JP4717224B2 - Image forming unit and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming unit used in a copying machine or a printer using an electrophotographic system, and an image forming apparatus that forms an image on a transfer material using the image forming unit.
[0002]
[Prior art]
In an electrophotographic image forming apparatus, an image is formed by transferring a toner image formed on a photosensitive drum, which is an image carrier, onto a transfer material. In a color image forming apparatus, the image is sequentially formed on a photosensitive drum. An image forming apparatus has been used in which each color toner image to be formed is superimposed and transferred onto an intermediate transfer member, and the color image is collectively transferred onto a transfer material. In this case, in order to make it easy to handle a member that is deteriorated or wears out of the photosensitive drum, a unit that is unitized and detachable from the apparatus main body is widely used.
[0003]
A color image forming apparatus using such an intermediate transfer member is disclosed in JP-A-8-137181, JP-A-10-301464, and JP-A-11-295998. Are configured so as to be detachable when the unit life is reached, or when jamming (paper jam) processing is performed.
[0004]
Here, Japanese Patent Application Laid-Open No. 8-137181 is configured such that the movable frame on the front side of the apparatus is opened by rotating downward on the front side of the apparatus, and the photosensitive unit and the intermediate transfer unit are respectively attached and detached from above. In Japanese Patent Laid-Open No. 10-301464, the photosensitive member unit and the intermediate transfer member unit are detachably attached to a movable body that can be pulled out horizontally on the front surface of the apparatus main body. In these two conventional examples, the unit is attached and detached in a direction parallel to the transfer material conveyance direction.
[0005]
On the other hand, in Japanese Patent Laid-Open No. 11-295998, the unit is slidably attached and detached in a direction perpendicular to the transfer material conveyance direction.
[0006]
In the above conventional example, the intermediate transfer member is an endless belt, and is suspended and stretched by three or more rollers. The intermediate transfer belt is a driving roller that rotationally drives the belt, and a tension that applies tension to the belt. It is composed of a roller and a secondary transfer counter roller facing the secondary transfer means.
[0007]
Further, the primary transfer unit facing the photosensitive drum with the photosensitive drum as the image carrier and the intermediate transfer belt interposed therebetween is positioned upstream of the intermediate transfer belt conveyance direction (so-called belt tension side) as viewed from the driving roller. is doing.
[0008]
Furthermore, the diameter of the roller as the suspension tension member is large and small.
[0009]
FIG. 11 is an explanatory diagram of a color image forming apparatus according to a conventional example using an intermediate transfer belt. In FIG. 11, an intermediate transfer unit 504 is composed of three rollers: a driving roller 502, a secondary transfer counter roller 505, and a tension roller 506 that applies a predetermined tension to the intermediate transfer belt 508 by a spring (not shown). A primary transfer roller 507 is provided at a position that is suspended and opposed to the photosensitive drum 501.
[0010]
As shown in FIG. 11, the drive roller 502 rotates in the right direction (clockwise), and the intermediate transfer belt 508 also rotates in the clockwise direction as indicated by an arrow. The secondary transfer counter roller 505 and the tension roller 506 are configured to rotate following the intermediate transfer belt 508.
[0011]
As shown in FIG. 11, the photosensitive drum 501 of the photosensitive drum cartridge 503 is disposed between the intermediate transfer belt driving roller 502 and the tension roller 506 at L1, and the primary transfer roller 507 is opposed to the intermediate transfer belt 508. Has been.
[0012]
L1 where the primary transfer site exists is the upstream side of the intermediate transfer belt conveyance direction as seen from the rotation direction of the intermediate transfer belt drive roller 502, and is the so-called belt tension side.
[0013]
This is an arrangement in consideration of the fact that the rotational transfer speed variation of the intermediate transfer belt 508 is more stable on the belt tension side L1 than on the loose side L2 of the intermediate transfer belt 508.
[0014]
That is, the process of developing the electrostatic latent image formed on the photosensitive drum 501 with toner of any color and primary transferring the obtained toner image to the rotating intermediate transfer belt 508 is repeated for each of the different colors. This is because when the color superimposed toner image is formed on the transfer belt 508, the conveyance speed of the intermediate transfer belt 508 must be stable in order to reduce the color misregistration for each color toner.
