JP5289359B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus including the developing device.

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.
As a developing device that constitutes a wet image forming apparatus, a pump that pumps up the liquid developer stored in the liquid developer storage section, and a liquid that is disposed to face the pumping roller with a gap and is pumped up by the pumping roller. A developer supply roller in which a developer film is transferred to form a developer film on the surface; and a developer roller in which the developer film formed on the surface of the developer supply roller is transferred to hold the developer film on the surface; (For example, refer to Patent Document 1).
According to the developing device configured as described above, the liquid developer stored in the liquid developer storage unit is sequentially transferred through the scooping roller, the developer supply roller, and the developing roller, and is supplied to the image carrier.

JP 7-219355 A

However, in the developing device constituting the wet image forming apparatus, when the viscosity of the liquid developer becomes high, the liquid developer is not smoothly transferred from the pumping roller to the developer supply roller. As a result, the developer film held on the surface of the film may become dull, resulting in a problem that the quality of the formed image is deteriorated.
In addition, the liquid developer viscosity changes depending on the environmental temperature of the image forming apparatus, so that the amount of liquid developer pumped by the pumping roller changes. There is also a problem that image blurring occurs due to excessive supply of developer.

The present invention allows the liquid developer to be smoothly transferred from the drawing roller to the developer supply roller, and can suppress the occurrence of problems due to insufficient supply of liquid developer to the development roller or excessive supply of liquid developer. An object is to provide an apparatus.
Another object of the present invention is to provide an image forming apparatus including the developing device.

  The present invention relates to a developing device that supplies a liquid developer to an image carrier, and includes a liquid developer storage section that stores the liquid developer, and a pumping roller that pumps up the liquid developer stored in the liquid developer storage section. A developer supply roller disposed opposite to the pumping roller with a gap, and a liquid developer pumped up by the pumping roller is transferred to form a developer film on the surface; and the developer supply A regulating member that is disposed in proximity to or in contact with the roller and regulates the film thickness of the developer film formed on the surface of the developer supply roller so as not to be thicker than a predetermined thickness; and the developer supply roller The developer film formed on the surface of the developer supply roller that is disposed to face and abut against each other is transferred, and a developer roller that holds the developer film on the surface, and a liquid developer reservoir A temperature sensor for measuring the temperature of the retained liquid developer, a pumping roller rotation driving unit for driving the pumping roller to rotate, and the rotation speed of the pumping roller is set to be equal to or higher than the rotation speed of the developer supply roller, and the temperature sensor And a pumping roller rotation drive control unit that controls the pumping roller rotation driving unit so as to change the rotation speed of the pumping roller based on the temperature of the liquid developer measured by the above.

The developer supply roller is disposed to face the developer supply roller with a gap, and is disposed between the pumping roller and the regulating member in the rotation direction of the developer supply roller, and the film thickness is regulated by the regulating member. Further comprising a squeeze roller for adjusting the film thickness of the developer film before being
The developer supply roller preferably rotates in the same direction as the scooping roller at a position facing the scooping roller.

  Further, the gap between the developer supply roller and the squeeze roller is equal to or less than the gap between the scoop roller and the developer supply roller, and the squeeze roller is located at a position facing the developer supply roller. It is preferable to rotate in the direction opposite to the rotation direction of the developer supply roller.

  The pumping roller rotation drive control unit increases the rotation speed of the pumping roller when the temperature of the liquid developer measured by the temperature sensor is high, and the temperature of the liquid developer measured by the temperature sensor. It is preferable to control the pumping roller rotation driving unit so as to slow down the rotation speed of the pumping roller when the roller is low.

  In addition, when the rotational speed of the squeeze roller rotational drive unit that rotationally drives the squeeze roller and the pumping roller is increased, the rotational speed of the squeeze roller is decreased, and when the rotational speed of the pumping roller is decreased It is preferable to include a squeeze roller rotation drive control unit that controls the squeeze roller rotation drive unit so as to increase the rotation speed of the squeeze roller.

  According to another aspect of the present invention, there is provided an image forming unit having the developing device and the image carrier, wherein the image forming unit forms a toner image on a sheet-like transfer material, and the transfer material is formed by the image formation unit. The present invention relates to an image forming apparatus comprising: a fixing unit that fixes a toner image formed on the toner image.

According to the developing device of the present invention, the liquid developer is smoothly transferred from the drawing roller to the developer supply roller, and occurrence of problems due to insufficient supply of liquid developer to the development roller or excessive supply of liquid developer is suppressed. It is possible to provide a developing device capable of performing the above.
Further, according to the image forming apparatus of the present invention, an image forming apparatus including the developing device can be provided.

2 is an overall view for explaining each component of the color printer 1. FIG. It is a schematic diagram explaining the structure of the liquid developer circulation device LY. FIG. 6 is an enlarged cross-sectional view illustrating the arrangement of each component of an image forming unit FY including a developing device 9b. It is an expanded sectional view explaining the structure and functional block of the developing device 9b. It is a graph which shows the temperature dependence data of liquid developer GB. It is a flowchart explaining operation | movement of the developing device 9b.

Hereinafter, embodiments of the present invention will be described 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. .

  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 to the paper T on the paper T. 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 intermediate transfer belt 21 is an endless belt member having conductivity.
The intermediate transfer belt 21 is wider than the largest paper 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 “front surface”, and the other surface is referred to as “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 30b, 30c, 30d. Here, among the image forming units, the image forming unit FB closest to the secondary transfer unit 4 does not have the carrier liquid removal roller, but the other configurations are the same as those of the other image forming units FY, FC, and FM. is there.

  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.

  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 devices 12a, 12b, 12c, and 12d is a photosensitive drum 10a, 10b, or 10c that is uniformly charged to a predetermined polarity and potential based on image data input from an external device (for example, a PC or the like). The surface of 10d 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.

