JP2006106133A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus equipped with a plurality of image carriers arranged side by side, and constituted in such a manner that a plurality of image carriers may be driven and rotated by one driving source and color shift can be efficiently restrained by achieving phase adjusting work after assembly. <P>SOLUTION: The image forming apparatus is equipped with a plurality of image carriers 1 being rotating bodies arranged side by side, and has a driving means for rotationally driving two or more image carriers 1 by driving a driving member 52 engaged with a gear 53 provided for each image carrier 1 by one driving source 51. The apparatus has a regulating member 55 performing regulation so as not to disengage the driving member 52 from the gear 53 in the driving means. At a predetermined time, the regulation of the regulating member 55 is released and the driving member 52 is disengaged from the gear 53. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile using an electrophotographic system or an electrostatic recording system.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, there is a color image forming apparatus called an inline method (tandem method) in which a plurality of image carriers (photosensitive drums) are arranged in a line. This is because, in the direct transfer system, the transfer material is carried and conveyed by an electrostatic transfer belt stretched by a plurality of rollers, and the four photosensitive drums arranged along the transfer material conveyance path are used for yellow transfer. A developer image (toner image) formed with magenta, cyan, and black color developers is sequentially transferred onto a transfer material, and a color image is formed by superimposing the respective colors. This configuration has become mainstream in recent years because it can perform printing at high speed.

  In the in-line method, when images on four photosensitive drums are superimposed on a transfer material, color misregistration due to speed fluctuations of the photosensitive drum is likely to occur. As a countermeasure, a method of reducing the color misregistration by adjusting the speed and the rotational phase of the drum by having independent driving sources (motors) for the four color photosensitive drums, and a plurality of photosensitive drums. Two methods are known in which the driving gear is connected to the gear and the color misregistration is reduced by means of assembling the gear.

  Compared to the former, the latter can reduce the number of motors and does not need to have a detection means or a complicated control means, and is therefore particularly suitable for a low-cost and compact image forming apparatus.

  For example, in Patent Document 1, in order to cancel the influence of the accumulated pitch error of the gears that drive the photosensitive drums, when an image is formed on each photosensitive drum, the accumulated pitch errors of the gears that drive the respective photosensitive drums. The phases at the meshing positions are configured to substantially coincide with each other.

  As described above, in the configuration in which the driving gears of a plurality of photosensitive drums are connected to each other, the gears that drive the photosensitive drums have the same configuration, and the same molding is performed, and the image accuracy of each color is adjusted. It is general that the phase relationship is fixed by assembling so that the phases of the gears at the formation position coincide, or that the phase relationship is maintained in a durable manner.

  However, in such a configuration, the optimum phase relationship between the gears actually deviates from the target due to variations in accuracy of drive components including the gears, so that the toner formed on each photosensitive drum There may be a positional shift when the images are transferred onto the intermediate transfer member or the transfer material, that is, a color shift of the color of the toner image.

  In that case, since there is no means for easily correcting the deviation, even if the optimum phase relationship is slightly shifted, the parts accuracy is tightened to satisfy the color shift standard, or the gear is removed and the phase is changed and reassembled. Or the standard of color misregistration itself had to be relaxed.

Therefore, in a configuration in which a plurality of photosensitive drums are driven by one motor, a configuration described in Patent Document 2 has been proposed as a configuration that can change the phase relationship. In Patent Document 2, since driving is switched between mono-color printing and full-color printing, the three colors of color and black can be intermittently connected via a clutch. By maintaining the connection accuracy of the clutch in mechanical durability, A method for maintaining the phase relationship between the black and the three color gears has been proposed. In this conventional example, the purpose is to maintain the phase relationship by compensating for the deterioration in durability of the clutch operation accuracy. It does not compensate for the gap. In addition, the phase relationship of the three colors remains fixed. That is, the phase relationship of gears cannot be optimally adjusted after assembly.
JP 2002-182450 A JP 2003-162119 A

  An object of the present invention is to drive two or more image carriers in an image forming apparatus provided with a plurality of image carriers by driving a drive member that meshes with a gear that is coupled to the image carrier. Another object of the present invention is to provide an image forming apparatus having a configuration capable of efficiently adjusting the phase of a gear coupled to an image carrier after assembly and capable of suppressing color misregistration efficiently.

The above object is achieved by the image forming apparatus according to the present invention. In summary, according to the present invention, a plurality of image carriers, which are rotating bodies, are provided side by side, and a drive member engaged with a gear provided coupled to the image carrier is driven by one drive source. In the image forming apparatus having a driving means for rotationally driving the image carrier described above,
In the driving means, a regulating member that regulates the engagement between the gear and the driving member so as not to come off,
In the image forming apparatus, the restriction of the restriction member can be released at a predetermined time, and the gear and the drive member can be disengaged.

