JP2006227504A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain the reduction of an apparatus in terms of size and cost, to stably regulate a developing gap and the transmission state of a developing roller gear with high accuracy, and also, to attain an output image of high image quality, and also, to improve the reliability of the apparatus. <P>SOLUTION: The apparatus includes a supporting means for supporting one developing means and the other developing means so that they can move at least in an attaching/detaching direction to/from an image carrier, and an energizing means for energizing the developing means in one of the movable direction. Besides, a cam member having a cam abutting surface for always controlling the movement of the developing means toward the movable direction by the energizing force of the energizing means, and for changing a distance between each developing means and the image carrier so as to switch to a 1st position where a distance between one developing means and the image carrier is made in a developing state and a distance between the other developing means and the image carrier is made in a non-developing state, and so as to switch to a 2nd position where the distance between the other developing means and the image carrier is made in the developing state and the distance between one developing means and the image carrier is made in the non-developing state is arranged at each end in the rotating shaft direction on a shaft parallel to the rotating shaft of the image carrier. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and in particular, develops a latent image formed on the same image carrier by switching a plurality of developing rollers provided in a plurality of developing units containing developers of different colors. The present invention relates to a developing device.

Conventionally, 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 are provided. Patent Documents 1 to 3 propose an apparatus that obtains a multi-color image by sequentially transferring a visible image formed by each image forming unit onto a single intermediate transfer member.
When forming a full-color image of four colors, in the method using a single image carrier and intermediate transfer member, it is necessary to arrange four developing means around the image carrier, and the intermediate transfer member is rotated four times. On the other hand, in an image forming apparatus having two image stations as in Patent Document 1, there are two developing means arranged around the image carrier, and full color with two rotations of the intermediate transfer member. Since image formation is possible, it is possible to reduce the size / diameter of the image carrier and speed up the apparatus.

  Further, in Patent Document 2 and Patent Document 3, two developing rollers are disposed in the developing unit so as to be rotatable around an axis parallel to the rotating shaft of the photosensitive drum, and the developing unit is rotated on the rotating shaft of the photosensitive drum. The image forming unit is supported so as to be rotatable about a rotation axis substantially parallel to the image forming unit, and the developing unit is rotated by a predetermined rotation angle with respect to the image forming unit, and one of the two developing rollers is rotated. There has been proposed an image forming apparatus having a development function switching means for switching a distance between the development roller and the photosensitive drum to a development position.

  As described above, in the image forming apparatuses proposed in Patent Documents 1 to 3, the distance between the photosensitive member and the developing roller (developing gap) is switched by the rotation of the developing unit, and at the same time, the driving gear and the developing roller gear are driven. Since the force transmission state is switched, the development function can be surely switched at a small size and low cost.

  Further, Patent Document 4 proposes a configuration for disabling the two developing rollers of the image forming unit on the side not including the Bk color developing roller at the time of outputting a black and white image, and a photosensitive member due to unnecessary developer contact. It is possible to prevent the wear and deterioration of the developer due to the abrasion and deterioration of the film and unnecessary stirring, and it is possible to realize an image forming apparatus capable of reducing the running cost and reducing the environmental load by extending the life of the photosensitive member and the developer. .

Further, in Patent Document 5, the drive transmission gear for rotating the developing roller is provided coaxially with the photosensitive drum rotating shaft, and therefore, between the rotating shaft of the developing roller and the rotating shaft of the photosensitive drum. By maintaining only the distance with high accuracy, the two positional relationships of the photosensitive drum rotation shaft and the drive transmission gear rotation shaft with respect to the development roller rotation shaft can be realized with high accuracy, and high-quality image output and stable development roller drive can be realized. Can be realized.
Japanese Patent Laid-Open No. 10-177286 JP 2003-167410 A JP 2003-307903 A JP 2004-037872 A JP 2004-309877 A JP 2003-208011 A

  However, in Patent Documents 1 and 2 described above, the parallelism of each of the two developing rollers and the rotation center axis of the photosensitive drum and the rotation center axis of the image forming unit is defined by component accuracy. Since many parts are interposed between the photosensitive drums, it is difficult to ensure parallelism with parts accuracy, and the development gap cannot be defined with high accuracy. For this reason, particularly in Patent Document 3, an adjustment mechanism is provided on the cam member that contacts both side plates of the image forming unit so that the rotation angle in the development switching operation can be arbitrarily adjusted by both side plates of the image forming unit. And the photosensitive drum are configured to absorb the parallelism deviation. However, the addition of an adjustment mechanism leads to an increase in the size of the device and an increase in cost, and there is a limit to the parallelism deviation that can be absorbed by adjusting the cam member. It is an obstacle. 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 fluctuates. Resulting in. Furthermore, 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 in a non-operating state. However, the developing unit rotation position where both developing rollers are in a non-developing state. By providing this, when one developing roller is in the developing state, the other developing roller is unnecessarily separated from the photosensitive member, and therefore the size of the apparatus and the development state switching time can be prevented from being prolonged. Absent.

  Further, Patent Document 5 proposes a configuration capable of realizing high image quality and stable development roller driving by providing a drive transmission gear coaxially with the photosensitive drum. As the development gap fluctuates due to the influence of the parallelism deviation between the body drum and the developing roller, the driving state of the developing roller also becomes unstable, which greatly improves the reliability of the development driving and the drive switching operation. It is an obstacle.

