JP3329370B2 - Occupant detection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant detection system and, more particularly, to an improvement in an occupant detection system capable of simply detecting the occupant's seating state in a passenger seat of an automobile equipped with an airbag device.

[0002]

2. Description of the Related Art Generally, an airbag device is a device for reducing the impact received by an occupant at the time of an automobile collision.
It has become indispensable to the safety of automobiles, and is recently being installed not only in the driver's seat but also in the passenger seat.

As shown in FIG. 14, for example, this airbag apparatus has a self-service sensor SS1 and a squib SQ.
1, a squib circuit on the driver's seat side comprising a series circuit of semiconductor switching elements SW1 such as a field effect transistor, and a semiconductor switching element SW such as a safing sensor SS2, a squib SQ2 and a field effect transistor.
2, a squib circuit on the passenger seat side, an electronic acceleration sensor (collision detection sensor) GS, and an electronic acceleration sensor G
The control circuit CC has a function of determining the presence or absence of a collision based on the output signal of S and supplying a signal to the gates of the semiconductor switching elements SW1 and SW2.

According to this airbag device, when an automobile collides for some reason, the switching contacts of the safety sensors SS1 and SS2 are closed in response to a relatively small acceleration, and the safety sensors SS1 and SS2 are closed. The squib circuit on the passenger seat side becomes operable. When the control circuit CC determines that the vehicle has definitely collided based on the signal from the electronic acceleration sensor GS, a signal is supplied to the gates of the semiconductor switching elements SW1 and SW2, and the switching elements SW1 and SW2 are turned on. Becomes ON state. As a result, current flows through each squib circuit,
Due to the heat generated by the squibs SQ1 and SQ2, the airbags on the driver's seat side and the passenger's seat side are deployed, and the occupant is protected from the impact due to the collision.

By the way, according to this airbag device,
For example, as shown in FIG. 15 (a), when an adult P is seated on the seat 1, the above-described occupant protection effect can be expected at the time of collision. However, as shown in FIG. (B), the passenger seat sheet - Child and fixed on sheet 1 sheet - if bets 1A infant SP is sitting backward (R ear F acing I nfant S eat: less, (Referred to as RFIS), since the deployment of the airbag may adversely affect the infant SP, it is desirable that the airbag should not be deployed even if the vehicle collides. Also, FIG.
As shown in (1), when the infant SP is sitting forward on the child seat 1A fixed on the seat 1 in the passenger seat ( F
orward F acing C hild S eat: less, since the air bag by the deployment of the air bag there is a concern that covers the face of the child SP to called FFCS), RFI
As in the case of S, it is desirable that the airbag should not be deployed even if the vehicle collides.

Therefore, in order to cope with such a problem, an airbag device as shown in FIG. 16 has been proposed. In this airbag device, a sensor SD for detecting whether or not an occupant is seated in a passenger seat is installed, and a control circuit CC determines a seating state of the occupant in the passenger seat based on a detection signal of the sensor SD. When an automobile collides, the airbag is set to one of a deployable state and an undeployable state. In particular, as the sensor SD, a sensor using a weight sensor for measuring the weight and a sensor using a camera to photograph an occupant sitting on a sheet and judging whether it is an adult P or a child SP by image processing are proposed. Have been.

According to the former method, it is possible to roughly determine whether the occupant is an adult P or a child SP, and based on the result, the airbag is deployed in one of a state in which it can be deployed and a state in which it cannot be deployed. Although it can be set to avoid an unexpected situation in the event of a car collision, the weight varies greatly between individuals, and even if a child is heavier than an adult, it is not only inaccurate but also RFIS, FFCS
There is a problem that it is not possible to determine which of the states is.

According to the latter method, the occupant is seated, the occupant is determined to be an adult P or a child SP,
Although it is possible to determine whether the child is in the RFIS or FFCS state fairly accurately, it is necessary to perform image processing on image data taken by a camera and make comparison judgments with various patterns. In addition, there is a problem that the processing apparatus becomes complicated and expensive.

[0009]

Accordingly, the present applicant has
Previously, an occupant detection system as shown in FIGS. 17 to 21 has been proposed. This occupant detection system basically has a weak electric field (Ele) generated between two electrodes arranged on a sheet.
ctric field). First, as shown in FIG. 17A, when the oscillation circuit 10 for generating a high-frequency low voltage is connected to the electrode E1 and the electrode E2 is connected to the ground, the electrodes E1 and E2 are connected based on the potential difference between the electrodes. An electric field is generated, and the displacement current I
d flows. In this state, when the object OB is present in the electric field, the electric field is disturbed and the displacement current Id1 different from the displacement current Id flows to the electrode E2 as shown in FIG. Become. Most objects OB are electrically represented by conductance and capacitance, and are coupled to ground via capacitance.

Therefore, the current (displacement current) flowing to the electrode E2 changes depending on whether the object OB is on or off the vehicle seat, and this phenomenon is utilized. This makes it possible to detect the occupant's seating state on the seat. In particular, by increasing the number of electrodes, it becomes possible to obtain a lot of information about an object including an occupant on the sheet, and it is possible to more accurately detect the occupant's seating state on the sheet.

A specific occupant detection system utilizing this principle will be described with reference to FIGS. still,
The same parts as those in the conventional example shown in FIGS. 14 to 16 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 18 shows a sheet according to the prior art, in which a plurality of electrodes are arranged on the front side of the sheet 1 in the passenger seat. Specifically, for example, rectangular electrodes E1 and E2 are arranged in the seating portion 1a, and electrodes E3 and E4 having substantially the same shape are arranged in the backrest portion 1b. These electrodes are formed of a conductive cloth in consideration of the occupant's comfort, but weaving a thread-like metal on the sheet cloth surface, applying conductive paint to the cloth surface, It can also be configured by arranging plates. These electrodes E1 to E4 are shown in FIG. 19 (FIG. 20).
Is connected to and incorporated in the circuit shown in FIG.

