JPH10171304A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately align the toner images of respective colors in a system where a color image is formed by successively moving plural photoreceptors to one image forming position. SOLUTION: Plural image forming units 3 including the photoreceptor 30 of each color are attached around the shaft of a rotating carriage 2, and a coupling member 61 on a driving side is engaged with a coupling member 42 provided at one end side of the photoreceptor 30 in the unit 3 moved to the image forming position, so that driving force is transmitted to the photoreceptor 30. One end side of the shaft of the photoreceptor is supported in an aligned state by an output shaft 70 rotating the member 61. The toner image formed on the photoreceptor 30 is successively superposed chromatically and transferred to a transfer belt rotating at constant speed, and the color image formed on the transfer belt is transferred to recording paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color printer,
The present invention relates to a color image forming apparatus used for a color copying machine, a color facsimile, and the like, and more particularly, to a color image forming apparatus that forms a color image by superposing multicolor toner images by an electrophotographic method.

[0002]

2. Description of the Related Art The configuration of a conventional color image forming apparatus will be described by taking a color printer described in Japanese Patent Application Laid-Open No. 7-36246 as an example. FIG. 17 shows the internal structure of the conventional printer viewed from the side. This apparatus includes an intermediate transfer belt unit 201 including a transfer belt 202, a first transfer roller 203, a second transfer roller 204, a cleaner roller 205, a waste toner reservoir 206, and the like.
The color images are superimposed on the transfer belt 202.

At the center of the printer, image forming units 207Bk, 207Y, 207M and 207C having four fan-shaped cross sections for black, cyan, magenta and yellow are arranged in an annular shape as shown in FIG. A group 208 is formed. Image forming unit 207 for each color
When Bk, 207Y, 207M, and 207C are correctly mounted in the printer, the mechanical drive system and the electric circuit system on the image forming unit side and the printer side are connected via a mutual coupling member, and both are mechanically and electrically connected. Integrated.

An image forming unit 207 arranged in an annular shape
Bk, 207Y, 207M and 207C are cylindrical shafts 2
It is supported by a rotatable support centered at 09 and is rotationally driven by a drive motor as a whole. At the time of image formation, each image forming unit is sequentially rotated by the first transfer roller 2 on which the above-described intermediate transfer belt 202 is stretched.
It moves to the image forming position 210 opposite to the image forming position 03. The image forming position 210 is also an exposure position by the laser light 211.

[0005] Reference numeral 212 denotes a laser exposure device disposed at a lower portion in the printer. The laser signal light 211 is transmitted through the optical path window 2 formed between the image forming units 207M and 207C.
13, through a window opened in a cylindrical shaft 209, a mirror 2 located in the shaft 209 and fixed to the apparatus main body.
14 is incident. The laser signal light 211 reflected by the mirror 214 is applied to the image forming unit 20 at the image forming position 210.
The left side surface of the photosensitive drum 218 enters the image forming unit 207Bk from the exposure window 215 of 7Bk, passes through a space for an optical path between a developing unit 216 and a cleaner 217 disposed vertically in the image forming unit. Incident on the exposed portion. The photosensitive drum 218 is exposed by scanning the incident laser signal light in the generatrix direction of the photosensitive drum 218.

[0006] The toner image formed on the photosensitive drum 218 is transferred to the transfer belt 202, and then the image forming unit group 208 is rotated by 90 °, and the yellow image forming unit 20 is rotated.
7Y moves to the image forming position 210. Then, the same operation as the above-described formation of the black toner image is performed, and a yellow toner image is formed so as to overlap the black toner image already formed on the intermediate transfer belt 202. The same operation is further performed by using magenta and cyan image forming units to form a full-color image on the intermediate transfer belt 202, then transfer the color image to paper by the third transfer roller 219, and fix by the fixing device 220. .

In such a color printer, a mechanism for transmitting a rotational driving force to the photosensitive drum by connecting a drive mechanism of the printer body to the photosensitive drum of the image forming unit at the image forming position is shown in FIG. In FIG.
The photosensitive drum 2 of the image forming unit moved to the image forming position
The gear 18 is supported in a state where the rotation shaft 235 is positioned by a bearing (not shown), and a gear 232 fixed to one end of the rotation shaft 235 is engaged with a gear 241 fixed to the output shaft 245 on the main body side. Thus, the driving force of the main body is transmitted to the photosensitive drum 218.

[0008]

In order to record a high-precision full-color image, it is necessary to precisely align toner images of four colors of black, cyan, magenta, and yellow. As in the above-described conventional example, an image forming unit including a photosensitive drum for each color is unitized, and the photosensitive drum for each color is sequentially moved to an image forming position to form an image, and toner images of four colors are superimposed. The configuration for forming a color image is superior to the configuration for forming a color image using a single photosensitive drum in terms of ease of maintenance, but the alignment of toner images of each color (hereinafter referred to as a color position). Alignment).

Factors that deteriorate the alignment accuracy include variations in the outer diameter accuracy and roundness of the photosensitive drum of each color, and the infidelity of the transmission angular velocity generated in the coupling portion between the photosensitive drum and the drive mechanism on the main body side. And the center positioning accuracy of the photosensitive drum, the rotation accuracy of the main body side drive mechanism itself, and the like.

An object of the present invention is to provide a plurality of photoconductors (drums)
Are sequentially moved to one image forming position to form a full-color image, by minimizing the influence of the above factors that make it difficult to align the toner images of each color,
An object of the present invention is to provide a color image forming apparatus capable of performing high-accuracy color registration.

[0011]

According to the present invention, there is provided a color image forming apparatus comprising: a plurality of color image forming units including a drum-shaped photosensitive member having a coupling member at at least one end and a developing device; Transfer means for moving the image forming unit between the retracted position and the image forming position, and the photosensitive member of the image forming unit moved to the image forming position, in order to rotationally drive the photosensitive member positioned at the image forming position, A photoreceptor driving unit having a driving side coupling member having a rotation axis coaxially with the rotation axis of the photoreceptor and detachable from the coupling member of the photoreceptor; An exposure device that exposes a photoconductor, and a color image in which toner images transferred from photoconductors of a plurality of colors are superimposed by transferring a toner image formed on the photoconductor at the image forming position onto a transfer body. Characterized by comprising a transfer means for forming on said transfer body, the transfer member driving means for driving the transfer member predetermined at a constant speed.

According to the above arrangement, since the rotation axis of the photosensitive member coincides with the rotation axis of the photosensitive member driving means, the angular velocity on the driving side of the apparatus main body is faithfully transmitted to the photosensitive member of each image forming unit. Is done. As a result, there is no variation in angular velocity that may occur in the coupling unit for each color image forming unit. On the other hand, a fluctuation component of the peripheral speed of the photoconductor caused by an eccentric component of the outer periphery of the photoconductor from the rotation axis can be absorbed by a slip generated between the transfer body running at a constant speed and the outer periphery of the photoconductor. Therefore, it is possible to accurately align the toner images of each color on the transfer body by minimizing the influence of the variation in the accuracy of the outer diameter and roundness of the photoconductor of each color and the variation in accuracy of the coupling member.

Preferably, the positioning of the photoconductor to the image forming position is performed by positioning both ends of the drum-shaped photoconductor, and the positioning of one end of the photoconductor is performed by the drive-side coupling. This is performed by a member located at the rotation axis of the member positioning the rotation axis of the photoconductor. As a result, the rotation axis of the photoconductor and the rotation axis of the photoconductor driving unit are reliably matched, and accurate positioning of the photoconductor at the image forming position and transmission of the accurate angular velocity can be performed.

It is preferable that the positioning of the other end of the photoconductor is performed by bringing a positioning member into contact with an outer peripheral portion of a shaft member protruding from the other end of the photoconductor.
In this case, the positioning of the photoconductor on the side opposite to the coupling member can be performed with a relatively simple structure such as a detent mechanism.

Further, the end of the output shaft for rotating the drive-side coupling member is engaged with the end of the photosensitive member, so that the photosensitive member at the image forming position is supported by the output shaft. preferable. According to this structure, the rotation axis of the coupling member on the driving side, that is, the axis of the output shaft, and the rotation axis of the photoconductor are almost naturally achieved. Further, since the coupling operation and the positioning operation can be performed by the same member, the structure is simplified.

Further, the photoreceptor shaft protrudes from the end of the photoreceptor, and the end of the output shaft is engaged with the end of the photoreceptor shaft. Are combined without play. Also, this photoconductor shaft is a single shaft penetrating both ends of the photoconductor, and the outer periphery of the photoconductor shaft is formed at the end opposite to the end of the photoconductor shaft with which the end of the output shaft engages. By adopting a structure where the positioning member abuts,
Each photoconductor can be accurately positioned at the image forming position.

Preferably, each of the plurality of image forming units is detachable from the apparatus main body, and the image forming unit further includes a charger for charging a photosensitive member and a toner hopper for storing toner. When the toner in the toner hopper runs out, the entire image forming unit is replaced and all the process elements are unitized, so that toner leakage hardly occurs, reliability is improved, and handling becomes easy. In addition, it is not necessary to use high-precision components for the photoreceptor and the coupling means, and a high-definition color image without color misregistration can be obtained even if inexpensive components having inferior processing accuracy are used.

Preferably, the transfer means holds the plurality of image forming units and simultaneously moves the image forming units so as to sequentially move each image forming unit to the image forming position one by one. It is composed of a carriage. The switching movement of the image forming unit is easily realized by such a simple configuration. Further, the photosensitive member is held by the carriage in a state where the photosensitive member is urged in a predetermined direction, and the photosensitive member is positioned at the image forming position, so that the photosensitive member moves in a direction opposing the urging. If the photosensitive member and the transfer member are configured to be in contact with each other, a dedicated drive mechanism for moving the photosensitive member and the transfer member toward and away from each other becomes unnecessary. Normally, the photoconductor is separated from the transfer member, so that the photoconductor and the transfer member can be prevented from rubbing each other when the image forming unit is switched.

As a specific structure, the carriage is rotatably supported by the apparatus main body, and holds the plurality of image forming units around its rotation axis. Is preferred. In addition, since the photosensitive member is held movably within a predetermined range with respect to the carriage, the photosensitive member can be directly positioned from the apparatus main body side, so that high positioning accuracy is secured.

More preferably, the image forming unit is held movably with respect to the carriage, and the entire image forming unit including the photosensitive member is moved with respect to the carriage by positioning the photosensitive member. The positional relationship between the photoreceptor of each color and the exposure means and the transfer means can always be kept accurate. Conditions such as toner seal around the photoreceptor can be made constant, which contributes to stabilization of operation. There is no need to move the entire carriage when positioning,
Since only the image forming unit with small inertia needs to be moved,
The positioning operation can be performed at high speed. Further, the positioning accuracy of the carriage itself does not need to be particularly accurate.

