JP5364646B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for applying an electric field of a proper intensity to a development roller. <P>SOLUTION: A color printer 1 includes: a charging part 971a for continuously applying a prescribed constant applied voltage to a liquid developer constituting a first developer film to be formed on the surface of a development roller 91a supplying a liquid developer to a photosensitive drum 10a; a surface potential measurement part 700a for measuring a surface potential value of a second developer film to be formed on the surface of the photosensitive drum 10a with the use of the liquid developer supplied from the development roller 91a; and a constant applied voltage setting part 510 for setting a constant applied voltage. The constant applied voltage setting part 510 sets the constant applied voltage, based on the surface potential value of the second developer film which is measured by the surface potential measurement part 700a in a state where a voltage is being applied by the charging part 971a while changing the voltage value. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a printer, there is a wet type image forming apparatus including an image carrier capable of carrying a toner image and a developing device capable of supplying a liquid developer to the image carrier. Normally, a wet image forming apparatus is constituted by a pumping roller that pumps up a liquid developer stored in a liquid developer storage unit, and a developer supply roller that is disposed opposite to the pumping roller and has a developer film formed on the surface thereof. And a developing roller that holds the developer film formed by transferring the developer film formed on the surface of the developer supply roller on the surface.

Here, in order to obtain a high-quality image, an image having an electric field applying roller that forms a liquid toner layer in which charged toner particles are aggregated by applying an electric field to the liquid developer attached to the surface of the developing roller. A forming apparatus has been proposed.
However, the aggregation state of the toner particles contained in the liquid developer is greatly influenced by the strength of the applied electric field. Specifically, the toner image is blurred when the strength of the electric field applied by the electric field application roller is weak, and conversely, when the strength of the applied electric field is strong, the adhesion to the developing roller becomes strong. There was a problem that it caused cleaning failure too much.

  On the other hand, a compression member that applies an electric field to the liquid developer supplied to the developing roller, a photoconductor that is developed with the liquid developer to which an electric field is applied by the compression member, and development when the photoconductor is developed A means for measuring the developing current flowing between the roller and the photosensitive member, and a control means for controlling the strength of the electric field applied to the compression member so that the measurement result measured by the means for measuring the developing current becomes a specified value. Has been proposed (for example, see Patent Document 1).

JP 2008-170601 A

However, in the image forming apparatus of Patent Document 1, there is a case where the intensity of the applied electric field is not appropriate as a result of controlling the measurement result to a specified value due to a change in environmental conditions.
Further, in the image forming apparatus of Patent Document 1, it is difficult to control the electric field to an appropriate electric field based on other factors such as the type of liquid developer.

  An object of the present invention is to provide an image forming apparatus capable of applying an electric field having an appropriate strength to a developing roller.

  The present invention is an image carrier capable of carrying a toner image based on the electrostatic latent image while an electrostatic latent image is formed on the surface, and a developing device for supplying a liquid developer to the image carrier, A developer supply unit that supplies the liquid developer, a developer storage unit that stores the liquid developer supplied by the developer supply unit, and a developer pump that pumps up the liquid developer stored in the developer storage unit And a liquid developer pumped up by the developer pumping unit to form a first developer film on the surface of the image carrier. A developing device that includes a developing roller that supplies a liquid developer to the image carrier in a region facing the image carrier, and a liquid developer that constitutes the first developer film formed on a surface of the developing roller. Electric field applied to the agent A charging unit capable of changing an electric field to be applied and capable of continuously applying a predetermined constant applied electric field, and a liquid developer supplied from the developing roller. A surface potential measuring unit for measuring a surface potential value of a second developer film formed on the surface, and a constant applied electric field setting unit for setting the constant applied electric field, wherein the first developer is changed while changing the electric field value. Controlling the charging unit to apply an electric field to the film, and measuring the surface potential value of the second developer film in a state where the charging unit applies an electric field while changing the electric field value. The present invention relates to an image forming apparatus comprising: a constant applied electric field setting unit that controls a measuring unit and sets the constant applied electric field based on the surface potential value measured by the surface potential measuring unit.

  In the image forming apparatus, it is preferable that the constant applied electric field setting unit sets an applied electric field corresponding to the highest value of the measured surface potential value as the constant applied electric field.

  The image forming apparatus is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred. The applied electric field setting unit preferably starts control of the charging unit and the surface potential measuring unit in the non-printing operation state.

  The image forming apparatus includes an environmental sensor that measures an environmental condition, and an environmental change determination unit that determines whether or not the change in the environmental condition exceeds a predetermined range based on a measurement result by the environmental sensor. The constant applied electric field setting unit preferably starts control of the charging unit and the surface potential measurement unit when the environmental change determination unit determines that the change in the environmental condition exceeds a predetermined range.

  Further, in the image forming apparatus, a temperature sensor, a viscosity detection unit that detects the viscosity of the liquid developer based on a measurement result by the temperature sensor, and a change in viscosity based on the viscosity detected by the viscosity detection unit. A constant change electric field setting unit that determines whether or not the change in viscosity exceeds a predetermined range by the viscosity change determination unit. It is preferable to start control of the unit and the surface potential measuring unit.

  The present invention also relates to an image carrier capable of carrying a toner image based on the electrostatic latent image while an electrostatic latent image is formed on the surface, and a developing device for supplying a liquid developer to the image carrier. A developer supply unit that supplies the liquid developer, a developer storage unit that stores the liquid developer supplied by the developer supply unit, and a development that pumps up the liquid developer stored in the developer storage unit. A developer pumping unit is disposed opposite to the image carrier so as to be rotatable about a rotation axis, and the liquid developer pumped up by the developer pumping unit is supplied to form a first developer film on the surface. And a developing device having a developing roller for supplying a liquid developer to the image carrier in a region facing the image carrier, and the first developer film formed on the surface of the developer roller. Voltage against liquid developer A charging unit that can be applied, the voltage to be applied can be changed, and a charging unit capable of continuously applying a predetermined constant applied voltage, and the image carrier by a liquid developer supplied from the developing roller A surface potential measuring unit for measuring a surface potential value of a second developer film formed on the surface of the first developer film, and a constant applied voltage setting unit for setting the constant applied voltage, wherein the first development is performed while changing the voltage value. Controlling the charging unit to apply a voltage to the agent film, and measuring the surface potential value of the second developer film in a state where the charging unit is applying a voltage while changing the voltage value. The present invention relates to an image forming apparatus comprising: a constant applied voltage setting unit that controls a potential measuring unit and sets the constant applied voltage based on the surface potential value measured by the surface potential measuring unit.

  In the image forming apparatus, it is preferable that the constant applied voltage setting unit sets an applied electric field corresponding to the highest value of the measured surface potential value to the constant applied voltage.

  The image forming apparatus is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred. It is preferable that the applied voltage setting unit starts control of the charging unit and the surface potential measuring unit in the non-printing operation state.

  The image forming apparatus includes an environmental sensor that measures an environmental condition, and an environmental change determination unit that determines whether or not the change in the environmental condition exceeds a predetermined range based on a measurement result by the environmental sensor. The constant applied voltage setting unit preferably starts control of the charging unit and the surface potential measurement unit when the environmental change determination unit determines that the change in the environmental condition exceeds a predetermined range.

  Further, in the image forming apparatus, a temperature sensor, a viscosity detection unit that detects the viscosity of the liquid developer based on a measurement result by the temperature sensor, and a change in viscosity based on the viscosity detected by the viscosity detection unit. A viscosity change determination unit that determines whether or not the viscosity change exceeds a predetermined range, and the constant applied voltage setting unit is configured to charge the charging when the viscosity change determination unit determines that the viscosity change exceeds a predetermined range. It is preferable to start control of the unit and the surface potential measuring unit.

  The present invention also relates to an image carrier capable of carrying a toner image based on the electrostatic latent image while an electrostatic latent image is formed on the surface, and a developing device for supplying a liquid developer to the image carrier. A developer supply unit that supplies the liquid developer, a developer storage unit that stores the liquid developer supplied by the developer supply unit, and a development that pumps up the liquid developer stored in the developer storage unit. A developer pumping unit is disposed opposite to the image carrier so as to be rotatable about a rotation axis, and the liquid developer pumped up by the developer pumping unit is supplied to form a first developer film on the surface. And a developing device having a developing roller for supplying a liquid developer to the image carrier in a region facing the image carrier, and the first developer film formed on the surface of the developer roller. Current against liquid developer A charging unit that can be applied, wherein a current to be applied can be changed, and a charging unit capable of continuously applying a predetermined constant applied current, and the image carrier by a liquid developer supplied from the developing roller A surface potential measuring unit that measures a surface potential value of a second developer film formed on the surface of the first developer film, and a constant applied current setting unit that sets the constant applied current, wherein the first development is performed while changing the current value. Controlling the charging unit to apply a current to the agent film, and measuring the surface potential value of the second developer film in a state where the charging unit is applying a current while changing a current value. The present invention relates to an image forming apparatus comprising: a constant applied current setting unit that controls a potential measuring unit and sets the constant applied current based on the surface potential value measured by the surface potential measuring unit.