  According to Patent Document 6 proposed as a configuration for solving the above-described problem, the developing unit disposed around the photosensitive drum and biased toward the photosensitive drum is provided with a photosensitive drum on both sides of the photosensitive drum. The shaft of the developing roller is supported so as to be in contact with the cam contact surface of the cam member which is provided so as to be independently rotatable and at least one groove is formed on the outer peripheral surface. For this reason, since the parallelism between the photosensitive drum and the developing roller is almost defined by the accuracy of the cam member parts, it is possible to maintain a high accuracy of the developing gap and to apply an impact when the developing roller contacts the photosensitive drum. Can be minimized.

  However, according to Patent Document 6, the developing unit is biased to the photosensitive drum side, 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 rotationally driven, it is necessary to bring the shaft of the developing roller into contact with the cam member with a sufficient biasing 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 component costs. Further, the rotation of the cam member for switching the development must generate a force against a sufficient urging force, so that there is a problem that a large power consumption is required or that a high-speed switching is difficult. Further, it is usually necessary to switch the development drive in addition to the switching of the development function by switching the interval between the developing roller and the photosensitive drum, and it is necessary to separately receive a configuration for switching the drive. Increase in size is inevitable.

  The present invention is for solving these problems, and positioning the developing means in a developing state with respect to the image carrier with high accuracy without incurring the complexity, size and cost of the apparatus. Therefore, it is possible to provide an image forming apparatus that can improve the image quality of an output image and that can stably perform a developing operation by positioning a developing member driven member with high accuracy relative to a driving force transmitting unit. Objective.

  In order to solve the above problems, the image forming apparatus of the present invention has different latent images on the image carrier in a state of being opposed to each other and adjacent to each other around the image carrier to be rotationally driven. At least one image forming unit provided with a plurality of developing means for visualizing with a color developer is provided. Further, when the color is switched in the image forming unit, the developing function is switched from one of the developing means to the other developing means while the image carrier is rotating, and the image obtained by making the visible image visible. The visible image on the carrier is sequentially primary transferred to the intermediate transfer member, and the transfer image on the intermediate transfer member is secondarily transferred to the recording material to form a recording image. The image forming apparatus according to the present invention is attached to one of the developing unit and the other developing unit at least in one of the moving direction of the developing unit and the supporting unit that supports the developing unit so as to move at least in the approaching / separating direction of the image carrier. Biasing means for biasing. Further, the movement of the developing means in the movable direction by the urging force of the urging means is always restricted, the distance between one developing means and the image carrier is in the development state, and the distance between the other developing means and the image carrier is non-developing. In the first position where the developing state is set, and in the second position where the interval between the other developing means and the image carrier is in the developing state, and the interval between the one developing means and the image carrier is in the non-developing state, Cam members having cam contact surfaces for changing the distance between the developing means and the image carrier are provided at both ends in the rotational axis direction on an axis parallel to the rotational axis of the image carrier. Further, in the image forming apparatus of the present invention, the one developing unit and the other developing unit are supported so as to be rotatable about an axis parallel to the rotation axis of the image carrier, and the one developing unit and the other developing unit are supported. When the driven member is fixed on the same axis as the rotation shaft and the interval between the one or the other developing means and the image carrier is in the developing state due to the rotation of the cam member, the driven member of the one or the other developing means When the distance between one or the other developing means and the image carrier is in the non-developing state, the driving force transmitting means that is in the non-developing state with the driven member of one or the other developing means is provided. It is characterized by the provision. Therefore, by realizing development function switching and development drive switching with the same configuration and operation, it is possible to reduce the size and cost of the apparatus. In addition, the development gap and development roller gear transmission state can be defined with high accuracy and stability, and the rotational load fluctuation and shock / vibration of the image carrier during development switching can be prevented. Reliability can be improved.

  Further, the driving force transmitting means is a driving force acting on the driven member when the driven member of the one or other developing means is driven in the driving force transmitting state. Is provided at the same position as the urging direction of the urging means. Therefore, the development roller position fluctuation of the developing means relative to the image carrier can be surely prevented, the development gap and the developing roller gear transmission state of the developing means can be stably defined with higher accuracy, and the biasing means is required. Therefore, the apparatus can be reduced in cost, speeded up, or reduced in power consumption.

  Further, the urging unit urges one developing unit and the other developing unit in different directions in the moving direction of each developing unit, and a driven member fixed to the one developing unit and the other developing unit includes: The driving force is transmitted to the same driving force transmission means in the driving force transmission state or the driving force non-transmission state. Therefore, it is possible to reduce the size of the apparatus by simplifying the configuration and reduce the cost by reducing the number of parts.

  The urging means is provided between the one developing means and the other developing means so as to urge the other developing means with respect to one developing means in the movable direction of each developing means. Therefore, it is possible to reduce the size of the apparatus by simplifying the configuration and reduce the cost by reducing the number of parts.

  Further, the cam member is provided so as to be rotatable coaxially with the rotation axis of the image carrier. Therefore, 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.

  The drive force transmission means is provided coaxially with the rotation axis of the image carrier so that the development switching operation reliability is improved by reducing the number of parts that define the development roller gear transmission state. it can.

  Further, the cam member is in a third position where 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. A cam contact surface for changing the interval between the image carriers is provided. Therefore, the retraction interval of the developing roller can be minimized, and the apparatus can be downsized and the development switching operation can be speeded up.

  Further, the cam member has a cam contact surface at a third position between the cam contact surface at the first position and the cam contact surface at the second position by the rotation of the cam member. Therefore, the output image switching between the color image and the monochrome image becomes faster, and an effective product specification can be realized for a user who has the same output ratio between the color image and the monochrome image.

  Further, the cam member has a cam contact surface at the second position between the cam contact surface at the first position and the cam contact surface at the third position by rotation of the cam member. Therefore, since the image output time during continuous color image output can be increased, product specifications effective for users with a high color ratio can be realized.

