JP2015102634A - Latent image carrier drive mechanism, process unit, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow gear rotation position to be adjusted easily with respect to a photoreceptor, when a drive gear of a latent image carrier unit having the photoreceptor is integrated with the photoreceptor.SOLUTION: A photoreceptor 2 includes a driven gear section 301 to be detachably engaged with a drive gear 25 arranged in a latent image carrier unit mounting position of the device body. At an end of the photoreceptor 2, an engaged section 30a fixed to the photoreceptor 2 and an engaging member 30d to be brought into contact with/separated from it, are arranged. The driven gear section 301 is arranged in the engaging member 30d. When the engaging member 30d is disengaged from the engaged section 30a, the engaging member 30d is freely rotatable.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and the like, in which a visible image formed on each of a plurality of latent image carriers is superimposed on a transfer material to obtain a superimposed image, and the image forming apparatus The present invention relates to a process unit mounted on the apparatus and a latent image carrier driving mechanism.

  Developing a photosensitive member as a latent image carrier corresponding to black (Bk), yellow (Y), magenta (M), and cyan (C), and an electrostatic latent image formed on each photosensitive member, respectively. A so-called tandem type image forming apparatus that obtains a color image by sequentially superimposing the obtained color toner images on a transfer material is known.

  In this tandem type image forming apparatus, usually, a photoconductor for forming a black toner image is rotationally driven by a drive source different from other photoconductors. The reason why the driving source is different for the black photosensitive member is that the demand for monochrome printing is higher than that for color printing. This is because during monochrome printing, which is in high demand, by driving only the black photoconductor, consumption of other photoconductors and motors can be suppressed, and energy can be saved.

  Further, in this tandem type image forming apparatus, each toner image on a plurality of photoconductors is sequentially superimposed on a transfer material to form a color image. Therefore, if the overlapping position of each toner image is shifted, a so-called color is formed. Deviation occurs. This color misregistration is mainly caused by a drive gear mounting eccentricity provided on the photosensitive member, a gear forming accuracy, a speed variation caused by a joint portion connecting the driving gear and the photosensitive member, and the like.

  When the drive gear of the photoconductor is eccentric, the surface movement speed of the photoconductor fluctuates periodically, and the toner image transferred onto the surface of the transfer material is periodically expanded and contracted due to this fluctuation. . Therefore, when the period of expansion / contraction of the toner image by each photoconductor does not coincide on the surface of the transfer material, color misregistration occurs.

  In general, in an image forming apparatus, the position and size of each process unit may change slightly due to changes in internal temperature or external force, but these changes are unavoidable. It is. For example, when operations such as paper jam processing, parts replacement by maintenance, and movement of the image forming apparatus are performed, an external force is applied to the process unit.

  When such an external force or a change in the internal temperature occurs, the optical path of the laser light emitted from the optical writing unit as an exposure device changes slightly, and the light of each color (Bk, C, M, Y) is exposed. The optical writing position in the sub-scanning direction with respect to the body slightly changes. As a result, a positional shift of the superimposition of the Bk, C, M, and Y toner images in the sub-scanning direction occurs, and a color shift due to this occurs.

  In an image forming apparatus using a plurality of colors such as Bk, C, M, and Y, color detection is performed by performing phase detection and phase control of rotation unevenness of each color photoconductor to control image formation start timing. Image formation without deviation can be performed. However, this phase detection and phase control requires a predetermined time. For example, when the process unit is attached or detached, the rotational direction coupling position of the photosensitive drum and the drum driving gear changes, and thereby the phase of rotational unevenness shifts between the photosensitive members of the respective colors. Therefore, if the phase detection and phase control are performed each time the process unit is attached / detached, a loss of image forming time occurs.

  Therefore, conventionally, in order to suppress the color misregistration, a technique has been proposed in which a driving gear and a photoconductor are mounted on the apparatus main body so that the speed fluctuation phases of the photoconductors are matched. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-4087) proposes an invention in which the rotational direction coupling position between the photosensitive drum and the drum driving gear is always constant even when the process unit is attached or detached.

  Further, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2009-063771), regarding the phase of the speed fluctuation of the Bk and CMY color photoreceptors, the speed fluctuation of the Bk photoconductor is the speed fluctuation of the remaining CMY photoconductors. There has also been proposed an invention in which the drive of Bk is controlled so as to fall between the maximum value and the minimum value in each phase.

  However, these inventions are premised on a coupling system in which a drum driving gear is disposed on the apparatus main body side, and the drum driving gear is detachably coupled to a photoconductor via a coupling. In the coupling method, it is necessary to retract the coupling in the axial direction when attaching or detaching the process unit having the photosensitive member. For this reason, there is a problem that it is difficult to reduce the size of the apparatus because it is necessary to secure the retreat space in the machine.

  Therefore, some image forming apparatuses use a drum drive gear that is integrally attached to the photosensitive member in the process unit (this is referred to as a “drive gear integrated system” for convenience). Then, when the process unit is mounted, the drum driving gear is meshed with a main body side driving gear disposed in the apparatus main body so as to be covered from above.

  However, in this drive gear integrated system, each time the process unit is attached or detached, the meshing position of the drum drive gear of the process unit and the drive gear on the main body side shifts. There was a difficult problem. In particular, when the black and color photoconductors are driven by a single drive source, the above-mentioned phase control is impossible, and even when the black and color photoconductors are driven separately, the color photoconductors are not connected to each other. Phase control is impossible. Another problem is that if the photoconductor gears are damaged or worn, the entire photoconductor must be replaced, increasing repair costs.

  In view of the above problems, the present invention has a configuration in which the driven gear portion of the latent image carrier is integrated with the latent image carrier, and the rotation position of the driven gear portion relative to the latent image carrier can be easily adjusted. An object is to provide an image carrier unit.

  In order to solve the above problems, the present invention provides a latent image carrier unit that has a latent image carrier that carries a latent image on its surface and is detachably attached to the main body of the image forming apparatus. The body unit is movably attached to the engaged portion provided on the latent image carrier and the latent image carrier unit, and is moved relative to the engaged member by movement in a predetermined direction in the latent image carrier unit. An engaging member that engages in a relatively non-rotatable manner and is separated from the engaged member by movement in a direction opposite to the predetermined direction, and is freely rotatable with respect to the latent image carrier unit; and A latent image carrier unit having a driven gear portion that is integrally disposed and capable of transmitting a rotational driving force from the outside of the latent image carrier unit.

  In the latent image carrier unit of the present invention, the engaging member having the driven gear portion is configured to be engageable and disengageable with respect to the engaged member of the latent image carrier. The rotational position can be easily adjusted in a freely rotating state separated from the member.

1 is a schematic view of an electrophotographic color image forming apparatus according to an embodiment of the present invention. It is a schematic sectional drawing of the process unit mounted in the image forming apparatus. FIG. 3 is a perspective view showing a latent image carrier and a charging roller of a process unit mounted on the apparatus main body. FIG. 4 is a schematic side view of a mode switching unit that moves up and down a latent image carrier and a charging roller of a process unit (color mode). It is a schematic side view of the mode switching means for moving up and down the latent image carrier and the charging roller of the process unit (all rest mode). It is a schematic side view of a mode switching means for moving up and down a latent image carrier and a charging roller of a process unit (monochrome mode). It is sectional drawing of a latent image carrier. It is sectional drawing of the drive side edge part of a latent image carrier (at the time of rotational driving force transmission). It is sectional drawing of the drive side edge part of a latent image carrier (at the time of a rest). It is a perspective view of the engaging member of a latent image carrier. It is sectional drawing of the engaging member of a latent image carrier. It is sectional drawing of the drive side edge part of the latent image carrier in an apparatus main body mounting position (mounting state). It is sectional drawing of the drive side edge part of the latent image carrier in an apparatus main body mounting position (detachment | leave state). (A) is a figure explaining the phase difference of the gear of a latent image carrier. (B) is a graph showing the phase difference. (A) is a figure explaining the phase difference of the gear of a latent image carrier. (B) is a graph showing the phase difference. FIG. 3A is a cross-sectional view illustrating a state immediately after a new process unit is mounted on an image forming apparatus. (B) is a sectional view showing a state after the charging roller of the process unit is driven to rotate after the unit is mounted. 2 is a block diagram illustrating a part of an electric circuit of the image forming apparatus. FIG.