Each of the developing devices 9a, 9b, 9c, and 9d includes a liquid developer GB, GY, GC, and GM containing a toner and a carrier liquid that is formed on the surface of each of the photosensitive drums 10a, 10b, 10c, and 10d. Hold to face the image. 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 respectively disposed on the back surface of the intermediate transfer belt 21 so as to correspond to the photosensitive drums 10a, 10b, 10c, and 10d. 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 opposite to that of the toner constituting the toner image (minus in this embodiment) from a power source (not shown). That is, each of the primary transfer rollers 20a, 20b, 20c, and 20d applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position where it is 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 the periphery thereof.

  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 surface of each of the photosensitive drums 10a, 10b, 10c, and 10d as the photosensitive drums 10a, 10b, 10c, and 10d rotate. take.

  The conveying screws 28a, 28b, 28c, and 28d are disposed inside the cleaning devices 26a, 26b, 26c, and 26d, respectively. Each of the conveying screws 28a, 28b, 28c, and 28d receives the liquid developer scraped by the cleaning blades 27a, 27b, 27c, and 27d and accommodated in the cleaning devices 26a, 26b, 26c, and 26d, respectively. It conveys to collection containers 81a, 81b (see FIG. 2), 81c, 81d. Further, the conveying screws 28a, 28b, 28c, and 28d are removed from the intermediate transfer belt 21 by carrier liquid removing rollers 30b, 30c, and 30d, which will be described later, and accommodated in the cleaning devices 26a, 26b, 26c, and 26d, respectively. The carrier liquid is also transferred to the first collection containers 81a, 81b (see FIG. 2), 81c, 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 static eliminators 13a, 13b, 13c, and 13d respectively remove static charges from the portions of the photosensitive drums 10a, 10b, 10c, and 10d from which the liquid developer has been removed by the cleaning blades 27a, 27b, 27c, and 27d. Process.

  Each of the carrier liquid removal rollers 30b, 30c, and 30d is a substantially columnar member that is disposed so as to be rotatable about rotation axes parallel to the rotation axes of the photosensitive drums 10b, 10c, and 10d. The carrier liquid removal rollers 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 30b, 30c, and 30d is disposed to face the surface of each of the photosensitive drums 10b, 10c, and 10d. Each of the carrier liquid removal rollers 30b, 30c, and 30d is photosensitive on the downstream side in the rotational direction of each of the photosensitive drums 10b, 10c, and 10d from the position where the photosensitive drums 10b, 10c, and 10d are in contact with the intermediate transfer belt 21. The body drums 10b, 10c, and 10d are arranged to face each other.

  Each of the carrier liquid removal rollers 30b, 30c, and 30d rotates in the same direction as each of the photosensitive drums 10b, 10c, and 10d when viewed from a predetermined direction. The carrier liquids removed by the carrier liquid removal rollers 30b, 30c, and 30d are accommodated in the cleaning devices 26b, 26c, and 26d.

  The paper storage unit 3 is disposed in the lower part of the color printer 1 in the vertical direction. The paper storage unit 3 includes 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 a paper transport unit 6 in a state in which a plurality of papers T overlap. And a separation roller pair 33 that suppresses the supply.

  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 intermediate transfer belt 21 (surface) to 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 display of the other transport roller pairs is omitted.

  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 from which the paper T on which the toner image is transferred by the secondary transfer unit 4 and 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 pairs 71 is shown, and the display of the other discharge roller pairs is omitted.

Next, the developing device and the liquid developer circulating device will be described with reference to FIGS.
FIG. 2 is a schematic diagram illustrating the configuration of the liquid developer circulating device LY. FIG. 3 is an enlarged cross-sectional view for explaining the arrangement of each component of the image forming unit FY including the developing device 9b. FIG. 4 is an enlarged cross-sectional view illustrating the structure and functional blocks of the developing device 9b.
First, the developing devices 9a, 9b, 9c, and 9d will be described. Here, the developing device 9b will be described in detail, and description of the other developing devices 9a, 9c, and 9d having the same configuration will be omitted.

  As shown in FIGS. 2 to 4, the developing device 9b is a device for supplying the liquid developer GB to the photosensitive drum 10b. The developing device 9b includes a developing container 95b serving as a liquid developer storing unit that stores the liquid developer GB, a developing roller 91b, a supply roller 92b serving as a developer supplying roller, and a liquid developer stored in the developing container 95b. A pumping roller 93b that pumps GB, a supply roller blade member 921b as a regulating member, a squeeze roller 98b, a developer supply device 94b that pumps the liquid developer GB to the storage unit of the pumping roller 93b or the developing container 95b, and a developing A roller cleaning device 96b and a charging device 97b are provided.

The developing container 95b is a container capable of storing (storing) the liquid developer GB inside (storing part), and stores the liquid developer GB supplied by the developer supplying device 94b in the storing part. The developing container 95b includes a developing roller 91b, a supply roller 92b, a pumping roller 93b, a supply roller blade member 921b, a squeeze roller 98b, a developer supply device 94b, a development roller cleaning device 96b, and a charging device 97b. Support.
A discharge portion 952b (see FIG. 2) capable of discharging the liquid developer GB is formed at an end portion on the downstream side in the axial direction of each roller at the bottom of the housing portion of the developing container 95b. The discharge portion 952b is connected to the second recovery container 83b of the liquid developer circulation device LY through a flow path R2b described later.

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

  The developing roller 91b is disposed so as to face and contact the supply roller 92b. In the developing roller 91b, a developer film GB1 (described later) formed on the surface of the supply roller 92b is transferred to the elastic portion on the surface, and the transferred developer film GB1 is held on the surface of the elastic portion.

The supply roller 92b is a roller member that supplies the liquid developer GB to the development roller 91b. The supply roller 92b is disposed in contact with the developing roller 91b so as to face each other.
The supply roller 92b is disposed below the vertical direction Z in the developing roller 91b. Further, the supply roller 92b is disposed such that the rotation shaft is displaced in the horizontal direction (left-right direction X) with respect to the rotation shaft of the developing roller 91b. The supply roller 92b is disposed between the developing roller 91b and the drawing roller 93b.