  In the image forming apparatus, it is preferable that the constant applied current setting unit sets the applied current corresponding to the highest value of the measured surface potential value as the constant applied current.

  The image forming apparatus is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred. The applied current setting unit preferably starts control of the charging unit and the surface potential measuring unit in the non-printing operation state.

  The image forming apparatus includes an environmental sensor that measures an environmental condition, and an environmental change determination unit that determines whether or not the change in the environmental condition exceeds a predetermined range based on a measurement result by the environmental sensor. The constant applied current setting unit preferably starts control of the charging unit and the surface potential measurement unit when the environmental change determination unit determines that the change in the environmental condition exceeds a predetermined range.

  Further, in the image forming apparatus, a temperature sensor, a viscosity detection unit that detects the viscosity of the liquid developer based on a measurement result by the temperature sensor, and a change in viscosity based on the viscosity detected by the viscosity detection unit. A viscosity change determination unit for determining whether or not the viscosity change exceeds a predetermined range, and the constant applied current setting unit determines that the change in viscosity exceeds the predetermined range by the viscosity change determination unit. It is preferable to start control of the unit and the surface potential measuring unit.

  According to the present invention, it is possible to provide an image forming apparatus capable of applying an electric field having an appropriate strength to the developing roller.

2 is an overall view for explaining each component of the color printer 1. FIG. It is a schematic diagram for demonstrating the structure of liquid developer circulation device LB. It is sectional drawing explaining the structure of the developing device 9a. 2 is a block diagram illustrating a configuration in the color printer 1. FIG. 5 is a graph showing a change curve of a surface potential value when a surface potential of a second developer film is measured in a state where a voltage is applied to the first developer film while changing a voltage value. FIG. 5 is a flowchart for explaining an initial setting operation of a constant applied voltage in the color printer 1. FIG. 5 is a flowchart for explaining a constant applied voltage update operation in the color printer 1.

The best mode for carrying out the present invention will be described below with reference to the drawings.
First, the overall configuration of a color printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is an overall view for explaining each component of the color printer 1.
As shown in FIG. 1, the color printer 1 includes an image forming unit 2, a paper storage unit 3, a secondary transfer unit 4, a fixing unit 5, a paper transport unit 6, and a paper discharge unit 7. . In addition, the color printer 1 includes a temperature sensor 8 as an environmental sensor that measures an environmental condition in a housing 100 that is an apparatus main body.

  The image forming unit 2 is of a tandem type that forms a toner image based on image data. The paper storage unit 3 stores paper T, which is an example of a transfer material. The secondary transfer unit 4 transfers the toner image formed by the image forming unit 2 onto the paper T (front surface). The fixing unit 5 fixes the toner image transferred onto the paper T onto the paper T (front surface). The paper transport unit 6 transports the paper T from the paper storage unit 3 to the paper discharge unit 7. The paper discharge unit 7 discharges (discharges) the paper T conveyed by the paper conveyance unit 6.

The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22, and a plurality of image forming units FB, FY, FC, and FM. The image forming unit 2 is based on image data (such as an image forming instruction, image information, and number information) input from an external device (for example, a PC (Personal computer)) via the input receiving unit 400 (see FIG. 3). Thus, a toner image is formed. The image data includes an image formation instruction that is an instruction to form a predetermined toner image on each of the photosensitive drums 10a, 10b, 10c, and 10d as image carriers described later with respect to the image forming unit 2, and image information and the number of sheets related to the toner image. Includes information.
The image forming unit 2 is controlled by an image forming control unit 410 (see FIG. 3).

The image formation control unit 410 controls the image formation unit 2 to form a toner image on the photosensitive drums 10a, 10b, 10c, and 10d as image carriers to be described later.
When image data is received by the input receiving unit 400, the image forming control unit 410 causes the image forming unit 2 to form a toner image on each of the photosensitive drums 10a, 10b, 10c, and 10d as image carriers to be described later. Control.

The intermediate transfer belt 21 is an endless belt member having conductivity.
The intermediate transfer belt 21 is wider than the width of the largest sheet that can be used in the color printer 1. Here, the “width” refers to the length in the direction perpendicular to the paper transport direction.
The intermediate transfer belt 21 is stretched and disposed on a driving roller 41, a driven roller 23, and a tension roller 24 that are disposed at predetermined positions.
The intermediate transfer belt 21 is driven to circulate clockwise (in FIG. 1) as indicated by an arrow. Specifically, the intermediate transfer belt 21 is rotationally driven in the arrow direction (ring direction) by a driving roller 41 rotated by a rotational driving force transmitted from a driving motor (not shown). The driven roller 23 and the tension roller 24 are driven to rotate by the intermediate transfer belt 21 that is driven to rotate. The intermediate transfer belt 21 is rotationally driven in a state where an appropriate tension is applied so as not to be loosened by the tension roller 24.
Hereinafter, the surface facing the outside of the intermediate transfer belt 21 is referred to as a front surface, and the other surface is referred to as a back surface.

  The cleaning unit 22 includes a cleaning roller 22a and a cleaning blade 22b. The cleaning unit 22 cleans the intermediate transfer belt 21.

Each of the image forming units FB, FY, FC, FM is disposed in the vicinity of the intermediate transfer belt 21. The image forming units FB, FY, FC, and FM are arranged side by side in the horizontal direction. The image forming units FB, FY, FC, and FM are arranged side by side between the cleaning unit 22 and the secondary transfer unit 4 in the horizontal direction. The image forming units FB, FY, FC, FM are arranged in the order of FB, FY, FC, FM from the left in FIG.
The image forming units FB, FY, FM, and FC are units corresponding to the respective colors of black (Bk), yellow (Y), cyan (C), and magenta (M).
Note that the arrangement order of the image forming units FB, FY, FC, and FM is not limited to the above, but considering the influence on the image (image transferred onto the paper T) due to the color mixture of each color, the arrangement order described above. Is preferred.

Further, corresponding to each of the image forming units FB, FY, FC, FM, toner tanks TB, TY, TC, TM constituting the liquid developer circulating devices LB, LY, LC, LM, which will be described later, and a main carrier tank MT Is provided. These are tanks used for supply and recovery of the liquid developer of each color.
The liquid developer circulating devices LB, LY, LC, and LM will be described later.

  Each of the image forming units FB, FY, FC, and FM includes photosensitive drums 10a, 10b, 10c, and 10d, charging devices 11a, 11b, 11c, and 11d, exposure devices 12a, 12b, 12c, and 12d, and a developing device 9a. 9b, 9c, 9d, primary transfer rollers 20a, 20b, 20c, 20d, cleaning devices 26a, 26b, 26c, 26d, static eliminators 13a, 13b, 13c, 13d, and carrier liquid removal rollers 30a, 30b, 30c, 30d.

  Each of the photosensitive drums 10a, 10b, 10c, and 10d is a cylindrical member that can carry a toner image charged on its surface (charged to a positive polarity in this embodiment). Each of the photosensitive drums 10a, 10b, 10c, and 10d is disposed to be able to rotate counterclockwise in FIG. 1 as indicated by an arrow.

  Each of the charging devices 11a, 11b, 11c, and 11d is a device that uniformly charges the surface of each of the photosensitive drums 10a, 10b, 10c, and 10d to a predetermined polarity and potential.

  Each of the exposure apparatuses 12a, 12b, 12c, and 12d includes a light source unit (not shown) (for example, an LED (Light-Emitting Diode)). Each of the exposure apparatuses 12a, 12b, 12c, and 12d is uniform in a predetermined polarity and potential based on image data input from an external device (for example, a PC or the like) via the input receiving unit 400 (see FIG. 3). The surface of each of the photosensitive drums 10a, 10b, 10c, and 10d charged with a light is irradiated with light. As a result, the charge at the exposed portion is removed, and electrostatic latent images are formed on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d.

The developing devices 9a, 9b, 9c, and 9d are respectively liquid developers GB and GY that contain toner and a carrier liquid so as to face the electrostatic latent images formed on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d, respectively. , GC, GM. Thus, each of the developing devices 9a, 9b, 9c, and 9d attaches toner of each color to the electrostatic latent image and develops the electrostatic latent image as a toner image.
The developing device will be described in detail later.

  The primary transfer rollers 20a, 20b, 20c, and 20d are disposed on the back surface of the intermediate transfer belt 21 corresponding to the photosensitive drums 10a, 10b, 10c, and 10d, respectively. The primary transfer rollers 20a, 20b, 20c, and 20d are arranged to face the photosensitive drums 10a, 10b, 10c, and 10d, respectively, with the intermediate transfer belt 21 interposed therebetween.

  The primary transfer rollers 20a, 20b, 20c, and 20d are each applied with a voltage having a polarity (minus in this embodiment) opposite to that of the toner constituting the toner image by a power source (not shown). That is, each of the primary transfer rollers 20 a, 20 b, 20 c, and 20 d applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt 21 and its periphery.

