JP5287530B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device for carrying and transporting a thin layer of a liquid developer in which toner is dispersed in a solvent to the surface of a developing roller to develop a latent image formed on an image carrier, and an image including the developing device. The present invention relates to a forming apparatus.

  2. Description of the Related Art An electrophotographic image forming apparatus that forms an electrostatic latent image on a photoconductor (photosensitive drum), adheres toner to the image, and transfers and fixes the image on paper or the like is widely used. In particular, in an image forming apparatus that requires higher image quality and higher resolution, such as an office printer for large-scale printing and an on-demand printing apparatus, a liquid developer that uses relatively small toner particles and that does not easily disturb toner images is used. Wet development methods are being used.

  In recent years, wet using a high-viscosity, high-concentration liquid developer, which is formed by dispersing toner as a solid content composed of resin and pigment in an insulating liquid “carrier liquid” such as silicon oil at a high concentration. Development devices and image forming apparatuses have been proposed.

  When developing using this liquid developer, a thin layer of developer is formed on a developer carrier such as a developing roller, and the thinned developer is brought into contact with the photoreceptor. It is common to develop.

  In the usual wet development method, a thin layer of liquid developer is formed on the developing roller by a thin layer forming means such as restriction of the developer transport amount by the blade, and the upstream side of the developer area in the developer transport direction The toner in the developer thin layer is charged by the charging means provided in the developing unit, and the latent image of the opposing photoconductor is developed in the development area.

  However, in general, the amount of toner developed on the photosensitive member is determined by the amount of toner on the developing roller. Therefore, when the amount of liquid developer on the developing roller changes, the amount of toner on the photosensitive member changes. The image density on a certain paper changes and becomes a problem.

  Here, the temperature of the liquid developer is one of the major factors affecting the amount of toner on the developing roller, that is, the amount of liquid developer.

  For example, in the formation of a thin layer of the liquid developer, the amount of developer on the developing roller changes when the temperature of the liquid developer changes. Specifically, when the temperature of the developer is low, the amount of developer on the developing roller is large, and when the temperature is high, the amount of developer is small.

  The temperature of the liquid developer varies depending on the temperature around the developing device, but further rises as the roller generates heat by driving the developing device. When the temperature of the developer increases due to continuous driving, the amount of developer on the developing roller decreases.

  For this reason, as a developing device, a technique (see Patent Documents 1 to 4) that adjusts the amount of developer supplied to the developing roller according to the temperature of the liquid developer has been developed.

  Patent Documents 1 to 4 each disclose a technique in which the number of rotations of the supply roller is variable depending on the temperature in the apparatus and the temperature of the liquid developer, and the developer supply amount to the development roller is changed.

  Further, the temperature change of the developer during the continuous driving is large in the initial stage, and the change amount becomes small with time. Along with this, the change in the developer amount on the developing roller also decreases. Therefore, it is preferable to use the developer after the temperature of the developer on the developing roller is stabilized and the developer amount is stabilized.

  For this reason, as a developing device, a technique for providing a warm-up time before development (see Patent Documents 5 and 6) has been developed.

  In the technique described in Patent Document 5, when the temperature of the supply roller that supplies the developer to the developing roller during printing is high, the speed of the supply roller is increased to control the amount of developer, but the temperature of the supply roller is low. In some cases, the warm-up operation is performed.

  In the technique described in Patent Document 6, the temperature of the developer is detected at the time of printing, and the timing of the warm-up operation is adjusted according to the temperature of the developer by controlling the print start timing. .

JP-A-11-143243 JP 2001-255747 A JP-A-2005-352218 JP 2006-11292 A JP-A-2005-31406 Japanese Patent Laid-Open No. 5-289525

  As described above, in a developing device using a liquid developer, one of the major factors that fluctuates the amount of developer on the developing roller is the temperature of the liquid developer. On the other hand, techniques for adjusting the developer supply amount according to the temperature have been proposed.

  However, in the techniques disclosed in Patent Documents 1 to 4, since the temperature of the liquid developer itself is not controlled, it is necessary to deal with a large temperature fluctuation, and the adjustment range of the developer supply amount becomes too large. In some cases, it is difficult to adjust the accuracy appropriately.

  There has also been proposed a technique for performing development after performing a warming-up operation to increase and stabilize the temperature of the liquid developer.

  However, even with the techniques disclosed in Patent Documents 5 and 6, the temperature of the liquid developer itself is not directly controlled, and the warming-up operation is merely to drive the developing device and wait for the temperature to rise.

