JP2006251572A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus in which high image quality is achieved without making the apparatus complex, large, and high in cost. <P>SOLUTION: A distance in a rotary shaft direction between the rotary shaft of a developing means for each color and the rotation shaft of a corresponding drive means is altered using a cam mechanism and thus image formation is made efficient. Developing units 110, 120, 210 and 220 are moved by development switching mechanisms 114, 124, 214 and 224 respectively. Thereby, developing rollers 111 and 211 for cyan and yellow respectively are moved to developing positions opposite to photoreceptor drums 101 and 201 respectively, and develop images as toner images. The toner images are primarily transferred onto an intermediate transfer belt 105 rotating in contact with the photoreceptor drums 101 and 201. This primary transfer step is also carried out for magenta and black in order. Thereafter, the toner images in four colors are superposed one onto another on the intermediate transfer belt 105. These toner image in the four colors are secondarily transferred all at once by a secondary transfer member 106. Thus, a full color image is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to an image forming apparatus having a plurality of developing units that store developers of different colors.

  Conventionally, copying machines, facsimile machines, printers and the like have been put into practical use in many fields. Among them, as an image forming apparatus for transferring and outputting a multi-color image formed on an intermediate transfer member to a recording material, a plurality of image forming units in which a latent image forming unit and a plurality of developing units are arranged around an image carrier. It is known that a visible image formed by each image forming unit is sequentially transferred onto a single intermediate transfer member. An apparatus for obtaining a multi-color image in this way is presented in Patent Document 1, Patent Document 2, and Patent Document 4.

  In the case of forming a full-color image of four colors, in a method using a single image carrier and intermediate transfer member, it is necessary to dispose four developing means around the image carrier, and the intermediate transfer member 4 Need to rotate. On the other hand, in the conventional image forming apparatus, there are two developing means arranged around the image carrier, and a full color image can be formed by rotating the intermediate transfer member twice. For this reason, it is possible to reduce the size / diameter of the image carrier and speed up the apparatus. The basic operation of this method is described in detail in paragraphs 0016 to 0031 of Patent Document 1.

  In Patent Document 2 and Patent Document 4, two developing rollers are disposed in the developing unit so as to be rotatable around an axis parallel to the rotation axis of the photosensitive drum. In the image forming apparatus, the developing unit is supported by the image forming unit so that the developing unit can be rotated about a rotating shaft substantially parallel to the rotating shaft of the photosensitive drum, and the developing unit is rotated a predetermined time with respect to the image forming unit. The image forming apparatus includes a developing function switching unit that rotates by a moving angle and switches a distance between one of the two developing rollers and the photosensitive drum to a developing state position. In these documents, by rotating the developing unit, the distance between the photosensitive member and the developing roller (developing gap) can be switched, and at the same time, the driving force transmission state of the driving gear and the developing roller gear can be switched. For this reason, it is said that reliable development function switching can be realized with small size and low cost.

  Japanese Patent Application Laid-Open No. 2005-228688 proposes a configuration for disabling the two developing rollers of the image forming unit on the side not including the Bk color developing roller when outputting a black and white image. In this document, it is possible to prevent the wear and deterioration of the photoreceptor film due to unnecessary developer contact, and the wear and deterioration of the developer due to unnecessary agitation, and lower the running cost by extending the life of the photoreceptor and developer. In addition, an image forming apparatus capable of reducing the environmental load can be realized.

In Japanese Patent Application No. 2003-104614 relating to the prior application of the applicant, a drive transmission gear for rotationally driving the developing roller is provided coaxially with respect to the photosensitive drum rotating shaft. For this reason, by maintaining only the distance between the developing roller rotating shaft and the photosensitive drum rotating shaft with high accuracy, the positional relationship between the photosensitive drum rotating shaft and the drive transmission gear rotating shaft with respect to the developing roller rotating shaft is highly accurate. In other words, high-quality image output and stable development roller driving can be realized. Furthermore, this prior application shows a configuration in which the drive transmission gear is provided coaxially with the photosensitive drum, thereby realizing high image quality and stable driving of the developing roller.
Japanese Patent Laid-Open No. 10-177286 JP 2003-167410 A JP 2003-208011 A JP 2003-307903 A JP 2004-37872 A

  However, the two developing rollers as described above are disposed in the developing unit so as to be rotatable around an axis parallel to the rotation axis of the photosensitive drum, and the developing unit is rotated substantially parallel to the rotation axis of the photosensitive drum. An image forming unit is supported so as to be rotatable about an axis, and the developing unit is rotated by a predetermined rotation angle with respect to the image forming unit, so that one of the two developing rollers and the photosensitive member are rotated. The image forming apparatus having the developing function switching means for switching the distance from the drum to the development state position has the following problems.

  The parallelisms of the rotation center axis of the two developing rollers and the photosensitive drum and the rotation center axis of the image forming unit are determined by the component accuracy, and in particular, there are many between the two developing rollers and the photosensitive drum. Intervening parts. For this reason, it is difficult to ensure parallelism with parts accuracy, and there is a problem that the development gap cannot be defined with high precision. For this reason, in Patent Document 4 described above, an adjustment mechanism is provided on the cam member that contacts both side plates of the image forming unit, and the rotation angle in the development switching operation can be arbitrarily adjusted by both side plates of the image forming unit. Absorbing the parallelism deviation between the roller and the photosensitive drum. However, the addition of the adjusting mechanism increases the size and cost of the apparatus, and there is a limit to the parallelism shift that can be absorbed by adjusting the cam member. This is an obstacle to cost reduction. In addition, when the driving force from the drive transmission gear acts on the developing roller and the rigidity of the developing unit housing that supports the developing roller is insufficient, the parallelism between the photosensitive drum and the developing roller is shifted due to the driving force, and the developing gap is increased. It will fluctuate. It is difficult to prevent this by increasing the rigidity of the developing unit housing, and the significant increase in rigidity of the developing unit housing is a major obstacle to cost reduction.

Japanese Patent Application Laid-Open No. 2005-228561 discloses a configuration in which both of the two developing rollers in the image forming unit can be brought into a non-operating state. In this configuration, by providing a developing unit rotation position where both developing rollers are in a non-developing state, when one developing roller is in the developing state, the other developing roller is separated from the photoreceptor more than necessary. Become. For this reason, an increase in the size of the apparatus and a long development state switching time are inevitable.
Further, in the above-mentioned prior application by the applicant, the developing roller is not driven in the same manner as the developing gap fluctuates due to the influence of the parallelism deviation between the photosensitive drum and the developing roller due to the driving force as described above. It becomes stable. This is a major obstacle to improving the reliability of the development drive and drive switching operation.