[0015]
Further, the circumferential length Lb of the intermediate transfer belt 508 is substantially an integral multiple of the circumferential length Ld of the photosensitive drum 501 and is also a substantially integral multiple of the circumferential length Lr of the intermediate transfer roller driving roller 502. The primary transfer of each color toner is started from a predetermined position of the intermediate transfer belt 508 with a constant cycle of a change in peripheral speed in one rotation cycle due to the shake of the drum 501 and a change in conveyance speed due to the shake of the driving roller 502 of the intermediate transfer belt 508. As a result, the phase of color misregistration for each color toner overlaps on the intermediate transfer belt 508, and a color image with little color misregistration is obtained by being collectively transferred to the transfer material by the secondary transfer roller 509. ing.
[0016]
In FIG. 11, if the diameter D1 of the photosensitive drum 501 is 47 mm, the photosensitive drum circumferential length Ld = 47π mm, and the circumferential length Ld1 from the exposure position A to the primary transfer position B of the photosensitive drum 501 is about 63 mm. To do.
[0017]
The peripheral length Lb of the intermediate transfer belt 508 is 47π × 2≈295.3 mm or 47π × 3≈442.96 mm. If the transfer material is an A4 size sheet, the sheet length is 297 mm and the exposure position of the photosensitive drum 501 A belt length of 360 mm or more is required as a minimum, which is obtained by adding the distance 63 mm at which A rotates to the primary transfer position B.
[0018]
Further, the belt length from the primary transfer position B of the intermediate transfer belt 508 to the secondary transfer position C in the belt conveyance direction needs to be at least 297 mm or more of the A4 size paper length.
[0019]
Considering the time for switching between the color toner developing devices, the pressure applied to the photosensitive drum 501 of the toner developing device, the separation, etc. The proper circumference Lb is 442.96mm.
[0020]
Further, the peripheral length Lr of the intermediate transfer belt driving roller 502 is 442.96 / 5≈88.593 mm, and the driving roller diameter D2 is 88.893 / π≈28.2 mm.
[0021]
[Problems to be solved by the invention]
The conventional example described above has the following problems. That is, the part where the primary transfer is performed is located on the tension side on the intermediate transfer belt 508, and the position where the secondary transfer is performed in consideration of the transfer path of the transfer material, while further satisfying the above dimensional relationships, A shape in which the intermediate transfer belt 508 is suspended in a compact manner must be devised.
[0022]
However, the intermediate transfer belt 508 faces the driving roller 502 and the secondary transfer roller 509, forms a nip with the secondary transfer roller 509, and conveys the transfer material to the secondary transfer counter roller 505 and the intermediate transfer belt 508. The shape is such that it is stretched around three or more rollers such as a tension roller 506 for applying tension. When a charging unit for charging the toner transferred to the intermediate transfer belt 508 is brought into contact with the belt 508, it is necessary to provide a belt support roller at a position facing the charging unit.
[0023]
For this reason, the intermediate transfer belt 508 requires a large number of rollers with high dimensional accuracy, and the frame itself constituting the intermediate transfer belt unit needs to be complicated and highly accurate. As a result, the intermediate transfer unit and the image forming apparatus main body are required. Was the cause of the increase in size and cost.
[0024]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming unit that can be reduced in size and cost by reducing the number of parts and an image forming apparatus using the image forming unit.
[0025]
[Means for Solving the Problems]
In order to achieve the above object, a typical configuration according to the present invention is such that a toner image primarily transferred from an image carrier to an intermediate transfer belt at a primary transfer portion is secondarily transferred from an intermediate transfer belt to a transfer material at a secondary transfer portion. an image forming unit detachably mountable to an image forming apparatus main body for transferring an image bearing member for bearing a toner image, an intermediate transfer belt of endless toner image on said image bearing member is transferred, the intermediate transfer belt a plurality of rotary members for stretching a has a primary transfer member to form a primary transfer portion together with the image carrier via the intermediate transfer belt, one said intermediate transfer of the plurality of rotary members A driving roller for rotating the belt, wherein the primary transfer portion is formed downstream of the driving roller in the rotation direction of the intermediate transfer belt, and the image carrier and the intermediate transfer belt In the image forming unit detachably attached to the image forming apparatus main body, the intermediate transfer belt is stretched only by two rollers, a driven roller and a driven roller driven by the rotation of the intermediate transfer belt. The driving roller includes a secondary transfer member that contacts the outer surface of the intermediate transfer belt to form the secondary transfer portion, and an outer surface of the intermediate transfer belt for collecting toner remaining on the intermediate transfer belt And a cleaning roller that is in contact with each of the cleaning members that are in contact with each other via the intermediate transfer belt, and is grounded as a counter electrode for each of the secondary transfer member and the cleaning member, When the image forming unit is mounted on the main body of the image forming apparatus, the driving roller is disposed below the driven roller. Characterized in that that.