  It takes a long time to stabilize the temperature of the liquid developer on the developing roller and stabilize the amount of developer, and it is desirable to shorten the stabilization time (warming up time).

  The present invention has been made in view of the above technical problems.

  An object of the present invention is to stabilize the temperature of a liquid developer on a developing roller and stabilize the amount of developer by a warm-up operation in a shorter time without complicating the apparatus configuration in a developing apparatus using a liquid developer. It is an object of the present invention to provide a developing device that can be converted into an image forming apparatus and an image forming apparatus including the developing device.

  In order to solve the above problems, the present invention has the following features.

1. A developing roller for carrying and transporting on the surface a thin layer of a liquid developer in which toner is dispersed in a solvent, and developing a latent image formed on the image carrier;
A developing device having a supply roller that rotates in contact with the developing roller and supplies the liquid developer to the developing roller;
An image forming mode for performing development for normal image formation;
In a warm-up mode in which a preliminary operation is performed when starting the development,
Control means for controlling the driving of the developing roller and the supply roller,
The control means controls the driving of the developing roller and the supply roller in the warm-up mode so that the amount of heat generated by driving the developing roller and the supply roller is larger than that in the image forming mode. A developing device.

2. The control means includes
2. The developing device according to claim 1, wherein in the warming-up mode, the rotation of the supply roller is controlled to be slower than in the image forming mode.

3. The control means includes
3. The developing device according to 1 or 2, wherein in the warm-up mode, control is performed so that a pressure contact force between the developing roller and the supply roller is increased as compared with the image forming mode.

4). Developer temperature detecting means for detecting the temperature of the liquid developer on the developing roller or the supply roller;
The control means includes
In the warm-up mode, based on the temperature of the liquid developer detected by the developer temperature detecting means, the warm-up mode is terminated, and the image forming mode is entered.
In the image forming mode, the development amount is adjusted so that the supply amount of the liquid developer from the supply roller to the development roller is adjusted based on the temperature of the liquid developer detected by the developer temperature detection unit. The developing device according to any one of 1 to 3, wherein driving of the roller and the supply roller is controlled.

5. A developing roller for carrying and transporting on the surface a thin layer of a liquid developer in which toner is dispersed in a solvent, and developing a latent image formed on the image carrier;
A regulating device that contacts the developing roller and regulates the amount of the liquid developer on the developing roller,
An image forming mode for performing development for normal image formation;
In a warm-up mode in which a preliminary operation is performed when starting the development,
Control means for controlling the pressing force of the restricting means to the developing roller,
In the warm-up mode, the control unit controls the pressure-contact force of the regulating unit with respect to the developing roller so that the amount of heat generated by the regulating unit with respect to the developing roller is larger than that in the image forming mode. A developing device.

6). An image carrier;
A developing device that develops the electrostatic latent image formed on the image carrier using a liquid developer,
The image forming apparatus, wherein the developing device is the developing device according to any one of 1 to 5 above.

  According to the developing device and the image forming apparatus including the developing device according to the present invention, in the developing device using the liquid developer, the amount of heat generated by driving the device is larger in the warm-up mode than in the image forming mode. The driving conditions are controlled. Thus, the temperature of the liquid developer on the developing roller can be stabilized and the amount of developer can be stabilized by a warm-up operation in a shorter time without complicating the apparatus configuration.

1 is a cross-sectional view illustrating an overall configuration example of an image forming apparatus according to the present invention and a schematic configuration example of a developing device according to a first embodiment. It is a graph which shows the relationship between developing apparatus drive time and the temperature of the liquid developer on a supply roller. 6 is a graph showing the relationship between the temperature of a liquid developer on a supply roller and the amount of developer on a developing roller. It is a graph which shows the relationship between the developing device drive time and the temperature of the liquid developer on the supply roller when the roller drive condition is changed. It is sectional drawing which shows the one part structural example of the developing device which concerns on 2nd Embodiment. It is sectional drawing which shows the schematic structural example of the developing device which concerns on 3rd Embodiment. It is sectional drawing which shows the schematic structural example of the developing device which concerns on 4th Embodiment.

  Embodiments of a developing device and an image forming apparatus according to the present invention will be described with reference to the drawings.

  2. Description of the Related Art Wet image forming apparatuses that develop using a thin layer of a liquid developer are used in copying machines, simple printing machines, printers, and the like. In general, an electrophotographic image forming process is commonly used for these. First, the electrophotographic wet image forming apparatus will be described with reference to FIG. 1, and the configuration and functional operation of the developing apparatus used there will be described.

