JP2007322685A - Density measurement device for liquid developer and wet type image forming apparatus comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a density measurement device for a liquid developer capable of correctly measuring the density of particles with a simple constitution, and to provide an image forming apparatus. <P>SOLUTION: A transparent tube 40 is pressed by a first pressing member 50, and, in a state where the transparent tube 40 is deformed, density measurement is performed äSee (b)}. In this state, the cross-section of the transparent tube 40 has oval shape, and is simultaneously sandwiched between the first pressing face 51 and the second pressing face 61 each composed of a flat face, thus the parts in contact with the first and second pressing faces 51, 61 in the transparent tube 40 are deformed, so as to be planar shape. Infrared light emitted from a light emitting element 52 passes through the part deformed into the planar shape in the transparent tube 40, thus is not refracted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a liquid developer concentration measuring device and a wet image forming apparatus provided with the liquid developer concentration measuring device.
In an electrophotographic image forming apparatus, it is a mainstream to transfer an electrostatic latent image on a photosensitive drum using powder toner. However, a liquid developer in which toner particles are dispersed in a carrier liquid is used. There has been proposed a liquid developing apparatus that develops an electrostatic latent image using the liquid developing apparatus (for example, Patent Document 1).

The particle concentration of the liquid developer applied to the photosensitive drum (the ratio of the toner particles to the entire liquid developer) is maintained within an appropriate range so that a high-quality image can be obtained. The particle concentration must be accurately measured.
In Patent Document 1, a light emitting unit and a light receiving unit are arranged opposite to each other with a liquid developer in a container in which a liquid developer is stored, and the amount of light received by the light receiving unit when the light emitting unit emits light Based on this, it is disclosed to measure the particle concentration of a liquid developer.
JP 2005-315948 A

  When such a method is used, the light emitting unit and the light receiving unit need to be disposed close to each other at the time of measurement, but light emission is performed so that the toner component of the liquid developer does not stop at one place during normal times other than the measurement. The distance between the light receiving portion and the light receiving portion needs to be kept wide. Therefore, it is conceivable to use a concentration measuring device in which the light receiving unit is slidable with respect to the light emitting unit as in Patent Document 1. However, if a movable light receiving unit is provided in a container in which the liquid developer is stored, the structure of the density measuring device becomes complicated.

The present invention has been made based on such a background, and an object of the present invention is to provide a liquid developer concentration measuring apparatus capable of accurately measuring the particle concentration with a simple configuration.
Another object of the present invention is to provide a wet image forming apparatus capable of stably obtaining a good image.

  The invention described in claim 1 is provided as a transport path (38) for the liquid developer, and has a pair of translucent, flexible, and restorable tubes (40) and a pair of the tubes disposed between the tubes. A first member (50) having a transparent first pressing surface (51) facing the tube, and a transparent second facing the tube and the first pressing surface and arranged parallel to the first pressing surface. A pressing member (50, 60) including a second member (60) having a pressing surface (61) and a first wavelength member embedded in the first member and radiating light in a predetermined wavelength range outward from the first pressing surface. A light emitting element (52), a light receiving element (62) embedded in the second member, for receiving light that passes through the tube and reaches the second pressing surface, and a pressing member connected to the pressing member. Measuring position where the tube is pressing the tube in a predetermined state, and the pressing member A displacement device that displaces on the release position not to press the tube (70) and density measuring system for a liquid developer comprising (37, 40).

The numbers in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
The invention according to claim 2 is provided as a transport path (38) for the liquid developer, and is disposed with the tube (40) having translucency, flexibility and resilience interposed between the tubes. A pair of members, a first member (50) having a transparent first pressing surface (51) facing the tube, and a mirror surface facing the tube and the first pressing surface and arranged in parallel with the first pressing surface A pressing member (50, 60) comprising a second member (60) having a configured second pressing surface (61), and a light in a predetermined wavelength range embedded in the first member to remove light from the first pressing surface. And a light receiving element (62) for receiving reflected light that is embedded in the first member, passes through the tube, is reflected by the second pressing surface, and returns to the first member. ) And the pressing member, and the pressing member predetermines the tube. A measurement position in which the pressing state, the concentration measuring apparatus of the liquid developer which comprises a displacement device that displaces on the release position not to press the tube (70) (37, 40).