[0026]
In the above configuration, by using one of the rotating bodies that suspend and stretch the belt member as a common electrode of the plurality of electrode members, the belt member can be supported by the two rotating members. By reducing the number of components, it is possible to reduce the size of the entire apparatus body, improve assembly, and reduce costs.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Next, an image forming unit and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
[0028]
[First Embodiment]
FIG. 1 is a longitudinal cross-sectional explanatory view showing a schematic configuration of a four-color full-color laser beam printer in the electrophotographic image forming apparatus A according to the first embodiment, and the right side of the figure is the front side of the apparatus.
[0029]
{Overall configuration of image forming apparatus}
In synchronization with the rotation of the intermediate transfer belt 5a as an endless belt member as an intermediate transfer member, the photosensitive drum 1 as an image carrier is rotated in the direction of an arrow (counterclockwise) in FIG. The surface is uniformly charged by a charging roller 2 as a charging device, and a yellow image is irradiated by an exposure unit 3 to form a yellow electrostatic latent image on the photosensitive drum 1. Simultaneously with the formation of the electrostatic latent image, the developing device 4 is driven to place the yellow developing device 4Y at the developing position, and the photosensitive drum 1 is charged so that yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. A yellow toner is attached to the electrostatic latent image and developed by applying a voltage having the same polarity and substantially the same potential. Thereafter, a voltage having a polarity opposite to that of the toner is applied to a pressing roller (primary transfer roller) 5j of the intermediate transfer belt 5a to primarily transfer the yellow toner image on the photosensitive drum 1 onto the intermediate transfer belt 5a.
[0030]
When the primary transfer of the yellow toner image is completed as described above, the next developing device rotates and is positioned at the development position facing the photosensitive drum 1, and in the same manner as in the case of yellow, magenta, cyan, and For each color of black, formation of an electrostatic latent image, development by the color developing devices 4M, 4C, and 4BK, and primary transfer are sequentially performed, and the four color toner images are superimposed on the intermediate transfer belt 5a.
[0031]
During this time, the secondary transfer roller 11 as the secondary transfer means is in a non-contact state with the intermediate transfer belt 5a. At this time, the charging roller 5f as the cleaning charging unit is also in a non-contact state with the intermediate transfer belt 5a.
[0032]
After the four color toner images are formed on the intermediate transfer belt 5a, the secondary transfer roller 11 is pressed against the intermediate transfer belt 5a (the state shown in FIG. 1), and further conveyed in synchronization with the rotation of the intermediate transfer belt 5a. The transfer material which is conveyed from the transfer material cassette 7a by the feeding roller 7b and the conveying roller pair 7c as means and is waiting at a predetermined position in the vicinity of the registration roller pair 7d is formed between the intermediate transfer belt 5a and the secondary transfer roller 11. It is sent out to the nip part.
[0033]
Here, immediately before the registration roller pair 7d, a pre-registration sensor 14 is provided that detects the leading edge of the transfer material S, blocks the rotational driving force of the registration roller pair 7d, and waits the transfer material S at a predetermined position. Yes.
[0034]
Further, the secondary transfer roller 11 functions as an electrode member. A voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 11, and the toner image on the intermediate transfer belt 5a is collectively displayed. Secondary transfer is performed on the surface of the transferred transfer material S. At this time, the driving roller 40 facing the secondary transfer roller 11 via the intermediate transfer belt 5 a functions as a counter electrode of the secondary transfer roller 11.
