JPH1039651A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image of high quality and improve operation at jam processing and maintenance by securing fitting accuracy of a transfer unit to an image forming part and providing constant shifting speed of a recording material holding sheet and minimizing and lightening the transfer unit. SOLUTION: A transfer unit 30 to which driving force from a drive motor 17 mounted at body side of the image forming device is supplied is turnable to the body side of the image forming device and detachable from the body of the image forming device. In this case, the transfer unit 30 turns for contacting and separating to the image forming device body taking a drive roller shaft 32a as turning center. A motor shaft 17a is coupled with the drive motor 17 in the drive roller shaft 32a and whereby, rotational drive force from the drive motor 17 transmitted and turned, for example, a transfer carry belt 31 for holding and carrying a transfer paper is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic recording system and an electrostatic recording system, and more particularly to an image forming apparatus having a transport belt for transporting a recording material.

[0002]

2. Description of the Related Art An image forming apparatus employing an electrophotographic recording system uses a drum-type electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") as an image carrier using light, magnetism, electric charge and the like.
An image forming unit for forming a latent image thereon, developing the latent image and visualizing the latent image as a toner image, and a recording material conveying unit for conveying a transfer sheet as a recording material to a transfer position (transfer site) of the image forming unit (Hereinafter, referred to as a “transfer unit”), and a fixing unit that fixes the toner image transferred to the transfer sheet at the transfer portion.

Some transfer units use a belt-shaped transfer member (transfer sheet transfer belt) for transferring the transfer sheet when the toner images are sequentially transferred from the image forming units of the respective colors to the transfer sheet. The transfer paper transport belt is wound around an endless ring around one drive roller and at least one driven roller, adsorbs the transfer paper by electrostatic attraction, and sequentially moves each color by the orbital movement of the transfer paper transport belt. Is transferred to the transfer portion of the image forming section.

In addition, between the driving roller and the driven roller, a transfer paper conveying belt is devised so as to be stretched with a constant force, and the driving roller is arranged downstream in the conveying direction, so that the surface of the image forming section is exposed. The transfer paper transport belt is designed so that the tension side of the transfer paper transport belt does not sag, and the transfer paper transport belt is configured to move at a constant speed from the image forming section on the most upstream side to the image forming section on the most downstream side.

The driving roller is driven by a transfer driving motor provided in the transfer unit via a timing belt.

The toner images of the respective colors formed on the respective photosensitive drums are sequentially superimposed and transferred onto the transfer paper which is attracted onto the conveyor belt and conveyed to the transfer portions of the respective image forming sections.

Further, the transfer unit can be pulled out of the image forming apparatus main body at the time of jam clearance or maintenance, so that when the transfer unit is pulled out, the transfer paper transport belt is separated from the image forming unit, for example, The transfer paper transport belt is configured to be able to swing around the drive roller.

A fixing unit is disposed downstream of the transfer paper transfer belt in the transfer paper transfer direction and close to the transfer unit. The fixing unit mixes and fixes the toner images of each color transferred to the transfer paper by heat and pressure to form a full-color print image.

[0009]

However, the conventional image forming apparatus has the following problems. (1) In the above-described image forming apparatus, the transfer unit is configured to be swingable about the driving roller and to be able to be pulled out. Therefore, the accuracy of the clearance of the transfer unit with respect to the image forming unit is equal to the transfer with respect to the image forming unit. Since the unit positioning is inferior to the case where the transfer unit is fixed, a good transfer state cannot be obtained, and an image defect occurs. (2) The drive roller in the transfer unit is driven via a timing belt by a transfer drive motor provided in the transfer unit, and therefore, a pulley attached to a shaft of the drive motor around which the timing belt is wound, If the pulley attached to the drive roller shaft is eccentric,
The speed of the transfer paper conveyance belt varies with the rotation cycle of the timing belt. For this reason, the transfer paper conveyance belt cannot be conveyed at a constant speed, and image defects such as expansion and contraction of images and color shift occur. (3) The transfer unit is pulled out of the image forming apparatus main body or removed from the image forming apparatus main body during jam processing and maintenance, but in the image forming apparatus, a driving system including a driving motor and a driving roller is used for transfer. Because it is inside the unit, the transfer unit becomes large,
Since the weight is increased, the operability at the time of jam clearance and maintenance of the transfer unit may be deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has assured mounting accuracy of a rotary unit to an image forming unit, and has a constant moving speed of a recording material holding sheet. By reducing the size and weight of the rotating unit, high quality images are obtained,
It is another object of the present invention to provide an image forming apparatus having improved operability during jam clearance and maintenance.