Preferably, the drive-side coupling means slides in the axial direction with respect to the photosensitive member at the image forming position to engage or disengage with the coupling member of the photosensitive member. According to such a structure, it is easy to make the rotation axis of the drive-side coupling member coincide with the rotation axis of the photoconductor, and a simple structure for simultaneously performing the coupling operation and the positioning of the photoconductor is realized. Cheap.

In positioning the both ends of the photoconductor, it is preferable to position the end of the photoconductor opposite to the end engaged with the drive-side coupling means first. The coupling of the coupling portions is performed smoothly by previously positioning the photoconductor at a substantially accurate position by the positioning means on the side opposite to the coupling portion. Conversely, when releasing the positioning of both ends of the photoconductor positioned at the image forming position, the positioning of the end engaged with the drive-side coupling means is performed before the positioning of the opposite end is released. Is preferred. When a force perpendicular to the output shaft is applied to the coupling member, the coupling is difficult to be released due to frictional force generated on the tooth surface of the engaged coupling member, but the drive side coupling member is engaged. By releasing the positioning of the end first, the coupling is released when the photoconductor is at the correct position.
The coupling is smoothly released.

An output shaft drive gear is fixed to an output shaft for rotating the drive side coupling member. The output shaft drive gear is slidable within a predetermined range in the axial direction while meshing with the driving side gear. It is preferable that the output shaft drive gear, the output shaft and the drive-side coupling means be integrally slid in the axial direction. With such a simple structure, the drive-side coupling member and its output shaft can slide in the photoreceptor axial direction while maintaining the power transmission of the drive-side coupling member to the output shaft.

Further, the output shaft drive gear is a helical gear, and its tooth surface twist direction is made the same as the rotation direction of the photosensitive member. Since the load in the direction of rotating the photoconductor is not applied to the coupling member when the coupling member is separated from the ring member, the coupling can be easily released.

Also, a convex tapered surface is provided at the end of the output shaft for rotating the drive-side coupling member, and a concave tapered surface is provided at the end of the photoreceptor, so that the convex tapered surface of the output shaft extends in the axial direction. It is preferable to position one end of the photoconductor by pressing and engaging the concave tapered surface of the photoconductor. When the concave taper and the convex tapered surface are pressed against each other, the output shaft and the end portion of the photoconductor are connected without play, and more accurate angular velocity transmission becomes possible. Then, the photosensitive member at the image forming position receives the thrust force received from the output shaft by the carriage, so that the switching operation of the photosensitive member is performed smoothly.

The transfer member driving means rotates the transfer member one time each time a toner image of each color is transferred, and makes the ratio of the number of rotations of the drive-side coupling member to one rotation of the transfer member an integer, thereby providing an output. It is possible to suppress a color position shift due to a variation in the angular velocity of the shaft. In other words, the output shaft for driving the photoconductor has an angular velocity fluctuation caused by the pitch error of the output shaft driving gear, but this fluctuation component does not change depending on the photoconductor of each color but is unique to the apparatus main body. Therefore, with the above-described configuration, the displacement of the toner image on the photoconductor due to the angular velocity variation of the output shaft is:
This occurs in the same pattern for all the photoconductors, and does not cause color misregistration on the transfer body. In addition, by setting the rotational speed ratio of the rotating member connected to the driving side coupling member to the driving side coupling member to be an integer, not only the angular velocity fluctuation of the output shaft due to the pitch error of the output shaft driving gear, but also A change in the angular velocity of the output shaft caused by a change in the angular velocity of the rotating member does not cause a color position shift.

When the image forming unit at the image forming position is replaced by the transfer unit, it is preferable that both the photosensitive member driving unit and the transfer unit driving unit are stopped. The coupling between the photoreceptor and the photoreceptor driving unit that is away from the image forming position is released, the photoreceptor stops, and the photoreceptor newly moving to the image forming position moves in a stationary state. When coupling is performed, when the drive-side coupling member is stationary, the coupling operation is performed smoothly, and no impact vibration occurs. At this time, if the transfer member is rotating, it is difficult to synchronize the rotation phase of the coupling member and the transfer member. Can be easily synchronized if they are started at the same time. Further, the peripheral length of the transfer body can be shortened, and there is no need to limit the switching time of the image forming unit.

If the photosensitive member driving unit and the transfer unit driving unit are configured to be driven by a single motor, the rotational phases of the two units do not deviate from each other, and the phase adjustment is easy. In addition, the transfer member is rotated once for each color transfer, and the ratio of the number of rotations of the transfer member of the transfer member driving unit to one rotation of the transfer member is set to an integer. The speed fluctuation component of the transfer body can be synchronized for each color, and the occurrence of color misregistration on the transfer body can be suppressed.

It is preferable that the transfer member is an intermediate transfer belt which is formed of a loop-shaped endless belt and which re-transfers color images taken from the plurality of photosensitive members to another transfer member. Compared with the method of transferring directly to a drum-shaped material or recording paper, the method using such an intermediate transfer belt can stabilize by reducing the contact pressure and frictional force between the photoconductor and the transfer material, so that the transfer is performed. Using the slip between the material and the outer periphery of the photoreceptor, it is easy to correct the recording pitch unevenness caused by the speed fluctuation of the outer periphery of the photoreceptor. Further, there is no possibility that the recording sheet may damage the photoconductor as in the case where the image is directly transferred to the recording sheet. It is also preferable that the ratio of the number of rotations of the drive pulley that drives the intermediate transfer belt to one rotation of the intermediate transfer belt is an integer. As a result, color shift does not occur even if the dimensional accuracy of the pulley that is long in the axial direction is not so high, so that inexpensive components can be used.

Also, at least one guide pulley is provided in the loop of the intermediate transfer belt, and the guide pulley is disposed between a position where the intermediate transfer belt contacts the photosensitive member and the drive pulley on the upstream side. The outer peripheral length of the guide pulley is a fraction of the peripheral length of the intermediate transfer belt.
It is preferred that According to such a configuration, the partial belt length from the driving pulley to the contact position with the photoconductor (that is, the transfer position) changes depending on the rotation angle of the guide pulley due to the eccentric component of the outer periphery of the guide pulley. Even if the belt speed fluctuates, the fluctuation phase of each color can be matched on the intermediate transfer belt, so that color misregistration can be prevented.

Further, it is preferable that a tension pulley for applying tension to the intermediate transfer belt is disposed downstream of a transfer position where the photosensitive member contacts the intermediate transfer belt. In the method of contacting the intermediate transfer belt and the photoconductor by the tension of the intermediate transfer belt, if the photoconductor is eccentric, the belt path changes and the tension pulley moves, but the tension pulley can be arranged downstream from the transfer position. For example, the movement of the tension pulley does not directly affect the speed fluctuation of the intermediate transfer belt at the transfer position, and the constant speed running of the intermediate transfer belt is ensured. Further, as described above, the method of contacting the intermediate transfer belt with the photoconductor by the tension of the intermediate transfer belt is different from the method of providing a backup roller on the opposite side of the photoconductor with the intermediate transfer belt interposed therebetween, for example. Since the contact pressure with the intermediate transfer belt can be reduced, the intermediate transfer belt is less susceptible to fluctuations in the peripheral speed of the photosensitive member, and the intermediate transfer belt runs at a constant speed independent of the photosensitive member. The color misregistration caused by the eccentric element is suppressed.

Preferably, the intermediate transfer belt is stretched over a plurality of pulleys, and a portion between the pulleys comes in contact with the photosensitive member at the image forming position to form an image forming unit at the image forming position. When switching, the photoconductor moves while rubbing the intermediate transfer belt. According to such a configuration, there is no need to provide an approach / separation mechanism between the photoconductor and the intermediate transfer belt, and the structure is simplified. Also,
By sufficiently reducing the contact pressure between the photoconductor and the intermediate transfer belt, damage to the photoconductor due to friction with the photoconductor can be reduced.

Further, there is provided an image-free area where the toner image is not transferred between the transfer end position and the transfer start position of the intermediate transfer belt, and the intermediate transfer member moves while rubbing when the image forming unit is switched. It is preferable that the belt is configured to be always the non-image area. In this case, the image forming unit can be switched without providing a mechanism for approaching / separating the photosensitive member and the intermediate transfer belt and disturbing the image on the intermediate transfer belt. Further, by stopping the driving of the intermediate transfer belt when the image forming unit is switched, the portion of the intermediate transfer belt rubbed when the photosensitive member moves is shortened, so that the peripheral length of the intermediate transfer belt can be shortened. When skipping an unused image forming unit, only the image forming unit needs to be moved while the intermediate transfer belt is stopped, so that the recording time can be reduced without wasting time.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows an internal structure of a color image forming apparatus according to a first embodiment of the present invention as viewed from a side.
The configuration and operation of each unit will be described in order. [Image Forming Unit] In FIG. 1, reference numeral 3 denotes an image forming unit in which the photosensitive member 30 and its peripheral process elements are integrated for each of the colors yellow, magenta, cyan, and black, and each is composed of the following components. Reference numeral 34 denotes a corona charger for uniformly charging the photosensitive member 30 to a negative voltage, 35 denotes a developing device including a developing roller, and 39 denotes a toner hopper. The toner hopper 39 contains a negative voltage charging toner 32 in which a pigment is dispersed in a polyester resin. The toner 32 is carried by the developing roller surface of the developing device 35 and is
Develop 0. Reference numeral 38 denotes a cleaner for cleaning the toner remaining on the surface of the photoreceptor 30 after transfer, and includes a cleaning blade 36 made of rubber and a waste toner reservoir 37 for storing waste toner. Reference numeral 33 denotes an exposure window provided so that the laser beam can enter the image forming unit. The photoreceptor 30 has a diameter of 30 mm, and the developing roller of the developing unit 35 has a diameter of about 16 mm, and is rotatably supported on the side wall of the image forming unit 3. [Transfer Belt Unit] The transfer belt unit 5 is for transferring the toner image formed on the photoconductor 30 at the image forming position 10 and retransferring the toner image to recording paper. The transfer belt unit 5 includes an intermediate transfer belt 50, guide pulley groups 55A to 55D around which the
1 and a waste toner case 57 for accommodating the waste toner after cleaning is integrated and made detachable from the apparatus main body 1.

The intermediate transfer belt 50 has a thickness of about 100 μm.
Endless belt-like semi-conductive (medium electric resistance)
The urethane base material is used as the base material, and the surface layer is made of a fluororesin such as polytetrafluoroethylene (PTFE) or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA), and has a thickness of 100 to 300 μm in total. is there. The circumference of the intermediate transfer belt 50 is A
To enable full-color printing on 4 size or letter size paper, the length in the longitudinal direction of A4 size (297 m
m) plus a length slightly longer than half the circumference of the photosensitive drum (diameter 30 mm) is set at 378 mm.

