Image forming apparatus

Abstract

This suppresses the shock when switching the clutch mechanism from a transmission state to a non-transmission state. [Solution] The system comprises a drive source, a first driven member, a second driven member, a first drive transmission unit that transmits rotational drive output from the drive source to the first driven member, the first drive transmission unit having a clutch mechanism that can transition between a transmission state and a non-transmission state, and a second drive transmission unit that transmits rotational drive output from the drive source to the second driven member and has a brake section that generates a braking force to load the rotation of the second driven member. The second drive transmission unit is connected to the first drive transmission unit between the clutch mechanism and the first driven member. When the clutch mechanism is in the transmission state, the first driven member is driven by both a first torque transmitted via the first drive transmission unit and a second torque transmitted via the brake section of the second drive transmission unit.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that forms an image on a recording material.

Background Art

[0002] Conventionally, an image forming apparatus provided with a photosensitive drum and a developing roller that can be driven by one motor has been proposed (see Patent Document 1). A clutch device that can be switched between a transmission state for transmitting the rotational drive from the motor and a non-transmission state for not transmitting the rotational drive from the motor is provided in the drive transmission path between the motor and the developing roller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the image forming apparatus described in Patent Document 1, when the clutch device switches from the transmission state to the non-transmission state, the torque applied to the developing roller instantaneously becomes 0, and the torque fluctuation is large. Therefore, the impact when switching the clutch device from the transmission state to the non-transmission state was large.

[0005] Therefore, an object of the present invention is to provide a form of an image forming apparatus capable of suppressing the impact when switching a clutch mechanism from a transmission state to a non-transmission state.

Means for Solving the Problems

[0006] One aspect of the present invention is an image forming apparatus for forming an image on a recording material, comprising: a drive source; a first driven member; a second driven member different from the first driven member; and a first drive transmission unit for transmitting rotational drive output from the drive source to the first driven member, the first drive transmission unit having a clutch mechanism that can transition between a transmission state in which rotational drive output from the drive source is transmitted to the first driven member and a non-transmission state in which rotational drive output from the drive source is not transmitted to the first driven member, and the second drive transmission unit for transmitting rotational drive output from the drive source to the second driven member, and the second The image forming apparatus comprises: 2 a second drive transmission unit having a brake section that generates a braking force to apply a load to the rotation of a driven member, and the second drive transmission unit being drive-connected to the first drive transmission unit, wherein the second drive transmission unit is connected to the first drive transmission unit between the clutch mechanism and the first driven member, and when the clutch mechanism is in the transmission state, the first driven member is driven by both a first torque transmitted via the first drive transmission unit and a second torque transmitted via the brake section of the second drive transmission unit. [Effects of the Invention]

[0007] According to the present invention, the shock when switching the clutch mechanism from a transmission state to a non-transmission state can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing the printer according to this embodiment. [Figure 2] A schematic diagram showing a printer with its door open. [Figure 3] A perspective view showing the cartridge. [Figure 4] Enlarged perspective view showing the drum coupling. [Figure 5] A perspective view showing the drive transmission mechanism. [Figure 6] (a) is an exploded perspective view showing the clutch unit, and (b) is another exploded perspective view showing the clutch unit. [Figure 7] (a) is a cross-sectional view showing the clutch unit in a transmission state, and (b) is a cross-sectional view showing the clutch unit in a non-transmission state. [Figure 8] (a) is an exploded perspective view showing the second drive transmission unit, and (b) is an exploded perspective view showing the first brake engagement member, the second brake engagement member, and the brake transmission member. [Figure 9] A cross-sectional view showing the second drive transmission unit. [Figure 10] (a) is a perspective view showing the drum drive coupling, (b) is a perspective view showing the drum drive coupling and coupling engagement part, and (c) is a perspective view showing how the coupling engagement part rotates within the through hole. [Figure 11] A cross-sectional view showing the drum drive coupling and the drum coupling engaged. [Figure 12] An enlarged cross-sectional view showing the vicinity of the protrusion of the drum coupling. [Figure 13] (a) is a schematic diagram showing the drive transmission path from the motor to the developing coupling when the clutch unit is in the transmission state, and (b) is a schematic diagram showing the drive transmission path from the motor to the developing coupling when the clutch unit is not in the transmission state. [Figure 14] (a) is a graph showing the torque applied to the developing coupling according to the comparative example, and (b) is a graph showing the torque applied to the developing coupling according to this embodiment. [Modes for carrying out the invention]

[0009] (Overall structure) First, the overall configuration of the printer 1 as an image forming apparatus according to this embodiment will be described using Figures 1 and 2. Figure 1 is a schematic diagram showing the overall configuration of the printer 1 according to this embodiment. Figure 2 is a schematic diagram showing the printer 1 with the door 20 open. The printer 1 is an electrophotographic color laser beam printer that forms images on a sheet S as a recording material.

[0010] In the following description and drawings, when the printer 1 is installed on a horizontal plane, the vertical direction is defined as the Z-axis direction. The axial direction of the photosensitive drum 61 included in the printer 1 is defined as the Y-axis direction. The direction that intersects both the Z-axis direction and the Y-axis direction is defined as the X-axis direction. The X-axis direction, the Y-axis direction, and the Z-axis direction are preferably perpendicular to each other. Also, one side of the X-axis direction (the side indicated by the arrow of X) may be referred to as the +X side or the +X direction, and the other side of the X-axis direction may be referred to as the -X side or the -X direction. Similarly, one side of the Y-axis direction (the side indicated by the arrow of Y) may be referred to as the +Y side or the +Y direction, the other side of the Y-axis direction may be referred to as the -Y side or the -Y direction, one side of the Z-axis direction (the side indicated by the arrow of Z) may be referred to as the +Z side or the +Z direction, and the other side of the Z-axis direction may be referred to as the -Z side or the -Z direction.

[0011] The +X direction can be referred to as the front side (front) of the printer 1. Also, based on the state of viewing the printer 1 from the front side, the +Y side can be referred to as the right side and the -Y side can be referred to as the left side.

[0012] <0,000,086>As shown in FIG. 1, the printer 1 includes a device main body 1A (housing), a scanner 2, a control unit 3, and a door 20. The printer 1 also includes a sheet feeding unit 30, a transfer unit 40, a tray unit (detachable unit) 50, and a fixing device 80. The portion including the device main body 1A and the door 20 can also be referred to as the main frame 100 of the printer 1. The main frame 100 includes the exterior portion of the printer 1. The device main body 1A houses the scanner 2, the control unit 3, the sheet feeding unit 30, the transfer unit 40, the secondary transfer roller 45, the tray unit 50, and the fixing device 80.

[0013] The sheet feeding unit 30 includes a stacking tray 31 for stacking the sheet S and a feeding roller 32 for feeding the sheet S. The stacking tray 31 can be pulled out in the direction of the door 20 to replenish the sheet S. In the present embodiment, the opening direction of the door 20 and the pulling-out direction of the stacking tray 31 are the same direction, the +X side.

[0014] The tray unit 50 has a tray 51 (support member, drawer) and cartridges PY, PM, PC, and PK. The tray 51 has a tray handle 52 (grip portion). The cartridges PY, PM, PC, and PK are detachably (removably) attached to the tray 51.

[0015] Each of the cartridges PY, PM, PC, and PK is detachably attached to the tray 51 independently of the others. The cartridges PY, PM, PC, and PK each contain toner (developer) of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The cartridges PY, PM, PC, and PK have the same configuration except for the different colors of the toner they contain. Therefore, the configuration and operation of any one of the cartridges PY, PM, PC, and PK may be described, and the description of the others may be omitted. Also, when it is not necessary to distinguish between the cartridges PY, PM, PC, and PK, the cartridges PY, PM, PC, and PK may simply be referred to as cartridge P. It can be said that the tray unit 50 has a plurality of cartridges P and a tray 51 to which the plurality of cartridges P are removably attached.

[0016] In the present embodiment, the tray unit 50 has a plurality of photosensitive drums (image carriers) 61, a plurality of charging rollers 62 (charging members), and a plurality of developing rollers (developing members, developer carriers) 71. Specifically, the tray unit 50 has four photosensitive drums 61, four charging rollers 62, and four developing rollers 71. The rotational axis directions of each photosensitive drum 61, each developing roller 71, and each charging roller 62 are substantially parallel.