[0011]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a rotating unit capable of moving toward and away from an image forming unit; The image forming apparatus is provided so as to be detachable from the main body, and a driving source for rotating the rotary unit is provided on the image forming apparatus main body side.

According to the second aspect of the present invention, the rotating unit is provided so as to be able to contact and separate from the image forming unit and to be detachable from the image forming apparatus main body. A drive source provided on the main body side for rotating the rotary unit, a first drive force transmitting unit for transmitting a drive force from the drive source to the rotary unit, and a first drive power transmission unit provided on the unit side; A second driving force transmitting unit that detachably engages with the driving force transmitting unit to rotate the unit and positions the rotary unit.

According to a third aspect of the present invention, the rotating unit is slidable in a state of being rotated about the second driving force transmitting portion and separated from the image forming apparatus main body.

According to a fourth aspect of the present invention, the first driving force transmitting section has a driving shaft for supplying a driving force from the driving source, and a main body positioning section for fitting the driving shaft. The second driving force transmitting unit to which the driving force is supplied from the first driving force transmitting unit includes a rotating shaft coupled to the driving shaft, and a unit positioning unit that fits the rotating shaft. Have.

According to the invention described in claim 5, the drive shaft is a motor shaft.

According to the invention described in claim 6, the rotating shaft is a drive roller shaft.

According to the seventh aspect of the present invention, the drive shaft and the rotary shaft are detachably connected so that the rotational drive force is transmitted from the main body to the unit on the same shaft. .

According to the present invention, the rotating unit is a transfer unit.

According to a ninth aspect of the present invention, the transfer unit includes a recording material holding sheet for holding and conveying a recording material so as to transfer a toner image at a transfer portion facing the image carrier, and the recording material holding sheet. The image forming apparatus includes a driving roller that drives the sheet while supporting the sheet, and at least one driven roller that winds the recording material holding sheet together with the driving roller.

According to the present invention, the rotary unit provided in the main body of the image forming apparatus and supplied with the driving force from the driving source can contact and separate from the image forming section. And is detachably provided from the image forming apparatus main body. In this case, the rotation unit is provided with a second
About the driving force transmission unit as a rotation center. Further, the second driving force transmission unit includes a first driving force transmitting unit.
The driving force transmitted from the driving source is transmitted and rotated by the driving force transmitting section, and the recording material holding sheet that holds and conveys the recording material is driven, for example.

Further, the rotating unit is slid with respect to the image forming apparatus main body in a state where the rotating unit is separated from the image forming section.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a schematic structural view showing an image forming apparatus according to a first embodiment of the present invention. In the present embodiment, a color image forming apparatus having an electrophotographic image forming unit will be described as an example.

The image forming apparatus according to the present embodiment includes a document reading section 1R and an image output section 1P. The image output unit 1P is roughly divided into four stations a, b,
The image forming unit 10 having the same configuration in which c and d are arranged in parallel, a sheet feeding unit 20, and a transfer unit (rotating unit) 30
, A fixing unit 40, and a control unit (not shown).

Further, the image forming section 10 has the following configuration.