  Each of the cleaning devices 26a, 26b, 26c, and 26d includes cleaning blades 27a, 27b, 27c, and 27d, and conveying screws 28a, 28b, 28c, and 28d. Each of the cleaning devices 26a, 26b, 26c, and 26d is a device for removing the liquid developer remaining on the photosensitive drums 10a, 10b, 10c, and 10d without being transferred to the intermediate transfer belt 21.

  Each of the cleaning blades 27a, 27b, 27c, and 27d is a plate-like member that extends in the rotation axis direction of each of the photosensitive drums 10a, 10b, 10c, and 10d. The cleaning blades 27a, 27b, 27c, and 27d are members for scraping off the liquid developer remaining on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d, respectively. The cleaning blades 27a, 27b, 27c, and 27d are arranged so that the tips thereof are in contact (sliding contact) with the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d, respectively. Each of the cleaning blades 27a, 27b, 27c, and 27d scrapes off the liquid developer remaining on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d as the photosensitive drums 10a, 10b, 10c, and 10d rotate. .

  The conveying screws 28a, 28b, 28c, and 28d are disposed inside the cleaning devices 26a, 26b, 26c, and 26d, respectively. The conveying screws 28a, 28b, 28c, and 28d are scraped off by the cleaning blades 27a, 27b, 27c, and 27d, respectively, and the liquid developer stored in the cleaning devices 26a, 26b, 26c, and 26d is first recovered. It conveys to container 81a (refer FIG. 2), 81b, 81c, 81d, respectively. Further, the conveying screws 28a, 28b, 28c, and 28d are removed from the intermediate transfer belt 21 by carrier liquid removing rollers 30a, 30b, 30c, and 30d, which will be described later, and are respectively disposed inside the cleaning devices 26a, 26b, 26c, and 26d. The accommodated carrier liquid is also transferred to the first recovery containers 81a (see FIG. 2), 81b, 81c, and 81d.

  Each of the static eliminating devices 13a, 13b, 13c, and 13d has a light source for static elimination (not shown). Each of the static elimination devices 13a, 13b, 13c, and 13d performs static elimination processing on the surface of each of the photosensitive drums 10a, 10b, 10c, and 10d with light from the light source. The neutralization devices 13a, 13b, 13c, and 13d respectively perform neutralization processing on portions where the liquid developer has been removed from the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d by the cleaning blades 27a, 27b, 27c, and 27d, respectively. do.

Each of the carrier liquid removal rollers 30a, 30b, 30c, and 30d is a substantially columnar member that is rotatably disposed around rotation axes parallel to the rotation axes of the photosensitive drums 10a, 10b, 10c, and 10d. . The carrier liquid removal rollers 30 a, 30 b, 30 c, and 30 d are members that remove the carrier liquid from the surface of the intermediate transfer belt 21.
Each of the carrier liquid removal rollers 30a, 30b, 30c, and 30d is disposed to face the surface of each of the photosensitive drums 10a, 10b, 10c, and 10d. Each of the carrier liquid removal rollers 30a, 30b, 30c, and 30d is located at each of the photosensitive drums 10a, 10b, 10c, and 10d rather than a position where the photosensitive drums 10a, 10b, 10c, and 10d are in contact with the intermediate transfer belt 21. The photoconductor drums 10a, 10b, 10c, and 10d are arranged to face each other on the downstream side in the rotation direction.
Each of the carrier liquid removal rollers 30a, 30b, 30c, and 30d rotates in the same direction as each of the photosensitive drums 10a, 10b, 10c, and 10d when viewed from a predetermined direction. The carrier liquids removed by the carrier liquid removal rollers 30a, 30b, 30c, and 30d are accommodated in the cleaning devices 26a, 26b, 26c, and 26d.

  The paper storage unit 3 is disposed at the lower part in the vertical direction of the color printer 1. The paper storage unit 3 supplies a paper feed cassette 31 that stores paper T, a paper feed roller 32 that supplies the paper T to a paper transport unit 6 described later, and supplies the paper T to the paper transport unit 6 in a state where a plurality of papers T overlap. And a separation roller pair 33 that suppresses this.

  The secondary transfer unit 4 includes a drive roller 41 that drives the intermediate transfer belt 21 and a secondary transfer roller 42. The secondary transfer roller 42 is arranged to be pressed toward the drive roller 41 with the intermediate transfer belt 21 interposed therebetween. The secondary transfer unit 4 transfers the toner image formed on the surface (surface) of the intermediate transfer belt 21 onto the paper T. The secondary transfer unit 4 constitutes a transfer device that transfers the toner image onto the paper T together with the primary transfer rollers 20a, 20b, 20c, and 20d described above.

  The fixing unit 5 includes a heating roller 51 and a pressure roller 52. The pressure roller 52 is disposed so as to face the heating roller 51 and press the heating roller 51. The fixing unit 5 is a part (device) that fixes the toner image transferred by the secondary transfer unit 4 to the paper T. The fixing unit 5 is disposed downstream of the secondary transfer unit 4 in the transport direction of the paper T.

  The paper transport unit 6 includes a plurality of transport roller pairs 74 and a registration roller pair 75. The paper transport unit 6 is a part that transports the paper T supplied from the paper storage unit 3 to the paper discharge unit 7 via the secondary transfer unit 4 and the fixing unit 5. In FIG. 1, only a pair of transport roller pairs 74 is shown, and the other transport roller pairs are not shown.

  The paper discharge unit 7 includes a plurality of discharge roller pairs 71 and a discharge tray 72 provided on the upper surface of the color printer 1. The paper discharge unit 7 is a portion where the toner image is transferred by the secondary transfer unit 4 and the paper T on which the toner image is fixed on one or both sides by the fixing unit 5 is discharged. In FIG. 1, only a pair of discharge roller pair 71 is shown, and the other discharge roller pairs are not shown.

Next, the configuration of the color printer 1 will be described with reference to FIGS. 2 and 4 focusing on the configuration of the developing device and the liquid developer circulating device.
FIG. 2 is a schematic diagram illustrating the configuration of the liquid developer circulating device LB. FIG. 3 is a cross-sectional view illustrating the configuration of the developing device 9a. FIG. 4 is a block diagram illustrating a configuration in the color printer 1.

  As shown in FIGS. 2 to 4, the color printer 1 includes developing devices 9a, 9b, 9c, and 9d, charging units 97a, 97b, 97c, and 97d, surface potential measuring units 700a, 700b, 700c, and 700d, It has a temperature sensor 8 as an environmental sensor, an input receiving unit 400, an image formation control unit 410, a CPU 500, and a memory 600.

  First, the configuration of the developing devices 9a, 9b, 9c, and 9d will be described. Here, the developing device 9a will be described in detail, and description of other developing devices 9b, 9c, and 9d having the same configuration will be omitted. Similarly, with respect to the charging unit and the surface potential measuring unit, the charging unit 97a and the surface potential measuring unit 700a will be described in detail, and the description of other components having the same configuration will be omitted.

2 and 3, the developing device 9a includes a developing roller 91a, a supply roller 92a and a pumping roller 93a constituting a developer pumping unit, a developer supplying device 94a as a developer supplying unit, and a developing unit. A developing container 95a serving as a developer storage unit and a developing roller cleaning device 96a serving as a developer removing unit are provided.
The developing device 9a is a device for supplying a liquid developer to the photosensitive drum 10a.

The developing roller 91a is a cylindrical member disposed to face the photosensitive drum 10a. The developing roller 91a has an elastic portion that is disposed on the outer surface side and forms the surface. The developing roller 91a is rotated in the arrow direction (clockwise) in FIG.
The developing roller 91a is disposed so as to come into contact with the photosensitive drum 10a with a predetermined pressure. As a result, a contact portion NC (a facing region) is formed at the contact portion between the photosensitive drum 10a and the developing roller 91a.

Further, the developing roller 91a is disposed so as to face and contact the supply roller 92a.
The liquid developer pumped up by the developer pumping unit is supplied to the developing roller 91a. Specifically, in the developing roller 91a, the first developer film formed on the surface of the supply roller 92a is transferred to the elastic portion of the surface, and the transferred first developer film is transferred to the surface of the elastic portion. Hold.
The developing roller 91a supplies a liquid developer to the photosensitive drum 10a at a contact portion NC as a region facing the photosensitive drum 10a to form a second developer film on the surface of the photosensitive drum 10a.

The supply roller 92a constitutes a developer pumping unit.
The supply roller 92a is disposed opposite to the developing roller 91a. The supply roller 92a is disposed on the lower side in the vertical direction of the developing roller 91a. Further, the supply roller 92a is arranged such that the rotation shaft is displaced in the horizontal direction with respect to the rotation shaft of the developing roller 91a. The supply roller 92a is disposed between the developing roller 91a and the drawing roller 93a.

The supply roller 92a is a roller member that supplies the liquid developer to the development roller 91a.
The supply roller 92a has a role as a member called a so-called anilox roller, and a spiral groove is formed on the surface. The supply roller 92a is configured to be able to hold the liquid developer on the surface when the liquid developer flows into the spiral groove. Here, the liquid developer held on the supply roller 92a (front surface) is moved from the one end side in the axial direction (the front side in FIG. 3) to the other end side (the back side in FIG. 3) as the supply roller 92a rotates. Side).