A third aspect of the invention is the liquid developer concentration measuring apparatus according to the first or second aspect, wherein the tube is formed of a transparent soft tube and has a thickness of 1 mm or less.
The invention according to claim 4. The distance between the first pressing surface and the second pressing surface at the measurement position is maintained at an interval of 1/2 or more of the outer diameter of the tube. It is a density | concentration measuring apparatus of the liquid developer of description.

  According to a fifth aspect of the present invention, there is provided a wet type comprising the liquid developer concentration measuring device according to any one of the first to fourth aspects in a transport path of the liquid developer that connects the containers for storing the liquid developer. An image forming apparatus (1).

According to the first and second aspects of the invention, at the time of measurement, light emitted from the light emitting element passes through the deformed tube along the pressing surface, so that there is almost no influence due to light refraction. As a result, the particle concentration can be accurately measured with a simple configuration using the conveyance path.
Further, if the first member is in the release position except during measurement, and the first member is positioned in the measurement position only during measurement, the flow of the liquid developer in the tube is not hindered during normal times. . Thereby, the particle concentration of the liquid developer can be measured without hindering the flow of the liquid developer in the tube.

  According to the invention described in claim 3, by using a soft tube and setting the thickness of the tube to 1 mm or less, the tube is deformed by an appropriate amount by pressing with the pressing member. For this reason, the particle concentration of the liquid developer can be measured more accurately. Further, since the soft tube is transparent, the amount of light received by the light receiving element is large. Thereby, the measurement accuracy of the particle concentration of the liquid developer can be improved.

According to the fourth aspect of the present invention, the tube is not deformed by an appropriate amount due to the pressing of the pressing member, and the tube is not excessively deformed. For this reason, the particle concentration of the liquid developer can be measured more accurately.
In the fifth aspect of the invention, since the liquid developer concentration measuring device according to any one of the first to fourth aspects is employed, the development is performed using the liquid developer adjusted to an appropriate particle concentration. It is possible to provide a wet image forming apparatus capable of stably obtaining a stable image.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic view showing a configuration of a wet image forming apparatus according to an embodiment of the present invention.
The wet image forming apparatus 1 forms a color image, and includes a first image forming mechanism 11, a second image forming mechanism 12, and a third image forming mechanism 13. In the wet image forming apparatus 1, each of the image forming mechanisms 11 to 13 is configured for cyan (C), magenta (M), and yellow (Y) in order from the top in FIG. Yes. Although the black (BK) image forming mechanism is not illustrated in FIG. 1, the wet image forming apparatus 1 may include a black (BK) image forming mechanism.

  Each of the image forming mechanisms 11 to 13 includes cylindrical photosensitive drums 2C, 2M, and 2Y, chargers 3C, 3M, and 3Y for charging the surfaces of the photosensitive drums 2C to 2Y, and chargers 3C to 3Y. Exposure units 4C, 4M, and 4Y for exposing the surfaces of the charged photosensitive drums 2C to 2Y corresponding to the image to be created, and liquid developers of respective colors are supplied to the surfaces of the photosensitive drums 2C to 2Y. The liquid developing devices 6C, 6M, 6Y for developing the electrostatic latent images formed by exposure and the surfaces of the photosensitive drums 2C-2Y after the toner images are transferred to the intermediate transfer belts 10C, 10M, 10Y. Cleaning devices 7C, 7M, and 7Y for removing the remaining liquid developer, and neutralizers 8C, 8M, and 8Y for neutralizing the surface of the photosensitive drum 2 after the toner image is transferred are provided. Yes.

The toner images of the respective colors developed on the surfaces of the photosensitive drums 2C to 2Y are temporarily transferred to the endless intermediate transfer belts 10C, 10M, and 10Y, and the toner images are transferred to a sheet by a secondary transfer roller (not shown). . The sheet on which the toner image has been transferred is heated and pressed by a fixing device (not shown), whereby the full-color toner image is fixed on the sheet.
Each of the liquid developing devices 6C to 6Y has a configuration that is substantially common to each other. However, the cyan liquid developing device 6C will be described as an example, and the description of the configurations of the other liquid developing devices 6M and 6Y will be omitted.