  Further, in order to always restrict the movement of each developing means in the proximity direction of the image carrier by the biasing force of the biasing means, each developing means is connected to the cam contact surface of the cam member with the rotation shaft of the image carrier. The bearing member which supports rotatably about a parallel axis | shaft contacts. Therefore, 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.

  Furthermore, the support means supports the bearing member, thereby improving the developing gap position accuracy by improving the attitude accuracy of the developing roller and improving the support rigidity, saving space by simplifying the configuration, and reducing the cost by reducing the number of parts. realizable.

  The urging unit urges each developing unit in the proximity of the image carrier and urges the bearing member. Therefore, even if the developing unit rigidity is reduced, the developing unit can be always brought into contact with the cam member stably, and the cost can be reduced by reducing the component cost.

  According to the image forming apparatus of the present invention, it is possible to improve the image quality of the output image by positioning the developing unit in the developing state with high accuracy with respect to the image carrier, and to adjust the driven member of the developing unit. By positioning with high accuracy with respect to the driving force transmitting means, a stable developing operation is possible.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a main part of an image forming apparatus to which the present invention is applied. The image forming apparatus shown in FIG. 2 is a two-image station type image forming apparatus that uses two photosensitive drums each having two developing units arranged side by side and forms a full color image on an intermediate transfer belt as an intermediate transfer member. It is. The image forming apparatus having such a configuration can reduce the size of the apparatus and increase the printing speed as compared with a configuration using a single photosensitive drum. In this image forming apparatus, at the time of image formation, the two photosensitive drums 101 and 201 are rotationally driven in the direction of arrow A, and the surfaces thereof are uniformly charged by the chargers 102 and 202. An electrostatic latent image is formed by performing exposure according to input image information. Then, the cyan development unit 104, the magenta development unit 105, the yellow development unit 204, and the black development unit 205 are moved by the development switching mechanisms 106, 107, 206, and 207, and the first image forming unit develops cyan as the first color. The developing roller 108 of the unit 104 is located at the developing position facing the photosensitive drum 101, and the developing roller 208 of the yellow developing unit 204, which is the second color in the second image forming unit, is located at the developing position facing the photosensitive drum 201. The toner is attached to the electrostatic latent image on the photosensitive drum 101 and developed as a cyan toner image, and the toner is attached to the electrostatic latent image on the photosensitive drum 201 and developed as a yellow toner image. To do. The cyan toner image and the yellow toner image are in contact with the photosensitive drums 101 and 201, are spread by rollers 302 and 303, and are transferred onto the intermediate transfer belt 301 that is an intermediate transfer member that rotates in the direction of arrow B. Primary transfer is performed at the next transfer portions T11 and T12. 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 301. These four color toner images are fully transferred onto the recording material P conveyed from a paper feed cassette (not shown) by the secondary transfer member 304 at the secondary transfer portion T2 so as to be full color. An image can be obtained.

  Next, FIG. 2, which is a schematic diagram illustrating the configuration of the developing function switching mechanism of the developing device, and the configuration of the developing drive switching mechanism of the developing device in the image forming apparatus according to the first exemplary embodiment of the present invention. This will be described with reference to FIG. In both figures, the same reference numerals as those in FIG. 1 denote the same components. Further, the first image forming unit will be described. Here, as 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 in the direction of approaching and separating from the photosensitive drum. The movable roller is movably supported and urged in one of the movable directions, and the movement of the cam member is restricted by contacting the cam contact surface of the cam member. A method is adopted in which the position is shifted and the developer spike formed on the developing roller is moved to the non-contact position of the photosensitive drum.

  In FIG. 2, the photosensitive drum 101 is supported so as to be rotatable about the axis of the photosensitive drum 101 with respect to the side plate 110 of the first image forming unit. A cyan developing unit 104 including a developing roller 108 positioned on the upstream side of the photosensitive drum 101 and a magenta developing unit 105 including a developing roller 109 positioned on the downstream side of the photosensitive drum 101 are included in the first image forming unit. The side plate 110 is supported by support means 111 and 112 so as to be movable in the approaching / separating direction of the photosensitive drum 101. Further, the side plate 110 of the first image forming unit is urged in the proximity direction of the photosensitive drum 101 by the urging means 113 and 114. Roller members 115 and 116 are provided on the side end portions of the side plates 110 of the developing rollers 108 and 109, respectively, on the developing roller shafts, and cams having a rotation axis parallel to the axis of the photosensitive drum 101. By constantly contacting the cam contact surface 117a of the member 117, the movement of the cyan developing unit 104 and the magenta developing unit 105 by the urging force of the urging means 113 and 114 is restricted. Therefore, the photosensitive drum 101, the cyan developing unit 104, and the magenta developing unit 105 are supported and urged with the same configuration on the side plate of the image station (not shown) on the other end side in the axial direction of the photosensitive drum 101. At the same time, the movement of the roller member on the rotation shaft of the developing roller is restricted by contacting a similar cam member.