(Example of overall configuration and operation of image forming apparatus)
FIG. 1 shows an example of the overall configuration of the image forming apparatus according to the present embodiment. The overall configuration of the image forming apparatus will be described with reference to FIG. However, only the components related to the image forming process are shown. The components related to the feeding, transporting, and discharging of the recording medium are omitted.

  The image forming apparatus of FIG. 1 includes a photosensitive drum 1 as an image carrier, a charging device 2, an exposure device 3, a wet developing device 4, a transfer roller 5, a cleaning device 6, and a charge eliminating device 7.

  In FIG. 1, only one wet developing device 4 is disposed, but a plurality of wet developing devices 4 may be disposed for color image formation. The color development method, the presence / absence of intermediate transfer, and the like may be set arbitrarily, and an arbitrary arrangement configuration corresponding to the method can be taken.

  The photosensitive drum 1 has a cylindrical shape with a photosensitive layer (not shown) formed on the surface thereof, and rotates in the direction of arrow a in FIG. A cleaning device 6, a charge removal device 7, a charging device 2, an exposure device 3, a wet developing device 4, and a transfer roller 5 are sequentially arranged on the outer periphery of the photosensitive drum 1 along the rotation direction of the photosensitive drum 1. ing.

  The charging device 2 charges the surface of the photosensitive drum 1 to a predetermined potential.

  The exposure device 3 irradiates the surface of the photosensitive drum 1 with light to lower the charge level in the irradiated area, thereby forming an electrostatic latent image.

  The wet developing device 4 develops the latent image formed on the photosensitive drum 1. That is, the liquid developer is conveyed to the development area of the photosensitive drum 1, and the toner contained in the liquid developer is supplied to the electrostatic latent image on the surface of the photosensitive drum 1 to form a toner image.

  In the developing process, a developing bias voltage having the same polarity as the toner is applied from the power source 48 to the developing roller 41 of the wet developing device 4. Similarly, a difference in electric field is formed in balance with the potential of the latent image on the photosensitive drum 1 having the same polarity as the toner, and the toner in the developer is electrostatically adsorbed on the photosensitive drum 1 in accordance with the latent image. The latent image on 1 is developed.

  The transfer roller 5 is disposed so as to face the photosensitive drum 1 with the recording medium 9 interposed therebetween, and rotates in contact with the recording roller 9 via the recording medium 9. Transfer from the photosensitive drum 1 to the recording medium 9 is performed at the nip portion between the transfer roller 5 and the photosensitive drum 1.

  The recording medium 9 is conveyed in the direction of arrow d to the transfer position in accordance with the transfer timing.

  In the transfer process, a transfer bias voltage having a polarity opposite to that of toner is applied to the transfer roller 5 from a power source (not shown). As a result, an electric field is formed between the transfer roller 5 and the photosensitive drum 1, and the toner image on the photosensitive drum 1 is transferred onto the recording medium 9 that has passed between the transfer roller 5 and the photosensitive drum 1. It is electrostatically attracted and transferred onto the recording medium 9.

  The recording medium 9 onto which the toner image has been transferred is conveyed to a fixing unit (not shown) and is pressurized at a high temperature at the fixing unit, so that the toner forming the toner image is fused and fixed to the recording medium 9.

  When the toner image is transferred to the recording medium 9, the cleaning device 6 removes the residual toner on the photosensitive drum 1, the neutralization device 7 removes the residual potential on the surface of the photosensitive member 1, and the next image formation is performed. .

(Developer composition)
The liquid developer 8 used for development will be described. In the liquid developer, colored toner particles are dispersed at a high concentration in a carrier liquid which is a solvent. In addition, additives such as a dispersant and a charge control agent may be appropriately selected and added to the liquid developer.

  As the carrier liquid, an insulating, non-volatile solvent at room temperature is used. Examples of the non-volatile solvent include silicon oil, mineral oil, paraffin oil, and the like.

  The toner particles are mainly composed of a resin and a pigment or dye for coloring. The resin has a function of uniformly dispersing pigments and dyes in the resin and a function as a binder when being fixed to the recording material.

  Examples of the resin that can be used include thermoplastic resins such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, and polyurethane resin. A plurality of these resins may be mixed and used.

