JP2002229413A - Image forming unit and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming unit realizing miniaturization and the reduction of cost by reducing the number of parts, and an image forming device using the image forming unit. SOLUTION: This image forming unit which can be attached to/detached from an image forming device main body is provided with an endless intermediate transfer belt 5a to which a toner image on a photoreceptor drum 1 is transferred, and a driving roller 40 and a driven roller 41 rotatably supporting the belt 5a. Then, the driving roller 40 becomes a common electrode for a secondary transfer roller 11 and an electrifying roller 5f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming unit used for a copying machine or a printer using an electrophotographic system, and an image forming apparatus for forming an image on a transfer material using the same.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an image is formed by transferring a toner image formed on a photosensitive drum as an image carrier to a transfer material. 2. Description of the Related Art There has been used a device having a configuration in which toner images of respective colors sequentially formed on a body drum are superimposedly transferred onto an intermediate transfer member, and the color images are collectively transferred onto a transfer material. In this case, in order to facilitate the handling of the deteriorated and consumable members of the photosensitive drum and the like, those which are unitized and detachable from the apparatus main body have been widely used.

A color image forming apparatus using such an intermediate transfer member is disclosed in JP-A-8-137181 and JP-A-10-3103.
As described in JP-A-01464 and JP-A-11-295998, the photoreceptor unit and the intermediate transfer unit have independent unit configurations, and when the unit life has been reached or when a jam (paper jam) is to be processed. It is configured to be removable.

Japanese Patent Application Laid-Open No. 8-137181 discloses a structure in which a movable frame on the front of the apparatus is rotated downward and opened to the front of the apparatus, and the photosensitive unit and the intermediate transfer unit are detachably mounted from above. In Japanese Patent Application Laid-Open No. Hei 10-301464, the photoreceptor unit and the intermediate transfer unit are detachably mounted on a movable body that can be pulled out horizontally to the front of the apparatus body. In these two conventional examples, the unit is attached and detached in a direction parallel to the transfer material transport direction.

On the other hand, in Japanese Patent Application Laid-Open No. H11-295998, the unit is slid in a direction perpendicular to the transfer material conveying direction to be detached.

In the above conventional example, the intermediate transfer member is an endless belt, which is suspended by three or more rollers, and the intermediate transfer belt applies a driving roller for driving the belt and tension to the belt. And a secondary transfer facing roller facing the secondary transfer means.

The primary transfer means facing the photosensitive drum with the photosensitive drum serving as an image carrier and the intermediate transfer belt interposed therebetween is viewed from the drive roller on the upstream side in the transport direction of the intermediate transfer belt (the so-called belt tension side). ) Is located.

Further, the diameter of the roller serving as the suspended tension member is large and small.

FIG. 11 is an explanatory view of a conventional color image forming apparatus using an intermediate transfer belt. In FIG.
The intermediate transfer unit 504 has the intermediate transfer belt 508 suspended and stretched by three rollers: a driving roller 502, a secondary transfer opposing roller 505, and a tension roller 506 for applying a predetermined tension to the intermediate transfer belt 508 by a spring (not shown). In addition, a primary transfer roller 507 is provided at a position facing the photosensitive drum 501.

The driving roller 502 rotates clockwise (clockwise) as shown in FIG. 11, and the intermediate transfer belt 508 also moves clockwise as shown by the arrow. Secondary transfer facing roller
The 505 and the tension roller 506 are configured to rotate following the intermediate transfer belt 508.

The photosensitive drum 501 of the photosensitive drum cartridge 503 has an intermediate transfer belt driving roller 5 as shown in FIG.
The primary transfer roller 507 is disposed at L1 between the second transfer roller 02 and the tension roller 506, and the primary transfer roller 507 is disposed opposite to the intermediate transfer belt 508.

L1 where the primary transfer portion exists is an upstream side in the intermediate transfer belt transport direction when viewed from the rotation direction of the intermediate transfer belt driving roller 502, that is, a so-called belt tension side.

This is an arrangement in consideration of the fact that the variation in the rotational movement speed of the intermediate transfer belt 508 is more stable on the tight side L1 of the belt than on the loose side L2 of the intermediate transfer belt 508.