[0017] The part of the tray unit 50 that forms the black image is called the black station (first station), and the photosensitive drum 61 of the first station can be called the first photosensitive drum, the developing roller 71 can be called the first developing roller, and the charging roller 62 can be called the first charging roller. The part of the tray unit 50 that forms the cyan image is called the cyan station (second station), and the photosensitive drum 61 of the second station can be called the second photosensitive drum, the developing roller 71 can be called the second developing roller, and the charging roller 62 can be called the second charging roller. The part of the tray unit 50 that forms the magenta image is called the magenta station (third station), and the photosensitive drum 61 of the third station can be called the third photosensitive drum, the developing roller 71 can be called the third developing roller, and the charging roller 62 can be called the third charging roller. The part of the tray unit 50 that forms the yellow image is called the yellow station (fourth station), and the photosensitive drum 61 of the fourth station can be called the fourth photosensitive drum, the developing roller 71 can be called the fourth developing roller, and the charging roller 62 can be called the fourth charging roller.

[0018] Cartridge PK, mounted in tray 51, constitutes at least a part of the black station. Cartridge PC, mounted in tray 51, constitutes at least a part of the cyan station. Cartridge PM, mounted in tray 51, constitutes at least a part of the magenta station. Cartridge PY, mounted in tray 51, constitutes at least a part of the yellow station. Cartridge PK can be referred to as the first cartridge, cartridge PC as the second cartridge, cartridge PM as the third cartridge, and cartridge PY as the fourth cartridge. Note that the ordinal numbers 1st, 2nd, 3rd, and 4th used in the above explanation are for convenience.

[0019] The photosensitive drum 61, the charging roller 62, and the developing roller 71 may be provided in either the cartridge P or the tray 51. In this embodiment, the cartridge P has the photosensitive drum 61, the charging roller 62, and the developing roller 71.

[0020] The transfer unit 40 includes a belt 41, a primary transfer roller 42, a cleaning unit 43, a drive roller 46 for driving the belt 41, and a tension roller 47. The printer 1 is also equipped with an optical sensor 44 for detecting the toner image transferred to the belt 41. In this embodiment, the belt 41 is positioned below the photosensitive drum 61 and is able to contact the photosensitive drum 61 so that a primary transfer section is formed between the belt 41 and the photosensitive drum 61.

[0021] Furthermore, the printer 1 has a secondary transfer roller 45 that contacts the belt 41 so that a secondary transfer section is formed. The secondary transfer section is formed between the belt 41 and the secondary transfer roller 45. The rotational axis directions of the primary transfer roller 42, the drive roller 46, the tension roller 47, and the secondary transfer roller 45 are substantially parallel. Upstream of the secondary transfer section in the conveying direction of the sheet S, a pair of registration rollers 4 is positioned.

[0022] The fixing device 80 includes a fixing section 81 and a switching guide 5. In this embodiment, the fixing device 80 is movable relative to the device body 1A between a working position and a retracted position. When the image forming operation is performed, the fixing device 80 is in the working position. When the fixing device 80 is in the working position, it is housed inside the device body 1A. The fixing device 80 is also configured to heat the sheet S when it is in the working position. The fixing section 81 includes a heating section (heating roller) that includes a heater (heat source), and a pressing section (pressure roller) that forms a fixing nip together with the heating section.

[0023] As shown in Figure 2, the device body 1A has an opening 1A1 at the +X side end. The door 20 is an opening / closing member (cover member, front cover) that can move relative to the device body 1A between a closed position and an open position. As shown in Figure 1, when the door 20 is in the closed position, the door 20 covers the opening 1A1. As shown in Figure 2, when the door 20 is in the open position, the opening 1A1 is exposed. When the door 20 is in the closed position, the printer 1 performs the image forming operation described later. When the door 20 is in the open position, the tray unit 50 and the transfer unit 40 are allowed to be pulled out from the device body 1A through the opening 1A1. The tray unit 50 can be pulled out from the device body 1A by the user pulling the tray handle 52 of the tray 51. When the tray 51 is pulled out from the device body 1A, the cartridge P can be detached from the tray 51.

[0024] In other words, the cartridge P can be considered a removable unit configured to be detachable from the main body 1A of the device. Similarly, the tray unit 50 can also be considered a removable unit configured to be detachable from the main body 1A of the device. The drum unit 68, which will be described later and is provided on the cartridge P, is an example of a rotatably driven member.

[0025] The fixing device 80 is movable (retractable) from the usage position shown in Figure 1 to a retracted position that is retracted above the specified position, so that the opening 1A1 is widely exposed. When the door 20 is moved to the open position and the fixing device 80 is moved to the retracted position, the transfer unit 40 and the tray unit 50 can move from the inside to the outside of the device body 1A through the opening 1A1.

[0026] (Image formation process) Using Figure 1, the image formation operation, which is a series of operations in which the printer 1 transports a sheet S and forms an image on the sheet S, will be explained. The control unit 3 of the printer 1 starts the image formation operation based on image information received from an external host device 90. The external host device 90 is, for example, a personal computer, an image reader, or a facsimile machine.

[0027] When the image forming operation starts, the photosensitive drum 61 is rotated at each station of the tray unit 50, and the charging roller 21, to which a charging voltage is applied, uniformly charges the surface of the photosensitive drum 61. At the same time, a laser corresponding to the image information is shone from the scanner 2 onto each photosensitive drum 61, exposing the surface of the photosensitive drum 61. As a result, an electrostatic latent image corresponding to the image obtained by decomposing the original image information into its CMYK color components is formed on the surface of the photosensitive drum 61.

[0028] The developing roller 71 rotates while carrying toner. A developing voltage is applied to the developing roller 71, and the electrostatic latent image formed on the photosensitive drum 61 is developed by the toner supplied from the developing roller 71, forming a toner image on the surface of the photosensitive drum 61. In this embodiment, the developing roller 71 develops the electrostatic latent image while in contact with the photosensitive drum 61 (contact developing method). However, the developing roller 71 may develop the electrostatic latent image with a gap between it and the photosensitive drum 61. When a full-color image is formed, toner images of each color are formed on each photosensitive drum 61.

[0029] In this embodiment, the developing roller 71 is movable between a contact position in contact with the photosensitive drum 61 and a separated position away from the photosensitive drum 61. Specifically, a switching device provided in the main body 1A switches between the developing roller 71 being in the contact position and the developing roller 71 being in the separated position. This allows the developing roller 71 to be kept away from the photosensitive drum 61 when no image forming operation is being performed.

[0030] Furthermore, printer 1 can perform monochrome printing with the developing roller 71 and photosensitive drum 61 corresponding to cartridge PK in contact, and the developing roller 71 and photosensitive drum 61 corresponding to cartridges PY, PM, and PC separated. In addition, printer 1 can perform full-color printing with the photosensitive drum 61 and belt 41 corresponding to cartridges PY, PM, PC, and PK in contact.

[0031] The toner images formed on each photosensitive drum 61 are transferred onto the belt 41 by the primary transfer roller 42 in the primary transfer section. The toner images, supported on the belt 41, are then transported towards the secondary transfer section, which is formed by the belt 41 and the secondary transfer roller 45.

[0032] On the other hand, the main body 1A of the device has a transport path 1c (first transport path) that goes from the feed roller 32 through the secondary transfer section to the fixing device 80. The door 20 also has a double-sided transport path (second transport path) 20a through which the sheet S that has passed through the fixing device 80 passes. When the door 20 is closed, it covers the transport path 1c. As shown in Figure 2, when the door 20 is opened, at least a part of the transport path 1c and at least a part of the double-sided transport path 20a are exposed.

[0033] In the image formation operation, in parallel with the formation of the toner image described above, sheets S are fed one by one from the sheet feeding unit 30 to the secondary transfer unit via the transport path 1c. Specifically, the top sheet S of the sheets S stacked on the loading tray 31 is fed out by the feeding roller 32 at a predetermined timing. The fed-out sheets S are separated by a separating member such as a friction roller, and further corrected for skew and adjusted for timing by a pair of registration rollers 4, before being sent to the secondary transfer unit. In the secondary transfer unit, the toner image is transferred from the belt 41 to the sheets S by applying voltage to the secondary transfer roller 45. Toner that was not transferred to the sheets S is removed from the belt 41 by a cleaning blade 43A (cleaning member) provided in the cleaning unit 43.