[0035]
In this way, the transfer material S that has been secondarily transferred reaches the fixing device 8 via the conveying belt unit 12, and after fixing the toner images of a plurality of colors, the transfer material S is then discharged to the discharge guide 15 by the discharge roller pair 13. Are discharged to a discharge tray 10 above the color image forming apparatus A by a discharge roller pair 9 to complete image formation.
[0036]
On the other hand, the charging roller 5f for cleaning is pressed against the intermediate transfer belt 5a after the secondary transfer, and the residual toner remaining on the intermediate transfer belt is charged with a charge opposite to that at the time of transfer (a charge having a polarity opposite to the normal charging polarity of the toner). ) To collect. In other words, the collecting unit applies a charge having a reverse polarity to the residual toner as described above, and electrostatically adheres this to the photosensitive drum 1 by the primary transfer roller 5j as the primary transfer unit, and then the photosensitive drum. It collects with the cleaning blade 6 for use. Then, the collected residual toner follows a conveyance path to be described later as waste toner and is collected and accumulated in the waste toner box 16.
[0037]
Further, when images are continuously formed on a plurality of transfer materials, the residual toner charged by the cleaning charging roller 5f is electrostatically transferred from the intermediate transfer belt 5a to the photosensitive drum 1 and at the same time. The toner image for the next transfer material formed on 1 is primarily transferred to the intermediate transfer belt 5a. Thereby, the throughput of image formation can be improved.
[0038]
{Image forming unit}
Next, a detailed description will be given of the configuration of an image forming unit that is integrated with the photosensitive drum and the intermediate transfer belt that is attached to and detached from the image forming apparatus.
[0039]
FIG. 2 is an enlarged main longitudinal sectional view showing a schematic configuration of the image forming unit of FIG. 1, and is a sectional view seen from the left side toward the front of the apparatus. FIG. 3 is a longitudinal sectional view of the image forming unit viewed from the right side toward the front of the apparatus. FIG. 4 is a cross-sectional view of the waste toner conveyance passage portion when FIG. 2 is viewed from above.
[0040]
2 to 4, in the image forming unit 5, the photosensitive drum unit 20 is disposed on the upper projection surface of the intermediate transfer belt unit 21, and the waste toner box 16 is disposed on the lower projection surface of the intermediate transfer belt unit 21. . Further, the belt driving roller 40 of the intermediate transfer belt unit 21 is provided with a cleaning charging roller portion 23 for applying a charge opposite to that at the time of transfer to the residual toner on the intermediate transfer belt 5a.
[0041]
(Photosensitive drum unit)
As shown in FIGS. 2 and 3, the photosensitive drum unit 20 holds the photosensitive drum 1 by a right bearing 206 and a left rotating support shaft 202 so that both ends can rotate freely, and through a coupling 24 at the right end. A predetermined rotational driving force is transmitted from the apparatus main body.
[0042]
The charging roller 2 is pressed against the photosensitive drum 1 with a predetermined force by a compression spring 26 via bearings 25 at both ends, and is driven to rotate. At least one of the bearings 25 is composed of a conductive member, and the surface of the photosensitive drum 1 is uniformly charged by applying a predetermined charging bias voltage from the compression spring 26 to the charging roller 2 via the bearing 25. It is like that.
[0043]
Further, as shown in FIG. 5, the end portion of the compression spring 26 extends downward from the left side surface of the photosensitive drum frame 29 to become a compression spring 327, and one end thereof is press-fitted into the boss portion of the photosensitive drum frame 29. It is fixed.
[0044]
Further, the photosensitive drum 1 is provided with a cleaning blade 6 at a predetermined position, and the residual toner on the intermediate transfer belt to which the above-described reverse charge is applied is collected on the photosensitive drum 1, It is configured to scrape together with the residual toner. The scraped waste toner is prevented from dropping onto the intermediate transfer belt 5a by the squeeze sheet 27 (see FIG. 2), and the waste toner accumulated on the bottom of the photosensitive drum frame 29 is viewed from the front of the apparatus by the rotation of the screw 28. Then, it is conveyed to the right side (in the direction of arrow C in FIG. 4).
[0045]
Thereafter, the waste toner is conveyed to the right side surface (as viewed from the front side of the apparatus) of the photosensitive drum unit 20 by the screw 28, and is slid down and accumulated in the waste toner box 16. The photosensitive drum unit 20 is also provided with a drum shutter 19 that opens and closes in conjunction with an operation of attaching to and detaching from the image forming apparatus main body.
