JP2009053486A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, and the like, capable of maintaining good image quality, regardless of the temperature change, or the like. <P>SOLUTION: A thermometer 98 is disposed in the developing device 9, and the higher the temperature measured by the thermometer 98 becomes, the smaller the gap between a supply roller 92 and a support roller 93 is made; and the lower the measured temperature becomes the larger the gap is set. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multifunction machine and a developing device that can be used in the image forming apparatus, and more particularly to a developing device that forms an image using a liquid developer. And a wet image forming apparatus.

  In recent years, a wet developing apparatus and an image forming apparatus (hereinafter referred to as “developing apparatus”) that perform image formation using a liquid developer containing a liquid carrier and toner have been proposed. In a wet developing device or the like, the electrostatic latent image is developed by attaching toner from the developing roller to the electrostatic latent image drawn on the photosensitive drum.

In order to obtain a good image, it is important to form a thin layer of a uniform liquid developer on the surface of the developing roller in a wet developing device or the like. Therefore, a restriction roller such as an anilox roller that restricts the amount of developer on the developing roller is used, a doctor blade that contacts the anilox roller is further provided, and further, as disclosed in Patent Document 1, between the anilox roller and the developing roller A technique for forming a uniform toner layer between the anilox roller and the developing roller has been studied, such as providing an intermediate roller.
JP 2006-30395 A

  However, the present inventors have confirmed that the disturbance of the toner layer further upstream of the anilox roller also affects the uniformity of the toner layer on the developing roller.

  Therefore, the present invention provides a developing device and an image forming apparatus that can form a toner layer more stably and uniformly on a roller that supplies a developer to an image carrier such as a photosensitive drum. Objective.

  In order to solve the above problems, a developing device according to claim 1 supplies the developer containing toner and a liquid carrier to an image carrier capable of carrying an electrostatic latent image. A developing device for developing a latent image, the developing device being arranged to face the image carrier, a first roller for supplying developer to the electrostatic latent image, and a first roller to face the first roller, The second roller that attaches the developer to the first roller, the third roller that is arranged so as to face the second roller, and that attaches the developer to the second roller, and the viscosity of the developer increases, A gap adjusting unit that increases a gap between the second roller and the third roller.

  Since the developing device includes the gap adjusting unit, the gap between the second roller and the third roller can be increased as the developer viscosity increases. Disturbance of the uniformity of the agent layer can be prevented, and as a result, the developer layer on the first roller can be made uniform. Therefore, a good image can be obtained regardless of the change in the viscosity of the developer.

  According to a second aspect of the present invention, there is provided a developing device for developing the electrostatic latent image by supplying a developer containing toner and a liquid carrier to an image carrier capable of carrying the electrostatic latent image. A first roller that is disposed to face the image carrier and supplies developer to the electrostatic latent image; and a developer that is disposed to face the first roller and that is disposed on the first roller. A second roller that adheres to the second roller, a third roller that adheres the developer to the second roller, a temperature measuring unit that measures the temperature of the developer, and the temperature From the measurement result by the measurement unit, a gap adjustment unit is provided which increases the gap between the second roller and the third roller as the developer temperature decreases.

  One factor that affects the viscosity of the developer is temperature. Therefore, according to the configuration of the second aspect, similarly to the developing device of the first aspect, it is possible to maintain a good image regardless of a change in the viscosity of the developer caused by a change in temperature.

  According to a third aspect of the present invention, there is provided an image carrier capable of carrying an electrostatic latent image, and a first roller disposed so as to face the image carrier and supplying a developer to the electrostatic latent image. A second roller disposed to face the first roller and attaches the developer to the first roller; and a second roller disposed to face the second roller and attaches the developer to the second roller. An image forming apparatus including three rollers and a gap adjusting unit that increases the gap between the second roller and the third roller as the viscosity of the developer increases is also included in the technical scope of the present invention.

  According to the present invention, the image quality can be kept constant regardless of changes in conditions such as temperature, and problems such as device malfunctions are less likely to occur.

