JP2006207791A - Transmission mechanism and image forming apparatus provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a power controlling mechanism capable of maintaining disconnection and connection conditions of a clutch mechanism without continuing to electrify a motor. <P>SOLUTION: A transmission mechanism is configured so as to mount to make it possible to slide a slide member 62 with respect to structure 61 on both sides and to make it possible to move leftwards by a disengagement hook 65 and rightwards by a cam mechanism 64. As the slide member 62 slides on both sides, the clutch mechanisms 70a-70c is configured so that an arm 72 turns on both sides and disconnection and connection conditions to an output gear 75 of power of external driving motor 72 are switched. The slide member 63 is maintained in such position that the clutch mechanism is in the disconnection condition when a protuberance 63a for locking the lock member 63 is engaging to a lock hole 63a of the structure 61 and in such position that the clutch mechanism is in the connection condition by an urging means 68 if engagement with the lock hole 63a of the protuberance 63a for lock is disengaged even if continuing to electrify to a cam mechanism driving motor 64a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power transmission device capable of simultaneously controlling one or more clutch mechanisms in a disconnected state and a connected state, and an image forming apparatus including the same.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, an apparatus capable of forming a color image is often used. As such an image forming apparatus, a tandem type is known in which image forming units for forming images of each color of yellow, cyan, magenta and black are arranged in series in the rotation direction of an intermediate transfer belt.

  Each image forming unit includes a photosensitive drum carrying an electrostatic latent image and a toner image of an image to be formed, and a developing device for developing the electrostatic latent image on the photosensitive drum as a toner image. . A developing roller is provided inside the developing device, and the developing roller rotates to convey the toner to the surface of the photosensitive drum. When forming a color image, the toner images formed by the image forming units of the respective colors are transferred so as to overlap each other on the intermediate transfer belt, and the overlapping toner images are transferred from the intermediate transfer belt to a sheet. On the other hand, when forming a black and white image, only a black image forming unit forms a toner image, and this toner image is transferred to a sheet via an intermediate transfer belt.

  In conventional tandem type image forming apparatuses, the photosensitive drums of all image forming units are rotated in order to stably rotate the intermediate transfer belt when forming a color image or a black and white image. With this, the developing roller rotates. Here, the toner conveyed through the developing device can develop the electrostatic latent image on the photosensitive drum by being charged, but the characteristics such as the charge amount change when the toner is stirred by vibration or conveyance. Therefore, when mainly forming a black-and-white image, the toners of the respective colors in the image forming units other than black are swirled by the developing roller and charged more than necessary and deteriorated, although the frequency of use is low.

For this reason, in Patent Document 1, a tandem type image forming apparatus includes a pivotable arm to which a drive control gear is attached, and the arm can be pivoted to disconnect and connect power from one drive source. The one provided with a simple clutch mechanism has been proposed. As a result, when a black and white image is formed, the developing roller of all image forming units other than black is not transmitted with the power of the driving source, and the rotation is stopped, so that deterioration of the toner other than black that is not frequently used is suppressed. Is possible.
JP 2002-6579 A (6th page, FIG. 2)

  However, in the clutch mechanism using the pivotable arm proposed in Patent Document 1, it is necessary to continue energizing the means for pivoting the arm such as a solenoid in order to maintain the disconnected state or the connected state. Has occurred.

  Accordingly, an object of the present invention is to provide a power control mechanism that can maintain the disconnected state and connected state of the clutch mechanism without energization, and an image forming apparatus including the same.

  (1) In order to achieve the above object, the power transmission mechanism of the present invention slides between at least one clutch mechanism and an engagement position and a disengagement position with respect to the clutch mechanism. A sliding member for intermittently holding the sliding member, a frame for holding the sliding member so as to be slidable, a biasing means for biasing the sliding member to an engagement position with respect to the clutch mechanism, and a mechanism for engaging the sliding member with respect to the clutch mechanism. A locking member that locks in the unlocking position, a cam and a disengagement hook that can rotate about the cam, and a cam mechanism that displaces the locking member between the locking position and the unlocking position; and In the power transmission mechanism including the cam drive motor to be rotated, the lock member is pivotably mounted on the slide member around one end. The cam is provided with a locking projection and a disengagement hook engaging portion, and when the cam is rotated in one direction by the cam drive motor, the cam contacts the free end of the locking member, and the slide member is moved together with the locking member. The slide mechanism is slid in the direction of the disengagement position with respect to the clutch mechanism, and at the same time, the lock member is rotated in the direction of the lock position, and the lock protrusion is engaged with the lock hole provided in the frame body, thereby moving the slide member. When held in the disengagement position with respect to the clutch mechanism and rotated in the other direction by the cam drive motor, the free end of the lock member is contacted, the lock member is rotated toward the unlock position, and the lock The protrusion for release is disengaged from the engagement with the lock hole, the disengagement hook is engaged with the disengagement hook engagement portion of the lock member, and the It characterized in that for moving the slide member with click member in a direction for displacing the engaged position with respect to the clutch mechanism.

