JP2006011292A - Method for adjusting gap between rollers in liquid developing device and liquid developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for adjusting a gap between rollers in a liquid developing device, wherein the film thickness of the thin layer of liquid developer is properly controlled without being adversely influenced by a fluctuation in temperature and good image quality is always maintained, and to provide the liquid developing device. <P>SOLUTION: In the liquid developing device 54, the temperature of the liquid developer 70 is detected and the gap between a plurality of rollers, that is, a coating roller 73 and a drawing-up roller 74 provided in the liquid developing device 54 is adjusted in accordance with the result of detection. As a result, a proper amount of liquid developer 70 is transferred to a developing roller 72 through the coating roller 73 even when the viscosity of the liquid developer 70 transferred from the drawing-up roller 74 to the coating roller 73 is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for adjusting a gap between rollers in a liquid developing device used in a copying machine, a facsimile machine, a printer, and the like, and a liquid developing device.

  The liquid developing device will be described with reference to FIG. FIG. 10 is a schematic perspective view illustrating a general liquid developing apparatus. The liquid developing device 100 develops an electrostatic latent image formed on a latent image carrier 140 such as a photoreceptor (for example, a photosensitive drum) with a liquid developer in which toner is dispersed in an insulating liquid. ing.

  The liquid developing device 100 includes a developing roller 110, a coating roller (anilox roller) 120 that applies a thin layer of liquid developer to the developing roller 110, and a coating amount that regulates the amount of liquid developer on the coating roller 120. A doctor blade 130 as a control member and a developer storage tank (not shown) for storing the liquid developer are provided. Further, a cleaning blade 150 for cleaning the toner on the latent image carrier 140 is provided. In the liquid developing device 100, the liquid developer in the developer storage tank (not shown) is pumped up by the application roller 120 or a pumping roller (not shown), and the liquid developer on the application roller 120 is discharged by the doctor blade 130. After the amount is regulated, it is applied to the developing roller 110 in a thin layer. The developing roller 110 conveys the thinned liquid developer to the developing area facing the latent image carrier 140.

  In the development area, development based on the latent image is performed, and the liquid developer on the development roller 110 is supplied to the latent image carrier 140. On the other hand, excess liquid developer on the application roller 120 regulated by the doctor blade 130 is collected into the developer storage tank. The recovered liquid developer is mixed with the liquid developer stored in the developer storage tank, and is supplied to the application roller 120 again in a state where the toner is uniformly dispersed in the liquid developer.

  By the way, during the development, the liquid developer moves the charged toner in the insulating liquid by the electrostatic force, and develops the electrostatic latent image on the latent image carrier 140. At this time, the shorter the moving distance of the toner, the less the charge charged on the toner is lost, and the development efficiency is improved. Therefore, in order to increase the development efficiency, a thin layer of a micron unit is formed on the developing roller 110 as described above, and the thinned liquid developer is brought into contact with the latent image carrier 140 as described above. Yes.

  As a means for forming such a thin layer of liquid developer, an uneven pattern is formed on the peripheral surface of the coating roller 120, and the amount of liquid developer is determined by contacting a doctor blade to the peripheral surface. The measured liquid developer is transferred and applied by the developing roller 110 to form a uniform thin layer.

  However, conventionally, due to temperature fluctuations in the apparatus, it is difficult to form an appropriate film thickness of the thin layer, and there is a problem of deterioration in image quality. For example, when the temperature in the apparatus increases, the temperature of the liquid developer also increases, and as a result, the viscosity of the liquid developer decreases, so that the liquid development conveyed to the developing roller even if measured by the doctor blade 130. The film thickness of the agent is reduced, and the image density is lowered due to transfer failure.

  On the other hand, when the temperature inside the apparatus is lowered, the temperature of the liquid developer is also lowered. As a result, the viscosity of the liquid developer is increased, so that the liquid developer is conveyed to the developing roller even if measured by the doctor blade 130. The thickness of the thin layer of the liquid developer is increased, causing an image flow and a decrease in image density.