In FIG. 19, the occupant detection system has a frequency of about 100 KHz and a voltage of 10 to 12 V, for example.
An oscillation circuit 10 for generating a high-frequency low voltage of the order, a load current detection circuit 11, a transmission / reception switching circuit 12, a current / voltage conversion circuit 13 having an amplification function, a bandpass function (unnecessary noise removal function), A detection circuit (demodulation circuit) 14 having an AC-DC conversion function, an amplification circuit 15, an offset conversion circuit 16, and a control circuit 17 such as an MPU
And an airbag device 18. FIG.
19 is a more specific example of the circuit shown in FIG. 19. The amplifier circuit 15 includes a first amplifier circuit 15A and a second amplifier circuit 15B having a gain G of 1 × and 100 ×, for example. An analog selection circuit 19 for selecting output signals of the second amplifier circuits 15A and 15B is provided.
The analog selection circuit 19 is controlled by the control circuit 17.

In this system, the load current detecting circuit 11 comprises, for example, an impedance element such as a resistor 11a connected in series to the circuit, and an amplifier 11b for amplifying the terminal voltage of the resistor 11a. 10
The current (load current) supplied to the specific electrode selected from is detected. The transmission / reception switching circuit 12 includes, for example, switching means Aa to Ad for connecting a selected one of the electrodes E1 to E4 (referred to as a transmission electrode) to the output side of the oscillation circuit 10; The other electrodes (referred to as receiving electrodes) are connected to the current / voltage conversion circuit 13 by switching means Ba to Bd. Switching of each switching means is controlled by the control circuit 17. It is desirable that the transmission / reception switching circuit 12 be constituted by a multiplexer circuit. The current / voltage conversion circuit 13 includes, for example, an impedance element such as a resistor 13a for converting a displacement current flowing on the receiving electrode side into a voltage, and an amplifier 13 for amplifying the converted voltage.
b and are provided corresponding to the respective electrodes E1 to E4. The analog selection circuit 19 includes, for example, four switching means 19a which are simultaneously selected and connected to the output side of the second amplification circuit 15B and four switching means 19 which are simultaneously selected and connected to the output side of the first amplification circuit 15A. And a switching means 19b.

The system configured as described above operates as follows. First, based on a signal from the control circuit 17, only the switching means Aa of the transmission / reception switching circuit 12 is connected to the output side of the oscillation circuit 10, and the switching means Bb to Bd are connected to the current / voltage conversion circuit 13. ,
A high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E1, and a displacement current flows through the reception electrodes E2 to E4. This current is converted into a voltage by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. On the other hand, the load current flowing through the transmission electrode E1 is detected by the load current detection circuit 11 and output to the detection circuit 14 as data R (1, 1) described later. In the detection circuit 14, for example, a signal of about 100 KHz is band-passed, and unnecessary noise components are removed.
A, 15B. The first and second amplifier circuits 1
The output signals of 5A and 15B are appropriately selected by the operation of the offset conversion circuit 16 and the analog selection circuit 19, and output to the control circuit 17. For example, if the output signal from the detection circuit 14 can be measured in the full range, the four switching means 19b of the analog selection circuit 19
Only one is simultaneously selected and connected to the output side of the first amplifier circuit 15A. When it is difficult to measure a subtle change in a full range due to a small output signal, only the four switching means 19a of the analog selection circuit 19 are simultaneously selected and connected to the output side of the second amplification circuit 15B. . Then, in the control circuit 17, the output signals from the first and second amplifier circuits 15A and 15B are A / D converted and then stored in the memory.

Next, based on a signal from the control circuit 17, the switching means Aa of the transmission / reception switching circuit 12 is opened, only the switching means Ab is connected to the output side of the oscillation circuit 10, and the switching means Ba, Bc, Bd is the current
When connected to or changed to the voltage conversion circuit 13, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E2,
Displacement currents flow in 1, E3, and E4. This current is converted into a voltage by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. The load current flowing through the transmission electrode E2 is detected by the load current detection circuit 11 and output to the detection circuit 14 as data R (2, 2) described later. The data is processed in the same manner as described above and stored in the control device 17 as data. Next, the switching means Ac
Only to the output side of the oscillation circuit 10 and the switching means Ba, Bb, Bd to the current / voltage conversion circuit 13.
When changed, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E3, and a displacement current flows through the reception electrodes E1, E2, and E4. The load current flowing through the transmission electrode E3 is detected by the load current detection circuit 11, and the data R to be described later is used.
It is output to the detection circuit 14 as (3,3). further,
When only the switching means Ad is connected to the output side of the oscillation circuit 10 and the switching means Ba, Bb, Bc is connected or changed to the current / voltage conversion circuit 13, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E4, Receiving electrode E1,
A displacement current flows through E2 and E3. These displacement currents are converted into voltages by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. The transmission electrode E
4 is detected by a load current detecting circuit 11 and is detected as data R (4, 4) to be described later.
4 is output. The processing is performed in the same manner as described above, and the control device 17
Is stored as data.

The control circuit 17 calculates the seating pattern by arithmetically processing these data. Various types of seating patterns are stored in the control circuit 17 in advance, and the seating patterns calculated by data based on various combinations of transmission electrodes and reception electrodes at the electrodes E1 to E4 are stored in advance. The stored seating pattern is compared with the stored seating pattern, and the corresponding seating pattern is extracted and determined. In the control circuit 17, for example, various seating patterns described below are provided.
Is the target of the judgment. Specifically, an empty seat pattern where no occupant is seated on the seat, an FFCS pattern where the child is seated in the child seat in the FFCS state, and a child seat where the child is in the RFIS state. R sitting at
The FIS pattern is a pattern in which an adult is seated on a sheet. The electrodes E1 to E4 are appropriately selected, and the general formula R is obtained by various combinations of transmission electrodes and reception electrodes.
The data indicated by (i, j) is obtained. The general formula R
In (i, j), i = j indicates transmission data, i ≠ j indicates reception data, and i indicates a transmission electrode, and j
Represents a receiving electrode. In the control circuit 17, arithmetic processing is performed using, for example, 16 pieces of data for each pattern, and the characteristics of the seated pattern are extracted.