  A developing device 9 as an embodiment of the developing device of the present invention and a printer 1 as an embodiment of an image forming apparatus will be described below with reference to the drawings. For convenience of explanation, the position and size of the members are drawn with emphasis as appropriate in the drawings. In the following embodiments, a color printer will be described as an example of the image processing apparatus of the present invention, but the present invention is not limited to this. That is, the image processing apparatus of the present invention only needs to include an image forming unit, and may be a so-called multi-function peripheral (MFP) having a function as a copying machine or a facsimile machine or only a copying function. Specific configurations of these members described below, other members, and the like can be appropriately changed.

<1. Printer 1>
First, the overall configuration of the printer 1 will be described with reference to FIG. FIG. 1 is a front view illustrating a configuration of a main part of the printer 1.

  The printer 1 includes an image forming unit 2 that forms a color image, a paper storage unit 3 that stores paper P, a transfer unit 4 that transfers an image formed by the image forming apparatus 2 on the paper P, and an image on the paper P. A fixing unit 5 for fixing, a paper discharge tray 6 for receiving the paper P after the image is fixed, a paper transport unit 7 for transporting the paper P from the paper storage unit 3 to the paper discharge tray 6, a toner tank 217, a carrier tank 218, etc Is provided.

  The image forming unit 2 includes an endless, ie, annular, intermediate transfer belt 21 that is rotatable in one direction, and further, yellow (Y) and magenta (M), respectively, along the rotation direction of the intermediate transfer belt 2. Image forming units FY, FM, FC, and FB that form images with four color developers of cyan, (C), and black (B), and that are primarily transferred to the intermediate transfer belt 21, and the primary on the intermediate transfer belt 21 A carrier removing unit 22 that removes excess carrier from the transferred image, a belt cleaning unit 23 that removes the developer from the intermediate transfer belt 21 after transfer by the transfer unit 4, and the like are provided.

  More specifically, the image forming unit 2 includes a belt driving roller 211, a first driven roller 212, and a back side of the intermediate transfer belt 21 (inner side of the ring shape of the intermediate transfer belt 21) so as to contact the intermediate transfer belt 21. The second driven roller 213 is provided in this order along the rotation direction of the intermediate transfer belt 21. The belt driving roller 211 rotates to rotate and move the intermediate transfer belt 21 clockwise, and the first and second driven rollers 212 and 213 rotate following the rotation of the belt driving roller 211. The belt driving roller 211 is provided so as to face the transfer roller 41 of the transfer unit 4 with the intermediate transfer belt 21 interposed therebetween, and constitutes the transfer unit 4 together with the transfer roller 41.

  The image forming units FY, FM, FC, and FB are arranged in this order from the second driven roller 213 toward the belt driving roller 211. The arrangement order of the image forming units is not limited to this, but this arrangement is preferable in consideration of the influence on the completed image due to the color mixture of each color. Details of the image forming unit will be described later.

  The carrier removing unit 22 is provided further downstream of the most downstream image forming unit FB and upstream of the belt driving roller 211 in the moving direction of the intermediate transfer belt 21. The carrier removing unit 22 is in contact with the surface of the intermediate transfer belt 21 to remove the carrier liquid, the carrier removing roller 22a, the collecting device 22b for collecting the carrier liquid adhering to the carrier removing roller 22a, and the intermediate transfer belt 21. Is provided with a counter roller 22c arranged to face the carrier removing roller 22a. It is preferable that the surface of the carrier removal roller 22 a has higher wettability than the surface of the intermediate transfer belt 21.

  The belt cleaning unit 23 is disposed downstream of the transfer unit 4 in the moving direction of the intermediate transfer belt 21 and upstream of the most upstream developing unit FY among the image forming units. More specifically, the belt cleaning unit 23 includes a blade 23 a that contacts the intermediate transfer belt 21 in the vicinity of the second driven roller 213, and a storage case 23 b that stores the developer scraped by the blade 23 a.

  As shown in FIG. 1, the sheet storage unit 3 is a part that stores a sheet on which a toner image is fixed, and is disposed below the printer 1. The sheet storage unit 3 includes a sheet feeding cassette 31 that stores sheets, a sheet feeding unit 222 that supplies the uppermost sheet P in the sheet feeding cassette 31 to the sheet transport unit 7, and the like.