  In the image forming apparatus of the present invention, a plurality of image carriers that are rotating members are provided side by side, and two or more driving members engaged with gears that are coupled to the image carrier are driven from one drive source. In the image forming apparatus having a driving unit that rotationally drives the image carrier, the driving unit has a regulating member that regulates the engagement between the gear and the driving member, and the regulation member is released at a predetermined time. The gear can be disengaged from the drive member, so that the phase relationship between multiple gears can be adjusted by rotating a predetermined gear, and the phase relationship can be easily achieved without disassembling the drive means even after the image forming apparatus is assembled. Therefore, it is possible to easily maintain the accuracy of color misregistration. Also, with the gear position of the gear in the driving means fixed, the gears can be disengaged and the phase can be adjusted by moving the axial position of the predetermined gear by a predetermined amount. Very important backlash and alignment are stable, and banding and misalignment can be avoided.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 is a longitudinal sectional view showing the overall configuration of a full-color laser beam printer 100 which is an image forming apparatus of this embodiment.

  The color image forming apparatus 100 includes four photosensitive drums 1 (1a, 1b, 1c, 1d) arranged in parallel in the vertical direction as image carriers. These photosensitive drums 1 are driven to rotate counterclockwise in the drawing by the driving means. A photosensitive device 1 (2a, 2b, 2c, and 2d) that uniformly charges the surface of the photosensitive drum 1 in order according to the rotation direction is irradiated around the photosensitive drum 1, and a laser beam is irradiated on the basis of image information. A scanner unit 3 (3a, 3b, 3c, 3d) for forming an electrostatic latent image on the body drum 1; and a developing device 4 (4a, 4b, 4c, for developing the toner image by attaching toner to the electrostatic latent image. 4d), an electrostatic transfer device 5 for transferring the toner image on the photosensitive drum 1 to the transfer material S, and a cleaning device 6 (6a, 6b, 6c) for removing residual transfer toner remaining on the surface of the photosensitive drum 1 after the transfer. , 6d) and the like.

  Here, each photosensitive drum 1 is integrally formed into a cartridge together with the charging device 2, the developing device 4, and the cleaning device 6 to form a process cartridge 7 (7a, 7b, 7c, 7d).

  Both ends of the photosensitive drum 1 are rotatably supported by a support member, and four of them are arranged in the same direction by transmitting a driving force from a driving source (motor) described later to one end. Driven by rotation.

  As the charging device 2, a contact charging type can be used. The charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 is uniformly charged by applying a charging bias voltage. .

  The scanner unit 3 is arranged in a substantially horizontal direction of the photosensitive drum 1, and image light corresponding to an image signal is rotated at a high speed by a scanner motor (not shown) by a laser diode (not shown). , 9c, 9d). The image light reflected by the polygon mirror 9 selectively exposes the uniformly charged surface of the photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d) to form an electrostatic latent image. To do.

  The developing device 4 applies developer (toner) of each color of yellow, magenta, cyan, and black to the outer periphery of the developing roller 40 that rotates in the clockwise direction as shown in FIG. Apply charge. Then, a developing bias is applied to the developing roller 40 (40a, 40b, 40c, 40d) facing the photosensitive drum 1 on which the latent image is formed by the exposure of the scanner unit 3, so that the surface of the photosensitive drum 1 is changed according to the latent image. In addition, a developer image (toner image) is formed.

  Further, an electrostatic transfer belt 11 that circulates is disposed so as to face and contact all the photosensitive drums 1. The electrostatic transfer belt 11 is supported by rollers in four directions in the vertical direction and circulates and moves so that the transfer material S is electrostatically attracted to the outer peripheral surface on the left side in the drawing so that the transfer material S comes into contact with the photosensitive drum 1. To do. As a result, the transfer material S is conveyed to the transfer position by the electrostatic transfer belt 11, and the toner image on the photosensitive drum 1 is transferred. Transfer rollers 12 (12a, 12b, 12c, 12d), which are transfer means, are arranged in parallel at positions facing the inside of the electrostatic transfer belt 11 and facing the four photosensitive drums 1. A positive charge is applied from the transfer roller 12 to the transfer material S via the electrostatic transfer belt 11, and the electric field generated by the charge causes the transfer material S in contact with the photoconductive drum 1 to be transferred onto the photoconductive drum 1. A negative toner image is transferred. The electrostatic transfer belt 11 circulates in the direction of the arrow in the figure, and the toner image is transferred while the transfer material S is conveyed from the driven roller 14a side to the drive roller 13 side.

