JP2021110847A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can give necessary rotational resistance to a gear at a small load.SOLUTION: An image forming apparatus comprises: a motor 3; cams 150; and a drive transmission device 100 that can transmit a driving force from the motor 3 to the cams 150. The drive transmission device 100 includes: electromagnetic clutches 140A, 140K that have a large-diameter gear 140L to which the driving force from the motor 3 is input and a small-diameter gear 140S that outputs the driving force toward the cams 150, the electromagnetic clutches 140A, 140K being switchable between a transmission state for transmitting the rotation of the large-diameter gear 140L to the small-diameter gear 140S and a shield state for not transmitting the rotation of the large-diameter gear 140L to the small-diameter gear 140S; a gear train that transmits the driving force from the small-diameter gear 140S to the cams 150, the gear train including an idle gear 133; and a leaf spring 200 that presses the idle gear 133 in the direction of the axis of rotation of the idle gear 133 to give rotational resistance to the idle gear 133.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus including a drive transmission device capable of transmitting a driving force from a motor to a driven body.

Conventionally, an image forming apparatus including a drive transmitting device capable of transmitting a driving force from a motor to a driven body is known (Patent Document 1). In this technique, the drive transmission device includes an electromagnetic clutch that can switch between a transmission state in which a driving force is transmitted to a shaft member which is a driven body and a cutoff state in which the driving force is not transmitted.

Japanese Unexamined Patent Publication No. 2008-033161

By the way, even if the electromagnetic clutch is disconnected, the driving force may be transmitted by the idling torque (drag torque) of the electromagnetic clutch to drive the driven body. In this respect, in the above-mentioned conventional technique, the friction member is pressed against the shaft of the gear that meshes with the transmission gear of the electromagnetic clutch to suppress the shaft member from being driven by the idling torque. However, in the configuration of the prior art, since the friction member presses the shaft in the radial direction of the shaft, there is a possibility that the load for imparting the necessary rotational resistance to the gear becomes large.

Therefore, an object of the present invention is to provide an image forming apparatus capable of imparting a necessary rotational resistance to a gear with a small load.

In order to achieve the above object, the image forming apparatus of the present invention can transmit the driving force from the motor, the driven body driven by transmitting the driving force from the motor, and the driving force from the motor to the driven body. It is equipped with a drive transmission device.
The drive transmission device includes an electromagnetic clutch, a gear train, and a rotation resistance member.
The electromagnetic clutch is an electromagnetic clutch having a first gear to which a driving force from a motor is input and a second gear to output a driving force toward a driven body, and the rotation of the first gear is a second gear. It is possible to switch between a transmission state in which the rotation is transmitted to the second gear and a cutoff state in which the rotation of the first gear is not transmitted to the second gear.
The gear train is a gear train that transmits a driving force from the second gear to the driven body, and includes a first idle gear.
The rotation resistance member presses the first idle gear in the direction of the rotation axis of the first idle gear to give rotation resistance to the first idle gear.

According to such a configuration, when the electromagnetic clutch is in the disconnected state, the rotation resistance member can suppress the rotation of the first idle gear, so that the driven body moves due to the idling torque of the electromagnetic clutch. It can be suppressed. At this time, since the rotation resistance member presses the first idle gear in the direction of the rotation axis of the first idle gear, it is possible to give the first idle gear the necessary rotation resistance with a small load.

In the image forming apparatus described above, the first idle gear may be configured to be a gear that directly meshes with the second gear.

According to this, since there is no other gear for decelerating between the second gear and the first idle gear, the reduction ratio from the second gear to the first idle gear can be minimized. As a result, the necessary rotational resistance can be given to the first idle gear and the second gear with a small load.

In the image forming apparatus described above, the rotation resistance member may be configured to be a leaf spring.

According to this, even if the rotation direction of the first idle gear is switched, the load can be uniformly applied to the first idle gear. As a result, the rotation resistance can be uniformly applied to the first idle gear regardless of the rotation direction of the first idle gear.

In the image forming apparatus described above, the position where the leaf spring presses the first idle gear shall be such that the distance to the outer circumference of the first idle gear is smaller than the distance to the rotation center of the first idle gear. Can be done.

According to this, it is possible to give the first idle gear the necessary rotational resistance with a small load.

In the image forming apparatus described above, the first idle gear is a large-diameter gear that directly meshes with the second gear, and is a large-diameter gear having more teeth than the second gear and a small-diameter gear that rotates integrally with the large-diameter gear. The leaf spring has a small diameter gear having a smaller number of teeth than the large diameter gear, and the leaf spring can be configured to press the large diameter gear in the direction of the rotation axis of the first idle gear.

According to this, by pressing the large diameter gear having a diameter larger than that of the second gear or the small diameter gear with the leaf spring, the position of the leaf spring pressing the first idle gear is from the rotation center of the first idle gear. It will be located farther away. This makes it possible to provide the first idle gear with the required rotational resistance with a smaller load.

In the image forming apparatus described above, the first idle gear has an annular rib protruding in the direction of the rotation axis of the first idle gear, and the leaf spring can be configured to press the rib.

According to this, since the load can be uniformly applied to the rotating first idle gear, the rotation resistance can be uniformly applied to the first idle gear.

The image forming apparatus described above further includes a gear cover that covers at least the first idle gear, and the leaf spring has a pressing portion that presses the first idle gear and a cover engaging portion that is positioned with respect to the gear cover. The gear cover may have a through hole into which the pressing portion is inserted and a positioning portion provided on the outer surface of the gear cover and in which the cover engaging portion engages.

According to this, the leaf spring can be assembled after assembling the first idle gear and the gear cover. As a result, the reaction force of the leaf spring is not applied when assembling the gear cover, so that the assembling property can be improved.

The image forming apparatus described above has a shaft that rotatably supports the first idle gear and a head, and the leaf spring is shafted with the leaf spring sandwiched between the head and the shaft by being screwed into the shaft. It can be configured to further include a screw for fixing the screw.

According to this, the reaction force of the leaf spring can be received by the head of the screw that fixes the leaf spring. As a result, the number of parts can be reduced.

In the image forming apparatus described above, the leaf spring has a plurality of pressing portions for pressing the first idle gear, and the plurality of pressing portions are arranged symmetrically with respect to the rotation center of the first idle gear. can do.

According to this, since the load can be uniformly applied to the first idle gear, the rotational resistance can be uniformly applied to the first idle gear.

According to the present invention, the required rotational resistance can be applied to the gear with a small load.

