DE3915188C1 - Wireless interrogation and current supply method for switches - using capacitative and inductive elements corresp. to sec. winding of transformer - Google Patents

Abstract

The method monitors switches in an isolated circuit mounted on a turning component of the car, e.g. steering wheel or column. The circuit is fed by a phase transformer with a.c. through its windings which are connected, on the one hand to the car and, on the other hand, to the turning component. The primary winding receives a driving voltage fromm the car's power source. In the isolated circuit there is a capacitative and an inductive element - and the latter, at least in part, can be supplied by the sec. winding- forming a resonant sub-circuit, with a resistance to limit the current. When at least one of the switches is activated, the resonance behaviour of the sub-circuit changes from the case when none is being activated and a comparison of the voltages and currents flowing can be used to monitor the switches. Other electronic unis are provided to analyse the results. ADVANTAGE - Requires only few components which need not themselves be precision types.

Description

The invention relates to a method for wireless interrogation and energizing a plurality of switches and a resistance in an on / in a rotatable component of a vehicle arranged insulated circuit the genus of claim 1, and a device for Execution of the procedure.

Such is known from European patent application 1 83 580 inductive arrangement for the transmission of commands, about from the steering wheel of a motor vehicle to the steering column or to the vehicle chassis, known. It will be there proposed that with the steering wheel rotatable relative to the Steering column connected secondary winding of a rotary transformer defined to strain in such a way that a Driver request coded secondary load of said rotary transformer results. The primary side is the application  with an almost constant alternating current provided so that the measurable on the primary winding AC voltage is a measure of that on the secondary side provided load is. This AC voltage will then peak rectified and quantized to different load conditions different Assign commands.

However, that arrangement does not provide a checking or monitoring query to the effect that the resistors ( 53 to 57 ) actually correspond to certain target values (within permissible tolerances) or are not changed inadmissibly by aging or are even defective. A faulty resistance to a wrong command can thus be evaluated in that arrangement. The rotary transformer must be manufactured with high precision and may only have small tolerances with regard to its air gap and its leakage inductance. The transformer cannot be tested. Because of the lack of intrinsic safety, that known device is e.g. B. less suitable for use in life-support personal protection systems.

A targeted supply of energy to a specific component, preferably in a certain resistance if no switch is closed (actuated) is not possible. That known arrangement is also generally suitable not about low-resistance, high-current resistors to supply.  

The post-published DE-OS 38 12 633 discloses a method and an apparatus for measurement a resistor in an isolated circuit, e.g. B. in a vehicle steering wheel. The procedure provides for one Resistance to part of a resonance circuit so that it largely determines its resonance quality, the resonance circuit on its inductive path Stimulate the resonance frequency in pulses and after switching off the number of decaying sources Count oscillation trains until their amplitude increases decayed a certain fraction of the initial decay value are. From the number of detected vibrations is concluded on the resistance.

A device described for this uses a rotary transformer, the secondary winding of a series connection said resistor with a capacitance and a separate one Resonance inductance is connected in parallel. The pulse-like lighting and switching off of the excitation signal causes interference spectra, the sensitive electronic Can influence on-board devices. A defect of the Resistance from an open circuit or the defect of another component connected in series be distinguished.

Since an excitation is provided at fixed frequencies is the effective total secondary inductance of the rotary transformer however due to manufacturing and assembly tolerances can fluctuate is an additional inductance  practically unavoidable in the secondary circuit. In case of additional transmission of a switching state to the The primary side is in addition to another capacity another inductance with from the field guidance of the Transformer and the aforementioned additional inductance independent field guidance required. Next is Query a variety of switches an appropriate Numerous additional L-C circuits in the isolated circuit required. The query of resonances at fixed Test frequencies further require that each additional Inductor made relatively accurate and above theirs must be secured against drift over the entire service life. Components, that code a switch position cannot be checked before the corresponding switch first is operated. Without actuation, a latent So the defect remains undetected.

In the German patent 38 12 628 a device for contactless power supply and query of an electrical Component or trigger means in a movable Part, especially in the steering wheel of a motor vehicle described. Query and power supply happen inductively using two rotary transformers. counter or the query of their positions are not provided. The facility uses two rotary transformers. The monitoring and operating current of the Trigger means in the form of a resistance happens at two different current levels. The facility operated yourself u. a. of a microcomputer for both generation  a driving alternating current as well as for evaluation purposes.

European patent application 1 53 072 describes one Multiplex device for solving the task, only a single continuous electrical connection and Interrogation line from a secure control room of a nuclear power plant from the position of a variety of switches in the Hazard or high temperature area of the nuclear power plant wired query, d. H. without isolation in mind a missing galvanic connection.

For this purpose, it is proposed that the electrical line as in Hazardous area of the system spatially installed LC network in the form of a waveguide with distributed inductance and capacity, d. H. with characteristic wave resistance execute this waveguide at switching locations lead past and there with appropriate switches Individual resonators of different resonance frequencies connect, and in the safe control room at the entrance of the waveguide thereby detectable change in impedance and determine classifiable changes accordingly Assign switching states. An isolation between the switching status detection and evaluation side is not aimed at according to the task and also did not fulfill any plausible purpose. Because of the transformation property the transmission line must be complex Impedance can be measured, for which both a voltage as well as current measurement, by amount and phase,  necessary is. The measurement of the supply voltage only or only the feed current at the entrance to the waveguide would give an ambiguous picture of what actually exists Switching state. The query and monitoring resistance is not provided.

The US-PS 39 67 161 describes a circuit in which has a low-resistance, designed as a fuse to protect against melting, in an electromagnetic field Resonance with high current can be applied. The WO 86/05302 discloses further developed structures of these Art, and in connection with it a resonance transformer with concentric primary and secondary conductor tracks, which with mutual overlap melting through against each other at every twist angle allow such resistance.

The object of the invention is, on the one hand, a method for wireless Interrogation and energization of a plurality of switches and a resistor in an on / in a rotatable Component of a vehicle arranged insulated circuit to create the few individual elements in the latter assumes that only minimal demands on their Absolute accuracy and that makes it possible to constantly monitor said resistance.

This task is accomplished by a generic method solved with the characterizing features of claim 1. According to the teaching of, advantageous further training is given claims 2 to 30 related thereto.  

The process according to the invention has the advantage that - in the simplest case - in addition to the resistance and one Multi-switch element only two more functional Elements in the isolated circuit are needed, namely an inductive and a capacitive element. Matching work or an expensive one The selection of components is completely eliminated. Need it only voltage values to be measured, no power levels or even a complex impedance.

Another object of the invention is a device for To carry out the procedure, which is only one small number of small and compact building elements with only small Requirements for their absolute accuracy in the isolated Circuit includes, thus also at cramped installation conditions (e.g. also in a vehicle steering wheel) and it allows constant monitoring of the resistance.

This object is achieved in a generic device solved with the characterizing features of claim 31; advantageous further training are according to the teaching of given claims 32 to 64 referring back to claim 31.

Advantageously, the device needs to be isolated Circuit next to the resistor and to be queried In the simplest case, switches only the secondary winding an already necessary transformer and a capacitive one Element. This can be used as a network with taps in  Formed a single-body multilayer component be. Additional benefits will be added a single further inductance opened up. Latter can be an integral part of the invention of a one-piece secondary part of the rotary transformer with mutually rotatable primary and secondary parts be carried out. It is also advantageous the failure of one of said components or a line break or a short in the wireless the circuit to be queried can be determined without delay.

Furthermore, it should enable the configuration according to claim 51 as Part of such a device the stationary control circuit, by means of which the query of switches or one in Circuit existing resistance take place continuously can, with as few components as possible, higher and higher to perform all comparable reliability, so that also a high and calculable availability of the whole Device results.

According to the teaching of, advantageous further training is given related claims 52 to 58.

This device has the advantage only need relatively small inductors, which enables them to be produced inexpensively in large quantities are. The device also has the advantage  to distinguish faultless operating states from faulty ones and the distinction criteria as required to learn a program again at any time. Thereby function inaccuracies can also occur over very long periods of time exclude completely by drifting component values. Another advantage of the device is in being a very effective energization of the resistance on a learned, d. H. exact resonance frequency allowed.