  Further, when the amount of liquid developer from the drawing roller to the application roller changes depending on the temperature in the apparatus, the amount after measurement changes due to the influence of the developer amount before measurement even if the amount is measured by the doctor blade. For example, when the temperature in the apparatus becomes high and the viscosity is low, the film thickness formed on the pumping roller becomes thin, so the amount to the application roller is reduced and the measured amount is also reduced.

In order to solve this problem, a method of keeping the temperature of the liquid developer constant by controlling a temperature heater or the like has been considered, but it is not desirable from the viewpoint of energy saving due to recent environmental problems.
SUMMARY OF THE INVENTION An object of the present invention is to provide a gap adjusting method between a roller and a liquid in a liquid developing apparatus capable of appropriately controlling the film thickness of a thin layer of a liquid developer without being adversely affected by temperature fluctuations and always maintaining good image quality. It is to provide a developing device.

  In order to solve the above problem, the invention according to claim 1 detects the viscosity of the liquid developer or the degree of the viscosity influencing factor, and a plurality of rollers provided in the liquid developing device according to the detection result. The gist of the present invention is to adjust a gap between rollers in a liquid developing device characterized by adjusting a gap between the rollers.

  The gist of the second aspect of the invention is a liquid developing apparatus including a plurality of rollers for transferring the liquid developer, the liquid developing apparatus including an adjusting means for adjusting a gap between the rollers. It is.

  According to a third aspect of the present invention, in the liquid developing device including a plurality of rollers for transferring the liquid developer, the adjusting means for adjusting the gap between the rollers and the degree of the viscosity of the liquid developer or the viscosity influencing factor are detected. The gist of the present invention is a liquid developing apparatus comprising a detection unit and a control unit that adjusts and controls the adjustment unit according to a detection result of the detection unit.

According to the first aspect of the present invention, the film thickness of the thin layer of the liquid developer can be appropriately controlled without being adversely affected by temperature fluctuations, and there is an effect that good image quality can always be maintained.
According to the invention of claim 2, it can be applied as an apparatus for directly realizing the invention of claim 1, and the invention of claim 1 can be easily performed.

  According to the third aspect of the present invention, the film thickness of the thin layer of the liquid developer can be appropriately controlled without being adversely affected by temperature fluctuations, and the effect of always maintaining good image quality is achieved.

(First embodiment)
Hereinafter, an embodiment in which the present invention is embodied in a liquid developing device of a tandem type color image forming apparatus (hereinafter simply referred to as an image forming apparatus) will be described with reference to FIGS.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus. The image forming apparatus includes a paper feeding unit 1, a vertical conveyance path 2, a registration roller pair 3, a belt conveyance unit 4, a first image forming unit 5, a second image forming unit 6, a third image forming unit 7, 4 image forming means 8, secondary transfer means 9, fixing means 10, discharge conveyance path 11, discharge tray 14 and the like. The paper feed means 1 includes a paper feed cassette 1a and a pickup roller 1b, and transports the paper P in the paper feed cassette 1a to the vertical transport path 2 by the pickup roller 1b. The vertical conveyance path 2 conveys the conveyed paper P to the secondary transfer unit 9 via the registration roller pair 3.

  The belt conveying unit 4 includes a driving roller 41, a driven roller 42, and an endless intermediate transfer belt 43 that is stretched over the two rollers. The intermediate transfer belt 43 maintains an appropriate tension by the tension roller 44. In this state, the driving roller 41 receives driving force from a driving motor (not shown), and the outer peripheral speed of the photosensitive drum 51 in each image forming unit and the outer peripheral speed of the intermediate transfer belt 43 of the belt conveying unit 4 are constant. It is driven to become.