  In the vicinity of the supply roller 92a, a supply roller blade member 921a is disposed so that the tip is in contact with the surface of the supply roller 92a. The supply roller blade member 921a regulates the layer thickness of the liquid developer on the supply roller 92a.

  The supply roller 92a is rotated in the direction of the arrow (clockwise) in FIG. That is, at the nip portion NA where the developing roller 91a and the supply roller 92a abut, the surface of the developing roller 91a moves in the opposite direction to the surface of the supply roller 92a. As a result, the liquid developer held on the surface of the supply roller 92a is transferred to the surface of the developing roller 91a.

  The scooping roller 93a is disposed in a state where the lower part thereof is immersed in the liquid developer GB stored in the developing container 95a. The scooping roller 93a is disposed in contact with the supply roller 92a. The drawing roller 93a is a member shorter than the supply roller 92a in the axial direction. The pumping roller 93a is disposed on one end side in the axial direction (front side in FIG. 3). The pumping roller 93a is disposed on the lower side in the vertical direction of the supply roller 92a. In addition, the pumping roller 93a is arranged such that the rotation shaft is displaced in the horizontal direction with respect to the rotation shaft of the supply roller 92a.

  The drawing roller 93a is rotated in the direction of the arrow (counterclockwise) in FIG. That is, in the nip portion NB where the supply roller 92a and the pumping roller 93a contact each other, the surface of the supply roller 92a moves in the same direction as the surface of the pumping roller 93a. As a result, the liquid developer stored in the nip NB is easily supplied to the supply roller 92a (a developer film is easily formed on the surface of the supply roller 92a).

  The scooping roller 93a can support the liquid developer in the vicinity of the nip NB that contacts the supply roller 92a. The scooping roller 93a is arranged so that the rotation shaft is displaced in the horizontal direction with respect to the rotation shaft of the supply roller 92a, thereby allowing the liquid developer to be easily stored in the vicinity of the nip portion NB.

The developer supply device 94a is a device for supplying the liquid developer whose density has been adjusted to the developing container 95a.
The developer supply device 94a includes a plurality of developer supply nozzles 941a arranged at equal intervals in the axial direction of the supply roller 92a, and a pump P4a described later.

  The developer supply nozzle 941a is connected to the reserve tank 87a of the liquid developer circulation device LB via the flow path R7a, and receives supply of the liquid developer from the reserve tank 87a (see FIG. 2). The developer supply nozzle 941a supplies a liquid developer to the developing container 95a. The amount of the liquid developer supplied by the developer supply nozzle 941a is adjusted by the pump P4a. The pump P4a is controlled by a supply control unit (not shown).

  The liquid developer supplied from the developer supply device 94a is stored in the storage unit 951a of the developing container 95a. The liquid developer stored in the storage portion 951a of the developing container 95a is pumped up by the pumping roller 93a and transferred to the surface (spiral groove) of the supply roller 92a.

  Further, at the nip portion NA where the developing roller 91a and the supply roller 92a abut, the surface of the developing roller 91a moves in the opposite direction to the surface of the supply roller 92a. As a result, the liquid developer (developer film) transferred and held on the surface of the supply roller 92a is transferred to the surface of the developing roller 91a. Here, since the film thickness of the developer film of the supply roller 92a is regulated within a predetermined range by the supply roller blade member 921a, the film thickness of the developer film formed on the surface of the developing roller 91a is also maintained within the predetermined range. .

The developing container 95a includes a scooping roller 93a, a supply roller 92a, a developer supplying device 94a, a developing roller 91a, a developing roller cleaning device 96a, a charging unit 97a (charger 971a), and a supply roller blade member 921a. Is a container having a reservoir 951a capable of containing a liquid developer therein.
The developing container 95a contains the liquid developer supplied by the developer supply device 94a. Specifically, the reservoir 951a in the developing container 95a accommodates the liquid developer supplied by the developer supply device 94a.

  The developing roller cleaning device 96a includes a developer collecting roller 963a, a collecting roller scraping blade 964a, a scraping blade 961a, a developer collecting unit 962a, and a discharge member 965a. The developing roller cleaning device 96a is arranged to be supported by the developing container 95a.

The developing roller cleaning device 96a (developer collecting roller 963a, scraping blade 961a) is in contact with a position on the surface of the developing roller 91a and downstream of the contact portion NC in the rotation direction (arrow direction) of the developing roller 91a. Be placed.
The developing roller cleaning device 96a is a device that removes (cleans) the liquid developer remaining on the surface of the developing roller 91a without being supplied to the photosensitive drum 10a.

The developer collecting roller 963a is disposed in contact with the developing roller 91a so as to face the developing roller 91a. The developer recovery roller 963a is disposed on the surface of the developing roller 91a in contact with a position downstream of the contact portion NC in the rotation direction (arrow direction) of the developing roller 91a. The developer recovery roller 963a is a member that recovers the liquid developer remaining on the development roller 91a. The developer recovery roller 963a is a member that recovers the liquid developer remaining on the developing roller 91a without being transferred to the developing roller 91a at the contact portion NC.
The collection roller scraping blade 964a is a member that scrapes off the liquid developer adhering to the developer collection roller 963a, and the tip thereof is disposed in contact with the developer collection roller 963a.

  The scraping blade 961a is a plate-like member disposed to face a predetermined position on the downstream side in the rotation direction of the developing roller 91a with respect to the developer collecting roller 963a. The scraping blade 961a is disposed on the surface of the developing roller 91a in contact with a position downstream of the contact portion NC in the rotation direction (arrow direction) of the developing roller 91a. The scraping blade 961a is disposed so that the tip thereof is in contact with the developing roller 91a. The scraping blade 961a is a member for scraping off the liquid developer on the developing roller 91a (surface). The scraping blade 961a is a member for scraping off the liquid developer that is not transferred to the developing roller 91a but remains on the developing roller 91a at the contact portion NC and is not collected by the developer collecting roller 963a. It is.

  The developer recovery unit 962a has an internal space for recovering the liquid developer scraped by the scraping blade 961a. The internal space in the developer recovery unit 962a is connected to the second recovery container 83a by a flow path R1a (see FIG. 2).

  The discharge member 965a is a screw-like member that conveys the liquid developer recovered by the developer recovery unit 962a to the flow path R1a connected to the second recovery container 83a (see FIG. 2).

As shown in FIGS. 2 and 3, the charging unit 97a includes a charger 971a and a charging control unit 972a.
The charger 971a is disposed to face the developing roller 91a. The charger 971a is disposed in the vicinity of the developing roller 91a. The charger 971a is upstream of the contact portion NC between the developing roller 91a and the photosensitive drum 10a in the rotation direction of the developing roller 91a, and is downstream of the nip portion NA between the developing roller 91a and the supply roller 92a. It is arranged to face the side part. The charger 971a is disposed opposite to the developing roller 91a between the nip portion NA and the contact portion NC in the rotation direction of the developing roller 91a.

  The charger 971a applies a voltage as an electric field to the liquid developer that forms the developer film formed on the surface (surface) of the developing roller 91a. The charger 971a imparts a charge to the liquid developer constituting the developer film, for example, by corona discharge.

The voltage applied to the charger 971a is controlled by the charge controller 972a. The charger 971a is configured to be able to change the voltage to be applied based on the control from the charge controller 972a.
The charger 971a is configured to be able to maintain a constant voltage to be applied, and is configured to be able to change the voltage to be applied continuously or intermittently.

The charging control unit 972a controls the applied voltage in the charger 971a.
The charging controller 972a controls the charger 971a so as to continuously apply a predetermined constant applied voltage to the developing roller 91a. Specifically, the charging control unit 972a applies a predetermined constant applied voltage to the developing roller 91a based on the constant applied voltage value stored in the constant applied voltage value storage unit 601 in the memory 600. 971a is controlled. Specifically, the charging control unit 972a continues a predetermined constant applied voltage based on the constant applied voltage value set by the constant applied voltage setting unit 510 described later and stored in the constant applied voltage value storage unit 601 in the memory 600. Thus, the charger 971a is controlled so as to be applied to the developing roller 91a.

  Further, the charging control unit 972a controls the charger 971a so as to change the applied voltage continuously or intermittently. Specifically, the charging control unit 972a continuously increases the applied voltage value from a predetermined first voltage value to a predetermined second voltage value based on an instruction from a constant applied voltage setting unit 510 described later (or The charger 971a is configured to be controllable so as to be reduced.

The surface potential measurement unit 700a includes a surface potential measurement device 701a (surface potential sensor) and a surface potential measurement control unit 702a.
The surface potential measuring unit 700a measures the surface potential value of the second developer film formed on the surface of the photosensitive drum 10a.
The surface potential measuring device 701a is disposed to face the photosensitive drum 10a. The surface potential measuring device 701a is disposed in the vicinity of the photosensitive drum 10a. The surface potential measuring device 701a is disposed opposite to a portion on the downstream side of the nip NA that is a contact portion between the photosensitive drum 10a and the developing roller 91a in the rotation direction of the photosensitive drum 10a.