That is, the process of developing the electrostatic latent image formed on the photosensitive drum 501 with toner of an arbitrary color and primary transferring the obtained toner image to the rotating intermediate transfer belt 508 is repeated for each different color. This is because, when forming a color superimposed toner image on the intermediate transfer belt 508, the conveyance speed of the intermediate transfer belt 508 must be stable in order to reduce the color shift for each color toner.

Further, the peripheral length Lb of the intermediate transfer belt 508 is configured to be substantially an integral multiple of the peripheral length Ld of the photosensitive drum 501, and also to be approximately an integral multiple of the peripheral length Lr of the intermediate transfer roller driving roller 502. The primary transfer of each color toner from a predetermined position on the intermediate transfer belt 508 is performed with a constant period between a change in the peripheral speed in one rotation cycle due to the shake of the photosensitive drum 501 and a change in the transport speed due to the shake of the drive roller 502 of the intermediate transfer belt 508. By starting, the phase of the color shift for each color toner on the intermediate transfer belt 508 is configured to overlap, and the secondary transfer roller 50
In step 9, the color image is transferred onto the transfer material at a time and a color image with little color shift can be obtained.

In FIG. 11, if the diameter D1 of the photosensitive drum 501 is 47 mm, the circumferential length Ld of the photosensitive drum is 47π mm, and the circumferential length Ld1 from the exposure position A of the photosensitive drum 501 to the primary transfer position B is Approximately 63 mm.

The circumference Lb of the intermediate transfer belt 508 is 47π × 2
≒ 295.3mm or 47π × 3 ≒ 442.96mm, but transfer material is A4
For a sheet of a size, the minimum length is a belt length of 360 mm, which is obtained by adding a paper length of 297 mm and a distance 63 mm at which the exposure position A of the photosensitive drum 501 rotates to the primary transfer position B.

Further, the length of the belt from the primary transfer position B of the intermediate transfer belt 508 to the secondary transfer position C in the belt transport direction must be at least 297 mm or more, which is the length of A4 size paper.

Considering the switching time of each color toner developing device, the pressing of the toner developing device to the photosensitive drum 501, and the time of separation, the intermediate transfer is performed when an appropriate interval (sheet interval) of the sheet paper is taken into consideration. The proper length Lb of the belt 508 is 442.96 mm.

The peripheral length Lr of the intermediate transfer belt driving roller 502 is 442.96 / 5 ≒ 88.593 mm, and the driving roller diameter D
2 is 88.893 / π ≒ 28.2 mm.

[0021]

The above-mentioned prior art has the following problems. That is, the portion 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 is considered in consideration of the transfer path of the transfer material, and further, while satisfying the respective dimensional relationships described above, Intermediate transfer belt
It is necessary to devise a shape for hanging the 508 compactly.

However, the intermediate transfer belt 508 faces the drive roller 502 and the secondary transfer roller 509, and forms a nip with the secondary transfer roller 509 to convey the transfer material to the secondary transfer opposing roller 505 and the intermediate transfer belt 508. In such a case, three or more rollers such as a tension roller 506 for applying a predetermined tension are provided. Then, the intermediate transfer belt 50
When a charging unit for charging the toner transferred to the belt 8 is brought into contact with the belt 508, a belt support roller must be provided at a position facing the charging unit.

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 must be complicated and high in accuracy. As a result, the intermediate transfer unit and the image This has been a factor of increasing the size of the forming apparatus body and increasing the cost.

The present invention solves the above problems,
It is an object of the present invention to provide an image forming unit capable of reducing the number of components to reduce the size and cost and an image forming apparatus using the same.

[0025]

A typical configuration according to the present invention for achieving the above object is to transfer a toner image on an image carrier in an image forming unit detachable from an image forming apparatus main body. An endless belt member, and a plurality of rotating members rotatably supporting the belt member, wherein one of the plurality of rotating members is configured to be a common electrode of a plurality of electrode members. .