On the outer peripheral surface of the photosensitive drum 11a, 11b, 11c, 11d which is driven to rotate in the direction of the arrow shown in the figure, a primary charger 12a which applies a charge of a uniform charge amount to the surface of the photosensitive drum 11 along the rotation direction. , 12b, 12c, 12
d and a light beam such as a laser beam modulated in accordance with a recording image signal is applied to the photosensitive drums 11a, 11b, 11c, 1
Exposure means 13 for exposing on 1d to form an electrostatic latent image
a, 13b, 13c, and 13d, and developers of four colors of yellow, cyan, magenta, and black (hereinafter, referred to as “toners”), and the photosensitive drums 11a, 11b, 11c,
Developing devices 14a and 14 for visualizing the electrostatic latent image of 11d
b, 14c, 14d and transcription sites Ta, Tb, Tc, T
and cleaning devices 15a and 15 that are disposed downstream of the transfer drum 16 and remove toner remaining on the photosensitive drums 11a, 11b, 11c, and 11d without being transferred to the transfer paper 16.
b, 15c and 15d are sequentially arranged.

The paper feeding unit 20 includes a cassette 21 for storing the transfer paper 16, a pickup roller 22 for sending out the topmost transfer paper 16 one by one from the cassette 21, and a transfer paper sent from the pickup roller 22. Paper feed rollers 23a and 23b for transporting the paper 16, a paper feed guide 24, registration rollers 25a and 25b for sending the transfer paper 16 to the transfer unit 30 in accordance with the image forming timing of the image forming unit 10, and transfer described later. A suction guide 26 for guiding the transfer paper 16 to the unit 30 is provided.

The transfer unit 30 includes a driving roller 32,
A driven roller 33, a tension roller 34, and a transfer paper transport belt 31 as a recording material holding sheet wound between the rollers 32, 33, 34 are provided. A transfer plane is formed on the tight side. The transfer paper transport belt 31 is formed of a material such as polyethylene terephthalate (PET) or polyvinylidene fluoride (PVdF).
Further, the transfer paper transport belt 31 includes the photosensitive drums 11a, 1a.
They are spaced apart by about 1 mm from 1b, 11c and 11d.

At a position of the transfer paper transport belt 31 where the transfer paper 16 sent from the registration rollers 25a and 25b enters, a suction charger 27 is disposed, and each photosensitive member downstream of the suction charger 27 is provided. Drums 11a, 11b, 1
The transfer portions Ta, Tb, Tc, and Td where the transfer paper transport belt 31 faces the transfer paper transport belt 3
The transfer charging blades 35a, 35b, 35
c and 35d are arranged.

The transfer charging blades 35a, 35b,
35c and 35d are photosensitive drums 1 by a mechanism not shown.
Pressing and separating can be performed on 1a, 11b, 11c, and 11d, and at the time of pressing, the transfer paper transport belt 31 is lifted and pressed against the photosensitive drums 11a, 11b, 11c, and 11d with an appropriate pressure. Is configured to perform better image transfer.

On the downstream side of the transfer paper transport belt 31 in the moving direction and slightly upstream of the drive roller 32, a charging / discharging charger 36 for separating and removing the transfer paper 16 is disposed. On the side, there are provided a static eliminator 37 for giving a uniform charge to the surface of the transfer paper transport belt 31, a brush roller 38 for cleaning the transfer paper holding surface of the transfer paper transport belt 31, and the like.

The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, and a pressing roller 41b pressed against the fixing roller 41a (the pressing roller 41b may also have a heat source). ), An insertion guide 43 for guiding the transfer paper 16 to the nip portion of the rollers 41a and 41b, and an inner discharge roller 44 for discharging the transfer paper 16 discharged from the rollers 41a and 41b to the outside of the apparatus main body 2. And an outer discharge roller 45. In the present embodiment, the distance between the fixing roller 41a and the driving roller 32 is set to about 100 mm or less.

The control unit includes a control board 50 and a motor drive board (not shown) for controlling the operation of the mechanism in each unit.

Next, description will be made according to the operation of the image forming apparatus.