  The transfer unit 4 includes the belt driving roller 211 described above, the transfer roller 41 facing the belt driving roller 211 with the intermediate transfer belt 21 interposed therebetween, and the like. The transfer unit 4 includes a bias application unit (not shown) that applies a bias to the transfer roller 41, and an image is transferred from the intermediate transfer belt 21 to the paper P by this bias.

  The fixing unit 5 is a part for fixing the toner image on the paper P, and is disposed downstream of the transfer unit 4 in the paper transport direction. The fixing unit 5 includes a heating roller 51 in contact with the toner image transferred to the sheet, a pressure roller 52 disposed to face the heating roller 52, and the like.

  The paper transport unit 7 includes a plurality of roller pairs and the like.

  The developer tank 217 and the carrier liquid tank 218 store a high-concentration developer and a carrier liquid containing toner at a high concentration, respectively.

  The printer 1 further includes a developer circulation processing device (not shown). The developer circulating apparatus is supplied with a high-concentration developer and a carrier liquid from a developer tank 217 and a carrier liquid tank 218. The high-concentration developer and the carrier liquid are mixed in the developer circulation processing device, the concentration is adjusted, and then supplied as a developer to the developing device 9 via a developer supply unit 94 described later.

<2. Image forming unit>
(2-1) Outline of Image Forming Unit Since the image forming units FY, FM, FC, and FB have substantially the same configuration, the image forming unit FY for yellow will be described below with reference to FIG. Description of other image forming units is omitted. FIG. 2 is a front view showing a main configuration of the developing unit FY.

  As shown in FIG. 2, the developing unit FY includes a photosensitive drum 10 as a rotatable image carrier, and a charging unit 11 that charges the photosensitive drum 10 uniformly along the rotation direction is charged. An exposure unit 12 that draws an electrostatic latent image by irradiating the surface of the photosensitive drum 10 with light, a developing device 9 that develops the electrostatic latent image with a developer, and a primary transfer that transfers the developed image to the intermediate transfer belt 21. A roller 13, a drum cleaning unit 14 that removes the developer remaining on the photosensitive drum 10 after transfer, and a light source are provided, and the surface of the photosensitive drum 10 after cleaning is discharged by light from the light source to form the next image. The neutralization unit 15 provided in the

(2-2) Developing device 9
The developing device 9 includes a first roller for supplying a developer to the electrostatic latent image on the image carrier, a second roller for attaching the developer to the first roller, and a first roller for attaching the developer to the second roller. As an example of each of the three rollers, a developing roller 91, a supply roller 92, and a support roller 93 are provided. The developing device 9 further includes a developer supplying unit 94, a developer removing device 96, a developer charging device 97, a thermometer 98 as a temperature measuring unit, and a developing container 99 that accommodates these members. Prepare.

  The developing roller 91 is disposed so as to be in contact with the photosensitive drum 10 and rotates to supply the developer to the photosensitive drum 10.

  The supply roller 92 is for supplying developer to the developing roller 91, and is arranged in contact with the lower portion of the developing roller 91.

  The support roller 93 is a member for supporting the developer together with the supply roller 92, and is disposed so as to contact the supply roller 92. A doctor blade 921 is brought into contact with the supply roller 92. In order to supply the developing roller 91 by the doctor blade 921, the layer thickness of the developer carried on the supply roller 92 is regulated to a predetermined value.

  The developer supply unit 94 is a member for supplying the developer to the support roller 93 near the contact portion between the supply roller 92 and the support roller 93.

  The developer removing device 96 is a device for removing the developer not supplied to the photosensitive drum 10 but remaining on the developing roller 91, and has a developer removing blade 961. The developer on the developing roller 91 is scraped off by the developer removing blade 961.

  The developer charging device 97 is a device for charging the toner in the developer carried on the developing roller 91, and is disposed in the vicinity of the developing roller 91.

  The thermometer 98 is disposed in the vicinity of the developing roller 91 on the inner wall of the developing container 99. In this embodiment, a radiant heat thermometer that detects heat radiated from an object is used. However, if the measurement result of the thermometer 98 reflects the temperature of the developer, more specifically, the viscosity of the developer on the developing roller 91, the form of the thermometer 98 in the printer 100 The installation position and the like are not limited to this embodiment. For example, the thermometer 98 may be provided on the outer wall of the developing container 99, or the temperature inside the printer 100 may be measured outside the developing device 9. In addition, as a temperature measurement unit, a temperature sensor may be provided in place of the thermometer 98 at a position in direct contact with the developer in the developer supply unit 94.