[0034] The sheet S onto which the toner image has been transferred in the secondary transfer section is transported to the fuser unit 80. The sheet S is heated and pressurized in the fuser unit 81, and the toner image is fixed to the sheet S. After passing through the fuser unit 81, the sheet S reaches the switching guide 5, which acts as a path switching section.

[0035] The switching guide 5 is movable between a paper output position that guides the sheet S, which has passed through the fuser 80, toward the output path 1d, and a reversal position that guides it toward the reversal path 1e. When single-sided printing is performed, in which an image is formed on one side of the sheet S, the sheet S is guided toward the output path 1d by the switching guide 5 and discharged into the output tray 1f formed on the upper part of the device body 1A.

[0036] On the other hand, when double-sided printing is performed in which an image is printed on one side and the other side of the sheet S, the sheet S is guided to the reversal path 1e by the switching guide 55. After the sheet S is guided to the reversal path 1e, the transport direction of the sheet S is reversed, and the sheet S is transported through the double-sided transport path 20a formed in the door 20 toward the secondary transfer section. After the toner image is transferred to the back side of the sheet S in the secondary transfer section, the sheet S passes through the fuser 80, is guided to the discharge path 1d by the switching guide 5, and is discharged into the discharge tray 1f of the main body 1A.

[0037] As described above, the door 20 covers the opening 1A1 in the closed position and also covers at least a portion of the sheet S transport path 1c. The door 20 also has a double-sided transport path 20a. If a sheet S jams (hereinafter referred to as a jam), the user of the printer 1 can remove the sheet S from one end (+X side) of the device body 1A to clear the jam. Specifically, the door 20 can be moved to the open position to access the inside of the device body 1A and remove the sheet S. Also, if a portion of the sheet S that has passed through the fuser 80 is exposed to the outside of the device body 1A, the sheet S can be pulled from the outside of the device body 1A and removed without opening the door 20.

[0038] Furthermore, the user of printer 1 can move the transfer unit 40 and tray unit 50 from one end of the main unit 1A to the outside of the main unit 1A to perform tasks such as checking the condition of the transfer unit 40 and cartridge P, maintenance, and replacement.

[0039] In other words, the printer 1 has a fuser 80 located at one end of the main body 1A, while the transfer unit 40 and tray unit 50 can be moved in and out of the main body 1A through that end. As a result, the user can clear jams, access the fuser 80, and operate the transfer unit 40 and tray unit 50 from one direction.

[0040] In this embodiment, the printer 1 has its front facing the door 20 side (+X side). Therefore, it is sufficient to have enough space to perform tasks such as clearing jams and operating the transfer unit 40 and tray unit 50 from the front of the printer 1. On the other hand, the space required to perform these tasks from the left, right, back, and top of the printer 1 can be omitted. Therefore, the printer 1 can be installed in a space-saving manner.

[0041] If the transfer unit 40 or tray unit 50 is pulled out from the other end of the device body 1A, the user needs to access both ends of the device body 1A to clear the jam and pull out the transfer unit 40 or tray unit 50. Similarly, if one of the transfer unit 40 or tray unit 50 is pulled out from one end of the device body 1A and the other is pulled out from the other end, the user also needs to access both ends of the device body 1A. As a result, space is required to work from both the front and the back of the device body 1A, increasing the area required to install the printer 1.

[0042] Furthermore, in this embodiment, the sheets S can be replenished from one end of the device body 1A. Therefore, it is sufficient to have space to replenish the sheets S from the front of the printer 1, and the printer 1 can be installed in a space-saving manner.

[0043] (cartridge) Next, the configuration of cartridge P will be explained using Figures 3 and 4. Figure 3 is a perspective view showing cartridge P, which is a process cartridge. Figure 4 is an enlarged perspective view showing drum coupling 63.

[0044] As shown in Figure 3, the cartridge P comprises a drum unit 60 and a developing unit 70. The cartridge P also has a first side cover 66 and a second side cover 67, which are fixed to both ends of the drum unit 60 and the developing unit 70 in the longitudinal direction LD of the cartridge P. The developing unit 70 is rotatably supported by the first side cover 66 and the second side cover 67.

[0045] The drum unit 60 consists of a photosensitive drum 61, a charging roller 62, and a drum frame 65, etc. A drum coupling 63 and a drum flange 64 are fixed to the photosensitive drum 61 as second driven members, and these photosensitive drum 61, drum coupling 63 and drum flange 64 constitute a drum unit 68. The drum coupling 63 is rotatably supported on the first side cover 66, and the drum flange 64 is rotatably supported on the second side cover 67. In other words, the photosensitive drum 61 is rotatably supported on the first side cover 66 and the second side cover 67 via the drum coupling 63 and drum flange 64.

[0046] In this embodiment, the drum unit 60 is not provided with cleaning means (e.g., a cleaning blade) for removing residual toner remaining on the surface of the photosensitive drum 61, but this is not limited to this. For example, the drum unit 60 may be provided with the above-mentioned cleaning means.

[0047] The developing unit 70 includes a developing roller 71 that holds toner, a toner transport roller (toner supply roller) not shown, a developing blade not shown, a developing coupling 72, and a developing frame 73. The developing roller 71 supplies toner contained in the toner storage chamber within the developing frame 73 to the photosensitive drum 61, developing the electrostatic latent image on the photosensitive drum 61 as a toner image. The toner transport roller supplies toner from the toner storage chamber to the developing roller 71. The developing blade regulates the thickness of the toner layer carried on the developing roller 71. The developing coupling 72, which acts as the first driven member, is given rotational drive from the main body 1A, thereby driving the developing roller 71 and the toner transport roller. The developing coupling 72 is a different member from the drum coupling 63.

[0048] As shown in Figure 4, the drum coupling 63 has a circular hole 63a and a projection 63e, which will be described in more detail later. There are two projections 63e, positioned 180 degrees apart from each other in the circumferential direction around the rotation axis M1. Each projection 63e is provided with a driving force receiving portion 63b and a braking force receiving portion 63c. The circular hole 63a can engage with a positioning boss 180i provided on the drum drive coupling 180 of the drum drive transmission unit 203, which will be described later. The engagement of the circular hole 63a and the positioning boss 180i aligns the drum drive transmission unit 203 and the drum coupling 63. The driving force receiving portion 63b receives rotational drive from the drum drive transmission unit 203, and the braking force receiving portion 63c receives braking force from the braking force applying unit 260 (see Figure 5(a)), which will be described later. The drive force receiving portion 63b is located upstream of the brake force receiving portion 63c in the direction of arrow A, which is the rotation direction of the drum unit 68. In this embodiment, there are two drive force receiving portions 63b and two brake force receiving portions 63c.

[0049] Next, the configuration of the drive transmission mechanism 200 provided in the main body 1A of the device will be described using Figure 5. Figure 5 is a perspective view showing the drive transmission mechanism 200. As shown in Figure 5, the drive transmission mechanism 200 includes a motor M as a drive source, an output unit MP that outputs the rotational drive of the motor M, a first drive transmission unit 150 as a first drive transmission unit, and a second drive transmission unit 250 as a second drive transmission unit. The output unit MP may be a gear formed on or attached to the shaft of the motor M, or it may be another gear that meshes with this gear. The first drive transmission unit 150 and the second drive transmission unit 250 are connected to the output unit MP. The transmission path of the rotational drive of the motor M can be said to branch from the output unit MP to the first drive transmission unit 150 and the second drive transmission unit 250. Of course, other drive transmission members such as gears may be provided in the drive transmission path between the output unit MP and the first drive transmission unit 150, and in the drive transmission path between the output unit MP and the second drive transmission unit 250.

[0050] The first drive transmission unit 150 includes a clutch unit 120 as a clutch mechanism, a gear 112, a developing drive gear 111 as a rotating body, and a developing drive coupling 110, and transmits the rotational drive output from the motor M to the developing coupling 72. The developing drive gear 111 and the developing drive coupling 110 are located between the clutch unit 120 and the developing coupling 72. The developing drive gear 111 is also located between the developing drive coupling 110 and the clutch unit 120.