  As a configuration for solving the above problems, a configuration as in Patent Document 3 is conceivable. In the present invention, the developing units disposed around the photosensitive drum and urged toward the photosensitive drum are rotatably provided on both sides of the photosensitive drum independently of the photosensitive drum, and at least one is provided on the outer peripheral surface. The shaft of the developing roller is supported so as to be in contact with the cam surface of the cam member in which the above grooves are formed. For this reason, the parallelism between the photosensitive drum and the developing roller is almost defined by the accuracy of the cam member parts, and it is possible to maintain a high developing gap and minimize the impact when the developing roller contacts the photosensitive drum. It can be suppressed to.

  Here, the developing unit is urged toward the photosensitive drum, and the parallelism between the photosensitive drum and the developing roller and the developing gap are defined by the shaft of the developing roller being in contact with the cam member. However, since the developing roller is driven to rotate, it is necessary to bring the shaft of the developing roller into contact with the cam member with a sufficient urging force so that the parallelism between the developing roller and the photosensitive drum does not occur due to the driving force. For this reason, it is necessary to ensure high rigidity of the developing unit housing so that deformation does not occur even when a sufficient urging force is applied, resulting in an increase in the cost of parts. Further, the rotation of the cam member for switching the development must generate a force that is against a sufficient urging force. For this reason, there is a problem that large power consumption is required or high-speed switching becomes difficult.

  The present invention has been made in view of the above problems, and a visible image formed on an image carrier by a plurality of developing units is sequentially transferred onto an intermediate transfer member, and a multicolor image is formed on the intermediate transfer member. In the image forming apparatus that forms the image, the development means in the development state is positioned with respect to the image carrier with high accuracy without causing the apparatus to be complicated, large, and high in cost. Is possible. Along with this, an object is to realize an image forming apparatus capable of reliably transmitting a driving force from a driving unit to a developing unit and capable of performing a stable developing operation.

  The image forming apparatus according to the first aspect of the present invention provides one developing unit that visualizes a latent image of the same rotating image carrier in an arbitrary color and a visible image in a color different from the arbitrary color. When the color is switched in the image forming unit having a configuration in which the other developing unit is arranged so as to face and adjoin the outer periphery of the image carrier, one of the developing units is rotated during the rotation of the image carrier. The developing function is switched from the developing means to the other developing means, and the visible image on the image carrier obtained by making the visible image is sequentially transferred to the intermediate transfer member, and the transferred image on the intermediate transfer member is further recorded. In an image forming apparatus that obtains a recorded image by transferring to a material, a supporting unit that supports each of one developing unit and the other developing unit so as to be movable at least in the direction of approaching and separating from the image carrier, and the developing unit Urging means for urging the one side of the movable direction; It provided for restricting the movable direction movement of the developing unit by the urging force of the urging means at all times. At the same time, by rotating, the distance between the one developing means and the image carrier is in the developing state, and the distance between the other developing means and the image carrier is in the non-developing state, and the other developing means and the image. A cam member having a cam surface for changing the distance between each developing means and the image carrier at a position where the distance between the carrier is in a developed state and the distance between one developing means and the image carrier is in a non-developed state; Provided at both ends in the rotation axis direction on an axis parallel to the rotation axis of the image carrier, and one developing means and the other developing means are supported rotatably about an axis parallel to the rotation axis of the image carrier. . Further, a driving means for rotating each developing means is provided, and a driving force is connected to each of the rotating shafts of the developing means and the rotating shaft of the driving means coaxially to transmit the rotational driving force of the driving means to the developing means. In addition to providing the transmission means, the drive force transmission means moves the rotation shaft of the developing means and the rotation shaft of the drive means by a specified distance in the rotation axis direction. As a result, the driving force transmission state is released, and the rotation shaft of the developing means can move between the position where the developing means is in the developing state and the position where the developing means is not developed with the rotation of the cam member. At least one of the cam members provided at both ends in the rotation axis direction of the image carrier is rotated so that the distance between one developing means and the image carrier is in a developed state. And the distance between the other developing means and the image carrier is not developed, and the driving force transmitting means connected to the rotating shaft of one developing means and the rotating shaft of the driving means is in the driving force transmitting state, and the other A position where the driving force transmitting means connected to the rotating shaft of the developing means and the rotating shaft of the driving means is in a driving force transmission release state, and the distance between the other developing means and the image carrier is in the developing state, and Developing means and image carrier Interval is a non-developing state. The driving force transmitting means connected to the rotating shaft of the other developing means and the rotating shaft of the driving means is in a driving force transmitting state, and the driving force connected to the rotating shaft of one developing means and the rotating shaft of the driving means. A cam surface for changing the distance in the rotation axis direction between the rotation shaft of each developing unit and the rotation shaft of the driving unit can be integrally formed at a position where the transmission unit is in a driving force transmission release state.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cam member in which the two cam surfaces are integrally formed transmits the driving force between the rotating shaft of one developing means and the rotating shaft of the driving means. After the device starts and ends the operation of changing from the driving force transmission state to the driving force transmission release state, the operation of changing the interval between the one developing device and the image carrier from the developing state to the non-developing state is started. After the operation of changing the distance between the other developing means and the image carrier from the non-developing state to the developing state is finished, the driving force transmitting means of the rotating shaft of the other developing means and the rotating shaft of the driving means are released. The operation to change from the state to the driving force transmission state starts and ends. At the same time, after the driving force transmitting means between the rotating shaft of the other developing means and the rotating shaft of the driving means starts and ends the operation of changing from the driving force transmitting state to the driving force transmitting released state, the other developing means and image After the operation of changing the interval between the carrier from the development state to the non-development state and the operation of changing the interval between the one development unit and the image carrier from the non-development state to the development state is completed, The drive force transmission means between the rotation shaft and the rotation shaft of the drive means starts and ends the operation of changing from the drive force transmission release state to the drive force transmission state.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the cam members provided at both ends in the rotation axis direction of the image carrier are coaxial with the rotation axis of the image carrier. It is characterized by being provided so as to be freely rotatable.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the cam members provided at both ends in the rotation axis direction of the image carrier are provided with one developing means and the image carrier. A position where the distance between the other developing means and the image bearing member is in a non-developing state, and a distance between the other developing means and the image bearing member is in the developing state, and one developing means and the image In addition to the position where the distance between the carrier is in the non-development state, the distance between one developing means and the image carrier is in the non-development state, and the distance between the other development means and the image carrier is in the non-development state. A cam surface is provided for changing the interval between each developing means and the image carrier. At the same time, in the cam member in which the two cam surfaces are integrally formed, the distance between one developing means and the image carrier is in the developed state, and the distance between the other developing means and the image carrier is in the non-developed state. The driving force transmitting means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling position. , And the distance between the other developing means and the image carrier is in the developed state, and the distance between the one developing means and the image carrier is in the non-developed state. Further, the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling state. In addition to the position, the distance between one developing means and the image carrier is not developed, and the distance between the other developing means and the image carrier is not developed. The driving force transmission means of the shaft is in a driving force transmission release state, and each developing means rotation shaft and the drive are driven to a position where the driving force transmission means of the other developing means rotation shaft and the driving means rotation shaft is in a driving force transmission release state. It is characterized by having a cam surface for changing the distance in the rotation axis direction of the means rotation shaft.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the cam members provided at both ends of the image bearing member rotating shaft are rotated by one of the developing means and the image bearing member. The distance between the other developing means and the image carrier is in the non-development position, and the distance between the other developing means and the image carrier is in the developed state, and the one developing means and the image carrier are in the developed state. Between the positions where the interval between the developing bodies is in the non-developing state, the interval between the one developing means and the image carrier is in the non-developing state, and the positions where the spacing between the other developing means and the image carrier is in the non-developing state. Have. At the same time, in the cam member in which the two cam surfaces are integrally formed, the rotation of the cam member causes the interval between one developing means and the image carrier to be in the developed state, and the interval between the other developing means and the image carrier. Is in a non-developing state, the driving force transmitting means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is driven. The position where the force transmission is released and the distance between the other developing means and the image carrier are in the developing state, and the distance between the one developing means and the image carrier is in the non-developing state. Further, the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling state. Between the positions, the distance between one developing means and the image carrier is in a non-development state, and the distance between the other developing means and the image carrier is in a non-development state. The driving force transmitting means of the rotating shaft is in a driving force transmission canceling state, and the other developing means rotating shaft and the driving force transmitting means of the driving means rotating shaft are in a driving force transmitting canceling state.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the cam members provided at both ends in the rotation axis direction of the image bearing member are connected to one of the developing means by the rotation of the cam member. The position where the distance between the carrier is in the development state and the distance between the other development means and the image carrier is in the non-development state, the distance between the one development means and the image carrier is in the non-development state, and the other development means Between the other developing means and the image carrier is in the developed state, and the distance between the one developing means and the image carrier is in the non-developed state. The cam member having a position and two cam surfaces formed integrally with each other has a developed state in which the distance between one developing means and the image carrier is developed by the rotation of the cam member, and the other developing means and the image bearing member. The body spacing becomes undeveloped . At the same time, the driving force transmission means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling state. And the distance between one developing means and the image carrier is in a non-developed state, and the distance between the other developing means and the image carrier is in a non-developed state. Further, the driving force transmission means of one developing means rotating shaft and the driving means rotating shaft is in a driving force transmission released state, and the other developing means rotating shaft and the driving force transmitting means of the driving means rotating shaft are in a driving force transmission released state. The distance between the other developing means and the image carrier is in the developing state, and the distance between the one developing means and the image carrier is in the non-developing state, and the other developing means rotating shaft and the driving means are rotated. The driving force transmission means of the shaft is in a driving force transmission state, and one developing means rotation shaft and the driving force transmission means of the driving means rotation shaft have a position in a driving force transmission release state.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the driving unit that rotationally drives the developing unit receives a driving force from a driving source via a one-way clutch. In addition, the one-way clutch that transmits the driving force to the driving unit that rotationally drives each developing unit receives the driving force from a common driving source, and switches the rotation direction of the driving source to each driving unit. On the other hand, the driving force can be transmitted alternatively.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the image carrier of the developing means by the urging force of the urging means that urges the developing means in one of the movable directions. In order to always restrict the movement in the proximity direction, a bearing member that supports the developing means so as to be rotatable about an axis parallel to the rotation axis of the image carrier is in contact with the cam surface of the cam member. .