In the above configuration, the belt member can be supported by the two rotating members by using one of the rotating members for suspending and extending the belt member as a common electrode of the plurality of electrode members. By reducing the number of component parts of the unit, it is possible to reduce the size of the entire apparatus main body, improve assemblability, and reduce costs.

[0027]

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.

[First Embodiment] FIG. 1 is an explanatory longitudinal sectional view showing a schematic configuration of a four-color full-color laser beam printer in an electrophotographic image forming apparatus A according to a first embodiment. It is the front.

<< Overall Configuration of Image Forming Apparatus >> Photosensitive drum 1 as an image carrier in synchronization with rotation of intermediate transfer belt 5a as an endless belt member as an intermediate transfer member
Is rotated in the direction of the arrow in FIG. 1 (counterclockwise), and the surface of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a charging device. A yellow electrostatic latent image is formed on the drum 1. Simultaneously with the formation of the electrostatic latent image, the developing device 4 is driven to arrange the yellow developing unit 4Y at the developing position, and the charging of the photosensitive drum 1 is performed so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. A voltage having the same polarity as the polarity and substantially the same potential is applied to cause the yellow toner to adhere to the electrostatic latent image for development. 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, so that a yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed as described above, the next developing device rotates and moves to the developing position facing the photosensitive drum 1, and the magenta and yellow toner images are moved in the same manner as in the case of yellow. Forming an electrostatic latent image for each color of cyan and black, and developing each color 4
M, 4C, and 4BK development and primary transfer are sequentially performed, and four color toner images are superimposed on the intermediate transfer belt 5a.

During this time, the secondary transfer roller 11 as a secondary transfer means is not in contact with the intermediate transfer belt 5a.
At this time, a charging roller 5f as a cleaning charging unit
Are not in contact with the intermediate transfer belt 5a.

After the formation of the four color toner images 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).
feed roller 7 as a conveying means in synchronization with the rotation of
b, the transfer material transported from the transfer material cassette 7a by the transport roller pair 7c and waiting at a predetermined position near the registration roller pair 7d is sent out to the nip portion between the intermediate transfer belt 5a and the secondary transfer roller 11.

Here, immediately before the registration roller pair 7d, a pre-registration sensor 14 which detects the leading end of the transfer material S, interrupts the rotational driving force of the registration roller pair 7d, and waits the transfer material S at a predetermined position. Is provided.

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 intermediate transfer belt 5a
The upper toner image is secondarily transferred to the surface of the transfer material S conveyed in a lump. At this time, the driving roller 40 facing the secondary transfer roller 11 with the intermediate transfer belt 5a interposed therebetween.
Functions as a counter electrode of the secondary transfer roller 11.

The transfer material S thus secondary-transferred in this manner is
Reaches the fixing device 8 via the conveyor belt unit 12, where a plurality of color toner images are fixed, and then the discharge roller pair 13 is fixed.
The sheet is conveyed along the discharge guide 15 and discharged to the discharge tray 10 above the color image forming apparatus A by the discharge roller pair 9 to complete the image formation.

On the other hand, after the secondary transfer, the cleaning charging roller 5f is pressed against the intermediate transfer belt 5a, and charges the residual toner remaining on the intermediate transfer belt with a charge opposite to that at the time of transfer (reverse the normal charge polarity of the toner). (Polar charge). That is, the collecting means applies the opposite-polarity charge to the residual toner as described above, and applies this charge to the photosensitive drum 1 by the primary transfer roller 5j as the primary transfer means.
And then is collected by the cleaning drum 6 for the photosensitive drum. 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.

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 at the same time. The toner image for the next transfer material formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 5a. Thereby, the throughput of image formation can be improved.

{Image Forming Unit} Next, the structure of the image forming unit integrated with the photosensitive drum and the intermediate transfer belt that is attached to and detached from the image forming apparatus will be described in detail.

FIG. 2 is an enlarged main longitudinal sectional view showing a schematic configuration of the image forming unit shown in FIG. 1, and is a sectional view seen from the left side as viewed from the front of the apparatus. FIG. 3 is a longitudinal sectional view of the image forming unit viewed from the right side as viewed from the front of the apparatus. FIG. 4 is a cross-sectional view of the waste toner conveying passage when FIG. 2 is viewed from above.