(2-3) Drive and Control Mechanism The drive mechanism of each roller of the developing device 9 will be described with reference to FIGS. 3 and 4 are drawings showing a developing roller 91, a supply roller 92, a support roller 93, and a driving mechanism for these rollers. FIG. 3 shows a case where the viscosity of the developer is small, and FIG. The case where the viscosity is large is shown.

  As shown in FIG. 3, the developing device 9 includes a development system drive unit 101 that rotationally drives the development roller 91, and a supply system drive unit 102 that rotationally drives the supply roller 92 and the support roller 93. A cam 103 is attached to the rotation shaft of the supply roller 92, and a cam 104 that contacts the cam 103 is attached to the rotation shaft of the support roller 93. The development system drive unit 101 is directly connected to the rotation shaft of the development roller 91, and the supply system drive unit 102 is directly connected to the rotation shaft of the supply roller 92. When the supply roller 92 is rotated by the supply system driving unit 102, the support roller is also driven through the cams 103 and 104. The cams 103 and 104 are connected to a cam switching unit 105, and the cam switching unit 105 adjusts the gap between the supply roller 92 and the support roller 93 through the cams 103 and 104 in two stages.

  The cam switching unit 105 increases the gap as the developer viscosity increases, and decreases the gap as the viscosity decreases. As a specific configuration, the cam switching unit 105 switches the gap based on the measurement result of the thermometer 98. Specifically, when the measurement result of the thermometer 98 is a predetermined reference temperature (for example, 25 ° C.) or more, the gap is reduced as shown in FIG. 3, and when the measurement result of the thermometer 98 is less than the reference temperature, The gap is increased as shown in FIG.

  As the temperature increases, the viscosity of the developer decreases. Therefore, if the gap is large, it is difficult for the developer to adhere to the supply roller 92. Further, as the temperature is lowered, the viscosity of the developer increases, and if the gap is small, the developer layer on the supply roller 92 is difficult to be uniform, and unnecessary lines (streaks) may appear in the image. On the other hand, as described above, since the cam switching unit 105 adjusts the size of the gap according to the temperature, a good image can be maintained regardless of the temperature.

  In this embodiment, the gap is adjusted based on the temperature. However, as is clear from the above description, the temperature is only one of the factors affecting the viscosity of the developer. Therefore, in place of the thermometer 98, a viscometer that measures the viscosity of the developer itself can be used as appropriate.

  Further, as a means for measuring the viscosity, for example, a viscosity measuring unit including a stirring blade arranged so as to be in contact with the developer, a motor, and a current detecting unit for detecting a current value change of the motor can be used. The stirring blade may be provided in the developer supply unit 94, for example. Alternatively, a certain amount of developer may be stored in the developing container 99 so that the support roller 93 is not immersed, and the stirring blades may be immersed in the developer stored in the developing container 99. The viscosity measuring unit can detect the change in the viscosity of the developer indirectly from the detection result of the current detection unit by rotating the stirring blade by the motor.

  Further, the control mechanism for causing the cam switching unit 105 to operate according to the temperature may be realized by hardware resources or software resources. In this embodiment, this control mechanism is realized by software resources using a CPU (Central Processing Unit) or the like. FIG. 5 is a block diagram showing the hardware configuration of the printer 1.

  As shown in FIG. 5, in addition to the above-described members, the printer 1 includes a CPU 201, a RAM (Random Access Memory) 202, a ROM (Read Only Memory) 203, an HDD (Hard Disk Drive) 204, and driving units for the printing. Corresponding driver 205 is provided. These members and the members such as the image forming unit 2 described with reference to FIG. 1 are connected to each other via an internal bus 206.

  The CPU 201 uses, for example, the RAM 202 as a work area, executes programs stored in the ROM 203, the HDD 204, and the like, and exchanges data and commands with the driver 205 based on the execution results. The operation of each of the illustrated driving units is controlled.