  (2) In the power transmission mechanism configured as described above, the clutch mechanism includes an external output motor, a drive gear connected to the shaft of the external output motor, and an axis of the external output motor. An arm provided movably, an idle gear rotatably attached to the arm so as to mesh with the drive gear, and an output gear that rotates by being connected to the idle gear, The power cutting posture is taken by engagement with the slide member, and the power transmission posture is taken by disengaging the engagement. When the power cutting posture is taken, the idle gear is separated from the output gear and the clutch mechanism is cut off. When taking a power transmission posture, the idle gear is engaged with the output gear to bring the clutch mechanism into a connected state.

  (3) The image forming apparatus of the present invention includes the power transmission mechanism described above, and a developing roller provided inside the developing device is connected to the output gear.

  (1) According to the present invention, one or more clutch mechanisms can be operated at a time by one cam drive motor and slide member, and the cam drive motor is continuously energized by the biasing means and the lock member. The slide member can be held at the engagement position and the engagement release position with respect to the clutch mechanism without any problem. In addition, since the disengagement hook engages with the disengagement hook engaging portion provided on the lock member by the rotation of the cam and moves in the direction of displacing the slide member to the engagement position with respect to the clutch mechanism together with the lock member, the idle gear is Even when there is a large bite load generated by the drive torque received from the drive gear and the output gear in a direction that prevents the arm from changing its posture to the power cut posture, the slide member is biased to the engagement position with respect to the clutch mechanism. Without increasing the urging force of the urging means, the posture of the arm can be easily changed by the urging means and the disengaging hook. Further, since it is not necessary to increase the urging force of the urging means, it is not necessary to increase the force that opposes the urging force of the urging means when the slide member is displaced to the disengagement position with respect to the clutch mechanism. The drive motor can be made small and inexpensive with a small output.

  (2) Also, according to the present invention, the clutch mechanism is connected or disconnected when the arm of the clutch mechanism is disengaged from or engaged with the slide member and rotated, and is rotatably attached to the arm of the clutch mechanism. Since the idle gear is engaged with the output gear or separated from the output gear, the power of the external output motor can be transmitted to the output gear or disconnected.

  (3) According to the present invention, the output gear of the clutch mechanism is connected to the developing roller provided inside the developing device other than black so that the power of the external output motor is always transmitted to the photosensitive drum. Thus, the developing roller can be rotated or stopped while the photosensitive drum is rotated. Therefore, this power transmission mechanism is used to rotate all developing rollers and photosensitive drums including black when forming color images, and to rotate developing rollers other than black while rotating all photosensitive drums when forming black and white images. It can be stopped, and toner other than black can be suppressed from being charged and charged by the developing roller more than necessary.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of an image forming apparatus provided with a mechanism according to an embodiment of the present invention, FIG. 2 is a partially enlarged view in the vicinity of the image forming unit, and FIG. 3 is a schematic configuration of a power transmission mechanism in which an arm takes a power cutting posture. 4 is a schematic configuration diagram of a power transmission mechanism in which the arm takes a power transmission posture, FIG. 5 is a partially enlarged view around the cam mechanism of the power transmission mechanism in which the arm takes a power cutting posture, and FIG. 6 is a power transmission posture of the arm. It is the elements on larger scale around the cam mechanism of the power transmission mechanism which takes.

  First, each part of the printer 10 will be described. Inside the printer 10, a control unit 12, a paper feeding unit 30, an image forming unit 40, and a fixing unit 80 are provided. The control unit 12 controls operations of the printer 10 such as a paper transport operation and an image forming operation.