Finally, the configurations according to claims 59 to 62 train such a device so that they allow switch positions wirelessly query from the steering wheel of a vehicle and / or Resistance in the steering wheel as part of an occupant restraint system monitor and with operational performance to supply.

Easy to check and high reliability the device is finally in training Doctrine of claims 63 and 64 achieved.

An embodiment with different modifications is shown in the drawing and in the following Description explained. It shows  

FIG. 1 shows the functional diagram of a device according to the invention;

FIG. 2a harmonic quasi-a first schematic schedule of pulses for generating a frequency-variable drive signal;

FIG. 2b shows a second schematic schedule of corresponding pulses;

Fig. 3 is a diagram illustrating a monotonous gradual change in frequency of the driving signal over time;

Fig. 4 is a diagram illustrating the programmed time optimal, portion-wise wobbling of the quasi-harmonic drive signal;

FIG. 5 shows a diagram to illustrate the time-optimally dismonotonic wobble of the quasi-harmonic drive signal for a repetition frequency of different frequencies of the interrogation of switch positions of different priority; FIG.

Fig. 6 is an illustration of the absorption due Meßspannungsfenster lying within certain frequency intervals;

Fig. 7 shows a first modified embodiment form of the isolated circuit;

Fig. 8 is a section of a second modified embodiment of the isolated circuit;

9 shows the simplified sectional view of a rotary transformer whose primary and secondary windings of an axle are rotated in opposite directions with respect to Fig.

10 shows the functional circuit diagram of a reduction of the exemplary embodiment only for interrogating switches;

FIG. 11a is a third modified embodiment of the isolated circuit;

Figure 11b is a table of the allocation of switching commands and efficient capacity.

Fig. 12 shows a fourth modified form of the isolated circuit.

Identify the same marks in different figures same or corresponding parts.

The understanding of the method according to the invention follows completely from the functional explanations of the exemplary embodiment according to FIG. 1 and its reduction according to FIG. 10 and derived detailed modifications in each case.

In addition to querying a plurality of switches, the exemplary embodiment according to FIG. 1 also monitors a resistor in the isolated circuit. Without being a limitation of the invention, an example is an application in a vehicle steering wheel in which several switches are queried and a resistor (for example, as an operating element of an airbag system) is continuously monitored or even supplied with a certain operating power should. Finally, a reduction possibility of the exemplary embodiment for exclusive switch polling is explained.

According to Fig. 1 10 A are in an isolated circuit comprises a plurality of switches 11 a, b 11. . .; 11 and - as part of an airbag system assumed as an example - a resistor 17 is provided. The isolated circuit can be queried or supplied with energy from a stationary control circuit 30 via a rotary transformer 20 with axially rotatable primary 21 and secondary windings 19 . The primary winding 21 of said transformer 20 is part of the stationary control circuit, the secondary winding 19 is part of the insulated circuit 10 A.

Corresponding taps 23 , 26 of an inductive element 6 are assigned to different switching commands. Depending on whether the source feeding the primary winding 21 is designed as a voltage or current source, the inductive element 6 can be designed differently; in the latter case it can consist of the secondary winding 19 of the transformer 20 alone. If an upstream low-pass filter ( 33 ; see below) limits the coupling impedance to a current source or if a supply from a voltage source is provided, the inductive element 6 preferably consists of two partial inductances, namely, according to the equivalent circuit, of a coupling inductance which provides a fixed coupling to the primary winding 21 of the transformer 20 , and a free inductance, which does not have such a coupling. In general, the inductive element 6 is thus composed of the secondary winding 19 with magnetic route 22 of the transformer 20 and a secondary inductance, for example realized by a further winding 24 with a corresponding magnetic route 25 , in which case the taps mentioned can then also be distributed over both windings .

The winding 24 can be implemented independently of the transformer 20 as a separate winding with its own field guiding means 25 (e.g. made of ferrite or carbonyl iron). Depending on the manufacturing technology of the transformer 20 - z. B. with the formation of the same in the sense of FIG. 9 - but it can also be realized together with the secondary winding 19 as part of a one-piece secondary component of the transformer 20 .

Said taps are via assigned switches 11 a , 11 b,. . . connectable via at least one bus bar 12 to the capacitive element 7, here for example, with the partial capacity 14, thus the latter which on said serving as a return current path resistor 17, the inductance of the secondary winding 19 or a tapped 23 portion thereof or to the inductance of the secondary winding 19 and a tapped 26 Part of the winding 24 can be connected in parallel. The total inductance of the circuit is - also via the current path of the resistor 17 - for example another capacitor 13 permanently connected in parallel (the concept of the invention also includes more complex capacitive structures and, if necessary, also two or three busbars for connecting taps 23 , 26 of the inductive element 6 in groups to different capacitive outputs or taps of a capacitive element 7 , see FIG. 12).

The isolated circuit 11 A is capable of resonance without actuating a switch at a frequency which results from known total inductance and the capacitance of the capacitor 13 according to known rules. If one of the switches is actuated, the total inductance is capacitively blind-loaded along the total inductance in accordance with the relevant tap 23 , 26 , so that at least one new main resonance results at a lower frequency. In any case, the resistor 17 to be supplied with operating power and otherwise continuously monitored is in the main resonance current path.

The resistor 17 , for example in the form of an ignition resistor of a squib for triggering an occupant protection device in a vehicle, is preferably connected to the inductive / capacitive circuit as described above via two special connecting terminals 16 a and 18 a of the protection device 15 .

Via separate terminals 16 b and 18 b , the resistor can be connected in parallel with a control device 27 , which in the simplest case z. B. may include a series connection of a light emitting diode 28 and a counter-connected Zener diode 29 .

The inductive element 6 can consist of two windings 19 and 24 provided with differently designed or completely separate field guiding means 22 and 25 , so that in addition to the inductance of the winding 19 of the transformer 20 , a certain secondary inductance is effective in the isolated circuit 10 A , on which no direct transformer penetration takes place from the primary side.

For safety reasons, can be constructive provided that the switches are simultaneously actuated for delivery of a specific signal command, for example, for triggering a signal horn, two, for example, the switch 11 b and 11 e, that is, corresponding switching places in a steering wheel as the reaction conditions of a horn button e.g. B. can be executed multiple times, are each carried out in duplicate in a corresponding manner.

The two capacitors 13 and 14 are advantageous as a one-piece component, for. B. executed as a capacitive voltage divider in the form of a ceramic multilayer network with center tap 71 and branch connections 72 and 73 . Described in embodiments of the inductive element 6 as described with reference to FIG. 9, and constructive union of the switch 11 a,. . ., 11 g, for example on an integral multi-switch circuit board 11 that can be inserted into cavities of a steering wheel, the isolated circuit 10 A , 10 B ,. . . except a resistor 17 z. B. a protective device 15 and its control device 27 thus comprise only three one-piece components, which results in advantages in assembly and easy testing and servicing in the event of service.

The structure of the stationary drive circuit 30 is described below.

The primary winding 21, which is preferably connected to ground 9 on one side, has its other end routed to the output 34 of a low-pass filter 33 , which is fed on the input side by the output 32 of a drive circuit 31 . The low-pass filter 33 has an upper cut-off frequency and can contain a simple decoupling amplifier on the output side. For this purpose, the low-pass filter 33 and the drive circuit 31 can be connected to an operating voltage rail (+ U _B ); both are also connected to ground 9 .

Furthermore, an A / D microcontroller 36 is provided, which is also connected to ground 9 and is also connected to a resonance component 49 that determines its clock frequency. The microcontroller 36 has, as usual, a CPU, RAM and ROM areas, and furthermore an electrically erasable and writable, non-volatile memory 39 (E²PROM). Furthermore, it has an A / D input port 40 which communicates internally with an A / D converter, a digital control port 41 , a digital signal output port 37 and a display port 38 , both of which can also be combined with the digital control port 41 . If the device z. B. interact in a vehicle with a CAN / VAN bus 48 , a special bus port 47 can also be provided, via which data can then be exchanged between the device and a vehicle periphery according to the bus protocol.