[0051] The second drive transmission unit 250 includes a drum drive transmission unit 203, a brake force application unit 260, a brake section 206, a rotating shaft 215, and a gear 220, and transmits the rotational drive output from the motor M to the drum coupling 63. The second drive transmission unit 250 is connected to the first drive transmission unit 150 between the developing coupling 72 and the clutch unit 120. The second drive transmission unit 250 is connected to the first drive transmission unit 150 between the developing drive coupling 110 and the clutch unit 120. In this embodiment, the gear 220 of the second drive transmission unit 250 meshes with the developing drive gear 111 and is connected to the first drive transmission unit 150. The brake section 206 is located between the output section MP and the gear 220. The gear 220 can be called the connection section that connects to the first drive transmission unit 150.

[0052] The developing drive gear 111 of the first drive transmission unit 150 is rotatably supported on a shaft (not shown) fixed to the drive frame 102 (see Figure 9) and is driven-coupled to the developing coupling 72. Rotational drive (driving force) output from the motor M is transmitted to the developing drive gear 111 via the output unit MP, clutch unit 120, and gear 112. The developing coupling 72 is supported so as to be movable in the thrust direction relative to the developing drive gear 111 and is biased toward the developing coupling 72 by a biasing member (not shown).

[0053] The drum coupling 63 receives rotational drive (driving force) output from the motor M via the drum drive transmission unit 203, which will be described later. The drum coupling 63, drum drive transmission unit 203, and gear 216 rotate around the rotation axis M1. In Figure 5, for illustrative purposes, the developing coupling 72 and the developing drive coupling 110 are shown separately, and the drum coupling 63 and the drum drive coupling 180 are shown separately, but in reality, they are engaged with each other and transmit drive.

[0054] Furthermore, the rotational drive (driving force) output from the motor M is transmitted to the developing drive gear 111 via the output unit MP, drum drive transmission unit 203, drum coupling 63, brake force application unit 260, brake unit 206, rotating shaft 215, and gear 220. In other words, the rotational drive of the motor M is transmitted to the developing drive gear 111 via two paths: a first drive transmission path through the first drive transmission unit 150, and a second drive transmission path through the second drive transmission unit 250.

[0055] (Clutch unit) Next, the clutch unit 120 of the first drive transmission unit 150 will be described using Figures 6(a) to 7(b). Figure 6(a) is an exploded perspective view showing the clutch unit 120, and Figure 6(b) is another exploded perspective view showing the clutch unit 120. Figure 7(a) is a cross-sectional view showing the clutch unit 120 in the transmission state, and Figure 7(b) is a cross-sectional view showing the clutch unit 120 in the non-transmission state.

[0056] As shown in Figures 6(a) and 6(b), the clutch unit 120 includes a clutch drive gear 122, a biasing member 124, a drive-side engaging member 123, a release member 127, a cam holding member 128, a cam gear member 126, and a clutch driven gear 125. The device body 1A is provided with a drive frame 101, and a shaft 121 is fixed to the drive frame 101.

[0057] The rotational drive output from the motor M is transmitted to the clutch drive gear 122, which is rotatably supported on the shaft 121. The drive-side engaging member 123 and the clutch driven gear 125 are also rotatably supported on the shaft 121. The clutch drive gear 122 has a hollowed-out inner surface on the gear portion provided on its outer circumferential surface, and the inner circumferential surface of the clutch drive gear 122 is configured as a positioning surface and sliding surface for positioning the drive-side engaging member 123.

[0058] The drive-side engaging member 123 has a ratchet portion 123a, a groove portion 123b, and a pawl portion 123c, with the groove portion 123b engaging with the rotation-stopping portion 122a of the clutch drive gear 122. As a result, the drive-side engaging member 123 is configured to rotate integrally with the clutch drive gear 122 around the shaft 121. Furthermore, the drive-side engaging member 123 is configured to be movable in the axial direction of the shaft 121 relative to the clutch drive gear 122.

[0059] A biasing member 124 is positioned between the clutch drive gear 122 and the drive-side engaging member 123. The biasing member 124 biases the drive-side engaging member 123 in a direction away from the clutch drive gear 122, and also biases the drive-side engaging member 123 in a direction to engage with the clutch driven gear 125. In this embodiment, the biasing member 124 is made of a compression spring. The drive-side engaging member 123 is held in a state where it abuts against the abutment surface 127c of the release member 127 by being biased by the biasing member 124. The drive-side engaging member 123 moves in conjunction with the movement of the release member 127 in the axial direction of the shaft 121 (the same direction as the axial direction MD described later).

[0060] The claw portion 123c provided on the outer circumferential surface of the drive-side engaging member 123 engages with the retaining portion 122b provided on the clutch drive gear 122. This prevents the drive-side engaging member 123 from detaching from the clutch drive gear 122 due to the biasing force of the biasing member 124. In other words, the drive-side engaging member 123 is prevented from detaching from the clutch drive gear 122 by the engagement of the claw portion 123c with the retaining portion 122b.

[0061] The clutch driven gear 125 has a ratchet portion 125a that faces the ratchet portion 123a of the drive-side engaging member 123, and a cylindrical portion 125b. Furthermore, the clutch driven gear 125 is restricted from moving in the second direction M1B by abutting against the drive frame 102 (see Figure 9).

[0062] As shown in Figure 7(a), when the ratchet portion 123a of the drive-side engaging member 123 engages with the ratchet portion 125a of the clutch driven gear 125, the clutch unit 120 enters a transmission state. Also, as shown in Figure 7(b), when the ratchet portion 123a of the drive-side engaging member 123 separates from the ratchet portion 125a of the clutch driven gear 125, the clutch unit 120 enters a non-transmission state. When the clutch unit 120 is in a transmission state, the rotational drive output from the motor M is transmitted to the developing drive gear 111. On the other hand, when the clutch unit 120 is in a non-transmission state, the rotational drive output from the motor M is not transmitted to the developing drive gear 111. In other words, the clutch unit 120 can transition between a transmission state in which the rotational drive output from the motor M is transmitted to the developing coupling 72, and a non-transmission state in which the rotational drive output from the motor M is not transmitted to the developing coupling 72.

[0063] The cam holding member 128 has a rotation-stopping portion 128a and a protrusion 128b, and is pivotally supported on the inner circumference 122c of the clutch drive gear 122. The rotation-stopping portion 128a engages with a rotation-restricting hole (not shown) in the drive frame 102 (see Figure 9), thereby restricting rotation around the shaft 121. The cam gear member 126 has multiple (three in this embodiment) cam portions 126a protruding toward the release member 127, and is rotatably supported on the cylindrical portion 125b of the clutch driven gear 125.

[0064] The release member 127 has a recess 127b and a top surface 127a1, a bottom surface 127a2, and a slanted surface 127a3 that can engage with the cam portion 126a. The release member 127 is configured to rotate integrally with the cam holding member 128 around the shaft 121 by the recess 127b engaging with the protrusion 128b of the cam holding member 128. The release member 127 is configured to be relatively movable with respect to the cam holding member 128 in the axial direction of the shaft 121.

[0065] The cam gear member 126 is driven by a solenoid and gear train (not shown) which disconnect and reconnect the rotational drive from the motor M. In this embodiment, the cam gear member 126 is controlled to rotate 1 / 3 of a turn, or 60 degrees, by opening the solenoid once. Alternatively, other actuators may be used instead of the solenoid.

[0066] When the cam gear member 126 rotates and the cam portion 126a of the cam gear member 126 and the top surface portion 127a1 of the release member 127 are in the same phase, the top surface portion 127a1 of the release member 127 is pressed to the left in Figures 6(a) and 6(b). As a result, the release member 127 and the drive-side engaging member 123 move away from the clutch driven gear 125, and the ratchet portion 123a of the drive-side engaging member 123 and the ratchet portion 125a of the clutch driven gear 125 move apart. Therefore, the clutch unit 120 enters the non-transmission state shown in Figure 7(b).

[0067] Furthermore, when the cam gear member 126 rotates and the phase difference between the cam portion 126a of the cam gear member 126 and the top surface portion 127a1 of the release member 127 is shifted, the biasing force of the biasing member 124 causes the drive-side engaging member 123 to move toward the clutch driven gear 125. At this time, the cam portion 126a of the cam gear member 126 comes into contact with the bottom surface portion 127a2 of the release member 127. As a result, the ratchet portion 123a of the drive-side engaging member 123 and the ratchet portion 125a of the clutch driven gear 125 engage, and the clutch unit 120 enters the transmission state shown in Figure 7(a).