  Embodiments of a latent image carrier unit of the present invention, a process unit using the same, and an image forming apparatus will be described below with reference to the accompanying drawings. In each drawing for explaining this embodiment, constituent elements such as members and components having the same function or shape are given the same reference numerals as much as possible to distinguish them, and then the explanation will be given. Is omitted.

(Configuration of image forming apparatus)

  FIG. 1 is a schematic configuration diagram of an image forming apparatus having a process unit according to an embodiment of the present invention. This image forming apparatus can be configured in a so-called AIO (all-in-one) format as a multifunction machine in which functions of a copying machine, a printer, and a facsimile are integrated. The image forming apparatus includes four process units 1Bk, 1Y, 1M, and 1C as full-color image forming units, and a developing device as a developing unit is provided in the process unit. Of course, the present invention can also be applied to a monochrome image forming apparatus having one latent image carrier or process unit.

  In the following description, Bk, Y, M, and C next to the reference number indicate black, yellow, magenta, and cyan, and when describing a common configuration for each color, Bk, Y, M , C is omitted as appropriate, and only numbers are used. The latent image carrier 2 is described as a drum-shaped photoconductor 2.

  In this image forming apparatus, the process unit 1 having the toner bottle 6 and the latent image carrier 2 is configured to be replaceable for each unit by opening and closing the upper cover 8. A protrusion 8b is formed in the vicinity of the support shaft 8a of the upper cover 8, and when the upper cover 8 is opened and closed, the upper cover switch 18 as a cover open / close detection means is turned on / off by the protrusion 8b.

  Each process unit 1Bk, 1Y, 1M, 1C has the same configuration except that it contains toners of different colors of black, yellow, magenta, and cyan corresponding to the color separation components of the color image. Specifically, each process unit 1Bk, 1Y, 1M, and 1C includes a latent image carrier unit having a photosensitive member 2, and a charging roller as a charging unit that charges and initializes the surface of the photosensitive member 2 to a high potential. 3 is disposed. Further, a developing device 4 that forms a toner image on the photoconductor 2 and a cleaning blade 5 that cleans the surface of the photoconductor 2 are provided.

  As the constituent elements of the invention, the black process unit 1Bk is the first process unit, the color process units 1Y, 1M, and 1C are the second process units, the black photoreceptor 2Bk is the first photoreceptor, and the color photoreceptor 2Y. , 2M, 2C are second photoconductors.

  Each process unit 1Bk, 1Y, 1M, 1C is configured to be detachable integrally with the image forming apparatus main body 11. Although the process units have been described in the order of black, yellow, magenta, and cyan, they are not specified in this order, and the order is arbitrary.

  A toner bottle 6 as a developer supply unit filled with toner of each color is provided on the upper portion of the image forming apparatus main body 11. Each color toner in the toner bottle 6 is transferred to a toner storage portion of the corresponding developing device 4 via a toner supply mechanism (not shown).

  An exposure device that exposes the surface of each photoconductor 2 by an LED 7 is disposed above the photoconductor 2 in the latent image carrier unit of each process unit 1Bk, 1Y, 1M, and 1C. Light is irradiated from the exposure apparatus to each photoconductor 2, and by the irradiation (exposure), an electrostatic latent image is formed on the surface of each photoconductor 2. An image is formed.

  A transfer device 9 is disposed below each process unit 1Bk, 1Y, 1M, 1C. The transfer device 9 has an intermediate transfer belt 10 composed of an endless belt as a transfer material. The intermediate transfer belt 10 is stretched between a driving roller 12 and a tension roller 13, and the driving roller 12 rotates so that the intermediate transfer belt 10 runs in the direction of the arrow in the figure.

  Four primary transfer rollers 14 as primary transfer means are disposed at positions facing the four photoconductors 2. The primary transfer roller 14 is a conductive elastic roller, and is disposed so as to be pressed against the photoreceptor 2 from the back surface of the intermediate transfer belt 10.

  A constant current controlled bias is applied to the primary transfer roller 14 as a primary transfer bias. A primary transfer nip is formed at a location where the intermediate transfer belt 10 is sandwiched by each primary transfer roller 14 and each photoreceptor 2.

  Further, a secondary transfer roller 15 as a secondary transfer unit is in contact with the outer peripheral surface on the right side of FIG. A secondary transfer nip is formed at a position where the intermediate transfer belt 10 is sandwiched by the secondary transfer roller 15 and the driving roller 12 facing the secondary transfer roller 15.

  A power supply for secondary transfer bias is connected to the driving roller 12. The secondary transfer roller 15 is electrically grounded. By applying a voltage having the same polarity as the toner to the driving roller 12, a voltage is generated in which the toner travels from the intermediate transfer belt 10 toward the transfer paper. Thereby, the toner image can be transferred onto the transfer paper.

  The power supply connection and grounding of the drive roller 12 and the secondary transfer roller 15 may be reversed. That is, the drive roller 12 is electrically grounded, and a secondary transfer bias power source is connected to the secondary transfer roller 15. By applying a voltage having a polarity opposite to that of the toner to the secondary transfer roller 15, a voltage is generated in which the toner moves from the intermediate transfer belt 10 toward the transfer paper. Thereby, the toner image can be transferred onto the transfer paper.

  A belt cleaning blade 16 that cleans the surface of the intermediate transfer belt 10 is disposed adjacent to the driving roller 12 of the intermediate transfer belt 10. The front end portion of the belt cleaning blade 16 makes a counter contact with the intermediate transfer belt 10, and the transfer residual toner scraped off at the front end portion is collected in a waste toner storage portion 17 below the intermediate transfer belt 10. It is like that.

  Under the image forming apparatus main body 11, a paper feed tray 19 that accommodates transfer paper P as a recording medium, a paper feed roller 20 that carries the transfer paper P out of the paper feed tray 19, and the like are provided. Further, a conveyance path R for guiding the transfer paper P upward from the paper feed tray 19 is formed in the image forming apparatus main body 11.

  In the transport path R, a pair of timing rollers 21 for measuring the transport timing of the transfer paper P is disposed on the way from the position where the paper feed roller 20 is disposed to the position where the secondary transfer roller 15 is disposed. Has been. A fixing device 22 for fixing the image on the transfer paper P is disposed above the position where the secondary transfer roller 15 is disposed. Further, a pair of paper discharge rollers 24 is disposed above the fixing device 22. The paper discharge roller 24 discharges the transfer paper P after image fixing to a stock portion 23 formed by denting the upper surface of the image forming apparatus main body 11.