  The paper feed unit 16 feeds and conveys the transfer material S to the image forming unit, and a plurality of transfer materials S are stored in the paper feed cassette 17. At the time of image formation, the paper feed roller 18 (half-moon roller) and the registration roller pair 19 are driven and rotated in accordance with the image forming operation to separate and feed the transfer material S in the paper feed cassette 17 one by one, and at the front end of the transfer material S , Abuts against the registration roller pair 19 and temporarily stops. After forming a loop, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized, and the sheet is fed to the electrostatic transfer belt 11 by the registration roller pair 19. .

  The fixing unit 20 fixes a plurality of color toner images transferred to the transfer material S, and includes a heating roller 21a that rotates, and a pressure roller 21b that presses and applies heat and pressure to the transfer material S. Consists of That is, the transfer material S to which the toner image on the photosensitive drum 1 is transferred is conveyed by the fixing roller pair 21a and 21b when passing through the fixing unit 20, and is given heat and pressure by the fixing roller pair 21a and 21b. . As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S to form an image formed product.

  Next, a characteristic configuration of the present invention will be described in detail.

  A feature of the present invention is that, in the above-described image forming apparatus, in the configuration of a driving unit that drives a plurality of photosensitive drums 1 with a single driving source (motor), the phase of a gear coupled to the photosensitive drum 1 is adjusted. It is possible.

  FIG. 2 shows a configuration of a rotational drive mechanism (drive means) that rotationally drives the four photosensitive drums 1 by one motor 51. This drum rotation drive mechanism is arranged between one motor 51, four drum drive gears (gears) 53 (53a, 53b, 53c, 53d), and the respective drum drive gears 53. The intermediate gear 52 (52ab, 52bc, 52cd) is used as the engaging drive member.

  Here, the photosensitive drums 1 are aligned in a line on a straight line as shown in FIG. 1, but the photosensitive drums 1a, 1b, 1c, and 1d are the same drum driving gear 53, respectively. The drum drive gears 53a, 53b, 53c, 53d are attached to the coaxial upper end.

  In this embodiment, as shown in FIG. 3, the drum drive gear 53 is integrally formed with a coupling portion 53z via a shaft portion, and the rotational drive transmitted by the gear meshing is accurately transmitted to the coupling. To be. The gear-side coupling 53 z is fitted and coupled to the drum coupling 31 attached to the shaft end of the photosensitive drum 1, whereby the rotational driving of the drum driving gear 53 is transmitted to the photosensitive drum 1.

  Each photosensitive drum 1 is rotationally driven at the same reduction ratio from the motor 51 by the intermediate gear 52, the drum drive gear 53, and the like in the configuration shown in FIG. That is, each drum drive gear 53 is engaged with the intermediate gear 52 arranged between them.

  An intermediate gear 52bc arranged at the center of the three intermediate gears 52 and engaged with the drum drive gear 53b and the drum drive gear 53c adjacent to each other among the four drum drive gears 53 is the shaft portion of the motor 51. Is engaged. Therefore, when the intermediate gear 52bc is rotated by the drive of the motor 51, the rotation is transmitted to the drum drive gears 53b and 53c, and is transmitted to the intermediate gears 52ab and 52cd engaged with each other, and then sandwiched between them. The rotation is also transmitted to the drum drive gears 53a and 53d adjacent to the drum drive gears 53b and 53c on the other side. Then, the rotational drive of the motor 51 is transmitted to all four drum drive gears 53.

  In such a configuration, the reduction ratio between the intermediate gear 52 and the drum drive gear 53 is set to an integer ratio so that the phase relationship between these gears is fixed and the same engagement is always repeated.

  At the time of assembling the drum rotation driving mechanism, the toner images transferred from the photosensitive drum 1 to the transfer material S are overlapped at the same position on the transfer material S in order to prevent the color shift caused by the position shift. The gears 53 that drive the photosensitive drums 1 are made to be the same mold-molded product and marked so that the phase can be recognized, and the phase of the accumulated pitch error between the gears matches on the image. Generally, a method of assembling in phase is adopted.

  4 (a) and 4 (b) are graphs showing the state of positional deviation with respect to each color, where the horizontal axis is the distance from the leading edge of the transfer material S, and the vertical axis is the amount of deviation from the correct position. Yes. A large period of waviness is a positional shift amount of one rotation period of the photosensitive drum, and is mainly caused by an accumulated pitch error of the drum driving gear 53. The difference between the respective position shifts is recognized as a color shift.

  The amount of positional deviation is determined by printing horizontal lines arranged at predetermined intervals in the sub-scanning direction on the transfer material S, measuring the distance from the tip of the transfer material S with an optical measuring device (not shown), Is obtained as a difference between

  As shown in FIG. 4A, if the phases of the undulations of the four colors can be ideally matched, the color deviation can be reduced, and the maximum color deviation amount is p in the figure in which the undulations of the four colors are maximized simultaneously. Here, since the four colors are shifted in the same direction at the same time, the total shift amount becomes small.