  According to the above configuration, the cam member 117 rotates at both ends of the photosensitive drum 101 in the axial direction, and from the rotating shaft of the cam member 117 to the cam contact surface 117a on which the roller members 115 and 116 contact. As the distance changes, the distance from the rotation axis of the cam member 117 to the axis of each developing roller 108, 109 changes, and the distance from the axis of each developing roller 108, 109 to the axis of the photosensitive drum 101 changes. As a result, the distance between the photosensitive drum 101 and the developing rollers 108 and 109, the so-called developing gap, changes. In FIG. 2A, the developing roller 108 disposed on the upstream side of the photosensitive drum 101 is in contact with the photosensitive drum 101 while the developer is in contact with the photosensitive drum 101 with a predetermined development gap. In the developing roller 109 disposed on the downstream side of the photosensitive drum 101, the developer is not in contact with the photosensitive drum 101. In the developing roller driving mechanism shown in FIG. 3A at this time, a driving gear 119 is fixed to a driving shaft 118 coupled to a motor (not shown) as a driving source provided on the apparatus main body side. Has been. The drive gear 119 is a gear disposed on the shaft 122 of the developing roller 108 via a drive transmission gear 121 that is an intermediate idler gear that is rotatably disposed on an axis parallel to the rotation shaft 120 of the photosensitive drum 101. 123. When the drive shaft 118 is driven by the motor, the gear 123 is driven via the drive gear 119 and the drive transmission gear 121, and the developing roller 108 rotates. On the other hand, the drive gear 119 is connected to a drive transmission gear 124 which is an intermediate idler gear rotatably disposed on an axis parallel to the rotation shaft 120 of the photosensitive drum 101. At this time, the drive transmission gear 124 is connected. Is not connected to the gear 126 disposed on the shaft 125 of the developing roller 109, so that the developing roller 109 does not rotate even when the drive shaft 118 is driven by the motor.

  Next, as shown in FIG. 2B, in order to switch the developing function to the developing roller 109 arranged on the downstream side of the photosensitive drum 101, the cam member 117 is rotated counterclockwise about the rotation axis. Move. Therefore, the developing roller 109 disposed on the downstream side of the photosensitive drum 101 is in contact with the photosensitive drum 101 at a predetermined development gap with respect to the photosensitive drum 101 and is disposed on the upstream side of the photosensitive drum 101. The developed roller 108 is in a non-contact state with the developer on the photosensitive drum 101. At this time, as shown in FIG. 3B, the driving gear 119 is connected to the developing roller 109 via a driving transmission gear 124 that is rotatably arranged on an axis parallel to the rotating shaft 120 of the photosensitive drum 101. It is connected to a gear 126 arranged on the shaft 125 of the motor. When the drive shaft 118 is driven by the motor, the gear 126 is driven via the drive gear 119 and the drive transmission gear 124, and the developing roller 109 rotates. On the other hand, at this time, since the drive transmission gear 121 connected to the drive gear 119 is not connected to the gear 123 disposed on the shaft 122 of the developing roller 108, the developing roller is driven even if the driving shaft 118 is driven by the motor. 108 does not rotate.

  Here, by driving the drive gear 119 in the direction of arrow a, the drive transmission gear 121 or the drive transmission gear 124 is driven in the direction of arrow b, and the gear 123 or gear 126 on the developing roller shaft is driven in the direction of arrow c. When driven, the force d taking into account the effect of the gear pressure angle received by the gear 123 or the gear 126 has a component dx in the approaching / separating direction of the photosensitive drum 101, and the developing rollers 108 and 109 are photosensitive drums. 101 is driven in the approaching / separating direction. The direction of the force of the approaching / separating direction component dx of the photosensitive drum 101 is determined by the positional relationship between the gears 123 and 126 of the developing rollers 108 and 109 and the drive transmission gears 121 and 124. On the other hand, the positions of the drive transmission gears 121 and 124 with respect to the gears 123 and 126 on the developing roller shaft are determined in accordance with the direction of the force of the driving force received by the developing roller in the driving state of the developing roller. Is set to a position that coincides with the direction of the urging force in the approaching / separating direction of the photosensitive drum 101 by the urging means 113, 114, so that the developing rollers 108, 109 approach the photosensitive drum 101 by the driving force of the developing roller. Since movement in the separation direction is limited by the cam member 117, fluctuations in the position of the developing roller relative to the photosensitive drum 101 can be reliably prevented, and the urging force required for the urging means 113 and 114 can be suppressed. it can.

  According to the first embodiment having the above-described configuration, the developing function switching mechanism by changing the developing gap and the developing drive switching mechanism by changing the gear transmission state between the developing roller driving source have the same configuration and operation. This cam member can reduce the size and cost of the apparatus, and restricts the development gap and the gear transmission state of the developing roller by constantly contacting the movement of the photosensitive member in the approaching / separating direction at both ends of the developing roller. Therefore, it is possible to make stable regulation with high accuracy and to prevent the rotation load fluctuation and shock / vibration of the photosensitive drum at the time of development switching. it can.

  Next, FIG. 4 which is a schematic diagram showing the configuration of the developing function switching mechanism of the developing device and the configuration of the developing drive switching mechanism in the configuration of the developing device in the image forming apparatus according to the second embodiment of the present invention. This will be described with reference to FIG. In both figures, the same reference numerals as those in FIGS. 2 and 3 indicate the same components. Further, the first image forming unit will be described.

  In FIG. 4, the cyan developing unit 104 and the magenta developing unit 105 are supported so as to be movable in the approaching / separating direction of the photosensitive drum 101 by supporting means 111 and 112 with respect to the side plate 110 of the first image forming unit. Further, the cyan developing unit 104 is moved away from the photosensitive drum 101 by the urging means 113 with respect to the side plate 110 of the first image forming unit, and the magenta developing unit 105 is moved closer to the photosensitive drum 101 by the urging means 114. Is biased in the direction. The roller member 115 on the shaft of the developing roller 108 is always in contact with the cam contact surface 131a of the cam member 131, so that the movement of the cyan developing unit 104 by the urging force of the urging means 111 is restricted. Further, the roller member 116 on the shaft of the developing roller 109 is always in contact with the cam contact surface 131b of the cam member 131, so that the movement of the magenta developing unit 105 by the urging force of the urging means 114 is restricted. Therefore, the photosensitive drum 101, the cyan developing unit 104, and the magenta developing unit 105 are supported and attached to the side plate of the first image forming unit (not shown) on the other end side in the axial direction of the photosensitive drum 101 with the same configuration. In addition, the roller member on the rotation shaft of the developing roller is in contact with a similar cam member, and the movement is restricted. In FIG. 4A, the developing roller 108 disposed on the upstream side of the photosensitive drum 101 is in contact with the photosensitive drum 101 while the developer is in contact with the photosensitive drum 101 at a predetermined development gap. In the developing roller 109 disposed on the downstream side of the photosensitive drum 101, the developer is not in contact with the photosensitive drum 101. At this time, as shown in FIG. 5A, the drive gear 119 fixed to the drive shaft 118 is connected to the gear 123 of the developing roller 108, and the drive shaft 118 is driven by a motor (not shown). When this occurs, the gear 123 is driven via the drive gear 119 and the developing roller 108 rotates. On the other hand, since the driving gear 119 is not connected to the gear 126 of the developing roller 109 at this time, the developing roller 109 does not rotate even when the driving shaft 118 is driven by the motor.