When the seating pattern is detected and specified in the control circuit 17, a signal based on the detected pattern is transmitted to the airbag device 18. For example, the seating pattern is empty, FFC
In the case of S, RFIS, a signal is sent to the airbag device 18 to set the airbag so that the airbag does not expand even if the vehicle collides. In other patterns, the airbag is expanded. Is transmitted. These signals are input to the control circuit CC of the airbag device 18, and in the case of the former pattern, they are set so as not to supply a gate signal to the semiconductor switching element SW2 on the passenger seat side in the event of a collision. A gate signal is supplied to the semiconductor switching element SW1 on the driver's seat side. In the latter case, it is set so that a gate signal is supplied to the semiconductor switching elements SW1 and SW2.

According to this prior art, a plurality of electrodes E1 to E4 are arranged on the front surface side of the sheet 1, and between one selected transmitting electrode and a receiving electrode other than the transmitting electrode. Since the weak electric field is generated by the application of the high frequency and low voltage, a displacement current related to the occupant's seating pattern on the sheet 1 flows on the receiving electrode side. Therefore, by determining the characteristic pattern of the displacement current, the occupant's seating pattern can be accurately detected. For this reason, the airbag of the airbag device 18 can be set to any of a deployable state and an undeployable state according to the seating pattern of the occupant.

In addition, since a plurality of electrodes are arranged on the sheet 1 at a distance from each other, the number of combinations of transmitting electrodes and receiving electrodes can be increased, and the number of obtained data can be increased. -It is possible to more accurately determine the pattern in which the occupant sits on the vehicle.

The control circuit of the system includes, for example, RF
Since the current pattern characterized by the current flowing through each electrode based on the seating pattern of IS, FFCS, Person, Empty is stored in advance as the seating pattern, the transmitting electrode and the receiving electrode are appropriately set. By comparing received signal data obtained by combining the above with various kinds of seating patterns stored in advance and extracting the corresponding stored seating pattern, the actual seating pattern can be accurately detected.
An excellent effect such as the ability to detect the noise can be obtained.

However, recently, depending on the type of automobile, an occupant detection system having only a function of simply determining whether or not the occupant is seated in the passenger seat may be required. When the above-described occupant detection system according to the prior art is applied to such a vehicle, RFIS, FFCS,
Although the various seating patterns of Person and Empty have a function of accurately identifying and detecting the seating, only the function of detecting the presence or absence of the occupant is used, resulting in excessive quality and unnecessarily high cost. There is a problem.

However, for example, as shown in FIG.
Sensor S for detecting whether or not an occupant is seated in the passenger seat
If a weight sensor is used as D, the cost of the system can be effectively reduced, but the weight sensor only detects the weight of the object located in the passenger seat, and discriminates between a person and an object other than a person by weight. And there is a problem that another means must be adopted.

Therefore, recently, depending on the type of vehicle, there is a demand for an occupant detection system which can not only reliably detect the presence or absence of an occupant sitting on a seat but also can be configured at a low cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an occupant detection system capable of accurately and reliably detecting the presence or absence of an occupant sitting on a seat and reducing the cost.

[0025]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a sheet, substantially one antenna electrode disposed at least on the front side of the sheet, and an antenna electrode for achieving the above object. An oscillation circuit for generating a weak electric field around the antenna, a current detection circuit for detecting a current flowing from the oscillation circuit to the antenna electrode based on the weak electric field generated around the antenna electrode, and a transmission signal from the oscillation circuit. A phase difference detection circuit for detecting a phase difference from an output signal to the antenna electrode; and a control circuit for detecting whether or not an occupant is seated on a sheet based on output signals of the current detection circuit and the phase difference detection circuit. It is characterized by having.

According to a second aspect of the present invention, there is provided a sheet, at least one antenna electrode disposed at least on the front side of the sheet, and a device for generating a weak electric field around the antenna electrode. An oscillation circuit, an amplitude control circuit that controls the voltage amplitude of a transmission signal transmitted from the oscillation circuit to the antenna electrode to be substantially constant, and a current flowing from the oscillation circuit to the antenna electrode via the amplitude control circuit based on the weak electric field. A current detection circuit for detecting a transmission current, a phase difference detection circuit for detecting a phase difference between a transmission signal from an oscillation circuit and an output signal to an antenna electrode, and a current detection circuit and a phase difference detection circuit. And a control circuit for detecting whether or not an occupant is seated on the seat. The third invention includes the oscillation circuit, a current detection circuit, a phase difference detection circuit, and a control circuit. Accommodating the road in the same housing to constitute the control unit, the control unit sheet - characterized by being arranged to root section.

A fourth invention of the present invention is characterized in that the phase difference detection circuit is configured to detect a phase difference between a voltage on the oscillation circuit side of the current detection circuit and a voltage on the antenna electrode side. In a fifth aspect, the phase difference detection circuit is configured to detect a rising or falling edge of the output signal with respect to a rising edge of the transmission signal, thereby detecting a phase difference between the two signals. Characteristic, 6th
In the invention, the amplitude control circuit includes at least an amplitude variable circuit capable of varying a voltage amplitude of a transmission signal and an amplitude detection circuit detecting a voltage amplitude of the transmission signal, and transmits the signal based on an output signal of the amplitude detection circuit. The amplitude variable amount by the amplitude variable circuit is controlled so that the voltage amplitude of the signal becomes substantially constant.

Further, in a seventh aspect of the present invention, the antenna electrode is formed by extending an antenna portion disposed on a seating portion and / or a backrest portion of a sheet and extending a part of the antenna portion. According to an eighth aspect of the present invention, a connector is provided in the housing of the control unit, the connector being connected to an oscillation circuit via at least a current detection circuit. The connector of the antenna electrode is electrically connected to the connector,
In a ninth aspect of the present invention, the control circuit is based on threshold data corresponding to an occupant's seating pattern stored in advance and output signals of a current detection circuit and a phase difference detection circuit. It is characterized in that control is performed so as to detect the presence or absence of the occupant by comparing the data with the data corresponding to the occupant's seating pattern.