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the supporting means for supporting the developing means so as to be movable in the approaching / separating direction of the image carrier is the developing means. A bearing member is supported which is rotatably supported around an axis parallel to the rotation axis of the image carrier.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the urging means for urging the developing means in one of the movable directions causes the developing means to rotate the image carrier. The bearing member is rotatably urged around an axis parallel to the axis.

  According to the first aspect of the present invention, it is possible to stably define the development gap with high accuracy, and it is possible to prevent the photosensitive drum rotational load fluctuation and the impact / vibration during the development switching. For this reason, it is possible to improve the device reliability as well as to improve the image quality of the output image.

  According to the second aspect of the invention, it is possible to stably define the development gap with high accuracy and to perform a stable development switching operation. For this reason, it is possible to achieve a significant improvement in device reliability as well as to improve the image quality of the output image.

  According to the third aspect of the invention, it is possible to increase the accuracy of the developing gap by reducing the number of parts that define the developing gap, and it is possible to realize space saving by simplifying the configuration and cost reduction by reducing the number of parts.

  According to the fourth aspect of the present invention, the retracting interval of the developing roller can be minimized, and the apparatus can be downsized and the development switching operation can be speeded up.

  According to the fifth aspect of the present invention, the output image switching between the color image and the monochrome image can be performed at high speed, and work efficiency can be provided to the user who has the same output ratio between the color image and the monochrome image.

  According to the sixth aspect of the present invention, the image output time at the time of continuous color image output is shortened, and the efficiency of the work can be improved in the work with a high color image usage ratio.

  According to the seventh aspect of the present invention, it is possible to extend the life of the component and improve the durability without incurring an increase in cost. Therefore, it is possible to reduce the cost of the apparatus and improve the reliability.

  According to the eighth aspect of the invention, it is possible to increase the accuracy of the development gap by reducing the number of parts that define the development gap, and it is possible to realize space saving by simplifying the configuration and cost reduction by reducing the number of parts.

  According to the ninth aspect of the invention, the development gap position accuracy can be improved by improving the developing roller attitude accuracy and the supporting rigidity, and the space can be saved by simplifying the configuration and the cost can be reduced by reducing the number of parts.