  The first to fourth image forming units 5 to 8 shown in FIG. 1 are for black (BK), magenta (M), cyan (C), and yellow (Y) from the left side in the figure, and are all substantially the same. It is a unit of composition. Here, for convenience of explanation, the configuration of the first image forming unit 5 will be described with reference to FIG. In other image forming units, the same components as those of the first image forming unit 5 are denoted by the same reference numerals. The first image forming means 5 includes a photosensitive drum 51, a main charging device 52, an LPH (LED PRINT HEAD) 53, a liquid developing device 54, a primary transfer means 55, a cleaning device 56, and a charge eliminating lamp 57, and is made of resin. By assembling it into the housing made of the above, it becomes one unit and is attached to the apparatus main body (not shown).

  The photosensitive drum 51 is an amorphous silicon drum and is charged by the main charging device 52 so that the dark potential at the developing position is about 300V. The LPH 53 irradiates the surface of the charged photoconductive drum 51 with light corresponding to image information, whereby an electrostatic latent image is formed on the surface of the photoconductive drum 51. The photosensitive drum 51 corresponds to a latent image carrier. The LPH 53 is used to reduce the size of the unit, but an LSU (laser scanning unit) may be used.

  The liquid developing device 54 stirs and mixes a developer composed of toner and a carrier so as to have a predetermined concentration, and an electrostatic latent image of a portion of the photosensitive drum 51 irradiated with the developer by a developing roller. To form a toner image on the photosensitive drum 51. The dark potential of the photosensitive drum 51 is set to 300V, the developing bias is set to 200V, and the post-exposure potential is set to 20V. That is, the dark potential corresponds to the white portion of the image, the post-exposure potential corresponds to the black portion of the image, and this difference is a so-called contrast potential. The toner image obtained by developing the electrostatic latent image formed as described above is transferred to the intermediate transfer belt 43 of the belt conveying unit 4 in the nip with the primary transfer unit 55. In the present embodiment, the primary transfer means 55 uses a transfer roller, and a voltage having a polarity opposite to the surface potential of the photosensitive drum 51 is set in a range of −1000 to −1300 V and applied.

  The toner that has not been transferred on the photosensitive drum 51 is scraped off by the rubber blade 56a of the cleaning device 56 in the next process. The photosensitive drum 51 is neutralized by a neutralizing lamp 57 to lower the residual potential on the surface and make it uniform, and thereafter, it is prepared for the next series of processes. The potential setting for image formation in this manner varies depending on the characteristics of the photosensitive drum 51, the toner performance, and the environment. The image forming apparatus develops images corresponding to magenta, cyan, and yellow on the photosensitive drum by the second to fourth image forming units 6 to 8 in the same manner as the first image forming unit 5. A full-color image is formed by sequentially repeating the transfer onto the intermediate transfer belt 43 without transfer.

  Returning to FIG. 1, image formation after transfer will be described. In the present embodiment, the secondary transfer unit 9 includes a secondary transfer roller. The secondary transfer unit 9 is disposed at a secondary transfer position on the vertical conveyance path 2. The secondary transfer position is a position where the secondary transfer unit 9 faces the driving roller 41 and is pressed against the intermediate transfer belt 43. A secondary transfer bias is applied to the secondary transfer unit 9, and the paper P conveyed by the secondary transfer unit 9 from the intermediate transfer belt 43 through the vertical conveyance path 2 and the registration roller pair 3. A full-color image is secondarily transferred to the image. Thereafter, the paper P onto which the full-color image has been secondarily transferred is separated from the intermediate transfer belt 43 and conveyed to the fixing unit 10. The fixing unit 10 includes a first fixing roller 10a and a second fixing roller 10b. Each fixing roller includes a fixing heater (not shown), and the identification fixing heater is controlled to a predetermined temperature necessary for fixing. Due to this temperature, a full-color image is fixed on the paper P that is pressed and passed by both rollers. The paper P is discharged to the discharge tray 14 via the discharge conveyance path 11 after being fixed by the fixing unit 10.