  The supply roller 92b has a role as a member called a so-called anilox roller, and a spiral groove is formed on the surface of the supply roller 92b. The supply roller 92b is configured to hold the liquid developer GB on the surface and form the developer film GB1 when the liquid developer GB flows into the spiral groove. Here, the liquid developer GB (developer film GB1) held on the surface of the supply roller 92b is moved from the one end side in the axial direction (the front side in FIG. 4) to the other end side with the rotation of the supply roller 92b. (In FIG. 4, the back side of the sheet).

  In the vicinity of the supply roller 92b, the supply roller blade member 921b is disposed so that the tip is in contact with or close to the surface of the supply roller 92b. The supply roller blade member 921b regulates the thickness (film thickness) of the liquid developer GB film (developer film GB1) formed on the surface of the supply roller 92b so as not to be thicker than a predetermined thickness.

  The scooping roller 93b is disposed in a state where the lower part thereof is immersed in the liquid developer GB stored in the developing container 95b. The pumping roller 93b is rotated in the direction of the arrow (counterclockwise) in FIGS. The pumping roller 93b is a member shorter than the supply roller 92b in the axial direction, and is disposed below the supply roller 92b in the vertical direction Z. In addition, the pumping roller 93b is disposed such that its rotation shaft is displaced in the horizontal direction (left-right direction X) with respect to the rotation shaft of the supply roller 92b.

  The supply roller 92b is rotated in the direction of the arrow (clockwise) in FIGS. That is, the supply roller 92b rotates in the same direction as the pumping roller 93b at a position facing the pumping roller 93b. As a result, the liquid developer GB pumped up by the pumping roller 93b is displaced, and a developer film GB1 is formed on the surface of the supply roller 92b.

  The pumping roller 93b is disposed to face the supply roller 92b. The supply roller 92b has a gap (hereinafter also referred to as “first gap”) K1 with the pumping roller 93b, and is disposed to face the pumping roller 93b. The first gap K1 is, for example, 0.2 to 2 mm, preferably 0.5 to 1 mm.

  The scooping roller 93b can support the liquid developer in the vicinity of the nip NB facing the supply roller 92b. The scooping roller 93b is arranged so that the rotation shaft is displaced in the horizontal direction (left-right direction X) with respect to the rotation shaft of the supply roller 92b, thereby allowing the liquid developer to be easily stored in the vicinity of the nip portion NB.

  The drawing roller 93b is rotated in the direction of the arrow (counterclockwise) in FIG. That is, at the nip portion NB where the supply roller 92b and the pumping roller 93b face each other, the surface of the supply roller 92b moves in the same direction as the surface of the pumping roller 93b. Thereby, the liquid developer stored in the nip portion NB is easily supplied to the supply roller 92b.

  The developer supply device 94b is a device for supplying the liquid developer whose concentration has been adjusted to the vicinity of the nip NB between the supply roller 92b and the pumping roller 93b. The developer supply device 94b supplies the liquid developer GB at a position slightly upstream in the rotational direction of the pumping roller 93b from the gap K1 between the pumping roller 93b and the supply roller 92b.

  Part of the liquid developer GB supplied from the developer supply device 94b is directly transferred from the surface of the pumping roller 93b to the surface (spiral groove) of the pumping roller 93b, and via the surface of the pumping roller 93b. It is stored in the accommodating portion of the developing container 95b. The stored liquid developer GB is pumped up by the pumping roller 93b and is transferred to the surface (spiral groove) of the supply roller 92b.

  Further, at the nip portion NA where the developing roller 91b and the supply roller 92b abut, the surface of the developing roller 91b moves in the opposite direction to the surface of the supply roller 92b. Thus, the liquid developer GB (developer film GB1) transferred and held on the surface of the supply roller 92b is transferred to the surface of the developing roller 91b. Here, since the film thickness of the developer film GB1 of the supply roller 92b is regulated within a predetermined range by the supply roller blade member 921b, the film thickness of the developer film formed on the surface of the developing roller 91b is also kept within the predetermined range. It is.

  The developer supply device 94b has a plurality of developer supply nozzles 941b arranged at equal intervals in the axial direction of the supply roller 92b. The developer supply nozzle 941b is connected to the reserve tank 87b of the liquid developer circulating device LY via a flow path R7b, and receives the supply of the liquid developer from the reserve tank 87b (see FIG. 2). The developer supply nozzle 941b supplies the liquid developer toward the portion near the nip NB between the supply roller 92b and the pumping roller 93b in the pumping roller 93b.

  The excess liquid developer supplied in the vicinity of the nip NB between the supply roller 92b and the scooping roller 93b falls downward from the scooping roller 93b in the vertical direction Z and is stored in the housing portion of the developing container 95b. The stored liquid developer is recovered in the second recovery container 83b of the liquid developer circulating device LY through the flow path R2b.

  The squeeze roller 98b has a gap (hereinafter also referred to as a “second gap”) K2 with the supply roller 92b and is disposed below the supply roller 92b. The second gap K2 is equal to or less than the gap K1 between the pumping roller 93b and the supply roller 92b, for example, 0.2 to 1.0 mm. The ratio (K1 / K2) between the first gap K1 and the second gap K2 is, for example, 1.0 to 2.0.

  The squeeze roller 98b is a roller that adjusts the film thickness of the developer film GB1 before the film thickness is regulated by the supply roller blade member 921b. The squeeze roller 98b is disposed between the pumping roller 93b and the supply roller blade member 921b in the rotation direction of the supply roller 92b. The squeeze roller 98b is rotated in the direction of the arrow (clockwise) in FIGS. That is, the squeeze roller 98b rotates in a direction opposite to the supply roller 92b at a position facing the supply roller 92b.

  The developing roller cleaning device 96b is a device that cleans the liquid developer remaining on the surface of the developing roller 91b without being supplied to the photosensitive drum 10a. The developing roller cleaning device 96b includes a developer collecting roller 963b, a collecting roller scraping blade 964b, a developing roller blade member 961b whose tip abuts on the surface of the developing roller 91b, a developer collecting unit (not shown), A discharge member 965b (see FIG. 2). The developing roller cleaning device 96b is disposed to be supported by the developing container 95b.