It is a figure which shows the schematic structure of the image forming apparatus which concerns on embodiment. It is a perspective view which looked at the motor, the drive transmission device, and the moving mechanism from the upper right. It is the figure which looked at the motor, the drive transmission device, and the moving mechanism from the right side. It is the figure which looked at the drive transmission device from the left side. It is a perspective view (a) and a side view (b) which show a cam, a cam follower, and a lever when a developing roller is in a contact position, and a clutch is in a transmission state. It is a schematic view which looked at the periphery of the developing cartridge from the top, and shows when the cam follower is in a standby position (a), and when it is in a protruding position (b). It is an exploded perspective view (a) of the clutch seen from the sun gear side, and is an exploded perspective view (b) seen from the carrier side. An exploded perspective view (a) of the lever, a view (b) showing a state in which the rotation of the first lever is restricted by a rotation regulating portion, and a view showing a state in which the first lever swings with respect to the second lever. (C). It is a perspective view (a) and a side view (b) which show a cam, a cam follower, and a lever when a developing roller is in a separated position and a clutch is in a disengaged state. It is a perspective view which shows the gear cover, the leaf spring, and the 1st plate. It is a perspective view which shows a shaft, an idle gear, a gear cover, a leaf spring, and a screw. It is the figure which looked at the electromagnetic clutch, an idle gear, and a leaf spring from the right side. It is sectional drawing which shows the state which the leaf spring is fixed with a screw to the shaft which supports idle gear rotatably. It is a perspective view which shows the leaf spring and a gear cover in an enlarged manner.

As shown in FIG. 1, the image forming apparatus 1 according to the embodiment is a color printer, and includes a housing 10, a sheet supply unit 20, an image forming unit 30, and a control unit 2. In the present embodiment, the left side of FIG. 1 is the front, the right side is the rear, the top and bottom are the top and bottom as they are, the front side of the paper surface of FIG. 1 is the right side, and the back side of the paper surface is the left side.

The seat supply unit 20 includes a seat tray 21 on which the seat S is set and a supply mechanism 22. The seat tray 21 is arranged below the image forming portion 30, and is removable from the housing 10 by pulling it forward. The supply mechanism 22 includes a paper feed roller 23, a separation roller 24, a separation pad 25, a transfer roller 26, and a registration roller 27. The sheet S is a medium on which an image can be formed by the image forming apparatus 1, and includes plain paper, envelopes, postcards, thin paper, thick paper, glossy paper, resin sheets, stickers, and the like.

The sheet S housed in the sheet tray 21 is sent out by the paper feed roller 23, then separated one by one between the separation roller 24 and the separation pad 25, and is directed toward the registration roller 27 by the transfer roller 26. Be transported. After that, the seat S is supplied to the image forming unit 30 by rotating the registration roller 27 after the position of the front end is regulated by the registration roller 27 in a state where the rotation is stopped.

The image forming unit 30 includes an exposure device 40, a plurality of photosensitive drums 50, a plurality of developing cartridges 60, a transport device 70, and a fixing device 80.
The exposure apparatus 40 includes a laser diode, a deflector, a lens, and a mirror (not shown). The exposure apparatus 40 is configured to expose the surface of each photosensitive drum 50 by emitting a plurality of light beams shown by an alternate long and short dash line that exposes the plurality of photosensitive drums 50.

The plurality of photosensitive drums 50 include a Y photosensitive drum 50Y corresponding to yellow, an M photosensitive drum 50M corresponding to magenta, a C photosensitive drum 50C corresponding to cyan, and a K photosensitive drum 50K corresponding to black. In the present specification and the drawings, when the members provided corresponding to each color are indicated by different colors, Y, M, C, and K are added to the reference numerals, and the members will be described without distinguishing the colors. In this case, Y, M, C, and K are not added to the symbols.

One development cartridge 60 is provided for each of the plurality of photosensitive drums 50. The plurality of developing cartridges 60 include a Y developing cartridge 60Y having a Y developing roller 61Y for supplying toner to the Y photosensitive drum 50Y, an M developing cartridge 60M having an M developing roller 61M for supplying toner to the M photosensitive drum 50M, and C. A C developing cartridge 60C having a C developing roller 61C for supplying toner to the photosensitive drum 50C and a K developing cartridge 60K having a K developing roller 61K for supplying toner to the K photosensitive drum 50K are included.

Each developing cartridge 60 is at a position where the developing roller 61 is in contact with the corresponding photosensitive drum 50 (see the solid line) and a position where the developing roller 61 is separated from the corresponding photosensitive drum 50 (see the virtual line). ) And can be moved.

The plurality of photosensitive drums 50 are rotatably supported by the support member 90. The support member 90 is provided with a charger 52 for charging the photosensitive drum 50, which is arranged corresponding to each photosensitive drum 50. The support member 90 is removable from the housing 10 through an opening formed by opening the front cover 11 of the housing 10. Further, the support member 90 supports the plurality of developing cartridges 60 in a detachable manner.

The transport device 70 is provided between the sheet tray 21 and the plurality of photosensitive drums 50. The transfer device 70 includes a drive roller 71, a driven roller 72, a transfer belt 73 including an endless belt, and four transfer rollers 74. The transport belt 73 is stretched between the drive roller 71 and the driven roller 72, and the outer surface is arranged so as to face each photosensitive drum 50. Each transfer roller 74 is arranged inside the transfer belt 73 so as to sandwich the transfer belt 73 with each photosensitive drum 50.

The fuser 80 is provided behind the plurality of photosensitive drums 50 and the conveying device 70. The fuser 80 includes a heating roller 81 and a pressure roller 82 arranged so as to face the heating roller 81. A transport roller 15 and a discharge roller 16 are provided on the downstream side of the fuser 80 in the transport direction of the sheet S.

In the image forming unit 30, the surface of the photosensitive drum 50 is uniformly charged by the charger 52, and then exposed by the light beam emitted from the exposure apparatus 40. As a result, an electrostatic latent image based on the image data is formed on the photosensitive drum 50. Further, the toner contained in the developing cartridge 60 is supported on the surface of the developing roller 61 and is supplied from the developing roller 61 located at the contact position to the electrostatic latent image formed on the photosensitive drum 50. As a result, a toner image is formed on the photosensitive drum 50. Next, the sheet S supplied on the transfer belt 73 is conveyed on the transfer belt 73 and passes between the photosensitive drum 50 and the transfer roller 74, so that the toner image on the photosensitive drum 50 is transferred to the sheet S. Will be done. Then, the sheet S passes between the heating roller 81 and the pressure roller 82, so that the toner image is heat-fixed to the sheet S. After that, the sheet S is discharged onto the paper discharge tray 13 by the transport roller 15 and the discharge roller 16.