  The paper feeding unit 30 will be described. The paper feed unit 30 includes a paper feed cassette 31, a paper feed roller 32, a transport roller pair 33 and a registration roller pair 34. The paper feed cassette 31 accommodates the paper P and is disposed below the printer 10. From here, the paper P is sent one by one to the paper transport path 36 by the paper feed roller 32, and transported by the transport roller pair 33 and the registration roller pair 34.

  Next, the image forming unit 40 will be described. The image forming unit 40 includes yellow, cyan, magenta and black image forming units 50 a, 50 b, 50 c and 50 d, a primary transfer roller 41, an intermediate transfer belt 42 and a belt cleaner 47.

  The image forming units 50a, 50b, 50c and 50d are arranged in tandem, and the arrangement order can be changed. One primary transfer roller 41 is disposed at a position facing each of the image forming units 50a, 50b, 50c and 50d with the intermediate transfer belt 42 therebetween.

  The intermediate transfer belt 42 is stretched and supported by a driving roller 45 and driven rollers 46a and 46b. All the image forming units 50 a, 50 b, 50 c and 50 d are in contact with the outer surface on the upper side of the intermediate transfer belt 42. The support roller 55a drives the intermediate transfer belt 42, and the intermediate transfer belt 42 rotates clockwise (in the direction of the arrow) in FIG. Here, in the present embodiment, the number of driven rollers 46a and 46b is two. However, as long as the image forming units 50a, 50b, 50c and 50d are in contact with the intermediate transfer belt 42, one or more driven rollers may be used.

  The belt cleaner 47 removes toner that has not been transferred to the paper P from the intermediate transfer belt 42, and includes a blade that contacts the intermediate transfer belt 42.

  The image forming units 50a, 50b, 50c and 50d all have the same structure, and as shown in the partially enlarged view in the vicinity of the image forming unit 50a in FIG. 2, in accordance with the rotation of the intermediate transfer belt 42. Around the rotating photosensitive drum 51, a contact portion with the charger 52, the LED print head 53, the developing device 54, and the intermediate transfer belt 42 is sandwiched in accordance with the rotation direction (arrow direction) from above the photosensitive drum 51. Thus, the cleaning device 55 and the static eliminator 56 are arranged as peripheral elements.

  Finally, the fixing unit 80 will be described. In the fixing unit 80, the fixing roller 81 and the pressure roller 82 are pressed against each other, and the toner image transferred onto the paper P is heated and pressed to be fixed on the paper P.

  Next, an image forming operation will be described. When a user issues an image formation instruction from an external computer (not shown) connected to the main body 10 directly or via a network, the control unit 12 receives the instruction and operates each unit. 1 and 2, the intermediate transfer belt 42 is rotated clockwise (in the direction of the arrow) by the driving roller 45, and the photosensitive drums 51 of the image forming units 50a, 50b, 50c, and 50d that are in contact therewith correspond to each other. Rotate counterclockwise (arrow direction). When the photosensitive drum 51 rotates, the surface of the photosensitive drum 51 is first uniformly charged by the charger 52. Next, based on the electrical signal of the document image sent from the external computer, the light emitted from the LED print head 53 composed of a large number of LEDs is applied to the portion of the image formed on the paper P or a portion other than the image. Corresponding charges are erased, and an electrostatic latent image is formed on the surface of the photosensitive drum 51. Then, toner is supplied from the toner container 54b onto the photosensitive drum 51 by the developing roller 54a provided in the developing device 54, and the electrostatic latent image is visualized as a toner image.

  When the photosensitive drum 51 further rotates and the toner image comes to a position facing the primary transfer roller 41 with the intermediate transfer belt 42 interposed therebetween, a bias voltage having a polarity opposite to the toner charging polarity is applied to the primary transfer roller 41. The toner image is applied to the intermediate transfer belt 42 from the photosensitive drum 51. Residual toner that has not been transferred is removed by the cleaning device 55, and the charge remaining on the surface of the photosensitive drum 51 is removed by the static eliminator 56.