The developer collection roller 963b is disposed in contact with the developing roller 91b so as to face the developing roller 91b. The developer collection roller 963b is a member that collects the liquid developer remaining on the development roller 91b.
The collection roller scraping blade 964b is a member that scrapes off the liquid developer adhering to the developer collection roller 963b, and the tip thereof is disposed in contact with the developer collection roller 963b.

  The developing roller blade member 961b is a plate-like member that is disposed to face a predetermined position on the downstream side in the rotation direction of the developing roller 91b with respect to the developer collecting roller 963b. The developing roller blade member 961b is disposed so that the tip thereof is in contact with the developing roller 91b. The developing roller blade member 961b is a member for scraping off the liquid developer on the developing roller 91b (surface). The developing roller blade member 961b is a member for scraping off the liquid developer that has not been collected by the developer collecting roller 963b.

  The developer recovery unit (not shown) has an internal space for recovering the liquid developer scraped by the developing roller blade member 961b. The internal space in the developer recovery unit is connected to the second recovery container 83b by a flow path R1b (see FIG. 2).

  The discharge member 965b (see FIG. 2) is a screw-like member that conveys the liquid developer recovered by the developer recovery unit to the flow path R1b connected to the second recovery container 83b.

  The charging device 97b is disposed in the vicinity of the developing roller 91b. The charging device 97b is disposed to face the developing roller 91b. The charging device 97b is upstream of the contact portion NC between the developing roller 91b and the photosensitive drum 10b in the rotation direction of the developing roller 91b, and more than the nip portion NA between the developing roller 91b and the supply roller 92b. It is arranged so as to face the downstream part. The charging device 97b is disposed to face the developing roller 91b between the nip portion NA and the contact portion NC in the rotation direction of the developing roller 91b.

  The charging device 97b applies an electric charge (applies a voltage) to the liquid developer GB constituting the developer film GB1 formed on the developing roller 91b (surface). The charging device 97b imparts electric charge to the liquid developer GB constituting the developer film GB1, for example, by corona discharge. The charging device 97b can improve the developing efficiency in the developing device 9b.

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

  The liquid developer circulation device LY includes a first recovery container 81b, a separation / extraction device 82, a second recovery container 83b, an adjustment container 84b, a toner tank TY, a carrier tank CY, and a reserve tank 87b. The liquid developer circulating device LY is a device for reusing the liquid developer that has not been used for image formation.

  The first recovery container 81b is a container for recovering the liquid developer remaining on the surface (surface) of the photosensitive drum 10b.

  The separation / extraction device 82 is a device for separating the liquid developer in the first recovery container 81b into toner and carrier liquid. The separation and extraction device 82 is connected to the first recovery container 81b via the flow path R8b. A pump P6b is provided in the flow path R8b. The liquid developer in the first recovery container 81b is sent to the separation / extraction device 82 through the flow path R8b.

  The separation / extraction device 82 is connected to the carrier tank CY via the flow path R9b. A pump P7b is provided in the flow path R9b. The carrier liquid separated and extracted by the separation and extraction device 82 is sent to the carrier tank CY through the flow path R9b.

  The second collection container 83b is a container for collecting the liquid developer remaining in the developing device 9b without being used for image formation. The second collection container 83b is connected to the developing roller cleaning device 96b of the developing device 9b and the discharge portion 952b of the developing container 95b via the flow channel R1b and the flow channel R2b.

The flow path R1b is formed to connect the developing roller cleaning device 96b and the flow path R2b. The flow path R1b merges with the flow path R2b. The flow path R1b sends the liquid developer collected by the developing roller cleaning device 96b toward the junction with the flow path R2b.
The flow path R2b is formed so as to connect the discharge portion 952b of the developing container 95b and the second recovery container 83b. The flow path R1b joins the flow path R2b. The flow path R2b sends the liquid developer stored at the bottom of the developing container 95b to the second recovery container 83b. The flow path R2b sends the liquid developer collected by the developing roller cleaning device 96b and sent to the flow path R2b via the flow path R1b to the second collection container 83b.

  The adjustment container 84b is a container for adjusting the toner concentration of the liquid developer to a predetermined value. The adjustment container 84b is connected to the second recovery container 83b via the flow path R3b. A pump P1b is provided in the flow path R3b. The liquid developer in the second recovery container 83b is sent to the adjustment container 84b through the flow path R3b.

  The toner tank TY contains a liquid developer having a higher toner concentration than the liquid developer used in the developing device 9b. The liquid developer having a high toner concentration is used to increase the toner concentration in the adjustment container 84b. The toner tank TY is connected to the adjustment container 84b through the flow path R5b. A pump P5b is provided in the flow path R5b. The liquid developer having a high toner concentration stored in the toner tank TY is sent to the adjustment container 84b through the flow path R5b.

  The carrier tank CY stores a carrier liquid. The carrier liquid is used to lower the toner concentration in the adjustment container 84b. The carrier tank CY is connected to the adjustment container 84b via the flow path R4b. A pump P2b is provided in the flow path R4b. The carrier liquid is sent to the adjustment container 84b through the flow path R4b. A carrier tank similar to the carrier tank CY is also provided in each of the other liquid developer circulation devices LM, LC, LB (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 87b contains a liquid developer to be replenished to the developing device 9b.
The reserve tank 87b is connected to the adjustment container 84b via the flow path R6b. A pump P3b is provided in the flow path R6b. The liquid developer stored in the adjustment container 84b is sent to the reserve tank 87b through the flow path R6b.

  Further, the reserve tank 87b is connected to the toner tank TY via the flow path R10b. A pump P8b is provided in the flow path R10b. The liquid developer having a high toner concentration stored in the toner tank TY is sent to the reserve tank 87b through the flow path R10b. By supplying the liquid developer having a high toner concentration from the flow path R10b, the toner concentration of the liquid developer stored in the reserve tank 87b can be increased in a short time.