The surface potential measuring device 701a measures the surface potential value of the second developer film formed on the surface of the photosensitive drum 10a based on an instruction from the surface potential measurement control unit 702a.
The surface potential measuring device 701a outputs information on the measured surface potential value to the constant applied voltage setting unit 510 in the CPU described later.

The surface potential measurement control unit 702a controls the surface potential measurement device 701a. The surface potential measurement control unit 702a controls the surface potential measuring device 701a so as to start or stop the measurement of the surface potential value in the second developer film formed on the surface of the photosensitive drum 10a.
The surface potential measurement control unit 702a starts or stops the measurement of the surface potential value of the second developer film formed on the surface of the photosensitive drum 10a based on an instruction from the constant applied voltage setting unit 510. The measuring device 701a is controlled.

  The temperature sensor 8 (environment sensor) is attached to the housing 100 as described above. The temperature sensor 8 measures the temperature (environmental condition) in the housing 100. The temperature sensor 8 outputs temperature information to the temperature change determination unit 515 in response to a request from a temperature change determination unit 515 described later.

  As described above, the input receiving unit 400 receives input of image data from an external device or an operation input unit (not shown). Here, as described above, the image data includes, for example, an image formation instruction that is an instruction to form a predetermined toner image on each of the photosensitive drums 10a, 10b, 10c, and 10d with respect to the image forming unit 2, and image information related to the toner image. And number information.

  As described above, the image forming control unit 410 controls the image forming unit 2 to form toner images on the photosensitive drums 10a, 10b, 10c, and 10d. When image data is received by the input receiving unit 400, the image forming control unit 410 controls the image forming unit 2 to form a toner image on each of the photosensitive drums 10a, 10b, 10c, and 10d. The image forming control unit 410 changes the state of the image forming unit 2 from the first state corresponding to the non-printing operation state to the second state corresponding to the printing operation state.

  As shown in FIG. 4, the CPU 500 includes a constant applied voltage setting unit 510, a temperature change determination unit 515, a viscosity calculation unit 520 (viscosity detection unit), a viscosity change determination unit 530, an image formation permission unit 540, including.

  The constant application voltage setting unit 510 controls the charging unit 97a so as to apply a voltage to the first developer film while changing the voltage value, and the charging unit 97a applies a voltage while changing the voltage value. The surface potential measuring unit 700a is controlled to measure the surface potential of the second developer film. Specifically, the constant application voltage setting unit 510 controls the charger 971a via the charge control unit 972a so as to apply a voltage to the first developer film while changing the voltage value, and the charger 971a In a state where the voltage is applied while changing the value, the surface potential measuring device 701a is controlled to measure the surface potential of the second developer film via the surface potential measurement control unit 702a. Then, the constant applied voltage setting unit 510 sets the constant applied voltage based on the surface potential value of the second developer film measured by the surface potential measuring device 701a.

  The constant applied voltage setting unit 510 sets the applied voltage corresponding to the peak value in the measured surface potential value of the second developer film as the constant applied voltage. Specifically, the constant applied voltage setting unit 510 applies an application corresponding to the peak value (highest value) of the measured value of the surface potential value of the second developer film measured by the surface potential measuring unit 700a shown in FIG. Set the voltage to a constant applied voltage.

Here, the color printer 1 is configured to be able to change the state between a printing operation state in which a toner image is transferred from the photosensitive drum 10a to a paper T (transfer material) and a non-printing operation state in which the toner image is not transferred. .
Then, when the color printer 1 is in a non-printing operation state, the constant applied voltage setting unit 510 starts control on the charging unit 97a and the surface potential measuring unit 700a to set the constant applied voltage. For example, the constant applied voltage setting unit 510 starts control of the charging unit 97a and the surface potential measuring unit 700a immediately before the color printer 1 changes (switches) from the non-printing operation state to the printing operation state, and the constant application voltage setting unit 510 Set. Further, for example, the constant applied voltage setting unit 510 receives the image data from the input receiving unit 400, so that the image forming control unit 410 moves the image forming unit 2 from the first state corresponding to the non-printing operation state. When the state is changed to the second state corresponding to the printing operation state, control on the charging unit 97a and the surface potential measuring unit 700a is started to set a constant applied voltage.

The constant applied voltage setting unit 510 starts control of the charging unit 97a and the surface potential measurement unit 700a when a temperature change determination unit 515 (environment change determination unit) described later determines that the change in the environmental condition exceeds a predetermined range. Then, a constant applied voltage is set.
When the viscosity change determination unit 530 determines that the change in viscosity exceeds a predetermined range, the constant application voltage setting unit 510 starts control of the charging unit 97a and the surface potential measurement unit 700a to set the constant application voltage.

  The constant applied voltage setting unit 510 outputs information on the set constant applied voltage to the constant applied voltage value storage unit 601 of the memory 600 described later.

The temperature change determination unit 515 (environmental change determination unit) determines whether or not the temperature state change (environmental state change) exceeds a predetermined range based on the measurement result (temperature) by the temperature sensor 8 (environment sensor). To do.
For example, the temperature change determination unit 515 uses, as a reference, the temperature at which the predetermined constant applied voltage is set by the (previous) constant applied voltage setting unit 510, and the temperature measured by the temperature sensor 8 thereafter is outside the predetermined range ( It is determined whether or not the value exceeds any one of the upper and lower threshold values.
When the temperature change determination unit 515 determines that the temperature measured by the temperature sensor 8 is outside the predetermined range, the temperature change determination unit 515 outputs information to that effect to the constant applied voltage setting unit 510.

Here, the temperature is a preferable index because the change in the viscosity of the liquid portion having a large influence on the aggregation (migration) of the toner contained in the liquid developer can be easily grasped.
In the present embodiment, the color printer 1 includes a functional unit that calculates the viscosity of the liquid developer based on the measured temperature as follows.

  The viscosity calculation unit 520 calculates the viscosity of the liquid developer using the measurement result (temperature) by the temperature sensor 8 and an arithmetic expression stored in the viscosity calculation information storage unit 620 in the memory 600 described later. For example, the viscosity calculation unit 520 may be configured to be able to calculate the viscosity for each liquid developer of each color, or may be configured to be able to calculate the viscosity for each type of liquid developer.

The viscosity change determination unit 530 determines whether or not the change in viscosity exceeds a predetermined range based on the viscosity of the liquid developer calculated by the viscosity calculation unit 520.
For example, the viscosity change determination unit 530 uses the viscosity calculated by the viscosity calculation unit 520 as a reference based on the temperature at which the predetermined constant application voltage is set by the (previous) constant application voltage setting unit 510, and then the viscosity change It is determined whether or not the viscosity calculated by the calculation unit 520 is outside a predetermined range (a value exceeding either the upper or lower threshold).
When the viscosity change determination unit 530 determines that the viscosity calculated by the viscosity calculation unit 520 is outside the predetermined range, the viscosity change determination unit 530 outputs information to that effect to the constant applied voltage setting unit 510.

  Here, the color printer 1 according to the present embodiment can cause one or both of the temperature change determination unit 515 and the viscosity change determination unit 530 to function.

  The image formation permission unit 540 sends a predetermined toner image on the photosensitive drum 10a based on the image data to the image formation control unit 410 after a predetermined time has elapsed since the constant application voltage was set by the constant application voltage setting unit 510. Is permitted to control the image forming unit 2 to form Further, the image formation permission unit 540 controls the image formation control unit 410 to change the state of the image forming unit 2 from the first state corresponding to the non-printing operation state to the second state corresponding to the printing operation state. Allow that.

  As shown in FIG. 4, the memory 600 includes a constant applied voltage value storage unit 601, a reference temperature storage unit 610, and a viscosity calculation information storage unit 620.

  The constant applied voltage value storage unit 601 stores constant applied voltages for the chargers 971a, 971b, 971c, and 971d. The constant applied voltage value storage unit 601 includes, for example, chargers 971a, 971b, 971c, 971d—constant applied voltage tables.

Each constant application voltage stored in the constant application voltage value storage unit 601 is updated each time a new constant application voltage is set by the constant application voltage setting unit 510.
The constant applied voltage value storage unit 601 is appropriately referred to by the charging control units 972a, 972b, 972c, and 972d.

  The reference temperature storage unit 610 stores a reference temperature serving as a reference for temperature change determination by the temperature change determination unit 515. The reference temperature storage unit 610 updates the reference temperature based on the temperature information from the temperature sensor 8 every time a new constant application voltage is set by the constant application voltage setting unit 510.

The viscosity calculation information storage unit 620 stores a relational expression (calculation expression) for calculating the viscosity of the liquid developer as a function of temperature.
For example, the viscosity calculation unit 520 may store a relational expression (calculation expression) for calculating the viscosity for each color liquid developer. Further, the viscosity calculation unit 520 may be configured to be able to calculate the viscosity for each type of liquid developer, for example.

  Next, the liquid developer circulating device LB will be described. Here, the liquid developer circulation device LB will be described in detail, and description of other liquid developer circulation devices LB, LM, and LC having the same configuration will be omitted.