[0068] (Second drive transmission unit) Next, the configuration of the second drive transmission unit 250 provided in the main body 1A will be described using Figures 8(a) to 10(c). Figure 8(a) is an exploded perspective view showing the second drive transmission unit 250, and Figure 8(b) is an exploded perspective view showing the first brake engagement member 204, the second brake engagement member 208, and the brake transmission member 207. Figure 9 is a cross-sectional view showing the second drive transmission unit 250. Figure 10(a) is a perspective view showing the drum drive coupling 180, and Figure 10(b) is a perspective view showing the drum drive coupling 180 and the coupling engagement parts 204b and 208b. Figure 10(c) is a perspective view showing how the coupling engagement parts 204b and 208b rotate within the through hole 180f.

[0069] As shown in Figures 8(a) and 9, the second drive transmission unit 250 includes a drum drive transmission unit 203 as a drive transmission section, a brake force application unit 260 as a brake force application section, a brake section 206, a rotating shaft 215, and a gear 220. Also, as shown in Figure 9, the main body of the device 1A includes drive frames 101 and 102 which are fixed members, and a bearing member 202 which is fixed to the drive frame 101.

[0070] The drive frames 101 and 102 are made of sheet metal and extend in the radial direction RD, which is a direction of intersection (orthogonal) to the axial direction MD. The drive frames 101 and 102 are arranged with a gap between them in the axial direction MD. The radial direction RD is the radial direction of a virtual circle C centered on the rotation axis M1. In this embodiment, the radial direction RD is a direction perpendicular to the axial direction MD. The bearing member 202 is fixed to the drive frame 101 so as not to rotate around the rotation axis M1.

[0071] The rotation axis M1 of the drum drive transmission unit 203 extends in the axial direction MD and is coaxial with the rotation axis of the drum coupling 63. Furthermore, the axial direction MD is parallel to the longitudinal direction LD of the cartridge P shown in Figure 3. In the following, the direction from the drive frame 101 toward the drive gear 201 of the drum drive transmission unit 203 is referred to as the first direction M1B, and the direction from the drive frame 101 toward the gear 216 is referred to as the second direction M1B. The first direction M1A and the second direction M1B are opposite directions.

[0072] The bearing member 202 has a cylindrical portion 202a extending in the second direction M1B. The drum drive transmission unit 203 includes a drive gear 201 and a drum drive coupling 180. The drive gear 201 has a mating portion 201a recessed in the first direction M1A, and a plurality (three in this embodiment) of recesses 201b provided in the mating portion 201a and recessed in the radial direction RD. The three recesses 201b are arranged at equal intervals in the circumferential direction with respect to the rotation axis M1. The drive gear 201 is rotatably supported on the cylindrical portion 202a of the bearing member 202 and rotates when rotational drive is transmitted from the motor M.

[0073] The drum drive coupling 180 has a cylindrical portion 180c that extends in the axial direction MD and is formed in a cylindrical shape, a flange portion 180a, and a positioning boss 180i. The flange portion 180a is provided at the end of the cylindrical portion 180c in the first direction M1A, and the positioning boss 180i is provided at the end of the cylindrical portion 180c in the second direction M1B. The flange portion 180a is provided with a plurality (three in this embodiment) of protrusions 180b that project in the radial direction RD. The flange portion 180a fits into the mating portion 201a of the drive gear 201 in the first direction M1A, and each protrusion 180b engages with each recess 201b of the bearing member 202 described above. As a result, the drum drive coupling 180 rotates together with the drive gear 201 around the rotation axis M1. The positioning boss 180i engages with the circular hole 63a (see Figure 4) of the drum coupling 63 when the cartridge P is mounted on the device body 1A.

[0074] Furthermore, as shown in Figure 10(a), the drum drive coupling 180 is provided with drive transmission surfaces 180d, 180d and through holes 180f, 180f that penetrate in the axial direction MD around the positioning boss 180i. The drive transmission surfaces 180d, 180d are arranged 180 degrees apart from each other in the circumferential direction around the rotation axis M1, and the through holes 180f, 180f are also arranged 180 degrees apart from each other in the circumferential direction around the rotation axis M1. The drive transmission surfaces 180d, 180d can engage with the drive force receiving portion 63b of the drum coupling 63.

[0075] As shown in Figure 8(a), the brake force application unit 260, which serves as the brake force application section, includes gears 216 and 217, a brake transmission shaft 209, a spring holding member 214, a first brake engagement member 204, and a second brake engagement member 208. The brake force application unit 260 also includes a brake transmission member 207, a brake engagement spring 211, and a drum drive coupling spring 210. The spring holding member 214, the first brake engagement member 204, the second brake engagement member 208, the brake transmission member 207, the brake engagement spring 211, and the drum drive coupling spring 210 are arranged in the internal space of the cylindrical portion 180c of the drum drive coupling 180.

[0076] As shown in Figures 8(a) and 9, the brake transmission shaft 209 has a shaft portion 209c extending in the axial direction MD, an engagement pin 209b fixed to the shaft portion 209c and extending in the radial direction RD, and a groove portion 209a formed in the shaft portion 209c and extending in the axial direction MD. The shaft portion 209c passes through the cylindrical portion 202a of the bearing member 202 and rotatably supports the spring holding member 214, which will be described later. The engagement pin 209b is provided at the downstream end of the brake transmission shaft 209 in the first direction M1A, and the groove portion 209a is provided at the upstream end of the brake transmission shaft 209 in the first direction M1A. For this reason, the engagement pin 209b and the groove portion 209a are arranged on opposite sides of the drive frame 101 in the axial direction MD.

[0077] The engagement pin 209b engages with the engagement portion 216a of the gear 216, which is pivotally supported on the brake transmission shaft 209. As a result, the gear 216 and the brake transmission shaft 209 rotate together. In addition, a rotating shaft 215 is fixed to the drive frames 101 and 102. The rotating shaft 215 extends parallel to the rotation axis M1 and also extends along a rotation axis M2, which is located at a different position radially RD from the rotation axis M1. The inner ring 206b of the brake portion 206 is fixed to the rotating shaft 215.

[0078] The brake section 206 has an outer ring 206a as a first rotating member and an inner ring 206b as a second rotating member housed within the outer ring 206a. That is, the brake section 206 is positioned offset from the rotation axis M1 in the radial direction RD. The inner ring 206b has an engagement hole 206c that engages with an engagement pin 215a fixed to the rotation shaft 215. The engagement of the engagement pin 215a and the engagement hole 206c mounts the inner ring 206b so that it cannot rotate relative to the rotation shaft 215. That is, the inner ring 206b and the brake transmission shaft 209 are configured to rotate together around the rotation axis M2. The inner ring 206b is also driven and connected to the developing drive gear 111 (see Figure 5) via the rotation shaft 215 and gear 220. The outer ring 206a can rotate relative to the inner ring 206b when a torque exceeding a predetermined level is applied.

[0079] When the outer ring 206a rotates relative to the inner ring 206b, the outer ring 206a rotates while receiving a braking force (load) in the rotational direction from the inner ring 206b. The method of generating the braking force can be appropriately selected, such as friction or viscosity. In this embodiment, a torque limiter is applied to the braking section 206. For example, the torque limiter limits the torque transmitted from the input side to the output side to a predetermined limit value by utilizing, for example, the frictional force between a built-in spring and the inner ring. When the torque acting on the outer ring 206a is less than or equal to the predetermined limit value, the outer ring 206a and the inner ring 206b attempt to rotate together. Alternatively, a rotary damper that utilizes the braking force generated by the viscous resistance of oil may be applied as the braking section 206.

[0080] Furthermore, the outer ring 206a has a protrusion 206d, and the protrusion 206d engages with an engaging portion 217a provided on the gear 217, causing it to rotate together with the gear 217. In other words, the outer ring 206a and the gear 217 are configured to rotate around the rotation axis M2. The protrusion 206d and the engaging portion 217a are engaged, for example, by spline.

[0081] Gear 217 has a gear portion 217c and a housing portion 217d that houses the brake portion 206. The gear portion 217c meshes with the gear portion 216c of gear 216. The housing portion 217d is located inside the radial RD of the gear portion 217c, that is, on the rotation axis M2 side of the gear portion 217c.