  Next, as shown in FIG. 4B, in order to switch the developing function to the developing roller 109 disposed on the downstream side of the photosensitive drum, the cam member 131 is rotated counterclockwise about the rotation axis. . Therefore, the developing roller 109 disposed on the downstream side of the photosensitive drum 101 is in contact with the photosensitive drum 101 at a predetermined development gap with respect to the photosensitive drum 101 and is disposed on the upstream side of the photosensitive drum 101. The developed roller 108 is in a non-contact state with the developer on the photosensitive drum 101. At this time, as shown in FIG. 5B, the drive gear 119 is connected to the gear 126 of the developing roller 109. When the drive shaft 118 is driven by the motor, the gear 126 is driven via the drive gear 119, and the developing roller 109 rotates. At this time, since the driving gear 119 is not connected to the gear 123 of the developing roller 108, the developing roller 108 does not rotate even when the driving shaft 118 is driven by the motor.

  Here, when the drive gear 119 is driven in the direction of arrow a to drive the gear 123 on the shaft of the developing roller 108 in the direction of arrow c, the photosensitive drum 101 having the force d received by the gear 123 of the developing roller 108. The proximity / separation direction component dx is the separation direction of the photosensitive drum 101. The urging force by the urging means 113 is the separation direction of the photosensitive drum 101, and the movement of the developing roller 108 in the separation direction of the photosensitive drum 101 by the developing roller driving force is limited by the cam member 131. Further, when the drive gear 119 is driven in the direction of arrow a to drive the gear 126 on the shaft of the developing roller 109 in the direction of arrow c, the force d received by the gear 126 of the developing roller 109 is applied to the photosensitive drum 101. The proximity / separation direction component dx is the proximity direction of the photosensitive drum 101. The urging force by the urging means 114 is in the proximity direction of the photosensitive drum 101, and the movement of the developing roller 109 in the proximity direction of the photosensitive drum 101 by the developing roller driving force is limited by the cam member 131.

  According to the second embodiment having the above-described configuration, the driving force is transmitted from a single gear to the gears on the shafts of the two developing rollers. Cost reduction can be realized by reducing the number of parts.

  Next, the configuration of the developing device in the image forming apparatus according to the third embodiment of the present invention will be described with reference to FIG. 6 which is a schematic diagram showing the configuration of the developing function switching mechanism of the developing device. In the figure, the same reference numerals as those in FIG. 4 denote the same components. Further, the first image forming unit will be described.

  In FIG. 6, the cyan developing unit 104 and the magenta developing unit 105 are supported so as to be movable in the approaching / separating direction of the photosensitive drum 101 with respect to the side plate 110 of the first image forming unit. Between the cyan developing unit 104 and the magenta developing unit 105, the cyan developing unit 104 has an urging force component that urges the cyan developing unit 104 in the direction away from the photosensitive drum 101 with respect to the magenta developing unit 105. On the other hand, a biasing means 132 having a biasing force component that biases the magenta developing unit 105 in the proximity direction of the photosensitive drum 101 is provided. The roller member 115 on the shaft of the developing roller 108 is always in contact with the cam contact surface 131a of the cam member 131, so that the movement of the cyan developing unit 104 by the urging force of the urging means 132 is restricted. Further, the roller member 116 on the shaft of the developing roller 109 is always in contact with the cam contact surface 131b of the cam member 131, so that the movement of the magenta developing unit 105 by the urging force of the urging means 132 is restricted. Therefore, the photosensitive drum 101, the cyan developing unit 104, and the magenta developing unit 105 are supported and attached to the side plate of the first image forming unit (not shown) on the other end side in the axial direction of the photosensitive drum 101 with the same configuration. In addition, the roller member on the rotation shaft of the developing roller is in contact with a similar cam member, and the movement is restricted.

  According to the third embodiment having the above-described configuration, since the two developing units can be urged by a single urging unit, the size of the apparatus can be reduced by simplifying the configuration, and the number of parts can be reduced by reducing the number of parts. Cost reduction can be realized.

  Next, with respect to the configuration of the developing device in the image forming apparatus according to the fourth embodiment of the present invention, FIG. 7 is a schematic diagram showing the configuration of the developing function switching mechanism of the developing device and the configuration of the developing drive switching mechanism. This will be described with reference to FIG. In both figures, the same reference numerals as those in FIGS. 4 and 5 indicate the same components. Further, the first image forming unit will be described.