  The liquid developing device 6C is in contact with the supply pot 20 in which the liquid developer is stored, the supply roller 21 that draws the liquid developer from the supply pot 20, and the peripheral surface of the supply roller 21, and is drawn by the supply roller 21. A coating roller 22 for applying the liquid developer onto the peripheral surface of the developing roller 23, and a developing roller as a liquid developer carrier for contacting the surface of the photosensitive drum 2 and supplying the liquid developer to the photosensitive drum 2. 23.

  The supply roller 21 enters the supply pot 20 and is immersed in the liquid developer stored in the supply pot 20. The liquid developer in the supply pot 20 has high wettability, so that the liquid developer is pumped by the rotation of the supply roller 21 and is given to the surface of the photosensitive drum 2 via the application roller 22 and the development roller 23. It is done. The developing roller 23 is provided with a cleaning blade 24 that scrapes off the liquid developer remaining on the surface of the developing roller 23 after the image is formed on the surface of the photosensitive drum 2.

Furthermore, the liquid developing device 6C includes a preparation pot 26 that stores the liquid developer to be supplied to the supply pot 20 while adjusting the particle concentration within an appropriate range, and a toner that stores the liquid developer supplied to the preparation pot 26. A tank 27 and a recovery pot 28 for storing the liquid developer scraped and recovered by the cleaning blade 24 are provided.
The liquid developer is supplied to the blending pot 26 from the toner tank 27 through the new developer transport path 29. The liquid developer is obtained by dispersing powder toner in a carrier liquid. However, a high-viscosity carrier liquid is used, and thus the liquid developer has a high viscosity. A valve 30 is interposed in the new developer conveyance path 29, and the liquid developer is applied from the toner tank 27 to the preparation pot 26 by opening the valve 30.

In the liquid developing device 6C, the recovered liquid developer is used again for development, and the liquid developer is supplied to the preparation pot 26 from the recovery pot 28 via the recovered developer conveyance path 31. It has become. A valve 32 is interposed in the collected developer conveyance path 31, and when this valve 32 is opened, the liquid developer in the collected pot 28 is applied to the preparation pot 26.
Further, a carrier liquid tank 34 is connected to the preparation pot 26 via a carrier liquid transport path 33 and a branch path 33C. The carrier liquid tank 34 stores a transparent carrier liquid for diluting the liquid developer. As the carrier liquid, one having a high viscosity such as liquid paraffin or silicone oil is used.

At the bottom of the blending pot 26, a stirring blade 36 for stirring the liquid developer is installed. The new developer supplied from the toner tank 27, the recovered developer supplied from the recovery pot 28, and the carrier liquid supplied from the carrier liquid tank 34 are stirred by the stirring blade 36 and stored in a mixed state.
The preparation pot 26 is connected to the supply pot 20 via a liquid developer conveyance path 38. A valve 39 is interposed in the middle of the liquid developer conveyance path 38. A concentration measuring device 37 that measures the particle concentration of the liquid developer flowing in the liquid developer conveying path 38 is attached to the liquid developer conveying path 38 upstream of the valve 39. The concentration measuring device 37 detects the particle concentration in the preparation pot 26 by measuring the particle concentration of the liquid developer flowing in the liquid developer conveying path 38. Based on the particle concentration of the liquid developer measured by the concentration measuring device 37, the valves 30, 35C, and 32 are opened by feedback control, so that the concentration of the liquid developer in the preparation pot 26 is maintained in an appropriate range. ing. A branch path 14 branches from the liquid developer transport path 38 from the middle of the liquid developer transport path 38. The other end of the branch path 14 is connected to a blending pot 26, and a valve 15 is interposed in the branch path 14. When the valve 15 is opened, the liquid developer in the liquid developer conveying path 38 is returned to the blending pot 26 through the branch path 14. Thus, the liquid developer used for density measurement is returned to the preparation pot 26. The branch path 14 is branched upstream of the valve 39 in the liquid developer transport path 38.