2 to 4, the image forming unit 5
Has a photoreceptor drum unit 20 disposed on the upper projection surface of the intermediate transfer belt unit 21, and a waste toner box 16 disposed on the lower projection surface of the intermediate transfer belt unit 21. In addition, a cleaning charging roller unit 23 for applying a reverse charge to the residual toner on the intermediate transfer belt 5a as compared with the time of transfer is provided on the belt driving roller 40 of the intermediate transfer belt unit 21, and is configured integrally.

(Photosensitive Drum Unit) In the photosensitive drum unit 20, as shown in FIGS. 2 and 3, the photosensitive drum 1 is rotatably held at both ends by a right bearing 206 and a left rotating support shaft 202. A predetermined rotational driving force is transmitted from the apparatus main body via the coupling 24 of the unit.

The charging roller 2 is pressed against the photosensitive drum 1 by a compression spring 26 with a predetermined force via bearings 25 at both ends, and is driven to rotate. At least one of the bearings 25 is formed of a conductive member, and has a compression spring 26.
By applying a predetermined charging bias voltage to the charging roller 2 through the bearing 25 from above, the surface of the photosensitive drum 1 is uniformly charged.

Further, as shown in FIG. 5, the end of the compression spring 26 extends downward from the left side of the photosensitive drum frame 29 to form a compression spring 327, which is attached to the boss of the photosensitive drum frame 29 at one end. Is press-fitted and fixed.

Further, a cleaning blade 6 is provided at a predetermined position on the photosensitive drum 1 to remove the residual toner on the intermediate transfer belt to which the above-described reverse charge has been applied.
It is configured to be collected above and scraped off together with the residual toner on the photosensitive drum 1. The scraped waste toner is prevented from falling 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. To the right (arrow C in FIG. 4).
Direction).

Thereafter, the waste toner is supplied to the right side of the photosensitive drum unit 20 by the screw 28 (as viewed from the front side of the apparatus).
, And slide down and accumulate 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 the operation of attaching and detaching the photosensitive drum unit to and from the image forming apparatus main body.

(Intermediate Transfer Belt Unit) Next, the structure of the intermediate transfer belt unit 21 will be described. The intermediate transfer belt 5a is suspended around a frame 45 including a handle 61 by a driving roller 40 and a driven roller 41 as two rotating members.

The driving roller 40 is connected to the intermediate transfer belt 5.
a for applying a rotational force to the frame 45, and is rotatably fixed to the frame 45. The drive roller 40 is formed of a metal pipe or the like, and a layer having a high frictional force such as a rubber layer having a predetermined conductivity is formed on a surface layer thereof, and functions as an electrode.

As shown in FIG. 2 to FIG.
Are rotatably held at both ends by a right bearing 205 and a left bearing 201, and a predetermined rotational driving force is transmitted from the apparatus main body via a coupling 42 (see FIG. 3) at the right end. The left bearing 201 is formed of a conductive member and is grounded to the main body of the image forming apparatus.

The bearings 43 at both ends of the driven roller are provided with compression springs 44, which are movably mounted in a direction for applying a predetermined tension to the intermediate transfer belt 5a.

A primary transfer roller 5j is provided at a position opposed to the photosensitive drum 1 with the intermediate transfer belt 5a interposed therebetween. The primary transfer roller 5j is pressed with a predetermined force by a compression spring 47 via bearings 46 at both ends, and is driven. It is designed to rotate.

At least one of the bearings 46 is formed of a conductive member. By applying a predetermined charging bias voltage to the primary transfer roller 5j, the toner on the surface of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a. Is done.

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 member frame 45, and its end 401a is connected to the compression spring 47 and the other end thereof. 401b is fixed to a lower left portion of the intermediate transfer body frame 45 by a hook portion 401c.

As shown in FIG. 2, a cleaning charging roller section 23 is provided at a position facing the intermediate transfer belt driving roller 40 to apply a reverse charge to the residual toner on the intermediate transfer belt at the time of transfer. Have been.