[0046]
(Intermediate transfer belt unit)
Next, the configuration of the intermediate transfer belt unit 21 will be described. The intermediate transfer belt 5a is stretched around a frame 45 including a handle 61 by a driving roller 40 and a driven roller 41 as two rotating members.
[0047]
The driving roller 40 applies a rotational force to the intermediate transfer belt 5a, and is rotatably fixed to the frame 45. The driving roller 40 is composed of a metal pipe or the like, and a surface layer having a high frictional force such as a rubber layer having a predetermined conductivity is formed and functions as an electrode.
[0048]
As shown in FIGS. 2 to 4, the driving roller 40 is supported by a right bearing 205 and a left bearing 201 so that both ends thereof are rotatable, and a predetermined distance from the apparatus main body via a coupling 42 (see FIG. 3) at the right end. A rotational driving force is transmitted. The left bearing 201 is made of a conductive member and is grounded to the image forming apparatus main body.
[0049]
The bearings 43 at both ends of the driven roller are provided with compression springs 44, and are attached so as to be movable in a direction in which a predetermined tension is applied to the intermediate transfer belt 5a.
[0050]
A primary transfer roller 5j is provided at a position facing the photosensitive drum 1 across the intermediate transfer belt 5a, and is pressed by a predetermined force by a compression spring 47 through bearings 46 at both ends so as to be driven to rotate. It has become.
[0051]
At least one of the bearings 46 is formed of a conductive member, and the toner on the surface of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a by applying a predetermined charging bias voltage to the primary transfer roller 5j.
[0052]
As shown in FIG. 6, a primary transfer roller high-voltage contact plate 401 is provided on the left side surface of the intermediate transfer body frame 45, its end 401a is connected to the compression spring 47, and the other end 401b is the middle. It is fixed to the lower left part of the transfer body frame 45 by a hook portion 401c.
[0053]
As shown in FIG. 2, a cleaning charging roller portion 23 is provided at a position facing the intermediate transfer belt driving roller 40 to apply a charge opposite to that at the time of transfer to the residual toner on the intermediate transfer belt. .
[0054]
The cleaning charging roller 5f is brought into pressure contact with a predetermined force by a compression spring 52 via bearings 51 at both ends, and is driven to rotate. At least one of the bearings 51 is composed of a conductive member and functions as an electrode member. That is, by applying a voltage opposite to that at the time of transfer to the cleaning charging roller 5f, a charge opposite to that at the time of transfer is applied to the residual toner on the intermediate transfer belt 5a, and the photosensitive drum 1 electrostatically attracts the drum surface. Collected and accumulated in the waste toner box 16 as described above.
[0055]
When the charging roller 5f is charged, the driving roller 40 facing the intermediate roller 5a via the intermediate transfer belt 5a functions as a counter electrode of the charging roller 5f. The drive roller 40 functions as a common electrode common to the secondary transfer roller 11 and the charging roller 5f, and it is not necessary to provide a counter electrode for each of the secondary transfer roller 11 and the charging roller 5f. The intermediate transfer belt unit 21 can be downsized.
[0056]
As shown in FIG. 1, in a state where the image forming unit 5 is loaded in the apparatus main body, the charging roller 5f and the secondary transfer roller 11 are disposed in the vicinity of the driving roller 40 serving as a counter electrode. The roller 5f is disposed downstream of the secondary transfer roller 11 in the rotation direction of the intermediate transfer belt 5a and upstream of the primary transfer portion in the rotation direction. For this reason, it is possible to shorten the time from the secondary transfer until the residual toner on the intermediate transfer belt is charged by the charging roller 5f, and the throughput of image formation when images are continuously formed on a plurality of transfer materials. Can be prevented.
[0057]
As shown in FIG. 4, the compression spring 52 is connected to the end 403a of the cleaning charging roller high-voltage contact plate 403 constituting the cleaning means, and the other end 403b is connected to the left side of the intermediate transfer member frame 45 by the hook 403c. It is fixed at the bottom.