  Toner images are stacked on the intermediate transfer belt 42 in the order of the image forming units 50a to 50b, 50c, and 50d, and the intermediate transfer belt 42 is further rotated. The stacked toner images face the secondary transfer roller 43. When the position reaches the position, the sheet P is conveyed along the sheet conveyance path 36 between the intermediate transfer belt 42 and the secondary transfer roller 43 accordingly. At this time, a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 43, and the stacked toner images are transferred from the intermediate transfer belt 42 to the paper P. Residual toner that has not been transferred onto the intermediate transfer belt 42 is removed from the intermediate transfer belt 42 by the belt cleaner 47. The sheet P on which the toner image has been transferred is conveyed to the fixing unit 80 and heated and pressed as described above to fix the toner image, and a discharge tray 85 provided above the printer 10 by the discharge roller pair 84. To be discharged.

  In the present embodiment, rotational power is transmitted to the photosensitive drum 51 and the developing roller 54a of each of the image forming units 50a, 50b, and 50c for yellow, cyan, and magenta by a power transmission mechanism 60 described below.

  The power transmission mechanism 60 is provided on the back side of the image forming unit 40 in FIG. 1, and as shown in FIGS. 3 and 4, a frame body 61, a slide member 62, a lock member 63, a cam mechanism 64, an urging force. Means 68 and three sets of clutch mechanisms 70a, 70b and 70c are provided.

  The frame 61 is made of a plate such as metal or plastic, and includes a vertical portion 61a and a horizontal portion 61b. 3 and 4 show a cross section of the horizontal portion 61b, and the horizontal portion 61b is provided with a groove 61c.

  A plurality of protrusions 62 a provided on the upper portion of the slide member 62 are engaged with the groove 61 c, so that the slide member 62 can slide with respect to the frame body 61. The frame body 61 and the slide member 62 are connected by an urging means 68 formed of a compression coil spring, and the slide member 62 is urged leftward with respect to the frame body 61 in FIGS.

  The slide member 62 is provided with engaging portions 62b that engage with arms 72 of clutch mechanisms 70a, 70b, and 70c, which will be described later, and each of the engaging portions 62b and the arms 72 is formed of a tension coil spring. They are connected by a biasing means 76. Further, the lock member 63 is rotatably attached with the fulcrum 63b as a fulcrum, and this lock member 63 is provided by a biasing means 67 comprising a tension coil spring attached between a disengagement hook 65 and the lock member 63 described later. The free end side of the lock member 63 is biased so as to rotate toward the upper lock position. A locking projection 63a is provided on the upper part of the free end side of the locking member 63, and a disengaging hook engaging portion 63c is provided at a position engaging with the engaging portion 65b of the disengaging hook 65 toward the front side of the drawing. Yes.

  The cam mechanism 64 meshes with the worm gear 64b, the cam drive motor 64a fixed to the vertical portion 61a of the frame 61 by the cam drive motor support member 65, the worm gear 64b attached to the rotating shaft of the cam drive motor 64a. The cam gear 64c is attached to the vertical portion 61a of the frame 61, and the cam 64d rotates integrally with the cam gear 64c. Since the cam drive motor 64a can rotate in any direction, the cam 64d can rotate in either the left or right direction in FIGS.

  The cam mechanism 64 includes a disengagement hook 65 having a ring portion 65a and an engagement portion 65b. The disengagement hook 65 is rotatably attached about the cam 64d by fitting the cam 64d into the ring portion 65a (see FIGS. 5 and 6). The disengagement hook 65 is urged by the urging means 67 on the engagement portion 65 b side upward, that is, in the direction of the disengagement hook engagement portion 63 c of the lock member 63. Since the ring portion 65a is provided so as not to cover a portion where the cam 64d contacts the free end of the lock member 63, contact between the cam 64d and the free end of the lock member 63 is not hindered. Further, since the thickness in the depth direction in FIG. 5 near the engaging portion 65b of the disengaging hook 65 is thinner than the thickness of the cam 64d in the same direction, the rotation of the lock member 63 is not hindered.

  Next, operations of the slide member 62, the lock member 63, and the cam mechanism 64 will be described. When the cam 64d rotates counterclockwise when the power transmission mechanism 60 is in the state shown in FIG. 3, the cam 64d contacts the free end of the lock member 63 and contacts the lock member 63 on the circumferential surface from the shaft of the cam 64d. As the distance to the portion becomes longer, the slide member 62 is moved in the right direction against the urging force of the urging means 68 together with the lock member 63. When the cam 64 further rotates, the lock member 63 is rotated upward by the urging force of the urging means 67, and the lock projection 63 a enters the lock hole 61 d provided in the horizontal portion 61 b of the frame body 61. Is the locked position.