  However, in practice, the phase of the swell may be out of the target due to variations in gear accuracy and other drive component accuracy. In this case, the positional deviation is as shown in FIG. 4B. The color deviation deteriorates and the undulations do not coincide with each other. When the positional deviation is maximum, the undulation magnitude for one color is It becomes q in the figure of substantially the same size.

  If the amount of deviation from the prospective view can be corrected, the color deviation can be reduced. To that end, it is necessary to disengage the gears in the rotational drive mechanism of the rotating drum 1 described above.

  Here, referring to FIG. 5, a configuration in which the phase relationship can be adjusted by disengaging the gears even after the apparatus main body is assembled will be described.

  The drum drive gear 53 is supported by bearings 54 on both sides of the shaft and is urged by a spring 55 in a direction opposite to a stopper 62 described below.

  Incidentally, the bearing 54 of the drum driving gear 53 receives the coupling portion (FIG. 3) with the photosensitive drum 1 and the bearing 54 on one side also serves as a bearing for the photosensitive drum 1. FIG. 5A shows a state at the time of image formation, and the drum driving gear 53 is engaged with the photosensitive drum 1 by couplings 53z and 31 (FIG. 3) at the end, and transmits rotational driving. .

  5B, the coupling release member 61 provided in the axial direction of the drum drive gear 53 is moved downward in the figure, and the thick portion of the release member 61 with respect to the axial direction of the drum drive gear 53 is the drum. This shows a state in which the gear 53 is shifted to the shaft end side (left side in the figure) by entering the shaft portion of the drive gear 53 and the coupling between the gear 53 and the drum 1 is released. This is a state in which the user can replace the process cartridge 7 (FIG. 1), and the user may touch the drum drive gear 53.

  Here, in this embodiment, a stopper 62 for restricting the position where the gears 53 and 52 are engaged is installed in the axial movement region of the drum drive gear 53 so as to restrict the axial movement of the drum drive gear 53. Even if the user releases the coupling between the drum 1 and the gear 53 and touches the drum driving gear 53, the phase is maintained without disengaging the gear 53 and the intermediate gear 52 as the driving member.

  Here, the spring 55 uses a spiral spring member wound around the axis of the gear 53, and the axial position of the drum gear 53 can mesh with the intermediate gear 52 by the biasing force. It is regulated so that it does not deviate from this region to the shaft end side or the photosensitive drum 1 installation side. On the other hand, the position of the intermediate gear 52 is fixed in the present embodiment, and the range of meshing with the drum 53 is the region of the thickness portion where the teeth meshing with the gear 53 of the intermediate gear 52 are provided.

  As a result, when the photosensitive drum 1 is removed when the process cartridge 7 is replaced, or when the drum driving gear 53 is touched at any other time other than when performing some maintenance, the drum gear 53 and the intermediate gear 53 are not intended. The engagement with 52 cannot be removed.

  In this embodiment, the gears 53 and 52 are disengaged to adjust the phase relationship of the gears.

  FIG. 5C shows a state in which the engagement between the drum driving gear 53 and the intermediate gear 52 is removed by moving the stopper 62 downward in the drawing and moving the drum driving gear 53 to the left in the drawing. . If an arbitrary drum driving gear 53 is rotated in this state, the phase relationship with the gear driving other colors can be shifted.

  Then, by providing a cover member that covers the operation portion of the stopper 62 and attaching the cover member after phase adjustment, the operation of shifting the axial direction of the stopper 55 is normally impossible, and is necessary during assembly adjustment. Can only be operated at times. For example, in the configuration of FIG. 6 to be described later, an exterior cover that covers the machine side surface may be assembled only after phase adjustment.

  Further, as a restricting member for restricting the axial position of the drum drive gear 53, a component such as a stopper 55 is provided in FIG. 5. However, for example, another component such as an exterior is arranged on the left side in the drawing and it is inevitably assembled. In particular, the drum driving gear 53 may be configured to exhibit an effect of restricting the movement in the axial direction.

  Thus, like the stopper 55 in this embodiment, there is provided a member for restricting the member that normally prevents the engagement of the gear, which is the driving means of the photosensitive drum, and the shaft position of the gear is determined as necessary. It is a method that can be disengaged by simply moving the axial position of the gear to be disengaged while it is fixed, so the backlash and alignment, which are very important in gear meshing accuracy, remain fixed. The phase of a predetermined gear can be adjusted, and rotation transmission can be maintained with high accuracy.

  On the other hand, as another method, there is a method in which the intermediate gear is disengaged as a pendulum type (oscillation type), but this is not particularly suitable for maintaining the rotation transmission accuracy, particularly in the series in which the photosensitive drum is driven.

  Here, when predetermined, for example, at the time of assembly, the stopper 55 is released, the gears 53 and 52 are disengaged, and the phase of the drum driving gear 53 in the driving means of these photosensitive drums 1 is confirmed and adjusted. However, the phase confirmation and adjustment method at that time will be described with reference to FIG.