[0082] The grooves 209a provided on the brake transmission shaft 209 are formed by splinting the shaft portion 209c. Multiple grooves 209a are formed in the circumferential direction centered on the rotation axis M1, but there may be just one groove 209a. The protrusions 207c of the brake transmission member 207 are spline-engaged in the grooves 209a. The protrusions 207c project inward in the radial direction RD from the inner circumferential surface of the brake transmission member 207, and there are the same number of protrusions as the grooves 209a. The spline engagement between the grooves 209a and the protrusions 207c configures the brake transmission member 207 to rotate integrally with the brake transmission shaft 209 around the rotation axis M1, and to be movable axially MD relative to the brake transmission shaft 209.

[0083] Furthermore, as shown in Figure 8(b), the brake transmission member 207 has a shaft portion 207b extending in the axial direction MD, and a flange portion 207a extending radially RD from the downstream end of the shaft portion 207b in the second direction M1B. The flange portion 207a is provided with a plurality (four in this embodiment) of protrusions 207e projecting in the first direction M1A, and the plurality of protrusions 207e are arranged at equal intervals in the circumferential direction centered on the rotation axis M1.

[0084] As shown in Figures 8(a)(b) and 9, a drum drive coupling spring 210, which is a compression spring, is compressed between the end face 207d of the brake transmission member 207 in the first direction M1A and the spring holding member 214. The drum drive coupling spring 210 provides a repulsive force (biasing force, elastic force) to the spring holding member 214 and the brake transmission member 207 in a direction away from each other.

[0085] As shown in Figure 8(b), the first brake engaging member 204 has a flange portion 204a and a coupling engaging portion 204b that protrudes claw-shaped from the flange portion 204a in the second direction M1B.

[0086] The flange portion 204a has a protrusion 204e that engages with the projection 207e of the brake transmission member 207, and a recess 204c. In this embodiment, there are four protrusions 204e and two recesses 204c, but the number of these is not limited. The first brake engaging member 204 rotates integrally with the brake transmission member 207 around the rotation axis M1 by the engagement of the protrusions 204e with the projection 207e of the brake transmission member 207.

[0087] The second brake engaging member 208 has a flange portion 208a and a coupling engaging portion 208b that protrudes claw-shaped from the flange portion 208a in a second direction M1B. The coupling engaging portion 208b is positioned inside the coupling engaging portion 204b of the first brake engaging member 204 in the radial direction RD. In this embodiment, the second brake engaging member 208 has two coupling engaging portions 208b, but the number of coupling engaging portions 208b is not particularly limited. The flange portion 208a is provided with a protrusion 208c that protrudes in a first direction M1A. The second brake engaging member 208 rotates integrally with the first brake engaging member 204 around the rotation axis M1 by the engagement of the protrusion 208c with the recess 204c of the first brake engaging member 204. Furthermore, the first brake engaging member 204 and the second brake engaging member 208 are connected so as to move integrally in the axial direction MD as well. Therefore, the first brake engaging member 204 and the second brake engaging member 208 are sometimes collectively referred to simply as brake engaging members (204, 208).

[0088] As shown in Figure 9, the flange portion 207a of the brake transmission member 207 is positioned in the axial direction MD between the flange portion 204a of the first brake engagement member 204 and the flange portion 208a of the second brake engagement member 208. The flange portion 207a is sandwiched between the flange portions 204a and 208a with a gap G in the axial direction MD.

[0089] As shown in Figures 8(a) and 99, a compression spring, the brake engagement spring 211, is compressed between the spring retaining member 214 and the flange portion 204a of the first brake engagement member 204. The brake engagement spring 211 exerts a repulsive force (biasing force, elastic force) on the spring retaining member 214 and the first brake engagement member 204 in a direction away from each other. The spring retaining member 214 is biased in the first direction M1A by the brake engagement spring 211 and the drum drive coupling spring 210, and is therefore abutting against the end face of the cylindrical portion 202a of the bearing member 202.

[0090] Furthermore, as shown in Figures 8(b) and 9, the brake transmission member 207 has a boss portion 207f that protrudes in the second direction M1B. The brake transmission member 207 receives the biasing force of the brake engagement spring 211 via the flange portion 204a of the first brake engagement member 204, and also receives the biasing force of the drum drive coupling spring 210 directly. For this reason, the boss portion 207f of the brake transmission member 207 abuts against the abutment surface 180g of the drum drive coupling 180.

[0091] Furthermore, the drum drive coupling 180 is biased in the second direction M1B by the biasing force of the brake engagement spring 211 and the drum drive coupling spring 210 via the brake transmission member 207. As shown in Figure 9, the movement of the drum drive coupling 180 in the second direction M1B is restricted when the flange portion 180a abuts against the restricting portion 212 fixed to the drive frame 102. This prevents the drum drive coupling 180 from falling off the drive gear 201. In addition, when the drum drive coupling 180 receives a force in the first direction M1A from the outside, it is able to move in the first direction M1A within the range of the aforementioned play G, against the biasing force of the brake engagement spring 211 and the drum drive coupling spring 210.

[0092] As shown in Figure 10(b), the coupling engagement portion 204b of the first brake engagement member 204 and the coupling engagement portion 208b of the second brake engagement member 208 are exposed through the through hole 180f of the drum drive coupling 180. When the cartridge P is mounted on the device body 1A, the coupling engagement portions 204b and 208b face the drum coupling 63 through the through hole 180f.

[0093] The through-hole 180f is formed wider than the width of the coupling engagement portions 204b and 208b in the circumferential direction centered on the rotation axis M1. Therefore, as shown in Figure 10(c), the coupling engagement portions 204b and 208b are configured to be rotatable relative to the drum drive coupling 180 within the range of the through-hole 180f.

[0094] (Drum drive coupling and drive coupling of drum coupling) Next, the drive coupling of the drum drive coupling 180 and the drum coupling 63 will be described. Figure 11 is a cross-sectional view showing the state in which the drum drive coupling 180 and the drum coupling 63 are engaged. Figure 12 is an enlarged cross-sectional view showing the vicinity of the projection 63e of the drum coupling 63.

[0095] As shown in Figure 11, when the cartridge P is mounted on the device body 1A, the positioning boss 180i of the drum drive coupling 180 engages with the circular hole 63a of the drum coupling 63. At this time, the drum drive coupling 180 receives a force from the drum coupling 63 in the first direction M1A. As a result, the drum drive coupling 180 moves in the first direction M1A against the biasing force of the brake engagement spring 211 and the drum drive coupling spring 210. Since the boss portion 207f of the brake transmission member 207 abuts against the abutment surface 180g of the drum drive coupling 180, the brake transmission member 207 moves in the first direction M1A together with the drum drive coupling 180.

[0096] As the brake transmission member 207 moves in a direction that reduces the aforementioned play G (see Figure 9), the projection 207e of the brake transmission member 207 engages with the convex portion 204e of the first brake engagement member 204, as shown in Figure 11. As a result, the brake transmission member 207, the first brake engagement member 204, the second brake engagement member 208, and the brake transmission shaft 209, which constitute the brake force application unit 260, rotate together around the rotation axis M1. In addition, the inner ring 206b of the brake section 206 rotates together with the brake transmission shaft 209.

[0097] When the drive gear 201 is driven by the motor M in the direction of arrow A in Figure 5(8), the drum drive coupling 180, which is coupled to the drive gear 201, also rotates in the direction of arrow A. As a result, the drive transmission surface 180d of the drum drive coupling 180 engages with the drive force receiving portion 63b in the direction of arrow A, as shown in Figure 12, and presses the drive force receiving portion 63b in the direction of arrow A. In other words, the drum drive coupling 180 is an example of an engaging member that can engage with the drive force receiving portion 63b of the drum unit 68. When such rotational drive (rotational force) in the direction of arrow A is applied to the drive force receiving portion 63b, the drum unit 68, including the photosensitive drum 61 and the drum coupling 63, rotates in the direction of arrow A as the first rotational direction, as shown in Figure 4.