When an image forming operation start signal is issued, first, the uppermost transfer paper 16 is fed one by one from the cassette 21 by the pickup roller 22. Then, the paper is guided to the paper feed guide 24 by the paper feed rollers 23a and 23b, and is guided between the paper feed guides 24 so that the registration rollers 2 are formed.
It is transported to 5a and 25b. At this time, the registration rollers 25a and 25b are stopped, and the leading end of the transfer paper 16 abuts against the registration rollers 25a and 25b to stop the conveyance. Then, the registration rollers 25a, 25 are synchronized with the timing at which the image forming section 10 starts image formation.
5b starts rotation. That is, the rotation start timing is set such that the toner image on the photosensitive drums 11a, 11b, 11c, and 11d coincides with the leading end of the image forming area of the transfer paper 16.

When a coulomb force is generated on the transfer paper transport belt 31 by the action of the attraction charger 27 and the transfer paper 16 enters the transfer paper transport belt 31, the transfer paper 16 is electrostatically attracted.

The transfer paper conveyor belt 31 holds the transfer paper 16 by suction while holding the photosensitive drums 11a, 11b, 11c, 1
1d, and circulates in synchronization with the rotation of the first transfer portion Ta.
The transfer paper 16 is transported up to that point. At the first transfer portion Ta, a high voltage is applied to the transfer charging blade 35a together with the start of the sequence in accordance with the passage timing of the transfer paper 16, and the yellow toner image formed on the photosensitive drum 11a is transferred to the transfer paper 16 Will be transferred to the surface of

Thereafter, the transfer paper 16 is further conveyed toward the second transfer portion Tb. This second transcription site Tb
Then, the cyan image is formed on the photosensitive drum 11b with a delay corresponding to the time required for the transfer paper 16 to be transported between the stations, and the second toner image is transferred with the registration on the previous image. Will be done.

Thereafter, the same steps are repeated to form magenta and black images on the photosensitive drums 11c and 11d.
6 and the toner images of four colors are multiplex-transferred.

When the multiple transfer of the toner images of the four colors to the transfer paper 16 is completed in this way, the attraction force of the transfer paper 16 to the transfer paper transport belt 31 is reduced by the action of the separating / charging charger 36, and thereafter, Then, the transfer paper 16 is separated from the transfer paper transport belt 31 by the curvature of the drive roller 32.

The transfer paper 16 separated from the transfer paper transport belt 31 is accurately guided to the nip portion of the fixing device 40 by the insertion guide 43. Then, the fixing roller 41
a) The unfixed toner image on the transfer paper 16 is fixed by the heat of the pressure roller 41b and the nip pressure. Thereafter, the transfer paper 16 is conveyed by the inner discharge roller 44 and the outer discharge roller 45, and is discharged outside the apparatus.

When the image forming step is completed, the transfer charging blades 35a, 35b, 35c, 35d release the pressure in order to protect the photosensitive drums 11a, 11b, 11c, 11d, and the transfer paper transport belt 31 is exposed to light. Drum 11
The sequence ends in a state in which the sequence is separated from a, 11b, 11c, and 11d. Transfer charging blades 35a, 35b,
35c and 35d can be separated by a mechanism (not shown). When pressurizing, the transfer paper transport belt 31 is lifted and pressed against the photosensitive drums 11a, 11b, 11c and 11d with an appropriate pressure. Image transfer can be performed.

Next, the characteristic portions of this embodiment will be described below.

The transfer unit 30 is generally provided with the transfer unit 3 in consideration of the operability at the time of jam clearance and maintenance.
0 can be pulled out from the image forming apparatus main body 2.

However, since the transfer paper transport belt 31 is in contact with the photosensitive drums 11a, 11b, 11c, 11d during image formation, the transfer paper transport belt 31 is temporarily pulled out of the photosensitive drums 11a, 11b, 11c when being pulled out. , 11d
It is necessary to have a configuration that allows an operation of separating from the user and then pulling out.

FIG. 2 is a schematic front sectional view showing a state in which the transfer unit according to the present embodiment is in contact with the photosensitive drum, and FIG. 3 is a schematic front sectional view showing a state in which the transfer unit is separated from the photosensitive drum. FIG. 4 is a schematic top sectional view showing a state where the transfer unit is mounted in the image forming apparatus main body, and FIG. 5 is a schematic sectional view showing a state where the transfer unit is pulled out to the near side. .

