Drum unit

Abstract

To provide a drum unit that can suppress vibrations in the developing cartridge. [Solution] The drum unit 50 is detachable from the main body housing of the image forming apparatus. The drum unit 50 comprises a photosensitive drum 51 rotatable around a drum shaft 51X extending in the axial direction, a drum frame 53 that holds the photosensitive drum 51, and a drum frame 53 to which a developing cartridge 60 having a developing roller 61 rotatable around a developing roller shaft 61X extending in the axial direction can be attached and detached, a support member 130 that contacts the developing cartridge 60 from below and supports the developing cartridge 60 when the developing cartridge 60 is mounted on the drum frame 53, and an elastic member 140 that biases the support member 130 toward the developing cartridge 60, the elastic member 140 biasing the support member 130 in a first biasing direction F1 which is perpendicular to the axial direction.

Description

Technical Field

[0001] The present disclosure relates to a drum unit. Background Art

[0002] Conventionally, there has been known an image forming apparatus comprising a main body housing, a drum unit attachable to and detachable from the main body housing, and a developing cartridge attachable to and detachable from the drum unit (Patent Document 1). According to this technology, the drum unit includes a support member that supports the developing cartridge when the developing cartridge is mounted on the drum unit. The support member is a roller rotatably held. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2024-116676 Summary of the Invention Problems to be Solved by the Invention

[0004] Incidentally, when the developing cartridge is driven, for example during printing, if the developing cartridge vibrates, the nip pressure between the photosensitive drum and the developing roller may vary, for example. Therefore, it is desired to be able to suppress vibration of the developing cartridge. Means for Solving the Problems

[0005] According to a first disclosure of the present application, a drum unit is attachable to and detachable from a main body housing of an image forming apparatus. The drum unit includes a photosensitive drum, a drum frame, a support member, and an elastic member. The photosensitive drum is rotatable around an axially extending drum shaft. The drum frame holds the photosensitive drum. A developing cartridge having a developing roller rotatable around an axially extending developing roller shaft is attachable to and detachable from the drum frame. The support member supports the developing cartridge by contacting it from below while the developing cartridge is mounted on the drum frame. The elastic member biases the support member toward the developing cartridge. The elastic member biases the support member in a first biasing direction which is perpendicular to the axial direction.

[0006] The drum unit comprises a support member and an elastic member. This allows the developing cartridge to be elastically supported, thereby suppressing vibrations of the developing cartridge.

[0007] In the second disclosure of this application, in the drum unit of the first disclosure, the elastic member biases the support member in a direction perpendicular to the axial direction, which is the first biasing direction, and in a direction intersecting the direction in which the developing roller presses against the photosensitive drum.

[0008] In the third disclosure of this application, in the drum unit of the first or second disclosure, the support member has a spherical shape on the surface that contacts the developing cartridge.

[0009] The support member has a spherical shape on the surface that contacts the developing cartridge. This reduces the sliding resistance between the support member and the developing cartridge.

[0010] In the fourth disclosure of this application, in the drum unit of the first or second disclosure, the support member includes a first support member and a second support member. The first support member contacts one end of the developing cartridge from below, in the axial direction, when the developing cartridge is mounted on the drum frame. The second support member contacts the other end of the developing cartridge in the axial direction from below when the developing cartridge is mounted on the drum frame. The elastic member includes a first elastic member and a second elastic member. The first elastic member biases the first support member toward the developing cartridge. The first elastic member biases the first support member in the first biasing direction. The second elastic member biases the second support member toward the developing cartridge. The second elastic member biases the second support member in the first biasing direction.

[0011] The support member includes a first support member and a second support member, and the elastic member includes a first elastic member and a second elastic member. This allows the developing cartridge to be stably supported, thereby suppressing vibrations of the developing cartridge in a stable manner.

[0012] In the fifth disclosure of this application, in the drum unit of the fourth disclosure, the developing cartridge has a first color and a second color. The first collar protrudes in one direction along the axial direction. The second collar protrudes toward the other side in the axial direction. The drum frame has a first guide and a second guide. The first guide positions the developing cartridge in the mounting position when it is mounted on the drum frame. The first guide also guides the first color. The second guide positions the developing cartridge in the mounting position when it is mounted on the drum frame. The second guide also guides the second color.

[0013] The support member includes a first support member and a second support member, and the drum frame has a first guide and a second guide. This allows for more stable support of the developing cartridge, thereby suppressing vibrations of the developing cartridge in a more stable manner.