  The reserve tank 87b is connected to the carrier tank CY via the flow path R11b. A pump P9b is provided in the flow path R11b. The carrier liquid stored in the carrier tank CY is sent to the reserve tank 87b through the flow path R11b. By supplying the carrier liquid from the flow path R11b, the toner concentration of the liquid developer stored in the reserve tank 87b can be lowered in a short time.

  The reserve tank 87b is connected to the developer supply nozzle 941b via the flow path R7b. A pump P4b is provided in the flow path R7b. The liquid developer stored in the reserve tank 87b is sent to the developer supply nozzle 941b through the flow path R7b. Then, the liquid developer sent to the developer supply nozzle 941b is supplied toward the nip NB.

Next, a configuration related to the control function of the developing device 9b will be described.
The developing device 9b includes a temperature sensor 601b that measures the temperature of the liquid developer GB stored in the developing container 95b, a pumping roller rotation driving unit 602b that rotates the pumping roller 93b, and a squeeze roller as a configuration related to the control function. A squeeze roller rotation drive unit 603b that rotates and drives 98b and a roller rotation drive control unit 604b are provided.

  The roller rotation drive control unit 604b includes a pumping roller rotation drive control unit 621b that controls the pumping roller rotation drive unit 602b, and a squeeze roller rotation drive control unit 631b that controls the squeeze roller rotation drive unit 603b.

  The temperature sensor 601b is disposed in the vicinity of the bottom of the inside (container) of the developing container 95b. The temperature sensor 601b measures the temperature of the liquid developer GB stored in the developing container 95b, and outputs the measured temperature to the roller rotation drive control unit 604b.

  The pumping roller rotation drive unit 602b is directly connected to the rotation shaft 931b of the pumping roller 93b and is connected to the pumping roller rotation drive control unit 621b of the roller rotation drive control unit 604b. The pumping roller rotation drive control unit 621b sets the rotation speed of the pumping roller 93b to be equal to or higher than the rotation speed of the supply roller 92b, and changes the rotation speed of the pumping roller 93b based on the temperature of the liquid developer GB measured by the temperature sensor 601b. As described above, the pumping roller rotation driving unit 602b is controlled.

  Specifically, the pumping roller rotation drive controller 621b increases the rotational speed of the pumping roller 93b when the temperature of the liquid developer GB measured by the temperature sensor 601b is higher than a predetermined value (threshold value). In addition, the pumping roller rotation driving unit 602b is controlled. In addition, the pumping roller rotation drive control unit 621b reduces the rotation speed of the pumping roller 93b when the temperature of the liquid developer GB measured by the temperature sensor 601b is lower than a predetermined value (threshold). The pumping roller rotation driving unit 602b is controlled.

  The squeeze roller rotation drive unit 603b is directly connected to the rotation shaft 981b of the squeeze roller 98b, and is connected to the squeeze roller rotation drive control unit 631b of the roller rotation drive control unit 604b. The squeeze roller rotation drive control unit 631b controls the squeeze roller rotation drive unit 603b so as to change the rotation speed of the squeeze roller 98b in accordance with the rotation speed of the pumping roller 93b.

  Specifically, the squeeze roller rotation drive control unit 631b controls the squeeze roller rotation drive unit 603b so as to decrease the rotation speed of the squeeze roller 98b when the rotation speed of the scoop roller 93b is increased. Further, the squeeze roller rotation drive control unit 631b controls the squeeze roller rotation drive unit 603b so as to increase the rotation speed of the squeeze roller 98b when the rotation speed of the pumping roller 93b is decreased.

  By the way, controlling the pumping roller rotation driving unit 602b so as to change the rotation speed of the pumping roller 93b based on the temperature T1 of the liquid developer GB measured by the temperature sensor 601b means that the viscosity of the liquid developer GB is high. This is to adapt to the so-called temperature dependence of the viscosity, which varies depending on the temperature of the liquid developer GB.

More specifically, as shown in FIG. 5, the viscosity (mPa · s) of the liquid developer GB has a temperature dependency that gradually decreases as the temperature (° C.) of the liquid developer GB increases.
The viscosity (residual viscosity) was measured with a Physica MCR-301 viscoelasticity measuring device manufactured by Anton Paar.

  The peripheral speed of the developing roller 91b is always equal to the peripheral speed of the photosensitive drum 10a. On the other hand, the peripheral speed of the supply roller 92b is variable. The peripheral speed of the pumping roller 93b, that is, the peripheral speed of the pumping roller 93b / the peripheral speed (peripheral speed ratio) of the supply roller 92b is variable. The peripheral speed of the drawing roller 93b is, for example, 400 to 500 mm / sec.

  The peripheral speed ratio (speed on the peripheral surface (surface)) between the drawing roller 93b and the supply roller 92b, which is set according to the temperature and viscosity of the liquid developer, is, for example, as shown in [Table 1] below.

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 formation instruction from a PC (not shown) connected to the color printer 1. The color printer 1 forms a toner image of each color using the image forming units FY, FM, FC, and FB based on the image information included in the image data.

  Specifically, the color printer 1 controls various operation units based on image information included in the image data 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 uses toner images (color toner images formed on the surfaces of the photosensitive drums 10a, 10b, 10c, and 10d) formed by the image forming units FY, FM, FC, and FB, and 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 also separates the separation roller pair 33. Thus, the paper T is sent to the paper transport unit 6 one by one.
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) onto a discharge tray 72 formed on the upper surface portion of the color printer 1 by the discharge roller pair 71.

Next, the operation of the developing device 9b will be described.
When the image forming operation of the color printer 1 is started, the pump P4b that has received the liquid developer supply start instruction starts liquid supply (supply) of the liquid developer. As a result, the developer supply device 94b starts supplying the liquid developer to the vicinity of the nip portion NB of the pumping roller 93b with the supply roller 92b. The supplied liquid developer is a liquid developer whose toner concentration is adjusted to a predetermined value by the adjustment container 84b of the liquid developer circulation device LY.