  According to the tenth aspect of the present invention, even if the rigidity of the developing unit is reduced, the developing unit can be constantly brought into contact with the cam stably, and the cost can be reduced by reducing the component cost.

  Next, embodiments of an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 9 show an embodiment of an image forming apparatus of the present invention.

  FIG. 1 shows an internal configuration of an embodiment of an image forming apparatus to which the present invention is applied. FIG. 1 is a schematic configuration diagram showing a main part of an image forming apparatus that uses two photosensitive drums provided with two developing devices in parallel and forms a full-color image on an intermediate transfer member (intermediate transfer belt in the figure). . Such a configuration is characterized in that the apparatus can be miniaturized and the printing speed can be increased as compared with a configuration using a single photosensitive drum.

  In this image forming apparatus, at the time of image formation, two image carriers (hereinafter referred to as photosensitive drums) 101 and 201 are rotationally driven in the directions of arrows (clockwise), and the surfaces thereof are uniformly charged by the chargers 102 and 202. Thereafter, the exposure apparatuses 103 and 203 perform exposure according to the input image information to form an electrostatic latent image. Then, the cyan developing unit 110, the magenta developing unit 120, the yellow developing unit 210, and the black developing unit 220 are moved by the development switching mechanisms 114, 124, 214, and 224, and the first color (cyan) developing roller 111 is moved to the photosensitive member. The developing roller 211 for the second color (yellow) is positioned at the developing position facing the photosensitive drum 201 at the developing position facing the drum 101, and toner is attached to the electrostatic latent image on the photosensitive drum 101. Develop as a cyan toner image. At the same time, toner is attached to the electrostatic latent image on the photosensitive drum 201 to develop it as a yellow toner image. The cyan toner image and the yellow toner image are primary-transferred at primary transfer portions T11 and T12 on an intermediate transfer member (intermediate transfer belt) 105 that is in contact with the photosensitive drums 101 and 201 and rotates in an arrow direction. Transcribed. Then, the primary transfer process is sequentially performed for the other two colors, that is, magenta and black, and the four color toner images are superimposed on the intermediate transfer belt 105. These four-color toner images are secondarily transferred collectively to the recording material P conveyed from a paper feed cassette (not shown) by the secondary transfer member 106 of the secondary transfer portion T2, thereby providing full color. An image can be obtained.

First and second embodiments will be described.
2 and 3 are diagrams showing a detailed configuration example of the photosensitive drum driving unit. Here, as a means for bringing the developer on the non-operating developing roller into a non-contact state with respect to the photosensitive drum, the two developing units that rotatably support the developing roller are at least close to and away from the photosensitive drum. Support to move. At the same time, it is biased in one of the movable directions and brought into contact with the cam surface of the cam member, thereby restricting its movement and rotating the cam member. Accordingly, a method is adopted in which the position of the developing roller relative to the photosensitive drum is shifted and the developer spike formed on the developing roller is moved to the photosensitive drum non-contact position.

  In FIG. 2, the photosensitive drum 101 is supported by the side plate 170 of the image forming unit I so as to be rotatable about the photosensitive drum axis. The C color developing unit 110 including the photosensitive drum upstream developing roller 111 and the M color developing unit 120 including the photosensitive drum downstream developing roller 121 are supported by the support means 115 and 125 with respect to the side plate 170 of the image forming unit I. The photosensitive drum is supported so as to be movable in the proximity / separation direction. Further, the side plate 170 of the image forming unit I is urged in the proximity of the photosensitive drum by the urging means 117 and 127. Roller members 112 and 122 that are rotatable on the developing roller shaft are provided at the end portions of the developing rollers 111 and 121 on the side plate 170, and the cam of the cam member 104 having a rotating shaft parallel to the photosensitive drum shaft. It always contacts the surface 104a. Thus, the movement of the developing units 110 and 120 by the urging force of the urging means 117 and 127 is restricted. The photosensitive drum 101 and the developing units 110 and 120 are supported and urged by a similar configuration with respect to an image forming unit side plate (not shown) on the other end side in the axial direction of the photosensitive drum. The movement of the member is restricted by contacting the same cam member.

  In the above configuration, the cam member rotates at both ends in the photosensitive drum axial direction, and the distance from the cam member rotating shaft to the cam surface 104a with which the roller members 112 and 122 abut changes. As a result, the distance from the cam member rotating shaft to the developing roller shaft is changed, and the distance from the developing roller shaft to the photosensitive drum shaft is changed. Change. In FIG. 2A, the developing roller 111 disposed on the upstream side of the photosensitive drum is in contact with the photosensitive drum 101 at a predetermined developing gap with respect to the photosensitive drum 101 and downstream of the photosensitive drum. In the developing roller 121 disposed on the side, the developer is not in contact with the photosensitive drum 101.

  The developing roller driving state at this time is shown in FIG. A drive side transmission means 511a at one end of the drive force transmission means 511 is coaxially connected to a drive shaft 510 connected to a drive source provided on the apparatus main body side. Driven side transmission means 511c is coaxially connected to the shaft 111s of the developing roller 111. Here, the driving force transmitting means 511 is in a driving force transmitting state, and when the driving shaft 510 rotates by driving the driving source, the driving side transmitting means 511a transmits the rotational driving force to the driven side transmitting means 511c. Then, the developing roller 111 rotates. Similarly, a drive side transmission means 521a at one end of the drive force transmission means 521 is coaxially connected to the drive shaft 520 connected to a common drive source. Driven side transmission means 521c is coaxially connected to the shaft 121S of the developing roller 121. Here, the driving force transmission means 521 is in a driving force transmission release state, and the developing roller 121 does not rotate even when the driving source is driven and the driving shaft 520 rotates.

  FIG. 2B shows a state in which the cam member is rotated counterclockwise about the rotation axis in order to switch the developing function to the developing roller 121 disposed on the downstream side of the photosensitive drum. The developing roller 121 arranged on the downstream side of the photosensitive drum is in contact with the photosensitive drum 101 at a predetermined development gap with respect to the photosensitive drum 101, and the developing roller arranged on the upstream side of the photosensitive drum. In 111, the developer is not in contact with the photosensitive drum 101.