The cleaner 51 is for cleaning and removing the toner remaining on the intermediate transfer belt 50, and includes a cleaning blade 53 made of rubber and a screw 52 for conveying the scraped toner to a waste toner case 57. . The cleaner 51 is configured to rotate around a fulcrum 58 and separate from the intermediate transfer belt while a color image is formed on the intermediate transfer belt 50.

Guide pulley 55 of intermediate transfer belt 50
A is a drive pulley for driving the intermediate transfer belt 50 and also serves as a backup roller for the cleaning blade 53. The guide pulley 55B is a backup roller for the secondary transfer roller 9 that transfers the toner image on the intermediate transfer belt 50 to the recording paper.
5C applies a primary transfer bias for transferring a toner image from the photoconductor 30 to the intermediate transfer belt 50. The guide pulley 55D is a tension pulley that applies tension to the intermediate transfer belt 50. The intermediate transfer belt 50 is stretched around these guide pulleys,
It rotates according to the rotation of 5A. Reference numeral 56 denotes a cover for protecting the intermediate transfer belt 50. [Configuration of Entire Apparatus] (Image Forming Unit, Carriage) As shown in FIG. 1, a carriage 2 is provided substantially at the center of the apparatus main body 1.
A front alligator 1A is provided on the front (right side in FIG. 1) of the apparatus main body.
Is provided, and a top surface door 17 is provided on the top surface of the apparatus.

The carriage 2 is a four-color image forming unit 3
Y, 3M, 3C, and 3Bk are accommodated, and are rotatably supported by the apparatus main body 1 about a circular tube 21 as an axis. Thereby, the photoconductor 30 of each image forming unit can be rotationally moved between the image forming position 10 and other retreat positions. When the top door 17 is opened, the image forming unit 3 can be easily removed from the carriage 2 by grasping the handle (not shown) of the image forming unit 3. Therefore, when the image forming unit 3 needs to be replaced, the carriage 2 is rotated so that the image forming unit 3 is located immediately below the top door 17, and then the top door 17 is opened and the image forming unit 3 is opened. 3
Can be replaced with a new unit.

The image forming unit 3 for each color is provided at the image forming position 1
Only works when it is at zero. At this time, the photoconductor 30 is irradiated with the laser beam 8, and the transfer belt unit 5 and the photoconductor 30 come into contact with each other. In this position, the image forming unit 3 is connected to a mechanical drive mechanism of the apparatus main body 1 and is also electrically connected to a power source or the like. The image forming unit 3 does not operate at other retracted positions.

(Front alligator, transfer belt unit)
The front alligator 1A is hinged to the main body 1 by a hinge shaft 1B.
And can be opened to fall forward. The fixing devices 15 and 2 are provided on the inner surface of the front alligator 1A.
The front sides of the next transfer roller 9, the static elimination needle 7, and the paper guides 13a to 13d are attached. When the front alligator 1A is tilted forward, these also fall along with the front alligator 1A. As a result, the front surface of the apparatus main body 1 is largely released, and the transfer belt unit 5 can be detached from this portion.
Further, when a paper jam occurs, the jammed paper can be easily removed.

The transfer belt unit 5 is reliably positioned at a predetermined position when the transfer belt unit 5 is mounted on the apparatus main body 1, and the portion of the intermediate transfer belt 50 facing the photosensitive member 30 at the image forming position 10 comes into contact with the photosensitive member 30. I do. In addition, each part of the transfer belt unit 5 is electrically connected to the apparatus main body, and the driving pulley 55A is connected to a driving unit on the apparatus main body side, so that the intermediate transfer belt 50 can rotate. In addition,
The static elimination needle 7 is for preventing the toner image from being disturbed when the recording paper is separated from the intermediate transfer belt 50.

(Optical System) As shown in FIG. 1, a laser exposure device 6 is disposed below the transfer belt unit 5. The laser exposure device 6 includes a semiconductor laser, a polygon mirror 6A, a lens system 6B, a first mirror 6C, and the like. The pixel laser signal light 8 corresponding to the time-series electrical pixel signal of the image information is supplied to the waste toner reservoir 37 of the image forming unit 3Y.
Through the optical path window 24 formed between the image forming unit 3Bk and the toner hopper 39 of the image forming unit 3Bk.
The light passes through 2 and is incident on a mirror 19 located in a circular tube 21. The mirror 19 is fixed to the apparatus main body 1. The laser signal light reflected by the mirror 19 is transmitted from the exposure window 33 of the image forming unit 3Y at the image forming position 10 to the image forming unit 3Y.
The light enters into Y and enters the exposed portion on the left side surface of the photoconductor 30. The photoconductor 30 is exposed by scanning the incident laser signal light in the generatrix direction of the photoconductor (drum) 30.

(Sheet Feeding System) In FIG. 1, reference numeral 12 denotes a sheet feeding unit, 14 denotes a sheet feeding roller, 16 denotes a registration roller, and 18 denotes a sheet discharging roller. 13a, 13b, 13
c and 13d denote these rollers, the intermediate transfer belts 50 and 2
It is a paper guide that connects the contact portion with the next transfer roller 9 and the fixing device 15. Next, the operation of the color image forming apparatus will be described.

In FIG. 1, when the power of the image forming apparatus 1 is turned on in a state where the transfer belt unit 5 and the image forming units 3 of each color are mounted at predetermined positions, the temperature of the fixing unit 15 rises, Polygon mirror 6 of exposure device 6
A starts to rotate and is ready. In some cases, immediately after the power is turned on, an initialization mode for adjusting the state of the photoconductor 30 and the intermediate transfer belt 50 may be operated.

When the preparation is completed, first, the image forming position 10
Starts image formation. At the same time as the yellow photoconductor 30 connected to the drive mechanism of the apparatus main body 1 starts rotating at the image forming position 10, the developing device 35, the charging device 34, and the intermediate transfer belt 50 start moving.
The intermediate transfer belt 50 is rotated in the direction of the arrow in FIG. 1 by driving the drive pulley 55A. At this time, the peripheral speed of the photoconductor 30 and the peripheral speed of the intermediate transfer belt 50 are set to be substantially equal. Further, the secondary transfer roller 9 and the cleaner 51 are separated from the intermediate transfer belt 50.

The charger 34 charges the surface of the photoreceptor 30, and the head position of the intermediate transfer belt 50 is detected by the detecting means in time for the uniformly charged portion to reach the exposure position. Synchronously, a laser beam 8 corresponding to the image signal is emitted from the laser exposure device 6. When a laser beam is irradiated onto the uniformly charged photoreceptor 30, an electrostatic latent image corresponding to an image signal is formed, and the electrostatic latent image is sequentially visualized by a developing device 35 to form a toner image. Is done.
The toner image formed on the photoreceptor 30 moves to a primary transfer position in contact with the intermediate transfer belt 50 as the photoreceptor 30 rotates, and is sequentially transferred to the intermediate transfer belt 50 here. This operation is performed by arranging the end portion of one screen of A4 on the intermediate transfer belt 5.
The yellow image formation is continuously completed until the transfer to 0 is completed, and the photoconductor 30 and the intermediate transfer belt 50 stop at the initial position.

Note that the charger 34 sets the photosensitive member 30 at -450.
V, and the exposure potential of the photoconductor is -50 V. When an uncharged portion of the photoconductor 30 passes through the developing roller, a DC voltage of +100 V is applied to the developing roller. A DC voltage of -250 V is applied to the roller. Further, the guide pulley 55 of the intermediate transfer belt 50
DC voltage of +1.0 kV is applied to C and the tension pulley 55D.

When the formation of the yellow image is completed and the photosensitive member 30 and the intermediate transfer belt 50 are stopped, the drive mechanism of the apparatus main body 1 associated with the yellow photosensitive member 30
Release the connection with 0. When the carriage 2 rotates 90 degrees in the direction of the arrow, the yellow image forming unit 3Y moves away from the image forming position 10 and the magenta image forming unit 3M moves to the image forming position 10 at the same time.
When the magenta image forming unit 3M stops at the image forming position 10, the driving mechanism of the apparatus main body 1 changes the magenta photoconductor 30
The image forming unit 3M and the transfer belt unit 5
Starts operation, and magenta image formation is started. Then, a magenta toner image is formed on the intermediate transfer belt 50 on the intermediate transfer belt 50 by the same operation as the above-described yellow image formation. The same operation as above is repeated for cyan and black, and four color toner images are formed on the intermediate transfer belt 50. While the last black toner image is being formed, the intermediate transfer belt 50
Just before the top of the toner image reaches the position of the secondary transfer roller 9 with the rotation of the
Approach zero. Then, the recording paper sent from the paper supply unit 12 is transferred to the secondary transfer roller 9 and the intermediate transfer belt 50.
The toner images of the four colors are collectively transferred onto the recording paper by being sandwiched between them. At this time, the secondary transfer roller 9
Is applied with a voltage of +300 V. The recording paper to which the toner image has been transferred passes through the fixing device 15 to fix the toner image, and is then discharged from the discharge roller 18 to the outside of the apparatus.

The toner remaining on the intermediate transfer belt 50 after the secondary transfer is scraped off by the cleaning blade 53 coming into contact with the intermediate transfer belt 50. To be housed. When the secondary transfer is completed, the intermediate transfer belt 50 and the image forming unit 3 stop, the carriage 2 rotates 90 degrees, and the yellow image forming unit 3Y moves to the image forming position 10 again. This completes the color image forming operation.

The secondary transfer of the toner image to the recording sheet is performed simultaneously with the formation of the last black toner image as described above. There is also a method of performing the secondary transfer by further rotating the intermediate transfer belt 50 once. [Details of Photoconductor Positioning and Driving Mechanism] Next, the photoconductor 3 of each color for accurately aligning the toner images of each color.
The details of the positioning and driving mechanism of 0 will be described with reference to FIGS.

(Structure of Carriage) In the carriage 2, a right side wall 20R and a left side wall 20L are fixed to a center circular tube 21.
Between the two side walls 20R and 20L, partition plates 23 for partitioning the image forming units 3 of each color are fixed at four positions at regular intervals of 90 degrees. Two partition plates 23 are provided in one place in parallel with a narrow space interposed therebetween. The space between the two partition plates 23 is a space for an optical path through which the laser light 8 passes, and an optical path window 24 is formed. In addition, the circular tube 21 has
A total of eight windows 22 are located at a position corresponding to the optical path 24 and a position where the laser light 8 reflected by the mirror 19 exits.
Is provided.