[0029]

Next, a first embodiment of an occupant detection system according to the present invention will be described with reference to FIGS. Incidentally, the basic principle of the present invention is to utilize the disturbance of the weak electric field generated around the antenna electrode basically in the same manner as in the above-mentioned prior art, and specifically, to dispose them on a sheet. A weak electric field is generated around one antenna electrode, and the occupant's seat is determined based on the transmission current flowing through the antenna electrode and the phase difference between the transmission signal and the output signal due to the electrical characteristics of an object located around the antenna electrode. This is to detect the presence or absence of a seat, and this is slightly different from the prior art.

FIG. 1 shows a passenger seat according to the present invention. The seat 1B is mainly composed of a seat 1a and a backrest 1b. This sheet 1B
For example, a sheet fixed to a base 2 that can be slid back and forth.
A toe frame 3, a cushion member 4 arranged on the upper part of the sheet frame 3, an antenna electrode 5 arranged along the surface at the rear side of the cushion member 4, and an antenna electrode 5
And an exterior material 6 arranged so as to cover. A control unit 20, which will be described later, is arranged inside the sheet 1B, for example, in the sheet frame 3. Although the antenna electrode 5 is arranged inside the exterior material 6, it can also be arranged outside it, and the meaning of "disposed at least on the surface side of the sheet" described in the claims is both. Is included.

In particular, the antenna electrode 5 is formed of a conductive cloth in consideration of the occupant's sitting comfort. For example, a thread-like metal is woven into a sheet cloth surface, or a conductive paint is coated on the cloth surface. It can also be configured by attaching or placing a metal plate. As shown in FIG. 2, the antenna electrode 5 is formed so as to extend mainly from the rear side of the seating portion 1a and from a part of the antenna portion 5a to a narrower width. Conductive part 5b, conductive part 5b
And a hook-type connector 5c that is caulked and fixed to the lead-out end of the connector so as to have an electrical connection relationship.
In particular, the conductive portion 5b of the antenna electrode 5 is arranged so as to extend from the back side of the cushion member 4 to the sheet frame side, and the connector 5c at the lead-out end is connected to the control unit 2 described later.
0 connector 28. The connector 5c
In addition to the hook type, an appropriate type such as a pin type or a jack-plug type can be applied.

A control unit 20 is fixed to the above-mentioned sheet 1B.
As shown in FIG. 1, an oscillation circuit 21 for generating a high-frequency low voltage having a frequency of about 100 KHz and a voltage of about 5 to 12 V, for example, and an amplitude control circuit 22 for controlling a voltage amplitude of a transmission signal from the oscillation circuit 21 to be substantially constant. A current detection circuit 25 for detecting a transmission current of a transmission signal; and a current detection circuit 25
AC-DC conversion circuit 26 for converting the output signal of
An amplifier 27 for amplifying an output signal of the AC-DC conversion circuit 26; a connector 28 connected to the current detection circuit 25 and disposed in the housing; an amplitude control circuit side (oscillation circuit side) of the current detection circuit 25; A phase difference detection circuit 2 connected to the connector side (antenna electrode side) and detecting a phase difference between a transmission signal from the oscillation circuit and an output signal to the antenna electrode.
9, an amplifier 30 for amplifying the output signal of the phase difference detection circuit 29, a control circuit 31 including an MPU, a connector 32 disposed in the housing and connected to a battery power supply (not shown), the connector 32 and the control circuit 31 And a power supply circuit 33 connected between them. For example, the airbag device 18 is connected to the control circuit 31 of the control unit 20.

In the control unit 20, the amplitude control circuit 22 comprises, for example, an amplitude variable circuit 23 for varying the voltage amplitude of the transmission signal and an amplitude detection circuit 24 for detecting the voltage amplitude of the transmission signal. The variable amplitude circuit 23 includes, for example, a programmable gain amplifier (PG
A), the amplitude detection circuit 24 includes a voltage amplitude detection unit 24a such as an operational amplifier, and an AC-DC conversion circuit 24b that converts an output signal of the detection unit 24a into a direct current. And an amplifier 24c for amplifying the output signal of the AC-DC conversion circuit 24b. The output signal of the amplifier 24c is supplied to the control circuit 31, and the variable amplitude signal for the variable amplitude section 23a is output from the control circuit 31.

In the control unit 20, the current detection circuit 25 includes, for example, an impedance element such as a resistor 25a connected in series to a circuit (transmission signal system), and a differential amplifier for amplifying the terminal voltage of the resistor 25a. Amplifier 2
5b. The output side of the current detection circuit 25 is connected to a control circuit 31 via an AC-DC conversion circuit 26 and an amplifier 27. And the current detection circuit 2
The output side of the resistor 25a at 5 is connected to a connector 28 arranged to be exposed on the outer surface of the housing.

Further, the phase difference detection circuit 29 separately shapes the transmission signal from the oscillation circuit 21 and the output signal to the antenna electrode 5 from a sine wave to a square wave, as shown in FIG. The waveform shaping circuits 29a, 29a and the first
, A second flip-flop circuit 29b2, and an integration circuit 29c, and the waveform shaping circuit 29a is configured, for example, as shown in FIG. The oscillation circuit 21
Is generated by a switching operation from a single power supply of +5 V, for example, and the waveform shaping circuit 29a can be omitted when the waveform is a square wave.

The occupant detection system thus configured operates as follows. First, when a high frequency low voltage is transmitted from the oscillation circuit 21, the voltage amplitude thereof is detected by the detection unit 24a of the amplitude detection circuit 24, and the detection signal is A
It is converted to DC by the C-DC conversion circuit 24b,
The signal is amplified at 4c and input to the control circuit 31. The control circuit 31 determines whether the detected voltage amplitude has a predetermined amplitude value, and outputs an amplitude variable signal for correcting the detected voltage amplitude to the predetermined voltage amplitude to the amplitude variable section 23a. Thereby, the voltage amplitude of the transmission signal is corrected to a predetermined amplitude,
Thereafter, the amplitude is controlled to be constant by the cooperative operation of the amplitude variable circuit 23 and the amplitude detection circuit 24.