  At this time, the phase adjusting jig 70 as the adjusting means for executing the phase adjustment of the gear 53 is provided with two or more, in this case, four rotating, which can be attached to the bearing 54 of the driving means in the same manner as the photosensitive drum 1. A coupling 31a that can be attached at the same position as the position where the drum coupling 31 of the photosensitive drum 1 is attached is provided at the end of the shaft. It includes a motor 73 that rotates and a brake device 72 that is provided coaxially with the gear 74 and applies a predetermined rotational load, and an encoder 71 that is also provided coaxially with the gear 74 and detects the rotational speed. At least two rotational speeds can be simultaneously detected and compared for the four drum drive gears 53. Here, since there are four gears 74, the rotational speeds of the four gears 53 can be obtained simultaneously, but it is assumed that at least two gears 74 are provided.

  First, in the image forming apparatus main body 100 from which all the process cartridges 7 have been removed, the phase adjusting jig 70 is mounted so that the gears 74 are mounted at the positions where the photosensitive drums 1 are provided, and the respective brakes 72 are mounted. The main body side motor 51 is rotated while applying a predetermined load to the four drum driving gears 53, and the rotational speeds of the four drum driving gears 53 are measured. The rotation speed may be increased within a range in which the rotation accuracy can be maintained, and the phase adjustment time may be shortened.

  As an example of the measurement result, FIG. 7 shows two rotation speeds of black and cyan on a graph. From this, the shift amount ΔTc with respect to the ideal phase difference Tc in which the phase of the undulation of the position shift overlaps on the transfer material S (that is, the color shift becomes the smallest) is detected. Similarly, phase differences ΔTm and ΔTy are detected for magenta and yellow. Next, when the thrust regulating member 63 is released and the phase adjusting jig 70 is operated, the coupling 31a moves in the axial direction with respect to the color determined to be adjusted based on the detected phase differences ΔTc, ΔTm, ΔTy, and the drum By disengaging the drive gear 53 and the intermediate gear 52 and rotating the motor 73 in the phase adjustment jig 70 by a predetermined amount, the drum drive gear 53 is rotated to adjust the phase.

  After the adjustment, the coupling between the drum 1 and the gear 53 returns to the original position, so that the phase adjustment jig 70 is removed and the coupling release member 61 is returned to the original position.

  If this embodiment is used, it is not necessary to assemble while aligning the phase of the gear according to the mark as in the past, and the phase adjustment is assembled as in the past, and only the adjustment work that exceeds the standard of color misalignment or rotational accuracy is performed. By doing so, the adjustment time can be minimized.

Example 2
In the present embodiment, the configuration for restricting or removing the engagement between the gear fitted to the photosensitive drum and the driving member described in Embodiment 1 with reference to FIG. 5 is changed. Is the same as in Example 1.

  FIG. 8 shows a configuration for disengaging the gear 53 in this embodiment.

  The intermediate gear 52 is biased in the axial direction by a spring 64 wound around the shaft of the intermediate gear 52, and the axial position is determined by a thrust restricting member 63 that is coaxial. FIG. 8A shows the time of image formation, and FIG. 8B shows the time of releasing the drum coupling in which the coupling release member 61 is moved downward in the drawing. That is, in addition to the restriction of the axial position by the stopper 55 of the drum driving gear 53 described in the first embodiment, here, the axial position of the intermediate gear 52 is determined by the spring 64 and the thrust restricting member 63 as restricting members. regulate.

  As shown in FIG. 8C, when the thrust restricting member 63 provided on the shaft portion of the intermediate gear 52 is moved downward in the figure, the thick portion of the thrust restricting member 63 enters the shaft of the intermediate gear 52. Then, the intermediate gear 52 moves to the right side in the drawing, disengagement from the drum drive gear 53, and the phase relationship can be adjusted.

  This configuration has an advantage that the space in the axial direction can be easily reduced as compared with the configuration of FIG. 5 because not only the drum drive gear 53 but also the position of the intermediate gear 52 is shifted within the regulation range. Further, it is not necessary to release the restriction of the drum driving gear 53 fitted to the photosensitive drum 1 during the phase adjustment, and the positional accuracy is improved.

  The spring 64 is not restricted to move the axial position from the restricted range unless the thrust restricting member 63 is moved, and can be operated only when necessary, such as during assembly adjustment.

  Note that the phase confirmation and adjustment method in the driving means of the photosensitive drum 1 at the time of assembly is the same as the method described in the first embodiment.

  Here too, a member member is usually provided to restrict the meshing of the gear, which is the driving means of the photosensitive drum, so that when necessary, the axial position of the gear to be disengaged with the gear shaft position fixed. Because it is a method that can disengage just by moving, backlash and alignment, which are very important in gear meshing accuracy, remain fixed. The phase of a predetermined gear can be adjusted, and rotation transmission can be maintained with high accuracy.