A right notch 26 for receiving a coupling plate 42 fixed to the photosensitive member of the image forming unit 3 is formed on the outer periphery of the right side wall 20R. A left notch 29 for receiving a collar 43 provided at the left end of the shaft 40 of the photoconductor 30 is formed on the outer periphery of the other left wall 20L. Reference numeral 25 denotes a guide groove formed inside the right side wall 20R and the left side wall 20L, and guides the guide pins 45R and 45L provided on both side walls of the image forming unit 3 to roughly move the image forming unit 3 in the carriage 2. Position. As shown in FIG. 6, when the image forming unit 3 is mounted in the carriage 2, the image forming unit 3 moves the coupling plate 4 with respect to the carriage 2 around the guide pins 45R and 45L.
It is rotatable by a gap between the second cutout 26 and the right cutout 26 or a gap between the collar 43 and the left cutout 29. As an example, these gaps were secured about 1 mm.

The guide pins 45 of the image forming unit 3
Clearances are also provided between R, 45L and the guide groove 25 of the carriage 2 (particularly in the radial direction), and between the outer surface of the image forming unit 3 and each part of the carriage 2. In this manner, the photoconductor 30 is held with play in all directions with respect to the carriage 2. Although not shown, the image forming unit 3 is prevented from dropping from the carriage 2 by providing a protrusion or a member protruding inward on the outer peripheral portion of the both side walls 20R and 20L. Further, in order to hold the image forming unit 3 at a center position indicated by a two-dot chain line in FIG. 6 with respect to the carriage 2, the image forming unit 3 is supported using a spring or the like while being floated from the carriage 2. May be adopted.

In FIG. 2, reference numeral 28 denotes a carriage gear fixed to the left side wall 20L, and is connected to a carriage driving mechanism 86 provided on the main body side. The carriage drive mechanism 86 includes a worm gear 89 connected to a drive source (the motor 100 in FIG. 9), a worm wheel 88 meshing with the worm gear 89, and a gear 87 integrated with the worm wheel 88 and meshing with the carriage gear 28.

The carriage 2 is rotatably supported by bearings 46 on the left and right main body walls 1R, 1L as shown in FIG. 3, and is arranged in parallel with the laser exposure device 6 and the mirror 19. The mirror 19 is directly fixed to the left and right main body walls 1R and 1L by a support member (not shown).

(Cross Section of Photosensitive Member) As shown in FIG. 3, the photosensitive member 30 of the image forming unit 3 has flanges 41 fixed to the inside of both ends of the drum, and a single photosensitive member penetrates these flanges 41. The shaft 40 is fixed. The photoreceptor shaft 40 is rotatably supported on both side walls of the image forming unit 3. A concave taper surface 48 is formed at the right end of the photoreceptor shaft 40, and a coupling plate 42 around which eight pawls 47 protruding in the axial direction are annularly fixed is fixed to the photoreceptor shaft 40. I have. When the coupling plate 42 is rotationally driven, the photoconductor shaft 40 rotates, and at the same time, the photoconductor 30 rotates via the flange 41. A collar 43 serving as a radial bearing is rotatably attached to the left end of the photoreceptor shaft 30.

Next, a photoconductor driving mechanism 60 and a detent mechanism 80 provided on both side walls 1R and 1L of the apparatus main body 1 for accurately positioning and rotating the photoconductor 30 at the image forming position 10 will be described.

(Photosensitive Member Driving Mechanism) The photosensitive member driving mechanism 60 is provided on the right main body wall 1R, and includes an output shaft 70, a coupling plate 61 which rotates integrally with the output shaft 70, an output shaft driving gear 71, and these components. It consists of a driving source for driving. Output shaft 7
Reference numeral 0 denotes a right main body wall 1R and a substrate 67 fixed in parallel with the right main body wall 1R.
Are supported rotatably and movably in the axial direction by bearings 77 provided respectively.

The tapered end portion 75 formed at the end of the output shaft 70 has a convex tapered surface corresponding to the concave tapered surface 48 formed at the right end of the shaft 40 of the photoreceptor 30. The base end of the output shaft 70 is formed in a spherical shape so as to contact the thrust bearing 69 with a small area. The output shaft driving gear 71 fixed to the output shaft 70 is a left-handed helical gear in the same direction as the rotation direction, and meshes with the gear 72 on the driving source side.

Reference numeral 74 denotes a compression spring inserted between the bearing 77 and the output shaft driving gear 71. The compression spring 74 always keeps the output shaft 70 in a direction in which the coupling plate 61 of the output shaft 70 is separated from the coupling plate 42 of the photoconductor 30. It is for energizing. The output shaft 70 is moved from the separated position (FIG. 4) where the coupling plate 61 of the output shaft 70 is separated from the coupling plate 42 of the photoconductor 30 by driving means for moving the thrust bearing 69, and the concave tapered surface of the photoconductor shaft 40. 48 and output shaft 7
0 engagement position with the tip taper portion 75 (FIG. 3)
And can move against the urging force of the compression spring 74.
The driving gear 72 has a sufficient length in the axial direction so that the output shaft driving gear 71 meshes with the driving source gear 72 at any of the separated position and the engaged position. When the output shaft 70 moves in the axial direction, the output shaft driving gear 71 and the driving gear 72 relatively move while sliding on each other on the tooth surface.

The coupling plate 61 is for engaging the coupling plate 42 on the photoreceptor 30 side to transmit power, and like the coupling plate 42, has eight coupling claws 65 protruding in the axial direction. Have. The coupling plate 61 is fixed to the output shaft 70 by a pin 64 in the rotational direction, but is movable in the axial direction by a predetermined amount. With such a configuration, when the tips of the coupling claws 65 and the coupling claws 47 come into contact with each other, the coupling plate 61 is temporarily retracted, and the concave tapered surface 48 of the photoreceptor shaft 40 and the output shaft 70 The engagement with the tip taper portion 75 is not prevented. The coupling plate 61 is urged toward the distal end of the output shaft 70 by the compression spring 62, and is restricted to a position where the coupling plate 61 contacts the distal end stopper 63.

(Detent Mechanism) Next, the detent mechanism 80 provided on the left main body wall 1L will be described. The detent mechanism 80 includes a guide plate 81, a detent lever 82, a solenoid 85 for moving the detent lever 82, and the like. The guide plate 81 is provided near the photosensitive member shaft 4 near the image forming position 10.
The carriage 4 guides the collar 43 provided at the left end of the carriage 2 and moves the collar 4 to a position at a predetermined radial distance from the center of the carriage 2.
3 for positioning, and is fixed to the left main body wall 1L. The detent lever 82 is pivotally attached to the left main body wall 1L by a support shaft 83, and the collar 43 is pressed against the guide plate 81 by a V groove at the tip.
Position accurately. The detent lever 82 is connected to a solenoid 85 via a lever 84. When the solenoid 85 is actuated, the detent lever 82 swings, and its V-groove presses the collar 43 strongly against the guide plate 81.

The components are so arranged that a straight line connecting the axis of the output shaft 70 of the photoconductor drive mechanism 60 and the center of the V-groove of the detent mechanism 80 has a correct parallelism with the laser exposure device 6 and the mirror 19. Are located. Also, the play of the bearing is minimized. As a result, when the photoconductor driving mechanism 60 and the detent mechanism 80 operate, the photoconductor 30 is accurately positioned at the image forming position 10.

(Driving Mechanism of Photoconductor and Intermediate Transfer Belt)
Next, a driving mechanism for driving the photoconductor 30 and the intermediate transfer belt 50 will be described. As shown in FIG. 7, the photoconductor and intermediate transfer belt driving mechanism 90 includes a first motor 95 as a driving source, and reduction gears 92 and 93 connected to the first motor 95. The reduction gear 92 is integrated with the drive source side gear 72 shown in FIG.

The reduction gear 93 meshes with a pulley gear 94 fixed to the driving pulley 55A. The reduction gear 92 meshes with the output shaft driving gear 71 to rotationally drive the photoconductor 30. Reference numeral 91 denotes a motor gear that meshes with the reduction gear 92 and the idler gear 96. The rotation ratios of these gears are all set to integer ratios.

The outer diameter of the driving pulley 55A is 30 mm. When the driving pulley 55A makes four rotations, the intermediate transfer belt 50 having a circumference of 377 mm just makes one rotation. Drive pulley 5
The rotation ratio between the pulley gear 94 fixed to 5A and the reduction gear 93 is 1: 2, and the pulley gear 94 and the idler gear 96
Are set to 1: 4, and the rotation ratio between the pulley gear 94 and the motor gear 91 is set to 1: 6. Further, the rotation ratio between the pulley gear 94 and the output shaft driving gear 71 is 1: 1 and the rotation ratio between the output shaft driving gear 71 and the reduction gear 92 is 1: 2.

(Relationship Between Intermediate Transfer Belt and Photoconductor) FIG. 8
Denotes a photosensitive member 30 located at the image forming position 10 and the intermediate transfer belt 5
It is a figure explaining the positional relationship of 0. When the transfer belt unit 5 is positioned and fixed between the left and right side walls 1L and 1R of the apparatus main body 1, the outer circumference of the photoconductor 30 positioned at the image forming position 10 is, as shown in FIG.
It is located about 1 mm inside the belt from the common tangent line between 5C and the tension roller 55D. Therefore, a constant pressure contact force is applied to the outer peripheral surfaces of the intermediate transfer belt 50 and the photoreceptor 30 by the tension applied to the intermediate transfer belt 50, and the two are uniformly contacted. For example, as shown by an arrow in FIG. 8, sufficient transfer performance was obtained by applying a spring force of about 2 to 3 kg to the tension roller 55D. At this time, the width of the intermediate transfer belt 50 was about 250 mm.

When the image forming unit 3 is switched by rotating the carriage 2, the photosensitive member 30 moves while rubbing the surface of the intermediate transfer belt 50. However, the intermediate transfer belt 50 makes one rotation each time a one-color toner image is transferred, and the non-image area where no image is formed becomes the photosensitive member 3.
Stop in a state where it touches 0. Therefore, the image is not disturbed at the time of color switching, and the image is not affected even if the surface of the non-image area of the belt is slightly worn.

(Carriage Driving Mechanism) FIG. 9 is a configuration diagram of a carriage driving mechanism for driving the carriage 2 to rotate.
9, 89 is the worm wheel 8 shown in FIG.
Worm gear that meshes with 8. The worm gear 89 is integrally connected to the bevel gear 102a by a shaft 97. The bevel gear 102a meshes with the bevel gear 102b, and the bevel gear 102b is connected to the motor shaft 101 of the second motor 100 via a one-way clutch 107.
The one-way clutch 107 transmits only the right rotation of the second motor 100 to the bevel gear 102b, and the left rotation causes the motor shaft 101 to idle and does not transmit the rotation to the gear 102b.