[0014] In the sixth disclosure of this application, in the drum unit of the first or second disclosure, the drum frame comprises a first side frame, a second side frame, and a resin frame. The first side frame is located on one side in the axial direction relative to the photosensitive drum. The second side frame is located on the other side in the axial direction relative to the photosensitive drum. The resin frame is positioned between the first side frame and the second side frame, and is attached to the first side frame. The resin frame has a guide and holds a supporting member and an elastic member. The guide positions the developing cartridge at the mounting position when the developing cartridge is mounted to the drum frame.

[0015] The resin frame has a guide and holds the supporting member. This allows positioning of the developing cartridge and holding of the supporting member to be achieved with a single component, the resin frame. This can suppress variation in the positions of the developing cartridge and the supporting member caused by multiple components.

[0016] In the seventh disclosure of the present application, in the drum unit according to the first disclosure or the second disclosure, the elastic member is a compression coil spring positioned between the supporting member and the drum frame. The compression coil spring is shorter than its natural length in a state where the developing cartridge is not mounted to the drum frame.

[0017] The compression coil spring serving as the elastic member is shorter than its natural length in a state where the developing cartridge is not mounted. This allows an initial load to be applied to the elastic member. Thereby, in a state where the developing cartridge is mounted, the developing cartridge can be constantly biased via the supporting member.

[0018] In the eighth disclosure of the present application, in the drum unit according to the first disclosure or the second disclosure, the supporting member has a pair of hooks. The pair of hooks extend in a direction away from the developing cartridge. Each of the pair of hooks has a claw at a distal end portion thereof. The claws project outward in the direction in which the pair of hooks face each other and engage with the drum frame.

[0019] The supporting member has a pair of hooks. This allows easy attachment of the supporting member. After the supporting member is attached, the claws catch on the drum frame, so that detachment of the supporting member from the drum frame can be suppressed.

[0020] In the ninth disclosure of the present application, in the drum unit according to the third disclosure, the developing cartridge is movable between a contact position and a separated position relative to the drum frame while being in contact with the support member. In the contact position, the developing roller is in contact with the photosensitive drum. In the separated position, the developing roller is separated from the photosensitive drum.

[0021] In a configuration where the sliding resistance between the support member and the developing cartridge is small, the developing cartridge is movable between the contact position and the separated position while being in contact with the support member. This allows the developing cartridge to move smoothly between the contact position and the separated position.

[0022] In the tenth disclosure of the present application, the drum unit according to the first disclosure or the second disclosure further comprises a pressing member and a spring. The pressing member contacts the developing cartridge in a state where the developing cartridge is mounted on the drum frame. The spring biases the pressing member toward the developing cartridge. The spring biases the pressing member in a second biasing direction, which is a direction orthogonal to the axial direction and is the direction in which the developing roller is pressed against the photosensitive drum.

[0023] The drum unit comprises the pressing member and the spring, whereby the developing roller can be pressed against the photosensitive drum.

[0024] In the eleventh disclosure of the present application, the developing cartridge is detachably attachable to a drum unit having a photosensitive drum rotatable around a drum shaft extending in the axial direction. The developing cartridge comprises a developing roller, a support member, and an elastic member. The developing roller is rotatable around a developing roller shaft extending in the axial direction. The support member contacts the drum unit from above in a state where the developing cartridge is mounted on the drum unit. The elastic member biases the support member toward the drum unit. The elastic member biases the support member in a direction orthogonal to the axial direction and intersecting the direction in which the developing roller is pressed against the photosensitive drum.

[0025] The developing cartridge comprises a support member and an elastic member. This allows the developing cartridge to be elastically brought into contact with the drum unit, thereby suppressing vibrations of the developing cartridge. [Effects of the Invention]

[0026] This can suppress vibrations in the developing cartridge. [Brief explanation of the drawing]

[0027] [Figure 1] This is a diagram showing the schematic configuration of an image forming apparatus. [Figure 2] This is a perspective view showing the drum unit and developing cartridge. [Figure 3] This is a cross-sectional view corresponding to the III-III section in Figure 2, showing the developing cartridge located in contact with the drum unit. [Figure 4] This is a cross-sectional view showing the developing cartridge located at a distance from the drum unit. [Figure 5] (a) is a perspective view showing the support member and elastic member, and (b) is a cross-sectional view showing the support member and elastic member in a state where they are held by the drum frame. [Figure 6] This is a cross-sectional view corresponding to the VI-VI section in Figure 3, showing the drum frame and developing cartridge. [Figure 7] This is a cross-sectional view corresponding to section VII-VII in Figure 3, showing the drum frame and developing cartridge. [Figure 8] This is a perspective view showing the first side frame, the second side frame, the first resin frame, and the second resin frame. [Figure 9] This is a view of the first resin frame from the inside in the first direction. [Figure 10] This is a view of the second resin frame from the inside in the first direction. [Figure 11] This is a perspective view of the drum unit from above. [Figure 12] This is a diagram showing a modified version of a developing cartridge. [Modes for carrying out the invention]

[0028] Next, embodiments will be described. As shown in Figure 1, the image forming apparatus 1 is a color printer capable of forming color images on a sheet S such as paper. The image forming apparatus 1 comprises a main body housing 10, a main body cover 11, a sheet supply unit 20, and an image forming unit 30.