  A part of the liquid developer is transferred directly from the surface of the pumping roller 93b to the surface (spiral groove) of the supply roller 92b, and is stored in the accommodating portion of the developing container 95b through the surface of the pumping roller 93b. . The stored liquid developer GB is pumped up by the pumping roller 93b and transferred to the surface (spiral groove) of the supply roller 92b to form the developer film GB1. The developer film GB1 formed on the surface of the supply roller 92b is transferred to and held by the developing roller 91b.

  Here, the developer film held on the developing roller 91b is regulated to a constant film thickness by the supply roller blade member 921b. Specifically, when the supply amount from the developer supply device 94b is small (less than a predetermined amount), the developer film is not regulated by the supply roller blade member 921b, and the film thickness increases as the supply amount increases. Become thicker. When the supply amount from the developer supply device 94b is large (a predetermined amount or more), the developer film is regulated by the supply roller blade member 921b and the film thickness becomes constant. In this case, the developer supply device 94b supplies the liquid developer in excess by the amount of the liquid developer scraped off by the supply roller blade member 921b.

  Subsequently, the color printer 1 instructs the charging device 97b to start charge application processing (for example, corona discharge). By the charge imparting process, the toner in the liquid developer constituting the developer film is moved to the surface side of the developer film. As a result, the developing device 9b supplies toner to the electrostatic latent image formed on the photosensitive drum 10b. The liquid developer remaining on the developing roller 91b without being supplied to the photosensitive drum 10b is scraped off by the developing roller blade member 961b described above, and is stored in the developer collecting section (not shown) of the developing roller cleaning device 96b. Collected. The liquid developer stored in the developer recovery unit is recovered into the second recovery container 83b through the flow path R1b (see FIG. 2).

  The liquid developer that has not been supplied to the developing roller 91b falls downward from the scooping roller 93b and is stored in the housing portion of the developing container 95b. The liquid developer stored in the housing portion of the developing container 95b is recovered into the second recovery container 83b through the flow path R2b (see FIG. 2). Further, the liquid developer remaining on the surface of the photosensitive drum 10b is collected in the first collection container 81b by the developing roller cleaning device 96b.

  The liquid developer collected in the first collection container 81b and the second collection container 83b is circulated by the liquid developer circulation device LY, and the toner density is adjusted to a desired density. Then, the liquid developer whose toner concentration is adjusted to a predetermined concentration is supplied again to the developing device 9b by the developer supplying device 94b.

Next, with reference to FIG. 2, the liquid developer circulation will be described focusing on the operation of the liquid developer circulation device LY.
First, the liquid developer supplied from the developer supply device 94b is supplied to the developing roller 91b via the supply roller 92b. Part of the liquid developer (part of toner) supplied to the developing roller 91b is supplied to the photosensitive drum 10b. The liquid developer remaining on the developing roller 91b without being supplied to the photosensitive drum 10b is scraped off by the developing roller blade member 961b. The liquid developer thus scraped off is sent to the second recovery container 83b through the flow path R1b and the flow path R2b.

The liquid developer supplied from the developer supply device 94b, which was not supplied to the supply roller 92b, and the liquid developer supplied to the supply roller 92b but scraped off by the supply roller blade member 921b, , Temporarily stored in the developing container 95b.
The liquid developer temporarily stored in the developing container 95b is sent to the second recovery container 83b through the flow path R2b.

  The liquid developer stored in the second recovery container 83b is supplied to the adjustment container 84b through the flow path R3b at a predetermined timing.

Further, the liquid developer remaining on the photosensitive drum 10b without being transferred to the intermediate transfer belt 21 is scraped off by the cleaning blade 27b. The liquid developer thus scraped off is accommodated in the first recovery container 81b.
The liquid developer recovered in the first recovery container 81b is sent to the separation / extraction device 82 through the flow path R8b.

  The liquid developer sent to the separation and extraction device 82 is subjected to a separation and extraction process in which the liquid developer is separated into toner and carrier liquid. The carrier liquid extracted in the separation and extraction device 82 is sent to the carrier tank CY through the flow path R9b.

  In the adjustment container 84b, the toner concentration of the liquid developer is adjusted based on the toner concentration of the liquid developer detected by a solid content concentration detection unit (not shown). Specifically, when the toner concentration is high, the carrier liquid is supplied from the carrier tank CY to the adjustment container 84b through the flow path R4b. When the toner concentration is low, the liquid developer having a high toner concentration is supplied from the toner tank TY to the adjustment container 84b through the flow path R5b.

The liquid developer whose toner concentration is adjusted in the adjustment container 84b is sent to the reserve tank 87b through the flow path R6b as necessary.
The liquid developer stored in the reserve tank 87b is sent to the developer supply nozzle 941b through the flow path R7b by the action of the pump P4b.
Then, the liquid developer is supplied from the developer supply nozzle 941b to the developing device 9b and used for image formation.

  Next, a characteristic operation of the developing device 9b in the present embodiment will be described. FIG. 6 is a flowchart for explaining the operation of the developing device 9b.

  When the image forming operation of the color printer 1 is started and an electrostatic latent image is formed on the surface of the photosensitive drum 10a, the pumping roller 93b of the developing device 9b rotates in step ST1. Thereby, the liquid developer GB stored in the developing container 95b is pumped up on the surface of the pumping roller 93b. At this time, since the rotational speed of the pumping roller 93b is equal to or higher than the rotational speed of the supply roller 92b, a sufficient amount of the liquid developer GB is pumped into the gap K1 between the pumping roller 93b and the supply roller 92b.

  In step ST2, when the liquid developer GB is pumped by the pumping roller 93b, the temperature of the liquid developer GB stored in the developing container 95b is measured by the temperature sensor 601b.