The transmission signal whose voltage amplitude is fixed is supplied to the antenna electrode 5 via the current detection circuit 25 and the connector 28. As a result, a weak electric field is generated around the antenna electrode 5, and the sheet 1B A different level of current flows from the oscillation circuit 21 to the antenna electrode 5 depending on whether or not the occupant is seated. This current is detected by a current detection circuit 25, converted into a direct current by an AC-DC conversion circuit 26, amplified by an amplifier 27, and input to a control circuit 31.

On the other hand, the signal (voltage) at both ends of the current detection circuit 25, that is, the transmission signal from the oscillation circuit on the amplitude control circuit side and the output signal to the antenna electrode on the connector side (antenna electrode side) are converted into phase difference detection circuits 29 6, the sine wave signal is shaped into a square wave by the waveform shaping circuit 29a and output to the first and second flip-flop circuits 29b1 and 29b2, as shown in FIG.
The rising edge (arrow in the figure) of the square wave output on the transmission side is detected at the terminal CK of the first flip-flop circuit 29b1, and the terminal Q has a high output. On the other hand, the receiving side also detects the rising edge of the square wave output (arrow in the drawing) at the terminal B of the second flip-flop circuit 29b2, as shown in FIG. A low output is output as one shot. This output signal is supplied to the first flip-flop circuit 29b.
When the signal is input to the terminal RES, the output of the terminal Q of the first flip-flop circuit 29b1 is inverted to low as shown in FIG. This output becomes a phase amount (phase difference), is converted into a voltage by passing through an integration circuit 29c, and is input to a control circuit 31 via an amplifier 30.

The control circuit 31 has a sheet 1B in advance.
The threshold value for the current detected by the current detection circuit 25 when the occupant is seated in the vehicle and the threshold value for the phase difference between the transmission signal to the current detection circuit 25 and the output signal to the antenna electrode 5 are set to the threshold values. It is stored as data. Specifically, the detected current is between the average current detected by the current detection circuit 25 when the occupant is seated on the sheet 1B and the average current detected by the presence of a person other than a person. Is set as a "threshold value for recognizing that a person is almost seated". The phase difference between the average phase difference detected by the phase difference detection circuit 29 when the occupant is seated on the seat 1B and the average phase difference detected by the presence of a person other than a person. Is set as a “threshold value for recognizing that a person is seated”. Therefore, in the control circuit 31, such threshold data on the current and the phase difference stored in advance are calculated as follows:
By comparing the input current and the phase difference data, it is accurately determined whether or not the occupant is seated on the seat 1B. In particular, depending on the state of the sheet 1B (for example, wetness), a plurality of thresholds such as an upper limit and a lower limit can be set. Processing flow described later
In the description, an example using one threshold value is described. Note that the current detected by the current detection circuit 25 is the sheet 1
When the occupant is seated in B, the number increases,
When the seat is not seated, the number decreases, and there is a clear level difference between the two, and the phase difference has the same tendency.

When the control circuit 31 detects the presence or absence of the occupant, signal data based on the detection is transmitted to the airbag device 18 shown in FIG. In the figure, "to 17" should be read as "to 31". For example, the seating pattern of the passenger seat is an empty seating pattern,
In the case of the luggage placement pattern and the sheet wet pattern, a signal is sent to the airbag device 18 to set the airbag so that the airbag is not deployed even if the vehicle collides. When the occupant is seated, signal data for setting the airbag to be deployed is transmitted.
These signal data are sent to the control circuit C of the airbag device 18.
C. In the case of the former pattern, the gate signal is set so as not to supply a gate signal to the semiconductor switching element SW2 on the passenger seat side in the event of a collision. A gate signal is supplied to the semiconductor switching element SW1 on the driver's seat side. In the case of the latter pattern, the semiconductor switching element SW
1 and SW2 are set so that the gate signal is supplied.

Next, the processing flow of the occupant detection system will be described.
Will be described with reference to FIGS. First, FIG.
As shown in (1), the ignition switch is turned on to start. Initialization is performed in step S1, and the process proceeds to step S2. In step S2, an initial diagnosis relating to the communication system between the control circuit 31 and the airbag device 18 is performed. In step S3, it is determined whether or not the engine has started. If it is determined that the engine has started, the process proceeds to step S4. If it is determined that it has not started, the process returns. In step S4, the signal data relating to the current flowing through the antenna electrode 5 detected by the current detection circuit 25 is output.
Signal data relating to the phase difference detected by the data and phase difference detection circuit 29 is received. Then, step S5
Then, based on each data taken, the crew member
The seating status of the user 1B is determined. Further, step S
In S6, SRS communication is performed with the airbag device (SRS) 18 based on the determination result in step S5. When step S6 ends, the process returns to step S4, and the processes from step S4 to step S6 are repeatedly performed.
Step S3 can be omitted.

The initial diagnosis in FIG. 7 is performed, for example, as shown in FIG. First, in step SA1, the fixed data
From the control circuit 31 to the control circuit C of the airbag device 18.
Send to C. In step SA2, the airbag device 18
Receive the transmission data from. Then, Step SA3
Then, it is determined whether or not the fixed data transmitted from the control circuit 31 to the airbag device 18 and the received data from the airbag device 18 match. If it is determined that the respective data match, the processing flow is continued. If it is determined that the respective data do not match, it is determined that there is an abnormality in the communication system, a fail-safe process is performed, and, for example, a warning lamp is turned on. In this initial diagnosis, fixed data is transmitted from the airbag device 18 to the control circuit 31, and the transmitted data from the control circuit 31 is determined by the control circuit CC of the airbag device 18 regarding the coincidence. You may do so.