Various lines are led from the digital control port 41 to the periphery, for example the line 42 to a signaling means, for example a signal horn, the line 43 to a warning system, and lines 44 to other devices. The line 46 A can be a learning command line, via which the microcontroller 36 can be induced to learn a specific operating situation in the form of data fields in the E²PROM 39 . Such a line can also be a component 48 a of the CAN / VAN bus 48, as indicated. In line 46 B , it can be, for. B. is an alarm line, such as from an on-board anti-theft system; Via line 46 B z. B. at least one external signal means can be triggered via one of the lines 42 and 43 . The line 45 comes from a hazard detector, such as a crash sensor, and then carries a signal when the consumer 17 is to be started up.

A status bus 50 , consisting of several lines, leads from the display port 38 to a display 51 which can display various operating states depending on the stored program, preferably in the field of vision of the driver of the vehicle. For this purpose, the display 51 can also be accommodated separately from the µcontroller 36 . Corresponding lines can, however, also be routed to a central diagnostic computer of a vehicle, which operates its own display means.

At least one input of the A / D port 40 is preceded by a signal detection circuit in the form of a detector 53 a , which in turn is connected via an input line 52 to the non-ground end of the primary winding 21 , which also functions as a read winding. The detector 53 a is connected to ground 9 and can be constructed as a passive film circuit, for example with the indicated structure of a semiconductor diode 54 a , a network of several resistors 55 a , and at least one smoothing capacitor 56 a and 57 a on the input and / or output of the resistance network. The detector 53 a can also be implemented as an active AM demodulator. Integrated detectors, such as e.g. B. the video demodulator chip MC 1330 from MOTOROLA. The detector 53 a supplies a unipolar directional voltage corresponding to the enveloping voltage at the primary winding to the A / D port 40 . The circuitry exemplified has a high bandwidth and, to that extent, desirably a very fast response.

A second such detector 53 b can optionally be provided, which, for. B. is able to generate a directional voltage with opposite sign. Its input is connected in parallel to that of the detector 53 a ; its output is routed via a separate line 58 b to a second input of the A / D input port 40 .

The digital signal output port 37 of the μcontroller 36 can control the drive circuit 31 via a plurality of lines 35 - here four by way of example. Optionally, the drive circuit 31 or - if present, the low-pass filter 33 , if it contains a decoupling amplifier - can also have an output from which a signal U _L corresponding to the current or voltage carried on line 32 or 34 can be obtained as a level reference; Such an output can possibly also be connected to an additional input of the A / D port 40 via an additional line 67 or 67 a .

The stationary drive circuit thus essentially comprises four components ( 31 , 36 , 49 , 53 a) with approximately the same, high reliability. Since there are trends in µcontrollers towards highly specialized circuits - including µSequences for directly binary-coded harmonic output signals - which ideally fulfill the tasks at hand, the term "µController" does not constitute a limitation in the context of this invention, but only specifies that a programmable one Digital circuit with non-volatile memory and the ability to process measurement data depending on program states (namely counter readings according to instantaneous frequencies) when a frequency generator controlling the drive circuit 31 is used for the harmonic operation of the isolated circuit.

The function of the device according to the method is described below with reference to FIGS. 2 to 6 in conjunction with FIG. 1.

When there is resonance, an increased current flows in the circuit - and thus also in the resistor 17 . In this resistor, a considerable part of the AC power transferred into the isolated circuit is converted into heat (power loss = RI²). The energy lost in this way comes from the drive circuit 31 , but, as assumed here, can only deliver a limited current (assumed current source characteristic). In this respect, when a limited current is fed into the primary winding 21 in the resonance state, there is an absorption-related voltage dip at the latter, which can be detected.

When switches 11 a are not actuated,. . ., 11 g here is the highest possible resonance frequency. An alternating current coupled in at this frequency can also supply operating power to resistor 17 particularly effectively. An increased primary current level is preferably provided for energizing the resistor 17 , that is to say significantly higher than for merely checking the resistor 17 in connection with the cyclical switch interrogation, so that the resistor 17 consequently heats up to a certain desired level only when energized.

Is it resistance 17 z. B. the resistance of a squib 15 of a restraint system in the steering wheel of a vehicle, the current supply of the resistor 17 must not be prevented even if the driver - for example out of shock - holds the horn button pressed in a collision. Other switch contacts can be designed as inoperable in such an exceptional situation by appropriately ergonomic design of the control panel of a steering wheel.

15 and then to ensure the ignitability of squib when the horn is actuated to target ignition timing, may, specifically two switches are utilized, as already mentioned above for a horn function is a constrained by design measures simultaneous operation, such as the switch 11 b and 11 e .

By simultaneously actuating these switches, the secondary winding 19 is not immediately short-circuited, but a part of the winding 24 of the secondary inductance, possibly also the latter together with a smaller part of the primary winding; the remaining, not short-circuited part of the secondary inductance is reduced to the non-short-circuited part of the winding 24 at least by counter-induction of the short-circuited part of the winding 24 .

This defines the total inductance of the isolated circuit. At the same time, however, a major part of this reduced inductance of the capacitor 14 is additionally connected in parallel. By tuning the capacitance of the capacitors 13 and 14 of the two partial inductances and the position of the horn switches 11 b and 11 e interconnectable taps 26 can be achieved that the resonance frequency at operated horn button (ie when actuated switches 11 b and 11 e) is either identical to the resting resonance frequency, or is only at a certain safety distance from it.

Since here the value of the resistor 17 (over a short time) as the effective resistance of the circuit is constant (unchangeable), there are two significantly different resonance qualities due to different reactance circuits. With the supply current left constant, they lead to significantly different voltages on the primary winding 21 , ie to different values of the directional voltage U _M. From a comparison of the regular open-circuit voltage value U _M for the resonance question of the isolated circuit without switch actuation (check of resistor 17 ) and that other value of U _M with simultaneous actuation of said horn switch with a previously learned reference value stored in the E²PROM for a long time without switch actuation (and, if increased Safety requirements, with a corresponding no-load voltage value stored volatilely as a contact release operation at the same frequency immediately after the last operation of the same switch), an actual operation of the horn switch can be easily discriminated.

In the event of an interruption in the resistance of the resistor 17 , the control device 27 responds at least at an interrogation frequency, in that a sufficiently high AC voltage is then available at its terminals for operating the light-emitting diode 28 . Your own rectifier effect in connection with the upstream Zener diode 29 perform the function of level discrimination; A sufficient diode current can only flow if a certain minimum voltage is exceeded at the terminals of the protective device - which is not possible without a defect in resistor 17 or the current paths supplying it. When the resistor 17 is intact, this device therefore has no effect on the function of the isolated circuit.

The drive circuit 31 of the control circuit 30 comprises, for example, one, preferably a plurality of digitally switched on and off current sources which can deliver a defined current to a common summation line, namely the output line 32 . Corresponding current sources are available in array form as fully integrated circuits with very high reliability; they also allow the current strength to be programmed within certain limits. Overall, the drive circuit used here acts as a signal converter for generating a quasi-harmonic AC signal from (several) logic signals.

Depending on the microcontroller used, a pulse-width-modulated signal which already directly reproduces a harmonic oscillation or various pulses can be transmitted on the signal path 35 , from which an at least quasi-harmonic signal can be assembled by addition or binary weighting.

For this purpose, FIG. 2a exemplifies how a quasi-harmonic signal, in particular the drive variable DS on the line 32 , is generated from three individual logic signals U _A , U _B and U _C output by the μcontroller. At inputs A and B of the drive circuit 31 there are temporally nested pulses 60 and 61 which, when added and signed, according to a semi-periodically changing sign signal U _C at input C - corresponding to pulse 62 - result in a step signal 63 approximating sinusoidal form 59 . A logic signal for increasing the drive current or the drive voltage can be transmitted to a further input D as soon as operating power is to be supplied to the resistor 17 .

Fig. 2b illustrates another method of obtaining a quasi-harmonic current signal DS from two compared to a basic signal 62 ( I _c ; LEAD) by relative phases ϕ ₁ and ϕ ₂ offset pulses 60 and 61 ( I _A / LAG₁, I _B / LAG₂) ; it allows higher output frequencies.