  At this time, as shown in FIG. 3B, the driving side connecting portion 521a of the driving force transmitting means 521 connected coaxially to the driving shaft 520 and the shaft connected to the shaft 121S of the developing roller 121 coaxially. The driving side connecting portion 521c is in a driving force transmission state. When the driving shaft 520 is rotated by driving the driving source, the driving side transmission means 521a transmits the rotational driving force to the driven side transmission means 521c, and development is performed. The roller 121 rotates. Similarly, the driving side connecting portion 511a of the driving force transmitting means 511 connected coaxially to the driving shaft 510 and the driven side connecting portion 511c connected coaxially to the shaft 111S of the developing roller 111 are respectively driven. Even if the driving force source is driven and the driving shaft 510 rotates, the developing roller 111 does not rotate.

  Here, the driving force transmission means 511, 521 are the rotation centers of the driven side connecting portions 511b, 521b connected to the developing roller shaft with respect to the rotation center shafts of the driving side connecting portions 511a, 521a connected to the driving shaft. When the driving force transmission is released, the shafts are configured to be movable in directions orthogonal to the respective rotation center axes while maintaining the respective rotation axis center axes in a parallel state. For this reason, the rotation of the cam member allows the developing roller to move with respect to the drive shaft between a position where the distance from the photosensitive drum is a predetermined developing gap and a position where the developing roller is not developed.

A configuration for realizing the function of such a driving force transmission means is shown in FIG. As shown in FIG. 4A, the driving-side transmission means 511a is formed with a driving force transmission portion 511b having a plurality of planes parallel to the rotation axis. The driven side transmission means 511c is formed with a driving force transmitted portion 511d having a plurality of planes parallel to the rotation axis. The roller member 112 abuts on the cam surface 104a to define the development gap so that the developing roller is in a developing state with respect to the photosensitive drum, and at this time, the rotation of the driving side transmission unit 511a and the driven side transmission unit 511c is rotated. The axis is coaxial.
The drive-side transmission means 511 a is biased in a direction in which the integrally formed rotation axis direction defining portion 511 e comes into contact with the cam surface 104 b formed on the cam member 104. At the same time, the rotation axis direction defining portion 511e abuts on the cam surface 104b, so that the rotation axis direction position of the drive side transmission means 511a with respect to the driven side transmission means 511c is defined to be in the driving force transmission state. .

When the driving side transmission means 511a is driven in this state, the driving force transmission portion 511b of the driving side transmission means 511a is in contact with the driving force transmission portion 511d of the driven side transmission means 511c to transmit the rotational driving force. The developing roller is rotated by rotating the driving source.
Similarly, the driving side transmission means 521a is also provided with a driving force transmission portion 521b. Similarly, a driving force transmitted portion 521d is formed in the driven side transmission means 521c.
The roller member 122 abuts on the cam surface 104a and defines a development gap so that the developing roller is in a non-development state with respect to the photosensitive drum, and at this time, the driving side transmission unit 521a and the driven side transmission unit 521c. The rotation axis is not coaxial.

Further, the drive-side transmission means 521a is biased in a direction in which the integrally formed rotation axis direction defining portion 521e abuts on the cam surface 104b formed on the cam member 104. At the same time, the rotational axis direction defining portion 521e contacts the cam surface 104b, so that the rotational axis direction position of the driving side transmission means 521a with respect to the driven side transmission means 521c is defined to be in the driving force transmission release state. Yes.
Even if the driving side transmission means 521a is driven in this state, the driving force transmission portion 521b of the driving side transmission means 521a does not contact the driving force transmission portion 521d of the driven side transmission means 521c, and the rotational driving force is not Not transmitted. For this reason, even if the drive source is driven to rotate, the developing roller does not rotate.

FIG. 4B shows a state where the cam member is rotated to switch the developing function.
The roller member 122 abuts against the cam surface 104a and defines a development gap so that the developing roller is in a developing state with respect to the photosensitive drum, and at this time, the rotation of the driving side transmission unit 521a and the driven side transmission unit 521c. The axis is coaxial.
Further, in the driving side transmission means 521a, the rotation axis direction position of the driving side transmission means 521a with respect to the driven side transmission means 521c becomes a driving force transmission state by the rotation axis direction defining portion 521e coming into contact with the cam surface 104b. It stipulates that

When the driving side transmission means 521a is driven in this state, the driving force transmission portion 521b of the driving side transmission means 521a contacts the driving force transmission portion 521d of the driven side transmission means 521c to transmit the rotational driving force. The developing roller is rotated by rotating the driving source.
The roller member 112 is in contact with the cam surface 104a so as to define a development gap so that the developing roller is not developed with respect to the photosensitive drum. At this time, the rotating shafts of the drive side transmission means 511a and the driven side transmission means 511c are not coaxial.
Further, the drive-side transmission means 511 a is biased in a direction in which the integrally formed rotation axis direction defining portion 511 e comes into contact with the cam surface 104 b formed on the cam member 104. At the same time, the rotational axis direction defining portion 511e abuts on the cam surface 104b, so that the rotational axis direction position of the driving side transmission means 511a with respect to the driven side transmission means 511c is defined to be in the driving force transmission release state. .

Even if the driving side transmission means 511a is driven in this state, the driving force transmission portion 511b of the driving side transmission means 511a does not contact the driving force transmission portion 511d of the driven side transmission means 511c, and the rotational driving force is transmitted. Not. For this reason, even if the drive source is driven to rotate, the developing roller does not rotate.
Here, the driving force transmission means is configured to have a degree of freedom of movement in the direction orthogonal to the rotation axis of the developing roller with respect to the driving shaft only when the driving transmission is released. For this reason, it is desirable to form the cam surface so that the development gap / development / non-development state switching operation of the development gap is performed only in a reliable driving force transmission release state.

  Therefore, after the cam member 104 starts and completes the operation that the driving force transmitting means on one developing roller side changes from the driving force transmitting state to the driving force transmitting released state by the rotation, After the operation to change the interval between the photosensitive drums from the development state to the non-development state and the operation to change the interval between the other development roller and the photosensitive drum from the non-development state to the development state is completed, the other development side After the driving force transmission means starts the operation of changing from the driving force transmission release state to the driving force transmission state, the driving force transmission unit ends. At the same time, the driving force transmitting means on the other developing roller side starts the operation of changing from the driving force transmitting state to the driving force transmission canceling state, and after this operation is completed, the interval between the other developing roller and the photosensitive drum is increased. Then, the operation of changing from the development state to the non-development state is started. Further, after the operation of changing the interval between the one developing roller and the photosensitive drum from the non-developing state to the developing state is completed, the driving force transmitting means on the one developing side changes from the driving force transmission canceling state to the driving force transmitting state. By forming the cam surface so as to start / end the changing operation, stable development switching can be realized.