The cleaning charging roller 5f has bearings at both ends.
The compression spring 52 press-contacts with a predetermined force via 51, and is driven to rotate. At least one of the bearings 51 is formed 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, the intermediate transfer belt 5
A charge opposite to that at the time of transfer is imparted to the residual toner on the photosensitive drum 1, the toner is electrostatically attracted and collected on the drum surface by the photosensitive drum 1, and is accumulated in the waste toner box 16 as described above.

When charging by the charging roller 5f, the driving roller 40 facing the charging roller 5f via the intermediate transfer belt 5a functions as a counter electrode of the charging roller 5f. The driving roller 40 is connected to the secondary transfer roller 11 and the charging roller 5.
f, and serves as a common electrode common to both the secondary transfer roller 11 and the charging roller 5f, so that it is not necessary to provide opposing electrodes for each of the secondary transfer roller 11 and the charging roller 5f, so that the size of the intermediate transfer belt unit 21 can be reduced. .

As shown in FIG. 1, when the image forming unit 5 is loaded in the apparatus main body, the charging roller 5
f and the secondary transfer roller 11 are respectively disposed near the drive roller 40 serving as the counter electrode, and the charging roller 5f is located on the downstream side of the secondary transfer roller 11 in the rotation direction of the intermediate transfer belt 5a. It is arranged upstream of the transfer section 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 image forming throughput in the case of continuously forming images on a plurality of transfer materials Can be prevented from decreasing.

As shown in FIG. 4, the compression spring 52 is connected to an end 403a of a high-voltage contact plate 403 of the cleaning charging roller constituting the cleaning means, and the other end 403b.
Is fixed to a lower left portion of the intermediate transfer body frame 45 by a hook portion 403c.

Further, as shown in FIGS. 4 and 5, the charging roller 2 is placed inside the left cover 208 of the intermediate transfer member frame 45.
Is provided with a charging roller high voltage contact plate 402 for supplying a high voltage to the intermediate transfer body frame 4.
5, and extends downward from the left side of the photosensitive drum frame 29 and is connected to a compression spring 327. The other end 402b is hooked by a hook 402c.
It is fixed to the lower left of the 45. As a result, the electric power from the apparatus main body is applied to one end 402
b and the other end 402a of the contact plate 402 and the compression spring
Since 327 is electrically connected as electric contact means, it is supplied to the charging roller 2 via the compression spring 26 and the bearing 25.

As described above, the contact points for supplying the bias voltages from the image forming apparatus main body to (1) the charging roller 2, (2) the primary transfer roller 5j, and (3) the cleaning means are connected to the intermediate transfer belt unit 21. The lower 40 (outside the width of the image forming area)
2b, 401b, and 403b.

{Unit Configuration of Image Forming Unit} Next, the frame configuration of the image forming unit 5 will be described in detail. The frame configuration is roughly divided into two. First, as shown in FIGS. 3 and 4, the first unit is a photosensitive drum frame integrally configured with the waste toner box 16.
29, a photosensitive drum 1, a right bearing 206, a left rotating shaft 202,
Charging roller 2, cleaning blade 6, screw 2
8. A photosensitive drum unit 20 (a portion surrounded by a bold two-dot chain line in FIG. 4) composed of the drum shutter 19 as a main component. Further, as shown in FIG. 2, the second unit includes an intermediate transfer belt 5a on the intermediate transfer body frame 45.
The primary transfer roller 5j is disposed inside the intermediate transfer belt facing the photosensitive drum 1, and the cleaning charging roller 5f is also disposed on the drive roller 40. The belt unit 21.

As shown in FIGS. 2 and 3, the two units have projections 71 provided on the left and right ends of the photosensitive drum frame 29 in 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 body frame 45.

Here, the positioning hole 72 and the lock hole 74 provided in the intermediate transfer body frame 45 are larger by a predetermined amount than the projection 71 provided in the photosensitive drum frame 29 and the hook 73 of the hook. A hole is formed, and a predetermined amount of relative position movement between the photosensitive drum unit 20 and the intermediate transfer belt unit 21 is possible. Also,
The positioning hole 72 is provided with a tapered portion 72a (see FIG. 8) so that it can be easily attached and detached.