First, a mechanism for moving the transfer unit 30 into and out of contact with the photosensitive drums 11a, 11b, 11c and 11d will be described with reference to FIGS. Transfer unit 30
Are the driving roller 32 and the driven roller 3 on the rotation tip side.
3 and the tension roller 34, the photosensitive drum 11a,
Transfer blades 35a, 35b, 35c for transferring the toner images formed on 11b, 11c, 11d to transfer paper
35d, a frame 39 for supporting these rollers 32, 33, 34 and transfer blades 35a, 35b, 35c, 35d, and a transfer paper transport belt 31 wound around the rollers 32, 33, 34 to be stretched. You.

The transfer unit 30 is provided with a pressing means 54 rotatably provided below the tension roller 34.
And a pressure swing cam 55 for rotating the pressure means 54. That is, when one end of the pressing unit 54 comes into contact with or separates from the frame 39, the transfer unit 30 rotates about the drive roller 32 as a rotation center. The pressurizing means 54 is in constant contact with a pressurizing rocking cam 55 that is automatically or manually rotated by a drive source or a handle (not shown) at the other end in order to bring the pressurizing means 54 into and out of contact with the frame 39. When the cam surface of the pressure swing cam 55 that is the most distant from the eccentric shaft contacts the other end of the pressure means 54, the frame 3
9, the transfer unit 30 is moved by its own weight to cause the transfer unit 30 to contact the photosensitive drums 11a, 11b, 1 with the cam surface closest to the eccentric shaft of the pressure swing cam 55 contacting the other end of the pressure means 54.
It is configured to be separated from 1c and 11d. The frame 39 includes the photosensitive drums 11a, 11b, 1
Projection 39a abutting on abutting portion 110 of 1c, 11d
Are formed to project upward, and a projecting portion 39b is formed to lock the rotating front end side of the frame 39 to the guide portion 52a of the unit support 52.

As shown in FIGS. 2 and 3, the transfer unit 30 has the drive roller 32 as a rotation center and the tension roller 34 as a rotation tip, as shown in FIGS.
By rotating the pressure swing cam 55, the pressing means 5
One end of 4 is brought into contact with the frame 39, or one end of the pressurizing means 54 is separated from the frame 39.
Then, one end of the pressing means 54 is brought into contact with the frame 39 so that the projection 39a of the transfer unit 30 is brought into contact with the abutting portion 11 on the photosensitive drum 11a, 11b, 11c, 11d side.
Contact 0. Further, by separating one end of the pressing means 54 from the frame 39, the transfer unit 30 is separated from the abutting portion 110 by its own weight, and the projection 39 b of the frame 39 is locked on the guide portion 52 a of the unit support 52. .

Next, a mechanism for pulling out the transfer unit 30 from the photosensitive drums 11a, 11b, 11c and 11d to the front side of the image forming apparatus main body with the transfer unit 30 separated from the photosensitive drums 11a, 11b, 11c and 11d will be described with reference to FIGS.

The drive roller 32 is rotatably supported via bearings 39e on cylindrical bearing holders 39c and 39d having both ends of a drive roller shaft 32a (rotating shaft) serving as a rotation center fixed to a frame 39. ing. That is, the bearing 39e is provided such that the centers of the bearing holders 39c and 39d and the center of the drive roller shaft 32a are the same.

The outer peripheral portion of the bearing holder (unit positioning portion) 39c on the back side of the main body of the image forming apparatus is fitted with a support hole 51b formed in the back side plate 51a of the rail frame 51 and a drive motor holder (main body positioning portion). Part 18 is fitted to the inner peripheral part 18a. This drive motor holder 1
Reference numeral 8 denotes a drive motor holder 18 fitted to the rear plate 2a of the image forming apparatus main body, and a bearing holder 39c fitted to the inner peripheral portion 18a of the drive motor holder 18. Thus, a positioning means is formed, and the rear side of the transfer unit 30 is positioned with respect to the image forming apparatus main body.