Next, a configuration for driving / stopping the developing roller 61 and a configuration for contacting / separating the developing roller 61 with the corresponding photosensitive drum 50 will be described.
As shown in FIG. 2, the image forming apparatus 1 includes a motor 3, a drive transmission device 100, and a moving mechanism 5.

The motor 3 is a motor for driving the developing roller 61 and the cam 150 described later of the moving mechanism 5. The motor 3 is a motor capable of forward and reverse rotation. In the present embodiment, the rotation direction of the motor 3 when the image forming apparatus 1 forms an image is a forward rotation, and the case where the motor 3 rotates in the opposite direction to the forward rotation is a reverse rotation. The motor 3 has an output shaft 3A that is rotationally driven, and the output shaft 3A is provided with a gear (not shown). The drive of the motor 3 is controlled by the control unit 2.

The drive transmission device 100 is a device capable of transmitting the driving force from the motor 3 to the developing roller 61 and the cam 150. In this embodiment, the cam 150 corresponds to the "driven body". As shown in FIGS. 3 and 4, the drive transmission device 100 includes a first gear row 100D for transmitting the driving force to the developing roller 61 and a second gear row 100C for transmitting the driving force to the cam 150. have. In FIGS. 3 and 4, the meshing of the gears constituting the first gear row 100D is shown by a thick solid line, and the meshing of the gears constituting the second gear row 100C is shown by a thick broken line.

As shown in FIG. 4, the first gear train 100D includes idle gears 110, 113A, 113B, 113C, 115, a clutch 120, and a coupling gear 117. Each gear constituting the first gear train 100D is supported by the first plate 101 (see FIG. 10) or the second plate 102, and is rotatable around a rotation axis parallel to the axial direction of the photosensitive drum 50.

The coupling gear 117 has a coupling shaft 119 (see FIG. 2) that meshes with the clutch 120 and rotates integrally. The coupling shaft 119 can move in the axial direction of the developing roller 61 in conjunction with the opening and closing of the front cover 11 (see FIG. 1), and when the front cover 11 is closed, it engages with a coupling (not shown) of the developing cartridge 60. The driving force from the motor 3 can be transmitted to the developing roller 61.

The driving force of the yellow coupling gear 117Y is transmitted from the motor 3 via the idle gears 110A, 113A, 115Y and the clutch 120. The driving force of the magenta coupling gear 117M is transmitted from the motor 3 via the idle gears 110A, 113A, 115M and the clutch 120. The driving force of the cyan coupling gear 117C is transmitted from the motor 3 via the idle gears 110B, 113B, 115C and the clutch 120. The driving force of the black coupling gear 117K is transmitted from the motor 3 via the idle gears 110B, 113B, 115C, 113C, 115K and the clutch 120. The specific configuration of the clutch 120 will be described later.

As shown in FIG. 3, the second gear train 100C includes idle gears 131 to 137, a YMC clutch 140A, and a K clutch 140K. Each gear constituting the second gear train 100C is supported by the first plate 101 (see FIG. 10) or the second plate 102, and is rotatable around a rotation axis parallel to the axial direction of the photosensitive drum 50.

The YMC clutch 140A switches between rotation and stop of the cams 150Y, 150M, and 150C by switching between transmission and disconnection of the driving force. The YMC clutch 140A has a large-diameter gear 140L into which the driving force from the motor 3 is input, and a small-diameter gear 140S in which the driving force is output toward the cam 150. In the YMC clutch 140A, the large-diameter gear 140L meshes with the idle gear 132A, and the small-diameter gear 140S meshes with the idle gear 133A.

The K clutch 140K switches between rotation and stop of the cam 150K by switching between transmission and disconnection of the driving force. The K clutch 140K has the same configuration as the YMC clutch 140A, the large diameter gear 140L meshes with the idle gear 132B, and the small diameter gear 140S meshes with the idle gear 133B.

The YMC clutch 140A and the K clutch 140K are electromagnetic clutches. When the YMC clutch 140A and the K clutch 140K are energized and turned on, the rotation of the large diameter gear 140L is transmitted to the small diameter gear 140S, the large diameter gear 140L and the small diameter gear 140S rotate integrally, and the energization is stopped. By turning it off, it is possible to switch to a cutoff state in which the rotation of the large diameter gear 140L is not transmitted to the small diameter gear 140S. ON / OFF of the YMC clutch 140A and the K clutch 140K is controlled by the control unit 2.

The driving force of the yellow cam 150Y is transmitted from the motor 3 via the idle gears 110A, 131A, 132A, the YMC clutch 140A, and the idle gears 133A, 134. The driving force of the magenta cam 150M is transmitted from the cam 150Y via the idle gear 135. The driving force of the cyan cam 150C is transmitted from the cam 150M via the idle gear 136. The cams 150Y, 150M, and 150C rotate at the same time when the YMC clutch 140A is turned on, and stop when the YMC clutch 140A is turned off.

The driving force of the black cam 150K is transmitted from the motor 3 via the idle gears 110B, 131B, 132B, the K clutch 140K, and the idle gears 133B, 137. The cam 150K rotates when the K clutch 140K is turned on, and stops when the K clutch 140K is turned off.

As shown in FIG. 2, the moving mechanism 5 is a mechanism for moving the developing roller 61 between the contact position and the separated position. The moving mechanism 5 moves the developing roller 61 between the contact position and the separated position by receiving a driving force from the motor 3 when the motor 3 rotates in the forward direction, and also when the motor 3 rotates in the reverse direction. The developing roller 61 is configured to move between the contact position and the separated position by receiving the driving force from the developing roller 61. The moving mechanism 5 includes a plurality of cams 150 (150Y, 150M, 150C, 150K) and a plurality of cam followers 170 provided corresponding to each of the plurality of cams 150.

The cam 150 is rotationally driven by transmitting the driving force from the motor 3. The cam 150 rotates to move the corresponding developing roller 61 between the contact position and the separation position. As shown in FIG. 5, the cam 150 includes a disk portion 151, a gear portion 150G formed on the outer circumference of the disk portion 151, a first cam portion 152, a second cam portion 153, and a detected portion 154. And have.

The first cam portion 152 is a portion that moves the developing roller 61 between the contact position and the separated position, and protrudes from the disc portion 151 in the axial direction of the developing roller 61. The first cam portion 152 has a cam surface 152F on an end surface in the axial direction. The cam surface 152F has a first holding surface F1, a second holding surface F2, a first guide surface F3, and a second guide surface F4. The first holding surface F1 is a surface that holds the cam follower 170 at a standby position described later, and the second holding surface F2 is a surface that holds the cam follower 170 at a protruding position described later. The first guide surface F3 is a surface that connects the first holding surface F1 and the second holding surface F2 and is inclined with respect to the first holding surface F1, and the second guide surface F4 is the second holding surface F2 and the first. It is a surface inclined with respect to the first holding surface F1 that connects the holding surfaces F1. In FIG. 5 and the like, the dot hatch attached to the first cam portion 152 represents the second holding surface F2.