  Commonly commercially available pigments and dyes used for coloring the toner can also be used. For example, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, etc. can be used as the pigment. Solvent red 27, acid blue 9, or the like can be used as the dye.

  As a method for adjusting the liquid developer, it can be adjusted based on a commonly used technique. For example, the resin and the pigment are melt kneaded using a pressure kneader, a roll mill or the like at a predetermined blending ratio and uniformly dispersed, and the obtained dispersion is finely pulverized by, for example, a jet mill. Further, by classifying the obtained fine powder with, for example, an air classifier, a colored toner having a predetermined particle diameter can be obtained.

  Subsequently, the obtained toner is mixed with an insulating liquid as a carrier liquid at a predetermined blending ratio. This mixture can be uniformly dispersed by a dispersing means such as a ball mill to obtain a liquid developer.

  The volume average particle diameter of the toner is suitably in the range of 0.1 μm or more and 5 μm or less. When the average particle diameter of the toner is less than 0.1 μm, the developability is greatly lowered. On the other hand, when the average particle diameter exceeds 5 μm, the quality of the image is deteriorated.

  An appropriate ratio of the toner particles to the liquid developer is about 10 to 50% by mass. If it is less than 10%, toner particles are liable to settle, and there is a problem with the stability over time during long-term storage. Further, in order to obtain a required image density, it is necessary to consume a large amount of developer, which causes a problem in cost. If it exceeds 50%, the viscosity of the liquid developer becomes too high, making it difficult to manufacture and handle.

  The viscosity of the liquid developer is preferably from 0.1 mPa · s to 10,000 mPa · s at 25 ° C. If it exceeds 10,000 mPa · s, handling of the developer such as stirring and feeding becomes difficult, and the burden on the apparatus for obtaining a uniform liquid developer is large.

(First Embodiment: Configuration and Operation of Developing Device)
As a first embodiment of the wet developing apparatus according to the present invention, the configuration and operation of the developing apparatus 4 in FIG. 1 will be described.

  The developer tank 44 contains the liquid developer 8. As described above, in the liquid developer 8, toner particles are dispersed in a carrier liquid that is a solvent.

  The coarsely pulverized toner and liquid developer used in the present embodiment were manufactured as follows.

  After fully mixing 100 parts of polyester resin and 15 parts of copper phthalocyanine with a Henschel mixer, melt kneading is performed using a co-rotating twin screw extruder with a heating temperature in the roll of 100 ° C., and the resulting mixture is cooled and coarsely pulverized. Thus, a coarsely pulverized toner was obtained.

  75 parts of IPS2028 (manufactured by Idemitsu Kosan Co., Ltd.), 25 parts of coarsely pulverized toner and 0.8 part of V216 (manufactured by ISP) as a dispersant were mixed, and wet pulverized with a sand mill for 4 days to obtain a liquid developer. The particle size at that time was 2.0 μm. The particle size was measured with a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation).

  The configuration and operation of the developing device 4 will be described.

  A part of the pumping roller 43 is immersed in the liquid developer 8 in the developer tank 44, and pumps up the liquid developer 8 by rotation in the direction of arrow f.

  The scooping roller 43 is provided with a regulating member 45 for regulating the developer 8 to a constant thickness, and the thickness of the liquid developer 8 pumped up is constant.

  By using a metal roller (anilox roll) having a concave portion on the surface as the drawing roller 43, the amount of developer can be accurately regulated.

  After being regulated to a certain amount by the regulating member 45, the liquid developer 8 on the drawing roller 43 is conveyed to the nip portion with the supply roller 42.

  The supply roller 42 rotates in the same direction as the pumping roller 43 (in the direction of arrow e) at the nip portion, and the liquid developer 8 is delivered to the supply roller 42.

  The pumping roller 43 is driven by the supply roller 42 and is not provided with a driving device.

  On the other hand, the supply roller 42 rotates in the direction opposite to the rotation direction of the developing roller (the direction of the arrow b) at the nip portion with the developing roller 41 as the developer carrying member.

  By doing so, most of the liquid developer 8 on the supply roller 42 is transferred to the developing roller 41, and the efficiency is high. Further, the thin layer of the liquid developer 8 on the developing roller 41 becomes uniform.

  In this configuration, when the rotation speed of the supply roller 42 is changed, the developer supply amount per unit time to the developing roller 41 is changed, and the developer amount on the developing roller 41 can be controlled. Since the pumping roller 43 is driven by the supply roller 42, the rotational speed of the pumping roller 43 is similarly changed by changing the rotational speed of the supply roller 42.