In the above configuration, as shown in FIG. 3, the hook claw 73 of the photosensitive drum unit 20 is pushed in the direction of arrow D to disengage it from the lock hole 74 of the intermediate transfer belt unit 21.
As shown in FIG. 7, by rotating the photosensitive drum unit 20 in the direction of arrow E, as shown in FIGS.
The photosensitive drum unit 20 and the intermediate transfer belt unit 21 can be divided.

When connecting the separated units 20 and 21, the projection 71 of the photosensitive drum unit 20 is reversed
Into the positioning hole 72 of the intermediate transfer belt unit 21,
By rotating the hook claw 73 into the lock hole 74 by rotating in the direction opposite to the arrow E in FIG. 7, the two units 20 and 21 are connected.

At this time, the bias voltage supply path to the charging roller 2 is connected to the end 402a of the charging roller high voltage contact plate 402 provided on the intermediate transfer belt unit 21 side and the photosensitive drum unit.
It is configured to be connected and separated by a compression spring 327 provided on the 20 side.

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, the life is reached. Only the unit can be replaced. Therefore, when the life of the photosensitive drum 1 and the life of the intermediate transfer belt 5a are different, the cost burden on the user is reduced.

{Attaching Means of Unit to Apparatus Main Body} Next, a description will be given, with reference to FIG. 10, of a structure 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.

When the upper lid 60 of the color image forming apparatus main body A is opened, the coupling 24 provided on the support portion 302 for supporting the photosensitive drum bearing and transmitting the rotational driving force to the photosensitive drum 1 (see FIG. 3). And a coupling 42 (see FIG. 3) provided on the support portion 303 for supporting the bearing portion of the intermediate transfer belt driving shaft and transmitting rotational driving force to the intermediate transfer belt driving roller. The respective couplings are slid in the axial direction and retracted (uncoupled state). It should be noted that a well-known configuration may be used for the retraction configuration itself of the coupling interlocking with the upper lid 60.

A guide rail 300 for the photosensitive drum and a guide rail 301 for the intermediate transfer member are provided on both sides of the apparatus main body with a step γ. The step γ is caused by the bearing 206 for the drum of the image forming unit and the rotating shaft 2 shown in FIG.
02 and a step γ between the bearings 201 and 205 of the intermediate transfer belt driving roller.

The photosensitive drum right bearing 206 and left rotating shaft 202 of the image forming unit 5 are provided on the photosensitive drum guide rail 300, the right bearing 205 and left bearing 201 of the intermediate transfer belt driving roller, and the left and right side covers. Projection 2
03 and 204 (see FIG. 4) are respectively placed on the guide rails 301 for the intermediate transfer member and inserted while sliding.

Finally, the photosensitive drum right bearing 206 and the left rotary support shaft 202 are supported by the support 3 supporting the photosensitive drum bearing.
02, the right side bearing 20 of the intermediate transfer belt drive roller
5 and the left bearing 201 fall into the support part 303 which supports the bearing part of the intermediate belt drive shaft, and 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. As shown in 10, each is pressed against the positioning of the apparatus body frame by the torsion coil springs 305, 306, 307 and fixed.

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, but both units are configured as an integral unit that cannot be separated. Is also good.

Further, in the image forming unit 5 of the above-described embodiment, an example has been described in which the intermediate transfer belt 5a is supported by two rollers, that is, a driving roller and a driven roller. However, the intermediate transfer belt 5a is supported by three or more rollers. It may be.

In the above-described embodiment, a color image forming apparatus for forming a color image by loading the image forming unit 5 is illustrated. However, the image forming unit according to the present invention is applicable to an image forming apparatus for forming a monochrome image. Can also be used.

[0075]

As described above, according to the present invention, the belt member is supported by the two rotating members by using one of the rotating members for suspending the belt member as a common electrode of the plurality of electrode members. This makes it possible to reduce the number of component parts of the unit, thereby reducing the size of the entire apparatus body, improving the assemblability, and reducing the cost.

[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 an explanatory left main longitudinal sectional view of an image forming unit integrated with a photosensitive drum and an intermediate transfer belt embodying the present invention.