(Operation of image forming apparatus)
The basic operation of the image forming apparatus will be described below with reference to FIG.
When the image forming operation is started, the photosensitive members 2 of the process units 1Bk, 1Y, 1M, and 1C are driven to rotate clockwise in FIG. 1 by a driving device (not shown), and the surface of each photosensitive member 2 is charged by the charging roller 3. It is initialized by being charged with a high potential uniformly at a predetermined polarity.

  The surface of each charged photoconductor 2 is irradiated with light from an exposure device, and an electrostatic latent image composed of a low potential portion by exposure and a high potential portion by initialization is applied to the surface of each photoconductor 2. It is formed. At this time, the image information to be exposed on each photoconductor 2 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. By supplying toner to the electrostatic latent image formed on the photoreceptor 2 in this way by each developing device 4, the electrostatic latent image is visualized (visualized) as a toner image.

  The intermediate transfer belt 10 travels in the direction indicated by the arrow in the figure when the drive roller 12 that has passed the intermediate transfer belt 10 with a predetermined tension is rotationally driven. Further, a constant voltage or a constant current-controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 14. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 14 and each photoconductor 2.

  Then, the toner images of the respective colors formed on the photoconductors 2 of the process units 1Bk, 1Y, 1M, and 1C are sequentially transferred onto the intermediate transfer belt 10 by the transfer electric field formed in the primary transfer nip. The Thus, a full color toner image is carried on the surface of the intermediate transfer belt 10. When the transfer of the toner image is completed, the toner remaining on the surface of each photoreceptor 2 is removed by the cleaning blade 5.

  When the image forming operation is started, the paper feed roller 20 starts to rotate, and the transfer paper P stored in the paper feed tray 19 is sent out to the transport path R. The transfer paper P sent out to the transport path R is temporarily stopped by the timing roller 21. Thereafter, the driving of the timing roller 21 is resumed, and the transfer paper P is sent to the secondary transfer nip between the secondary transfer roller 15 and the intermediate transfer belt 10 in synchronization with the toner image on the intermediate transfer belt 10. It is done.

  Since a transfer voltage having the same polarity as the toner charging polarity of the toner image on the intermediate transfer belt 10 is applied to the driving roller 12, a transfer electric field is formed in the secondary transfer nip by the transfer voltage having the same polarity. When the transfer paper P and the toner image on the intermediate transfer belt 10 reach the secondary transfer nip, the toner image on the intermediate transfer belt 10 is transferred onto the transfer paper P by the transfer electric field formed in the secondary transfer nip. Are collectively transferred.

  The toner remaining on the intermediate transfer belt 10 after the transfer is removed by the belt cleaning blade 16. The transfer paper P onto which the toner image has been transferred is conveyed to the fixing device 22 where the toner image is fixed to the transfer paper P by being pressed and heated between the fixing roller 22a and the pressure roller 22b. Thereafter, the transfer paper P is discharged to the stock unit 23 by the paper discharge roller 24.

  The above description is the image forming operation when a full color image is formed on the transfer paper. However, a single-color image is formed using any one of the four process units 1Bk, 1Y, 1M, and 1C, and a two-color or three-color image is formed using two or three process units. It is also possible to do.

(Process unit)
FIG. 2 shows a schematic structure of the process units 1Bk, 1Y, 1M, and 1C. A toner bottle 6 is disposed at the top of the unit, and an agitator 6a and a toner supply screw 6b are disposed inside the toner bottle 6. A latent image carrier unit having a drum-shaped photoconductor 2 as a latent image carrier is disposed below the unit. The photosensitive member 2 is driven by a latent image carrier driving mechanism described later.

  Around the photosensitive member 2, a charging roller 3, an LED 7 as an exposure device, a developing device 4, and a cleaning blade 5 are disposed. Inside the developing device 4, a developing roller 4a, a supply roller 4b, and a toner supply screw 4c are disposed.

  As described above, the process unit 1 is mounted from a vertical direction at a predetermined mounting position in the apparatus main body 11 with the upper cover 8 of the image forming apparatus main body 11 opened. This mounting direction is for mounting from above on a photosensitive member driving mechanism described below. However, as long as there is a structure in which the process unit 1 is mounted at a predetermined mounting position in the apparatus main body 11 from above at the final stage, the process unit 1 can be mounted on the apparatus main body 11 from the horizontal direction or the oblique direction. is there.

(Photoconductor drive mechanism)
As shown in FIG. 3, a photoreceptor driving unit 200 is disposed in the apparatus main body 11. The photosensitive member driving unit 200 is provided with a pair of left and right contact / separation bars 28a and 28b as mode switching means for switching between three modes of color, all pauses, and monochrome described later. With the pair of contact / separation bars 28a and 28b, the photosensitive member 2 is contacted and separated in the vertical direction with respect to the mounting position of the apparatus main body 11.

 The contact / separation bars 28a and 28b are parallel to each other in the apparatus main body 11 and extend in the horizontal direction. The interval between the contact / separation bars 28 a and 28 b corresponds to the width of the process unit 1. Then, both ends of the respective support shafts 32 and 37 of the photosensitive member 2 and the charging roller 3 protruding from the casing of each process unit 1 are supported by cams 29 and 29 'described later formed on the contact / separation bars 28a and 28b. Yes.

  As shown in FIGS. 4A to 4C, four drive gears 25Bk, 25Y, 25M, and 25C having the same diameter are disposed at equal intervals in the horizontal direction at the lower position of one contact / separation bar 28a. These four drive gears 25 mesh with a driven gear portion 301 (described later) provided at one end portion of each photoconductor 2 on the drive side. The intervals between the four drive gears 25 are set to be the same as the intervals between the four photoconductors 2. The driven gear portion 301 of each photoconductor 2 is moved up and down by sliding movement of the contact / separation bars 28a and 28b, so that the driven gear portion 301 and the main body side drive gear 25 are contacted and separated.

  Between the inner two drive gears 25Y and 25M, a motor gear 26a of the photosensitive member drive motor 26 as a single rotation drive source is disposed. Further, idle gears 27a and 27b are disposed between the drive gears 25Bk and 25C on both sides and the drive gears 25M and 25Y on the inside thereof. Then, by rotating the photoconductor drive motor 26, the four drive gears 25 rotate simultaneously in the same rotation direction.

  Note that it is not always necessary to drive all four drive gears 25Bk, 25Y, 25M, and 25C with a single rotational drive source. For example, the drive gear 25Bk may be driven by a first rotation drive source, and the other drive gears 25Y, 25M, and 25C may be driven by a second rotation drive source.

  As shown in FIGS. 3 and 4A to 4C, rack teeth 53a and 53b are formed on the upper surfaces of the one end portions of the contact / separation bars 28a and 28b. The small gear portions of the two-stage drive gears 52a and 52b mesh with the rack teeth 53a and 53b.

  The large-diameter gear portions of the two-stage drive gears 52 a and 52 b mesh with the idle gears 51 a and 51 b, and one idle gear 51 a meshes with the pinion gear 50 a of the photoreceptor contact / separation drive motor 50. The other idle gear 51 b is connected to the shaft of the opposite idle gear 51 a by a connecting shaft 36. Then, by rotating the pinion gear 50a of the motor 50 clockwise in FIG. 4A, the contact / separation bars 28a, 28b are moved to the left, and by rotating counterclockwise, the contact / separation bars 28a, 28b are moved to the right. It has become.