  The intermediate transfer cleaning unit 12 includes an intermediate transfer cleaning roller 12a and an intermediate transfer cleaning blade 12b. The intermediate transfer cleaning roller 12 a is in pressure contact with the intermediate transfer belt 43 and is rotated in the same direction as the rotation direction of the intermediate transfer belt 43. The intermediate transfer cleaning blade 12b counter-contacts the intermediate transfer belt 43 on the downstream side from the position of the intermediate transfer cleaning roller 12a in the moving direction of the intermediate transfer belt 43, thereby removing residual toner on the intermediate transfer belt 43. The intermediate transfer belt 43 is prepared for the next image forming process.

(Liquid developing device 54)
Next, a specific configuration of the liquid developing device 54 will be described with reference to FIGS.
The liquid developing device 54 of this embodiment includes a storage tank 71 that stores the liquid developer 70. Inside the storage tank 71, a developing roller 72 as a developer carrier, a coating roller 73, a pumping roller 74, a doctor blade 75, a cleaning blade 76, and a pair of stirring screws 77a and 77b are provided. ing.

  The developing roller 72, the application roller 73, the pumping roller 74, and the stirring screws 77a and 77b are rotationally driven by a drive motor (not shown) through a drive transmission mechanism K including a gear train and the like. The drive transmission mechanism K will be described later.

  The liquid developer 70 is adjusted so as to disperse the toner at a high concentration in the carrier liquid composed of a nonpolar insulating liquid such as silicon oil and the carrier liquid. The agitating screws 77a and 77b circulate and agitate the liquid developer 70. A part of the pumping roller 74 is immersed in the liquid developer 70, and the pumped liquid developer 70 is applied to the application roller 73.

  A peripheral surface excluding both ends of the application roller 73 is an application region for the developing roller 72. In the application region, an uneven pattern is formed. Then, the liquid developer 70 pumped up by the pump-up roller 74 is weighed after the excess liquid developer 70 is removed (restricted) by the doctor blade 75 that is in counter-contact with the rotation direction of the application roller 73. The

  The application roller 73 forms a thin layer of the liquid developer 70 on the development roller 72 by applying the liquid developer 70 on the development roller 72. In the developing area on the photosensitive drum 51, the latent image is developed by the liquid developer 70. Further, after development, the liquid developer 70 remaining on the developing roller 72 is removed from the developing roller 72 by the cleaning blade 76.

(Drive transmission mechanism)
The drive transmission mechanism K will be described. As shown in FIGS. 4 and 5, end walls 80 are provided at both ends in the longitudinal direction of the storage tank 71 (only one end wall 80 is shown in FIGS. 4 and 5). The rotation shafts of the developing roller 72, the application roller 73, and the scooping roller 74 are rotatably supported on the both end walls 80. The rotation shafts 72a, 73a, and 74a of the developing roller 72, the application roller 73, and the scooping roller 74 protrude from one end wall 80, and spur gears 81, 82, and 83 are fixed to the respective shafts. Further, as shown in FIG. 6, cylindrical bearing portions 80a and 80b of idle gears are formed on the outer surface of the end wall 80, and the respective bearing portions 80a and 80b mesh with the spur gears 82 and 83, respectively. Idle gears 84 and 85 are pivotally supported. The idle gears 84 and 85 are meshed with each other.

  These spur gears 81, 82, 83 and idle gears 84, 85 constitute a drive transmission mechanism K. The spur gear 81 and the idle gear 84 are meshed with a spur gear 86 of a transmission drive system that operates in conjunction with a drive motor (not shown), and the rotational torque of the drive motor is transmitted.

(Adjustment mechanism T)
Next, an adjusting mechanism T as an adjusting means for adjusting the gap between the rollers will be described with reference to FIGS. One set of the adjusting mechanism T is provided on each end of the rotary shaft 74a of the pumping roller 74. However, since the configuration is the same, one adjusting mechanism T will be described, and the other adjusting mechanism T will be described. The description is omitted.