  Specifically, when the rotation speed of the supply roller 42 is increased, the amount of the liquid developer 8 on the developing roller 41 is increased.

  The high-viscosity liquid developer 8 adheres to the surface of the developing roller 41 with its adhesive force, and is transported in a state where a developer thin layer is formed.

  As the developing roller 41, a low hardness rubber roller is used.

  The developing roller 41 also rotates in contact with the photosensitive drum 1 that is an image carrier, and a thin layer of the developer 8 conveyed to the nip portion with the photosensitive drum 1, that is, the developing region, is the photosensitive drum 1. The latent image above will be developed.

  Further, since toner particles and a dispersion medium that remain without being developed exist on the surface of the developing roller 41 after passing through the developing region, a cleaning blade 46 is provided to remove them.

(Relationship between development device drive and liquid developer temperature)
FIG. 2 shows the relationship between the developing device drive time (min) and the temperature (° C.) of the liquid developer 8 on the supply roller 42 in the above configuration. The solid line L1 indicates the liquid temperature on the roller (° C.), and the broken line L2 indicates the developer amount change rate (%) on the developing roller. Detailed conditions are described below.

  In the developing roller 41, a polyurethane rubber having a hardness of 30 degrees (JISA) was provided on a core metal having a diameter of 20 mm and a thickness of 10 mm, and a polyurethane resin of 10 μm was coated thereon. For the supply roller 42, a polyurethane rubber having a hardness of 50 degrees is provided on a core metal of φ28 mm with a thickness of 6 mm. The pumping roller 43 is an anilox roller having a diameter of 40 mm.

  The developing roller 41 and the supply roller 42 have a push-in amount of 0.1 mm, and the supply roller 42 and the pumping roller 43 have a push-in amount of 0.4 mm.

  The cleaning blade 46 is made of polyurethane rubber with a thickness of 2 mm, and the regulating member 45 is made of stainless steel with a thickness of 0.15 mm.

  The linear speed of each roller at that time is 400 mm / sec for the developing roller 41, 500 mm / sec for the supply roller 42, and 500 mm / sec for the drawing roller 43.

  As apparent from FIG. 2, under the above conditions, the temperature of the liquid developer 8 on the supply roller 42 increases with the driving of the developing device (see the solid line L1). Further, as the temperature of the liquid developer 8 increases, the amount of developer on the developing roller 41 decreases (see broken line L2).

  The temperature rise of the liquid developer occurs as follows.

  The developing roller 41 and the supply roller 42 and the developing roller 41 and the blade 46 are rubbed by continuous driving of the developing device, and the temperature of each rubber roller rises due to the frictional heat.

  The thickness of the liquid developer 8 on each roller is about several μm, and the newly supplied developer also reaches the same temperature as the roller when it contacts the roller.

<Correction of developer supply amount according to temperature>
In this embodiment, the temperature of the liquid developer 8 on the supply roller 42 is detected by the temperature sensor 47 to correct the change due to the temperature of the developer amount on the developing roller 41, and the liquid development on the developing roller 41 is performed. The rotation speed of the supply roller 42 is controlled by the control means 49 so that the amount of the agent becomes constant (see FIG. 3).

  That is, the temperature sensor 47 functions as temperature detection means.

FIG. 3 shows the relationship between the temperature (° C.) of the liquid developer 8 on the supply roller 42 and the developer amount (g / m ² ) on the developing roller 41 in the above configuration. Solid lines S1 to S3 indicate the relationship when the supply roller rotation speed is 500 mm / sec, 550 mm / sec, and 600 mm / sec, respectively.

  When the temperature of the liquid developer increases, it is necessary to increase the rotation speed of the supply roller 42 in order to keep the developer amount on the developing roller 41 constant (target value).

  The temperature sensor 47 is preferably a non-contact type, for example, a thermopile type (in this embodiment, ESI-LP OMRON) was used.

<Warming up and driving conditions>
On the other hand, it can be seen from FIG. 2 that the temperature change of the liquid developer 8 on the supply roller 42 is large at the initial stage of driving, and the temperature change is small after a predetermined time.

  For this reason, when the temperature change of the liquid developer 8 is large, the control by the developer supply amount correction as described above cannot catch up with the change in the developer amount, and the error in the developer amount on the developing roller 41 is large. Or the control interval needs to be shortened.