The additive assembly of such a signal proves to be expedient in order to achieve a sufficiently high drive frequency with very inexpensive µcontrollers. When using a simple µController of the type 80C96 from Intel (without E²PROM) or the type MC68HC05 from MOTOROLA (with E²PROM), the upper frequency limit for the drive signal can be reached up to 100 kHz. When using fast signal or video A / D processors, an operating frequency band between 255 kHz and 510 kHz can be used - with binary binary-coded output of a largely harmonic drive signal - so that direct interference from the fundamental wave in both the long-wave and medium-wave range of radio devices omitted. As is known, a harmonic signal that is only to be amplified then already provides a simple resistance network as a D / A converter in the drive circuit 31 . A squib can thus be triggered, for example, at a frequency of 500 kHz.

The low-pass filter 33 dampens harmonics in the drive signal according to FIG. 2 above the highest operating frequency. For this reason, and because there is no sudden surge of resonance in the isolated circuit, the connecting line 34 between the transformer 20 and a device part 30, for example, housed remotely, can have a certain length without causing interference to the reception in a nearby radio receiver . A combination of the quasi-harmonic drive signal DS from only two pulses 60 and 61 and a pulse 62 controlling the sign feeding current or voltage sources has proven to be sufficient to achieve sufficient harmonic suppression in the drive signal with a very simple low-pass filter 33 . Depending on the width of the occupied operating frequency range and the design of the low-pass filter, the signal U _B can also be omitted entirely, as a result of which an even simpler drive signal DS is obtained at the input of the low-pass filter, which may only consist of pulses 63 a appearing in a gap, their signs alternating, as indicated in Fig. 2a.

In the specified frequency range, inexpensive mass production technologies can be used both for the transformer 20 and the secondary inductance 24 , 25 and their taps, since only relatively small numbers of turns occur. The magnetic route 22 of a corresponding rotary transformer can be efficiently manufactured with high precision as a powder compact for corresponding working frequencies.

According to FIG. 3, the frequency of the drive signal is digitally wobbled in clock frequency increments by clock-controlled repetitive incrementing or decrementing of the pulse lengths in signals U _A , U _B , U _C both in relation to the fixed clock frequency of the μcontroller and to one another, ie above the Time repetitively changed from a lower frequency f _L to a higher frequency f _u (sweeping). Accordingly, a current is impressed into the insulated circuit, the frequency of which - if only for a short time - successively comes to lie at least in the vicinity of all possible resonance frequencies of the insulated circuit, ie without and with switch actuation. The wobble can be continuous according to (I) or discontinuous according to (II).

According to FIG. 6, when the resonance point is reached, the voltage on the primary winding 21 drops as already mentioned; the detector 53 a transmits a correspondingly characteristic drop in the rectified envelope voltage U _M via the A / D port 40 to the μcontroller 36 . By program-linked assignment of the instantaneous fundamental frequency output at the digital signal output port 37 and the size of the instantaneous reference voltage U _M related to a stored comparison value, the µcontroller determines the instantaneous state of the isolated circuit, ie without or with an instantaneously effective switching command. Without operating a switch 11 a ,. . ., 11 g , the resonance behavior is basically recorded on the basis of the property of the reaction components and the value of the resistor 17 . It can be seen that if this resistance is defective, all other resonances are also affected, ie a corresponding error in the protective device 15 can be determined in the course of switch queries.

Fig. 6 symbolizes a simultaneous superimposition of all possible resonances, as occurs only with monotonically spanning sweep with very fine frequency steps and successive actuation of various switches 11 a ,. . ., 11 g appear. The exemplary course of the directional voltage U _{M is} plotted against the frequency f . A corresponding (slow) monotonous area-spanning wobble is provided, on the one hand, for testing purposes and, on the other hand, as a learning operating state of the device, in the course of which, in a prescribed sequence of switch operations, the resonances which arise are stored in the E²PROM 39 in the form of data sets which characterize them, after which to be available as a look-up table for the detection of operational resonances and their assignment to switching commands.

For this purpose, the µController recognizes the extreme value of the reference voltage U _M at or in the vicinity of a resonance in the learning state and stores both the same and the value of the instantaneous frequency F _a , F _b , F _c , etc. as that of the relevant switching operation or Value of the resistance 17 characterizing data set. These learning values will later serve as reference values. On the other hand, the µController uses a ROM-resident program to generate value windows W _a , W _b , W _c , etc. from these learning values, within which it subsequently expects corresponding operating values due to permissible switching states in the isolated circuit or tolerates them as error-free. The frequency base values of the windows W _a , W _b , W _c , etc. in the scan program of the µController determine the non-volatile settable or loadable counter readings of a software counter within the µController for changing the drive frequency, within which the software counter is clocked in or out to cover the expected frequency ranges is decremented so as to effect the frequency change. The basic voltage values of the windows W _a , W _b , W _c , etc. accordingly determine non-volatile reference voltage words with which the bit patterns of all measuring words of the currently digitized measuring voltage U _M are compared by means of software-implemented exclusion comparators.

According to Fig. 6, ie, for example for actuating the switch 11 a, an expected frequency interval δ f _a, to that of the switch 11 b, a corresponding interval δ f _b, generated, etc., and each of these intervals a rectified voltage escape interval δ U _Ma, δ U _Mb, etc. assigned; the basic values are stored in the E²PROM 39 as non-volatile field description parameters. Since the resonances take place at different resonance qualities, the resonance peaks of the reference voltage U _M appear at different values over the frequency and are also of different widths; adjusted, the stored expectation windows of corresponding values can in practice also be unequally high or wide. In connection with this, the sensitivity of the A / D port 40 of the µcontroller 36 can be switched or adapted in a program-controlled manner for the approximately equally accurate detection of greatly different directional voltages U _M at different resonance frequencies. If the reading in of a reference signal characterizing the drive level is provided via a line 67 or 67 a , the sensitivity of the A / D port can also be set by an initialization program so that this signal has a fixed unit value after digitization. The level of the feed variable DS is then always automatically adjusted to the basic voltage values stored as learned (level normalization loop).

The learning mode of the µcontroller is called up, for example, in the manufacturing plant of a vehicle, or during a later service measure in the workshop in the course of a normal function check; To do this, line 46 A must be set to the learning signal level and switches 11 a to 11 g must be operated as normal (teachin). It can be seen that by learning its operating parameters, the device tolerates both certain absolute variations and long-term changes (e.g. due to aging) of the characteristic values of components in the isolated circuit, which results in cost advantages. After the steering wheel has been removed and reinstalled, assembly tolerances of the rotary transformer 20 can be "learned" for the purpose of a repair, for example.

According to FIG. 4, the entire frequency range containing operational resonances is preferably not continuously swept through (normal sweeping), but only expected frequency ranges to be queried in accordance with window barriers or reference frequencies that have been stored once are swept over (spot sweeping or scanning), so that no additional query dead times by sweeping over partial frequency ranges in which normally no resonances are to be expected. During the query time intervals δ t _a , δ t _b etc., only the corresponding frequency ramps S _a = F _a - ½ δ f _a to F _a + ½ δ f _a , S _b = F _b - ½ δ f _b to F are preferred _b + ½ δ f _b etc. swept over. In this respect, one query period follows the next without gaps.

In these targeted target frequency range queries (spot scans), which serve to shorten the response time, however, after a certain number of scan cycles specified in the program specification according to FIG. 4, a continuous range-spanning wobble can be switched on regularly, so that e.g. B. happens every 8th or 16th cycle according to FIG. 3 (ie over the entire operating frequency range). (Inadmissible) resonances outside the tabulated frequency window can also be detected in this way and evaluated for a corresponding error message and a specific entry in an error memory segment of the E²PROM 39 , from where an associated error code z. B. can be read out via bus 48 for service purposes.

The direct assembly of the feed variable DS from digital signals has the advantage over a PLL-guided harmonic oscillator that there are practically negligible settling times of the generator even with large frequency jumps. For this reason, corresponding spot queries of different resonances can be nested in any way, regardless of their position. B. shown in Fig. 5. This is very useful when e.g. B. for a specific query either during a certain, periodically repeating time interval (z. B. t ₂ to t ₇) or generally a certain query dead time must not be exceeded, ie the query in question must be done more often than other queries (e.g. S _b ₁, S _b ₂, S _b ₃). As indicated by S _d ₁ and S _d ₂, the frequency ramps S can be either increasing or decreasing by program, provided that they are only dimensioned sufficiently long in relation to the settling time of the isolated circuit 10 A.