  Thereafter, as the cam 64d further rotates and the distance from the shaft of the cam 64d to the portion in contact with the peripheral surface locking member 63 becomes shorter, the slide member 62 urged by the urging means 68 moves in the left direction. However, when the locking projection 63a engages with the lock hole 61d, it can no longer move to the left as shown in FIG. 4, and becomes a disengagement position for the clutch mechanism. At this time, as shown in FIG. 6, when the locking projection 63a and the lock hole 61d are engaged, the disengagement hook engaging portion 63c is moved to an upper position where it is not engaged with the engaging portion 65b. The hook 65 does not affect the operation of the power transmission mechanism 60.

  Thus, since the slide member 64 is in the disengagement position with respect to the clutch mechanism while the cam 64d rotates once counterclockwise, it is not necessary to continue energizing the cam drive motor 64a. Thereafter, even if the cam 64d continues to rotate in the same direction, the slide member 64 may move rightward from the disengagement position with respect to the clutch mechanism by the cam 64d, but the engagement with the clutch mechanism shown in FIG. There is no return to position.

  On the other hand, when the cam 64d rotates clockwise when the power transmission mechanism 60 is engaged with the lock projection 63a and the lock hole 61d as shown in FIG. 4, only when the cam 64d rotates clockwise. The free end of the lock member 63 is caught by the protrusion provided on the peripheral surface of the cam 64d so as to be caught, the free end of the lock member 63 is pulled down, the engagement between the lock protrusion 63a and the lock hole 61d is released, and The slide member 62 urged by the urging means 68 moves to the left and becomes an engagement position with respect to the clutch mechanism shown in FIG.

  Thus, since the slide member 64 is in the engagement position with respect to the clutch mechanism while the cam 64d makes one clockwise rotation, it is not necessary to continue energizing the cam drive motor 64a. Here, the lock member 63 tries to rotate upward by the urging means 67, but comes into contact with the horizontal portion 61b of the frame body 61 and cannot be rotated any more, and becomes the unlocked position. Even if the cam 64d continues to rotate in the same direction thereafter, the locking member 63 is pulled downward by the protrusion of the cam 64d. When the protrusion is removed, the biasing means 67 returns the lock member 63 to the unlocked position, and the slide The member 62 does not move from the engagement position with respect to the clutch mechanism.

  Next, the clutch mechanisms 70a, 70b and 70c will be described. The clutch mechanisms 70a, 70b, and 70c have the same structure, and include an external output motor 71 fixed to the vertical portion 61a of the frame 61, a drive gear 73 connected to the shaft of the external output motor 71, and an external output motor. An arm 72 rotatably attached about the axis of 71, an idle gear 74 rotatably attached to the arm 72, and an output gear rotatably attached to a plate 78 fixed to the external output motor 71. 75.

  In the state shown in FIG. 3, the arm 72 is biased so as to rotate counterclockwise by engaging with the engaging portion 62b of the slide member 62 biased to the engaging position with respect to the clutch mechanism. Since the clutch mechanisms 70 a, 70 b and 70 c are in a disconnected state in which the idle gear 74 and the output gear 75 are separated from each other, the power of the external output motor 71 is not transmitted to the output gear 75.

  Further, when the cam 64d rotates counterclockwise in the state shown in FIG. 3, as described above, the slide member 62 moves to the engagement release position with respect to the clutch mechanism in the right direction. The arm 72 is pulled by the urging means 76 attached so as to connect the arm 72 and the engaging portion 62b of the slide member 62, and rotates clockwise from the state shown in FIG. Since the clutch mechanisms 70a, 70b and 70c are in a connected state in which the idle gear 74 and the output gear 75 are engaged as shown in FIG. 4, the power of the external output motor 71 is transmitted to the output gear.

  When the cam 64d rotates clockwise in the state shown in FIG. 4, as described above, the slide member 62 moves to the engagement position with respect to the clutch mechanism in the left direction, and the arm 72 engages with the engagement portion 62b of the slide member 62. Then, the clutch mechanism 70a, 70b and 70c are in the disconnected state shown in FIG.