[0029] In the referenced drawings, the first direction (see Figure 2), the second direction, and the third direction are indicated by arrows, with the arrow indicating one direction and the other by the arrowless direction. In this embodiment, the first direction corresponds to the "axial direction".

[0030] The second direction is the direction that intersects the first direction. The angle between the first and second directions is preferably 45 to 135 degrees, more preferably 80 to 100 degrees, and even more preferably 90 degrees. In the embodiment, the second direction is perpendicular to the first direction.

[0031] The third direction is a direction that intersects both the first and second directions. The angle between the first and third directions is preferably 45 to 135 degrees, more preferably 80 to 100 degrees, and even more preferably 90 degrees. The angle between the second and third directions is preferably 45 to 135 degrees, more preferably 80 to 100 degrees, and even more preferably 90 degrees. In the embodiment, the third direction is orthogonal to both the first and second directions. In the embodiment, the third direction corresponds to the up and down direction. One side of the third direction corresponds to the up side, and the other side of the third direction corresponds to the down side.

[0032] The main housing 10 has an opening 10A. The main cover 11 opens and closes the opening 10A. The main cover 11 is movable relative to the main housing 10 between a closed position shown by a solid line and an open position shown by a dashed line. Specifically, the main cover 11 is rotatable relative to the main housing 10 between the closed position and the open position. The closed position is the position in which the opening 10A is closed. The open position is the position in which the opening 10A is opened.

[0033] The sheet supply unit 20 includes a sheet tray 21 and a sheet supply mechanism 22. The seat tray 21 accommodates the seat S. The sheet supply mechanism 22 includes a pickup roller 23, a separation roller 24, a separation pad 25, a transport roller 26, and a registration roller 27.

[0034] The pickup roller 23 pushes the seat S out of the seat tray 21. The separation roller 24 and separation pad 25 separate the sheet S fed out by the pickup roller 23 into individual sheets. The transport roller 26 and registration roller 27 transport the sheet S to the image forming unit 30.

[0035] The image forming unit 30 comprises an exposure unit 40, a drum unit 50, four developing cartridges 60, a transfer unit 70, and a fixing unit 80. The exposure unit 40 includes a light source, a deflector, a lens, a mirror, and the like. The exposure unit 40 emits a light beam as shown by the dashed line to expose the surface of the photosensitive drum 51.

[0036] The drum unit 50 includes four photosensitive drums 51, four chargers 52, and a drum frame 53. A toner image is formed on the surface of the photosensitive drum 51. The photosensitive drum 51 is rotatable around a drum shaft 51X extending in a first direction. The photosensitive drum 51 includes a photosensitive drum 51K, a photosensitive drum 51C, a photosensitive drum 51M, and a photosensitive drum 51Y.

[0037] The four photosensitive drums 51 are arranged in the order of photosensitive drum 51Y, photosensitive drum 51M, photosensitive drum 51C, and photosensitive drum 51K, from one end of the second direction to the other. The four photosensitive drums 51 are also arranged in the order of photosensitive drum 51Y, photosensitive drum 51M, photosensitive drum 51C, and photosensitive drum 51K, from upstream to downstream in the conveying direction of the sheet S.

[0038] The charger 52 charges the surface of the photosensitive drum 51. The drum frame 53 holds the photosensitive drum 51 and the charger 52. The developing cartridge 60 can be attached to and removed from the drum frame 53.

[0039] The drum unit 50 is detachable from the main body housing 10 of the image forming apparatus 1. Specifically, the drum unit 50 is detachable from the main body housing 10 through the opening 10A when the main body cover 11 is in the open position indicated by the dashed line.

[0040] The developing cartridge 60 includes a developing roller 61 and a developing housing 65. The developing roller 61 supplies toner to the photosensitive drum 51. The developing roller 61 is rotatable around a developing roller shaft 61X that extends in a first direction. The developing unit 65 houses the toner. The developing unit 65 holds the developing roller 61.