As shown in FIG. 2, the liquid developer circulating device LB includes a first recovery container 81a, a separation / extraction device 82, a second recovery container 83a, an adjustment container 84a, a toner tank TB, a carrier tank CB, And a reserve tank 87a. The liquid developer circulating device LB is a device for reusing the liquid developer that has not been used for image formation.
The first recovery container 81a is a container for recovering the liquid developer remaining on the surface (surface) of the photosensitive drum 10a.

  The separation and extraction device 82 is a device for separating the liquid developer in the first recovery container 81a into toner and carrier liquid. The separation and extraction device 82 is connected to the first recovery container 81a through the flow path R8a. A pump P6a is provided in the flow path R8a. The liquid developer in the first recovery container 81a is sent to the separation / extraction device 82 through the flow path R8a.

  The separation / extraction device 82 is connected to the carrier tank CB via the flow path R9a. A pump P7a is provided in the flow path R9a. The carrier liquid separated and extracted by the separation and extraction device 82 is sent to the carrier tank CB through the flow path R9a.

  The second collection container 83a is a container for collecting the liquid developer remaining in the developing device 9a without being used for image formation. The second collection container 83a is connected to the developing roller cleaning device 96a of the developing device 9a via the flow path R1a.

The flow path R1a is formed so as to connect the developing roller cleaning device 96a and the second recovery container 83a. The flow path R1a sends the liquid developer recovered by the developing roller cleaning device 96a toward the second recovery container 83a.
That is, the flow path R1a sends the liquid developer remaining in the developing roller 91a and removed (recovered) by the developing roller cleaning device 96a toward the second recovery container 83a.

  The adjustment container 84a is a container for adjusting the toner concentration of the liquid developer to a predetermined value. The adjustment container 84a is connected to the second recovery container 83a via the flow path R3a. A pump P1a is provided in the flow path R3a. The liquid developer in the second collection container 83a is sent to the adjustment container 84a through the flow path R3a.

  The toner tank TB stores a liquid developer having a higher toner concentration than the liquid developer used in the developing device 9a. The liquid developer having a high toner concentration is used to increase the toner concentration in the adjustment container 84a. The toner tank TB is connected to the adjustment container 84a through the flow path R5a. A pump P5a is provided in the flow path R5a. The liquid developer having a high toner concentration stored in the toner tank TB is sent to the adjustment container 84a through the flow path R5a.

  The carrier tank CB contains a carrier liquid. The carrier liquid is used to lower the toner concentration in the adjustment container 84a. Further, the carrier tank CB is connected to the adjustment container 84a via the flow path R4a. A pump P2a is provided in the flow path R4a. The carrier liquid is sent to the adjustment container 84a through the flow path R4a. A carrier tank similar to the carrier tank CB is also provided in each of the other liquid developer circulating devices LM, LC, and LY (see FIG. 1). These carrier tanks are supplied with carrier liquid from a main carrier tank MT (see FIG. 1) common to each color.

The reserve tank 87a contains a liquid developer to be replenished to the developing device 9a.
The reserve tank 87a is connected to the adjustment container 84a via the flow path R6a. A pump P3a is provided in the flow path R6a. The liquid developer accommodated in the adjustment container 84a is sent to the reserve tank 87a through the flow path R6a.

  The reserve tank 87a is connected to the toner tank TB via the flow path R10a. A pump P8a is provided in the flow path R10a. The liquid developer having a high toner concentration stored in the toner tank TB is sent to the reserve tank 87a through the flow path R10a. By supplying the liquid developer having a high toner concentration from the flow path R10a, the toner concentration of the liquid developer stored in the reserve tank 87a can be increased in a short time.

  The reserve tank 87a is connected to the carrier tank CB via the flow path R11a. A pump P9a is provided in the flow path R11a. The carrier liquid stored in the carrier tank CB is sent to the reserve tank 87a through the flow path R11a. By supplying the carrier liquid from the flow path R11a, the toner concentration of the liquid developer stored in the reserve tank 87a can be lowered in a short time.

The reserve tank 87a is connected to the developer supply nozzle 941a via the flow path R7a. A pump P4a is provided in the flow path R7a. The liquid developer stored in the reserve tank 87a is sent to the developer supply nozzle 941a through the flow path R7a. Then, the liquid developer sent to the developer supply nozzle 941a is supplied toward the storage portion 951a of the developing container 95a.
The liquid developer is stored in the storage portion 951a of the developing container 95a. The liquid developer is stored in the storage portion 951a of the developing container 95a in a state where the storage amount is kept constant.

Next, the operation of the color printer 1 will be described.
First, an image forming operation of the color printer 1 will be described with reference to FIG.
The color printer 1 receives image data including an image forming instruction from a PC (not shown) connected to the color printer 1 via an input receiving unit 400 (see FIG. 3).
The color printer 1 receives permission to start image formation from the image formation permission unit 540 (see FIG. 4), and causes the image formation unit 2 to start image formation. The color printer 1 forms a toner image of each color using the image forming units FB, FY, FC, and FM based on the image information included in the image data.

  Specifically, in the color printer 1, the image formation control unit 410 (see FIGS. 3 and 4) that has received permission to start image formation from the image formation permission unit 540, based on the image information included in the image data. Various operation units are controlled to form electrostatic latent images on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d. Then, the color printer 1 causes the developing devices 9a, 9b, 9c, and 9d to operate so as to supply various toners to the electrostatic latent images, and the color toner images are respectively formed on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d. To form.

  The color printer 1 converts the color toner images (color toner images formed on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d) formed by the image forming units FB, FY, FC, and FM to the intermediate transfer belt 21. Are transferred while being superimposed on each other. As a result, a color toner image is formed on the intermediate transfer belt 21.

In synchronism with the formation of the color toner image, the color printer 1 takes out the paper T stored in the paper feed cassette 31 of the paper storage unit 3 from the paper feed cassette 31 by the paper feed roller 32, and uses the separation roller pair 33. Each sheet is sent to the sheet transport unit 6.
The transport roller pair 74 of the paper transport unit 6 feeds the paper T to the registration roller pair 75.
The registration roller pair 75 corrects the transport posture of the paper T and temporarily stops the transport of the paper T. Then, the registration roller pair 75 sends the paper T to the secondary transfer unit 4 in synchronization with the primary transfer to the intermediate transfer belt 21.

The secondary transfer unit 4 secondarily transfers the color toner image on the intermediate transfer belt 21 to the paper T. The sheet T on which the color toner image is secondarily transferred is conveyed to the fixing unit 5 by the sheet conveying unit 6.
The fixing unit 5 fixes the color toner image on the paper T by heating the paper T on which the color toner image is transferred in a pressurized state.

  The paper transport unit 6 transports the paper T on which the color toner image is fixed to the paper discharge unit 7. The paper discharge unit 7 discharges the paper T on which the color toner image is formed (fixed) on a discharge tray 72 formed on the upper surface portion of the color printer 1 by the discharge roller pair 71.

Next, with reference to FIGS. 6 and 7, the operation of the color printer 1 will be described focusing on the operation of the developing device 9a.
FIG. 6 is a flowchart for explaining the initial setting operation of the constant applied voltage in the color printer 1.

In step ST101, the user operates a power operation unit (not shown) to turn on the color printer 1.
When the power is turned on, the constant applied voltage setting unit 510 starts an initial setting operation.
First, in step ST102, the constant applied voltage setting unit 510 instructs the charger 971a to start applying a voltage to the first developer film while changing the voltage value via the charging control unit 972a.

  At the same time, in step ST103, the constant applied voltage setting unit 510 instructs the surface potential measuring device 701a to start measuring the surface potential value of the second developer film via the surface potential measurement control unit 702a.

  Subsequently, in step ST104, the surface potential measurement unit 700a measures the surface potential value of the second developer film in a state where the charging unit 97a applies a voltage while changing the voltage value, and the result of the surface potential measurement is as follows. To get. The measurement result is as shown by the solid line in FIG.

  Subsequently, in step ST105, the constant applied voltage setting unit 510 corresponds to the peak value P0 of the surface potential value at which the constant applied voltage is measured based on the measurement result (solid line in FIG. 5) by the surface potential measuring unit 700a. Set the applied voltage to a constant applied voltage (initial setting).

Subsequently, in step ST106, the constant application voltage setting unit 510 controls the charging unit 97a so as to continuously apply the initially set constant application voltage to the first developer film.
Thereafter, the process ends.

  Next, the operation for updating the constant applied voltage in the color printer 1 will be described. FIG. 7 is a flowchart for explaining the constant applied voltage update operation in the color printer 1.

  First, in step ST201, the charging unit 97a (charger 971a) applies the constant application voltage (application voltage corresponding to the peak value P0) initially set by the constant application voltage setting unit 510 to the surface (first development). Applied to the agent film).

  Subsequently, in step ST202, the input receiving unit 400 receives input of image data from an external device. Accordingly, the image formation control unit 410 controls the image forming unit 2 to form an electrostatic latent image on the surface of the photosensitive drum 10a according to the image data received by the input receiving unit 400, and a predetermined number of images. The forming operation (printing) is continued (printing operation state).