  Cams 29 and 29 'for moving the support shaft 32 of each photoreceptor 2 and the support shaft 37 of each charging roller 3 up and down are arranged on the upper surfaces of the contact / separation bars 28a and 28b. The lower cam 29 is for the support shaft 32 of the photoreceptor 2, and the upper cam 29 ′ is for the support shaft 37 of the charging roller 3. The cam 29 for the support shaft 32 of the photosensitive member 2 has five low positions 29a, 29a, 29a, 29a, 29d and four high positions 29b, 29b, 29b, 29c. The low positions and the high positions have the same height and extend in the horizontal direction with a predetermined width. The cam 29 ′ has the same low position and high position, and the relative positional relationship between the support shaft 37 of the charging roller 3 and the support shaft 32 of the photosensitive member 2 does not change even when the contact / separation bars 28 a and 28 b slide. .

  The high position 29c on the right end is for supporting the support shaft 32 of the black photoconductor 2Bk in the rest mode, and the low position 29d on the right is the black photoconductor 2Bk in the monochrome mode (monochrome printing). The support shaft 32 is supported. That is, the support shaft 32 of the black photosensitive member 2Bk is positioned at the low position 29a in the color mode, and moves over the high position 29c and moves to the low position 29d in the monochrome mode. For this reason, the width of the high position 29 c at the right end is made shorter than the width of the high position 29 b of the other photoconductors 2.

  FIG. 5A shows a cross-sectional view of a single latent image carrier unit having the photosensitive member 2. 5B and 5C show the engaged state and the separated state of the engaging member 30d disposed at the driving side end of the photosensitive member 2. FIG.

  As shown in FIG. 5A, the photoreceptor 2 of the latent image carrier unit is formed of a hollow cylindrical member. A driving force receiving member 30 is disposed at the left end of the photoreceptor 2. A shaft holding flange 31 is bonded to the inside of the right end portion of the photosensitive member 2. The support shaft 32 of the photosensitive member is held in a penetrating state by the driving force receiving member 30 and the shaft holding flange 31. In order to prevent the support shaft 32 from coming off in the thrust direction, the support shaft 32 is engaged with the driving force receiving member 30 and the shaft holding flange 31 in a radial direction by a pin (not shown).

  As shown in FIGS. 5B and 5C, the driving force receiving member 30 includes an engaged member 30a, an engaging member 30d, and a spring 33 as an urging means disposed between the both members 30a and 30d. Has been. The engaged member 30a has a bottomed cylindrical shape and has a boss portion through which the support shaft 32 penetrates at the center. The outer peripheral surface of the engaged member 30a is fixed to the inner peripheral surface of the end portion of the photoreceptor 2 with an adhesive.

  A plurality of internal gears 30b protruding inward in the radial direction are integrally formed on the inner peripheral surface of the engaged member 30a. A tooth end portion on the outer side in the axial direction of the internal gear 30b is tapered and tapered. The boss portion of the engaged member 30a and the outer cylindrical portion are connected by a flange portion 30c. This flange portion 30c closes the interdental gap of the internal gear 30b. The flange portion 30c has a reinforcing action for the engaged member 30a, and can be used as an abutting surface of an external gear 30e of an engaging member 30d described later.

  On the other hand, as shown in FIGS. 6A and 6B, the engaging member 30d is integrally formed by a cylindrical member having a center hole. And the support shaft 32 is penetrated with a gap in the radial direction through the large-diameter center hole 30m and the small-diameter center hole 30n of the engagement member 30d.

  The support shaft 32 of the photosensitive member 2 has a distal end with a diameter at the small diameter portion 32a and the medium diameter portion 32b so that the center holes 30m and 30n do not interfere with the engagement member 30d by the axial movement of the engagement member 30d. It is formed differently. Thus, the engaging member 30d is attached to the support shaft 32 so as to be coaxial and movable in the axial direction.

  A plurality of external gears 30e protruding in the direction of the engaged member 30a are integrally formed at the axial end of the engaging member 30d. The tooth end portion on the outer side in the axial direction of the external gear 30e is tapered and can be easily inserted between the internal gears 30b from the axial direction. The effect of the easy insertion can be obtained also by tapering only the opposing tooth end portion of either the external gear 30e or the internal gear 30b.

  The internal gear 30b and the external gear 30e may have any structure that can transmit the rotational driving force to the photosensitive member 2 and can be engaged and disengaged from each other in the axial direction. It does not necessarily have to be a “gear”. For example, a spline may be used instead of the gear. However, in order to increase the accuracy of phase alignment, it is better that the number of teeth of the internal gear 30b and the external gear 30e is large. The same applies to a spline.

  A flange portion 30g is formed adjacent to the base end portion of the external gear 30e. The end of the photoreceptor 2 is closed by the flange portion 30g. Further, the interdental gap of the external gear 30e is closed by the flange portion 30g. Following the flange portion 30g, a large diameter portion 30h, a medium diameter portion 30i, a small diameter portion 30j, and a medium diameter portion 30k are sequentially formed toward the left end of the engagement member 30d.

  And the follower gear part 301 is formed in the large diameter part 30h. As will be described later with reference to FIGS. 7A and 7B, the driven gear portion 301 is exposed to the outside through a notch hole 167 a of the casing 167 of the process unit 1.

  Here, the medium diameter part 30i and the medium diameter part 30k are formed to have the same diameter, but the medium diameter part 30i may be formed slightly larger than the medium diameter part 30k. The middle-diameter portion 30k on the distal end side is rotatably fitted in the shaft support hole 167b of the casing 167 as shown in FIG. 7A in a state where the process unit 1 is mounted on the apparatus main body 11.

  As shown in FIGS. 6A and 6B, a narrow hole 34 extending in the axial direction is formed from the end face of the engagement member 30d. The hole 34 is formed at a position eccentric from the axis of the engagement member 30d. A rod-like weight 40 is fitted in the hole 34. The position of the hole 34 (the radial position from the axial center of the engaging member 30d) and the weight of the weight 40 are the same for each photoconductor 2.

  However, the positions of the hole 34 to the weight 40 with respect to the circumferential direction of the driven gear portion 301 need not be considered in particular. In other words, it is not necessary to consider the relationship between the phase of the speed fluctuation in the circumferential direction due to the engagement of the driven gear portion 301 and the drive gear 25 and the circumferential position of the weight 40 in the engaging member 30d.

  This is because the circumferential speed fluctuation due to the engagement of the driven gear portion 301 is canceled by the speed fluctuation caused by the weight 40. For this reason, it is not necessary to improve the processing accuracy of the driven gear portion 301 and the hole 34, and the engaging member 30d can be manufactured at low cost.

  7A and 7B show the photosensitive member mounting position of the image forming apparatus main body 11. FIG. 7A shows the mounted state of the photoconductor 2, and the photoconductor 2 is in contact with the intermediate transfer belt 10 in this mounted state. FIG. 7B shows the separated state of the photoreceptor 2. In this separated state, the photoreceptor 2 is separated from the intermediate transfer belt 10.

  As shown in the figure, a guide surface 41 is formed on the apparatus main body 11 so as to be adjacent to the mounting position of the photoreceptor 2. The guide surface 41 forms a part of the insertion port to the mounting position of the apparatus main body 11. The guide surface 41 includes a vertical portion 41a and an inclined portion 41b that extends further upward from the upper end of the vertical portion 41a. A mounting position of the photosensitive member 2 is provided on the right side of the vertical portion 41a.

  In the guide surface 41, a vertically long slit 41c starting from the upper end of the vertical portion 41a and extending vertically is formed continuously with the inclined portion 41b. A small-diameter portion 32a at the tip of the support shaft 32 of the photoreceptor 2 is inserted into the slit 41c so as to be movable up and down. The vertical movement of the support shaft 32 of the photosensitive member 2 is guided by the slit 41c.