  At the initial stage of driving of a developing device having a large temperature change, the countermeasure for correcting the developer supply amount according to the temperature as described above tends to be insufficient, which is not preferable. Therefore, for example, it is desirable to provide a mode (warming up mode) in which the printing operation (normal image forming mode) is not performed until a certain time has elapsed after the developing device is driven.

  FIG. 4 shows the relationship between the developing device drive time (min) and the temperature (° C.) of the liquid developer 8 on the supply roller 42 as in FIG. However, the driving time is a warm-up operation time, and the result (broken line L3) of changing the roller driving conditions is also shown in FIG.

  The solid line L1 indicates the relationship between the developing device driving time (warming up time) and the temperature of the liquid developer 8 on the supply roller 42 as in FIG.

  In L1, a warm-up time of 20 to 30 minutes is required until the liquid temperature on the roller is almost stabilized. This is too long and impractical.

  In this embodiment, in order to shorten the warm-up time, the driving conditions are set such that the amount of heat generated by each roller is larger during the operation in the warm-up mode than in the normal image forming mode.

  As a method of increasing the heat generation amount, the control means 49 controls the rotation speed of the supply roller 42 to be slower when operating in the warm-up mode than when operating in the normal image forming mode.

  The broken line L3 indicates the driving time (warming up time) and the liquid on the supply roller 42 when the supply roller 42 is rotated at a speed (400 mm / sec) slower than the speed (500 mm / sec) in the image forming mode. The relationship with the temperature of the developer 8 is shown.

  If the rotation speed of the supply roller 42 is slow, the liquid developer 8 that enters the nip portion between the supply roller 42 and the developing roller 41 is reduced, and the lubricating effect is reduced. As a result, the friction between the developing roller 41 and the supply roller 42 increases, and the amount of heat generated between the rollers also increases. That is, the temperature rise of the liquid developer 8 on the supply roller 42 also increases.

  Therefore, at the time of warming up, the temperature of the liquid developer 8 on the developing roller 41 and the supply roller 42 is increased by making the rotation speed of the supply roller 42 slower than that at the time of the printing operation (image formation). The rotation speed of the supply roller 42 is set to a normal value and the printing operation is started.

  In the broken line L3, the liquid temperature on the roller reaches the stable temperature in a warm-up time of about 10 minutes, and it is possible to return to the rotation speed of the supply roller 42 and shift to the normal image forming mode.

  As described above, in the warm-up mode, the warm-up mode is completed in a shorter time by reducing the rotation speed of the supply roller 42 and increasing the heat generation amount, and the liquid developer amount on the developing roller 41 is small. Can enter the image forming mode (printing operation) in a stable state.

(Second Embodiment: Configuration and Operation of Developing Device)
As a second embodiment of the developing device according to the present invention, FIG. 5 shows a partial sectional view of the developing device 4. The configuration and operation of the developing device 4 according to the second embodiment will be described. However, only differences from the first embodiment will be described.

  In the developing device according to the first embodiment, the form in which the warm-up time is shortened by changing the rotation speed of the supply roller 42 with respect to the developing roller 41 has been described. However, in the developing device according to the second embodiment, the developing roller 41 A mode in which the warm-up time is shortened by changing the pushing amount of the supply roller 42 with respect to is shown.

  Increasing the amount by which the supply roller 42 is pushed into the developing roller 41 increases friction during roller rotation and increases the amount of heat generated. Therefore, the liquid developer on the supply roller 42 and the developing roller 41 is the same as in the first embodiment. The temperature rise of 8 becomes faster.

  In order to change the pushing amount of the supply roller 42, an eccentric cam 51 is provided for the supply roller 42 as shown in FIG.

  The supply roller 42 is slidably held on a side plate (not shown), and the eccentric cam 51 is in contact with the shaft of the supply roller 42. When the eccentric cam 51 is rotated by the control means 49 in this state, the supply roller 42 moves with respect to the developing roller 41, and the pushing amount changes.

  The pumping roller 43 is held by the supply roller 42 by a holding member 52. By doing so, even when the supply roller 42 moves, the pushing amount of the pumping roller 43 and the supply roller 42 is kept constant.

  Further, a movement preventing device such as a spring 53 may be provided on the surface of the shaft of the supply roller 42 facing the eccentric cam 51. By doing so, the shaft of the supply roller 42 is always in contact with the eccentric cam 51, and the accuracy of the pushing amount is improved.

  Further, the rotational speed may be controlled as in the first embodiment in a state where the pushing amount of the supply roller 42 is changed.