The second cam portion 153 is a portion that switches transmission and disengagement of the clutch 120 in cooperation with the lever 160 described later, and is opposite to the side surface of the disk portion 151 on which the first cam portion 152 is arranged. It protrudes from the side surface in the axial direction of the developing roller 61. The second cam portion 153 extends in a substantially arc shape when viewed from the axial direction. The second cam portion 153 is formed integrally with the disk portion 151 together with the first cam portion 152. Therefore, the second cam portion 153 rotates together with the first cam portion 152.

The detected portion 154 is a portion showing the phase of the cam 150 in the rotation direction, and protrudes from the disk portion 151 in the axial direction of the developing roller 61 at a position closer to the rotation center than the first cam portion 152. The detected portion 154 of the cyan and black cams 150C and 150K is detected by the separation sensors 4C and 4K described later.

As shown in FIG. 2, the cams 150Y, 150M, and 150C are almost the same in other configurations except that the length of the cam 150 of the first cam portion 152 in the rotation direction is longer than the others. Is. Further, the black cam 150K is provided with two first cam portions 152 that are short in the rotation direction.

Returning to FIG. 5, the cam follower 170 has a slide shaft portion 171, a contact portion 172, and a spring hook portion 174.
The slide shaft portion 171 is supported by a support shaft 179 (see FIG. 6B) provided in the housing 10 so as to be slidable in the axial direction of the developing roller 61. As a result, the cam follower 170 can slide and move in the axial direction.

The contact portion 172 is a portion that can come into contact with the cam surface 152F of the first cam portion 152, and is provided so as to extend from the slide shaft portion 171. The cam follower 170 has a protruding position in which the contact portion 172 contacts the second holding surface F2 to position the developing roller 61 at a separated position as shown in FIG. 6 (b) and a contact portion 172 shown in FIG. 6 (a). The developing roller 61 can be slidably moved to and from the standby position where it comes into contact with the first holding surface F1 and positions the developing roller 61 at the contact position.

As shown in FIG. 5, the spring hooking portion 174 is a portion on which one end of the spring 176 is hooked, and is provided so as to extend from the slide shaft portion 171 in a direction different from that of the contact portion 172. The spring 176 is a tension spring, and the other end thereof is hooked on a spring hooking portion (not shown) provided at a position below the spring hooking portion 174 of the second plate 102. The spring 176 urges the cam follower 170 from the protruding position to the standby position.

As shown in FIG. 6, the developing cartridge 60 is supported by the support member 90 so as to be movable back and forth. The support member 90 has a contacted portion 94 and a pressing member 95. The contacted portion 94 is a portion to which the slide member 64, which will be described later, comes into contact with the contacted portion 94, and is composed of a roller that can rotate about an axis along the vertical direction. The pressing member 95 is urged rearward by the spring 95A, and when the developing cartridge 60 is mounted on the supporting member 90, the pressing member 95 presses the developing cartridge 60 and brings the developing roller 61 into contact with the corresponding photosensitive drum 50. Move to the contact position.

The developing cartridge 60 has a case 63 for accommodating toner and a slide member 64. The slide member 64 is a member that can slide and move in the axial direction of the developing roller 61 with respect to the case 63, and slides and moves in the axial direction when pressed by the cam follower 170. The slide member 64 includes a shaft 191 supported by the case 63 so as to be slidable, a first contact member 192 provided at one end of the shaft 191 and a second contact member 193 provided at the other end of the shaft 191. And have.

The first contact member 192 has a pressing surface 192A and a slope 192B inclined with respect to the axial direction, and the second contact member 193 has a slope 193B inclined in the same manner as the slope 192B. The pressing surface 192A is pressed by the cam follower 170. When the slide member 64 is pressed by the cam follower 170, the slopes 192B and 193B abut on the contacted portion 94 to urge the developing cartridge 60 in a direction orthogonal to the axial direction, and the developing roller 61 is subjected to the corresponding photosensitivity. It is moved to a separation position away from the drum 50. A spring 194 for urging the slide member 64 toward the left side is arranged between the first contact member 192 and the case 63.

As shown in FIG. 2, the image forming apparatus 1 includes separation sensors 4C and 4K provided corresponding to the cyan and black cams 150C and 150K. The separation sensors 4C and 4K are phase sensors capable of detecting the origin of the phase of the cams 150C and 150K. A signal is output when it is located in the range, and no signal is output when the cams 150C and 150K are not located in the predetermined phase range.

The separation sensors 4C and 4K have a light emitting unit that emits detection light and a light receiving unit that can receive the detection light from the light emitting unit. The separation sensors 4C and 4K block the detection light of the light emitting unit by inserting the detected unit 154 between the light emitting unit and the light receiving unit, and output a signal to the control unit 2 when the light receiving unit does not receive the detected light. When the detected unit 154 is disengaged from between the light emitting unit and the light receiving unit and the light receiving unit receives the detected light of the light emitting unit, no signal is output to the control unit 2. Although the cams 150Y and 150M are also provided with the detected portion 154, since the separation sensor corresponding to the cams 150Y and 150M is not provided, these do not function as the portions detected by the separation sensor.

Next, a specific configuration of the clutch 120 and its function will be described.
As shown in FIG. 7, the clutch 120 has a planetary gear mechanism. The clutch 120 is configured to be switchable between a transmission state in which the driving force from the motor 3 is transmitted to the developing roller 61 and a disconnecting state in which the driving force from the motor 3 is not transmitted to the developing roller 61. Specifically, the clutch 120 includes a sun gear 121, a ring gear 122, and a carrier 123, which are elements that can rotate around one axis, and a planetary gear 124 supported by the carrier 123.

The sun gear 121 has a gear portion 121A, a disc portion 121B that rotates integrally with the gear portion 121A, and a plurality of claw portions 121C provided on the outer periphery of the disc portion 121B. The claw portion 121C has a sharp tip, and the sharp tip is inclined in one of the rotational directions in the circumferential direction.

The ring gear 122 has an inner gear 122A provided on the inner peripheral surface and an input gear 122B provided on the outer peripheral surface. The input gear 122B meshes with the idle gear 115 (see FIG. 4).