By opening the valve 39, the liquid developer adjusted to an appropriate concentration is supplied to the supply pot 20.
The carrier liquid tank 34 supplies the carrier liquid to the preparation pots 26 of all the liquid developing devices 6C to 6Y. For each color branched from the carrier liquid conveyance path 33 connected to the carrier liquid tank 34. The carrier liquid is supplied to the preparation pots 26 of the liquid developing devices 6C to 6Y through the branch paths 33C, 33M, and 33Y. A valve 35C is interposed in the cyan branch 33C, and a valve 35M is interposed in the magenta branch 33M.

FIG. 2 is a perspective view showing a state in which the density measuring device is attached to the liquid developer conveyance path.
The liquid developer conveyance path 38 is constituted by a transparent tube 40 made of a soft fluororesin having an outer diameter of 7 mm, for example. For this reason, the transparent tube 40 has flexibility and a restoring property. Further, since the transparent tube 40 is made of a fluororesin, the transparent tube 40 has a property of easily transmitting infrared light. The transparent tube 40 has a hardness of, for example, A65 and a thickness of, for example, 0.8 mm.

The concentration measuring device 37 is a transmissive optical sensor, and includes a first pressing member 50 and a second pressing member 60 arranged with the transparent tube 40 interposed therebetween.
The first pressing member 50 has a flat first pressing surface 51 that faces the transparent tube 40. The first pressing member 50 is made of transparent, for example, polycarbonate resin. A light emitting element 52 is embedded in the first pressing member 50 at a position facing the first pressing surface 51. Since the first pressing member 50 is made of a transparent polycarbonate resin, the infrared light emitted from the light emitting element 52 is transmitted through the first pressing surface 51. That is, the light emitting element 52 irradiates infrared light outward from the first pressing surface 51.

The light emitting element 52 emits infrared light having a predetermined wavelength, and is constituted by, for example, an infrared diode having an emission peak wavelength of 850 nm. As the light emitting element 52, the liquid developer T of each color is measured in advance, and based on this, the one having the light emission peak wavelength most suitable for the liquid developer T of each color is selected.
The second pressing member 60 has a flat second pressing surface 61 that faces the first pressing surface 51. The second pressing surface 61 is parallel to the first pressing surface 51. The second pressing member 60 is made of a transparent resin, for example, a polycarbonate resin. A light receiving element 62 made of, for example, a phototransistor is embedded at a position facing the second pressing surface 61 of the second pressing member 60. The light receiving element 62 is disposed to face the light emitting element 52 described above. Since the second pressing member 60 is made of a transparent polycarbonate resin, the infrared light passes through the second pressing surface 61.

  Infrared light emitted from the light emitting element 52 is received by the light receiving element 62 through the first pressing surface 51, the transparent tube 40, the liquid developer T and the second pressing surface 61. As described above, since the transparent tube 40, the first pressing surface 51, and the second pressing surface 61 have the property of transmitting infrared light, the infrared light emitted from the light emitting element 52 is transmitted through the transparent tube. Only the liquid developer T within 40 is absorbed. Therefore, the infrared light received by the light receiving element 62 is only affected by the liquid developer T in the transparent tube 40.

The concentration measuring device 37 further includes a displacement device 70 that slides the first pressing member 50 relative to the second pressing member 60. The 1st press member 50 makes the space | interval with the 2nd press member 60 variable, keeping the 1st press surface 51 and the 2nd press surface 61 in a mutually parallel state. The concentration measuring device 37 and the transparent tube 40 constitute a concentration measuring device.
The displacement device 70 is connected and fixed to the first pressing member 50, extends in a direction perpendicular to the first pressing surface 51, and a drive motor 72 that drives the slide member 71 to displace it. It has. A drive gear 74 attached to the output shaft 73 of the drive motor 72 so as to be integrally rotatable meshes with the engagement surface 71A of the slide member 71, and the slide member 71 is slid and displaced by the rotational drive of the drive motor 72.