  As described above, in the warm-up mode, the warm-up mode is completed in a shorter time by increasing the amount of pushing of the supply roller 42 into the developing roller 41 and the amount of heat generated, and the temperature change is small and the temperature on the developing roller 41 is increased. It becomes possible to enter an image forming mode (printing operation) in a state where the amount of the liquid developer is stable.

(Third Embodiment: Configuration and Operation of Developing Device)
As a third embodiment of the developing device according to the present invention, FIG. 6 shows a schematic sectional view. The configuration and operation of the developing device 4 according to the third embodiment will be described with reference to FIG. However, only differences from the first and second embodiments will be described.

  The developing device according to the third embodiment uses a pumping roller 43 as a roller for supplying the liquid developer 8 to the developing roller 41. That is, the pumping roller 43 functions as a supply roller.

  The pump-up roller 43 is an anilox roller partially immersed in the liquid developer 8 in the developer tank 44, and pumps up the liquid developer 8 by rotation.

  A regulating member 45 is in contact with the drawing roller 43 and regulates the amount of the liquid developer 8 on the drawing roller 43.

  Thereafter, the liquid developer 8 on the drawing roller 43 is conveyed to the nip portion with the developing roller 41.

  The developing roller 41 and the scooping roller 43 rotate in the same direction at the contact portion, and the liquid developer 8 on the scooping roller 43 is transferred onto the developing roller 41 by passing through the nip.

  In this configuration, when the rotation speed of the drawing roller 43 is changed, the developer supply amount per unit time to the developing roller 41 is changed, and the amount of the liquid developer 8 on the developing roller 41 can be controlled. . Specifically, when the rotational speed of the drawing roller 43 is increased, the amount of the liquid developer 8 on the developing roller 41 is increased.

  The developing roller 41, the drawing roller 43, the regulating member 45, the cleaning blade 46, and the like can be the same as those in the first embodiment.

  Also in this configuration, when the developing roller 41 and the pumping roller 43 are continuously driven, the developing roller 41 and the pumping roller 43 are caused by deformation of the developing roller 41 at the nip portion between the pumping roller 43 and friction between the developing roller 41 and the cleaning blade 46. Temperature rises.

  As a result, the temperature of the liquid developer on the roller rises and the amount of developer on the developing roller 41 decreases.

  In the developing device according to the present embodiment, the liquid on the developing roller 41 is kept constant in order to keep the developer amount on the developing roller 41 constant even when the temperature of the liquid developer changes during the printing operation (image forming mode). Control means 49 for measuring the developer temperature with the temperature sensor 47 and adjusting the rotational speed of the pumping roller 43 based on the result is provided.

  Further, as in the case of the first embodiment, a warm-up mode is provided, and in the warm-up mode, a driving condition is set such that the heat generation amount of the developing roller 41 is increased and the temperature rise of the liquid developer is accelerated.

  Specifically, during the warm-up mode, the push-in amounts of the developing roller 41 and the scooping roller 43 are increased as in the second embodiment. The adjustment mechanism for the push-in amount can use the same configuration as in the second embodiment.

  The control means 49 continues to measure the liquid developer temperature with the temperature sensor 47 even in the warm-up mode. When the temperature reaches a stable temperature, the control means 49 ends the warm-up mode and shifts to the normal image forming mode.

  In this way, the warm-up operation time can be shortened, the printing operation can be started quickly, and temperature measurement is continued even during printing, and the developer supply amount is adjusted to cope with temperature fluctuations during image formation. In addition, the developer amount can be stabilized.

(Fourth Embodiment: Configuration and Operation of Developing Device)
As a fourth embodiment of the developing device according to the present invention, FIG. The configuration and operation of the developing device 4 according to the fourth embodiment will be described with reference to FIG. However, only differences from the first, second, and third embodiments will be described.

  In the developing device 4 according to the fourth embodiment, the developing roller 41 is partly immersed in the liquid developer 8.

  A part of the developing roller 41 is immersed in the liquid developer 8 in the developer tank 44, and the liquid developer 8 is pumped up by rotation. The developing roller 41 uses the same rubber roller as in the first embodiment, and a regulating member 45 that regulates the amount of developer on the developing roller 41 is in contact with the upstream side in the rotation direction of the developing roller 41.

  As a result, the liquid developer 8 drawn up by the rotation of the developing roller 41 is regulated to a constant thickness and is carried to the developing area with the photoreceptor 1. That is, the restricting member 45 functions as a restricting means.