A third embodiment will be described.
In the configuration of FIG. 5, the description of the configurations and operations equivalent to those of the first and second embodiments and the configurations of FIGS. The roller members 112 and 122 at the end of the developing roller are always in contact with the cam surface 104a of the cam member 104 that is rotatably supported coaxially with the photosensitive drum shaft 101a, thereby restricting the movement of the developing roller and the photosensitive member. Defines the distance from the drum. The drive-side transmission means 511a and 521a are driven to the driven-side transmission means 511c and 521c by the rotation axis direction defining portions 511e and 521e formed integrally with the cam surface 104b formed on the cam member 104. The position of the transmission means 511a, 521a in the rotational axis direction is defined, and the driving force transmission state / transmission release state is defined.

  In the configuration as described above, by providing a cam member that defines the distance between the photosensitive drum developing rollers on the photosensitive drum coaxially, it is possible to improve the development gap accuracy by reducing the number of parts that define the developing gap, Space can be saved by simplifying the configuration, and cost can be reduced by reducing the number of parts.

Fourth, fifth, and sixth embodiments will be described.
In FIG. 6, the description of the configuration and operation equivalent to those of the first embodiment and FIGS. 2, 3, and 4 is omitted.
In FIG. 6A, the developing roller 111 disposed on the upstream side of the photosensitive drum has a developer in contact with the photosensitive drum 101 at a predetermined developing gap with respect to the photosensitive drum 101, and the developing roller 111 side. The driving force transmission means 511 (not shown) is in a driving force transmission state. The developing roller 121 disposed on the downstream side of the photosensitive drum is in a state where the developer is not in contact with the photosensitive drum 101, and driving force transmitting means 521 (not shown) on the developing roller 121 side is driven. It is in the state of canceling force transmission.

FIG. 6B shows a state where the cam member is rotated clockwise about the rotation axis in order to stop the developing function of the photosensitive drum upstream side developing roller 111. The photosensitive drum upstream developing roller 111 and the photosensitive drum downstream developing roller 121 are in a non-contact state with the developer with respect to the photosensitive drum 101, and driving force transmission means 511 and 521 (not shown) are provided. The driving force transmission is released.
FIG. 6C shows a state in which the cam member is further rotated clockwise about the rotation axis in order to make the developing function of the developing roller 121 on the downstream side of the photosensitive drum effective. The developer on the downstream side of the photosensitive drum 121 is in contact with the photosensitive drum 101 at a predetermined development gap with respect to the photosensitive drum 101. At the same time, the driving force transmitting means 521 (not shown) on the developing roller 121 side is in a driving force transmitting state. The developing roller 111 disposed on the upstream side of the photosensitive drum is in a state where the developer is not in contact with the photosensitive drum 101, and a driving force transmitting means 511 (not shown) on the developing roller 111 side is driven. It is in the state of canceling force transmission.

  When the operation of the image forming unit I including the C and M color developing units is stopped when outputting a black and white image, the conventional method of Japanese Patent Application No. 2002-195201 provides a state in which both developing rollers are in a non-developing state. When one of the developing rollers is in the developing state, the other developing roller is in a state of being more distant from the photoreceptor than necessary, and the size of the apparatus and the development state switching time are inevitably increased. In the present embodiment, the upper and lower developing units are separate bodies, and it is possible to effectively utilize the configuration that can be independently moved and positioned. It is possible to reduce the size of the apparatus and speed up the development switching operation.

  In addition, as shown in FIG. 6, there is a state in which the photosensitive drum is in the non-development interval between the two developing rollers during the developing function switching operation from one developing roller to the other developing roller. Therefore, the output image switching from a color image to a monochrome image and the output image switching from a monochrome image to a color image are both fast, and effective product specifications for users who have the same color image and monochrome image output ratio. Can be realized.

  Here, as shown in FIG. 7, by rotation of the cam member, one developing roller is in a developing state, the other developing roller is in a non-developing state, and both developing rollers are in a non-developing state. During this state, a cam surface having a state in which the other developing roller is in a developing state and one developing unit is in a non-developing state is formed. As a result, there is no state in which the photosensitive drums are in the non-development interval between the two developing rollers during the developing function switching operation from one developing roller to the other developing roller. For this reason, the development color switching operation time during continuous color image output can be shortened, the image output time can be increased, and an effective product specification can be realized for a user with a high color ratio.

A seventh embodiment will be described.
In the first and second embodiments and the description of FIG. 3, it has been described that the drive shafts 510 and 520 are driven by a common drive source. In this case, when the drive source is driven in the apparatus operating state, the drive shafts 510 and 520 are always in a rotating state. The drive side transmission means 511a and 521a are always in a rotating state, and the rotation axis direction defining portions 511e and 521e for defining the rotation axis direction position of the drive side transmission means 511a and 521a and the cam surface 104b are affected by friction. In addition, it is difficult to extend the life of parts, and heat problems occur.
On the other hand, if individual drive sources can be provided for the drive shafts 510 and 520, the drive source corresponding to the developing roller in the non-development state can be stopped, and the influence of friction and heat is greatly reduced. However, there are significant cost barriers.

  As shown in FIG. 8, gears 512 and 522 are provided on the shafts of the drive shafts 510 and 520 via a one-way clutch, and from the motor output shaft 501 as a drive source to the gear 512 via one one-way clutch. Directly transmits the rotational driving force to the gear 522 via the other one-way clutch via the idle gear 502. This motor can also selectively drive the drive shafts 510 and 520 by switching the rotation direction, and the above problem can be solved even by using one drive source.

Eighth, ninth, and tenth embodiments will be described.
In FIG. 9, the description of the same configuration and operation as those of the first embodiment and FIG. 2 is omitted. The photosensitive drum 101 is supported by the side plate 170 of the image forming unit I so as to be rotatable about the photosensitive drum axis. A bearing 113 that rotatably supports the photosensitive drum upstream developing roller 111 with respect to the developing unit 110 and a bearing 123 that rotatably supports the photosensitive drum downstream developing roller 121 with respect to the developing unit 120 include an image forming unit I. The side plate 170 is supported by the support means 115 and 125 so as to be movable in the proximity and separation directions of the photosensitive drum. Further, the bearing 113 of the developing unit 110 and the bearing 123 of the developing unit 120 are urged in the proximity of the photosensitive drum by the urging means 117 and 127 with respect to the side plate 170 of the image forming unit I. The bearing 113 of the developing unit 110 and the bearing 123 of the developing unit 120 are always in contact with the cam surface 104a of the cam member 104 having a rotation shaft parallel to the photosensitive drum shaft, so that the biasing means 117 and 127 are attached. The movement of the developing units 110 and 120 by the force is limited. The photosensitive drum 101 and the developing units 110 and 120 are supported and urged with a similar configuration with respect to an image forming unit side plate (not shown) on the other end side in the axial direction of the photosensitive drum. At the same time, a bearing that rotatably supports the developing roller comes into contact with a similar cam member, so that movement is limited.