The drive motor 70 is driven and controlled by the control unit 80. The control unit 80 includes a light emission control circuit (not shown) that controls light emission of the light emitting element 52 and a light reception control circuit (not shown) that controls light reception of the light receiving element 62. The control unit 80 may be provided separately from the main control unit of the image forming apparatus 1 or may be included in the main control unit.
The first pressing member 50 slides and displaces between a measurement position where the transparent tube 40 is pressed and a release position where the transparent tube 40 is not pressed.

FIG. 3 is a schematic view seen from the direction of arrow III in FIG. (A) shows the state where the first pressing member 50 is in the release position, and (b) shows the state where the first pressing member 50 is in the measurement position. As shown in FIG. 3B, the transparent tube 40 is pressed by the first pressing member 50, and the concentration measurement of the particle concentration of the liquid developer T is performed in a state where the transparent tube 40 is deformed.

In the state shown in FIG. 3A (the state where the first pressing member 50 is in the release position), the transparent tube 40 has a circular cross-sectional shape. When the drive motor 72 is driven from this state, the first pressing member 50 is slid in the direction approaching the second pressing member 60 and eventually presses the transparent tube 40.
In the state shown in FIG. 3B (the state where the first pressing member 50 is at the measurement position), the interval W between the first pressing surface 51 and the second pressing surface 61 is 4 mm, and the outer diameter of the transparent tube 40 is It is kept at an interval of 1/2 or more of D (7 mm). At this time, the cross-sectional shape of the transparent tube 40 is an oval shape. Since the transparent tube 40 is sandwiched between the first pressing surface 51 and the second pressing surface 61 which are flat surfaces, the first and second pressing surfaces of the transparent tube 40 are in a state where the first pressing member 50 is at the measurement position. The portions in contact with 51 and 61 are deformed into a flat plate shape. Infrared light emitted from the light emitting element 52 passes through a portion of the transparent tube 40 that is deformed into a flat plate shape. For this reason, infrared light is not refracted. Thus, the particle concentration of the liquid developer T can be accurately measured with a simple configuration using the liquid developer conveyance path 38.

  The distance between the first pressing surface 51 and the second pressing surface 61 at the time of measurement is preferably at least half of the outer diameter D of the transparent tube 40. If the amount of deformation is not a certain amount, the transparent tube 40 does not have an oval shape and cannot perform appropriate measurement, but the distance between the first pressing surface 51 and the second pressing surface 61 is less than half of the outer diameter D. This is because the transparent tube 40 is greatly deformed and becomes a gourd shape.

  FIG. 4 is a diagram showing the relationship between the particle concentration and transmittance of the liquid developer. There is a relationship shown in FIG. 4 between the toner particle concentration and the transmittance. As described above, the infrared light received by the light receiving element 62 is only affected by the liquid developer T in the transparent tube 40. For this reason, the output value of the light receiving element 62 reflects the transmittance between the first pressing surface 51 and the second pressing surface 61. For this reason, the particle concentration of the liquid developer T has a certain relationship with the output value of the light receiving element 62, whereby the control unit 80 calculates the particle concentration of the liquid developer T based on the output value of the light receiving element 62. .

The wall thickness of the transparent tube 40 is preferably 1 mm or less. This is because when the thickness of the transparent tube 40 exceeds 1 mm, the transparent tube 40 is not easily deformed, and the transparent tube 40 does not become an oval shape even when pressed by the first pressing member 50 during measurement.
In this embodiment, the transparent tube 40 is not deformed at normal times, and the transparent tube 40 is deformed only at the time of measurement. Therefore, the flow of the liquid developer T in the transparent tube 40 is not obstructed at normal times. Further, the toner component of the liquid developer T does not stay in the transparent tube 40.