Example 3
In this embodiment, the configuration of the driving means for the photosensitive drum 2 is engaged with the drum driving gear 53 instead of the intermediate gear 52 in the first embodiment as shown in FIG. 9A, and the driving of the motor 63 is transmitted. A worm 66 is used as the driving member. Here, similarly to the configuration of the first embodiment, the configuration of the rotational drive mechanism that rotationally drives the four photosensitive drums 1 with one motor is used, but the drum driving gear 53 of the four photosensitive drums 1 is replaced with the worm 66. Drive using. The coupling method between the drum driving gear 53 and the photosensitive drum 1, the configuration of the image forming apparatus, and the phase adjusting means for the gear 53 are the same as those in the first embodiment.

  FIG. 9B shows a state in which the drum driving gear 53 and the worm 66 are engaged with each other. FIG. 9C shows that the stopper 62 is removed and the drum driving gear 53 is moved to remove the engagement with the worm 66. Shows the state.

  In this case as well, a member for restricting the engagement of the gear, which is usually the driving means of the photosensitive drum, is provided, and when necessary, the axial position of the gear to be disengaged is kept while the gear shaft position is fixed. Because it is a method that can disengage only by moving it, it is possible to adjust the phase of a predetermined gear while maintaining the backlash and alignment, which are very important in gear meshing accuracy, and can maintain the transmission of rotation with high accuracy. .

Example 4
Regarding the driving means for the photosensitive drum 1, in the first to third embodiments, the phase adjustment of the drum driving gear 53 is performed by attaching the phase adjusting jig 70 from the outside. Even if the phase relationship is optimally adjusted, the phase relationship may deviate from the optimum value even if the gears are replaced for some reason after shipment, even if the gears are marked and assembled in phase. is there. With respect to this problem, a configuration that enables phase adjustment on the image forming apparatus main body side will be described.

  First, a predetermined image pattern for detecting the amount of color misregistration is formed on the photosensitive drum 1 as a toner image by the image forming process by the image forming unit described in Embodiment 1 with reference to FIG. Transfer is performed on a transfer material conveyance belt 11 which is a moving body. If the image forming apparatus adopts an intermediate transfer method, the image is transferred to an intermediate transfer member.

  As can be seen from FIG. 10 showing the positional relationship between the transfer material conveyance belt 11 and the photosensitive drum 1 driving means, a detection unit 80 serving as a color deviation detection means is provided at a position facing the transfer material conveyance belt 11. Yes, the image pattern of the transfer material conveyance belt 11 is optically detected, and the detection result is transmitted to the calculation unit 80a provided in the image forming apparatus control unit (not shown), and from the relative relationship of the positional deviation of each color, The amount of phase adjustment required for each drum drive gear 53 can be calculated. The calculation result of the necessary amount of phase adjustment is transmitted to the phase adjustment motor control unit 80b and the drum drive motor control unit 80c.

  Also in this embodiment, a mechanism for moving the drum drive gear 53 in the axial direction within the restriction range of the stopper 55 by the method described in the first or second embodiment is adopted. Although the restriction of the drive gear 53 is released, in this embodiment, the movement adjusting motor control unit 80b and the drum drive motor control unit 80c are provided as means for adjusting the phase of the drum drive gear 53 in the image forming apparatus main body 100. In accordance with the necessary amount of phase adjustment transmitted, adjustment means for adjusting the phase relationship by controlling the driving of the drum drive motor 51 and the phase adjustment motor 81 is provided, and the phase is adjusted based on the necessary amount of phase adjustment. .

  FIG. 11 shows a specific component configuration for moving the axial position of the drum driving gear 53 to disengage the gears 53 and 52 in this embodiment.

  The drum drive gear 53 is biased in the direction of the release member 87 by a spring 55 on its axis. The bearing 86 is fixed to the main body of the apparatus or the frame of the driving means, and supports the drum drive gear 53 at the inner periphery of the bearing, while the release member 87 is slidably supported at the outer periphery of the bearing and is provided on the same outer periphery. The rib 86a fits into the groove of the release member 87 and restricts rotation. The release cam 84 provided between the release member 87 and the bearing 86 is rotationally controlled by a gear provided on the outer periphery, and the cam surface provided on the end surface comes into contact with the protrusion of the release member 87 to move the drum drive. The axial position of the gear 53 is controlled.

  A typical state is shown using FIG. FIG. 12 shows release cams 84 (84a, 84b, 84c, 84d) corresponding to the driving means 53 of the four photosensitive drums 1 arranged in parallel. An inter-cam gear 85 is disposed between the release cams 84 so as to mesh with the release cams 84, and the four release cams 84 are integrally rotated.