FIG. 3 is a main vertical cross-sectional explanatory view of the image forming unit of FIG. 2 as viewed from the right side.

4 is an explanatory cross-sectional view of the image forming unit of FIG. 2 as viewed from above.

FIG. 5 is an explanatory sectional view showing a bias voltage supply path to a charging roller for charging a photosensitive drum.

FIG. 6 is an explanatory sectional view showing a bias voltage supply path to a primary transfer roller.

FIG. 7 is an explanatory diagram illustrating a state of a high-voltage contact portion when the photosensitive member unit and the intermediate transfer unit are divided.

FIG. 8 is an explanatory diagram of an intermediate transfer unit.

FIG. 9 is an explanatory diagram of a photoconductor unit.

FIG. 10 is an explanatory diagram illustrating a state where 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 the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor 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 Feed roller 7c Transport roller pair 7d Registration roller pair 8 Fixing unit 9 Discharge roller pair 10 Discharge tray 11 Secondary transfer roller 12 Transport 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: Photoconductor drum unit 21: Intermediate transfer belt unit 23: Cleaning charging roller unit 24: Coupling 25 … Bearing 26… Compression spring 27… Squeeze sheet 28… Screw 29… Photoconductor drum frame 40 ... drive roller 41 ... driven roller 42 ... coupling 43 ... bearing 44 ... compression spring 45 ... intermediate transfer body frame 46 ... bearing 47 ... compression spring 51 ... bearing 52 ... compression spring 60 ... top lid 61 ... handle 71 ... projection 72… Positioning hole 72a… Taper part 73… Claw 74… Lock hole 201… Left bearing 202… Left rotation support shaft 203,204… Protrusion 205… Right bearing 206… Right bearing 208… Left cover 300… Guide for photosensitive drum Rail 301… Guide rail for intermediate transfer member 302… Support part 303… Support part 304… Groove 305, 306, 307… Torsion coil spring 327… Compression spring 401… Primary transfer roller high-voltage contact plate 401a… End 401b… End 401c… Hook 402: Charge roller high voltage contact plate 402a: End 402b: End 402c: Hook 403: Cleaning charge roller high voltage contact plate 403a: End 403b: End 403c: Hook

Claims (8)

[Claims] An image forming unit detachable from a main body of an image forming apparatus, comprising: an endless belt member to which a toner image on an image carrier is transferred; a plurality of rotating members rotatably supporting the belt member; An image forming unit, wherein one of the plurality of rotating members is configured to be a common electrode of a plurality of electrode members. 2. The method according to claim 1, wherein the plurality of rotating members are a driving roller having a fixed position for transmitting a rotating force to the belt member, and a driven roller movable to apply tension to the belt member. 2. The image forming unit according to claim 1, wherein the driving roller serves as a common electrode. 3. The image forming apparatus according to claim 1, further comprising: a primary transfer unit that primarily transfers a toner image formed on the image carrier to the belt member, at a position facing the image carrier with the belt member interposed therebetween. 2. The image forming unit according to 2. 4. One of the plurality of electrode members is a secondary transfer unit for performing a secondary transfer of an image transferred to the belt member to a transfer material, and another one of the plurality of electrode members remains on the belt member. Charging means for applying a reverse charge to the toner, wherein the charging means is disposed near the driving roller and downstream of the secondary transfer means in the rotation direction of the belt member. The image forming unit according to claim 2. 5. The image forming unit has a first unit having the image carrier and a second unit having the belt member, and the first unit and the second unit are separable. The image forming unit according to claim 1. 6. The image forming unit according to claim 1, further comprising an image forming unit detachable from an image forming apparatus main body, and forming an image on a transfer material. An image forming apparatus. 7. The image forming apparatus according to claim 6, wherein the toner remaining on the belt member of the image forming unit is collected by a cleaning unit via the image carrier. 8. A step of developing the electrostatic latent image formed on the rotating image carrier with an arbitrary color toner, and primary transferring the obtained toner image to the rotating belt member. 8. A color image is obtained by forming a superimposed toner image of a color on the belt member on the belt member and then performing secondary transfer collectively on a transfer material to obtain a color image. Image forming apparatus.