The cycle between START and STOP illustrated by way of example is thus run through in an endless sequence by the scan program of the µcontroller 36 , unless sweeping cycles spanning the area are regularly interspersed for test purposes, as mentioned. The successive frequency ramps S _b ₁, S _b ₂, S _b ₃, etc. in shorter time intervals can also be cyclically jumped from a continuous span sweeping period according to FIG. 3 whenever a maximum permissible dead time (corresponding to a certain number of clock cycles) for the here for example, the switch 11 is passed b associated switching command recognition. In addition, in the case of widely differing resonance qualities, a frequency change of different speeds can be provided in different frequency ranges.

If the µController is programmed accordingly, the normal scanning cycle can also be changed by calling it up via bus 48 , e.g. B. from a central monitoring computer or a workshop-side service facility. For example, a special measuring cycle can be specified in this way, and a deviation quantity (detuning quantity) can then be read off the display 51 in the vehicle. This function is very useful when e.g. B. the steering wheel of a vehicle is to be removed and reinstalled in the workshop; The installer only needs to observe the display 51 in order to achieve the necessary accuracy of the steering wheel to remount (together with the secondary part of the rotary transformer 20 ) and to actuate certain switches for the test.

The insulated circuit 10 A can of course also be supplied for querying the switch bank 11 and for monitoring the protective device 15 by means of a constant alternating voltage on the primary winding 21, which can be provided analogously by a corresponding alternating voltage source as the drive circuit 31 . Instead of the primary voltage, the alternating current fed into the primary winding 21 is then detected by the detector 53 a (or 53 b ). At resonance, the current increases due to increased power absorption in the resistor 17 , in contrast to the drop in the primary voltage during constant current operation. To energize the resistor 17 , the output voltage of a corresponding voltage source can be increased. Such a modification allows certain savings by realizing a voltage source in the drive circuit 31 , but requires a current / voltage converter 66 at the input 52 of the detector (s) 53 a / 53 a and 53 b , in the simplest case realizable by a resistor. Such a modification is in any case fully encompassed by the inventive concept.

Fig. ₇ and 8 illustrate advantageous modifications of the isolated circuit 10 A , which can be used optionally with primary-side current or voltage supply and the latter offer certain advantages depending on the application.

The isolated circuit 10 B according to FIG. 7 differs from each according to FIG. 1 mainly in that, for example, the two capacitors 13 and 14 are connected in series as a capacitive voltage divider, even when the switches are not actuated, the inductive element 6 is connected in parallel via the resistor 17 and thus always contribute both to the quiet resonance for the request of resistor 17 and to its energization; In contrast to the embodiment according to FIG. 1, the capacitor 14 (and in this respect the entire capacitive element 7 and thus the entirety of all reactance components) can also be checked here without actuating the switch. The center tap 71 between the two capacitors 13 and 14 is located here on the already mentioned (one) busbar 12 (a group connection of the taps of the inductive element 6 in connection with several taps of a capacitive element comprising more than two individual capacitances - from several busbars - is of course included in the idea of the invention).

Here, too, the inductive element 6 is preferably formed from two windings 19 and 24 provided with different field guiding means 22 and 25 , so that in addition to the main inductance of the winding 19 of the transformer 20 , a certain secondary inductance is effective in the isolated circuit 10 B. The winding 24 can be implemented independently of the transformer 20 as a separate winding with its own field guiding means 25 (e.g. ferrite or carbonyl iron core). Example, in forming such as shown in Fig 9 - also be realized together with the secondary winding 19 as part of a secondary component of the transformer 20 produced in one piece.. Double actuation of the switch for partial short-circuiting of the total inductance to bring about a resonance frequency identical or close to the rest resonance frequency - with differing resonance quality - is possible in the same way with suitable matching of the characteristic values of the components to one another.

When isolated circuit 10 C of FIG. 8, the secondary winding of a transformer 20 'is divided into two parts 19 A and 19 B, which have a fixed coupling with the primary winding 21 and preferably also have taps. A further inductance with taps is interposed between the two winding parts, which either has a considerably weaker or no field coupling to the primary winding. It can be implemented as a separate winding 24 with its own field guide means 25 independently of the transformer 20 ' , but it can also be just as good - for example when it is designed according to FIG. 9 - together with the secondary windings 19 A and 19 B as a one-piece inductive element in the form of a be realized relative to the primary component movable, one-piece secondary component of the transformer 20 ' .

Depending on the design, this embodiment of the isolated circuit 10 C enables a particularly wide usable frequency range within which a larger number of switches 11 a , 11 b , etc. can be queried than in the previous embodiments, without increasing the dynamic demands for measuring the Resonance extreme of the drive size fed into the primary winding. With suitable coordination of the partial inductances with one another, more than two switches can in principle be actuated here, provided that corresponding switch pairs do not immediately short-circuit parts of the secondary windings 19 A and 19 B.

Fig. 9 shows a partial cross section through a rotary transformer, which is formed rotationally symmetrical with respect to an axis 8 and its primary and secondary windings are rotated against one another in each case together with associated magnetic Leitwegteilen respect to the axis 8. Such a rotary transformer can, for. B. find use on the steering wheel of a vehicle; 8 then corresponds to the steering wheel axis.

The magnetic routes are distributed here to primary and secondary parts, which have a channel-like shape and encircle the axis 8 in a ring-shaped manner and are arranged such that they can interlock with one another with small radial air gaps between coupling surfaces; the magnetic path 25 of the secondary inductance 24 is preferably continuous or integral with the secondary part 22 s of the path 22 of the transformer 20 , 20 ' . In the primary "groove" 22 p of the magnetic path 22 of the transformer 20 , 20 ' is the annular primary winding 21st In the secondary, by way of example here external "channel" 22 s of the magnetic route 22 of the transformer 20, 20 'is / the annular / are n secondary winding / s 19/19 A and 19 B. The two magnetic conductive channel bodies appear so nested that only two relatively short, but in any case considerably larger air gaps 22 ' separate them. The ring-shaped winding 24 of the secondary inductance lies in the magnetic guide 25 designed as an open “groove”; it has a comparatively very long air gap 25 ' as a magnetic yoke and is provided to keep the unwanted field coupling of the winding 24 to the windings 19 and 19 A , 19 B and 21 low on the one hand and on the other hand an open radiation of magnetic fields by the Avoid winding 24 . The shear of the magnetic guide 25 with the long air gap 25 ' leads to a good reproducibility of the secondary inductance in the mass production of such a structure.

The magnetic routing body can be used for low Operating frequencies from individual angular, for Ring formability if necessary feathered or corrugated sheet metal elements be stacked together; by such dissolution into individual sheet metal layers low eddy current losses and correspondingly high ones Resonance grades achieved. The sheets must not be used  Realize circumferential short-circuit along the windings. To do this, it proves advantageous to use them superficially to isolate and layer on circumferential gap.

For higher operating frequencies, the production of one-piece primary and secondary magnetic guide bodies made of electrically non-conductive material that can be magnetized with low losses, for example made of ferrite or a ferrite or carbonyl iron powder material that can be molded in a resin bond, is more suitable. Sinterable ferrite materials are also possible. At higher frequencies, it proves to be very advantageous to provide the outer surfaces of the electrically non-conductive channel elements, which are not involved in the formation of the air gap, in the manner of circular circumferential short-circuit windings or sheaths with highly conductive metal coatings 64 , 65 ; As magnetic blocking surfaces, they support the desired field guidance and help reduce unwanted electromagnetic radiation. With sufficient magnetic conductivity and low loss of the core material of the magnetic paths, the resonance quality is not measurably influenced by such metallization.

The resistor 17 can be continuously monitored not only for complete failure (interruption or short circuit), but also for changes in its value. Since it lies in the main current path, its resistance value is included in all resonance qualities, provided that this resistance value is not significantly lower than the winding resistance of the inductors. A comparison of expected windows δ U _M for the reference voltage U _M, originally learned with proper resistor 17 and stored in the look-up table of E²PROM 39, and a characteristic failure of such a window without and / or with actuation of a specific switch, can result in a resistance-related change in the resonance quality by means of a simple one algebraic calculation routine can be determined.