A boss hole 18c is formed in the convex portion 18b of the drive motor holder 18 that penetrates the rear side plate 2a, and the boss portion 17b of the drive motor 17 as a drive source is fitted into the boss hole 18c. A drive motor 17 is fixed to a drive motor holder 18.

The driving motor holder 18 and the motor shaft 17a into which the driving motor holder 18 is inserted form a first driving force transmitting portion, and a bearing holder 39c and a driving device into which the bearing holder 39c is inserted. Roller shaft 32
and a form a second driving force transmitting portion.

One end of the drive roller shaft 32a is detachably coupled to a motor shaft 17a which is a drive shaft of the drive motor 17, and the rotation of the drive motor 17 is transmitted. That is, the motor shaft 17a and the drive roller shaft 32a are connected so that the unevenness is engaged. The drive roller shaft 32a and the motor shaft 17a are coaxially arranged by these configurations.

On the other hand, the outer peripheral portion of the bearing holder 39d on the front side of the image forming apparatus main body is connected to the front side plate 5 of the rail frame 51.
A support hole 51c formed in 1f is fitted. And
By positioning the positioning pins 51d projecting from the front side plate 51f into the fitting holes 2c of the front side plate 2b of the image forming apparatus main body, the front side of the transfer unit 30 is positioned in the image forming apparatus main body.

The driving-side slide rail 56 includes a movable rail 56a and a fixed rail 56b fixed to the main body frame 58, and the guide portion 51e of the rail frame 51 engages with the projection 56c of the movable rail 56a. I agree. The driven side slide rail 57 is mounted on the unit support 5.
2 to which the movable rail 57a is fixed and the body frame 5
8 with a fixed rail 57b fixed to
The transfer unit 30 is slidably supported by the driving slide rail 56 and the driven slide rail 56. Further, the transfer unit 30 is provided on the frame 39.
A handle 39f for pulling out along the slide rails 56 and 57 is provided.

The transfer unit 30 is pulled out by gripping the handle 39f of the frame 39. A slide rail 56 on the drive roller side is attached to a rail frame 51 integrally supported by the frame 39, and the driven unit is driven. With the roller-side frame 39 engaged with the unit support 52, the movable rails 56a, 57a are fixed to the fixed rails 56b, 5b.
7b, the fixing rail 56b on the driving roller side of the transfer unit 30 and the fixing rail 57b on the driven roller side of the transfer unit 30 are separated as shown in the present embodiment. The operations can be synchronized, and the transfer unit 30 can be pulled out substantially in parallel.

With these configurations, even if the transfer unit 30 is separated from the image forming apparatus main body and then pulled out, accurate positioning of the transfer unit 30 with respect to the image forming apparatus main body can be achieved, and an image defect due to a transfer failure can be prevented. .

Further, since the driving roller 32 and the driving motor 17 are coupled on the same axis and are directly driven without using a timing belt or a gear,
The belt circling speed of the transfer / conveyance belt 31 becomes constant, and expansion and contraction and color shift of an image are suppressed.

The drive motor 17 of the transfer unit 30
Can be arranged in the main body of the image forming apparatus.
The operability at the time of jam clearance and maintenance is improved by the weight reduction and size reduction of zero.

The following is a description of effects specific to the present embodiment.

In this embodiment, the shaft 32a of the drive roller 32
Correspond to the positioning with respect to the image forming apparatus main body, but the bearing holder 39 fixed to the frame 39 so that the coaxiality with the shaft 32a of the drive roller 32 is guaranteed.
Since the positioning is carried out via c and 39d, the weight of the transfer unit 30 is not applied to the drive roller shaft 32a, and it is possible to prevent the rotation accuracy from being deteriorated due to the bending of the shaft 32a.