  In FIG. 7, the photosensitive drum 101 is rotatably supported with respect to the side plate 110 of the first image forming unit. The cyan developing unit 104 on the upstream side of the photosensitive drum 101 and the magenta developing unit 105 on the downstream side are photosensitive. The photosensitive drum 101 is supported so as to be movable in the approaching / separating direction of the photosensitive drum 101 and urged in the separating direction of the photosensitive drum 101. The roller members 115 and 116 at the ends of the developing rollers 108 and 109 are attached to the cam contact surface 141a of the cam member 141 supported so as to be rotatable coaxially with the shaft 120 of the photosensitive drum 101. The movement of the cyan developing unit 104 and the magenta developing unit 105 due to the force is restricted. Therefore, the photosensitive drum 101, the cyan developing unit 104, and the magenta developing unit 105 are supported and attached to the side plate of the first image forming unit (not shown) on the other end side in the axial direction of the photosensitive drum 101 with the same configuration. In addition, the roller member on the rotation shaft of the developing roller is in contact with a similar cam member, and the movement is restricted. In FIG. 7A, the developing roller 108 disposed on the upstream side of the photosensitive drum 101 has a developer contacting the photosensitive drum 101 at a predetermined developing gap with respect to the photosensitive drum 101, and the photosensitive drum 101. The developing roller 109 disposed on the downstream side of the 101 is in a non-contact state with the developer on the photosensitive drum 101. At this time, as shown in FIG. 8A, a drive gear 119 is fixed to a drive shaft 118 coupled to a motor (not shown) as a drive source provided on the apparatus main body side. The drive gear 119 is connected to the gear 123 of the developing roller 108 via a drive transmission gear 151 that is an intermediate idler gear that is rotatably disposed coaxially with the rotation shaft 120 of the photosensitive drum 101. When the drive shaft 118 is driven by the motor, the gear 123 is driven via the drive gear 119 and the drive transmission gear 151, and the developing roller 108 rotates. On the other hand, since the drive transmission gear 151 is not connected to the gear 126 of the developing roller 109 at this time, the developing roller 109 does not rotate even when the driving shaft 118 is driven by the motor.

  Next, as shown in FIG. 7B, in order to switch the developing function to the developing roller 109 disposed on the downstream side of the photosensitive drum 101, the cam member 141 is rotated counterclockwise about the rotation axis. Move. The developing roller 109 disposed on the downstream side of the photosensitive drum 101 is disposed on the upstream side of the photosensitive drum 101 while the developer contacts the photosensitive drum 101 with respect to the photosensitive drum 101 at a predetermined development gap. In the developing roller 108, the developer is not in contact with the photosensitive drum 101. At this time, as shown in FIG. 8B, the drive gear 119 is connected to the gear 126 of the developing roller 109 via the drive transmission gear 151 that is rotatably arranged coaxially with the rotation shaft 120 of the photosensitive drum 101. It is connected to. When the drive shaft 118 is driven by the motor, the gear 126 is driven via the drive gear 119 and the drive transmission gear 151, and the developing roller 109 rotates. On the other hand, since the drive transmission gear 151 is not connected to the gear 123 of the developing roller 108 at this time, the developing roller 108 does not rotate even when the driving shaft 118 is driven by the motor.

  Here, by driving the drive gear 119 in the direction of arrow a, the drive transmission gear 151 is driven in the direction of arrow b, and the gear 123 on the shaft of the developing roller 108 or the gear 126 on the shaft of the developing roller 109 is arrowed. When driven in the direction c, the force d received by the gear 123 of the developing roller 108 or the gear 126 of the developing roller 109 has a component dx in the separation direction of the photosensitive drum 101. On the other hand, the developing unit is urged in the separating direction of the photosensitive drum 101 by the urging means 113 and 114, and the movement of the developing unit in the separating direction of the photosensitive drum 101 is restricted by the cam member 141.

  According to the fourth embodiment having the above-described configuration, the cam member that defines the distance between the photosensitive drum and the developing roller is provided on the same axis of the photosensitive drum, thereby defining the developing gap. It is possible to increase the development gap accuracy by reducing the number of points, as well as saving space by simplifying the configuration and reducing the cost by reducing the number of parts. In addition, the cam switching member that defines the development gap and the drive transmission gear that transmits the development driving force are coaxial, so that the development switching operation is achieved by reducing the number of parts that define the positional accuracy between the developing roller gear and the drive transmission gear. Can improve reliability.

  Next, with respect to the configuration of the developing device in the image forming apparatus according to the fifth embodiment of the present invention, FIG. 9 is a schematic diagram showing the configuration of the developing function switching mechanism of the developing device and the configuration of the developing drive switching mechanism. This will be described with reference to FIG. In both figures, the same reference numerals as those in FIGS. 2 and 3 indicate the same components. Further, the first image forming unit will be described.

  In FIG. 9A, the developing roller 108 disposed on the upstream side of the photosensitive drum 101 is in contact with the photosensitive drum 101 at a predetermined developing gap with respect to the photosensitive drum 101, and the photosensitive drum 101. The developing roller 109 disposed on the downstream side of the 101 is in a non-contact state with the developer on the photosensitive drum 101. At this time, in FIG. 10A, the driving gear 119 is connected to the gear 123 of the developing roller 108 via the driving transmission gear 121, and when the driving shaft 118 is driven, the developing roller 108 rotates. On the other hand, since the drive transmission gear 124 connected to the drive gear 119 at this time is not connected to the gear 126 of the developing roller 109, the developing roller 109 does not rotate even if the drive shaft 118 is driven.

  9B, in order to stop the developing function of the developing roller 108 on the upstream side of the photosensitive drum 101, the cam member 161 is rotated clockwise about the rotation axis. Therefore, the developer is not in contact with the photosensitive drum 101 on the developing roller 108 on the upstream side of the photosensitive drum 101 and the developing roller 109 on the downstream side of the photosensitive drum 101. At this time, as shown in FIG. 10B, the drive gear 119 is connected to the drive transmission gears 121 and 124. The drive transmission gears 121 and 124 are the gear 123 of the developing roller 108 and the gear of the developing roller 109. 126, the developing rollers 108 and 109 do not rotate even when the drive shaft 118 is driven.