  In this embodiment, the control for the cam switching unit 105 is realized by the CPU 201 executing a program. A reference temperature is stored in a storage device such as the HDD 204, and the CPU 201 compares the temperature measured by the thermometer 98 with the reference temperature, and issues a gap switching instruction to the cam switching unit 105.

  The cam switching unit 105 may perform control as shown in Table 1. In Table 1, “Gap” is the size of the gap between the supply roller 92 and the support roller 93, and “Before correction” is a streak on the formed image when the gap is maintained at 0.05 mm. “After correction” is the presence or absence of streaking when the gap is switched from 0.05 mm to 0.1 mm in accordance with a decrease in temperature.

  As shown in Table 1, the generation of streaks was suppressed by switching the gap from 0.05 mm to 0.1 mm when the temperature was lower than 25 ° C. Further, by switching the gap, a good image was obtained at any temperature.

<3. Other forms>
In the printer 1, the developing device 9 can be replaced with a developing device 109 shown in FIG. FIG. 6 is a front view showing a main configuration of the developing device 109. In FIG. 6, members having the same functions as those of the developing device 9 are denoted by the same reference numerals and description thereof is omitted.

  The developing device 109 includes a developing container 199 that stores a developer in place of the developing container 99, and a pumping roller 193 disposed in contact with the developer in the developing container 199 and a pumping roller 193 in the developing container 199. The developing device is substantially the same as the above-described developing device except that a regulating roller 192 provided so as to be opposed to is provided instead of the support roller 93 and the supply roller 92. That is, in the developing device 109, the developer pumped up by the pumping roller 193 is supplied to the developing roller 91 via the regulation roller 192.

  3 and 4, the supply roller 92 can be replaced with a regulating roller 192, and the support roller 93 can be replaced with a scooping roller 193. That is, the gap between the regulating roller 192 and the pumping roller 193 is switched so that it is small when the temperature is equal to or higher than the reference value and is large when the temperature is lower than the reference value.

FIG. 3 is a front view illustrating a main configuration of the printer 1. FIG. 3 is a front view illustrating a main configuration of a developing unit FY. The drawing which shows the roller in the developing device 9 and its drive mechanism. The drawing which shows the roller in the developing device 9 and its drive mechanism. 2 is a block diagram showing a hardware configuration of the printer 1. FIG. FIG. 3 is a front view illustrating a main configuration of the developing device 109.

Explanation of symbols

1 Printer (image forming device)
10 Photosensitive drum 9 Developing device 91 Developing roller (first roller)
92 Supply roller (second roller)
93 Support roller (third roller)
98 thermometer 109 developing device 192 regulating roller (second roller)
193 Pumping roller (third roller)

Claims (3)

A developing device for developing the electrostatic latent image by supplying a developer containing toner and a liquid carrier to an image carrier capable of carrying the electrostatic latent image,
A first roller disposed to face the image carrier and supplying a developer to the electrostatic latent image;
A second roller arranged to face the first roller and depositing developer on the first roller;
A third roller that is arranged to face the second roller and attaches developer to the second roller;
A developing device comprising: a gap adjusting unit that increases a gap between the second roller and the third roller as the viscosity of the developer increases. A developing device for developing the electrostatic latent image by supplying a developer containing toner and a liquid carrier to an image carrier capable of carrying the electrostatic latent image,
A first roller disposed to face the image carrier and supplying a developer to the electrostatic latent image;
A second roller arranged to face the first roller and depositing developer on the first roller;
A third roller that is arranged to face the second roller and attaches developer to the second roller;
A temperature measuring unit for measuring the temperature of the developer;
A developing device comprising: a gap adjusting unit that increases a gap between the second roller and the third roller as the temperature of the developer decreases from the measurement result of the temperature measuring unit. An image carrier capable of carrying an electrostatic latent image;
A first roller arranged to face the image carrier and supplying developer to the electrostatic latent image; and a second roller arranged to face the first roller and attach the developer to the first roller. Laura,
A third roller that is arranged to face the second roller and attaches developer to the second roller;
An image forming apparatus comprising: a gap adjusting unit that increases a gap between the second roller and the third roller as the viscosity of the developer increases.

Images