  As shown in FIG. 6, a bearing support housing hole 87 is formed through the end wall 80 that supports the rotating shaft 74 a of the pumping roller 74. The bearing support housing hole 87 has a small diameter portion 87a on the pumping roller 74 side, and a large diameter portion 87b on the spur gear 83 side. The small diameter portion 87a and the large diameter portion 87b are coaxial. A bearing support 88 is housed in the bearing support housing hole 87. The bearing support 88 is formed in a substantially cylindrical shape. The bearing support 88 includes a first insertion portion 88a having a small outer diameter and a second insertion portion 88b having a large outer diameter. Each insertion portion includes a small diameter portion 87a of the bearing support housing hole 87 and The large diameter portions 87b are respectively fitted. A pair of mounting pieces 88c are formed on the peripheral portion of the second insertion portion 88b of the bearing support 88 so as to protrude in directions opposite to each other by 180 degrees. The bearing support 88 is fastened and fixed to the end wall 80 by a bolt 89 screwed to the end wall 80 via an attachment piece 88c (see FIG. 5).

  The bearing support hole 88d of the bearing support 88 is formed in a long hole shape. The long hole-shaped bearing support hole 88d includes a circular arc surface A that is proximal to the axis O of the bearing portion 80b of the idle gear 85 that meshes with the spur gear 83, and a circular arc surface B that is distal (FIG. 7 ( a)).

  The circular arc surfaces A and B are respectively formed along concentric circles having a radius with the axis O as the center. The sealing material 90 is fitted in the bearing support hole 88d. A first bearing 91 is inserted into the bearing support hole 88d through a seal material 90. The sealing material 90 is made of a foam material having a low hardness, that is, an elastically deformable material (for example, a foamed sponge), and can follow the movement of the first bearing 91 within a movable range. As shown in FIG. 6, the sealing material 90 has a bearing insertion hole 90a formed therethrough, and a first bearing 91 is disposed in the bearing insertion hole 90a.

  As shown in FIG. 6, the first bearing 91 includes a cylindrical insertion portion 91 a and an outward flange 91 b formed at one end of the insertion portion 91 a, and the insertion portion 91 a is a bearing insertion hole of the sealing material 90. It is inserted in 90a. A rotation shaft 74a is rotatably supported in the bearing hole 91c of the first bearing 91.

  Further, on the rotary shaft 74a, a second bearing 92 is fitted on the tip side of the spur gear 83 so as to be relatively rotatable in a bearing hole 92c. The second bearing 92 is movably engaged in a guide groove 100 (see FIG. 7B) provided in the apparatus frame 110.

The guide groove 100 includes an arc guide surface C proximal to the axis O of the bearing portion 80 b of the idle gear 85 that meshes with the spur gear 83, and a distal arc guide surface D.
Side surfaces 92 a and 92 b formed along the arc guide surface C and the arc guide surface D of the guide groove 100 are provided on the peripheral portion of the second bearing 92. When the second bearing 92 moves along the guide groove 100, the second bearing 92 is guided by the arc guide surface C and the arc guide surface D. As a result, the rotary shaft 74a rotated relative to the second bearing 92 is A locus on a circle having a radius R is moved from the axis O.

  As shown in FIGS. 4 and 5, a step motor 99 is attached and fixed to the lower end of the storage tank 71. A screw portion 31 protrudes from the upper surface of the housing 99a of the step motor 99 so as to advance and retract in accordance with forward and reverse rotation of an output shaft (not shown) of the step motor 99. A contact 32 is fixed to the tip (upper end) of the screw portion 31. The contact 32 is always in contact with the lower surface of the second bearing 92. A guide member 30 is fixed to the lower end portion of the storage tank 71, and a contact 32 is slidably inserted into a guide hole 30 a pierced through the guide member 30. Guide up and down movement.

The adjustment mechanism T is configured by the bearing support 88, the step motor 99, the screw portion 31, the first bearing 91, the second bearing 92, the guide groove 100, and the like.
Next, the control device 93 of the adjusting mechanism T will be described with reference to FIG.