On the other hand, the value of the total resistance of the circuit, and thus indirectly also the value of the resistor 17 , can easily be determined in the course of normal operation from a direct control of the resonance quality; such can occasionally be interspersed in the normal scan program. For this purpose, in the case of unactuated switches (recognizable by a resonance frequency which had not been changed for a long time and which corresponds sufficiently with the corresponding reference value from the non-volatile memory 39 ), the current resonance frequency ( U _m maximum) is precisely recorded and then the existence or nonexistence of a given frequency offset requested value of the rectified voltage U _M in the calculated values of the learning values window, which has the voltage U _M will be allowable resistance values (Two windows measurement). The results of several such measurements can be statistically standardized and written as a trend factor in a record segment of the non-volatile memory 39 , from where this z. B. can be queried in the vehicle maintenance check or shown on the display 51 .

Alternatively, the implementation may signal a command output by two at the same time forcibly closing switch (z example 11 b and 11 e) are utilized to monitor the value of the resistor 17 as described. This value is namely - at the same resonance frequency - differently in effective resonance resistors with and without switch actuation, so that by means of a simple arithmetic routine from a drift of the difference of measured resonance direct voltage values from a difference of corresponding direct voltage values stored with originally intact resistor 17 (with closed and not closed signal switches ) Inadmissible storage of the resistance value from the setpoint can be discriminated against.

In this regard, it is also mentioned that when using a second detector 53 b (indicated) positive and negative half-waves of the reaction signal tapped at the primary winding can be detected and evaluated separately. In the event of an interruption of the resistor 17 and the resulting response of the light-emitting diode 28 - either without or with actuation of a switch provided specifically for test purposes - the μcontroller can also arise from the asymmetry in the envelope voltage of the primary voltage or the primary current caused by the rectifying effect of the diode 28 a second way, independent of the resonance measurement method, ascertain the presence of acute non-functionality of the protective device 15 and display it on the display 51 or the bus 48 . A test step in the operating program only needs to check whether the limit of the amount from the sum of the two reference voltages has been exceeded.

Regardless of the instantaneous polling frequency, when a trigger signal arrives on line 45 by interrupt or soft reset of the scan program, the operating frequency required to energize resistor 17 is immediately output by the µcontroller and, if necessary, the drive circuit 31 on the input side (e.g. D ) supply line with a power-up level in order to immediately increase the drive current / drive voltage emitted by the drive circuit. A corresponding soft reset can also be called up via the bus 48 as the initialization state of the scan program of the μcontroller with optional priority, in order to check, for example, the operability of a squib.

Depending on the distribution of the transformer coupling inductance and the secondary inductance, the isolated circuits described may also have (weaker) secondary resonances in addition to the main resonances. To rule out ambiguities, the learning program of the µcontroller can implement a maximum hold function with the effect that, in the learning state, only the smallest or largest detectable value of the reference voltage U _{M can be} saved from a buffer into the E²PROM 39 during sweeping across a range and can then be called as a reference value.

In Fig. 10, the embodiment is based on a minimal configuration for the sole query of switches 11 a ,. . ., 11 d reduced in the isolated circuit 10 D , which here has the simplest structure of a parallel resonance circuit. Depending on whether a current source 70 or voltage source 71 is realized in the drive circuit 31 a on the output side, the inductance of the parallel resonance circuit can only consist of that of the secondary winding 19 of the transformer 20 or additionally a free secondary inductance, e.g. B. realized by a series winding 24 include. A basic capacitance of a capacitor 13 connected in parallel with the inductive element 6 can be switched 11 a . . ., 11 d optionally additional coding capacities 14 a ,. . ., 14 d connected in parallel and thus the resonance frequency of the isolated circuit can be changed in a defined manner.

Because the absence of taps of the resistive inductive element 6, the loss resistance determining the resonance quality in the isolated circuit 10 D is approximately constant here (the capacitances have a negligible loss compared to the inductive element 6 , ie a higher quality), and because the monitoring of a resistance in the isolated circuit is omitted here, this embodiment results in a larger usable range of the directional voltage U _M , and thus a larger measurement-to-noise ratio. For this reason, the drive size DS has to meet lower requirements with regard to its maximum harmonic content. For this reason, the low-pass function described here can be realized solely by means of an RC element in the drive circuit 31 a and, as a result, the wobble or query speed can be higher than in the exemplary embodiment according to FIG. 1; The integration of such a low pass in the drive circuit 31 a is symbolized by the symbol 33 a . The second detector 53 b and the line 45 are omitted here. The function of this exemplary embodiment corresponds to that of the one already described according to FIG. 1.

FIG. 11a is a practical realization form of the isolated circuit 10 is D having a plurality of operable keys 82 of means of a Codiermechanik 83 switches 11 a to 11 c; said switches are e.g. B. constructively combined in a multi-switch element 84 . The capacitive element 7 comprises a common capacitor coating connected to the secondary winding 19 and a plurality of individual counter-coatings which, together with the former, realize a capacitor 13 and individual coding condensate 03073 00070 552 001000280000000200012000285910296200040 0002003915188 00004 02954oren 14 a , 14 b and 14 c ; the capacitors are preferably configured as a single-body as a multi-pole ( 71 , 72 , 73 a , 73 b , 73 c ) capacitive network. The corresponding coding capacitances are connected in parallel to the inductive element 6 - and optionally also to the basic capacitance of the capacitor 13 - in accordance with the table in FIG. 11b; this table corresponds to that of a binary counting sequence. With only three coding capacitors, seven different resonance states can be established and thus seven different switching commands can be transmitted. The capacitor 13 may also be missing; there is then no resonance (in the relevant measurement frequency range) without switch actuation, and in this respect a discriminant voltage or current extreme on the primary winding, not shown here. A rest resonance within the measuring frequency range by means of a capacitor 13 , on the other hand, permits the continuous checking of the isolated circuit 10 D even without a switch actuation, as explained in connection with FIG. 1. The optional ground connection 9 ' can be high-resistance and avoids, among other things, undesirable static charging of the isolated circuit 10 D.

Fig. 12 shows in a further developed embodiment an isolated circuit 10 E , in which not only taps of the capacitive element 7 , but also taps 23 , 26 of the inductive element 6 in accordance with a multi-switch element containing a plurality of switches (not shown), z . B. in the form of a switching matrix with keypad 85 , can be connected to each other. A partial short circuit of the inductive element can therefore also be provided here, whereby a particularly high number of command codes is possible with a low outlay on components. Of course - without this being repeated figuratively - the inductive element 6 can also be designed according to FIG. 8 (two-part secondary winding 19 A and 19 B with an intermediate inductor interposed).

In the course of the detailed functional description of the exemplary embodiment the device and its various Modifications are the basic characteristics of the invention Procedure in the context of the claim wording fully disclosed.

The scope of the invention is not left if e.g. B. other structures of resonant reactance circuits in the isolated circuit of a corresponding one Find device use.

Claims (64)

1. Method for wireless interrogation and energization of a plurality of switches and a resistor, which are arranged in an insulated circuit provided on / in a rotatable component of a vehicle, in the last instance by means of a rotary transformer connected on the one hand to the vehicle and on the other hand to the rotatable part Windings alternating current power can be fed in, in that the primary winding is impressed with an alternating drive variable (current or voltage), characterized in that

• - That in the isolated circuit ( 10 A , 10 B , 10 C , 10 D , 10 E) a capacitive ( 7 ) and an inductive element ( 6 ) are provided, the latter at least partially with the secondary winding ( 19 ; 19 A , 19 B ) of the transformer ( 20 ) is identical and forms a resonant circuit with the capacitive element ( 7 );
• - That said resistor ( 17 ) is provided in a circuit path leading to at least one resonance high current;
• - That the level of the drive size is kept substantially constant;
• - That the frequency of the drive variable is constantly changed over time between predetermined barriers;
• - That by reacting at least one switch, the reactance behavior of the circuit is changed so that its overall resonance behavior changes characteristically compared to that without switch actuation;
• - That a continuous reaction signal (voltage or current) is detected on the primary side in response to the frequency change of the drive change quantity and is subjected to an analysis;
• - That the analysis includes at least a comparison of instantaneous values of the reaction signal and associated instantaneous frequencies with corresponding target values;
• - That from the comparison result without actuated switch on the flawlessness of the isolated circuit and from a corresponding comparison result with at least one operated switch on one of the at least one switch assigned command and from at least one comparison result on flawlessness of said resistor ( 17 ).