Further, at the time of measurement, the transparent tube 40 is deformed by pressing, but when the toner component of the liquid developer T is fixed to the transparent tube 40, the toner component is peeled off. It is also possible to prevent the conveyance path 38 from being clogged.
The present invention is not limited to the embodiment described above.
In the above description, the concentration measuring device 37 has been described as a transmissive optical sensor, but may be a reflective optical sensor. In this case, not only the light emitting element 52 but also the light receiving element 62 is disposed on the first pressing member 50, and the second pressing surface 61 of the second pressing member 60 is configured as a mirror surface. The infrared light emitted from the light emitting element 52 is reflected by the second pressing surface 61 formed of a mirror surface and is received by the light receiving element 62 embedded in the first pressing member 50.

In the above description, only the first pressing member 50 is movable. However, even if only the second pressing member 60 is movable, both the first pressing member 50 and the second pressing member 60 are movable. It is good also as a structure.
Further, although the concentration measuring device 37 has been described as being disposed in the liquid developer transport path 38, it may be disposed in the recovered developer transport path 31 or the new developer transport path 29, or the carrier liquid transport path 33. Or, each branch path 33C, 33M, 33Y may be arranged.

The mixing pot 26 and the recovery pot 28 are provided with a circulation path for allowing the liquid developer to flow out of the container and returning the liquid developer to the container, and a density measuring device 37 is disposed in the circulation path. Also good.
In addition, various modifications can be made within the scope of the claims.

1 is a schematic diagram showing a configuration of a wet image forming apparatus according to an embodiment of the present invention. FIG. 6 is a perspective view showing a state in which a density measuring device is attached to a liquid developer conveyance path. It is the schematic diagram seen from the arrow III direction of FIG. (A) shows a state where the first pressing member is in the release position, and (b) shows a state where the first pressing member is in the measurement position. It is a figure which shows the relationship between the particle concentration of a liquid developer, and the transmittance | permeability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wet image forming apparatus 2C, 2M, 2Y Photosensitive drum 6C, 6M, 6Y Liquid developing device 11, 12, 13 Development forming mechanism 37 Density measuring device 38 Liquid developer conveyance path (conveyance path)
40 Transparent tube (tube)
50 First pressing member (first member)
51 1st press surface 60 2nd press member (2nd member)
61 Second pressing surface 70 Displacement device T Liquid developer

Claims (5)

A tube that is provided as a transport path for the liquid developer, and has translucency, flexibility, and resilience;
A pair of members disposed across the tube, the first member having a transparent first pressing surface facing the tube, and the transparent facing the tube and the first pressing surface and disposed in parallel with the first pressing surface A pressing member comprising a second member having a second pressing surface;
A light-emitting element embedded in the first member and radiating light in a predetermined wavelength range outward from the first pressing surface;
A light receiving element embedded in the second member for receiving light that passes through the tube and reaches the second pressing surface;
It is connected to the pressing member, and includes a measuring position where the pressing member presses the tube in a predetermined state, and a displacement device that displaces the releasing position where the pressing member does not press the tube. Liquid developer concentration measurement device. A tube that is provided as a transport path for the liquid developer, and has translucency, flexibility, and resilience;
A pair of members disposed across the tube, the first member having a transparent first pressing surface facing the tube, and the mirror surface facing the tube and the first pressing surface and disposed in parallel with the first pressing surface A pressing member comprising a second member having a second pressing surface constituted by:
A light-emitting element embedded in the first member and radiating light in a predetermined wavelength range outward from the first pressing surface;
A light receiving element embedded in the first member, for receiving reflected light that passes through the tube, is reflected by the second pressing surface, and returns to the first member;
A liquid developer, comprising: a measuring device connected to a pressing member, wherein the pressing member presses the tube in a predetermined state; and a displacement device that displaces the tube to a release position that does not press the tube. Concentration measuring device.   3. The liquid developer concentration measuring apparatus according to claim 1, wherein the tube is made of a transparent soft tube and has a thickness of 1 mm or less.   The distance between the first pressing surface and the second pressing surface at the measurement position is maintained at an interval of 1/2 or more of the outer diameter of the tube. The liquid developer concentration measuring apparatus as described. 5. A wet image forming apparatus comprising: a liquid developer concentration measuring device according to claim 1 in a liquid developer conveyance path that connects a container for storing a liquid developer and the container.

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