  Next, in FIG. 9C, in order to make the developing function of the developing roller 109 on the downstream side of the photosensitive drum 101 effective, the cam member 161 is further rotated clockwise about the rotation axis. Therefore, the developing roller 109 on the downstream side of the photoconductive drum 101 is in contact with the photoconductive drum 101 at a predetermined development gap with respect to the photoconductive drum 101, and the developing roller 109 is disposed on the upstream side of the photoconductive drum 101. In the roller 108, the developer is not in contact with the photosensitive drum 101. At this time, as shown in FIG. 10C, the driving gear 119 is connected to the gear 126 of the developing roller 109 via the driving transmission gear 124, and when the driving shaft 118 is driven, the developing roller 109 rotates. To do. On the other hand, since the drive transmission gear 121 connected to the drive gear 119 is not connected to the gear 123 of the developing roller 108, the developing roller 108 does not rotate even if the drive shaft 118 is driven.

  Note that when the operation of the first image forming unit including the cyan developing unit and the magenta developing unit is paused when outputting a black and white image, in the conventional method, both developing rollers are in a non-developing state. When the toner is in the developing state, the other developing roller is separated from the photoreceptor more than necessary, and it is inevitable that the apparatus becomes large and the developing state switching time becomes long. However, according to the present embodiment, it is possible to effectively utilize the configuration in which the upper and lower developing units are separate and can be moved and positioned independently, and the retracting interval of the developing roller can be minimized. This makes it possible to reduce the size of the apparatus and speed up the development switching operation.

  Further, according to the fifth embodiment, there is a state in which both the developing rollers have a non-developing interval between the photosensitive drums during the developing function switching operation from one developing roller to the other developing roller. The output image switching from the color image to the black and white image and the output image switching from the black and white image to the color image can be performed at high speed, and an effective product specification can be realized for users who have the same color image and monochrome image output ratio.

  Here, as shown in FIG. 11A, when the cam member 171 rotates, one of the developing rollers is in a developing state and the other developing roller is in a non-developing state. As shown in FIG. 11 (b), the other developing roller is in the developing state and one developing means is in the non-developing state while both developing rollers are in the non-developing state. By forming the cam abutting surface having a state in which the developing drum is in a state where the developing function is switched from one developing roller to the other developing roller, the photosensitive drums of both developing rollers have a non-developing interval. Since there is no state, the development color switching operation time at the time of continuous color image output can be shortened, and the image output time can be increased, so that it is possible to realize a product specification effective for a user with a high color ratio.

  FIG. 12 is a schematic diagram showing the configuration of the developing function switching mechanism of the developing device in the image forming apparatus according to the sixth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 denote the same components. The photosensitive drum 101 is supported by the side plate 110 of the first image forming unit so as to be rotatable about the axis of the photosensitive drum 101. A bearing 181 for rotatably supporting the developing roller 108 on the upstream side of the photosensitive drum 101 with respect to the cyan developing unit 104 and a developing roller 109 on the downstream side of the photosensitive drum 101 with respect to the magenta developing unit 109 are rotatably supported. The bearing 182 is supported on the side plate 110 of the first image forming unit by the support units 111 and 112 so as to be movable in the approaching / separating direction of the photosensitive drum 101. Further, the bearing 181 of the cyan developing unit 104 and the bearing 182 of the magenta developing unit 105 are urged toward the side of the photosensitive drum 101 by the urging means 113 and 114 with respect to the side plate 110 of the first image forming unit. Yes. The bearing 181 of the cyan developing unit 104 and the bearing 182 of the magenta developing unit 105 are always in contact with the cam contact surface 117a of the cam member 117 having a rotation axis parallel to the shaft 120 of the photosensitive drum 101, so Movement of the cyan developing unit 104 and the magenta developing unit 105 by the urging force of the urging means 113 and 114 is restricted. The photosensitive drum 101, the cyan developing unit 104, and the magenta developing unit 105 are supported and urged with the same configuration with respect to the side plate 110 of the first image forming unit (not shown) on the other end side in the axial direction of the photosensitive drum 101. At the same time, the bearing that rotatably supports the developing roller comes into contact with a similar cam member, so that the movement is restricted.

  According to the sixth embodiment having the above-described configuration, the cam member 117 rotates at both ends of the photosensitive drum 101 in the axial direction, and the bearings 181 and 182 contact with the rotating shaft of the cam member 117. By changing the distance to the cam contact surface 117a that comes into contact, the distance from the rotation shaft of the cam member 117 to the shaft of each developing roller changes, and the shaft from each developing roller to the shaft 120 of the photosensitive drum 101 changes. As the distance changes, the distance between the photosensitive drum 101 and each of the developing rollers 108 and 109, the so-called development gap, changes. Therefore, since the outer periphery of the bearing that supports the developing roller directly contacts the cam member, it is possible to increase the accuracy of the developing gap by reducing the number of parts that define the developing gap between the photosensitive drum and each developing roller. Space can be saved by simplifying the configuration, and cost can be reduced by reducing the number of parts. In addition, since the outer circumference of the bearing that supports the developing roller is directly supported, the developing gap attitude accuracy is improved by improving the developing roller attitude accuracy and the supporting rigidity, and the cost is reduced by simplifying the configuration and reducing the number of parts. Can be realized. In addition, since the outer periphery of the bearing that supports the developing roller is directly urged, the developing unit can be brought into constant contact with the cam even if the rigidity of the developing unit is reduced, resulting in lower costs due to reduced component costs. Can be realized.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