[0058]
Further, as shown in FIGS. 4 and 5, a charging roller high-voltage contact plate 402 for supplying a high voltage to the charging roller 2 is provided on the inner side of the left cover 208 of the intermediate transfer member frame 45. The portion 402a is fixed to the upper surface of the intermediate transfer member frame 45, extends downward from the left side surface of the photosensitive drum frame 29 and is connected to the compression spring 327, and the other end 402b is connected to the intermediate transfer member frame by the hook portion 402c. It is fixed to the lower left side of 45. Thereby, electric power from the apparatus main body is supplied to one end portion 402b of the charging roller high-voltage contact plate 402, and the other end portion 402a of the contact plate 402 and the compression spring 327 are electrically connected as electrical contact means. Therefore, the toner is supplied to the charging roller 2 via the compression spring 26 and the bearing 25.
[0059]
In this way, the supply contact portion of each bias voltage from the image forming apparatus main body to (1) the charging roller 2, (2) the primary transfer roller 5j, and (3) the cleaning means is on the left side of the intermediate transfer belt unit 21 ( Outside the image forming area width) are gathered in the lower parts 402b, 401b and 403b.
[0060]
{Unit configuration of image forming unit}
Next, the frame configuration of the image forming unit 5 will be described in detail. The frame structure is roughly divided into two. First, as shown in FIGS. 3 and 4, the first unit includes a photosensitive drum frame 29 that is integrated with the waste toner box 16, a photosensitive drum 1, a right bearing 206, a left rotating spindle 202, and a charging roller 2. , A photosensitive drum unit 20 (a portion surrounded by a two-dot chain line in FIG. 4), which includes a cleaning blade 6, a screw 28, and a drum shutter 19 as main components. Further, as shown in FIG. 2, the second unit has an intermediate transfer belt 5 a suspended on an intermediate transfer body frame 45 by a driving roller 40 and a driven roller 41 and opposed to the photosensitive drum 1. The intermediate transfer belt unit 21 has a primary transfer roller 5j on the inner side and a cleaning charging roller 5f on the driving roller 40.
[0061]
As shown in FIGS. 2 and 3, the two units have protrusions 71 provided at the left and right ends of the photosensitive drum frame 29 inserted into positioning holes 72 provided in the intermediate transfer member frame 45, respectively. On the other hand, a hook 73 of a snap-fit type hook provided at the center in the width direction of the photosensitive drum frame 29 is fitted and connected to a lock hole 74 of the intermediate transfer member frame 45.
[0062]
Here, the positioning hole 72 and the lock hole 74 provided in the intermediate transfer member frame 45 are formed by a predetermined amount larger than the protrusion 71 provided in the photosensitive drum frame 29 and the hook 73 of the hook. Thus, a predetermined amount of relative position movement is possible between the photosensitive drum unit 20 and the intermediate transfer belt unit 21. Further, the positioning hole 72 is provided with a tapered portion 72a (see FIG. 8) so that it can be easily attached and detached.
[0063]
3, the hook claw 73 of the photosensitive drum unit 20 is pushed in the direction of arrow D to remove it from the lock hole 74 of the intermediate transfer belt unit 21, and the photosensitive drum unit 20 is removed as shown in FIG. By rotating in the direction of arrow E, the photosensitive drum unit 20 and the intermediate transfer belt unit 21 can be divided as shown in FIGS.
[0064]
When connecting the separated units 20 and 21, the protrusion 71 of the photosensitive drum unit 20 is inserted into the positioning hole 72 of the intermediate transfer belt unit 21 and rotated in the direction opposite to the arrow E in FIG. Then, by pushing the hook claw 73 into the lock hole 74, the two units 20, 21 are connected.
[0065]
At this time, the bias voltage supply path to the charging roller 2 is connected to an end portion 402a of the charging roller high-voltage contact plate 402 provided on the intermediate transfer belt unit 21 side and a compression spring 327 provided on the photosensitive drum unit 20 side. It is configured to be separated.
[0066]
As described above, since the photosensitive drum unit 20 and the intermediate transfer belt unit 21 can be separated, when only the photosensitive drum 1 or only the intermediate transfer belt 5a reaches the end of its life, only the unit that has reached the end of its life is used. It can be exchanged. For this reason, when the lifetimes of the photosensitive drum 1 and the intermediate transfer belt 5a are different, the cost burden on the user is reduced.