The carrier 123 has four shaft portions 123A that rotatably support the planetary gear 124, and an output gear 123B provided on the outer peripheral surface. The output gear 123B meshes with the coupling gear 117 (see FIG. 5).

Four planetary gears 124 are provided, and each of them is rotatably supported by a shaft portion 123A of the carrier 123. The planetary gear 124 meshes with the gear portion 121A of the sun gear 121 and also meshes with the inner gear 122A of the ring gear 122.

When the sun gear 121 is stopped so as not to rotate, the clutch 120 is in a transmission state in which the driving force input to the input gear 122B can be transmitted to the output gear 123B. On the other hand, when the sun gear 121 can rotate, the driving force input to the input gear 122B cannot be transmitted to the output gear 123B, resulting in a disconnection state. When a driving force is input to the input gear 122B while the clutch 120 is disengaged and a load is applied to the output gear 123B, the output gear 123B does not rotate and the sun gear 121 idles.

As shown in FIG. 5, the drive transmission device 100 further includes a lever 160 provided corresponding to each of the plurality of clutches 120. The lever 160 is swingably supported by a support shaft 102A provided on the second plate 102. As shown in FIG. 8A, the lever 160 has a first lever 161, a second lever 162, and a spring 163.

The first lever 161 can swing around the swing shaft X2, which is the central axis of the support shaft 102A, and can come into contact with the second cam portion 153. The first lever 161 has a rotation support portion 161A having a hole 161B fitted in the support shaft 102A, a first arm 161C extending from the rotation support portion 161A, and a protrusion from the rotation support portion 161A to the opposite side of the first arm 161C. It has a protrusion 161D and a protrusion 161D. As shown in FIGS. 8 (b) and 8 (c), the first lever 161 can swing around the swing shaft X2 relative to the second lever 162. Here, the position where the first lever 161 swings with respect to the second lever 162 shown in FIG. 8C is defined as the swing position.

The second lever 162 is swingable around the swing shaft X2 and can be engaged with the sun gear 121. The second lever 162 has a rotation support portion 162A having a hole 162B fitted to the support shaft 102A, a second arm 162C extending from the rotation support portion 162A, a rotation regulation portion 162D, and a spring hook portion 162E. There is. The rotation control unit 162D projects in the direction in which the swing shaft X2 extends from the second arm 162C. As shown in FIG. 8B, the rotation regulating unit 162D regulates the rotation of the first lever 161 with respect to the second lever 162 in one direction when the protrusion 161D of the first lever 161 comes into contact with the protrusion 161D.

The spring 163 is a torsion spring, and urges the first lever 161 toward the second lever 162 in the direction in which the protrusion 161D abuts on the rotation restricting portion 162D.

As shown in FIG. 5, the tip of the second arm 162C of the lever 160 extends toward the outer peripheral surface of the disc portion 121B of the sun gear 121. One end of the spring 169 is hooked on the spring hooking portion 162E. The spring 169 is a tension spring, and the other end thereof is hooked on a spring hooking portion (not shown) provided at a position before the spring hooking portion 162E of the second plate 102. As a result, the spring 169 urges the second lever 162 clockwise in FIG. The second arm 162C regulates the rotation of the sun gear 121 by engaging with the claw portion 121C of the sun gear 121.

The lever 160 is shown in FIG. 9 with an engaging position in which the tip end portion of the first lever 161 is separated from the second cam portion 153 and the second lever 162 is engaged with the claw portion 121C to bring the clutch 120 into the transmission state. When the tip of the first lever 161 comes into contact with the second cam and is pushed, the tip of the second lever 162 is disengaged from the claw portion 121C to disengage the clutch 120. It can swing between and.

Further, in the state where the lever 160 is in the engaging position as shown in FIG. 5, the motor 3 rotates in the reverse direction, the cam 150 rotates counterclockwise in FIG. 5, and the first lever 161 is in the second cam portion 153. When pushed, the first lever 161 swings with respect to the second lever 162 against the urging force of the spring 163, and is positioned at the swing position (see FIG. 8C). As a result, when the motor 3 rotates in the reverse direction, an unreasonable force is not applied to the lever 160.

The control unit 2 is a device that controls the operation of the image forming device 1. The control unit 2 has a CPU, a ROM, a RAM, an input / output unit, and the like, and executes each process by executing a program stored in advance. The control unit 2 controls the drive of the motor 3 and controls the ON / OFF of the YMC clutch 140A and the K clutch 140K to control the operation of the cam 150, thereby driving / stopping the developing roller 61 and. The contact / separation of the developing roller 61 with respect to the corresponding photosensitive drum 50 is controlled.

Here, an example of the processing of the control unit 2 will be described.
In the image forming apparatus 1, all the developing rollers 61 are located at separated positions in the standby state before executing the image forming. At this time, as shown in FIG. 9, the cam follower 170 is located at a protruding position where the contact portion 172 comes into contact with the second holding surface F2 of the cam 150.

When a print job is input and image formation is executed, the control unit 2 rotates the motor 3 in the forward direction and sets the YMC clutch 140A and the K clutch 140K to ON according to the color of the toner used for image formation to plot the cam 150. Rotate clockwise. As a result, the contact portion 172 of the cam follower 170 is guided from the second holding surface F2 to the second guide surface F4, slides on the second guide surface F4, and is brought into the first holding surface F1 as shown in FIG. Contact. As a result, the cam follower 170 slides from the protruding position to the standby position by the urging force of the spring 176, and the developing roller 61 moves from the separated position to the contact position. When the developing roller 61 moves to the contact position, the control unit 2 turns off the YMC clutch 140A and the K clutch 140K and stops the cam 150.

When the development by the developing roller 61 is completed, the control unit 2 turns on the YMC clutch 140A and the K clutch 140K and rotates the cam 150 again. As a result, the contact portion 172 is guided from the first holding surface F1 to the first guide surface F3, slides on the first guide surface F3, and comes into contact with the second holding surface F2 as shown in FIG. As a result, the cam follower 170 slides from the standby position to the protruding position, and the developing roller 61 moves from the contact position to the separated position. After that, when the separation sensors 4C and 4K output a signal, the control unit 2 turns off the YMC clutch 140A and the K clutch 140K and stops the cam 150.

On the other hand, when the open front cover 11 (see FIG. 1) is closed, the control unit 2 rotates the motor 3 in the reverse direction in order to position the developing roller 61 at a separated position (position in the standby state). , YMC clutch 140A and K clutch 140K are turned ON, and the cam 150 is rotated counterclockwise in the figure. After that, when the separation sensors 4C and 4K are turned on twice, the control unit 2 turns off the YMC clutch 140A and the K clutch 140K and stops the cam 150.