In step ST3, the roller rotation drive control unit 604b compares the temperature T1 of the liquid developer GB measured by the temperature sensor 601b with a predetermined temperature T0.
As a result of the comparison, if the temperature T1 of the liquid developer GB is higher than the predetermined temperature T0 (T1 ≧ T0) (YES), in step ST4, the pumping roller rotation drive control unit 621b of the roller rotation drive control unit 604b is The pumping roller rotation driving unit 602b is controlled so as to increase the rotational speed of the pumping roller 93b.

  In step ST5, the squeeze roller rotation drive control unit 631b of the roller rotation drive control unit 604b controls the squeeze roller rotation drive unit 603b so as to reduce the rotation speed of the squeeze roller 98b.

  On the other hand, when the temperature T1 of the liquid developer GB measured by the temperature sensor 601b is lower than the predetermined temperature T0 (T1 <T0) (NO), in step ST6, the pumping roller rotation of the roller rotation drive control unit 604b. The drive control unit 621b controls the pumping roller rotation driving unit 602b so as to slow down the rotation speed of the pumping roller 93b.

  In step ST7, the squeeze roller rotation drive control unit 631b of the roller rotation drive control unit 604b controls the squeeze roller rotation drive unit 603b so as to increase the rotation speed of the squeeze roller 98b.

  As described above, in this embodiment, the relationship between the temperature and the viscosity of the liquid developer GB is grasped, and the peripheral speed ratio between the pumping roller and the developer supply roller is controlled based on the measured temperature.

  For example, in the case where the temperature dependency of the liquid developer GB is not taken into account, when the temperature (° C.) of the liquid developer GB increases and the viscosity decreases, the pumping amount of the liquid developer GB by the pumping roller 93b decreases. Thus, insufficient supply of the liquid developer GB to the supply roller 92b is likely to occur.

  On the other hand, in this embodiment, when the temperature T1 of the liquid developer GB measured by the temperature sensor 601b is higher than the predetermined temperature T0 (T1 ≧ T0), the rotation speed of the pumping roller 93b is increased. In addition, when the temperature T1 of the liquid developer GB measured by the temperature sensor 601b is lower than the predetermined temperature T0 (T1 <T0), the liquid developer GB is set so as to reduce the rotation speed of the pumping roller 93b. The rotational speed of the pumping roller 93b is changed and controlled in accordance with the temperature of. As a result, the pumping amount of the liquid developer GB by the pumping roller 93b can be kept substantially constant regardless of changes in the temperature (viscosity) of the liquid developer GB.

  In step ST8, the liquid developer GB pumped into the gap K1 by the pumping roller 93b is transferred to the supply roller 92b rotating in the same direction as the pumping roller 93b at the position facing the pumping roller 93b. A developer film GB1 is formed on the surface of the roller 92b.

  In step ST9, the film thickness of the developer film GB1 formed on the surface of the supply roller 92b as the supply roller 92b rotates is adjusted by the squeeze roller 98b. The film thickness of the developer film GB1 on the surface of the supply roller 92b adjusted by the squeeze roller 98b is substantially equal to the size of the second gap K2 between the supply roller 92b and the squeeze roller 98b.

  In step ST10, the developer film GB1 whose film thickness on the surface of the supply roller 92b is adjusted is regulated by the supply roller blade member 921b so that it does not become thicker than a predetermined thickness.

  In step ST11, the developer film GB1 formed on the surface of the supply roller 92b so as to have a constant film thickness is transferred to the development roller 91b as the supply roller 92b rotates, and the developer is transferred to the surface of the development roller 91b. The membrane is retained.

  In step ST12, the developer film held on the surface of the developing roller 91b is moved to a position close to the surface of the photosensitive drum 10a as the developing roller 91b rotates. At this time, the toner in the liquid developer film is moved to the surface side of the developing roller 91b by the electric field (same polarity as the charging polarity of the toner) generated by the charging device 97b. The toner is supplied from the developing roller 91b to the electrostatic latent image formed on the photosensitive drum 10a.

  In step ST13, the liquid developer remaining on the surface of the developing roller 91b without being supplied to the photosensitive drum 10a is collected by the developer collecting roller 963b of the developing roller cleaning device 96b and scraped by the developing roller blade member 961b. Taken and collected.

According to the developing device of the present embodiment configured as described above, for example, the following effects are exhibited.
In the present embodiment, the rotational speed of the drawing roller 93b is set to be equal to or higher than the rotational speed of the supply roller 92b.
Therefore, by the rotation of the pumping roller 93b, it is possible to sufficiently secure the pumping amount of the liquid developer GB into the first gap K1 at the position where the pumping roller 93b and the supply roller 92b face each other. As a result, the shortage of supply of the liquid developer GB to the supply roller 92b can be suppressed.

Further, in the present embodiment, the supply roller 92b rotates in the same direction at a position facing the pumping roller 93b.
Therefore, the liquid developer GB pumped into the gap K1 by the pumping roller 93b can be reliably and smoothly transferred to the supply roller 92b side, and a developer film having a constant regulated film thickness can be formed on the surface. . As a result, the transfer of the developer film from the supply roller 92b to the developing roller 91b can be ensured, and the occurrence of a defect such as image loss due to insufficient supply of the developer can be suppressed.

In this embodiment, the temperature of the liquid developer GB is measured, and when the measured temperature of the liquid developer GB is high, the rotational speed of the pumping roller 93b is increased, and the temperature of the liquid developer GB is low. In this case, the rotational speed of the pumping roller 93b is controlled to be changed based on the temperature of the liquid developer GB so as to slow down the rotational speed of the pumping roller 93b.
Therefore, even if the temperature of the liquid developer GB varies according to the ambient temperature around the printer 1 and the viscosity of the liquid developer GB changes, the pumping amount of the liquid developer GB by the pumping roller 93b becomes substantially constant. Can keep.