The switching gear 10 is further provided on the motor shaft 101.
4 is connected via a second one-way clutch 108. The second one-way clutch 108 transmits only rotation in a direction opposite to that of the one-way clutch 107 to the switching gear 104. The switching gear 104 is a gear 105
The gear 105 is connected to the fixing device 15, the paper feed / discharge roller group, and the developing device 35 at the image forming position. Therefore, the second motor 100 rotates the carriage 2 when rotating clockwise, and rotates the fixing device 15, the paper feed / discharge roller group, and the developing device 35 at the image forming position when rotating counterclockwise. To switch and drive different devices. Note that a stepping motor is used as the second motor.

(Detection of Carriage Position) FIG. 10 shows position detection means provided on the right side wall 20R of the carriage 2 for detecting the position of the carriage 2. As shown in a perspective view in FIG.
And the detection sensor 110. In FIG. 10, four detection pins 112 (Y, M, C, and Bk) detect the detection sensors 110 before the corresponding image forming unit 3 reaches the image forming position.
, And so as to divide the circumference into four equal parts. Immediately after the detection pin 112Bk corresponding to the black image forming unit 3 (rear side in the rotation direction).
Is provided with another detection pin 117. The detection pin 117 is used to detect the rotational position (initial position) of the carriage 2 as described later.

The position detecting pin 112 is also used for detecting whether the image forming unit 3 is mounted on the carriage 2 or not. The principle of this detection will be described with reference to FIG. When the image forming unit 3 is not mounted on the carriage 2, the detection pin 112 is urged by the compression spring 115 in a direction away from the detection sensor 110 as shown in FIG. Detection sensor 1
Not detected by 10. On the other hand, when the image forming unit 3 is mounted on the carriage 2, the image forming unit 3 pushes the inner end of the detection pin 112 and opposes the urging force of the spring 115 as shown in FIG. To the outside of the right side wall 20R. As a result, the detection pin 112
Becomes a state that can be detected by the detection sensor 110. In addition, 1
Reference numeral 14 denotes a stopper for preventing the detection pin 110 from dropping off the right side wall 20R.

(Operation of Positioning and Driving Mechanism) Next, the operation of the positioning and driving mechanism will be described. When the image forming units 3 of the respective colors are mounted on the carriage 2 and the second motor 100 (FIG. 9) for driving the carriage is rotated to rotate the worm gear 89, the carriage 2 is rotated in the direction of the arrow and yellow. Is carried to the image forming position 10 (FIG. 1). At this time, the output shaft 70 of the photoconductor drive mechanism 60 (FIG. 4) is urged by the spring 74 and descends rearward, and the tapered end portion 75 and the coupling plate 61 are separated from the coupling plate 42 on the photoconductor side. is there. Also, the solenoid 85 of the detent mechanism 80 (FIG. 5) is in the off state, and the detent lever 82 is
At the position indicated by the broken line. The first motor 95 that drives the photoconductor and the intermediate transfer belt is stopped. When the yellow photoreceptor 30 is carried while rubbing the surface of the intermediate transfer belt 50 and comes near the image forming position, the second motor for driving the carriage is stopped, the rotation of the worm gear 89 is stopped, and the carriage 2 is moved. Locked in that position.

As soon as the carriage 2 stops, the solenoid 85 is turned on, and the detent lever 82 is urged in the direction of pressing the collar 43 of the photoreceptor shaft 40 against the guide plate 81 so that the V-groove sandwiches the collar 43 at the specified position. Position.

At the same time, the thrust bearing 69 pushes the output shaft 70 to the left in FIG. 3 against the spring force. Output shaft 70
When the front end tapered portion 75 is pushed out, it starts engaging with the concave tapered surface 48 of the photoreceptor shaft 40, and the photoreceptor shaft 40 is connected to the output shaft 7.
Move forward while aligning with the 0 axis. The tapered end portion 75 and the concave tapered surface 48 are engaged, and further, the thrust bearing 69
Presses the output shaft 70, the axis of the photoreceptor shaft 40 completely coincides with the axis of the output shaft 70, and the photoreceptor 30 is moved to the image forming position 1
Positioned exactly at zero. At this time, the thrust force given by the output shaft 70 presses the end face of the flange 41 against the side plate bearing of the image forming unit 3, and the side plate bearing contacts the left side wall 20 </ b> L of the carriage 2 and is received. When the tip taper portion 75 is engaged with the concave tapered surface 48, the coupling plates 42 and 61 are engaged with each other, so that the rotational force of the output shaft 70 can be transmitted to the photosensitive member 30.

As described above, when the detent mechanism 80 and the photoconductor driving mechanism 60 operate to accurately position the photoconductor 30, the entire image forming unit 3 including the photoconductor 30 moves within the carriage 2. Become. As described above, since the image forming unit 3 is held in the carriage 2 with a certain amount of play, the carriage 2 does not hinder the movement of the image forming unit 3 during positioning. Although the carriage 2 has some play in the rotation direction due to backlash between the spur gear 28 and the gear 87, the photosensitive member 30 is directly positioned by the positioning mechanism on the apparatus main body side. Does not affect the positioning of the photoconductor 30.

Next, when the positioning of the photoconductor 30 is completed, the photoconductor and the first motor 95 for driving the belt start rotating, and the photoconductor 30Y and the intermediate transfer belt 50 start rotating. With the start of these operations, each process element starts operating, and a yellow toner image is sequentially formed on the photoreceptor 30, and this toner image is sequentially transferred onto the intermediate transfer belt 50.

During the operation described above, the output shaft 70 is pressed to the left in FIG. 2 by the thrust bearing 69, and the solenoid 85 is maintained in the on state, and the detent lever 8 is turned on.
2 keeps the collar 42 sandwiched between the guide plate 81 and the guide plate 81.

When the intermediate transfer belt 50 makes one rotation (the photosensitive member 30 and the driving pulley 55A make four rotations, and the guide pulley 55C makes six rotations), the yellow image formation is completed, and the first image formation is completed.
The motor 95 stops, and the intermediate transfer belt 50 stops at the initial position.

When the intermediate transfer belt 50 and the photosensitive member 30 stop, the solenoid 85 is turned off to release the detent, and at the same time, the thrust bearing 69 retreats to the right in FIG.
The output shaft 70 is also retracted rightward by the urging force of the spring 74. As a result, the coupling plate 61 and the tapered end 7
5 is separated from the coupling plate 42 and the photoreceptor shaft 40,
The carriage 2 can be rotated.

The output shaft 70 is driven to rotate counterclockwise when viewed from the right in FIG. When the first motor 95 is stopped and the photoconductor 30 is stopped, the photoreceptor 30 is in a state where the side surfaces of the coupling claw 65 and the coupling claw 47 of the photoreceptor side are pressed against each other due to a rotational load. There is. In this state, frictional force acts on the side surfaces of the claws to make it difficult to pull out the coupling plate 61 from the coupling plate 42. In the present embodiment, the output shaft drive gear 71 is a helical gear, and the twist direction thereof is the same left twist as the rotation direction. Therefore, the coupling plate 61 is rotated in the direction opposite to the drive direction of the photoconductor 30 by the amount corresponding to the twist of the tooth surface. The nail can be easily pulled out without applying frictional force to the nail portion.

In this embodiment, the operation of the detent mechanism 80 and the coupling operation of the output shaft 70 in the thrust direction are simultaneously performed. However, the lateral force is applied to the coupling claw 65 and the coupling claw 47 on the photosensitive member side. When this occurs, a frictional force is applied to the claws, making the detaching operation somewhat difficult. Therefore, it is desirable that the output shaft 70 and the photoreceptor shaft 40 coincide with each other as much as possible during the coupling operation. Therefore, when forming the coupling, the detent mechanism 80
Is operated first to position the one end side of the photoreceptor shaft 40, and then, when the output shaft 70 is moved and the coupling is released, it is more reliable to operate the output shaft 70 before the detent mechanism 80. And smooth operation can be realized.

In particular, when releasing the coupling, the output shaft 7
In the case of a configuration in which 0 is moved by the force of the spring 74, the claws are difficult to separate from each other if a load is applied to the coupling portion. In this embodiment, the output shaft 70 is configured to be returned by the spring 74. The drive mechanism on the thrust bearing 69 side may forcibly return, but the structure of this embodiment using a spring simplifies the structure.

When the coupling is released, the worm gear 89 rotates again, and the carriage 2 is driven to rotate in the direction of the arrow shown in FIG. I do. Then, the detent mechanism 80 and the photoconductor driving mechanism operate again to perform the positioning and coupling operation of the magenta photoconductor 30, and the second color toner image is formed.

As described above, the color switching operation and the toner image formation are repeated to transfer the four color images to the intermediate transfer belt 5.
No. 0 and finally transferred onto recording paper. In one embodiment, the time required for rotating the carriage 2 by 90 degrees is set to about 0.6 seconds, the time required for attaching and detaching the coupling of the output shaft is set to about 0.2 seconds, and the process speed is set to about 0.2 seconds. It was set to 100 mm / sec.

(Operation of Carriage Driving Mechanism) Next, operations of the carriage driving mechanism 86 and the position detecting means of the carriage 2 will be described. First, an initialization operation is performed before recording of an image is started. At this time, the second motor 100 starts right rotation in the direction indicated by the arrow in FIG.
a, worm gear 89, worm wheel 88 (FIG. 2)
And the like. At this time, the other one-way clutch 108 is connected to the switching gear 104 and the gear 1
No torque is transmitted to 05.

When the carriage 2 starts to rotate, the detection sensor 110 (FIG. 10) detects the detection pin 112, thereby recognizing the presence or absence of the image forming unit 3 of each color.
Further, as shown in FIG. 10, only when the detection pin 117 passes through the detection sensor 110, two detection signals are continuously detected, so that the position of the carriage 2 is determined.
The image forming unit 3 (the yellow image forming unit 3Y in this embodiment) of the color to be recorded first is moved to the image forming position 10 and the second motor 100 stops.

When the initialization is completed, the operation proceeds to the color image forming operation. First, when the coupling operation for driving the photosensitive member is completed and the photosensitive member 30 is positioned, the first motor 95 starts rotating, and the photosensitive member 30 and the intermediate transfer belt 50 are rotated.
The second motor 100 starts to rotate left as soon as starts rotating. The left rotation of the second motor 100 rotates the switching gear 104 and the gear 105 via the one-way clutch 108 (FIG. 9), and causes the fixing device 15, the sheet feeding and discharging roller group, and the developing device 35 at the image forming position to rotate. Drive. The transmission mechanism beyond the gear 105 may be an ordinary gear transmission system. At this time, since the second motor 100 rotates counterclockwise, the one-way clutch 107 does not transmit the rotating force, and the carriage 2 remains stationary. Since the transmission system from the one-way clutch 107 to the carriage 2 includes the worm gear 89 and the worm wheel 88, the carriage 2 can maintain the locked state.