  In FIG. 12, the cam surface of the release cam 84 has a surface that is raised by one step from a surface that is raised by one step of the cam surface indicated by the hatched portion. This cam shape is arranged point-symmetrically with respect to the rotation center, and enables stable operation. Further, the protrusions of the release member 87 that abut on this are arranged point-symmetrically with respect to the center of rotation at the position indicated by the solid line in the vertical direction in the figure.

  FIG. 12A shows the time of image formation. Since the lowermost surface of the cam is opposed to the protrusion of the release member 87 and the release member 87 does not move the axial position of the drum drive gear 53, the drum drive gear 53 is shown. Meshes with the intermediate gear 52 and the coupling is also engaged.

  FIG. 12B shows a state in which the release cam 84 is rotated by one step by the phase adjusting motor 81 and all the release members 87 are moved by one step to disengage the coupling. Used when replacing the process cartridge 7. Even at this position, the gears do not disengage, so the phase relationship is fixed.

  FIG. 12C shows the case where the release cam 84 is further rotated by one step. Only the cyan release cam 84c and the release cam 84c are moved to disengage the cyan drum drive gear 53c and the intermediate gear 52. it can. When the drum drive motor 51 is rotated by a predetermined amount in this state, the drum drive gears other than cyan rotate, so that the phase relationship can be adjusted. Other colors can be similarly adjusted.

  Which of the states shown in FIGS. 12A, 12B, and 12C is determined is determined according to the amount of color shift detected from the image pattern described above, and the drum drive motor control means 80c. These states are changed by the adjusting means which is the phase adjusting motor control 80b.

  As described above, as in this embodiment, a predetermined image pattern is formed on an endless belt that is a moving body, and this is read by a color misregistration detecting means provided in the main body to detect color misregistration or positional misalignment. In addition, by having means for adjusting the phase relationship between the gears of the photosensitive drum driving means and the driving members based on this detection information, predetermined timing considering durable changes, replacement of parts, process cartridge At the time of replacement, the phase can be automatically adjusted only by the image forming apparatus main body, and the accuracy of color misregistration can be maintained.

Example 5
Regarding the adjustment of the phase of the drum drive gear 53, a configuration that can be practically handled in the market by manual adjustment without using the automatic adjustment means by the apparatus main body in the fourth embodiment will be described.

  In this embodiment, an image pattern in which color misregistration is easily detected is stored in a control unit (not shown) of the apparatus main body, and this is processed by a signal in the image forming apparatus shown in FIG. Transmission to a driving unit of a certain scanner unit 3 and printing on the transfer material S by the image forming method described in the first embodiment facilitates manual phase adjustment by a service person or the like.

  For example, if two halftones (intermediate colors) or horizontal lines (lines in the main scanning direction) are printed on the entire surface as this image pattern, the color shift can be easily recognized as a change in color. In FIG. 13, as an example, one page of the transfer material S is obtained by superimposing yellow, magenta, and cyan on black, yellow and magenta (that is, red), magenta and cyan (that is, blue), An image in which six patterns in which cyan and yellow (that is, green) are overlaid is arranged in a band shape in the sub-scanning direction is shown.

  As an actual adjustment operation, first, a default image (before adjustment) is printed, and the level of color misregistration is grasped. Next, the regulating member such as the stopper 55 shown in FIG. 5 is released, and the drum driving gear 53 of the color whose color misalignment is to be corrected is shifted by a predetermined angle. The image is output again and the color shift is confirmed. Naturally, when it gets worse, the phase is shifted in the opposite direction.

  Normally, the amount of phase adjustment does not require an extreme amount of adjustment, and is approximately ± 90 ° or less. Also, even when replacing the gears in the drive means, if the gears are marked with the same mold as in the prior art, and the phase is assembled, a large adjustment amount is not necessary. Can be combined.

  In this way, an image pattern that can detect the state of color misregistration is stored in the main body, and an image can be formed on a transfer material by a predetermined operation, thereby adding complicated configuration and control to the image forming apparatus. In addition, when a service person or the like adjusts the color misregistration, the adjustment operation can be performed relatively easily.

Example 6
In this embodiment, as shown in FIG. 14, the photosensitive drum 1d on which a black toner image is formed is driven by two different motors 51b and 51a with respect to the other three-color photosensitive drums 1a to 1c. Can be switched between full color and mono color efficiently. However, it is impossible to fix the phase between the two gear trains by meshing the gears.

  For this problem, means 91a and 91b for detecting the phase of the black drum driving gear 53d and one of the three colors of the drum driving gear 53 are provided, and the phase data stored in the nonvolatile ROM. As compared with the above, the phase relationship can be adjusted using the control of the motors 51a and 51b. As the phase data used at that time, it is desirable to use the optimum phase data detected by the method described in the fourth or fifth embodiment in a nonvolatile ROM.