The occupant determination in FIG. 7 is performed, for example, as shown in FIG. First, at step SB1, it is determined whether or not received signal data relating to the current detected by the current detection circuit 25 is larger than threshold data stored in the control circuit 31 in advance. If it is determined that the received signal data (transmitted signal) is larger than the threshold data (almost the occupant is seated on the seat 1B), step SB2 is performed.
Proceed to. If it is determined in step SB1 that the received signal data is smaller than the threshold data, the process proceeds to step SB3, in which OFF data for preventing the airbag of the airbag device 18 from being deployed is output. At the same time, the processing flow is continued. In step SB2, it is determined whether or not the received signal data related to the phase difference detected by the phase difference detection circuit 29 is larger than the threshold data stored in the control circuit 31 in advance. If it is determined that the received signal data (phase difference data) is larger than the threshold data (the occupant is seated on the seat 1B), step SB4 is performed.
Proceed to. If it is determined in step SB2 that the received signal data is smaller than the threshold data, the process proceeds to step SB3. In step SB4, ON data for deploying the airbag of the airbag device 18 is set, and the SRS data communication flow is continued.

The SRS data communication in FIG. 7 is performed, for example, as shown in FIG. First, in step SC1, an ON state is set from the occupant detection unit side (the control circuit 31) to the airbag apparatus side (the control circuit CC) so that the airbag of the airbag apparatus 18 can be deployed or cannot be deployed. -Data or OFF data and check data
Data is sent. At step SC2, OK data or NG data and check data for ON data or OFF data from the airbag device are received, and the process proceeds to step SC3. In step SC3, it is determined whether the ON / OFF data and the check data transmitted from the occupant detection unit to the airbag device are returned to the occupant detection unit from the airbag device again in a normal state. You. If it is determined that it is normal (there is no abnormality in the communication system), the processing flow is continued. If it is determined that the communication system is abnormal, the process proceeds to step SC4, where it is determined whether the fail-safe timer has reached zero. The abnormality detection of the communication system is set to, for example, three times. Therefore, when it is determined that the fail-safe timer has reached zero, a fail-safe process is performed, for example, a warning light is turned on. If it is determined that the fail-safe timer has not become zero, the process proceeds to step SC5, and
The self-timer counts, and the processing flow is continued.

On the other hand, in step SD1, the airbag device side (control circuit CC) is connected to the occupant detection unit side (control circuit 3).
From 1), ON data or OFF data and check data for bringing the airbag of the airbag device 18 into a deployable state or an undeployable state are received. In step SD2, the received data is checked to determine whether the received data has been normally received. In any case, the process proceeds to step SD3, where O
K data or NG data and check data are transmitted to the occupant detection unit. If it is determined in step SD2 that there is no abnormality in the communication system, the OK data in step SD3 is output.
After the data transmission step, the process proceeds to step SD4. In step SD4, the data on the airbag device side is updated based on the OK data. As a result, the airbag is updated and set to one of a deployable state and an undeployable state. If it is determined in step SD2 that there is something wrong with the communication system, the flow advances to step SD5 via the NG data transmission step in step SD3. In this step SD5, it is determined whether or not the fail-safe timer has become zero. Incidentally, the abnormality detection of this communication system is, for example, 3
Set to times. Therefore, when it is determined that the fail-safe timer has reached zero, a fail-safe process is performed, for example, a warning light is turned on. If it is determined that the fail-safe timer has not become zero, the process proceeds to step SD6, where the fail-safe timer is counted, and the processing flow is continued.

According to this embodiment, a weak electric field is generated around the antenna electrode 5 based on the high-frequency low voltage supplied from the oscillation circuit 21 to the antenna electrode 5, and the current flowing based on the weak electric field is generated. Varies depending on the object existing on the sheet 1B. In particular, when the object is a person, a current having a level difference that can be distinguished from that of other objects flows. Accordingly, by detecting the current flowing in the transmission signal system by the current detection circuit 25, it is possible to easily detect whether or not the occupant is seated on the seat 1B.

Further, the phase difference between the transmission signal from the oscillation circuit on the oscillation circuit side and the antenna electrode side of the current detection circuit 25 and the output signal to the antenna electrode 5 differs depending on the object existing on the sheet 1B. In particular, when the object is a person, the object has a phase difference of a level difference that can be identified as compared with other objects. Therefore, by detecting the phase difference by the phase difference detection circuit 29, the occupant's seat 1B can be simply combined with the judgment of the signal data related to the detected current.
The presence / absence of a seat can be accurately and reliably detected.

In particular, since the antenna electrode 5 is composed of one, the circuit configuration is simplified and the system cost can be reduced as compared with the above-described prior art in which a plurality of electrodes are used. .

Since the voltage amplitude of the transmission signal transmitted to the antenna electrode 5 is controlled by the amplitude control circuit 22 to be substantially constant, the data related to the current detected by the current detection circuit 25 A simple comparison between the data and the threshold data stored in the control circuit 31 enables highly reliable and accurate detection.

Further, the control circuit 31 determines whether or not the occupant is seated on the seat 1B, and when the occupant is seated on the passenger seat, the airbag device 18 is controlled to operate. Since the safety of the occupant during traveling can be ensured and the airbag device 18 is controlled so as not to operate when the seat 1B is vacant or when luggage or the like is placed on the seat 1B, it is assumed that Even if a collision accident occurs, undesired deployment of the airbag can be prevented.

Further, the antenna part 5 is provided on the antenna electrode 5.
Since the conductive portion 5b is formed to extend from a part of the connector a, the connector 5c provided on the conductive portion 5b is connected to the connector 28 of the control unit 20 disposed on the sheet 1B. The harness connecting the antenna unit 5a and the control unit 20 can be omitted completely. Therefore, the cost of the system can be effectively reduced in combination with the above-described unification of the antenna electrode 5 and simplification of the circuit configuration.