Next, when the recording of the first color is completed, the first motor and the second motor are stopped, and the photosensitive member 30, the intermediate transfer belt 50, the fixing device 15, the sheet feeding and discharging rollers, and the image forming position are determined. All of the developing units 35 are stopped, and the coupling of the photoconductor is released. When the coupling is released, the second motor 100 starts rotating clockwise again to rotate the carriage 2.

FIG. 13 shows the change in the rotation speed of the second motor 100 controlled when the image forming unit 3 is switched, and the timing at which the detection sensor 112 detects the detection pin 112. When switching the image forming unit 3, the second motor, which is a stepping motor controlled by open loop, is accelerated and decelerated as shown in FIG. 13, and stops after rotating by a predetermined number of steps. At this time, the mechanical connection between the second motor 100 and the carriage 2 is disconnected by the clutch inserted into the transmission system each time one color image is formed. Since the relationship between the rotation position of the second motor 100 and the rotation position of the carriage 2 is not always constant, the number of pulses from the start to the stop of the rotation of the second motor 100 includes some variation.

Therefore, in this embodiment, first, the carriage 2 is rotated to determine the position of the detection pin 112 by the detection sensor 11.
When 0 is detected, the second motor is stopped after rotating by a certain number of pulses from that point.
While the carriage 2 is rotating, the rotational positional relationship between the carriage 2 and the second motor does not shift, so that the positioning of the carriage 2 can be accurately performed by the above control.

Further, in the present embodiment, as shown in FIG.
Stops the second motor after rotating a certain number of pulses from the point when the detection of the passage of the detection pin 112. Each gear from the motor shaft 101 to the carriage 2 has a backlash, and since the carriage 2 has a large inertia, the position of the second motor 100 and the carriage 2 caused by the backlash during the constant speed rotation. Relationship is unstable. On the other hand, during deceleration, a force is applied in the direction of stopping the carriage 2 against the inertia of the carriage 2, so that the backlash of the transmission system gears is all biased in a certain direction, and the second motor 100 and the carriage 2 Is uniquely determined. As a result, the carriage 2
Can be stopped at the correct position.

In order to switch the image forming unit 3 in a short time in order to increase the recording speed, it is necessary to rapidly accelerate and decelerate the carriage 2 having a large inertia. In this embodiment, since the one-way clutch 107 is inserted in the transmission system, the carriage 2 cannot be decelerated by the braking control of the second motor 100. However, since the worm gear 89 and the worm wheel 88 are interposed between the one-way clutch 107 and the carriage 2, the carriage 2 is braked by these, and the deceleration operation becomes possible.

Further, with the simple structure using the worm gear 89 and the worm wheel 88 as described above,
Even when the carriage 2 is stopped, especially when the power is off, the carriage 2 holding the image forming unit 3 can be locked at an arbitrary position.
This is convenient when you need to replace a device.

In the present embodiment, the carriage has a structure in which the carriage rotates while supporting a plurality of image forming units.
The carriage drive mechanism of the present invention is not necessarily limited to a carriage having such a structure. For example, a structure described in JP-A-63-23172, that is, a structure including a single photosensitive member, a plurality of developing units for each color, and a carriage supporting a plurality of developing units and rotating. The carriage drive mechanism of the present invention can also be applied to the present invention. In the case of this structure, different colors of toner images are sequentially formed on the photoconductor while switching the developing units of each color by rotating the carriage, and the color toner image on the photoconductor is directly transferred to recording paper.

In the carriage drive mechanism of the present embodiment, two one-way clutches 1 are used to transmit the drive force from the second motor while switching the load to two types of loads.
Although 07 and 108 are used, a normal electromagnetic clutch or the like may be used instead of the one-way clutch. The point is that it is only necessary to be able to control the intermittent power transmission, but from the viewpoint of miniaturization and simplification, a one-way clutch is most suitable.

In this embodiment, the detection pin 112 and the interrupter-type photosensor are used as the carriage position detection means. There is no. It is sufficient that the position of the carriage corresponding to each image forming unit can be detected while the carriage is rotating.

Although the stepping motor is used as the second motor 100, any motor can be used as long as it can open and control the rotation angle. For example, an AC servomotor or the like may be used.

(Positioning of Toner Images of Each Color) Next, the positioning of toner images of each color will be described. In order to accurately align the positions of the toner images of each color, the photoconductor 30 and the intermediate transfer belt 50 need to rotate at a constant and accurate speed. In order to realize this, in the present embodiment, the photosensitive member 3
0 and the first motor 95 for driving the intermediate transfer belt 50
The G motor is used, and the first motor 95 is used as a dedicated drive source for the photoconductor 30 and the intermediate transfer belt 50 in order to minimize the load fluctuation applied thereto.

Further, in order to accurately match the leading positions of the toner images transferred to the intermediate transfer belt 50, in forming an image of each color, the first motor 95 was completely driven at a constant speed after the first motor 95 was started. Later, the head position of the intermediate transfer belt 50 is detected, and based on the detection signal, a hole for detecting the head of the intermediate transfer belt 50 and a sensor are provided so as to start recording a latent image on the photoreceptor 30 with a laser beam. Is provided.

Further, in order to secure the positional accuracy, 4
It is necessary to accurately hold the photoconductor 30 at the image forming position 10. In the present embodiment, as described above, the positioning of the photoconductor 30 is performed by directly supporting the photoconductor shaft by the output shaft 70 and the detent lever 82 mounted on the left and right main body walls 1R and 1L. At this time, since the photoconductor 30 is supported in the carriage 2 so as to be freely displaceable within a certain range, the photoconductor 30 can be accurately positioned regardless of the positioning accuracy of the carriage 2.

Next, it is necessary to accurately rotate the photosensitive member 30 positioned correctly. In a conventional transmission mechanism combining a normal spur gear as shown in FIG. 18, since the pitch error due to the eccentric component of the gear on the photoconductor side differs for each color, the transmission error of the angular velocity specific to the photoconductor of each color is reduced. This causes color misregistration (image misregistration of each color). In particular, since the image forming unit including the photoconductor 30 is replaced with a new unit when the toner has been consumed, it is necessary to consider variations in the mechanical accuracy of the gear on the photoconductor side.

In the present embodiment, as described above, the shaft 40 of the photosensitive member 30 and the output shaft 70 on the drive side are coupled so that their axes coincide with each other, so that the angular velocity of the output shaft 70 and the photosensitive member 3
The angular velocity is equal to zero. Accordingly, the angular velocity of the output shaft 70 is accurately transmitted to the photoconductor 30, the photoconductors of the respective colors rotate at the same rotational angular velocity, and the rotational angular velocity does not change even if the photoconductor is replaced. Further, there is no need to require particularly high dimensional accuracy for the coupling member between the photoconductor and the output shaft 70.

Next, if the photosensitive member is eccentric with respect to the center of the concave tapered surface 48 of the photosensitive member shaft 40 which engages with the tapered end portion 75 of the output shaft 70, the peripheral speed of the photosensitive member fluctuates and recording is performed. The pitch changes. If the amount of eccentricity and the phase of each photoconductor are different, color misregistration may occur. In the present embodiment, as described above, the intermediate transfer belt 50 is moved by the tension to the photosensitive member 3.
0, and the intermediate transfer belt 50 is run at a constant speed independently of the peripheral speed of the photoconductor 30. Therefore, the fluctuation of the peripheral speed due to the eccentricity of the photoconductor is absorbed by the occurrence of the slip between the photoconductor 30 and the intermediate transfer belt 50. In other words, the portion recorded with the high peripheral speed and the long recording pitch is compressed and transferred onto the intermediate transfer belt 50, and is expanded and transferred in the reverse case.
Regardless of the fluctuation of the peripheral speed, the recording pitch corresponding to the angular speed is accurately transferred onto the intermediate transfer belt.

Next, an error in the rotational speed and angular speed occurring in the power transmission system on the main body side from the first motor 95 to the output shaft 70 or the intermediate transfer belt 50 is caused by each of the gears 91, 92, one rotation of the intermediate transfer belt 50. 93, 94, 96,
The problem is solved by setting the rotation ratio of the drive pulley 71 (FIG. 7) and the rotation ratio of the drive pulley 55A and the guide pulley 55C (FIG. 8) to integral multiples. With the above configuration, each gear and each pulley return to the initial position for each color recording and start recording from the same initial position for each color, so that the deviation amount and phase from the ideal recording position are the same for each color. In addition, color misregistration on the intermediate transfer belt 50 is eliminated.

As described above, according to the present embodiment, after the photosensitive member 30 is accurately positioned at the image forming position on the apparatus main body, the coupling portion for engaging the main body side drive shaft 70 with the photosensitive member 30 is used. And the recording pitch error caused by the eccentricity of the outer periphery of the photosensitive member 30 from the rotation axis is absorbed by slipping with the intermediate transfer belt 50 running at a constant speed, and further caused by the transmission mechanism on the main body side. This problem is solved by matching the amount of phase shift and the phase due to the fluctuation of the running speed of the intermediate transfer belt 50 for each color. In this manner, a high-precision color image without color misregistration can be recorded even when a plurality of photosensitive members having dimensional accuracy variations are switched and used.

As an example, the outer diameter of the photoconductor 30 is set to 30.
mm, the outer peripheral speed of the photoconductor 30 and the intermediate transfer belt 50
Peripheral speeds were made substantially equal. In another embodiment, the photoconductor 3
The outer diameter of 0 is set to be larger by about several percent, and the photoconductor 30 is always slid with respect to the intermediate transfer belt 50 to run. In this case, the direction in which the frictional force is applied to the intermediate transfer belt 50 is always constant even if the photosensitive member and the intermediate transfer belt 50 have some speed fluctuation, so that the frictional force is stabilized.
As a result, the intermediate transfer belt 50 was able to run at a constant speed in a more stable state, and a more accurate color image was obtained. At this time, since the output shaft driving gear 71 has the same number of rotations as the driving pulley 55A, the rotation synchronization between the photoconductor and the intermediate transfer belt 50 is not lost.

In this embodiment, a gear is used as the speed reduction mechanism between the first motor 95 and the drive pulley 55A and the output shaft drive gear 71. Instead, a speed reduction mechanism using a belt and a pulley may be used. Good. Again,
If the rotational speed ratio of the rotating member is set to an integral multiple, the same effect as in the present embodiment can be obtained.

In determining the outer diameter of the drive pulley 55A and the peripheral length of the intermediate transfer belt 50, the rotation ratio of the drive pulley 55A to one rotation of the intermediate transfer belt 50 is set to an exact integer multiple in consideration of the belt thickness. Is preferred.