[0041] The developing cartridge 60 includes developing cartridge 60K, developing cartridge 60C, developing cartridge 60M, and developing cartridge 60Y.

[0042] The developing unit 65K houses the black toner. The developing roller 61K supplies the black toner to the photosensitive drum 51K. The developing unit 65C houses the cyan toner. The developing roller 61C supplies the cyan toner to the photosensitive drum 51C.

[0043] The developing unit 65M houses the magenta toner. The developing roller 61M supplies the magenta toner to the photosensitive drum 51M. The developing unit 65Y houses the yellow toner. The developing roller 61Y supplies the yellow toner to the photosensitive drum 51Y.

[0044] In this specification and the drawings, when the colors black, cyan, magenta, and yellow are distinguished for each component, the reference numerals K, C, M, and Y are used, respectively. When the colors of each component are not distinguished, the reference numerals K, C, M, and Y are not used.

[0045] The transfer unit 70 comprises a drive roller 71, a driven roller 72, an endless transfer belt 73, and four transfer rollers 74. The transfer belt 73 is stretched between the drive roller 71 and the driven roller 72. The outer surface of the transfer belt 73 is in contact with the photosensitive drum 51. The transfer roller 74 is positioned inside the transfer belt 73. The transfer roller 74 sandwiches the transfer belt 73 between itself and the photosensitive drum 51.

[0046] The fixing unit 80 includes a heating roller 81 and a pressure roller 82. The heating roller 81 heats the sheet S. The pressure roller 82 sandwiches the sheet S between itself and the heating roller 81.

[0047] The charger 52 charges the surface of the photosensitive drum 51. The exposure unit 40 emits a light beam onto the charged surface of the photosensitive drum 51. This forms an electrostatic latent image on the photosensitive drum 51 based on the image data. The developing roller 61 supplies toner to the surface of the exposed photosensitive drum 51. This forms a toner image on the photosensitive drum 51.

[0048] The photosensitive drum 51 and transfer roller 74 transport the sheet S supplied from the registration roller 27. This transfers the toner image formed on the photosensitive drum 51 to the sheet S. The heating roller 81 and pressure roller 82 transport the sheet S with the transferred toner image. This fixes the transferred toner image to the sheet S. The intermediate discharge roller 15 and discharge roller 16 discharge the sheet S with the fixed toner image to the discharge tray 13.

[0049] As shown in Figure 2, the developing cartridge 60 is detachable from the drum frame 53 of the drum unit 50. When mounted on the drum frame 53, the developing cartridge 60 is movable relative to the drum frame 53 between the contact position shown in Figure 3 and the separated position shown in Figure 4.

[0050] The contact position shown in Figure 3 is the position where the developing roller 61 contacts the photosensitive drum 51. The developing roller 61 can supply toner to the photosensitive drum 51 when the developing cartridge 60 is in the contact position. The separation position shown in Figure 4 is the position where the developing roller 61 is separated from the photosensitive drum 51.

[0051] As shown in Figure 3, the drum unit 50 further comprises a pressing member 110, a spring 120, a support member 130, and an elastic member 140. The pressing member 110, spring 120, support member 130, and elastic member 140 are separate components from the drum frame 53.

[0052] The pressing member 110 contacts the developing cartridge 60 when the developing cartridge 60 is mounted on the drum frame 53. The pressing member 110 is pivotably held on the drum frame 53. The pressing member 110 is pivotable about an axis 110X that extends in a first direction relative to the drum frame 53.

[0053] The spring 120 is, for example, a torsion coil spring. The spring 120 biases the pressing member 110 toward the developing cartridge 60. More specifically, the spring 120 biases the pressing member 110 in a second biasing direction F2. The second biasing direction F2 is perpendicular to the first direction and is the direction in which the developing roller 61 presses against the photosensitive drum 51. In this embodiment, the second biasing direction F2 is the other direction of the second direction and the other direction of the third direction, and is directed diagonally downward to the left in Figure 3.

[0054] The support member 130 is a member that supports the developing cartridge 60. The support member 130 contacts the developing cartridge 60 from below when the developing cartridge 60 is mounted on the drum frame 53. The support member 130 is slidably held on the drum frame 53. The support member 130 is slidable relative to the drum frame 53 in a direction parallel to the first biasing direction F1, which will be described later.

[0055] The elastic member 140 is, for example, a compression coil spring. The elastic member 140 biases the support member 130 toward the developing cartridge 60. More specifically, the elastic member 140 biases the support member 130 in a first biasing direction F1.