That is, when the temperature of the liquid developer GB increases and the viscosity decreases, the rotational speed of the pumping roller 93b is increased to increase the pumping amount of the liquid developer by the pumping roller 93b. When the temperature of GB decreases and the viscosity increases, the rotational speed of the drawing roller 93b is slowed down to reduce the amount of liquid developer pumped by the pumping roller 93b, whereby the temperature and viscosity of the liquid developer GB are reduced. Regardless of the change, the pumping amount of the liquid developer GB by the pumping roller 93b can be kept substantially constant.
Accordingly, in spite of fluctuations in the environmental temperature, defects such as missing images due to insufficient supply of the liquid developer GB from the pumping roller 93b through the supply roller 92b to the developing roller 91b, or image blur due to excessive supply of the liquid developer GB, etc. Can be suppressed.

Furthermore, in this embodiment, when the rotational speed of the scoop roller 93b is increased, the rotational speed of the squeeze roller 98b is decreased, and when the rotational speed of the scoop roller 93b is decreased, the rotational speed of the squeeze roller 98b is increased. As described above, the rotation speed of the squeeze roller 98b is controlled in accordance with the change in the rotation speed of the pumping roller 93b.
Therefore, the adjustment of the film thickness by the squeeze roller 98b for the developer film GB1 transferred from the pumping roller 93b and formed on the surface of the supply roller 92b can be appropriately performed according to the viscosity of the developer film GB1. As a result, the regulation of the film thickness by the supply roller blade member 921b after the adjustment of the film thickness of the developer film GB1 can be reliably and smoothly performed in a state where the load applied to the supply roller blade member 921b is small.

  In addition, according to the present embodiment, an image forming apparatus including the developing device that exhibits the above-described effects is provided.

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, as the developer supply device 94b, in the above-described embodiment, the liquid developer GB whose density has been adjusted is supplied to the surface of the pumping roller 93b. However, the developer supplying device 94b is not limited to this and is separated from the pumping roller 93b. Alternatively, the toner may be supplied directly to the housing portion of the developing container 95b. That is, the entire amount of the liquid developer GB can be supplied to the supply roller 92b by being pumped by the pumping roller 93b.

  In the above-described embodiment, the supply roller 92b rotates in the same direction as the pumping roller 93b at the position facing the pumping roller 93b. However, the supply roller 92b is not limited to this, and may rotate in the direction opposite to the pumping roller 93b. Good.

In the present embodiment, the color printer 1 is described as an example of the image forming apparatus, but the present invention is not limited to this. The image forming apparatus may be, for example, a color copying machine, a monochrome copying machine, a monochrome printer, a facsimile, or a complex machine thereof.
The sheet-shaped transfer material is not limited to paper, and may be, for example, a film sheet.

  DESCRIPTION OF SYMBOLS 1 ... Color printer (image forming apparatus), 2 ... Image forming part, 5 ... Fixing part, 9a, 9b, 9c, 9d ... Developing apparatus, 91b ... Developing roller, 92b ... Supply roller (Developer) Supply roller), 921b... Supply roller blade member (regulating member), 93b... Pumping roller, 95b... Development container (liquid developer storage unit), 98b .. squeeze roller, 10a, 10b, 10c, 10d. Photosensitive drum 2 (image carrier), 601b: temperature sensor, 602b: pumping roller rotation drive unit, 603b: squeeze roller rotation drive unit, 621b: pumping roller rotation drive control unit, 631b: squeeze roller rotation Drive control unit, GB ... Liquid developer, GB1 ... Developer film, K1 ... First gap (gap), K2 ... Second gap (gap), T ... Paper (transferred) )

Claims (2)

A developing device for supplying a liquid developer to an image carrier,
A liquid developer reservoir for storing the liquid developer;
A pumping roller for pumping up the liquid developer stored in the liquid developer storage unit;
A developer supply roller that is disposed to face the scooping roller with a gap, the liquid developer scooped up by the scooping roller is transferred, and a developer film is formed on the surface;
A regulating member that is disposed close to or in contact with the developer supply roller and regulates the film thickness of the developer film formed on the surface of the developer supply roller so as not to be thicker than a predetermined thickness;
A developing roller disposed opposite to and in contact with the developer supply roller, the developer film formed on the surface of the developer supply roller being transferred, and holding the developer film on the surface;
A temperature sensor for measuring the temperature of the liquid developer stored in the liquid developer storage unit;
A pumping roller rotation drive unit for rotating the pumping roller;
The pumping roller rotational drive so that the rotational speed of the pumping roller is equal to or higher than the rotational speed of the developer supply roller and the rotational speed of the pumping roller is changed based on the temperature of the liquid developer measured by the temperature sensor. A pumping roller rotation drive control unit for controlling the unit;
The developer supply roller is disposed to face the gap with a gap, and is disposed between the pumping roller and the regulating member in the rotation direction of the developer supply roller, and the film thickness is regulated by the regulating member. A squeeze roller for adjusting the film thickness of the previous developer film;
A squeeze roller rotation drive unit that rotationally drives the squeeze roller;
The squeeze roller is rotated so that the rotation speed of the squeeze roller is decreased when the rotation speed of the pumping roller is increased, and the rotation speed of the squeeze roller is increased when the rotation speed of the pumping roller is decreased. A squeeze roller rotation drive control unit for controlling the drive unit ,
The developer supply roller rotates in the same direction as the scooping roller at a position facing the scooping roller,
The gap between the developer supply roller and the squeeze roller is equal to or less than the gap between the pumping roller and the developer supply roller.
The squeeze roller rotates in a direction opposite to the rotation direction of the developer supply roller at a position facing the developer supply roller,
When the temperature of the liquid developer measured by the temperature sensor is high, the pumping roller rotation drive control unit increases the rotation speed of the pumping roller, and the temperature of the liquid developer measured by the temperature sensor is low. In such a case, the developing device controls the pumping roller rotation driving unit so as to reduce the rotation speed of the pumping roller . A developing device according to claim 1 ;
An image forming unit having the image carrier, wherein the image forming unit forms a toner image on a sheet-like transfer material;
An image forming apparatus comprising: a fixing unit that fixes the toner image formed on the transfer material by the image forming unit.

Images