In the configuration as described above, the cam member rotates at both ends in the photosensitive drum axial direction, and the distance from the cam member rotating shaft to the cam surface 104a with which the bearings 113 and 123 abut changes. As a result, the distance from the cam member rotation shaft to the developing roller shaft changes, and the distance from the developing roller shaft to the photosensitive drum shaft changes. As a result, the distance between the photosensitive drum and the developing roller, that is, the so-called developing gap changes.
Since the outer periphery of the bearing that supports the developing roller directly contacts the cam member, it is possible to increase the developing gap accuracy by reducing the number of parts that define the developing gap between the photosensitive member and the developing roller. At the same time, it is possible to realize space saving by simplifying the configuration and cost reduction by reducing the number of parts.

Further, since the outer periphery of the bearing that supports the developing roller is directly supported, the developing gap position accuracy is improved by improving the developing roller attitude accuracy and the supporting rigidity. At the same time, it is possible to realize space saving by simplifying the configuration and cost reduction by reducing the number of parts.
Furthermore, since the outer periphery of the bearing that supports the developing roller is directly urged, the developing unit can be kept in constant contact with the cam even when the rigidity of the developing unit is reduced. Can be realized.

1 is a diagram illustrating an internal configuration example of an embodiment of an image forming apparatus of the present invention. It is a figure which shows the detailed structural example of a photoconductor drum drive part. It is a figure which shows the detailed structural example of a photoconductor drum drive part. It is a figure which shows the structural example of a driving force transmission means. It is a figure which shows the structural example of a driving force transmission means. It is a figure which shows the detailed structural example of a photoconductor drum drive part. It is a figure which shows the detailed structural example of a photoconductor drum drive part. It is a figure which shows the detailed structural example of a photoconductor drum drive part. It is a figure for demonstrating the operation example of a photoconductor drum drive part.

Explanation of symbols

101, 201 Photosensitive drum 104a Cam surface 110, 120 Developing unit 111, 211 Developing roller 113, 123 Bearing 114, 124, 214, 224 Development switching mechanism 115, 125 Supporting unit 117, 127 Energizing unit 120 Magenta developer 121 Photosensitive Body drum downstream developing roller 170 Side plate of image forming unit I 210 Yellow developing device 220 Black developing device

Claims (10)