[0056] The first biasing direction F1 is perpendicular to the first direction. More specifically, the first biasing direction F1 is perpendicular to the first direction and intersects with the direction in which the developing roller 61 presses against the photosensitive drum 51. The angle between the first biasing direction F1 and the direction in which the developing roller 61 presses against the photosensitive drum 51 is preferably 45 to 135 degrees, more preferably 80 to 100 degrees, and even more preferably 90 degrees. In this embodiment, the first biasing direction F1 is the direction toward the upper left of Figure 3, toward the other side of the second direction and toward one side of the third direction. The first biasing direction F1 is substantially perpendicular to the plane PL connecting the drum axis 51X and the developing roller axis 61X.

[0057] As shown in Figures 5(a) and (b), the support member 130 has a contact portion 131 and a pair of hooks 132.

[0058] The contact portion 131 contacts the developing cartridge 60. The contact portion 131 protrudes toward the developing cartridge 60. The contact portion 131 has a contact surface 131A. The contact surface 131A is the surface that contacts the developing cartridge 60. The contact surface 131A of the contact portion 131 has a spherical shape. The support member 130 is made of a resin with higher sliding properties than the resin frames RF1 and RF2 (see Figure 6) described later.

[0059] Each hook 132 extends away from the developing cartridge 60. More specifically, each hook 132 extends in the opposite direction to the first biasing direction F1. A pair of hooks 132 face each other in the first direction. The distance between a pair of hooks 132 in the first direction increases towards the tip.

[0060] Each hook 132 has a claw 132A at its tip. The claws 132A engage with the drum frame 53. The claws 132A protrude outward from the tip of the hook 132 in the direction in which the pair of hooks 132 face each other. Specifically, the claws 132A protrude outward from the tip of the hook 132 in a first direction.

[0061] The support member 130 has a pair of hooks 132, each claw 132A of which engages with the drum frame 53. This prevents the support member 130 from detaching from the drum frame 53 in the first biasing direction F1.

[0062] The elastic member 140 is located between the support member 130 and the drum frame 53. More specifically, the elastic member 140 is located between the contact portion 131 and the drum frame 53. The elastic member 140 is shorter than the natural length shown by the dashed line when the developing cartridge 60 is not mounted on the drum frame 53. In other words, the elastic member 140 is subjected to an initial load when the developing cartridge 60 is not mounted on the drum frame 53.

[0063] The developing cartridge 60 is movable relative to the drum frame 53 while in contact with the support member 130, between the contact position shown in Figure 3 and the separated position shown in Figure 4. More specifically, the developing cartridge 60 is movable relative to the drum frame 53 while in contact with the contact surface 131A (see Figure 4) of the support member 130, between the contact position and the separated position.

[0064] The developing housing 65 has a supported surface 66. The supported surface 66 is the surface that contacts the support member 130. The supported surface 66 extends along the direction of movement when the developing cartridge 60 moves between a contact position and a separated position. The supported surface 66 intersects the first biasing direction F1. In this embodiment, the supported surface 66 is perpendicular to the first biasing direction F1.

[0065] As shown in Figure 6, the support member 130 includes a first support member 130A and a second support member 130B. The elastic member 140 includes a first elastic member 140A and a second elastic member 140B. The first support member 130A and the first elastic member 140A, and the second support member 130B and the second elastic member 140B have a symmetrical structure with respect to a plane perpendicular to the first direction.

[0066] The first support member 130A contacts one end of the developing cartridge 60 in the first direction from below when the developing cartridge 60 is mounted on the drum frame 53. The second support member 130B contacts the other end of the developing cartridge 60 in the first direction from below when the developing cartridge 60 is mounted on the drum frame 53.

[0067] More specifically, the supported surface 66 of the developing housing 65 includes a first supported surface 66A and a second supported surface 66B. The first supported surface 66A is located at one end of the developing housing 65 in the first direction. The second supported surface 66B is located at the other end of the developing housing 65 in the first direction.

[0068] The first support member 130A contacts the first supported surface 66A from below. The second support member 130B contacts the second supported surface 66B from below.

[0069] The first elastic member 140A biases the first support member 130A toward the developing cartridge 60. More specifically, the first elastic member 140A biases the first support member 130A in the first biasing direction F1. The second elastic member 140B biases the second support member 130B toward the developing cartridge 60. More specifically, the second elastic member 140B biases the second support member 130B in the first biasing direction F1.

[0070] As shown in Figure 7, the developing cartridge 60 further comprises a first color 67A and a second color 67B.

[0071] The first color 67A protrudes from the developing housing 65 toward one side in a first direction. The first color 67A has a cylindrical shape. The first color 67A covers one end of the shaft 61A of the developing roller 61 in a first direction.