FIG. 11 shows a second embodiment of the occupant detection system according to the present invention, which is basically the same as the embodiment shown in FIG. The difference is that the control unit 2
In other words, a seat belt warning lamp 34 and a seat belt detection circuit 35 are connected to the control circuit 31 of FIG. The airbag device 18 can be used together.

In this embodiment, the control circuit 31 uses the sheet 1 based on data relating to the transmission current and the phase difference.
When it is determined that the occupant is seated at B, the seat belt detection circuit 35 detects whether the occupant is wearing a seat belt. If it is determined that the seat belt is not worn, the control circuit 31 outputs a warning signal to the seat belt warning light 34 to blink the warning light. If the detection result indicates that the seat belt is worn, no warning signal is output to the seat belt warning lamp 34, and the warning lamp does not blink. Further, if the occupant is not seated on the seat 1B, the seat belt warning lamp 3 is irrespective of the output signal from the seat belt detection circuit 35.
4 does not work. When an object other than a person, for example, a luggage is placed in the passenger seat, the dielectric constant is smaller than that of the person, so that the current amount detected by the current detection circuit 25 and the phase difference detection circuit 29 The detected phase difference is also smaller than when the occupant is seated, and there is no erroneous determination that the occupant is seated.

In particular, according to this embodiment, the control circuit 31
Is based on the detection result of the occupant and the wearing state of the seat belt, although the occupant is seated on the seat 1B,
When the belt is not worn, a warning signal is output to the seat belt warning light 34, and the warning light flashes, so that the seat belt can be worn, and safety during traveling can be expected.

FIG. 12 shows a third embodiment of an occupant detection system according to the present invention. The basic configuration is the same as that of the above-described embodiment. The difference is that the antenna portion 5a of the antenna electrode 5 covers almost the entire seating portion 1a of the sheet 1B.
And the conductive portion 5b is arranged so as to extend from the front side of the cushion member 4 to the sheet frame side, and the connector 5c at the lead-out end is connected to the connector 28 of the control unit 20.

According to this embodiment, since the arrangement area of the antenna electrode 5 is enlarged, the determination of the signal 1 relating to the transmission current and the phase difference is made, and the sheet 1B is Erroneous detection due to water wetting can be prevented.

FIG. 13 shows a fourth embodiment of the occupant detection system according to the present invention. The basic configuration is the same as that of the above-described embodiment. The difference is that one antenna electrode 5A is provided on the seat 1a and the backrest 1b of the sheet 1C.
That is, The antenna electrode 5A and the antenna portion 5a ₁ disposed in seated portion 1a, the backrest portion 1b
Antenna unit and 5a _2, conductive portion 5b which is formed extending from the side of the antenna portion 5a ₁ in a narrow state width disposed
And a connector 5c provided at an end of the conductive portion 5b. The conductive portion 5b extends from the side surface of the sheet 1C toward the control unit 20 and is connected to the connector 5c.
Are connected to the control unit 20.

According to this embodiment, since the area of the antenna electrode 5A is significantly increased, it is expected that the occupant detection accuracy is further improved. The area of the antenna portion 5a ₁ and the antenna portion 5a ₂ is - can be changed and set as appropriate according to the area of the root section.

It should be noted that the present invention is not limited to the above-described embodiment, but the shape of the antenna electrodes arranged on the sheet may be rectangular, circular, elliptical, or polygonal except square. It can also be formed. Also, the antenna section and the conductive section may be constituted by two pieces, and the antenna section and the conductive section may be connected by connectors provided respectively, or the conductive section may be replaced by a wire harness.
The output frequency of the oscillation circuit is set to 1 depending on the detection target.
The frequency can be set to a value other than 00 kHz, the voltage can be used outside the range of 5 to 12 V, and the output waveform can be set to a sine wave or a rectangular wave. Furthermore, the interlocking with the wearing state of the airbag device and the seat belt can be omitted.

[0060]

As described above, according to the present invention, a weak electric field is generated around the antenna electrode based on the high-frequency low voltage supplied from the oscillation circuit to the antenna electrode. The current flowing depends on the objects present on the sheet. In particular, when the object is a person, a current having a level difference that can be distinguished from that of other objects flows. Therefore, by detecting the current flowing in the transmission signal system by the current detection circuit, the presence or absence of the occupant sitting on the seat can be easily detected.

Further, the phase difference between the transmission signal from the oscillation circuit and the output signal to the antenna electrode on the oscillation circuit side and the antenna electrode side of the current detection circuit differs depending on the objects existing on the sheet. In particular, when the object is a person, the object has a phase difference of a level difference that can be identified as compared with other objects. Accordingly, by detecting the phase difference by the phase difference detection circuit, it is possible to easily and accurately determine whether or not the occupant is seated on the seat, together with the determination of the signal data related to the detected current. Can be detected.

In particular, since the antenna electrode is composed of one, the circuit configuration is simplified and the cost of the system can be reduced as compared with the above-described prior art in which a plurality of electrodes are used.

Further, if the antenna electrode is formed so as to extend a conductive portion from a part thereof and connect the lead-out end to a control unit disposed in the sheet portion, the antenna electrode and the antenna electrode can be connected to each other. Since the harness for connecting to the control unit can be completely omitted, the cost of the system can be effectively reduced in combination with the simplification of the antenna electrode and the simplification of the circuit configuration.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a seat of an occupant detection system according to the present invention.

FIG. 2A is a plan view of an antenna electrode of the occupant detection system according to the present invention, and FIG. 2B is a cross-sectional view of a connector portion in a conductive portion.

FIG. 3 is a circuit block diagram of a control unit of the occupant detection system according to the present invention.

4 is an essential part cross-sectional view showing a connection state between the control unit and the antenna electrode shown in FIG. 3;

5A is a specific circuit diagram of the phase difference detection circuit shown in FIG. 3, and FIG. 5B is a specific circuit diagram of a waveform shaping circuit.