  Although not shown, a vertically long slit into which the support shaft 37 of the charging roller 3 is inserted is similarly formed. The contact / separation bar 28a described above is disposed on the left side of the guide surface 41, and the small diameter portion 32a at the tip of the support shaft 32 of the photoreceptor 2 is supported by the contact / separation bar 28a when the photoreceptor 2 is mounted. It is like that.

(Operation of photoconductor drive mechanism)
The photoreceptor driving mechanism is configured as described above. As shown in FIGS. 4A to 4C, the photosensitive member driving mechanism is switched between an operating state (color mode and monochrome mode) and a non-operating state (all rest mode) by driving the photosensitive member contact / separation driving motor 50.

  FIG. 4A shows the color mode. The support shafts 32 of the four BkYMC photoreceptors 2 are supported at the low position 29a, and each photoreceptor 2 is in contact with the intermediate transfer belt 10 as a transfer material. In this state, when the photosensitive member 2 and the intermediate transfer belt 10 are driven, four color toner images are transferred to the intermediate transfer belt 10.

  FIG. 4B shows the all pause mode (all color separation mode). In this full rest mode, the contact / separation bars 28a, 28b are moved to the left by the motor 50, and the support shafts 32 of the four BkYMC photoreceptors 2 are lifted to the high positions 29b, 29b, 29b, 29c. The support shaft 37 of the charging roller 3 is similarly lifted. That is, the entire process unit 1 is lifted at a predetermined height.

 Accordingly, each photoreceptor 2 is separated from the intermediate transfer belt 10. In this state, the engaging member 30d having the driven gear portion 301 is released from the engaged member 30a of the photosensitive member 2 and becomes free to rotate, and is automatically brought to a predetermined rotational position by the rotational moment around the rotational center by the weight 40. Return.

  More specifically, as shown in FIG. 8B, when the photosensitive member 2 is separated from the mounting position and the engaging member 30d is free to rotate, the weight 40 is brought into a position directly below the support shaft 32 that is the center of rotation of the engaging member 30d by its own weight. Moving. Therefore, the phase of the rotation unevenness of each photoconductor 2 is matched, and the color shift due to the phase shift is prevented.

  8A and 8B compare the gear [1] as the driven gear portion 301 of the photoreceptors 2C and 2Y and the gear [2] as the driven gear portion 301 of the photoreceptors 2M and 2Bk for convenience. However, it goes without saying that the same phase alignment is performed by comparing the arbitrary driven gear portions 301 of the four photoconductors 2.

  The operation of the photoreceptor contact / separation drive motor 50 is controlled by the control unit 150 shown in FIG. In the present embodiment, the control unit 150 sets the all pause mode between print jobs, as conventionally performed.

 The all-pause mode may be performed in accordance with the timing of paper jam processing, parts replacement by maintenance, and the like. Since such an operation is often performed by opening the upper cover 8 of the apparatus main body 11 described above, the full sleep mode is temporarily set based on the operation of the upper cover switch 18.

  In the case of an image forming apparatus having no front cover 8 and having a front cover, the full pause mode is temporarily set based on the operation of a switch that detects the opening / closing of the front cover switch. Note that an embodiment in which the new replacement of the process unit 1 is detected by the new product detection means and the first power switch is turned on after the replacement of the new product to enter the all-pause mode will be described later with reference to FIG.

  FIG. 4C shows the monochrome mode. In the monochrome mode, the contact / separation bars 28a and 28b further move to the left, and the support shaft 32 of Bk gets over the high position 29c and moves to the low position 29d on the opposite side. The movement from the high position 29c to the low position 29d is due to the weight of the process unit 1Bk. As a result, the photoreceptor 2 </ b> Bk contacts the intermediate transfer belt 10.

  The support shafts 32 of the remaining three color (YMC) photoconductors 2Y, 2M, and 2C remain on the wide high position 29b. For this reason, the three photoconductors 2Y, 2M, and 2C are maintained in a state of being separated from the intermediate transfer belt 10. As a result, a monochrome toner image is printed in Bk single color.

 To return from the monochrome mode in FIG. 4C to the color mode, the contact / separation bars 28a and 28b are moved to the opposite side (to the right). Then, the color mode of FIG. 4A is restored via the all pause mode of FIG. 4B. At this time, the phase shift of the rotation unevenness of the photosensitive member 2 due to the free rotation of the engagement member 30d described above is suppressed even in the all pause mode.

  When shifting from the all-pause mode of FIG. 4B to the color mode of FIG. 4A, the support shaft 32 of each photoconductor 2 moves from the high position 29c, 29b of the cam 29 to the low position 29a. This movement is due to the weight of each process unit 1Bk, 1Y, 1M, 1C. Thus, in the present embodiment, the three modes can be switched by the sliding movement of the contact / separation bars 28a and 28b.

  FIG. 7A corresponds to the color mode of FIG. 4A, and shows a mounted state of the photoconductor 2. 4A, the driven gear portion 301 of the engaging member 30d of each photoconductor 2 is exposed from the notch hole 167a of the casing 167 and meshed with the drive gear 25 of the apparatus main body 11.

  The external gear 30e of the engagement member 30d is engaged with the internal gear 30b from the axial direction, and the spring 33 is compressed between the engagement member 30d and the engaged member 30a. Therefore, in the state of FIG. 7A, the engaging member 30d and the engaged member 30a are relatively unrotatable. In addition, the flange part 30c of the to-be-engaged member 30a can regulate the abutting position of the tapered tooth tip of the external gear 30e. Thereby, the engagement state of the external gear 30e and the internal gear 30b is stabilized.

  Since the engaging member 30d is in contact with the vertical portion 41a of the guide surface 41 by the urging force of the spring 33, an effect of preventing the photosensitive member 2 from rattling in the left-right direction can be obtained. In this state, the middle diameter portion 30k at the end of the engagement member 30d is rotatably fitted in the shaft support hole 167b of the casing 167. In addition, it is desirable that the vertical portion 41a of the guide surface 41 and the end surface of the engaging member 30d that contacts the vertical portion 41a be as smooth as possible so that the friction coefficient is reduced.

  When the drive gear 25 of the apparatus main body 11 is rotated by the photosensitive member driving motor 26 in the state of FIG. 7A, the rotational driving force is transmitted to the photosensitive member 2 via the engaging member 30d and the engaged member 30a. Then, the photoreceptor 2 rotates around the support shaft 32. The state of FIG. 7A is the same as that of the photoconductor 2Bk of FIG. 4C in the monochrome mode.

  FIG. 7B corresponds to the all pause mode of FIG. 4B and shows a state in which the photosensitive member 2 is separated from the mounting position. In this separated state, the engaging member 30d that has been in contact with the vertical portion 41a moves to the inclined portion 41b. A gap is formed between the engaging member 30d and the inclined portion 41b.

  The engaging member 30d is pushed outward in the axial direction while being pushed by the urging force of the spring 33. As a result, the external gear 30e of the engagement member 30d is disengaged from the internal teeth 30a of the photoreceptor 2, and the engagement member 30d is freely rotatable around the support shaft 32. Accordingly, the engaging member 30d automatically returns to a predetermined rotational position by moving the weight 40 to a position directly below the support shaft 32 by gravity acting on the weight 40.