[0072] The second color 67B protrudes from the developing housing 65 toward the other side in the first direction. The second color 67B has a bottomed cylindrical shape. The second color 67B covers the other end of the shaft 61A of the developing roller 61 in the first direction.

[0073] As shown in Figure 8, the drum frame 53 has a first side frame SF1, a second side frame SF2, four first resin frames RF1, and four second resin frames RF2. In this embodiment, the first resin frame RF1 corresponds to the "resin frame".

[0074] The first side frame SF1 is made of a metal plate. The first side frame SF1 is located on one side in a first direction relative to the photosensitive drum 51. The first side frame SF1 extends in a second direction.

[0075] The second side frame SF2 is made of a metal plate. The second side frame SF2 is located on the other side of the first direction relative to the photosensitive drum 51. The second side frame SF2 extends in the second direction. The first side frame SF1 and the second side frame SF2 face each other with a gap between them in the first direction.

[0076] The first resin frame RF1 is made of resin. The first resin frame RF1 is located between the first side frame SF1 and the second side frame SF2. The first resin frame RF1 is attached to the first side frame SF1 by screws SC.

[0077] The second resin frame RF2 is made of resin. The second resin frame RF2 is located between the first side frame SF1 and the second side frame SF2. The second resin frame RF2 is attached to the second side frame SF2 by screws SC.

[0078] The first resin frame RF1 and the second resin frame RF2 face each other with a gap between them in the first direction. As shown in Figure 7, the developing cartridge 60, when mounted on the drum frame 53, is located between the first resin frame RF1 and the second resin frame RF2. The developing cartridge 60, when mounted on the drum frame 53, is located between the first side frame SF1 and the second side frame SF2.

[0079] As shown in Figure 9, the first resin frame RF1 has a first guide G1. In this embodiment, the first guide G1 corresponds to a "guide". The first guide G1 is a groove that is recessed from one direction to the other in the first direction.

[0080] The first guide G1 positions the developing cartridge 60 in the mounting position when the developing cartridge 60 is mounted on the drum frame 53. The first guide G1 guides the first color 67A of the developing cartridge 60 when the developing cartridge 60 is mounted on the drum frame 53. The first guide G1 positions the first color 67A when the developing cartridge 60 is mounted on the drum frame 53.

[0081] The first resin frame RF1 holds the first support member 130A and the first elastic member 140A. The first resin frame RF1 holds the first support member 130A so that it can slide in a direction parallel to the first biasing direction F1. The first elastic member 140A is located between the first support member 130A and the first resin frame RF1.

[0082] As shown in Figure 10, the second resin frame RF2 has a second guide G2. The second guide G2 is a groove that is recessed from one direction to the other in the first direction.

[0083] The second guide G2 positions the developing cartridge 60 in the mounting position when the developing cartridge 60 is mounted on the drum frame 53. The second guide G2 guides the second color 67B of the developing cartridge 60 when the developing cartridge 60 is mounted on the drum frame 53. The second guide G2 positions the second color 67B when the developing cartridge 60 is mounted on the drum frame 53.

[0084] The second resin frame RF2 holds the second support member 130B and the second elastic member 140B. The second resin frame RF2 holds the second support member 130B so that it can slide in a direction parallel to the first biasing direction F1. The second elastic member 140B is located between the second support member 130B and the second resin frame RF2.

[0085] As shown in Figures 9 and 10, the pressing member 110 includes a first pressing member 110A and a second pressing member 110B. The spring 120 includes a first spring 120A and a second spring 120B. The first pressing member 110A and the first spring 120A, and the second pressing member 110B and the second spring 120B have a symmetrical structure with respect to a plane perpendicular to the first direction.

[0086] The first pressing member 110A contacts one end of the developing cartridge 60 in the first direction when the developing cartridge 60 is mounted on the drum frame 53. The first spring 120A biases the first pressing member 110A toward the developing cartridge 60. More specifically, the first spring 120A biases the first pressing member 110A in the second biasing direction F2.

[0087] The second pressing member 110B contacts the other end of the developing cartridge 60 in the first direction when the developing cartridge 60 is mounted on the drum frame 53. The second spring 120B biases the second pressing member 110B toward the developing cartridge 60. More specifically, the second spring 120B biases the second pressing member 110B in the second biasing direction F2.

[0088] As shown in Figure 11, the drum unit 50 has four first pressing members 110A, four first springs 120A, four first support members 130A, and four first elastic members 140A at one end in the first direction, corresponding to the four developing cartridges 60. The drum unit 50 has four second pressing members 110B, four second springs 120B, four second support members 130B, and four second elastic members 140B at the other end in the first direction.