As an example, the outer diameter of the guide pulley 55C of the transfer belt unit 5 was set to 20 mm, and the rotation ratio of the guide pulley 55C to the intermediate transfer belt 50 was set to an integral multiple. When the guide pulley 55C is eccentric, the belt moving speed at the transfer position varies due to a change in the partial length of the belt from the drive pulley 55A to the transfer position at which the photoconductor 30 and the intermediate transfer belt 50 contact. This variation occurs in synchronism with the rotation of the belt in the same pattern in the transfer of the toner image of each color by making the rotation speed ratio between the guide pulley 55C and the intermediate transfer belt 50 an integer multiple as described above. No color shift occurs due to this variation. In the case of an embodiment in which a plurality of guide pulleys are arranged between the drive pulley 55A and the upstream side of the transfer position, the guide pulleys are set so that the rotation ratios of the guide pulleys to the intermediate transfer belt 50 are all integral multiples. It is desirable to set the outer diameter of

Further, by disposing the tension pulley 55D on the downstream side of the transfer position where the intermediate transfer belt 50 and the photosensitive member 30 are in contact with each other, even if the photosensitive member 30 is slightly eccentric, the intermediate transfer belt 50 can be moved at the transfer position. The moving speed is hard to fluctuate. If the tension pulley 55D is located upstream of the transfer position and the photoconductor 30 is eccentric, the photoconductor 3
The amount of biting into the intermediate transfer belt 50 of 0 fluctuates, whereby the tension pulley 55D swings. As a result, the belt portion length from the drive roller 55A to the transfer position fluctuates, and the belt speed at the transfer position fluctuates.
Since the speed fluctuation of the belt is caused by the eccentricity inherent to the photoconductor 30 of each color, the fluctuation pattern differs for each color, causing a color position shift.

In this embodiment, the intermediate transfer belt is used as the transfer member for transferring the toner images on the photosensitive members of a plurality of colors in a superimposed manner. However, the present invention is not necessarily limited to the use of the intermediate transfer belt. The present invention is also applicable to a configuration using an intermediate transfer drum. Alternatively, the present invention can also be applied to a method in which a recording sheet is wound around a drum and the image is directly transferred from the photosensitive member to the recording sheet.
In short, a configuration in which the transfer body runs at a constant speed independently of the photoconductor, and variations in the outer diameter accuracy of the plurality of photoconductors can be absorbed by causing a slip between the transfer body and the photoconductor. Should be fine. For this purpose, it is preferable that the photosensitive member and the transfer member are in light contact or non-contact. (Second Embodiment) FIG. 14 shows a coupling portion between an output shaft and a photosensitive member of a color image forming apparatus according to a second embodiment of the present invention. 14, an engagement pin 78 fixed to the output shaft 70 is an alternative member of the coupling plate 61 (FIG. 4) in the first embodiment. This engagement pin 78
When the tip tapered portion 75 of the output shaft 70 is engaged with the concave tapered surface 48 (FIG. 3) at the shaft end of the photoconductor 30, it enters the groove of the claw 47 of the coupling plate 42 on the photoconductor 30 side. To engage the coupling plate 42 to enable the photoconductor 30 to be driven to rotate. Since the axis of the output shaft 70 and the rotation center of the photoconductor 30 are coaxial, and the output shaft 70 supports the shaft 40 of the photoconductor 30, a coupling having such a simple configuration is sufficient. Function can be exhibited.

Note that, contrary to the present embodiment, an engaging pin is provided on the photosensitive member 30 side, and this engaging pin is related to a coupling plate (the same shape as in the first embodiment) on the output shaft side. It may be configured to match. (Third Embodiment) FIG. 15 shows a coupling portion between an output shaft and a photoreceptor of a color image forming apparatus according to a third embodiment of the present invention. In FIG. 15, the output shaft 70 and the coupling plates 42 and 61 provided on the photoconductor 30 are exactly the same as those in the first embodiment, but the end of the output shaft 70 is the same as the end of the photoconductor shaft 40. The supporting structure is different from that of the first embodiment. A positioning hole 49 is formed at an end of the photoreceptor shaft 40, and an engagement shaft 79 having a size that fits into the positioning hole 49 of the photoreceptor shaft 40 is formed at an end of the output shaft 70. When the output shaft 70 is pushed out in the direction of the arrow in FIG. 15, the engagement shaft 79 fits into the positioning hole 49, and the output shaft 70
And the photoreceptor shaft 40 are integrated. In this state, the coupling plates 42 and 61 are engaged, and transmission of the rotational force from the output shaft 70 to the photosensitive member shaft 40 becomes possible. At this time, no thrust force is applied to the photoreceptor shaft 40. In the case of the present embodiment, if there is a gap between the engagement shaft 79 and the positioning hole 49, the axial center of the output shaft 70 and the photosensitive member shaft 40 is shifted, and the peripheral speed of the photosensitive member 30 varies. Therefore, the clearance between the engagement shaft 79 and the positioning hole 49 needs to be strictly controlled. In this embodiment, similarly to the above-described embodiment, since the axis of the output shaft 70 and the rotation center of the photoconductor are coaxial, the rotation of the photoconductor as shown in FIG. The rotation angular velocity of the output shaft 70 can be transmitted to the photoconductor 30 more faithfully than a drive mechanism in which the center and the axis of the output shaft are not located coaxially at all.

In particular, in the case where the image forming unit in which the photosensitive member is integrated with another process member is frequently replaced, the gear 232 provided on the photosensitive member 218 is usually used in the conventional photosensitive member driving mechanism shown in FIG. Since an inexpensive molded gear is used, the dimensional accuracy is poor and the dispersion is large. Therefore, the rotational angular velocity of the main body side output shaft 245 cannot be transmitted to the photoconductor 218 faithfully. That is, microscopically, the photoconductors of each color rotate at different angular velocities. As a result, the toner image recorded on the photoreceptor includes a pitch shift of a different pattern for each color, and this pitch shift cannot be absorbed by the slip between the photoconductor and the intermediate transfer belt. A color position shift occurs.

On the other hand, in the photoreceptor driving mechanism according to the present invention, the rotation center of the photoreceptor and the axis of the output shaft are coaxial, and the photoreceptor shaft is supported by the output shaft. The rotational speed of the output shaft is faithfully transmitted to the photoreceptor regardless of the dimensional accuracy of the coupling member because the photoreceptor shaft is rotated while the output shaft and the output shaft are coupled. If the rotation angular velocity of the output shaft is faithfully transmitted to the photoconductor, the accuracy of the photoconductor (outer diameter accuracy, roundness, straightness, etc.) and the accuracy of the coupling member, flange, etc. are all outside the photoconductor with respect to the rotation center. It can be considered as the eccentric component of the circumference. As previously mentioned,
The fluctuation of the recording pitch caused by the fluctuation of the peripheral speed of the photoconductor caused by the eccentric component of the outer circumference with respect to the rotation center of the photoconductor is that the rotation speed of the photoconductor is constant and the intermediate transfer belt is running at a constant speed. For example, the slippage occurs between the photoconductor and the intermediate transfer belt, so that the correction is performed on the intermediate transfer belt. Therefore, it is possible to eliminate color misregistration between colors.

In the configuration of the coupling portion between the output shaft and the photosensitive member shown in FIG. 15, the output shaft 70 is a cylindrical shaft, and the engagement shaft 79 is dedicated to positioning which does not rotate and passes through the output shaft 70. As a shaft, a non-rotating photosensitive member shaft 40 is positioned and fixed, and a coupling plate 4 integrated with the photosensitive member 30 is provided.
2 may be rotated around the photoreceptor shaft 40. Also in this case, it can be said that the structure is such that the axis of the output shaft and the rotation center of the photoconductor are coaxial, and the photoconductor shaft is supported by the output shaft (including the engagement shaft). It is preferable that the cylindrical output shaft 70 and the photoreceptor 30 are integrally connected without slipping or play, and the photoreceptor 30 is rotated while being supported by the output shaft 70. As a structure for supporting the photosensitive member 30, in addition to the structure shown in FIG. An integrated structure is also possible.

The carriage is not limited to the type in which the plurality of image forming units are switched to the image forming position by rotation as in the present embodiment, and supports a plurality of image forming units arranged in a plane. A configuration may be employed in which a plurality of image forming units are switched to image forming positions by reciprocating operation. (Fourth Embodiment) FIG. 16 shows the structure of a carriage of a color image forming apparatus according to a fourth embodiment of the present invention. FIG. 16 is a side view of the carriage 2 as viewed from the axial direction, and the image forming unit 3 is indicated by a two-dot chain line at one of four places divided in the circumferential direction. And carriage 2
A pressing leaf spring 66 for urging the image forming unit 3 inward in the radial direction is provided on the side walls 20R and 20L. FIG.
In FIG. 6, only one of the four locations of the holding plate spring 66 is shown, and the other three locations are omitted.

When the image forming unit 3 is mounted on the carriage 2, the image forming unit 3 is urged radially inward by the pressing leaf spring 66, so that the center of the photosensitive member 30 is at the position A in FIG. . While the carriage 2 is rotating to switch the image forming units 3, all four image forming units 3 are at this position. Since the center of the photoconductor 30 has receded to the position A in FIG. 16, the surface of the photoconductor 30 does not rub against the surface of the intermediate transfer belt 50,
0 can move to the image forming position 10.

When the image forming unit 3 is carried to the image forming position 10 by the carriage 2, the output shaft 70 is pushed out and the tapered end portion 75 is moved to the photosensitive member shaft 40 as described in the first embodiment. Engages with the concave tapered surface 48.
The alignment between the output shaft 70 and the photoreceptor shaft 40 is performed by the engagement between the tip tapered portion 75 and the concave tapered surface 48. As a result, the center of the photoreceptor 30 moves from the position A to the position B in FIG. As a result, the outer peripheral surface of the photoconductor 30 contacts the intermediate transfer belt 50.

The detent mechanism 80 for positioning the collar 43 provided on the opposite side of the concave tapered surface 48 of the photosensitive member shaft 40 is different from the guide plate 81 in the configuration of the first embodiment shown in FIG. It is preferable that the positional relationship with the detent lever 82 be reversed so that the collar 43 is moved by the detent lever 82 in a direction of being drawn radially outward.

When the coupling mechanism and the detent mechanism are released, the image forming unit 3 moves inward in the radial direction of the carriage 2, the outer peripheral surface of the photosensitive member 30 is separated from the intermediate transfer belt 50, and the center of the photosensitive member 30 is positioned as shown in FIG. Return to position A. With such a configuration, the photosensitive member does not move while rubbing the intermediate transfer belt when the image forming unit is switched.
Further, the photosensitive member can be moved in and out of the image forming position by a simple means using a holding plate spring without providing a special driving means.