6A and 6B are diagrams for explaining the operation of the phase difference detection circuit shown in FIG. 5A, wherein FIG. 6A is a diagram showing an output signal waveform of a first flip-flop circuit, and FIG. b) is the second
FIG. 3C is a diagram showing an output signal waveform of the flip-flop circuit of FIG. 2, and FIG. 3C is a diagram showing a state of detecting a phase amount from output signals of the first and second flip-flop circuits.

FIG. 7 is a flowchart of occupant detection by the occupant detection system according to the present invention.

FIG. 8 is a flowchart of the initial diagnosis shown in FIG. 7;

FIG. 9 is a flowchart for occupant determination shown in FIG. 7;

FIG. 10 is a flowchart of the SRS communication shown in FIG. 7;

FIG. 11 is a circuit block diagram of another embodiment of the occupant detection system according to the present invention.

FIG. 12 is an essential part cross-sectional view of another embodiment of the seat of the occupant detection system according to the present invention.

FIG. 13 shows still another embodiment of the seat of the occupant detection system according to the present invention, and FIG.
2 is a side view, and FIG. 2B is a plan view of an antenna electrode.

FIG. 14 is a circuit block diagram of an airbag device according to a conventional example.

15A and 15B are diagrams showing various seating patterns, wherein FIG. 15A shows a state where an adult occupant is seated on a sheet, and FIG. 15B shows a state of RFIS. FIG.
FIG. 3 is a diagram showing a state of FFCS.

FIG. 16 is a circuit block diagram of an improved airbag device according to a conventional example.

17A and 17B are diagrams for explaining a basic operation of the occupant detection system according to the prior art which is a premise of the present invention, wherein FIG. 17A is a diagram showing an electric field distribution between electrodes, and FIG. FIG. 4 is a diagram showing an electric field distribution when an object exists between electrodes.

FIG. 18 is a perspective view of a sheet of the occupant detection system according to the prior art.

FIG. 19 is a circuit block diagram of an occupant detection system according to the prior art.

FIG. 20 is a specific circuit block diagram of FIG. 19;

21 is a detailed circuit block diagram of the airbag device shown in FIG.

[Explanation of symbols]

1B, 1C sheet - DOO 1a seating portion 1b backrest 3 - Tofure - arm 4 cushioning material 5,5A antenna electrode 5a, 5a _1, 5a ₂ antenna portion 5b conductive portion 5c connector 6 outer member 18 the airbag device 20 control unit Reference Signs List 21 oscillation circuit 22 amplitude control circuit 23 amplitude variable circuit 24 amplitude detection circuit 25 current detection circuit 26 AC-DC conversion circuit 27, 30 amplifier 28, 32 connector 29 phase difference detection circuit 31 control circuit 33 power supply circuit 34 seat belt warning light 35 Sheet belt detection circuit

Continuation of the front page (56) References JP-A-9-207644 (JP, A) JP-A-7-270541 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60N 5 / 00 B60R 21/32 G01V 3/08

Claims (9)

(57) [Claims] 1. A sheet, substantially one antenna electrode disposed at least on the surface side of the sheet, an oscillation circuit for generating a weak electric field around the antenna electrode, and a sheet around the antenna electrode. A current detection circuit that detects a current flowing from the oscillation circuit to the antenna electrode based on the generated weak electric field, a phase difference detection circuit that detects a phase difference between a transmission signal from the oscillation circuit and an output signal to the antenna electrode, An occupant detection system, comprising: a control circuit for detecting whether or not an occupant is seated on a seat based on output signals of a current detection circuit and a phase difference detection circuit. 2. A sheet, substantially one antenna electrode disposed at least on the front side of the sheet, an oscillation circuit for generating a weak electric field around the antenna electrode, and an antenna electrode from the oscillation circuit. An amplitude control circuit that controls the voltage amplitude of the transmission signal transmitted to be substantially constant; and a current detection circuit that detects a transmission current flowing from the oscillation circuit to the antenna electrode via the amplitude control circuit based on the weak electric field. ,
A phase difference detection circuit for detecting a phase difference between a transmission signal from the oscillation circuit and an output signal to the antenna electrode, and presence or absence of an occupant on a seat based on output signals of the current detection circuit and the phase difference detection circuit An occupant detection system, comprising: a control circuit for detecting an occupant. 3. A control unit including the oscillating circuit, the current detecting circuit, the phase difference detecting circuit, and the control circuit, and these circuits are housed in the same housing to form a control unit, and the control unit is disposed in a sheet portion. The occupant detection system according to claim 1 or 2, wherein: 4. The phase difference detection circuit according to claim 1, wherein the phase difference detection circuit detects a phase difference between a voltage on the oscillation circuit side of the current detection circuit and a voltage on the antenna electrode side. Occupant detection system. 5. The phase difference detection circuit according to claim 1, wherein a phase difference between the two signals is detected by detecting a rising edge or a falling edge of the output signal with respect to a rising edge of the transmission signal. The occupant detection system according to claim 1. 6. The amplitude control circuit includes at least an amplitude variable circuit capable of varying a voltage amplitude of a transmission signal, and an amplitude detection circuit detecting a voltage amplitude of the transmission signal, based on an output signal of the amplitude detection circuit. 3. The occupant detection system according to claim 2, wherein the amplitude variable amount by the amplitude variable circuit is controlled so that the voltage amplitude of the transmission signal is substantially constant. 7. The antenna device according to claim 1, wherein the antenna electrode is provided on an antenna portion disposed on a seating portion and / or a backrest portion of the sheet, a conductive portion formed by extending a part of the antenna portion, and a conductive portion. The occupant detection system according to claim 1, further comprising a connector. 8. A connector connected to an oscillation circuit via at least a current detection circuit in a housing of the control unit, and a connector of an antenna electrode is electrically connected to the connector. The occupant detection system described. 9. The occupant's seating pattern based on threshold data corresponding to an occupant's seating pattern stored in advance and output signals of a current detection circuit and a phase difference detection circuit. 3. The occupant detection system according to claim 1, wherein control is performed so as to detect whether or not the occupant is seated by comparing data corresponding to the occupant.