Further, since the slide rails 56 and 57 for supporting the drawer of the transfer unit 30 are separated into the drive roller side and the driven roller side, a space is formed below the transfer unit 30. When a double-sided tray or the like is arranged at the lower portion, jam clearance of the double-sided tray can be performed in this space, and the height direction of the image forming apparatus main body can be compressed, which contributes to downsizing of the apparatus.

[0064]

As described above, according to the present invention,
The rotation unit is configured such that a driving force from a driving source provided on the image forming apparatus main body side is directly transmitted by a second driving force transmission unit via a first driving force transmission unit,
Since the second driving force transmission unit is provided so as to be able to contact and separate from the image forming unit with the rotation center as the center of rotation, positioning of the rotation unit with respect to the image forming main body can be achieved with high accuracy. An image defect due to transfer failure can be prevented, and the expansion and contraction and color shift of the image due to the speed fluctuation of the recording material holding sheet can be suppressed.

Further, since no drive source is disposed in the unit, the unit can be reduced in size and weight, and operability during jam clearance and maintenance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a full-color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a front sectional view showing a state in which the transfer unit according to the first embodiment of the present invention is in contact with a photosensitive drum.

FIG. 3 is a schematic front sectional view showing a state in which the transfer unit is separated from a photosensitive drum.

FIG. 4 is a schematic top sectional view showing a state in which the transfer unit is mounted in an image forming apparatus main body.

FIG. 5 is a schematic top sectional view showing a state in which the transfer unit is pulled out to the near side.

[Explanation of symbols]

 2 Image forming apparatus main body 11a Image carrier (photosensitive drum) 11b Image carrier (photosensitive drum) 11c Image carrier (photosensitive drum) 11d Image carrier (photosensitive drum) 17 Drive source (drive motor) 17a Drive shaft (motor shaft) 18) Body positioning section (drive motor holder) 30 unit (transfer unit) 31 recording material holding sheet (transfer conveyance belt) 32 drive roller 33 driven roller 32a rotating shaft (drive roller shaft) 39c unit positioning section (bearing holder)

Claims (9)

[Claims] 1. An image forming apparatus in which a rotation unit is provided so as to be able to contact and separate from an image forming unit and to be detachable from an image forming apparatus main body. An image forming apparatus provided on a forming apparatus main body side. 2. An image forming apparatus, wherein a rotating unit is provided so as to be able to approach and separate from an image forming unit and to be detachable from an image forming apparatus main body. A driving source for rotating the unit, a first driving force transmitting unit for transmitting a driving force from the driving source to the rotating unit, and a removably provided on the unit side and detachable from the first driving force transmitting unit. And a second driving force transmitting unit that engages to rotate the unit and position the rotating unit. 3. The image forming apparatus according to claim 1, wherein the rotation unit is slidable in a state where the rotation unit rotates about the second driving force transmission unit and is separated from the image forming apparatus main body. Alternatively, the image forming apparatus according to claim 2. 4. The first driving force transmitting unit includes a driving shaft that supplies driving force from the driving source, and a main body positioning unit that fits the driving shaft. The second driving force transmission unit to which the driving force is supplied from the transmission unit includes: a rotation shaft coupled to the drive shaft; and a unit positioning unit that fits the rotation shaft. The image forming apparatus according to claim 1 or 2, wherein 5. The image forming apparatus according to claim 4, wherein the drive shaft is a motor shaft. 6. The image forming apparatus according to claim 4, wherein the rotating shaft is a drive roller shaft. 7. The drive shaft and the rotary shaft are detachably coupled so that transmission of rotational drive force from the main body side to the unit side is performed on the same axis. 5. The image forming apparatus according to 4. 8. The image forming apparatus according to claim 1, wherein the rotation unit is a transfer unit. 9. A recording material holding sheet that holds and conveys a recording material so as to transfer a toner image at a transfer site facing an image carrier, and a driving device that drives while supporting the recording material holding sheet. The image forming apparatus according to claim 8, further comprising: a roller; and at least one driven roller that winds the recording material holding sheet together with the driving roller.