Subsequently, in step ST203, the temperature change determination unit 515 acquires measured temperature information (temperature in the housing) from the temperature sensor 8 at predetermined intervals.
Subsequently, in step ST204, the temperature change determination unit 515 determines whether or not the temperature change is equal to or greater than a predetermined threshold with reference to the reference temperature stored in the reference temperature storage unit 610.
If the temperature change is equal to or greater than a predetermined threshold with reference to the reference temperature stored in reference temperature storage unit 610 (ST204, YES), temperature change determination unit 515 advances the process to step ST205.
When the temperature change is less than the predetermined threshold with reference to the reference temperature stored in reference temperature storage unit 610 (ST204, NO), temperature change determination unit 515 returns the process to step ST203.

  Subsequently, in step ST205, the temperature change determination unit 515 performs a predetermined notification that notifies the constant applied voltage setting unit 510 that the temperature change is equal to or greater than a predetermined threshold with reference to the reference temperature.

Subsequently, in step ST206, the constant applied voltage setting unit 510 checks whether or not a predetermined number of image forming operations (printing) have been completed. That is, the constant applied voltage setting unit 510 confirms (determines) whether or not the color printer 1 has changed from the printing operation state to the non-printing operation state.
When the constant applied voltage setting unit 510 confirms that the predetermined number of image forming operations have been completed (non-printing operation state) (YES in step ST206), the process proceeds to step ST207.
When it is not possible to confirm that the predetermined number of image forming operations have been completed (non-printing operation state) (NO in step ST206), constant applied voltage setting unit 510 returns the process to step ST206.

  Subsequently, in step ST207, the constant application voltage setting unit 510 instructs the charger 971a to start voltage application to the first developer film via the charging control unit 972a while changing the voltage value. At the same time, the constant applied voltage setting unit 510 instructs the surface potential measuring device 701a to start measuring the surface potential value of the second developer film via the surface potential measurement control unit 702a.

  Subsequently, in step ST208, the surface potential measuring unit 700a measures the surface potential value of the second developer film in a state where the charging unit 97a is applying a voltage while changing the voltage value. In this measurement result, since the temperature is changed, the maximum value of the surface potential is increased or decreased as shown by the dotted line or the alternate long and short dash line in FIG.

  Subsequently, in step ST209, the constant applied voltage setting unit 510 changes the constant applied voltage to the peak value P1 or P2 of the surface potential value based on the measurement result (dotted line or one-dot chain line in FIG. 5) by the surface potential measuring unit 700a. The corresponding applied voltage is set to a constant applied voltage (updated).

Subsequently, in step ST210, the constant applied voltage setting unit 510 controls the charging unit 97a so as to continuously apply the updated constant applied voltage to the first developer film.
Thereafter, the process ends.

According to this embodiment, the color printer 1 measures the surface potential value of the second developer film formed on the surface of the photosensitive drum 10a, and based on the measured surface potential value, the developing roller 91a. A constant applied voltage (electric field) is set for the liquid developer constituting the first developer film formed on the surface.
Therefore, the color printer 1 can apply an appropriate voltage (electric field) corresponding to a change in environmental conditions. Therefore, in the color printer 1, the developing roller 91a has a cleaning failure caused by the intensity of the electric field applied to the liquid developer being excessive and the toner particles adhering to the developing roller 91a is too strong. It is possible to suppress the occurrence of blurring of the toner image due to the too weak adhesion of the toner particles to the toner and to improve the image quality.

According to the present embodiment, the constant applied voltage setting unit 510 of the color printer 1 sets the applied voltage corresponding to the highest value of the measured surface potential values.
Therefore, the color printer 1 can apply the most appropriate voltage to the liquid developer regardless of changes in environmental conditions and changes in the state of the second developer film on the surface of the photosensitive drum 10a. Therefore, the color printer 1 can maintain the toner image with the highest quality.

Further, according to the present embodiment, the constant applied voltage setting unit 510 of the color printer 1 starts controlling the charging unit 97a and the surface potential measuring unit 700a when the color printer 1 is in a non-printing operation state.
Therefore, the color printer 1 can accurately set the constant applied voltage based on the measurement of the surface potential value, and is appropriate from immediately after the start of the printing operation (immediately after the state change from the non-printing operation state to the printing operation state). It is possible to apply various voltages. Therefore, the color printer 1 can exert the effect of improving the quality of the toner image for all printed matter.

Further, according to the present embodiment, the color printer 1 includes the temperature sensor 8 as an environmental sensor for measuring the environmental situation, and the constant applied voltage setting unit 510 is based on the measured value (temperature) from the temperature sensor 8. It is determined whether to start control of the charging unit 97a and the surface potential measuring unit 700a. Furthermore, the color printer 1 is configured such that when the temperature change exceeds a predetermined range, the constant applied voltage setting unit 510 starts controlling the charging unit 97a and the surface potential measuring unit 700a.
For this reason, when the viscosity of the liquid developer changes beyond a predetermined range as the environmental temperature varies, the constant applied voltage can be reset to an appropriate constant applied voltage corresponding to the temperature. Accordingly, it is possible to reliably obtain a high-quality image by always applying an appropriate voltage to the liquid developer according to the change in the environmental temperature.

Further, according to the present embodiment, the color printer 1 detects the viscosity of the liquid developer based on the measurement result by the temperature sensor 8, and when it is determined that the change in the detected viscosity exceeds a predetermined range, The constant applied voltage setting unit 510 is configured to start control on the charging unit 97a and the surface potential measuring unit 700a.
For this reason, as described above, when the viscosity of the liquid developer changes beyond a predetermined range as the environmental temperature varies, the constant applied voltage can be reset to an appropriate constant applied voltage corresponding to the temperature. Accordingly, it is possible to reliably obtain a high-quality image by always applying an appropriate voltage to the liquid developer according to the change in the environmental temperature.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the above-described embodiment, the color printer 1 uses the constant applied voltage as the constant applied electric field applied to the liquid developer from the charging unit 97a, but is not limited thereto. For example, the color printer 1 may use a constant applied current as a constant applied electric field applied to the liquid developer from the charging unit 97a.

  In this case, the color printer 1 includes a constant applied current setting unit that sets a constant applied current. The constant application current setting unit controls the charging unit so as to apply a current to the first developer film while changing a current value, and the charging unit applies a current while changing the current value. The surface potential measuring unit is controlled to measure the surface potential value of the second developer film, and the constant applied current is set based on the surface potential value measured by the surface potential measuring unit.

  Similarly to the embodiment, the constant applied current setting unit may set the applied current corresponding to the highest value in the measured surface potential value as the constant applied current.

  Similarly to the embodiment, the constant applied current setting unit may start control of the charging unit and the surface potential measuring unit in the non-printing operation state.

  Similarly to the embodiment, the color printer 1 determines whether or not the change in the environmental condition exceeds a predetermined range based on an environmental sensor (for example, a temperature sensor) that measures the environmental condition and a measurement result by the environmental sensor. An environmental change determination unit (for example, a temperature change determination unit) for determination. The constant applied current setting unit may start control of the charging unit and the surface potential measurement unit when the environmental change determination unit determines that the change in the environmental condition exceeds a predetermined range.

  Similarly to the embodiment, the color printer 1 is detected by a temperature sensor, a viscosity detection unit (for example, a viscosity calculation unit) that detects the viscosity of the liquid developer based on a measurement result by the temperature sensor, and a viscosity detection unit. A viscosity change determination unit that determines whether or not the change in viscosity exceeds a predetermined range based on the obtained viscosity. The constant applied current setting unit may start control of the charging unit and the surface potential measuring unit when the viscosity change determining unit determines that the change in viscosity exceeds a predetermined range.

Moreover, in this embodiment, although the temperature sensor 8 was used as an environmental sensor which measures an environmental condition, an environmental sensor is not limited to this. For example, a humidity sensor may be used as the environmental sensor, and a temperature sensor and a humidity sensor may be used in combination.
In the present embodiment, the viscosity calculation unit 520 calculates the viscosity of the liquid developer using an arithmetic expression stored in the viscosity calculation information storage unit 620 based on the measurement result (temperature) by the temperature sensor 8. However, the present invention is not limited to this. For example, the color printer 1 may previously store the relationship between the temperature measured by the temperature sensor 8 and the viscosity in a table in the viscosity calculation information storage unit 620. And the color printer 1 may be comprised so that the viscosity calculation part 520 can acquire the information of the viscosity corresponding to measurement temperature by reading the table at predetermined timing.

  In the present embodiment, the color printer 1 uses the constant applied voltage setting unit 510 as the constant applied voltage with the applied voltage corresponding to the maximum value (peak value P0) of the surface potential value measured by the surface potential measuring unit 700a. Although configured to set, the present invention is not limited to this. For example, the color printer 1 is configured such that the constant applied voltage setting unit 510 sets the applied voltage corresponding to any value (not necessarily a peak) in the region where the measured surface potential value is high as the constant applied voltage. May be.