[0067]
{Means for mounting the unit on the device body}
Next, a configuration for attaching and detaching the image forming unit 5 to and from the image forming apparatus main body A and positioning and fixing the image forming unit 5 to a predetermined position will be described with reference to FIG.
[0068]
When the upper cover 60 of the color image forming apparatus main body A is opened, it is fitted to a coupling 24 (see FIG. 3) that is provided on a support portion 302 that supports the photosensitive drum bearing and transmits the rotational driving force to the photosensitive drum 1. And a coupling that is provided on a support portion 303 that supports the bearing portion of the intermediate transfer belt drive shaft and that is fitted to a coupling 42 (see FIG. 3) that transmits a rotational driving force to the intermediate transfer belt drive roller. However, each slides in the axial direction and is retracted (disconnected state). It should be noted that a well-known configuration may be used as the retracting configuration of the coupling interlocking with the upper lid 60.
[0069]
A photosensitive drum guide rail 300 and an intermediate transfer member guide rail 301 are provided on both sides of the apparatus main body with a step γ. The step γ is the step γ between the drum bearing 206 and the rotation spindle 202 of the image forming unit and the bearings 201 and 205 of the intermediate transfer belt driving roller shown in FIG.
[0070]
The photosensitive drum right bearing 206 and the left rotation spindle 202 of the image forming unit 5 are moved to the photosensitive drum guide rail 300, the right bearing 205 and the left bearing 201 of the intermediate transfer belt drive roller, and the protrusions provided on the left and right side covers. The parts 203 and 204 (see FIG. 4) are inserted on the intermediate transfer member guide rail 301 while being slid.
[0071]
Eventually, the photosensitive drum right bearing 206 and the left rotation support shaft 202 fall into the support portion 302 that supports the photosensitive drum bearing, and the right bearing 205 and the left bearing 201 of the intermediate transfer belt drive roller are the intermediate transfer belt drive shaft. The projections 203 and 204 provided on the left and right side covers of the image forming unit fall into the positioning grooves 304, respectively, and as shown in FIG. , 306, 307 are pressed against the positioning of the apparatus main body frame and fixed.
[0072]
In the image forming unit 5 of the above-described embodiment, the photosensitive drum unit 20 and the intermediate transfer belt unit can be separated. However, both units may be configured as an integral unit that cannot be separated.
[0073]
Further, in the image forming unit 5 of the above-described embodiment, the intermediate transfer belt 5a is supported by the two rollers of the driving roller and the driven roller. However, this may be supported by three or more rollers. Good.
[0074]
In the above-described embodiment, the color image forming apparatus that forms the color image by loading the image forming unit 5 is exemplified. However, the image forming unit according to the present invention is also used in the image forming apparatus that forms a monochrome image. be able to.
[0075]
【The invention's effect】
As described above, the present invention makes it possible to support the belt member with the two rotating members by using one of the rotating bodies that suspend and stretch the belt member as the common electrode of the plurality of electrode members. By reducing the number of component parts, it is possible to reduce the size of the entire apparatus body, improve assembly, and reduce costs.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a main longitudinal section of an electrophotographic color image forming apparatus embodying the present invention.
FIG. 2 is a left side main longitudinal cross-sectional explanatory view of an image forming unit integrally configured with a photosensitive drum and an intermediate transfer belt according to the present invention.
3 is a main longitudinal cross-sectional explanatory view of the image forming unit of FIG. 2 as viewed from the right side.
4 is a cross-sectional explanatory view of the image forming unit of FIG. 2 as viewed from above.
FIG. 5 is an explanatory cross-sectional view showing a bias voltage supply path to a charging roller for charging a photosensitive drum.
FIG. 6 is an explanatory cross-sectional view showing a bias voltage supply path to the primary transfer roller.
FIG. 7 is an explanatory diagram illustrating a state of a high-voltage contact portion when a photoconductor unit and an intermediate transfer body unit are divided.
FIG. 8 is an explanatory diagram of an intermediate transfer body unit.
FIG. 9 is an explanatory diagram of a photoreceptor unit.
FIG. 10 is an explanatory diagram illustrating a state in which the image forming unit is attached to and detached from the apparatus main body.