  The control device 93 as a control means adjusts and controls the two sets of adjusting mechanisms T. The control device 93 includes a CPU (central processing unit) 94, a ROM 95, and a RAM 96. The ROM 95 stores a drive control program for the adjustment mechanism. A temperature sensor 97 for detecting the temperature of the liquid developer 70 is provided in the storage tank 71. The temperature sensor 97 inputs a liquid developer temperature detection signal to the CPU 94. In the present embodiment, the temperature corresponds to a viscous influence factor, and the temperature value indicates the degree of the viscous influence factor. The temperature sensor 97 as temperature detecting means corresponds to detecting means for detecting the degree of the viscosity affecting factor. Further, the CPU 94 outputs a drive control signal corresponding to the temperature detection signal to the motor drive circuit 98 based on the drive control program. The motor drive circuit 98 rotates the step motor 99 forward and backward based on the drive control signal.

(Operation of the embodiment)
Now, the operation of the liquid developing device 54 configured as described above will be described.
The control of the control device 93 is performed on two sets of adjustment mechanisms T. However, for convenience of explanation, one set of adjustment mechanisms T will be described, and the control on the other adjustment mechanism T is the same. Omitted.

  When the temperature sensor 97 inputs a temperature detection signal of the liquid developer 70 to the control device 93, the CPU 94 of the control device 93 sets the gap between the application roller 73 and the pumping roller 74 according to the detected temperature of the liquid developer 70. Determine by referring to the map. The map is stored in the ROM 95. The map is a two-dimensional map showing the relationship between the temperature of the liquid developer 70 and the gap between the application roller 73 and the pumping roller 74, and the degree of the gap is set according to the temperature of the liquid developer 70. ing.

  In other words, since the viscosity of the liquid developer 70 uniquely changes according to the temperature of the liquid developer 70, the degree of the gap is set in the map according to the degree of viscosity of the liquid developer 70. Has the same meaning as

  When the temperature of the liquid developer 70 is high, the viscosity of the liquid developer 70 becomes low. Therefore, in the map, the gap between the pumping roller 74 and the application roller 73 is made narrower than when the temperature is low, so that the pumping roller It is set so that the liquid developer 70 can be satisfactorily transferred from 74 to the coating roller 73, that is, an appropriate amount can be transferred. In addition, when the temperature of the liquid developer 70 is low, the viscosity of the liquid developer 70 is increased. Therefore, in the map, the gap between the pumping roller 74 and the application roller 73 is made wider than when the temperature is high. The liquid developer 70 is set to be favorably transferred from the drawing roller 74 to the application roller 73, that is, an appropriate amount can be transferred.

  For example, as an example of a map, when the liquid developer 70 is 15 ° C. or lower, it is 0.11 mm, for maintaining 15 ° C., when it is lower than 20 ° C., 0.09 mm, 0.07 mm, 0.05 mm when 25 ° C. or higher and lower than 30 ° C., 0.03 mm when 30 ° C. or higher.

  Note that the temperature of the liquid developer 70 and the gap value that makes the thickness of the thin layer suitable for image formation by the appropriate amount of transfer of the liquid developer 70 to the application roller 73 at that temperature are: These are values obtained in advance through tests or the like.

  When the CPU 94 obtains a gap value (hereinafter referred to as a gap value) corresponding to the current temperature of the liquid developer 70 with reference to the map, the CPU 94 sets the gap value as a target value. On the other hand, the CPU 94 determines the degree of the current gap between the rollers (hereinafter referred to as the current value) as the total rotational drive of the step motor 99 that has driven the step motor 99 from when the liquid developing device 54 is turned on. Calculate based on quantity. The total rotational drive amount is a positive value in the forward rotation direction (in this embodiment, the rotation direction for moving the screw portion 31 upward), and the reverse rotation direction (in order to move the screw portion 31 downward). (The rotation direction) is a negative value and is the total amount. In order to obtain the current value, a position sensor that detects the position of the pumping roller 74 may be used.