[0122]

As described above, the color image forming apparatus according to the present invention employs a method of sequentially moving a plurality of photosensitive members to one image forming position to form a full-color image while using a photosensitive member of each color. Variations in the outer diameter accuracy and roundness of the drum, infidelity of the angular velocity transmitted at the coupling between the photoconductor drum and the drive mechanism on the main unit, center positioning accuracy of the photoconductor drum, and rotation accuracy of the main unit drive mechanism itself It is possible to reduce color misregistration caused by the above, and realize highly accurate color registration.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an internal structure of a color image forming apparatus according to a first embodiment of the present invention as viewed from a side.

FIG. 2 is an exploded perspective view showing a carriage and photosensitive member positioning and driving mechanism of the color image forming apparatus of FIG. 1;

FIG. 3 is a cross-sectional view of the carriage cut along a plane including the axis of the photoconductor at an image forming position of the color image forming apparatus of FIG. 1;

FIG. 4 is a perspective view of a driving mechanism for driving a photoconductor of the color image forming apparatus of FIG. 1;

FIG. 5 is a side view showing a shaft positioning mechanism provided on a side opposite to a driving mechanism of the photoconductor of the color image forming apparatus of FIG. 1;

FIG. 6 is a cross-sectional view of the color image forming apparatus of FIG. 1 taken along a plane perpendicular to an axis of the carriage.

FIG. 7 is a power transmission diagram of a main body-side driving mechanism for driving the photoconductor and the intermediate transfer belt of the color image forming apparatus of FIG. 1;

FIG. 8 is a detailed view showing a positional relationship between a photosensitive member and an intermediate transfer belt of the color image forming apparatus of FIG.

FIG. 9 is a cross-sectional view of the carriage driving mechanism of the color image forming apparatus of FIG. 1 viewed from the axial direction of the carriage.

10 is a configuration diagram of a carriage position detecting unit of the color image forming apparatus of FIG.

FIG. 11 is a perspective view of the carriage position detecting means of FIG.

FIG. 12 is an operation explanatory diagram showing that the carriage position detecting means of FIG. 10 also functions as the mounting detecting means of the image forming unit.

13 is a diagram illustrating a relationship between a rotation speed control profile of a carriage driving motor of the color image forming apparatus of FIG. 1 and a carriage position detection timing.

FIG. 14 is a perspective view illustrating a structure of a coupling portion between an output shaft and a photoconductor of a color image forming apparatus according to a second embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating a structure of a coupling portion between an output shaft and a photoconductor of a color image forming apparatus according to a third embodiment of the present invention.

FIG. 16 is a diagram illustrating a unit that regulates a position of an image forming unit in a carriage of a color image forming apparatus according to a fourth embodiment of the present invention.

FIG. 17 is a cross-sectional view showing an internal structure of a conventional color image forming apparatus as viewed from a side.

18 is a diagram illustrating a structure of a coupling portion between an output shaft and a photoconductor of the color image forming apparatus of FIG. 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Carriage 3 Image forming unit 10 Image forming position 19 Mirror 30 Photoconductor 40 Photoconductor shaft 42 Coupling plate 50 Intermediate transfer belt 55A Driving pulley 60 Photoconductor driving mechanism 61 Drive coupling plate 70 Output shaft 71 Output shaft Driving gear 75 Tip taper portion 80 Detent mechanism 86 Carriage driving mechanism 89 Worm gear 90 Driving mechanism for photoconductor and intermediate transfer belt 95 First motor 100 Second motor 107 One-way clutch

Continuation of front page (72) Inventor Masahiro Aizawa 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (33)

[Claims] A plurality of image forming units each including a drum-shaped photosensitive member having at least one end provided with a coupling member and a developing device; Transfer means for moving the photosensitive member of the image forming unit moved to the image forming position,
In order to rotate and drive while positioned at the image forming position,
A photoreceptor driving unit having a rotation axis coaxially with the rotation axis of the photoreceptor, and having a drive-side coupling member detachable from the coupling member of the photoreceptor; An exposure device that exposes a photoconductor, and a color image in which toner images transferred from photoconductors of a plurality of colors are superimposed by transferring a toner image formed on the photoconductor at the image forming position onto a transfer body. A color image forming apparatus comprising: a transfer unit that forms the image on the transfer body; and a transfer body driving unit that drives the transfer body at a predetermined constant speed. 2. The positioning of the photoconductor to an image forming position is performed by positioning both ends of the drum-shaped photoconductor, and the positioning of one end of the photoconductor is performed by the drive-side coupling member. 2. The color image forming apparatus according to claim 1, wherein the member positioned at the rotation axis of the photoconductor is positioned by positioning the rotation axis of the photoconductor. 3. The color image forming apparatus according to claim 2, wherein the positioning of the other end of the photoconductor is performed by bringing a positioning member into contact with an outer peripheral portion of a shaft member protruding from the other end of the photoconductor. apparatus. 4. A photoconductor at the image forming position is supported by the output shaft by engaging an end of an output shaft for rotating the drive-side coupling member with an end of the photoconductor. 2. The color image forming apparatus according to 1. 5. A color image forming apparatus according to claim 4, wherein a photoreceptor shaft projects from an end of said photoreceptor, and an end of said output shaft engages with an end of said photoreceptor shaft. 6. The photoconductor shaft is a single shaft penetrating both ends of the photoconductor, and a photoconductor shaft is provided at an end opposite to an end of the photoconductor shaft with which an end of the output shaft engages. 6. The color image forming apparatus according to claim 5, wherein a positioning member abuts an outer peripheral portion of the color image forming apparatus. 7. The color image forming apparatus according to claim 1, wherein each of the plurality of image forming units is detachable from an apparatus main body. 8. The color image forming apparatus according to claim 7, wherein said plurality of image forming units further include a charger for charging a photoconductor and a toner hopper for storing toner. 9. The transfer means holds the plurality of image forming units and simultaneously moves the image forming units, thereby moving each image forming unit one by one to an image forming position. 2. The color image forming apparatus according to claim 1, further comprising a carriage. 10. The photosensitive member is held by the carriage in a state where the photosensitive member is urged in a predetermined direction, and the photosensitive member is positioned at the image forming position, so that the photosensitive member is opposed to the urging. 10. The color image forming apparatus according to claim 9, wherein a body moves and the photoconductor and the transfer body come into contact with each other. 11. The color image forming apparatus according to claim 10, wherein the carriage is rotatably supported by the apparatus main body, and holds the plurality of image forming units around a rotation axis thereof. 12. The color image forming apparatus according to claim 10, wherein said photosensitive member is held movably within a predetermined range with respect to said carriage. 13. The image forming unit according to claim 12, wherein the image forming unit is held movably with respect to the carriage, and the entire image forming unit including the photosensitive member moves with respect to the carriage by positioning the photosensitive member. Color image forming apparatus. 14. The drive-side coupling member slides in the axial direction with respect to the photoconductor at the image forming position to engage or disengage with the coupling member of the photoconductor. The color image forming apparatus as described in the above. 15. The color image according to claim 14, wherein, when positioning both ends of the photoconductor, positioning of an end of the photoconductor opposite to an end engaged with the drive-side coupling means is performed first. Forming equipment. 16. When releasing the positioning of both ends of the photosensitive member positioned at the image forming position, the positioning of the end engaged with the drive-side coupling means is performed by releasing the positioning of the opposite end. 15. The color image forming apparatus according to claim 14, which is performed first. 17. An output shaft drive gear is fixed to an output shaft for rotating the drive side coupling member, and the output shaft drive gear is slidable within a predetermined range in an axial direction while meshing with a driving side gear. 15. The color image forming apparatus according to claim 14, wherein the output shaft drive gear, the output shaft, and the drive side coupling unit slide integrally in the axial direction. 18. The color image forming apparatus according to claim 17, wherein the output shaft driving gear is a helical gear, and the torsional direction of the tooth surface is the same as the rotation direction of the photoconductor. 19. A convex tapered surface is provided at a tip end of an output shaft for rotating the drive-side coupling member, and a concave tapered surface is provided at an end of the photoreceptor. 15. The color image forming apparatus according to claim 14, wherein one end side of the photoconductor is positioned by being pressed in an axial direction and engaging with the concave tapered surface of the photoconductor. 20. The color image forming apparatus according to claim 19, wherein the photosensitive member at the image forming position receives a thrust force applied from the output shaft to the carriage. 21. The transfer member driving means rotates the transfer member one rotation each time a toner image of each color is transferred, and the ratio of the number of rotations of the drive side coupling member to one rotation of the transfer member is an integer. The color image forming apparatus according to claim 1. 22. The color image forming apparatus according to claim 21, wherein a rotational speed ratio of the rotating member connected to the driving side coupling member to the driving side coupling member is an integer. 23. When the transfer unit switches the image forming unit at the image forming position, both the photosensitive member driving unit and the transfer member driving unit are stopped.
The color image forming apparatus as described in the above. 24. The apparatus according to claim 23, wherein the photoconductor driving unit and the transfer body driving unit are driven by a single motor.
The color image forming apparatus as described in the above. 25. The ratio of the number of rotations of the rotation member of the transfer member driving means to one rotation of the transfer member is an integer.
The color image forming apparatus as described in the above. 26. The color image according to claim 1, wherein the transfer member is an intermediate transfer belt that is formed of a loop-shaped endless belt and that re-transfers color images taken from the plurality of photoconductors to another transfer member. Forming equipment. 27. The image forming apparatus according to claim 26, wherein a rotation speed ratio of a driving pulley that drives the intermediate transfer belt to one rotation of the intermediate transfer belt is an integer. 28. At least one guide pulley is provided in a loop of the intermediate transfer belt, and the guide pulley is arranged between a position where the intermediate transfer belt contacts the photosensitive member and the drive pulley on the upstream side, 28. The color image forming apparatus according to claim 27, wherein an outer peripheral length of the guide pulley is a fraction of an integral length of the intermediate transfer belt. 29. The color image according to claim 27, further comprising a tension pulley for applying a tension to the intermediate transfer belt, wherein the tension pulley is disposed downstream from a transfer position where the photoconductor and the intermediate transfer belt come into contact with each other. Forming equipment. 30. The image forming apparatus according to claim 26, further comprising a tension pulley for applying a tension to the intermediate transfer belt, wherein the intermediate transfer belt is pressed against a photosensitive member at the image forming position by a tension applied from the tension pulley. . 31. The intermediate transfer belt is stretched over a plurality of pulleys, and a portion between the pulleys contacts the photoconductor at the image forming position to switch the image forming unit at the image forming position. 27. The color image forming apparatus according to claim 26, wherein the photoconductor moves while rubbing the intermediate transfer belt. 32. An image-free area where a toner image is not transferred between a transfer end position and a transfer start position of the intermediate transfer belt, and the intermediate member moves while rubbing when the image forming unit is switched. 32. The color image forming apparatus according to claim 31, wherein a portion of the transfer belt is always the non-image area. 33. The image forming apparatus according to claim 31, wherein driving of the intermediate transfer belt is stopped when the image forming unit is switched.