[0089] Next, the effects and advantages of the embodiment will be described. The drum unit 50 includes a support member 130 and an elastic member 140. This allows the developing cartridge 60 to be elastically supported, thereby suppressing vibrations of the developing cartridge 60.

[0090] The support member 130 has a spherical contact surface 131A. This reduces the sliding resistance between the support member 130 and the developing cartridge 60.

[0091] As shown in Figure 6, the support member 130 includes a first support member 130A and a second support member 130B, and the elastic member 140 includes a first elastic member 140A and a second elastic member 140B. This allows the developing cartridge 60 to be stably supported, and thus vibrations of the developing cartridge 60 can be suppressed in a stable manner.

[0092] The support member 130 includes a first support member 130A and a second support member 130B, and the drum frame 53 has a first guide G1 and a second guide G2. As a result, as shown in Figures 6 and 7, the developing cartridge 60 can be supported at four locations: the first support member 130A, the second support member 130B, the first guide G1, and the second guide G2. This allows the developing cartridge 60 to be supported more stably, and thus vibrations of the developing cartridge 60 can be suppressed in a more stable manner.

[0093] The first resin frame RF1 has a first guide G1 and holds the first support member 130A. This allows the positioning of the developing cartridge 60 and the holding of the first support member 130A to be achieved with a single component, the first resin frame RF1. This suppresses variations in the position of the developing cartridge 60 and the first support member 130A caused by other components.

[0094] The second resin frame RF2 has a second guide G2 and holds the second support member 130B. This allows the positioning of the developing cartridge 60 and the holding of the second support member 130B to be achieved with a single component, the second resin frame RF2. This suppresses variations in the position of the developing cartridge 60 and the second support member 130B caused by other components.

[0095] The compression coil spring, acting as the elastic member 140, is shorter than its natural length when the developing cartridge 60 is not installed. This allows an initial load to be applied to the elastic member 140. As a result, when the developing cartridge 60 is installed, the developing cartridge 60 can be constantly biased via the support member 130. This allows vibrations of the developing cartridge 60 to be constantly suppressed.

[0096] The support member 130 has a pair of hooks 132. This makes it easy to attach the support member 130. After the support member 130 is attached, the claws 132A catch on the drum frame 53, which prevents the support member 130 from coming off the drum frame 53.

[0097] The configuration has low sliding resistance between the support member 130 and the developing cartridge 60, allowing the developing cartridge 60 to move between a contact position and a separated position while in contact with the support member 130. This allows the developing cartridge 60 to move smoothly between the contact position and the separated position.

[0098] The drum unit 50 includes a pressing member 110 and a spring 120. This allows the developing roller 61 to be pressed against the photosensitive drum 51.

[0099] The embodiments have been described above, but the drum unit and developing cartridge can be modified as appropriate, as illustrated below.

[0100] In the embodiment, the drum unit 50 included a support member 130 and an elastic member 140. However, for example, as shown in Figure 12, the developing cartridge 60 may also include a support member 130 and an elastic member 140.

[0101] The support member 130 contacts the drum unit 50 from above when the developing cartridge 60 is mounted on the drum unit 50. The support member 130 is slidably held in the developing housing 65. The support member 130 is slidable relative to the developing housing 65 in a direction parallel to the first biasing direction F1.

[0102] The drum frame 53 of the drum unit 50 has a contact surface 54. The contact surface 54 is the surface that the support member 130 contacts. The contact surface 54 extends along the direction of movement when the developing cartridge 60 moves between a contact position and a separated position. The contact surface 54 intersects the first biasing direction F1. In a modified example, the contact surface 54 is perpendicular to the first biasing direction F1.

[0103] The elastic member 140 biases the support member 130 toward the contact surface 54 of the drum unit 50. More specifically, the elastic member 140 biases the support member 130 in a first biasing direction F1. The first biasing direction F1 is perpendicular to the first direction and intersects with the direction in which the developing roller 61 presses against the photosensitive drum 51. The angle between the first biasing direction F1 and the direction in which the developing roller 61 presses against the photosensitive drum 51 is preferably 45 to 135 degrees, more preferably 80 to 100 degrees, and even more preferably 90 degrees. In a modified example, the first biasing direction F1 is a direction toward the lower left of Figure 12, toward one of the second directions and the other of the third direction.

[0104] The developing cartridge 60 is equipped with a support member 130 and an elastic member 140, which allows the developing cartridge 60 to be elastically brought into contact with the drum unit 50. This suppresses vibrations of the developing cartridge 60.