[0098] On the other hand, as the photosensitive drum 61 and drum coupling 63 rotate in the direction of arrow A, the brake force receiving portion 63c of the drum coupling 63 engages with the coupling engagement portions 204b and 208b. In other words, the first brake engagement member 204 and the second brake engagement member 208 engage with the brake force receiving portion 63c of the drum unit 68 in the direction of arrow B, which is a second rotational direction opposite to the direction of arrow A. That is, the first brake engagement member 204 and the second brake engagement member 208 are examples of brake engagement members that engage with the drum unit 68. The rotational drive of the motor M is transmitted from the drum drive coupling 180 to the drum coupling 63, and from the drum coupling 63 to the brake engagement members (204, 208). As described above, the first brake engagement member 204, the second brake engagement member 208, the brake transmission member 207, the brake transmission shaft 209, and the inner ring 206b of the brake portion 206 are driven and connected in the rotational direction around the rotation axis M1. Then, as the inner ring 206b rotates around the rotation axis M1 relative to the outer ring 206a, it generates a braking force to load the rotation of the photosensitive drum 61. This braking force is applied to the brake force receiving portion 63c via a brake force application unit 260, which includes the first brake engagement member 204 and the second brake engagement member 208.

[0099] As a result, the drum coupling 63 rotates in the direction of arrow A by the rotational drive it receives from the drum drive coupling 180, while receiving an appropriate load (braking force) from the first brake engaging member 204 and the second brake engaging member 208. In other words, the torque required to rotate the drum coupling 63 increases due to the load (braking force) generated by the brake unit 206. As a result, the torque required by the drum drive coupling 180 to rotate the drum unit 68 does not become too light, but is of an appropriate magnitude, and the rotation of the drum unit 68 becomes stable. That is, changes in the rotational drive it receives from the drum drive coupling 180 can suppress unstable rotation of the drum unit 68, such as the drum unit 68 suddenly rotating too fast.

[0100] (Drive transmission to the developing coupling) Next, the drive transmission from the motor M to the developing coupling 72 will be explained using Figures 13(a) to 14(b). Figure 13(a) is a schematic diagram showing the drive transmission path from the motor M to the developing coupling 72 when the clutch unit 120 is in the transmission state. Figure 13(b) is a schematic diagram showing the drive transmission path from the motor M to the developing coupling 72 when the clutch unit 120 is not in the transmission state. Figure 14(a) is a graph showing the torque applied to the developing coupling 72 according to a comparative example, and Figure 14(b) is a graph showing the torque applied to the developing coupling 72 according to this embodiment.

[0101] As shown in Figure 13(a), in this embodiment, the rotational drive of the motor M is transmitted to the developing coupling 72 via two paths: a first drive transmission path passing through the first drive transmission unit 150 and a second drive transmission path passing through the second drive transmission unit 250. More specifically, the first drive transmission path is the path through which the rotational drive output from the motor M is transmitted to the developing coupling 72 via the clutch unit 120 and the developing drive gear 111, etc. The second drive transmission path is the path through which the rotational drive output from the motor M is transmitted to the developing coupling 72 via the drum drive transmission unit 203, drum coupling 63, brake force application unit 260, brake section 206 and the developing drive gear 111, etc.

[0102] Here, the torque transmitted to the developing drive gear 111 via the first drive transmission unit 150 without going through the second drive transmission unit 250, that is, the torque transmitted to the developing coupling 72 through the first drive transmission path, is defined as the first torque TCL. The torque transmitted to the developing drive gear 111 via the second drive transmission unit 250, that is, the torque transmitted to the developing coupling 72 through the second drive transmission path, is defined as the second torque TB. The second torque TB is transmitted to the developing coupling 72 via the brake unit 206.

[0103] Furthermore, the torque required to drive the developing coupling 72 (the torque required to drive the developing unit 70) is defined as the third torque TD. That is, the developing coupling 72 is driven by a torque greater than or equal to the third torque TD. The value of the second torque TB is determined by the performance of the brake unit 206, which is composed of a torque limiter, and the value of the first torque TCL is determined by the performance of the motor M. Also, the rotational speed of the outer ring 206a of the brake unit 206 is defined as speed V1, and the rotational speed of the inner ring 206b of the brake unit 206 is defined as speed V2.

[0104] As shown in Figure 13(a), when the clutch unit 120 is in the transmission state, both the first torque TCL and the second torque TB are applied to the developing drive gear 111. At this time, the first torque TCL, the second torque TB, and the third torque TD satisfy the following relationship. TCL+TB≧TD ····(1) In other words, the sum of the first torque TCL and the second torque TB is greater than or equal to the third torque TD, and the developing coupling 72 is driven by both the first torque TCL and the second torque TB. In this description of the embodiment, the reduction ratio (speed increase ratio) between the developing drive gear 111 and the developing coupling 72 is considered to be 1.

[0105] Furthermore, in this embodiment, the velocities V1 and V2 satisfy the following relationship. V1>V2 ····(2) The specifications of each gear in the drive transmission mechanism 200 are set to satisfy equation (2) above. As a result, the outer ring 206a of the brake unit 206 rotates at a relatively faster speed than the inner ring 206b while receiving a braking force from the inner ring 206b. In other words, the inner ring 206b rotates at a speed V2 that is slower than the outer ring 206a but greater than 0. Thus, a braking force can be applied to the drum unit 68, and the rotation of the drum unit 68 can be stabilized.

[0106] On the other hand, as shown in Figure 13(b), when the clutch unit 120 is not transmitting, only the second torque TB is applied to the developing drive gear 111. In this embodiment, the brake unit 206, which consists of a torque limiter, is selected to satisfy the following relationship between the second torque TB and the third torque TD. To satisfy TBV2, the outer ring 206a rotates at a relatively faster speed than the inner ring 206b while receiving a braking force from the inner ring 206b. Furthermore, when the motor M is driven, the drum coupling 63 is driven whether the clutch unit 120 is in the transmission or non-transmission state. Therefore, a braking force can be applied to the drum unit 68, and the rotation of the drum unit 68 can be stabilized.

[0107] In the comparative example shown in Figure 14(a), the second drive transmission path is omitted, and rotational drive is transmitted from the motor M to the developing coupling 72 only through the first drive transmission path. That is, the developing coupling 72 is driven only by the first torque TCL. In this case, when the clutch unit 120 is switched from the transmission state to the non-transmission state, the torque applied to the developing coupling 72 changes from the first torque TCL, which is greater than the third torque TD required to drive the developing coupling 72, to zero.

[0108] On the other hand, in this embodiment, the developing coupling 72 is driven by both the first torque TCL and the second torque TB. That is, the first torque TCL in this embodiment can be smaller than the first torque TCL in the comparative example. In this embodiment, as shown in Figure 14(b), when the clutch unit 120 is switched from a transmission state to a non-transmission state, the torque applied to the developing coupling 72 changes from the sum of the first torque TCL and the second torque TB to only the second torque TB.

[0109] Thus, in this embodiment, even when the clutch unit 120 is transitioned to a non-transmission state, the second torque TB acts on the developing coupling 72, so that torque fluctuations when switching the clutch unit 120 from a transmission state to a non-transmission state can be suppressed. For this reason, the shock when switching the clutch unit 120 from a transmission state to a non-transmission state can be suppressed, deformation of the clutch unit 120 can be suppressed and noise generation from the clutch unit 120 can be reduced.

[0110] Furthermore, since the torque fluctuation acting on the developing unit 70 when switching the clutch unit 120 from a transmission state to a non-transmission state can be reduced, the risk of deformation of the cartridge P frame can be reduced. Also, since the required rigidity of the cartridge P frame can be reduced, the cartridge P can be made lighter or the toner capacity that can be contained in the cartridge P can be increased. In addition, since the second torque TB is always applied to the developing coupling 72 regardless of the state of the clutch unit 120, the position of the cartridge P can be stabilized and the positional accuracy of the cartridge P can be improved.

[0111] <Other Embodiments> Furthermore, in the above-described embodiment, the developing drive gear 111, to which rotational drive is transmitted by the first drive transmission unit 150 and the second drive transmission unit, was composed of a gear member, but is not limited to this. For example, instead of the developing drive gear 111, other rotating bodies such as a pulley to which drive is transmitted by a belt, or a member in which a gear part and a pulley part are integrated may be used.