2. The method according to claim 1, characterized, that the constant frequency change predominantly happens continuously and discontinuous changes  the frequency leaps and bounds into negligible Time happen. 3. The method according to claim 1, characterized, that the constant frequency change predominantly happens quasi-continuously in small steps and other changes in frequency happen by leaps and bounds. 4. The method according to claim 1, characterized, that the constant change in frequency throughout from a deepest or highest to one highest or lowest frequency at all. 5. The method according to claim 2 or 3 and 4, characterized, that when extreme frequencies are reached, the change the frequency - if necessary gradually - happens continuously. 6. The method according to claim 1, characterized, that the change in frequency in at least two happens in individual areas and at least one discontinuous Transition from one frequency range to another takes place.   7. The method according to claim 6, characterized, that the change in frequency in different Areas with different directions of change happens. 8. The method according to claim 6, characterized, that the change in frequency in different Areas happens at different speeds. 9. The method according to claim 6, characterized, that the change in frequency in at least one Area with changing direction of change happens. 10. The method according to claim 6, characterized, that the change in frequency in at least one Area happens in multiple succession before the frequency changes to another range. 11. The method according to claim 6, characterized, that the change in frequency in more than two individual sub-ranges happens, with individual frequency ranges run through different times.   12. The method according to claim 4 and 6, characterized in that

• - That the change in frequency occurs predominantly in at least two individual areas, and
• - That the frequency change occurs less frequently continuously from the lowest or highest to the highest or lowest frequency.

13. The method according to claim 12, characterized, that in the course of the less frequent, continuous Frequency change the same temporarily canceled and at least one of the individual sub-frequency ranges visited and painted over and afterwards the continuous Frequency change continues from the abort frequency becomes. 14. The method according to claim 1, characterized, that the zero crossings of the drive change quantity by pulses or pulses output by a computer be determined. 15. The method according to claim 14, characterized, that the drive change size before loading the Primary winding subjected to frequency band trimming becomes.   16. The method according to claim 1, characterized, that in a learning state both without switch operation as well as successively taking place Switch operations detectable extreme values of said reaction signal read as setpoints and saved will. 17. The method according to claim 16, characterized, that the storage is non-volatile. 18. The method according to claim 16, characterized in that setpoint windows ( W _a , W _b , W _c , _... ) Are determined on the basis of discrete setpoints, which are used as tolerance windows for the analysis of the reaction signal obtained on the primary side. 19. The method according to claim 18, characterized, that said determination by calculation according to Program instruction of a computer happens. 20. The method according to claim 19, characterized, that for calculation according to program instructions at least one parameter is currently specified.   21. The method according to claim 19, characterized, that the calculation according to at least one current parameters each time it is started up happens. 22. The method according to claim 1 and 18, characterized in that the resistance ( 17 ) is monitored by analyzing said reaction signal for fitting into two different setpoint windows. 23. The method according to claim 1, characterized in that at least for a certain time in the course of the analysis of the reaction signal, an auxiliary signal ( U _L ) is evaluated, which represents a measure of the level of the drive change quantity fed into the primary winding, and that other analysis results at least one value of this auxiliary signal can be obtained. 24. The method according to claim 1, characterized in that to supply the resistor ( 17 ) with operating power as required, the constant frequency change is interrupted and the drive variable is supplied at a fixed frequency. 25. The method according to claim 24, characterized in that the fixed frequency optionally corresponds

• a) a resonance frequency last recorded over a long time;
• b) a stored fixed frequency.

26. The method according to claim 16 and 24, characterized, that a frequency is used as the fixed frequency the extreme value of said response signal without being present a switch operation was saved. 27. The method according to claim 24, characterized, that after the constant change of the Frequency of the level of the fixed frequency drive variable is increased. 28. The method according to claim 1, characterized in that an inductive element ( 6 ) is used as part of the resonant circuit, which has taps ( 23 , 26 ), which via associated switches ( 11 a ,..., 11 g ) with the capacitive element ( 7 ) can be connected. 29. The method according to claim 24 and 28, characterized in that the resistor ( 17 ) is heated at the same fixed frequency even when actuating more than one switch. 30. The method according to any one of the preceding claims, characterized, that positive and negative half waves of the primary continuously detected reaction signal separately be evaluated. 31. Device for wireless interrogation and energization of a plurality of switches and a resistor, which are arranged in an insulated circuit provided on / in a rotatable component of a vehicle, in the last instance by means of a rotary transformer connected on the one hand to the vehicle and on the other hand to the rotatable part Windings alternating current power can be fed in, in that the primary winding is impressed with an alternating drive variable (current or voltage), characterized in that

• - That the isolated circuit ( 10 A , 10 B , 10 C , 10 D , 10 E) includes switches to be queried ( 11 a ,..., 11 g ; 11 ; 84 , 85 ) and said resistor ( 17 ):
• - At least one inductive element ( 6 ), the winding of which is at least partially designed as a secondary winding ( 19 ; 19 A , 19 B) with a fixed magnetic coupling to the primary winding ( 21 ) of the transformer ( 20 );
• - At least one capacitive element ( 13 , 14 ; 13 , 14 a , 14 b , 14 c , 14 d ; 7 ), which together with the inductive element ( 6 ) forms a resonant circuit;
• - The resistance ( 17 ) of the inductive element ( 6 ) is connected directly in series and at least one element ( 6 or 7 ) via said switches ( 11 a ,..., 11 g ; 11 ; 84 , 85 ) with taps ( 73 ; 71 ; 73 a , 73 b , 73 c , 73 d ; 23 , 24 ) of the other element ( 7 or 6 ) is connectable;
• - That there is a control circuit ( 30 ) which interrogates the isolated circuit and supplies it with current, which comprises:
• - An alternating current or voltage source ( 31 ) with a substantially constant level and with a variable frequency, operatively connected to said primary winding ( 21 );
• - At least one signal detection circuit ( 53 a ; possibly with an upstream signal converter 66 ) for obtaining a reference voltage ( U _M ) corresponding to the voltage or the current on / in the primary winding ( 21 );
• - A measuring, control and evaluation device which specifies the instantaneous frequency of the drive quantity ( DS) output by the AC or voltage source ( 31 , 33 ), measures the reference voltage ( U _M ) and, together with the predetermined instantaneous frequency, compares it with stored fixed values and according to the comparison, either emits at least one error signal or emits control signals in accordance with actuated switches.

32. Apparatus according to claim 31, characterized in that the inductive element ( 7 ) has taps ( 23 , 26 ). 33. Apparatus according to claim 31, characterized in that the inductive element ( 6 ) is realized solely by a secondary winding ( 19 ) with a magnetic guide ( 22 ; 22 p , 22 s ) of the transformer ( 20 ). 34. Apparatus according to claim 31, characterized in that the inductive element ( 6 ) consists of two separate-physical structures, namely the secondary winding ( 19 ; 19 A , 19 B) with a magnetic path ( 22 ; 22 p , 22 s ) the transformer ( 20 ) and a separate inductor with winding ( 24 ) and its own magnetic route ( 25 ). 35. Apparatus according to claim 31, characterized in that the inductive element ( 6 ) is designed as a one-body secondary structure with at least two-part winding, the secondary structure cooperating with a correspondingly opposing primary structure by a first part of the winding ( 19 ; 19 A , 19th B) the secondary structure with coupling to the primary winding ( 21 ) of the transformer ( 20 ) and a second part of the winding ( 24 ) of the secondary structure is formed with no or negligible coupling to the primary winding ( 21 ). 36. Apparatus according to claim 35, characterized in that in the one-body secondary structure, the first winding part ( 19 ; 19 A , 19 B) cooperates with a magnetic guide ( 22 s ), which finds a corresponding magnetic yoke ( 22 p ) on the primary side, and that the second winding part interacts with a magnetic guide ( 25 ) without primary-side inference. 37. Apparatus according to claim 31, characterized in that elements ( 22 p , 22 s ) of the magnetic guide ( 22 ) of the transformer ( 20 ) are layered from angularly annular sheet metal elements. 38. Apparatus according to claim 36, characterized in that the magnetic path ( 22 s ) of the secondary winding ( 19 ; 19 A , 19 B) and the magnetic path ( 25 ) of the further winding ( 24 ) are formed as a molded or sintered piece . 39. Apparatus according to claim 31, characterized in

• - That the transformer ( 20 ) is designed as a rotary transformer with essentially circular, a common axis ( 8 ) revolving primary ( 21 ) and secondary windings ( 19 ; 19 A , 19 B) and the same receiving magnetic guide bodies ( 22 p , 22 s ), and
• - That on the free outer surface of at least one of the magnetic routing body ( 22 p , 22 s ) an electrically well-conductive coating ( 64 , 65 ) is provided at least in the form of a short-circuit conductor path encircling the routing body with a certain width.