  At this time, if the drive gear 73 rotates clockwise in FIG. 5, the arm 73 causes the arm 73 to rotate clockwise by the drive torque that the idle gear 74 receives from the drive gear 73 and the output gear 75. In other words, the biting load is generated in a direction that prevents the power changing posture from being changed.

  When this bite load is large, even if the engagement between the locking projection 63a and the lock hole 61d is released, the posture of the slide member 63 biased by the biasing means 68 cannot be changed while the arm 72 remains in the power transmission posture. Sometimes. However, when the cam 64d further rotates, the disengagement hook 65 moves to the left as shown in FIG. 5, and the engagement portion 65b and the disengagement hook engagement portion 63c are engaged to move the slide member 62 together with the lock member 63 to the left. The arm 72 can be slid in the direction to change the posture from the power transmission posture to the power cutting posture.

  When the biasing force of the biasing means 68 is B and the power of the cam drive motor 64a is C, the cam drive motor 64a slides the cam 64d when the clutch mechanisms 70a, 70b and 70c are changed from the disconnected state to the connected state. Since the member 62 must be rotated against the urging force of the urging means 68, C ≧ B must be satisfied.

  Assuming that the bite load is A, when there is no disengagement hook 65, B ≧ A must be satisfied in order to counter the bite load only by the urging force of the urging means 68, so the relationship C ≧ B ≧ A is established. And both B and C must be greater than or equal to A.

  However, by providing the disengagement hook 65, it is possible to counter the biting load by the urging force of the urging means 68 and the power of the cam drive motor 64a, and therefore B + C ≧ A, so C ≧ (B + C) / 2 ≧ It suffices if the A / 2 relationship holds. At this time, if C is the minimum A / 2, then B = A / 2.

  Therefore, even if the urging means 68 is not so large that the urging force B can counter the biting load A, the clutch mechanisms 70a, 70b are driven by the power C of the cam drive motor 64a and the urging force B of the urging means 68. And 70c can be changed from the connected state in which the idle gear 74 and the output gear 75 are engaged to the disconnected state. When the clutch mechanisms 70a, 70b and 70c are changed from the disconnected state to the connected state, the cam drive motor 64a must rotate the cam 64d against the biasing force B of the biasing means 68. However, since it is not necessary to increase the urging force of the urging means 68, that is, the elastic coefficient, the cam drive motor 64a can use a small and inexpensive output with a small output.

  The clutch mechanisms 70a, 70b and 70c correspond to the image forming units 50a, 50b and 50c for yellow, cyan and magenta, respectively. The photosensitive drums 51 of these three sets of image forming units 50a, 50b, and 50c are rotated by the power of the external output motor 71 transmitted by gears (not shown) connected to the corresponding drive gears 73. Similarly, the developing roller 54a is attached to the corresponding output gear 75, and the power of the external output motor 71 to the three developing rollers 54a is simultaneously transmitted and disconnected by the operation of the cam drive motor 64a. The black image forming unit 50d is not provided with such a clutch mechanism, and the power of an external output motor (not shown) is always transmitted to the photosensitive drum 51 and the developing roller 54a.

  Here, in FIG. 3 and FIG. 4, each clutch mechanism 70a, 70b and 70c is provided with an external output motor 71 for driving the respective drive gear 73, but by combining the gears, a plurality of drive gears 73 are provided. You may drive with one external output motor.

  When forming a color image in the printer 10, the control unit 12 controls the cam drive motor 64 a to rotate the cam 64 d once counterclockwise, and the lock member 63 moves the slide member 62 to the disengagement position with respect to the clutch mechanism. Lock it. As a result, the clutch mechanisms 70a, 70b and 70c remain connected even when the cam drive motor 64a is not energized, and the photosensitive drums 51 and the document rollers 54a of all the image forming units 50a, 50b, 50c and 50d are maintained. It is rotated by the power of the corresponding external output motor.