[0112] Summary of this disclosure This disclosure includes at least the following: (Composition 1) An image forming apparatus for forming an image on a recording material, Power source and The first driven member and A second driven member, which is different from the first driven member, A first drive transmission unit that transmits rotational drive output from the drive source to the first driven member, the first drive transmission unit having a clutch mechanism that can transition between a transmission state in which rotational drive output from the drive source is transmitted to the first driven member and a non-transmission state in which rotational drive output from the drive source is not transmitted to the first driven member, The system includes a second drive transmission unit which is drive-connected to the first drive transmission unit, and which has a brake section that transmits the rotational drive output from the drive source to the second driven member and generates a braking force to apply a load to the rotation of the second driven member, The second drive transmission unit is connected to the first drive transmission unit between the clutch mechanism and the first driven member, When the clutch mechanism is in the transmission state, the first driven member is driven by both a first torque transmitted via the first drive transmission unit and a second torque transmitted via the brake portion of the second drive transmission unit. An image forming apparatus characterized by the following: (Configuration 2) The first driven member is driven by the application of a torque greater than or equal to the third torque. The sum of the first torque and the second torque is greater than or equal to the third torque. The second torque is smaller than the third torque. The image forming apparatus according to configuration 1, characterized in that it is a picture forming apparatus. (Composition 3) The second driven member is driven when the drive source is driven, and the clutch mechanism is driven in both the transmission state and the non-transmission state. An image forming apparatus according to configuration 1 or 2, characterized by the above. (Composition 4) The first driven member is a developing coupling for driving a developing roller that carries toner. An image forming apparatus according to any one of configurations 1 to 3, characterized by the above. (Composition 5) The second driven member is a drum coupling for driving a photosensitive drum that carries a toner image. An image forming apparatus according to any one of configurations 1 to 4, characterized by the above. (Composition 6) The device body includes the drive source, the first drive transmission unit and the second drive transmission unit, The device further comprises a detachable unit that includes the first driven member and the second driven member and is detachably attached to the main body of the device, An image forming apparatus according to any one of configurations 1 to 5, characterized by the above. (Composition 7) The clutch mechanism further comprises an actuator for switching between the transmission state and the non-transmission state. An image forming apparatus according to any one of configurations 1 to 6, characterized by the features described herein. (Composition 8) The aforementioned brake unit includes a torque limiter, An image forming apparatus according to any one of configurations 1 to 7, characterized by the above. (Composition 9) The first drive transmission unit includes a rotatable rotating body, wherein when the clutch mechanism is in the transmission state, rotational drive output from the drive source is transmitted to the rotating body, and when the clutch mechanism is in the non-transmission state, rotational drive output from the drive source is not transmitted to the rotating body. The brake unit comprises a first rotating member to which rotational drive output from the drive source is input, and a second rotating member that is driven and connected to the rotating body. The first rotating member rotates relative to the second rotating member while receiving the braking force, The second rotating member rotates at a slower speed than the first rotating member when the clutch mechanism is in the transmission state, and stops together with the first driven member and the rotating body when the clutch mechanism is in the non-transmission state. An image forming apparatus according to any one of configurations 1 to 8, characterized by the above. (Composition 10) The second drive transmission unit has a braking force application unit that applies the braking force to the second driven member. An image forming apparatus according to any one of configurations 1 to 9, characterized by the above. (Composition 11) The second drive transmission unit has an engaging member that can engage with the second driven member, The braking force application unit has a brake engagement member that engages with the second driven member. The image forming apparatus according to configuration 10, characterized in that... (Composition 12) The second driven member rotates in the first rotational direction when rotational drive is transmitted to it via the second drive transmission unit. The engaging member engages with the second driven member in the first rotational direction, The brake engaging member engages with the second driven member in a second rotational direction opposite to the first rotational direction. The image forming apparatus according to configuration 11, characterized by the features described above. (Composition 13) The second drive transmission unit has a drive transmission section that transmits the rotational drive output from the drive source to the second driven member, The second torque is transmitted from the drive source to the second driven member via the drive transmission unit, the second driven member, the brake force application unit, and the brake unit. An image forming apparatus according to any one of the configurations 10 to 12 characterized by the above. [Explanation of Symbols]

[0113] 1: Image forming apparatus (printer) / 1A: Main unit / 50: Detachable unit (tray unit) / 61: Photosensitive drum / 63: Second driven member (drum coupling) / 72: First driven member (developer coupling) / 111: Rotating body (developer drive gear) / 120: Clutch mechanism (clutch unit) / 150: First drive transmission unit (first drive transmission unit) / 180: Engaging member (drum drive coupling) / 203: Drive transmission unit (drive transmission unit) / 204, 208: Brake engagement part Material (first brake engaging member, second brake engaging member) / 206: Brake section / 206a: First rotating member (outer ring) / 206b: Second rotating member (inner ring) / 250: Second drive transmission section (second drive transmission unit) / 260: Brake force application section (brake force application unit) / A: First rotation direction (direction) / B: Second rotation direction (direction) / M: Drive source (motor) / P: Detachable unit (cartridge) / S: Recording material (sheet) / TB: Second torque / TD: Third torque / TCL: First torque

Claims

1. An image forming apparatus for forming an image on a recording material, Power source and The first driven member and A second driven member different from the first driven member, A first drive transmission unit that transmits rotational drive output from the drive source to the first driven member, the first drive transmission unit having a clutch mechanism that can transition between a transmission state in which rotational drive output from the drive source is transmitted to the first driven member and a non-transmission state in which rotational drive output from the drive source is not transmitted to the first driven member, The second drive transmission unit is drive-connected to the first drive transmission unit and has a brake section that transmits the rotational drive output from the drive source to the second driven member and generates a braking force to apply a load to the rotation of the second driven member. The second drive transmission unit is connected to the first drive transmission unit between the clutch mechanism and the first driven member, When the clutch mechanism is in the transmission state, the first driven member is driven by both a first torque transmitted via the first drive transmission unit and a second torque transmitted via the brake portion of the second drive transmission unit. An image forming apparatus characterized by the following:

2. The first driven member is driven by the application of a torque greater than or equal to the third torque. The sum of the first torque and the second torque is greater than or equal to the third torque. The second torque is smaller than the third torque. The image forming apparatus according to feature 1.

3. The second driven member is driven when the drive source is driven, and the clutch mechanism is driven in both the transmission state and the non-transmission state. The image forming apparatus according to feature 1.

4. The first driven member is a developing coupling for driving a developing roller that carries toner. The image forming apparatus according to feature 1.

5. The second driven member is a drum coupling for driving a photosensitive drum that carries a toner image. The image forming apparatus according to feature 1.

6. The device body includes the drive source, the first drive transmission unit and the second drive transmission unit, The device further comprises a detachable unit which includes the first driven member and the second driven member and is detachably attached to the main body of the device, The image forming apparatus according to feature 1.

7. The clutch mechanism further comprises an actuator for switching between the transmission state and the non-transmission state. The image forming apparatus according to feature 1.

8. The aforementioned brake unit includes a torque limiter, The image forming apparatus according to feature 1.

9. The first drive transmission unit includes a rotatable rotating body, wherein when the clutch mechanism is in the transmission state, rotational drive output from the drive source is transmitted to the rotating body, and when the clutch mechanism is in the non-transmission state, rotational drive output from the drive source is not transmitted to the rotating body. The brake unit comprises a first rotating member to which rotational drive output from the drive source is input, and a second rotating member that is driven and connected to the rotating body. The first rotating member rotates relative to the second rotating member while receiving the braking force, The second rotating member rotates at a slower speed than the first rotating member when the clutch mechanism is in the transmission state, and stops together with the first driven member and the rotating body when the clutch mechanism is in the non-transmission state. The image forming apparatus according to feature 1.

10. The second drive transmission unit has a braking force applying unit that applies the braking force to the second driven member. The image forming apparatus according to feature 1.

11. The second drive transmission unit has an engaging member that can engage with the second driven member, The braking force application unit has a brake engagement member that engages with the second driven member. The image forming apparatus according to feature 10.

12. The second driven member rotates in the first rotational direction when rotational drive is transmitted to it via the second drive transmission unit. The engaging member engages with the second driven member in the first rotational direction, The brake engaging member engages with the second driven member in a second rotational direction opposite to the first rotational direction. The image forming apparatus according to feature 11.

13. The second drive transmission unit has a drive transmission section that transmits the rotational drive output from the drive source to the second driven member, The second torque is transmitted from the drive source to the second driven member via the drive transmission unit, the second driven member, the brake force application unit, and the brake unit. The image forming apparatus according to any one of claims 10 to 12.

Images