  During this rotation return operation, the interference between the engagement member 30d and the inner support shaft 32 is avoided, and the engagement member 30d is rotated smoothly by the rotation moment caused by the weight 40. Interference between 30d and the outer shaft support hole 167b is avoided. That is, the support shaft 32 has a two-stage configuration of a small diameter portion 32a and a medium diameter portion 32b, and the gap with the center hole 30n is enlarged in the state of FIG. 7B. Further, the clearance between the shaft support hole 167b is enlarged by the small diameter portion 30j of the engagement member 30d.

  When the photoreceptor 2 is lowered from the separated position in FIG. 7B toward the mounting position in FIG. 7A, the end of the engaging member 30d is pressed in the axial direction by the inclined portion 41b. With this pressing force, the engaging member 30d approaches the engaged member 30a in the axial direction while the spring 33 is contracted.

  When the photosensitive member 2 is mounted at a predetermined mounting position, the external gear 30e of the engaging member 30d is engaged with the internal gear 30b of the engaged member 30a from the axial direction, and the rotational driving force can be transmitted. It becomes a state. At the same time, the driven gear portion 301 formed on the outer periphery of the engagement member 30d meshes with the drive gear 25 of the apparatus main body 11. The photosensitive member driving mechanism can transmit the rotational driving force to the photosensitive member 2 as described above.

  As described above, the engaging member 30d formed with the driven gear portion 301 is automatically returned to the predetermined rotational position by the weight 40 in the all-pause mode. The rotational position of the driven gear 301 of 30d is always aligned at a constant rotational position. Therefore, the phase shift of the rotation unevenness between the photoconductors 2 is suppressed, and the color shift is suppressed.

  FIG. 8A and FIG. 8B show the state of suppressing the phase shift of the rotation unevenness. FIG. 8A shows a state in which the photoconductor 2 continues to be used in a state where it is mounted at the mounting position of the apparatus main body 11, and a phase shift due to rotation unevenness has occurred.

  From this state, the contact / separation bars 28a and 28b are slid by the motor 50 as shown in FIG. Then, each photoconductor 2 moves to the separated position in FIG. 7B, and the engagement member 30d becomes free to rotate. As a result, as shown in FIG. 8B, the weight 40 of the right gear [2] whose phase of rotation unevenness is shifted relative to the left gear [1] is the same as the left gear [1]. It automatically rotates and moves to a position directly below the support shaft 32. Further, when the position of the weight 40 on the left side of the gear [1] in FIG. 8A is shifted from the position directly below the support shaft 32, the weight 40 is positioned at the position directly below the support shaft 32, similarly to the gear [2]. It rotates automatically.

  Thereby, the phase shift of the rotation unevenness of all the photoconductors 2 is suppressed. Since the phase of the rotation unevenness is aligned in each photoconductor 2, even when a positional shift with respect to the ideal position to be transferred to the intermediate transfer belt 10 occurs, the color shift between the respective colors can be suppressed.

(New detection means for process units)
Next, an embodiment will be described in which the temporary switching to the all sleep mode is performed at the timing when the process unit is replaced with a new one.

  Each process unit is manufactured in a factory so that the rotation unevenness of the photosensitive member 2 does not occur, but the rotation unevenness cannot be completely eliminated. For this reason, when one of the plurality of process units in the apparatus main body is replaced with a new process unit, a phase shift of rotation unevenness occurs between the new process unit and the remaining process units.

  Therefore, a color shift occurs during color printing due to the phase shift of the rotation unevenness. Therefore, even when the process unit is replaced with a new one, it is necessary to suppress the phase deviation of the rotation unevenness by temporarily switching to the all-pause mode described above. In order to do this, it is necessary to provide new article detecting means for detecting that the process unit is new.

  FIG. 9 shows an example of a new article detecting means for detecting that a new process unit is mounted on the image forming apparatus main body 11 by using the rotation of the rotating shaft 3a of the charging roller 3 of the process unit. is there. Here, since the process units 1Bk, 1Y, 1M, and 1C have the same detection mechanism, the reference numerals Bk, Y, M, and C are omitted.

  In FIG. 9, reference numeral 80 denotes the apparatus main body. The rotation shaft 3a of the charging roller 3 of the process unit is rotatably supported by a support plate 168 of the process unit via a bearing. A threaded pin 164 for operating the microswitch 169 is attached to the rotating shaft 3a of the charging roller 3 and protrudes from the casing 167 of the process unit.

  On the other hand, the face plate 81 of the apparatus main body 80 is formed with a large-diameter hole into which a normally closed microswitch 169 for detecting the presence or absence of a process unit is fitted. The microswitch 169 is supported by the printed circuit board 82. The inner surface of the face plate 81 is covered with an inner cover 84, and the outer surface on the printed circuit board 82 side is covered with an outer surface cover 83.

  A connecting sleeve 165 is fixed to the tip of the rotating shaft 3a. The connecting sleeve 165 rotates integrally with the rotating shaft 3a, and a hole having a square cross section (which may be a rectangle or other irregular shape) is formed at the center of the connecting sleeve 165. A square columnar leg 164b having a square cross section of the threaded pin 164 is fitted into the square hole so as to be slidable in the axial direction.

  As shown in FIG. 9A, a large-diameter male screw 164s is formed between the leading pin 164p of the threaded pin 164 and the leg portion 164b. In a new (unused) process unit, the male screw 164s is shallowly coupled to the inlet of the female screw hole of the casing 167, and the return spring 166 is compressed.

  In this state, the protruding length of the threaded pin 164 from the casing 167 is short. However, when the charging roller 3 is rotationally driven in this state, the threaded pin 164 is rotated thereby to be coupled to the female screw hole.

  When the threaded pin 164 is coupled to the casing 167 and rotates, the threaded pin 164 moves in a direction approaching the face plate 81, and the leading pin 164 p hits the switching operator of the micro switch 169. Then, immediately before the male screw 164s of the threaded pin 164 penetrates the female screw hole, the normally closed micro switch 169 is switched from on to off by the contact of the leading pin 164p.

  FIG. 9B shows a state immediately after the normally closed micro switch 169 is switched from on to off and the male screw 164s penetrates the female screw hole. As shown in the drawing, when the male screw 164s penetrates the female screw hole, the pin 164 suddenly protrudes outward by the return spring 166. As a result, the prismatic portion of the leg portion 164b of the pin 164 completely comes out of the square hole of the connecting sleeve 165, and the screwed pin 164 no longer rotates even when the charging roller 3 rotates.

  Therefore, when a process unit that has already been used is mounted on the image forming apparatus as it is, the microswitch 169 is always off. Even if a new (unused) process unit is mounted, that is, the unit is replaced, the microswitch 169 is on until the charging roller 3 is driven to rotate.

  When the power of the image forming apparatus is turned on, the micro switch 169 is turned on, and when the driving of the image forming mechanism is started, the micro switch 169 is turned off. . That is, it can be seen that the unit was replaced immediately before the power was turned on. As a result, the control unit 150 described below drives the photoconductor contact / separation drive motor 50 to temporarily switch each photoconductor 2 to the all-pause mode, thereby suppressing a phase shift of rotation unevenness due to replacement of a new process unit. can do.

FIG. 10 is a block diagram showing a part of an electric circuit of the image forming apparatus. In the figure, the bus 94 has a photosensitive member driving motor 26 as a single rotation driving source for driving the four photosensitive members 2 of the process units 1Bk, 1Y, 1M, and 1C, and three modes of color, all pause, and monochrome. In addition to the photosensitive member separation drive motor 50 as a mode switching means for switching, the following devices are connected.
Exposure unit (LED 7), paper feed tray 19, timing motor 35a, data input port 151, transfer device 9, operation display unit 152 as manual input means, optical sensor unit 136, control unit 150, new replacement detection means for process unit 1 A micro switch 169 (Bk to C) and an upper cover switch 18.