During this time, the contact portion 172 is guided from the first holding surface F1 to the second guide surface F4, slides on the second guide surface F4 and comes into contact with the second holding surface F2, so that the cam follower 170 protrudes from the standby position. The developing roller 61 slides to the position and moves from the contact position to the separated position. Further, the contact portion 172 is guided from the second holding surface F2 to the first guide surface F3, slides on the first guide surface F3 and comes into contact with the first holding surface F1, so that the cam follower 170 stands by from the protruding position. The developing roller 61 slides to the position and moves from the separated position to the contact position.

After stopping the cam 150, the control unit 2 rotates the motor 3 in the forward direction and turns on the YMC clutch 140A and the K clutch 140K to rotate the cam 150. Then, when the separation sensors 4C and 4K output a signal, the control unit 2 turns off the YMC clutch 140A and the K clutch 140K and stops the cam 150. As a result, the developing roller 61 is positioned at a separated position (position in the standby state).

As shown in FIGS. 10 and 11, the drive transmission device 100 further includes a leaf spring 200 as a rotation resistance member. Further, the image forming apparatus 1 further includes a gear cover 300, a shaft 400 that rotatably supports the idle gear 133, and a screw 500 for fixing the leaf spring 200 to the shaft 400.

As shown in FIG. 4, the idle gear 133 (133A, 133B) is a two-stage gear having a large-diameter gear 133L and a small-diameter gear 133S that rotates integrally with the large-diameter gear 133L. In the idle gear 133A, the large-diameter gear 133L directly meshes with the small-diameter gear 140S (see FIG. 3) of the YMC clutch 140A, and the small-diameter gear 133S directly meshes with the idle gear 134. Further, in the idle gear 133B, the large diameter gear 133L directly meshes with the small diameter gear 140S (see FIG. 3) of the K clutch 140K, and the small diameter gear 133S directly meshes with the idle gear 137. The large-diameter gear 133L is a gear having a larger number of teeth than the small-diameter gear 140S of the clutches 140A and 140K, and the small-diameter gear 133S is a gear having a smaller number of teeth than the large-diameter gear 133L.

In the present embodiment, the large diameter gear 140L of the clutches 140A and 140K corresponds to the "first gear", and the small diameter gear 140S corresponds to the "second gear". Further, the idle gear 133 corresponds to the "first idle gear". Further, the cams 150Y and 150M having the idle gears 133A, 134, 135 and 136 and the gear portion 150G form a "gear train" that transmits the driving force from the small diameter gear 140S of the YMC clutch 140A to the cams 150Y, 150M and 150C. ing. Further, the idle gears 133B and 137 form a "gear train" that transmits a driving force from the small diameter gear 140S of the K clutch 140K to the cam 150K. That is, the gear train includes the "first idle gear".

As shown in FIG. 11, the idle gear 133 has a rib 133R. The rib 133R is an annular rib protruding from the side surface of the large-diameter gear 133L in the direction of the rotation axis of the idle gear 133. The rib 133R projects from the side surface of the large diameter gear 133L to the side opposite to the small diameter gear 133S.

The leaf spring 200 is a member that presses the idle gear 133 in the direction of the rotation axis of the idle gear 133 to give rotation resistance to the idle gear 133. The leaf spring 200 is made of a metal plate, and has a fixed portion 210, a plurality of pressing portions 220, and a plurality of cover engaging portions 230.

The fixed portion 210 is a portion fixed to the shaft 400 by a screw 500, and has a through hole 211 in the center. The shaft 400 is caulked and fixed to a first plate 101 (see FIG. 13) having one end made of sheet metal. The shaft 400 has a screw hole 410 at the other end of which the screw 500 is screwed.

The pressing portion 220 is a portion that presses the idle gear 133 and extends from the fixed portion 210. As shown in FIG. 12, the plurality of pressing portions 220 are arranged symmetrically with respect to the rotation center 133C of the idle gear 133. In the present embodiment, two pressing portions 220 are provided, and one pressing portion 220 extends from the fixed portion 210 toward the opposite side of the other pressing portion 220.

As shown in FIG. 13, in a state where the leaf spring 200 is fixed to the shaft 400 that rotatably supports the idle gear 133, each pressing portion 220 comes into contact with the large diameter gear 133L of the idle gear 133 and has a large diameter. The gear 133L is pressed in the direction of the rotation axis of the idle gear 133, specifically, downward in FIG. Further, in the leaf spring 200, each pressing portion 220 comes into contact with the rib 133R provided on the side surface of the large diameter gear 133L, and presses the rib 133R in the direction of the rotation axis of the idle gear 133.

Returning to FIG. 12, the position where the pressing portion 220 presses the idle gear 133 of the leaf spring 200 is smaller at the distance D2 to the outer circumference of the idle gear 133 than at the distance D1 to the rotation center 133C of the idle gear 133. It has become. That is, the leaf spring 200 presses the idle gear 133 at a position closer to the outer circumference of the idle gear 133 than the rotation center 133C of the idle gear 133. Further, the leaf spring 200 presses the idle gear 133 (large diameter gear 133L) outside the small diameter gear 133S in the radial direction of the idle gear 133.

The pressing portion 220 has a gear contact portion 221 that is convex toward the idle gear 133. The gear contact portion 221 has a cross-sectional shape curved in a substantially arc shape (see FIG. 14). The pressing portion 220 is in contact with the rib 133R at the ridgeline portion of the gear contact portion 221. The ridgeline portion (see the alternate long and short dash line) of the gear contact portion 221 extends along the direction in which the pressing portion 220 extends from the fixed portion 210 so as to intersect the rib 133R. By contacting the rib 133R with such a gear contact portion 221, the pressing portion 220 can uniformly contact the rib 133R even if the position of the leaf spring 200 changes slightly in the vertical direction of FIG. , The idle gear 133 can be uniformly loaded.

The cover engaging portion 230 is a portion positioned with respect to the gear cover 300, and extends from the fixed portion 210 in a direction different from that of the pressing portion 220. Specifically, the cover engaging portion 230 extends from the fixed portion 210 in a direction substantially orthogonal to the direction in which the pressing portion 220 extends. The plurality of cover engaging portions 230 are arranged symmetrically with respect to the rotation center 133C of the idle gear 133. In the present embodiment, two cover engaging portions 230 are provided, and one cover engaging portion 230 extends from the fixed portion 210 toward the opposite side of the other cover engaging portion 230.