  Then, the CPU 94 calculates a deviation between the target value and the current value, and outputs a drive control signal to the motor drive circuit 98 so as to eliminate the deviation. The motor drive circuit 98 drives the step motor 99 based on the drive control signal so that the gap between the rollers matches the target value.

  That is, when the step motor 99 rotates forward, the screw portion 31 is advanced upward to push the second bearing 92 upward. The second bearing 92 is guided by the guide groove 100 and moves along an arc having a radius R with the axis O as the center, as shown in FIG. Along with this, the rotating shaft 74a also moves in the same direction. At this time, the bearing 91 (see FIG. 7A) attached to the rotating shaft 74a is within a range allowed by the sealing material 90 and the bearing support hole 88d along an arc having a radius R centering on the axis O. It moves in the bearing support hole 88d. The pumping roller 74 is moved upward by the movement of the rotating shaft 74a, and the gap with the application roller 73 is narrowed.

  In this case, the viscosity of the liquid developer 70 is lower than when the temperature of the liquid developer 70 is high and the temperature of the liquid developer 70 is low. However, since the gap between the rollers is narrowed by the adjusting mechanism T, the transfer amount of the liquid developer 70 is appropriately secured from the draw-up roller 74 to the application roller 73, so that the transfer amount of the liquid developer 70 is large. Become. In this case, even if it is regulated by the doctor blade 75, the amount transferred from the coating roller 73 to the developing roller 72 can be secured. As a result, the thin film thickness of the liquid developer 70 formed on the developing roller 72 is suitable for image formation.

  Conventionally, even when the temperature of the liquid developer 70 increases, the gap between the rollers does not change. Therefore, the liquid developer 70 having a reduced viscosity is moved from the pumping roller 74 to the application roller 73 by an appropriate amount. Although this is not possible, this is not the case with this embodiment.

  When the step motor 99 rotates in the reverse direction, the screw portion 31 is retracted downward. The second bearing 92 moves downward by its own weight and the weight of the pumping roller 74 and the like. At this time, the second bearing 92 is guided by the guide groove 100 and moves along an arc having a radius R around the axis O as shown in FIG. 7B. Along with this, the rotating shaft 74a also moves in the same direction. At this time, the bearing 91 (see FIG. 7A) attached to the rotating shaft 74a is within the bearing support hole 88d within the range allowed by the sealing material 90 along the arc of radius R centering on the axis O. To move. The pumping roller 74 is moved downward by the movement of the rotating shaft 74a, and the gap with the application roller 73 is widened.

  In this case, the viscosity of the liquid developer 70 is higher than when the temperature of the liquid developer 70 is low and the temperature of the liquid developer 70 is high. However, since the gap between the rollers is widened by the adjusting mechanism T, the transfer amount of the liquid developer 70 is appropriately secured from the draw-up roller 74 to the application roller 73, so that the transfer amount of the liquid developer 70 is small. Become. In this case, even if it is regulated by the doctor blade 75, the amount transferred from the coating roller 73 to the developing roller 72 can be secured. As a result, the thin film thickness of the liquid developer 70 formed on the developing roller 72 is suitable for image formation.

  Conventionally, since the gap between the rollers does not change even when the temperature of the liquid developer 70 is lowered, the liquid developer 70 having increased viscosity moves from the pumping roller 74 to the application roller 73 by an appropriate amount. However, this is not the case with this embodiment.

  Note that the vertical movement of the second bearing 92 moves on an arc along a radius R with the axis O of the idle gear 85 as the center. At this time, the spur gear 83 attached to the rotary shaft 74a also moves on an arc along the radius R about the axis O of the idle gear 85, so that the spur gear 83 and the axis of the idle gear 85 are aligned. There is no change between them, and the meshing between the spur gear 83 and the idle gear 85 is not hindered.