  When a monochrome image is formed, similarly, the control unit controls the cam drive motor 64a to rotate the cam 64d once in the clockwise direction to release the locked state by the lock member 63 and to urge the slide member 62. The engagement position with respect to the clutch mechanism is set by the biasing force of the means 68. As a result, the clutch mechanisms 70a, 70b and 70c remain disconnected even when the cam drive motor 64a is not energized, and the photosensitive drums 51 of the image forming units 50a, 50b and 50c for yellow, cyan and magenta are externally connected. Although it is rotated by the power of the output motor 71, the developing roller 54a does not rotate because this power is not transmitted. Naturally, the image forming unit 50d for black is rotated by an external output motor (not shown) for both the photosensitive drum 51 and the developing roller 54a.

  By configuring as described above, the disconnection state and the connection state of the plurality of clutch mechanisms 70a, 70b, and 70c can be switched by short-time energization to one cam drive motor 64a, and these can be performed without energization. Can be maintained. Further, in the printer 10, yellow and cyan that are not used when a monochrome image is formed while the intermediate transfer belt 42 is stably rotated by the photosensitive drums 51 of all the image forming units 50a, 50b, 50c, and 50d. In addition, since magenta toner is not stirred by the developing roller 54a, deterioration due to charging can be suppressed.

  The present invention can be used for a power transmission mechanism that simultaneously switches one or more clutch mechanisms to a connected state or a disconnected state.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. Partial enlarged view near the image forming unit Schematic configuration diagram of a power transmission mechanism where the arm takes a power cutting posture Schematic configuration diagram of a power transmission mechanism in which the arm takes a power transmission posture Partial enlarged view of the periphery of the cam mechanism of the power transmission mechanism where the arm takes the power cutting posture Partial enlarged view around the cam mechanism of the power transmission mechanism where the arm takes the power transmission posture

Explanation of symbols

54 Developing Unit 54a Developing Roller 60 Power Transmission Mechanism 61 Frame 61a Lock Hole 62 Slide Member 63 Lock Member 63a Locking Projection 63c Disengagement Hook Engagement Section 64 Cam Mechanism 64a Cam Drive Motor 64d Cam 65 Disengagement Hook 68 Energizing Means 70a Clutch Mechanism 70b Clutch mechanism 70c Clutch mechanism 71 External output motor 72 Arm 73 Drive gear 74 Idle gear 75 Output gear

Claims (3)

At least one clutch mechanism, a slide member that slides between an engagement position and an engagement release position with respect to the clutch mechanism to intermittently connect the clutch mechanism, and a frame that holds the slide member so as to be slidable A body, a biasing means for biasing the slide member to an engagement position with respect to the clutch mechanism, a lock member for locking the slide member at a disengagement position with respect to the clutch mechanism, a cam, and the cam as a shaft. In a power transmission mechanism comprising a movable disengagement hook, a cam mechanism that displaces the lock member between a lock position and a lock release position, and a cam drive motor that rotates the cam.
The lock member is attached to the slide member so as to be rotatable around one end and includes a lock projection and a disengagement hook engaging portion.
When the cam rotates in one direction by the cam drive motor, the cam contacts the free end of the lock member, and slides the slide member in the direction of the disengagement position with respect to the clutch mechanism together with the lock member. The member is rotated in the lock position direction, the lock projection is engaged with a lock hole provided in the frame body, and the slide member is held at the disengagement position with respect to the clutch mechanism, and the cam drive When rotating in the other direction by the motor, it contacts the free end of the lock member, rotates the lock member toward the unlocking position, releases the locking projection from the engagement with the lock hole, and disengages the lock member. The hook is engaged with the disengagement hook engaging portion of the lock member, and the slide member is engaged with the clutch mechanism together with the lock member. A power transmission mechanism for causing movement in a direction of displacing the location. The clutch mechanism meshes with the drive gear and an external output motor, a drive gear connected to the shaft of the external output motor, an arm provided to be rotatable about the axis of the external output motor. An idle gear that is rotatably attached to the arm, and an output gear that rotates by being connected to the idle gear,
The arm takes a power cutting posture by engagement with the slide member and takes a power transmission posture by releasing the engagement. When taking the power cutting posture, the arm is separated from the output gear and the clutch. 2. The power transmission mechanism according to claim 1, wherein when the mechanism is in a disconnected state and takes a power transmission posture, the clutch mechanism is brought into a connected state by meshing the idle gear with the output gear.   An image forming apparatus comprising the power transmission mechanism according to claim 2, wherein a developing roller provided in a developing device is connected to the output gear.

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