In this embodiment, the color printer 1 is described as an example of the image forming apparatus. However, the image forming apparatus is not limited to this, and examples of the image forming apparatus include a color copier, a monochrome copier, a monochrome printer, and a facsimile. Or a multifunction machine of these.
Further, the sheet-like transfer material is not limited to paper, and may be a film sheet, for example.

  DESCRIPTION OF SYMBOLS 1 ... Color printer (image forming apparatus), 8 ... Temperature sensor (environment sensor), 9a, 9b, 9c, 9d ... Developing device, 10a, 10b, 10c, 10d ... Photosensitive drum (image carrier) 91a, 91b, 91c, 91d... Developing roller, 92a, 92b, 92c, 92d... Supply roller (developer pumping portion), 93a, 93b, 93c, 93d. 94b, 94c, 94d... Developer supply device (developer supply unit), 95a, 95b, 95c, 95d... Development container (developer storage unit), 97a, 97b, 97c, 97d. …… CPU, 510... Constant applied voltage setting unit (constant applied electric field setting unit), 515... Temperature change determination unit (environment change determination unit), 520. ...... Viscosity change determination unit, 600 ... Memory, 601 ... Constant applied voltage value storage unit, 610 ... Reference temperature storage unit, 620 ... Viscosity calculation information storage unit, 700a, 700b, 700c, 700d ... Surface Potential measurement unit, 701a, 701b, 701c, 701d ... Surface potential measurement device, 702a, 702b, 702c, 702d ... Surface potential measurement control unit, 971a, 971b, 971c, 971d ... Charger, 972a, 972b, 972c , 972d: Charging control unit

Claims (9)

An image bearing member on which an electrostatic latent image is formed and capable of carrying a toner image based on the electrostatic latent image;
A developing device for supplying a liquid developer to the image carrier,
A developer supply unit for supplying a liquid developer;
A developer storage section for storing the liquid developer supplied by the developer supply section;
A developer pumping unit that pumps up the liquid developer stored in the developer storing unit;
A liquid developer pumped up by the developer pumping unit is provided to be opposed to the image carrier so as to be rotatable about a rotation axis, and a first developer film is formed on the surface. A developing roller for supplying a liquid developer to the image carrier in a region facing the body;
A charging unit capable of applying an electric field to the liquid developer constituting the first developer film formed on the surface of the developing roller, the electric field to be applied being changeable, and a predetermined constant applied electric field A charging unit that can be applied continuously,
A surface potential measuring unit for measuring a surface potential value of a second developer film formed on the surface of the image carrier by the liquid developer supplied from the developing roller;
A constant applied electric field setting unit for setting the constant applied electric field,
When the constant applied electric field is set once, the charging unit is controlled to apply the electric field to the first developer film while changing the electric field value, and the charging unit applies the electric field while changing the electric field value. Controlling the surface potential measurement unit to measure the surface potential of the second developer film a plurality of times in a state where
A constant applied electric field setting unit configured to set the constant applied electric field corresponding to the highest value among a plurality of surface potential values obtained by the surface potential measuring unit measuring the surface potential of the second developer film a plurality of times ; , equipped with a,
It is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred,
The constant applied electric field setting unit includes:
The image forming apparatus that starts control of the charging unit and the surface potential measuring unit in the non-printing operation state . An environmental sensor for measuring environmental conditions;
An environmental change determination unit that determines whether or not a change in the environmental situation exceeds a predetermined range based on a measurement result by the environmental sensor;
The constant applied electric field setting unit includes:
2. The image forming apparatus according to claim 1, wherein when the environmental change determination unit determines that a change in an environmental condition exceeds a predetermined range, control of the charging unit and the surface potential measurement unit is started. A temperature sensor;
A viscosity detector that detects the viscosity of the liquid developer based on the measurement result of the temperature sensor;
A viscosity change determination unit that determines whether or not a change in viscosity exceeds a predetermined range based on the viscosity detected by the viscosity detection unit;
The constant applied electric field setting unit includes:
Wherein when the change in viscosity by a viscosity change determination unit is determined to exceed the predetermined range, the image forming apparatus according to claim 1 for starting the control for the charging section and said surface potential measuring unit. An image bearing member on which an electrostatic latent image is formed and capable of carrying a toner image based on the electrostatic latent image;
A developing device for supplying a liquid developer to the image carrier,
A developer supply unit for supplying a liquid developer;
A developer storage section for storing the liquid developer supplied by the developer supply section;
A developer pumping unit that pumps up the liquid developer stored in the developer storing unit;
A liquid developer pumped up by the developer pumping unit is provided to be opposed to the image carrier so as to be rotatable about a rotation axis, and a first developer film is formed on the surface. A developing roller for supplying a liquid developer to the image carrier in a region facing the body;
A charging unit capable of applying a voltage to the liquid developer constituting the first developer film formed on the surface of the developing roller, the voltage to be applied being changeable, and a predetermined constant applied voltage A charging unit that can be applied continuously,
A surface potential measuring unit for measuring a surface potential value of a second developer film formed on the surface of the image carrier by the liquid developer supplied from the developing roller;
A constant applied voltage setting unit for setting the constant applied voltage,
When setting the constant applied voltage once, the charging unit is controlled to apply a voltage to the first developer film while changing the voltage value, and the charging unit applies a voltage while changing the voltage value. Controlling the surface potential measurement unit to measure the surface potential of the second developer film a plurality of times in a state where
A constant applied voltage setting unit configured to set the constant applied voltage corresponding to the highest value among a plurality of surface potential values obtained by the surface potential measuring unit measuring the surface potential of the second developer film a plurality of times ; , equipped with a,
It is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred,
The constant applied voltage setting unit includes:
The image forming apparatus that starts control of the charging unit and the surface potential measuring unit in the non-printing operation state . An environmental sensor for measuring environmental conditions;
An environmental change determination unit that determines whether or not a change in the environmental situation exceeds a predetermined range based on a measurement result by the environmental sensor;
The constant applied voltage setting unit includes:
5. The image forming apparatus according to claim 4, wherein when the environmental change determination unit determines that the change in the environmental condition exceeds a predetermined range, the control of the charging unit and the surface potential measurement unit is started. A temperature sensor;
A viscosity detector that detects the viscosity of the liquid developer based on the measurement result of the temperature sensor;
A viscosity change determination unit that determines whether or not a change in viscosity exceeds a predetermined range based on the viscosity detected by the viscosity detection unit;
The constant applied voltage setting unit includes:
The image forming apparatus according to claim 4, wherein when the viscosity change determination unit determines that the change in viscosity exceeds a predetermined range, control of the charging unit and the surface potential measurement unit is started. An image bearing member on which an electrostatic latent image is formed and capable of carrying a toner image based on the electrostatic latent image;
A developing device for supplying a liquid developer to the image carrier,
A developer supply unit for supplying a liquid developer;
A developer storage section for storing the liquid developer supplied by the developer supply section;
A developer pumping unit that pumps up the liquid developer stored in the developer storing unit;
A liquid developer pumped up by the developer pumping unit is provided to be opposed to the image carrier so as to be rotatable about a rotation axis, and a first developer film is formed on the surface. A developing roller for supplying a liquid developer to the image carrier in a region facing the body;
A charging unit capable of applying an electric current to the liquid developer constituting the first developer film formed on the surface of the developing roller, the electric current to be applied being changeable, and a predetermined constant applied current A charging unit that can be applied continuously,
A surface potential measuring unit for measuring a surface potential value of a second developer film formed on the surface of the image carrier by the liquid developer supplied from the developing roller;
A constant applied current setting unit for setting the constant applied current,
When setting the constant applied current once, the charging unit is controlled to apply a current to the first developer film while changing the current value, and the charging unit applies a current while changing the current value. Controlling the surface potential measurement unit to measure the surface potential of the second developer film a plurality of times in a state where
A constant applied current setting unit configured to set the constant applied current corresponding to the highest value among a plurality of surface potential values obtained by the surface potential measuring unit measuring the surface potential of the second developer film a plurality of times ; , equipped with a,
It is configured to be able to change between a printing operation state in which the toner image is transferred from the image carrier to a transfer material and a non-printing operation state in which the toner image is not transferred,
The constant applied current setting unit includes:
The image forming apparatus that starts control of the charging unit and the surface potential measuring unit in the non-printing operation state . An environmental sensor for measuring environmental conditions;
An environmental change determination unit that determines whether or not a change in the environmental situation exceeds a predetermined range based on a measurement result by the environmental sensor;
The constant applied current setting unit includes:
The image forming apparatus according to claim 7, wherein when the environmental change determination unit determines that a change in an environmental condition exceeds a predetermined range, control for the charging unit and the surface potential measurement unit is started. A temperature sensor;
A viscosity detector that detects the viscosity of the liquid developer based on the measurement result of the temperature sensor;
A viscosity change determination unit that determines whether or not a change in viscosity exceeds a predetermined range based on the viscosity detected by the viscosity detection unit;
The constant applied current setting unit includes:
The image forming apparatus according to claim 7, wherein when the viscosity change determination unit determines that the change in viscosity exceeds a predetermined range, control of the charging unit and the surface potential measurement unit is started.

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