  As described above, in the liquid developing device 54 of the present embodiment, the temperature of the liquid developer 70 (degree of viscosity influence factor) is detected, and a plurality of units provided in the liquid developing device 54 are detected according to the detection result. The gap between the application roller 73 and the pumping roller 74 is adjusted. Since the gap between the application roller 73 and the pumping roller 74 is automatically adjusted according to the temperature of the liquid developer 70, the viscosity of the liquid developer 70 transferred from the pumping roller 74 to the application roller 73 changes. However, an appropriate amount of the liquid developer 70 can be transferred to the developing roller 72 via the application roller 73. As a result, the film thickness of the thin layer of the liquid developer 70 can be appropriately controlled without being adversely affected by temperature fluctuations, and good image quality can always be maintained.

  Further, in the present embodiment, in the adjustment mechanism T, the second bearing 92 is moved in the vertical direction so as to move on an arc along a radius R with the axis O of the idle gear 85 as the center. The spur gear 83 attached to is also moved on an arc along the radius R with the axis O of the idle gear 85 as the center. As a result, there is no change between the shaft centers of the spur gear 83 and the idle gear 85, and the meshing between the spur gear 83 and the idle gear 85 is not hindered.

In addition, you may change embodiment of this invention as follows.
In the above-described embodiment, the screw portion 31 is moved up and down by rotating the step motor 99 of the adjustment mechanism T, but a cam 200 may be used as shown in FIG. The cam 200 of FIG. 9 is an eccentric disk cam, and the gap between the rollers is adjusted by moving the second bearing 92 up and down by rotating the rotating shaft 210 arranged eccentrically forward and backward by a step motor (not shown). Have been able to.

  In place of the temperature sensor 97 of the above-described embodiment, in order to detect the degree of viscosity of the liquid developer 70, the stirring screw 77a is driven as a detection unit that detects the driving torque of the stirring screw 77a that mixes the liquid developer 70. A torque sensor for detecting the torque of the motor (not shown) may be provided. By this torque detection, the degree of viscosity of the liquid developer 70 can be detected, and the gap between the rollers may be adjusted according to the torque detection. Here, the torque sensor corresponds to detection means for detecting the degree of viscosity of the liquid developer.

  ○ As a viscosity influencing factor that affects the viscosity of the liquid developer, there is a toner concentration. That is, when the toner concentration is high, the viscosity increases, and when the toner concentration is low, the viscosity decreases. For this reason, a density detecting sensor for detecting the toner density may be provided as a detecting means for detecting the degree of the viscosity affecting factor.

1 is a schematic cross-sectional view of an image forming apparatus including a liquid developing device according to an embodiment embodying the present invention. 1 is a cross-sectional view of a liquid developing apparatus according to an embodiment. Explanatory drawing of the principal part expanded similarly. The schematic perspective view which comprises a drive system. A schematic side view of the drive system The disassembled perspective view of an adjustment mechanism similarly. (A) is principal part sectional drawing of an adjustment mechanism similarly, (b) is explanatory drawing of the guide of the 2nd bearing 92. FIG. The block diagram of a control apparatus. FIG. 7B corresponds to another embodiment. 1 is a schematic perspective view illustrating a general liquid developing device.

Explanation of symbols

54 ... Liquid developing device 70 ... Liquid developer 72 ... Developing roller (developer carrier)
73 ... Application roller 74 ... Pumping roller 93 ... Control device (control means)
97 ... Temperature sensor (detection means)
T: Adjustment mechanism (adjustment means)

Claims (3)

  The viscosity of the liquid developer or the degree of the viscosity influencing factor is detected, and a gap between a plurality of rollers provided in the liquid developing device is adjusted according to the detection result. Gap adjustment method. In a liquid developing device including a plurality of rollers for transferring a liquid developer,
A liquid developing apparatus comprising an adjusting means for adjusting a gap between the rollers. In a liquid developing device including a plurality of rollers for transferring a liquid developer,
Adjusting means for adjusting the gap between the rollers;
Detection means for detecting the viscosity of the liquid developer or the degree of the viscosity influencing factor;
A liquid developing apparatus comprising: a control unit that adjusts and controls the adjustment unit according to a detection result of the detection unit.

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