40. Apparatus according to claim 31, characterized in that the capacitive element ( 7 ) is designed as a network with at least three connections ( 71 , 72 , 73 ) which are not in ohmic connection with one another and at least two individual capacitors ( 13 , 14 ; 13 , 14 a , 14 b , 14 c , 14 d) and at least one capacitive tap ( 71 ; 71 , 73 a , 73 b , 73 c) . 41. Apparatus according to claim 40, characterized in that the capacitive element ( 7 ) is designed as a one-piece ceramic component. 42. Apparatus according to claim 40, characterized in that the values of individual capacities of the capacitive element ( 7 ) which can be tapped off are unequal. 43. Device according to claim 40, characterized in that

• - That the at least three connections ( 71 , 72 , 73 ) of the capacitive element ( 7 ) with other elements of the isolated circuit ( 10 A , 10 B , 10 C , 10 D , 10 E) can be connected as follows:
• - End lining connection ( 72 ) of a first capacitance ( 13 ) with the first end of the inductive element ( 6 );
• - Capacitive tap ( 71 ) with the second end of the inductive element ( 6 ),
• - The at least second end lining connection ( 73 ; 73 a , 73 b , 73 c , 73 d) an at least second capacitance ( 14 ; 14 a , 14 b , 14 c , 14 d) via individual switches ( 11 a ,..., 11 g) with the inductive element ( 6 ), etc

44. Device according to claim 40, characterized in that

• - That the at least three connections ( 71 , 72 , 73 ) of the capacitive element ( 7 ) with other elements of the isolated circuit ( 10 A , 10 B , 10 C , 10 D , 10 E) can be connected as follows:
• - End lining connection ( 72 ) of a first capacitance ( 13 ) with the first end of the inductive element ( 6 );
• - End lining connection of a second capacitance ( 14 ) with the second end of the inductive element ( 6 );
• - At least one capacitive tap ( 71 ) via individual switches ( 11 a ,..., 11 g) with the inductive element, etc

45. Apparatus according to claim 43 or 44, characterized in that the connection via individual switches ( 11 a ,..., 11 g) possible with the inductive element ( 6 ) by at least one tap ( 23 , 26 ) of the inductive element ( 6 ) happens. 46. Apparatus according to claim 45, characterized in that a partial short circuit of the inductive element ( 7 ) can be brought about by simultaneous actuation of at least two switches ( 11 a ,..., 11 g) . 47. Apparatus according to claim 40, characterized in that the inductive element ( 6 ), its taps ( 26 , 23 ) and the capacitance values of individual capacitors ( 13 , 14 ) of the capacitive element ( 7 ) are matched to one another in such a way that at the same time Closing at least two predetermined switches (from 11 a ,..., 11 f) results in at least approximately the same resonance frequency as in the case of unactuated switches. 48. Device according to claim 31, characterized in that the resistor ( 17 ) has a control device ( 27 ) connected in parallel. 49. Apparatus according to claim 48, characterized in that the control device ( 27 ) with the resistor ( 17 ) is connected via special connections ( 16 b , 18 b) , the latter not being identical to the connection points ( 16 a , 18 a) of the resistor ( 17 ) with the inductive and capacitive element ( 6 , 7 ). 50. Apparatus according to claim 49, characterized in that the control device ( 27 ) comprises at least one light-emitting semiconductor component ( 28 ). 51. Device according to claim 31, characterized in

• - That the measuring, control and evaluation device in the form of a programmable digital circuit with clock generator, memory and non-volatile memory, implemented as an example as a µcontroller ( 36 ) with E²PROM ( 39 ), A / D input port ( 40 ), digital control ( 41 ) and signal port ( 37 ) is formed;
• - that the alternating current or voltage source is formed (31) controllable with pulses driving circuit (31) for generating a frequenzverketteten at least quasi-harmonic, variable-frequency drive size (DS);
• - That the reference voltage ( U _M ) is measured after digitization by software.

52. Apparatus according to claim 51, characterized in that a low-pass function ( 33 , 33 a) is inserted in the signal path between the digital signal port ( 37 ) and the primary winding ( 21 ). 53. Apparatus according to claim 51, characterized in that the A / D port ( 40 ) is multi-channel and means are available to provide a level signal ( U _L ) corresponding to the drive variable ( DS) and a channel of the A / D Ports ( 40 ) to feed ( 67 , 67 a) . 54. Device according to claim 51, characterized in

• - That in accordance with a permanently stored program
• - The repetition frequency of the pulses from the µcontroller to the drive circuit ( 31 ) ( 37 , 35 ) can be changed continuously;
• - the instantaneous reference voltage ( U _M ) can be read into the µcontroller and, together with the instantaneously predetermined repetition frequency, is comparable with non-volatile ( 39 ) fixed values, and
• - On the basis of this comparison, either a warning or error signal or, in accordance with actuated switches ( 11 a ,..., 11 g), control signals can be emitted from the digital controller ( 41 ) by the µcontroller.

55. Apparatus according to claim 51, characterized in that after exposure to a learning signal ( 46 A) in accordance with a ROM-resident program from the µcontroller ( 36 ) instantaneous values of the measuring voltage ( U _M ), in particular maximum values, with associated instantaneous frequencies can be recorded and the same and / or tolerance fields calculated therefrom can be stored as reference and comparison values in the non-volatile memory ( 39 ). 56. Apparatus according to claim 51, characterized in that upon application of an operating signal ( 45 ) the constant frequency change can be canceled by the µcontroller ( 36 ) and on its digital signal port ( 37 ) a fixed frequency can be output, which according to a programmed selection one of the following largely corresponds to two frequencies:

• a) the resonance frequency last recorded over a long time;
• b) a non-volatile fixed frequency.

57. Apparatus according to claim 56, characterized in that a signal can be emitted from the µcontroller ( 36 ) to a switching or amplifying element at the same time, which causes the drive size ( DS) to be increased immediately. 58. Device according to claim 51, characterized in

• - That a second detector or sampling circuit ( 53 b) is provided for detecting and generating a reversely polarized directional voltage from said measurement signal;
• - That the control circuit ( 27 ) can be activated when the resistor ( 17 ) is interrupted and
• - That at least due to a non-balance of opposite directional voltages, a warning signal can be generated and can be removed at an output ( 38 , 41 , 47 ) of the µcontroller ( 36 ).

59. Apparatus according to claim 31, characterized in that the insulated circuit ( 10 A , 10 B , 10 C , 10 D , 10 E) of the device is provided for installation in the steering wheel of a motor vehicle. 60. Apparatus according to claim 31, characterized in that the resistor ( 17 ) is provided as part of the squib ( 15 ) of an occupant restraint system in the steering wheel of a motor vehicle. 61. Apparatus according to claim 51, characterized in that the control circuit ( 30 ) is equipped with a display device ( 51 ) which can be controlled by a special display output ( 38 ) of the µcontroller ( 36 ) in the field of vision of the vehicle driver. 62. Apparatus according to claim 51, characterized in that a resident auxiliary operating program can be called up, which changes the frequency in a cycle deviating from the normal polling cycle and thus allows a mechanic to measure a dismantled steering wheel again by measuring the display of the display device ( 51 ) without measuring aids to install. 63. Device according to claim 51, characterized in that the µcontroller has a special network port ( 47 ) through which the device can be loaded with operating parameters and the operating states of the same can be queried. 64. Apparatus according to claim 31, characterized in that the control circuit ( 30 ) comprises - apart from means at interfaces - essentially three integrated semiconductor circuit functions, namely a µcontroller with E²PROM ( 36 with 39 ), a driver circuit ( 31 ) and an AM demodulator ( 53 a) .