  The timing motor 35a is a drive source for the timing roller pair 35 described above. The data input port 151 receives image information sent from an external personal computer (not shown).

  The control unit 150 serving as a control unit controls the overall drive control of the image forming apparatus, and includes a CPU 150a, a RAM 150b serving as an information storage unit, a ROM 150c, and the like. The operation display unit 152 includes a touch panel, a liquid crystal panel, and a plurality of touch keys. The operation display unit 152 displays various information under the control of the control unit 150, and inputs information from the operator to the control unit 150. Or send.

  In the image forming apparatus according to the present embodiment, each photoconductor 2 is moved from the mounting position of the apparatus main body 11 as shown in FIG. By temporarily separating them, the phase of rotation unevenness between the photoconductors is matched.

  The driven gear portion 301 integrated with the photoconductor 2 at the mounting position of the apparatus main body 11 is once separated from the photoconductor 2 and phase-adjusted every time the job is completed. Even if the molding accuracy and the molding accuracy of the driven gear portion 301 of the photosensitive member 2 are somewhat poor, the effect of suppressing color misregistration can be easily obtained.

  Further, since the engagement member 30d automatically returns to the predetermined rotation position by the weight 40 every time it enters the all-pause mode, no special rotation adjustment means for adjusting the rotation of the engagement member 30d is required. Further, since the weight 40 can be fitted into the engaging member 30d, the space around the photoreceptor 2 does not increase. Therefore, it is possible to provide rotation unevenness phasing between jobs with a small size and low cost configuration.

  Further, since the engaging member 30d can be contacted and separated in the axial direction with respect to the photosensitive member 2, even when the gear portion needs to be replaced due to, for example, breakage of the driven gear portion 301, the engaging member can be quickly and easily engaged. It is possible to exchange only 30d. Therefore, there is an advantage that the repair cost is small.

  In addition, each photoconductor 2 is automatically put into a pause mode in accordance with the timing when the upper cover 8 of the apparatus main body 11 is opened and closed, or when a paper jam is processed. It can be carried out. In the paper jam processing, an external force may be applied to the process unit 1, and there is a possibility that a phase shift of the rotation unevenness of the photosensitive member 2 occurs due to a positional shift of each component due to the external force. Therefore, color misregistration can be suppressed by performing phase alignment of rotation unevenness of the photosensitive member 2 in accordance with the timing of jam processing.

In short, the effects obtained by the embodiment of the present invention are as follows.
(1) The color shift due to the phase shift of the rotation unevenness between the photoconductors can be suppressed by the free rotation of the engagement member 30d by the weight 40. This color misregistration suppression operation can be easily performed in a short time after the process unit is mounted, at the time of switching between the color mode and the monochrome mode, after the photoconductor replacement, after jam processing, and before each printing operation.

(2) Since the mechanism for suppressing the phase shift is simple in structure and saves space, the image forming apparatus can be provided in a small size and at a low cost.

(3) Even if the photoconductor gear (driven gear portion 301) is damaged, only the engaging member 30d having the driven gear portion 301 needs to be replaced, and the photoconductor itself can be used as it is, thus saving resources. I can plan. Moreover, it is possible to automatically and in a short time phase alignment of rotation unevenness between the photoconductor having the engagement member 30d replaced and another photoconductor.

(4) Since the driving force receiving member 30 of the photoconductor is constituted by the engaging member 30d and the engaged member 30a that can be easily engaged in the axial direction, the photoconductor can be easily assembled. Further, by tapering the tooth end portions of the external gear 30e of the engaging member 30d and the internal gear 30b of the engaged member 30a, re-engagement between the two members after separation is smooth, and operability is improved. A good photoreceptor driving mechanism can be provided.

(5) Conventionally, when the drive mechanism of the photosensitive member is not a coupling method but a space-saving drive gear integrated method, the waiting time by phase control is reduced by reducing the frequency of attaching and detaching the photosensitive member gear to the apparatus main body side gear. There was a need to do. For this reason, the photoconductor gear and the apparatus main body side gear are kept engaged, and switching between monochrome and color is performed by partial separation (YMC separation) on the transfer belt side. Further, due to the necessity of phase control between black and color, it is necessary to drive a plurality of gears on the apparatus body side separately for black and for color.

  In the embodiment of the present invention, there is no phase shift due to the attachment and detachment of the photoconductor gear and the apparatus main body side gear. Moreover, there is no need for phase control between black and color. Therefore, it is possible to drive a plurality of gears on the apparatus main body side with a single drive source. Switching between monochrome and color can be handled by floating the YMC photoconductor from the apparatus main body side gear. For this reason, it is possible to reduce the cost by using the single drive source and eliminating the YMC separation mechanism of the transfer belt.

  As mentioned above, although embodiment of this invention was described, this invention can be variously deformed without being limited to the said embodiment. For example, in the above-described embodiment, the center of gravity of the engaging member 30d disposed at the end of the photosensitive member 2 is decentered by the weight 40. It is also possible to decenter the center of gravity by forming.

  Further, the driving force receiving member 30 is composed of two members, that is, an engaging member 30d and an engaged member 30a sandwiching a spring 33 as an urging means, and an intermediate engaging member is interposed between both members. It is also possible to make the structure more than a member. Instead of decentering the center of gravity of the engaging member 30d with the weight 40, the center of gravity of the intermediate engaging member may be decentered with a weight or the like.

  It is also conceivable to rotate the photoconductor in the all pause mode by decentering the position of the center of gravity of the photoconductor body. However, in that case, it is necessary to remarkably increase the weight of the eccentric weight attached to the photoreceptor body. As a result, not only the photosensitive member driving energy is increased by the weight but also the photosensitive member is caused to run out of the shaft, and the rotation unevenness is increased.

  When the rotation unevenness becomes larger than a certain level, it becomes difficult to suppress color misregistration by phase alignment of the rotation unevenness. As in the embodiment of the present invention, only the engaging member 30d is freely rotated by the eccentric weight 40, so that effective phase alignment can be achieved without causing shaft shake due to the minimum weight usage.

  Further, as shown in FIGS. 7A and 7B, the latent image carrier unit can be mounted on the image forming apparatus main body as a single latent image carrier unit in addition to being incorporated in the casing 167 of the process unit 1. In this case, the latent image carrier unit includes a configuration without a casing as shown in FIG. 5A.

  Further, the engaging member 30d is not limited to the structure in which the engaging member 30d is disposed coaxially with the engaged member 30a and is engaged / disengaged with respect to the engaged member 30a in the axial direction as in the above-described embodiment. The engaging member 30d may be supported on a movable shaft that is parallel to each other on a separate axis from the engaged member 30a, and the movable shaft may be configured to approach and separate in parallel with the engaged member 30a. In this case, an external gear is provided instead of the internal gear 30b of the engaged member 30a. Then, the external gear 30e of the engagement member 30d is engaged / disengaged from the radial direction with respect to the external gear. The ratio of the number of teeth of the external gear of the engaged member 30a and the external gear 30e of the engaging member 30d may be arbitrary as long as a desired rotational driving force can be transmitted. Further, the external gear 30e of the engaging member 30d may be omitted, and the driven gear portion 301 may be engaged / disengaged from the external gear of the engaged member 30a from the radial direction. Thereby, an axial direction space can be reduced.