In the present embodiment, the two pressing portions 220 and the two cover engaging portions 230 are arranged alternately on the circumference centered on the rotation center 133C and at substantially equal intervals. The pressing portion 220 is longer than the cover engaging portion 230, and its tip is located outside the outer circumference of the large-diameter gear 133L. On the other hand, the cover engaging portion 230 is located inside the outer circumference of the large diameter gear 133L in the radial direction of the idle gear 133.

One cover engaging portion 230 has a penetrating first engaging hole 231 and the other cover engaging portion 230 has a penetrating second engaging hole 232. The first engaging hole 231 is formed in a substantially circular shape, and the second engaging hole 232 is formed in a substantially oval shape that is long in the direction in which the cover engaging portion 230 extends.

As shown in FIG. 10, the gear cover 300 is a member that covers the gears constituting the second gear row 100C (see FIG. 3), and is made of resin. The gear cover 300 is fixed to the first plate 101. The gear cover 300 has two clutch cover portions 310 that cover the clutches 140A and 140K, and two gear cover portions 320 that cover the idle gear 133. Further, as shown in FIG. 14, the gear cover 300 has a through hole 330 and a positioning portion 340.

The through hole 330 is a substantially rectangular hole into which the fixed portion 210 and the pressing portion 220 of the leaf spring 200 are inserted, and is formed in a state of penetrating the wall constituting the gear cover portion 320.

The positioning portion 340 is provided on the outer surface of the gear cover 300. Positioning portions 340 are provided on both sides of a central portion in the longitudinal direction of the through hole 330 so as to sandwich the through hole 330. Each positioning portion 340 has a concave portion 341 having a shape recessed with respect to the outer surface of the gear cover portion 320, and a positioning convex portion 342 protruding from the bottom surface of the concave portion 341. Engagement holes 231 and 232 of the cover engaging portion 230 are engaged with the positioning convex portion 342.

In the leaf spring 200, the cover engaging portion 230 is arranged in the concave portion 341 in a state where the engaging holes 231 and 232 are engaged with the positioning convex portion 342. The leaf spring 200 is restricted in rotation by engaging the two engaging holes 231 and 232 with the corresponding positioning protrusions 342, and the position with respect to the idle gear 133 and the gear cover 300 is determined. The leaf spring 200 has a second engaging hole 232 formed in a substantially oval shape, so that the effect of thermal expansion of the resin gear cover 300 can be absorbed.

As shown in FIG. 13, the screw 500 has a head portion 510 and a shaft portion 520 having threads formed on the outer peripheral surface thereof. The screw 500 is screwed into the screw hole 410 of the shaft 400 by passing the shaft portion 520 through the through hole 211 formed in the fixed portion 210 of the leaf spring 200. As a result, the leaf spring 200 is fixed to the shaft 400 by the screw 500. The screw 500 fixes the leaf spring 200 to the shaft 400 with the fixed portion 210 of the leaf spring 200 sandwiched between the head 510 and the shaft 400.

As shown in FIGS. 11 and 14, when the leaf spring 200 is assembled, first, the gears constituting the second gear row 100C including the idle gear 133 are assembled to the first plate 101 or the like. The idle gear 133 is assembled to the first plate 101 by engaging with the shaft 400 fixed to the first plate 101. Next, the gear cover 300 is arranged so as to cover the gears constituting the second gear row 100C, and the gear cover 300 is fixed to the first plate 101.

Then, the engaging holes 231 and 232 of the leaf spring 200 are engaged with the positioning convex portion 342 formed in the gear cover 300, and the cover engaging portion 230 is arranged in the concave portion 341. After that, the leaf spring 200 can be assembled by passing the shaft portion 520 of the screw 500 through the through hole 211 of the fixed portion 210 and screwing it into the screw hole 410 of the shaft 400.

As shown in FIG. 13, when the leaf spring 200 is fixed to the shaft 400 by the screw 500, each pressing portion 220 comes into contact with the rib 133R of the idle gear 133 and is pushed up. The leaf spring 200 presses the rib 133R of the idle gear 133 by the restoring force of the pressing portion 220. As a result, the leaf spring 200 presses the idle gear 133 in the direction of the rotation axis of the idle gear 133, and imparts rotation resistance to the idle gear 133.

In the above, the configuration of the leaf spring 200 that presses the idle gear 133A and its surroundings has been described. However, the configuration of the leaf spring 200 that presses the idle gear 133B (see FIG. 10) and its surroundings is also the same. A detailed description of the configuration will be omitted.

According to the present embodiment described above, when the clutches 140A and 140K are in the disengaged state, the leaf spring 200 can suppress the rotation of the idle gear 133, so that the cam 150 is driven by the idling torque of the clutches 140A and 140K. Can be suppressed from moving. At this time, since the leaf spring 200 presses the idle gear 133 in the direction of the rotation axis of the idle gear 133, as compared with the case where the rotation resistance member presses the first idle gear in the radial direction of the first idle gear, for example. Therefore, the required rotational resistance can be given to the idle gear 133 with a small load.

Further, the idle gear 133 is a gear that directly meshes with the small diameter gear 140S of the clutches 140A and 140K, and there is no other gear for decelerating between the small diameter gear 140S and the idle gear 133, so that there is another gear. In comparison, the reduction ratio from the small diameter gear 140S to the idle gear 133 can be minimized. As a result, the rotation required for the idle gear 133 and the small diameter gear 140S with a small load is compared with the case where the idle gear 133 is pressed by the leaf spring 200 when there is another gear between the small diameter gear 140S and the idle gear 133. Can give resistance.

Further, since the rotation resistance member is a leaf spring 200, even if the rotation direction of the idle gear 133 is switched by switching the rotation direction of the motor 3, for example, winding tightening and winding loosening unlike a coil spring do not occur, so that the idle gear A load can be uniformly applied to the 133. As a result, the rotation resistance can be uniformly applied to the idle gear 133 regardless of the rotation direction of the idle gear 133.

Further, since the position where the leaf spring 200 presses the idle gear 133 is smaller in the distance D2 to the outer circumference of the idle gear 133 than in the distance D1 to the rotation center 133C of the idle gear 133, the idle gear 133 with a small load. Can provide the required rotational resistance.

In particular, in the present embodiment, since the leaf spring 200 presses the small diameter gear 140S of the clutches 140A and 140K and the large diameter gear 133L having a diameter larger than that of the small diameter gear 133S, the position of the leaf spring 200 for pressing the idle gear 133 is determined. It will be located at a position farther from the rotation center 133C of the idle gear 133. This makes it possible to provide the idle gear 133 with the required rotational resistance with a smaller load.