[0105] In this embodiment, the elastic member 140 was a compression coil spring. However, the elastic member may be a torsion coil spring, a leaf spring, or the like. Also, the elastic member may be made of rubber. Furthermore, the elastic member may be made of a foamed elastic material.

[0106] In this embodiment, the spring 120 that biases the pressing member 110 was a torsion coil spring. However, the spring that biases the pressing member may be a compression coil spring, a leaf spring, or the like.

[0107] In this embodiment, the image forming apparatus 1 was a printer capable of forming color images, but for example, the image forming apparatus may be a printer capable of forming only monochrome images. Alternatively, for example, the image forming apparatus may be a copier, a multifunction printer, or the like.

[0108] The elements described in the embodiments and modifications may be implemented in any combination. [Explanation of Symbols]

[0109] 1. Image forming apparatus 10 Main Unit 50 Drum Units 51 Photosensitive drum 51X Drum shaft 53 Drum Frame 60 developing cartridges 61 Developing roller 61X Developing roller shaft 130 Support member 140 Elastic members F1 1st biasing direction

Claims

1. A drum unit that can be attached to and detached from the main housing of an image forming apparatus, A photosensitive drum that is rotatable around a drum shaft extending in the axial direction, A drum frame for holding the photosensitive drum, the drum frame from which a developing cartridge having a developing roller rotatable around a developing roller axis extending in the axial direction can be attached and detached, A support member that contacts the developing cartridge from below and supports the developing cartridge when the developing cartridge is mounted on the drum frame, A drum unit comprising an elastic member that biases the support member toward the developing cartridge, wherein the elastic member biases the support member in a first biasing direction which is perpendicular to the axial direction.

2. The drum unit according to claim 1, characterized in that the elastic member biases the support member in a direction perpendicular to the axial direction, which is the first biasing direction, and in a direction intersecting the direction in which the developing roller presses against the photosensitive drum.

3. The drum unit according to claim 1 or 2, characterized in that the support member has a spherical shape on the surface that contacts the developing cartridge.

4. The aforementioned support member is A first support member that contacts one end of the developing cartridge in the axial direction from below when the developing cartridge is mounted on the drum frame, The development cartridge includes a second support member that contacts the other end of the development cartridge in the axial direction from below when the development cartridge is mounted on the drum frame, The elastic member is A first elastic member that biases the first support member toward the developing cartridge, comprising a first elastic member that biases the first support member in a first biasing direction, The drum unit according to claim 1 or 2, further comprising a second elastic member that biases the second support member toward the developing cartridge, the second elastic member that biases the second support member in the first biasing direction.

5. The aforementioned developing cartridge is A first collar protruding toward one side in the axial direction, It has a second collar that protrudes toward the other side in the axial direction, The drum frame is A first guide for positioning the developing cartridge in the mounting position when the developing cartridge is mounted on the drum frame, comprising a first guide for guiding the first color, The drum unit according to claim 4, further comprising a second guide for positioning the developing cartridge in the mounting position when the developing cartridge is mounted on the drum frame, the second guide for guiding the second color.

6. The drum frame is A first side frame located on one side in the axial direction relative to the photosensitive drum, A second side frame located on the other side in the axial direction relative to the photosensitive drum, It has a resin frame located between the first side frame and the second side frame and attached to the first side frame, The drum unit according to claim 1 or 2, wherein the resin frame has a guide for positioning the developing cartridge in the mounting position when the developing cartridge is mounted on the drum frame, and holds the support member and the elastic member.

7. The drum unit according to claim 1 or 2, wherein the elastic member is a compression coil spring located between the support member and the drum frame, and is shorter than the natural length when the developing cartridge is not mounted on the drum frame.

8. The drum unit according to claim 1 or 2, characterized in that the support member is a pair of hooks extending away from the developing cartridge, each having a claw at its tip that protrudes outward in the direction in which the pair of hooks face each other and engages with the drum frame.

9. The drum unit according to claim 3, characterized in that the developing cartridge is movable with respect to the drum frame between a contact position in which the developing roller contacts the photosensitive drum and a separation position in which the developing roller separates from the photosensitive drum, while in contact with the support member.

10. A pressing member that contacts the developing cartridge when the developing cartridge is mounted on the drum frame, The drum unit according to claim 1 or 2, further comprising a spring for biasing the pressing member toward the developing cartridge, the spring for biasing the pressing member in a second biasing direction which is perpendicular to the axial direction and in the direction in which the developing roller presses against the photosensitive drum.

Images