1Bk, 1Y, 1M, 1C: Process unit 2Bk, 2Y, 2M, 2C: Latent image carrier (photosensitive member)
3Bk, 3Y, 3M, 3C: Charging roller 3a: Rotating shaft 4Bk, 4Y, 4M, 4C: Developing device 6Bk, 6Y, 6M, 6C: Toner bottle 8: Upper cover 9: Transfer device 10: Intermediate transfer belt 11: Image forming apparatus main body 12: Drive roller 13: Tension roller 14: Primary transfer roller 15: Secondary transfer roller 16: Belt cleaning blade 17: Waste toner container 18: Upper cover switch 19: Paper feed tray 20: Paper feed Roller 21: Timing roller 22: Fixing device 22a: Fixing roller 22b: Pressure roller 23: Stock unit 24: Paper discharge roller 25Bk, 25Y, 25M, 25C: Drive gear 26: Latent image carrier drive motor 26a: Motor gear 27a, 27b: idle gear 28a, 28b: contact / separation bars 29, 29 ': cam 30: driving force receiving member 30a: engaged member 30b: Internal gear 30c: Flange portion 30d: Engagement member 30e: External gear 30g: Flange portion 30h: Large diameter portion 30i: Medium diameter portion 30j: Small diameter portion 30k: Medium diameter portion 30m, 30n: Center hole 31: Shaft holding flange 32: Photosensitive shaft 32a: Small diameter portion 32b: Medium diameter portion 33: Spring (biasing means)
34: Hole 35: Timing roller pair 35a: Timing motor 36: Connection shaft 37: Support shaft of charging roller 40: Weight 41: Guide surface 41a: Vertical portion 41b: Inclined portion 41c: Slit 50: Photoconductor contact / separation drive motor 50a : Pinion gears 51a, 51b: Idle gears 52a, 52b: Two-stage drive gears 53a, 53: Rack teeth 80: Device main body 81: Face plate 82: Printed circuit board 83: Outer cover 84: Inner cover 136: Optical sensor unit 150: Control unit 151: Data input port 152: Operation display portion 164: Pin 164b: Leg portion 164p: Lead pin 164s: Male screw 165: Connection sleeve 167: Casing 167a: Notch hole 167b: Shaft support hole 168: Support plate 169: Normally closed Microswitch 200: Photoconductor drive unit 301: Driven gear unit

Japanese Patent Laid-Open No. 2002-4087 JP 2009-063771 A

Claims (15)

A latent image carrier unit that has a latent image carrier that carries a latent image on its surface and is detachably attached to the image forming apparatus main body, the latent image carrier unit comprising:
An engaged portion provided on the latent image carrier;
It is movably attached to the latent image carrier unit, and engages with the engaged member in a relatively non-rotatable manner by movement in a predetermined direction in the latent image carrier unit, and the movement in a direction opposite to the predetermined direction An engaging member that is disengaged from the engaged member and is free to rotate with respect to the latent image carrier unit;
A driven gear portion that is integrally disposed on the engaging member and capable of transmitting a rotational driving force from the outside of the latent image carrier unit;
A latent image carrier unit comprising:   2. The latent image carrier unit according to claim 1, further comprising an urging unit that urges the engaging member in a direction to release the engaging member from the engaged portion.   When the latent image carrier unit is mounted at a predetermined mounting position of the main body of the image forming apparatus, the engagement member engages with the engaged portion against the biasing means, and the latent image carrier 3. The latent image carrier unit according to claim 2, wherein when the body unit is separated from the mounting position, the engaging member is detached from the engaged portion.   The engaging member has a center of gravity of the engaging member disposed at a position eccentric from the rotation center, and the engaging member is separated from the engaged portion by the center of gravity. 4. The latent image carrier unit according to claim 1, wherein the latent image carrier unit automatically rotates to a predetermined rotational position by freely rotating integrally with the driven gear portion by a rotational moment around a rotational center.   The engaged portion has an internal gear, and the engagement member has an external gear that can mesh with the internal gear from the rotational axis direction, and the other side of the internal gear and / or external gear 5. The latent image carrier unit according to claim 3, wherein a tooth end portion facing the gear is tapered.   The inter-dentation gap at the tooth end opposite to the mating gear of the internal gear and / or external gear is in the engaged state of the engaged portion and the engaging member, and the engaged portion 6. The latent image carrier unit according to claim 5, wherein the latent image carrier unit is closed by a flange portion integral with the engagement member or a flange portion integral with the engagement member.   A latent image carrier unit according to any one of claims 3 to 6, a charging unit for charging the latent image carrier of the latent image carrier unit, and developing a latent image on the latent image carrier with a developer. And a developer supply unit for supplying the developer to the developing unit.   8. An image forming apparatus comprising one or more process units according to claim 7, wherein each process unit is detachable from above the apparatus main body. A guide surface that is disposed on the image forming apparatus main body side and guides the engaging member toward the mounting position against the biasing unit when the process unit is mounted;
When the process unit is mounted at the mounting position, the engagement member is guided by the guide surface, and moves in the direction of the rotation axis of the latent image carrier unit against the biasing unit. The driven gear engages with the engaged portion in a relatively non-rotatable manner, and the driven gear portion of the engaging member is detachably engaged with the drive gear disposed in the apparatus main body, so that the latent image is carried from the drive gear. 9. The image forming apparatus according to claim 8, wherein a rotational driving force can be transmitted to the body.   The guide surface forms a part of an insertion port for mounting the process unit at the mounting position of the apparatus main body and is inclined in a direction to narrow the insertion port toward the mounting position. The image forming apparatus according to claim 9. A first process unit having the latent image carrier unit for black; a second process unit having the latent image carrier unit for color; and the first process unit and the second process unit are It is possible to contact and separate from the mounting position of the device body,
A color mode in which the latent image carriers of the first process unit and the second process unit abut against a transfer material at the mounting position;
An all-pause mode in which the first process unit and the second process unit are separated from the mounting position and the engaging members of the latent image carrier units of the process unit are freely rotatable;
The second process unit is separated from the mounting position, the engagement member of the latent image carrier of the second process unit is freely rotatable, and the latent image carrier of the first process unit is rotated to the mounting position. The monochrome mode that contacts the transfer material in
The image forming apparatus according to claim 8, wherein the image forming apparatus is switchable by a mode switching unit.   12. The image forming apparatus according to claim 11, wherein the image forming apparatus is a tandem type image forming apparatus, and the drive gears are disposed corresponding to the individual process units at the mounting position of the apparatus main body, and at least one drive of the drive gear is driven. A single rotation drive source is connected to the gear, and a drive gear other than the drive gear meshes with the drive gear connected to the single rotation drive source via an idle gear. Image forming apparatus.   The image according to any one of claims 9 to 12, wherein the engagement member is removable from the latent image carrier unit in a rotation axis direction in a state where the process unit is detached from the apparatus main body. Forming equipment.   When at least one process unit is replaced with a new one, a new article detecting means for detecting the new process unit is provided, and all the process units are switched to the mode based on the detection result of the new article detecting means. 13. The image forming apparatus according to claim 11 or 12, wherein the image mode is once again moved from the color mode to the all-pause mode and then returned to the color mode.   Cover opening / closing detection means for detecting opening / closing of a cover that opens / closes when the process unit is attached to / detached from the apparatus main body is disposed, and all the process units are set in the mode based on the detection result of the cover opening / closing detection means. 13. The image forming apparatus according to claim 11 or 12, wherein the switching unit temporarily shifts the color mode to the all-pause mode and then returns to the color mode again.