One developing unit that visualizes the latent image of the same rotating image carrier with an arbitrary color and the other developing unit that visualizes the latent image with a color different from the arbitrary color, respectively. When the color is switched in the image forming unit having a configuration arranged so as to face the outer periphery of the body and adjacent to each other, development is performed from any one of the developing means to the other developing means while the image carrier is rotating. The functions are switched, and the visible image on the image carrier obtained by making the visible image is sequentially transferred to an intermediate transfer member, and the transfer image on the intermediate transfer member is further transferred to a recording material to obtain a recorded image. In the obtained image forming apparatus,
A supporting unit that supports each of the one developing unit and the other developing unit so as to be movable at least in the approaching / separating direction with respect to the image carrier, and a biasing unit that biases the developing unit in one of the movable directions. And the movement of the developing means in the moving direction by the urging force of the urging means is always restricted, and by rotating, the distance between the one developing means and the image carrier is in the developing state, and The position where the distance between the other developing means and the image carrier is in a non-development state, and the distance between the other developing means and the image carrier is in the developed state, and the one developing means and the image carrier A cam member having a cam surface for changing the distance between each of the developing means and the image carrier at positions where the gap is in a non-development state is provided at both ends in the rotational axis direction on an axis parallel to the rotational axis of the image carrier. Part ,
The one developing means and the other developing means are rotatably supported around an axis parallel to the rotation axis of the image carrier, and are provided with driving means for driving the developing means to rotate. A driving force transmitting means that is coaxially connected to each of the rotating shaft of the driving means and the rotating shaft of the driving means and transmits the rotational driving force of the driving means to the developing means; The driving force transmission state is released when the rotating shaft of the driving means and the rotating shaft of the driving means move by a predetermined distance in the rotating shaft direction, and the rotating shaft of the developing means is moved relative to the rotating shaft of the driving means, At least one of the cam members provided at both ends in the rotational axis direction of the image carrier. On the other hand, By rotating, the distance between the one developing means and the image carrier is in the developing state, and the distance between the other developing means and the image carrier is in the non-developing state, and the rotation axis of the one developing means is The driving force transmitting means connected to the rotating shaft of the driving means is in a driving force transmitting state, and the driving force transmitting means connected to the rotating shaft of the other developing means and the rotating shaft of the driving means is released. And the distance between the other developing means and the image carrier is in the developing state, and the distance between the one developing means and the image carrier is in the non-developing state, and the rotational axis of the other developing means The driving force transmitting means connected to the rotating shaft of the driving means enters a driving force transmitting state, and the driving force transmitting means connected to the rotating shaft of the one developing means and the rotating shaft of the driving means cancels the driving force transmission. State The location, an image forming apparatus in which the cam surface to change the rotation axis direction distance between the rotation axis of the rotary shaft and the driving means of each of the developing means, characterized in that it is formed integrally.   The cam member formed integrally with the two cam surfaces is rotated so that the driving force transmitting means of the rotating shaft of the one developing means and the rotating shaft of the driving means transmits the driving force from the driving force transmitting state. After starting and ending the operation of changing to the release state, the operation of changing the interval between the one developing unit and the image carrier from the developing state to the non-developing state is started, and the other developing unit and the image carrier are started. After the operation of changing the interval between the non-development state and the development state is completed, the drive force transmission means of the rotation shaft of the other development means and the rotation shaft of the drive means is changed from the drive force transmission release state to the drive force transmission state. And after the operation of changing the driving force transmission means between the rotation shaft of the other developing means and the rotation shaft of the driving means from the driving force transmission state to the driving force transmission release state is completed. The other current After the operation of changing the distance between the developing means and the image carrier from the development state to the non-development state and after the operation of changing the distance between the one development means and the image carrier from the non-development state to the development state is completed, 2. The driving force transmitting means between the rotating shaft of one developing means and the rotating shaft of the driving means starts and ends the operation of changing from the driving force transmission canceling state to the driving force transmitting state. Image forming apparatus.   3. The image forming apparatus according to claim 1, wherein cam members provided at both ends of the image carrier in the rotation axis direction are provided so as to be coaxially rotatable with respect to the rotation axis of the image carrier. apparatus.   The cam members provided at both ends of the image bearing member in the rotation axis direction are in a developed state, and the distance between the other developing unit and the image carrier is in a non-developed state. Other than the position where the distance between the other developing means and the image carrier is in the developing state and the distance between the one developing means and the image carrier is in the non-developing state. A cam surface for changing the distance between each developing means and the image carrier at a position where the distance between the carrier is in a non-development state and the distance between the other developing means and the image carrier is in a non-development state; In the cam member in which the two cam surfaces are integrally formed, the distance between the one developing means and the image carrier is in the developed state, and the distance between the other developing means and the image carrier is in the non-developed state. The one A position where the driving force transmitting means of the image means rotating shaft and the driving means rotating shaft is in a driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling state; The distance between the other developing means and the image carrier is in the developing state, and the distance between the one developing means and the image carrier is in the non-developing state, and the other developing means rotating shaft and the driving means rotating shaft are driven. In addition to the position where the force transmitting means is in the driving force transmitting state and the driving force transmitting means of the one developing means rotating shaft and the driving means rotating shaft is in the driving force transmitting released state, the one developing means and the image carrier The interval is in a non-development state, the interval between the other developing unit and the image carrier is in a non-developing state, and the driving force transmission unit of the one developing unit rotation shaft and the driving unit rotation shaft cancels the driving force transmission. Condition And the rotation direction distance between each of the developing means rotating shaft and the driving means rotating shaft is changed to a position where the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in a driving force transmission canceling state. 4. The image forming apparatus according to claim 1, further comprising a cam surface configured to perform the operation.   The cam members provided at both ends of the image bearing member rotational axis are in a developed state by the rotation of the cam member, and the distance between the one developing unit and the image bearing member is in a developed state, and the other developing unit and the image bearing member Between the position where the interval between the two bodies is in the non-development state and the position where the interval between the other developing means and the image carrier is in the development state and the interval between the one development means and the image carrier is in the non-development state. , The distance between the one developing means and the image carrier is in a non-development state, and the distance between the other developing means and the image carrier is in a non-development state. In the formed cam member, the rotation of the cam member causes the interval between the one developing means and the image carrier to be in a developed state, and the interval between the other developing means and the image carrier is not developed. , The one developing means A position where the driving force transmitting means of the rotation shaft and the driving means rotating shaft is in the driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in the driving force transmission canceling state; The developing unit and the image carrier are in a development state, and the one developing unit and the image carrier are in a non-development state, and the driving force transmission unit between the other developing unit rotation shaft and the driving unit rotation shaft Between the one developing means and the image carrier between the position where the one developing means rotating shaft and the driving force transmitting means of the driving means rotating shaft are in the driving force transmission canceling state. In the non-development state, the distance between the other development unit and the image carrier is in the non-development state, and the drive force transmission unit between the one development unit rotation shaft and the drive unit rotation shaft enters the drive force transmission release state. And before The other developing means rotating shaft and the image forming apparatus according to claim 4, wherein a position where the driving force transmitting means is a driving force transmission releasing state of the drive unit the rotary shaft.   5. The image forming apparatus according to claim 4, wherein the cam members provided at both ends in the rotation axis direction of the image carrier are developed so that the distance between the one developing means and the image carrier is developed by the rotation of the cam member. A position where the distance between the other developing means and the image carrier is in a non-development state, and a distance between the one developing means and the image carrier is in a non-development state, and the other developing means and the image carrier. A position where the distance between the other developing means and the image carrier is in the developed state, and a position where the distance between the one developing means and the image carrier is in the non-developed state. The cam member in which the two cam surfaces are integrally formed has a developing state in which the interval between the one developing unit and the image carrier is developed by the rotation of the cam member, and the other developing unit. Image carrier spacing is not At the same time, the driving force transmitting means of the one developing means rotating shaft and the driving means rotating shaft is in the driving force transmitting state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is the driving force. The position where the transmission is released and the distance between the one developing means and the image carrier are in the non-development state, and the distance between the other developing means and the image carrier is in the non-development state. Between the position where the driving force transmission means of the means rotating shaft and the driving means rotating shaft is in the driving force transmission released state, and the driving force transmitting means of the other developing means rotating shaft and the driving means rotating shaft is in the driving force transmission released state. In addition, the distance between the other developing means and the image carrier is in the developed state, and the distance between the one developing means and the image carrier is in the non-developed state, and the other developing means rotating shaft and the driving means rotating shaft. of Power transmission means is a driving force transmission state, and an image forming apparatus wherein the one developing means rotating shaft and the driving means rotational shaft of the driving force transmitting means and having a position at which the driving force transmission releasing state.   The driving means for rotationally driving the developing means is transmitted with a driving force from a driving source via a one-way clutch, and the one-way clutch for transmitting the driving force to the driving means for rotationally driving each of the developing means is 7. A driving force is transmitted from a common driving source, and the driving force can be transmitted alternatively to each of the driving means by switching the rotation direction of the driving source. The image forming apparatus according to any one of the above.   In order to always restrict the movement of the developing means in the proximity direction of the image carrier by the urging force of the urging means for urging the developing means in one of the movable directions, the developing means with respect to the cam surface of the cam member. 8. The image forming apparatus according to claim 1, wherein a bearing member that supports the image bearing member rotatably about an axis parallel to the rotation axis of the image carrier is in contact with the image forming apparatus.   The supporting means for supporting the developing means so as to be movable in the approaching / separating direction of the image bearing member includes a bearing member that supports the developing means so as to be rotatable about an axis parallel to the rotation axis of the image bearing member. The image forming apparatus according to claim 1, wherein the image forming apparatus is supported.   The biasing means for biasing the developing means in one of the movable directions biases a bearing member that supports the developing means so as to be rotatable about an axis parallel to the rotation axis of the image carrier. The image forming apparatus according to any one of claims 1 to 7.

Images