  Also at this time, due to the continuous driving of the developing roller 41, the temperature of the developing roller 41 increases due to friction between the developing roller 41 and the regulating member 45. As a result, the temperature of the liquid developer 8 on the regulated developing roller 41 increases, and the amount of developer decreases.

  The control means 49 measures the temperature of the liquid developer on the developing roller 41 with the temperature sensor 47 in order to keep the amount of developer on the developing roller 41 constant even when the temperature of the liquid developer 8 changes. The pressure contact force of the regulating member 45 is adjusted based on the above.

  The pressure contact force can be adjusted by changing the pressing amount of the regulating member 45 with respect to the developing roller 41.

  Furthermore, as in the case of the first embodiment, the warm-up mode is provided until the liquid developer temperature on the developing roller 41 reaches a certain value.

  Furthermore, the control means 49 increases the pressure contact force of the regulating member 45 against the developing roller 41 during warm-up to promote the temperature rise of the liquid developer 8 on the developing roller 41.

  As a result, in the warm-up mode, the press-contact force of the restricting means 45 against the developing roller 41 is increased and the amount of heat generation is increased, so that the warm-up operation time can be shortened and temperature measurement is continued even during printing. By adjusting the force, it is possible to cope with temperature fluctuations during image formation and to stabilize the developer amount.

  As described above, according to the developing device according to each embodiment of the present invention and the image forming apparatus provided with the developing device, in the developing device using the liquid developer, the warming-up mode is compared with the image forming mode. The driving conditions are controlled so that the amount of heat generated by the driving becomes larger. Thus, the temperature of the liquid developer on the developing roller can be stabilized and the amount of developer can be stabilized by a warm-up operation in a shorter time without complicating the apparatus configuration.

  In addition, the above-mentioned embodiment is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Photosensitive drum (image carrier)
2 Charging device 3 Exposure device 4 Developing device 5 Transfer roller 6 Cleaning device 7 Static eliminating device 8 Liquid developer 9 Recording medium 41 Developing roller (developer carrier)
42 supply roller 43 pumping roller 44 developer tank 45 regulating member 46 cleaning blade 47 temperature sensor 48 power supply 49 control means

Claims (6)

A developing roller for carrying and transporting on the surface a thin layer of a liquid developer in which toner is dispersed in a solvent, and developing a latent image formed on the image carrier;
A developing device having a supply roller that rotates in contact with the developing roller and supplies the liquid developer to the developing roller;
An image forming mode for performing development for normal image formation;
In a warm-up mode in which a preliminary operation is performed when starting the development,
Control means for controlling the driving of the developing roller and the supply roller,
In the warm-up mode, the control means controls the driving of the developing roller and the supply roller so that the amount of heat generated by driving the developing roller and the supply roller is larger than that in the image forming mode. A developing device. The control means includes
2. The developing device according to claim 1, wherein in the warming-up mode, the rotation of the supply roller is controlled to be slower than in the image forming mode. The control means includes
3. The developing device according to claim 1, wherein in the warm-up mode, control is performed so that a pressure contact force between the developing roller and the supply roller is increased as compared with the image forming mode. Developer temperature detecting means for detecting the temperature of the liquid developer on the developing roller or the supply roller;
The control means includes
In the warm-up mode, based on the temperature of the liquid developer detected by the developer temperature detecting means, the warm-up mode is terminated, and the image forming mode is entered.
In the image forming mode, the development amount is adjusted so that the supply amount of the liquid developer from the supply roller to the development roller is adjusted based on the temperature of the liquid developer detected by the developer temperature detection unit. The developing device according to claim 1, wherein driving of the roller and the supply roller is controlled. A developing roller for carrying and transporting on the surface a thin layer of a liquid developer in which toner is dispersed in a solvent, and developing a latent image formed on the image carrier;
A regulating device that contacts the developing roller and regulates the amount of the liquid developer on the developing roller,
An image forming mode for performing development for normal image formation;
In a warm-up mode in which a preliminary operation is performed when starting the development,
Control means for controlling the pressing force of the restricting means to the developing roller,
In the warm-up mode, the control unit controls the pressure contact force of the regulating unit against the developing roller so that the amount of heat generated by the regulating unit with respect to the developing roller is larger than that in the image forming mode. A developing device. An image carrier;
A developing device that develops the electrostatic latent image formed on the image carrier using a liquid developer,
The image forming apparatus according to claim 1, wherein the developing device is the developing device according to claim 1.

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