  In this way, in the configuration in which the four image carriers are driven by the two motors, it has means for detecting the phase of the gear driven by each motor, and the rotation of each motor is controlled based on the detected phase. However, if the phase relationship of the gears is adjusted, the optimum phase relationship can be maintained even when a configuration in which mechanical phase guarantee by gear meshing cannot be obtained is combined.

  In this embodiment, two or more motors are used, but at least one of them is used to drive two or more image carriers. Further, the distribution of the image carrier driven by each motor may be another distribution, and the configuration of black corresponding to one motor is not necessary.

  Although the image carrier driving means in the image forming apparatus shown in FIG. 1 has been described over the first to sixth embodiments, the image forming apparatus has a plurality of image carriers. If there is, there is no particular limitation. An intermediate transfer member may be provided instead of the transfer material transport member, and the toner image may be transferred onto the transfer material S after being primarily transferred onto the intermediate transfer member.

  In addition, the dimensions, materials, shapes, and relative positions of the components of the image forming apparatus described above are not intended to limit the scope of the present invention to those unless otherwise specified. Absent.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. It is sectional drawing which shows an example of the image carrier drive means based on this invention. It is a perspective view which shows an example of the components structure of the image carrier drive means which concerns on this invention. 6 is a graph showing a change in a positional shift amount in a moving direction of a transfer material in the image forming apparatus. It is explanatory drawing which shows the mode of the position control by the gear control means in an example of the image carrier drive means which concerns on this invention. FIG. 6 is a perspective view showing an example of a gear phase relationship adjusting unit in the image carrier driving unit according to the present invention. 3 is a graph showing the rotation speed of the image carrier according to the present invention. It is explanatory drawing which shows the mode of the position control by the gear control means in the other example of the image carrier drive means which concerns on this invention. It is sectional drawing which shows the other example of the image carrier drive means based on this invention. It is a schematic block diagram which shows the other example of the adjustment means of the phase relationship of the gearwheel in the image carrier drive means which concerns on this invention. It is a perspective view which shows the other example of a component structure of the image carrier drive means which concerns on this invention. It is explanatory drawing which shows the mode of the position control by the gear control means in the other example of the image carrier drive means which concerns on this invention. It is explanatory drawing which shows an example of the transfer material on which the image pattern which concerns on this invention was printed. It is a schematic block diagram which shows the other example of the image carrier drive means based on this invention.

Explanation of symbols

1 Photosensitive drum (image carrier)
11 Transfer material transport belt (moving body)
12 Transfer roller (transfer means)
51 Motor (drive source)
52 Intermediate gear (drive member)
53 Drum Drive Gear (Gear)
54 Bearing 55 Stopper (Regulator)
64 Spring (Regulator)
65 Thrust direction regulating member (regulating member)
80 Color shift detection means 81 Phase adjustment motor (adjustment means)

Claims (6)

Two or more image carriers are rotated by driving a driving member that meshes with a gear provided in combination with the image carrier by a plurality of image carriers that are rotating bodies. In an image forming apparatus having a driving unit for driving,
In the driving means, a regulating member that regulates the engagement between the gear and the driving member so as not to come off,
The image forming apparatus according to claim 1, wherein the restriction of the restriction member can be released at a predetermined time to disengage the gear and the drive member.   The engagement between the gear and the driving member can be removed by moving the axial position while the axial position of the gear or the driving member in the driving means is fixed at the predetermined time. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 1, wherein the predetermined time is a time when the phase relationship of the gears is adjusted. Image forming means for forming developer images on the surfaces of the plurality of image carriers, a moving body that moves to face the plurality of image carriers, and the developer image transferred from the image carrier to the moving body Transfer means, and color misregistration detection means for detecting color misregistration of the developer image transferred onto the movable body,
As the developer image, a predetermined image pattern is formed on the image carrier and transferred to the moving body, and the color shift of the transferred predetermined image pattern is read by the color shift detection unit. Adjustment means for detecting a positional shift of the developer image transferred from the plurality of image carriers to the moving body on the moving body and adjusting a phase relationship of the gears based on the positional shift detection information. The image forming apparatus according to claim 3, further comprising:   An image pattern that allows visual detection of the color misregistration state is formed on the image carrier, the image pattern is transferred to a transfer material, and the color misregistration state detected by the image pattern on the transfer material 4. The image forming apparatus according to claim 3, wherein the phase relationship of the gears is adjusted.   There are two or more drive sources, and at least one of the drive sources drives two or more image carriers by one, and each image carrier driven by each of the drive sources. And means for detecting the phase of the gears, controlling each of the drive sources based on the detected phase of the gears, and adjusting the phase relationship of the gears. The image forming apparatus according to claim 3.

Images