Further, since the leaf spring 200 presses the annular rib 133R, a load can be uniformly applied to the rotating idle gear 133. As a result, rotational resistance can be uniformly applied to the idle gear 133.

Further, the image forming apparatus 1 can assemble the idle gear 133, assemble the gear cover 300, and then assemble the leaf spring 200. As a result, the reaction force of the leaf spring 200 is not applied when assembling the gear cover 300, so that the assembling property can be improved.

Further, since the leaf spring 200 is fixed to the shaft 400 with the leaf spring 200 sandwiched between the head 510 and the shaft 400 by the screw 500, the plate is fixed by the head 510 of the screw 500 that fixes the leaf spring 200. It can receive the reaction force of the spring 200. As a result, the number of parts can be reduced.

Further, since the plurality of pressing portions 220 are arranged symmetrically with respect to the rotation center 133C of the idle gear 133, a load can be uniformly applied to the idle gear 133. As a result, rotational resistance can be uniformly applied to the idle gear 133.

Although one embodiment of the invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented as illustrated below.
For example, the number of gears forming the gear train including the first idle gear is arbitrary.

Further, in the above-described embodiment, the gear cover 300 covers substantially all the gears constituting the second gear row 100C, but the present invention is not limited to this, and a configuration may cover some gears. Furthermore, the gear cover may be configured to cover at least the first idle gear.

Further, in the above-described embodiment, the leaf spring 200 has two pressing portions 220, but the present invention is not limited to this, and the leaf spring may have three or more pressing portions. Even in this case, it is desirable that the plurality of pressing portions are arranged symmetrically with respect to the rotation center of the first idle gear. Further, the leaf spring may have a configuration having only one pressing portion.

Further, in the above-described embodiment, the cam 150 is exemplified as a driven body that is driven by transmitting a driving force from a motor, but the driven body is not limited to this, and the driven body may be, for example, a photosensitive drum. good. The driven body includes a developing roller, a supply roller for supplying toner to the developing roller, a charging roller for charging the photosensitive drum, a cleaning roller for collecting transfer residual toner from the photosensitive drum, and a sheet. Rollers such as a paper feed roller (pickup roller) for picking up from the tray and a sheet transfer roller for transporting sheets may be used. Further, the driven body may be a member other than the roller, such as the cam 150.

Further, in the above embodiment, the leaf spring 200 is configured to press the annular rib 133R formed on the idle gear 133, but the present invention is not limited to this, and for example, the first idle gear in which the rib is not formed. It may be configured to press the side surface of the.

Further, in the above embodiment, the leaf spring 200 is configured to press the large diameter gear 133L of the idle gear 133, but the present invention is not limited to this, and the configuration may be such that the small diameter gear 133S is pressed.

Further, in the above embodiment, the configuration in which the rotation resistance member is a leaf spring 200 has been illustrated, but the present invention is not limited to this, and the rotation resistance member may be, for example, a coil spring or the like.

Further, in the above embodiment, the idle gear 133 (first idle gear) is a gear that directly meshes with the small diameter gear 140S (second gear) of the clutches 140A and 140K, but the present invention is not limited to this, and the second gear and the second gear are not limited to this. There may be another gear between one idle gear.

Further, in the above embodiment, the image forming apparatus 1 capable of forming an image using four color toners has been exemplified, but for example, an image using two colors, three colors, or five or more colors of toner can be formed. It may be an image forming apparatus. Further, it may be an image forming apparatus that forms an image using only one color of toner. Further, the image forming apparatus is not limited to a printer, and may be a multifunction device, a copying machine, or the like.

In addition, the elements described in the above-described embodiments and modifications can be combined and implemented as appropriate.

1 Image forming device 3 Motor 100 Drive transmission device 133 (133A, 133B) Idle gear 133L Large diameter gear 133S Small diameter gear 133R Rib 134 to 137 Idle gear 140A YMC clutch 140K K clutch 140L Large diameter gear 140S Small diameter gear 150 Cam 200 220 Pressing part 230 Cover engaging part 300 Gear cover 330 Through hole 340 Positioning part 400 Shaft 500 Screw 510 Head

Claims (9)

With the motor
A driven body that is driven by transmitting the driving force from the motor, and
An image forming apparatus including a drive transmission device capable of transmitting a driving force from the motor to the driven body.
The drive transmission device is
An electromagnetic clutch having a first gear to which a driving force from the motor is input and a second gear to output a driving force toward the driven body, and the rotation of the first gear is rotated by the second gear. An electromagnetic clutch that can switch between a transmission state that transmits to the second gear and a cutoff state that does not transmit the rotation of the first gear to the second gear.
A gear train that transmits a driving force from the second gear to the driven body, including a first idle gear, and a gear train.
An image forming apparatus comprising: a rotation resistance member that presses the first idle gear in the direction of the rotation axis of the first idle gear to give rotation resistance to the first idle gear. The image forming apparatus according to claim 1, wherein the first idle gear is a gear that directly meshes with the second gear. The image forming apparatus according to claim 1 or 2, wherein the rotation resistance member is a leaf spring. The claim is characterized in that the position at which the leaf spring presses the first idle gear is smaller than the distance to the rotation center of the first idle gear to the outer circumference of the first idle gear. The image forming apparatus according to 3. The first idle gear is
A large-diameter gear that directly meshes with the second gear and has a larger number of teeth than the second gear.
A small-diameter gear that rotates integrally with the large-diameter gear and has a small-diameter gear having fewer teeth than the large-diameter gear.
The image forming apparatus according to claim 4, wherein the leaf spring presses the large-diameter gear in the direction of the rotation axis. The first idle gear has an annular rib protruding in the direction of the rotation axis.
The image forming apparatus according to any one of claims 3 to 5, wherein the leaf spring presses the rib. Further provided with a gear cover that covers at least the first idle gear.
The leaf spring has a pressing portion that presses the first idle gear and a cover engaging portion that is positioned with respect to the gear cover.
A third to sixth aspect of the present invention, wherein the gear cover has a through hole into which the pressing portion is inserted and a positioning portion provided on the outer surface of the gear cover and with which the cover engaging portion engages. The image forming apparatus according to any one of the following items. A shaft that rotatably supports the first idle gear and
It is characterized by further comprising a screw having a head and fixing the leaf spring to the shaft with the leaf spring sandwiched between the head and the shaft by being screwed into the shaft. The image forming apparatus according to any one of claims 3 to 7. The leaf spring has a plurality of pressing portions for pressing the first idle gear, and has a plurality of pressing portions.
The image forming apparatus according to any one of claims 3 to 8, wherein the plurality of pressing portions are arranged symmetrically with respect to the rotation center of the first idle gear.

Images