FIG. 11 is an explanatory diagram of an image forming apparatus according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 2 ... Charging roller 3 ... Exposure means 4 ... Developing device 4Y, 4M, 4C, 4BK ... Color developing device 5 ... Image forming unit 5a ... Intermediate transfer belt 5f ... Charging roller 5j ... Primary transfer roller 6 ... Cleaning Blade 7a ... Transfer material cassette 7b ... Feeding roller 7c ... Conveying roller pair 7d ... Registration roller pair 8 ... Fixer 9 ... Discharge roller pair
10… discharge tray
11… Secondary transfer roller
12… Conveyor belt unit
13… Rear discharge roller pair
14… Sensor before registration
15… discharge guide
16… Waste toner box
17… High-voltage power supply board
17a ... Positioning boss
19… Drum shutter
20… Photoreceptor drum unit
21 ... Intermediate transfer belt unit
23… Cleaning charging roller
24… Coupling
25… Bearing
26… Compression spring
27… Squish sheet
28 ... Screw
29… Photoreceptor drum frame
40… Drive roller
41… driven roller
42… Coupling
43… Bearing
44… Compression spring
45… Intermediate transfer member frame
46… Bearing
47… Compression spring
51… Bearings
52… Compression spring
60… Top lid
61 ... handle part
71… Projection
72… Positioning hole
72a ... Taper part
73 ... nail
74… Lock hole
201… Left side bearing
202… Left side pivot
203,204 ... Projection
205… Right side bearing
206… Right side bearing
208… Left cover
300… Guide rail for photosensitive drum
301… Guide rail for intermediate transfer member
302… Supporting part
303… Supporting part
304… groove
305, 306, 307 ... Torsion coil spring
327… Compression spring
401 ... Primary transfer roller high pressure contact plate
401a ... end
401b ... end
401c ... hook part
402… Charging roller high voltage contact plate
402a ... end
402b ... end
402c ... Hook part
403 ... Cleaning charging roller high voltage contact plate
403a ... end
403b ... end
403c ... hook part

Claims (4)

An image forming unit detachably mountable from the image bearing member in a primary transfer region in the image forming apparatus main body which transfers secondarily transfer material a toner image primarily transferred to the intermediate transfer belt from the intermediate transfer belt at the secondary transfer portion,
An image carrier for carrying a toner image;
An intermediate transfer belt of endless toner image on said image bearing member is transferred,
A plurality of rotating members that stretch the intermediate transfer belt ;
A primary transfer member that forms a primary transfer site together with the image carrier via the intermediate transfer belt ,
One of the plurality of rotating members is a driving roller for rotating the intermediate transfer belt, and the primary transfer portion is formed downstream of the driving roller in the rotation direction of the intermediate transfer belt, In the image forming unit in which the image carrier and the intermediate transfer belt can be integrally attached to and detached from the image forming apparatus main body,
The intermediate transfer belt is stretched only by two rollers, a driven roller and a driven roller driven by the rotation of the intermediate transfer belt,
The drive roller contacts the outer surface of the intermediate transfer belt to collect the secondary transfer member that contacts the outer surface of the intermediate transfer belt to form the secondary transfer portion and the toner remaining on the intermediate transfer belt. A counter roller facing each of the cleaning members in contact with each other via the intermediate transfer belt, and grounded as a counter electrode for each of the secondary transfer member and the cleaning member;
When the image forming unit is mounted on the main body of the image forming apparatus, the drive roller is disposed below the driven roller . The image forming apparatus according to claim 1 , further comprising an image forming unit that is detachable from the main body of the image forming apparatus, and forms an image on a transfer material. 3. The toner remaining on the intermediate transfer belt of the image forming unit is collected by a cleaning unit via the image carrier by applying a charge opposite to that at the time of transfer by the cleaning member. Image forming apparatus. The image forming apparatus develops an electrostatic latent image formed on a rotating image carrier with an arbitrary color toner, and performs a primary transfer process on the intermediate transfer belt for the obtained toner image for each different color. Again, the after forming the overlapped color toner image on the intermediate transfer belt, according to claim 2 or claim 3, characterized in that to obtain a color image secondarily transferred collectively onto a transfer material image Forming equipment.

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