1 is a schematic cross-sectional view illustrating a configuration of a main part of an image forming apparatus to which the present invention is applied. 1 is a schematic diagram illustrating a configuration of a developing function switching mechanism of a developing device in an image forming apparatus according to a first exemplary embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a development drive switching mechanism of the development device in the image forming apparatus according to the first exemplary embodiment. FIG. 10 is a schematic diagram illustrating a configuration of a developing function switching mechanism of a developing device in an image forming apparatus according to a second exemplary embodiment of the present invention. FIG. 10 is a schematic diagram illustrating a configuration of a development drive switching mechanism of a development device in an image forming apparatus according to a second exemplary embodiment. FIG. 10 is a schematic diagram illustrating a configuration of a developing function switching mechanism of a developing device in an image forming apparatus according to a third exemplary embodiment of the present invention. It is the schematic which shows the structure of the developing function switching mechanism of the developing device in the image forming apparatus which concerns on the 4th Embodiment of this invention. It is the schematic which shows the structure of the developing drive switching mechanism of the developing device in the image forming apparatus which concerns on the example of 4th Embodiment. It is the schematic which shows the structure of the developing function switching mechanism of the developing device in the image forming apparatus which concerns on the 5th Example of this invention. FIG. 10 is a schematic diagram illustrating a configuration of a development drive switching mechanism of a development device in an image forming apparatus according to a fifth exemplary embodiment. FIG. 10 is a schematic diagram illustrating another switching operation of the developing function switching mechanism of the developing device in the image forming apparatus according to the fifth embodiment. It is the schematic which shows the structure of the developing function switching mechanism of the developing device in the image forming apparatus which concerns on the 6th Embodiment of this invention.

Explanation of symbols

111, 112; support means, 113, 114, 132; biasing means,
115, 116; roller members,
117, 131, 141, 161, 171; cam member;
117a, 131a, 131b, 141a, 161a, 171a; cam contact surface;
118; drive shaft, 119; drive gear, 120; rotating shaft,
121, 124, 151; drive transmission gear, 122, 125; shaft,
123, 126; gears, 181, 182; bearings.

Claims (12)

A plurality of developing means for visualizing the latent images of the image carrier with different color developers in a state of being opposed to each other and adjacent to each other around the rotationally driven image carrier. At least one image forming unit provided, and when the color is switched in the image forming unit, the developing unit is developed from one of the developing units to the other developing unit 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 primary-transferred sequentially to the intermediate transfer member, and the transfer image on the intermediate transfer member is secondarily transferred to the recording material. In an image forming apparatus for forming a recorded image,
A supporting means for supporting each of the one developing means and the other developing means so as to be movable at least in the proximity / separation direction of the image carrier;
An urging means for urging the developing means in one of the movable directions;
The movement of the developing means in the movable direction by the urging force of the urging means is always restricted, the distance between one of the developing means and the image carrier is in the developing state, and the other developing means and the image carrier are 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. The cam member having a cam contact surface for changing the distance between each developing means and the image carrier at the second position formed at both ends in the rotational axis direction on an axis parallel to the rotational axis of the image carrier. Provided,
One of the developing units and the other of the developing units are supported so as to be rotatable about an axis parallel to the rotation axis of the image carrier. When the driven member is fixed on the same axis and the cam member is rotated, the one or the other developing means and the image carrier are in the development state. When the distance between one or the other developing means and the image carrier is in a non-developing state, the driving force is in a non-developing state with the driven member of one or the other developing means. An image forming apparatus comprising a transmission unit.   The driving force transmitting means drives the driven member of one or the other of the developing means in a driving force transmitting state, out of the driving force acting on the driven member in the moving direction of the one or the other developing means. The image forming apparatus according to claim 1, wherein the force is provided at a position where the force is the same as a biasing direction of the biasing unit.   The urging means urges the one developing means and the other developing means in different directions with respect to the movable direction of the developing means, and is fixed to the one developing means and the other developing means. The image forming apparatus according to claim 1, wherein the driving member is provided so as to be in a driving force transmission state with respect to the same driving force transmission unit in the driving force transmission state or the driving force non-transmission state.   The urging means is provided between one of the developing means and the other developing means so as to urge the other developing means with respect to one of the developing means in the movable direction of each developing means. The image forming apparatus according to claim 3.   The image forming apparatus according to claim 1, wherein the cam member is provided so as to be rotatable coaxially with a rotation axis of the image carrier.   The image forming apparatus according to claim 1, wherein the driving force transmission unit is coaxially rotatable with respect to a rotation axis of the image carrier.   The cam member is in a third position where the distance between the 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. The image forming apparatus according to claim 1, further comprising: a cam contact surface that changes a distance between each developing unit and the image carrier.   The cam member is rotated between the cam contact surface at the first position and the cam contact surface at the second position by rotation of the cam member. The image forming apparatus according to claim 7, wherein the image forming apparatus has a contact surface.   The cam member is rotated between the cam contact surface at the first position and the cam contact surface at the third position by rotation of the cam member. The image forming apparatus according to claim 7, wherein the image forming apparatus has a contact surface.   In order to always restrict the movement of each developing means in the proximity direction of the image carrier by the urging force of the urging means, the developing means is placed on the cam bearing surface of the cam member. The image forming apparatus according to claim 1, wherein a bearing member that rotatably supports an axis parallel to the rotation axis of the body abuts.   The image forming apparatus according to claim 10, wherein the support means supports the bearing member.   The image forming apparatus according to claim 10, wherein the urging unit urges each of the developing units in a proximity direction of the image carrier and urges the bearing member.

Images