This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2015-241834 filed on Dec. 11, 2015, the entire contents of which are incorporated herein by reference.
The present disclosure relates to an image forming apparatus such as a copier or a multifunction peripheral, and in particular relates to an image forming apparatus including a photoconductor drum used in a process of forming an image on a sheet.
An image forming apparatus of an electrophotographic system includes a photoconductor drum on which a toner image is formed by a developing device. The toner image formed on the photoconductor drum is transferred to a transfer belt by a primary transfer device, and is further transferred from the transfer belt to a sheet by a secondary transfer device. The photoconductor drum is unitized into a drum unit together with a frame and the like, wherein the frame rotatably supports the photoconductor drum. The drum unit including the photoconductor drum is attached to the image forming apparatus in a detachable manner. There is known, as one example of conventional image forming apparatuses, an image forming apparatus to/from which the drum unit is inserted and pulled out horizontally.
As one example of such drum units, there is known a drum unit that includes a flange fixed to an end portion of the photoconductor drum in the axial direction. The flange is integrally formed with a gear portion that transmits a rotational driving force to another driven body.
An image forming apparatus according to an aspect of the present disclosure includes an apparatus main body, a drum unit, and a transfer belt. The drum unit is attached, in a detachable manner, to a predetermined attachment position inside the apparatus main body. The drum unit includes a cylindrical photoconductor drum and is configured to be inserted and pulled out horizontally with respect to the apparatus main body. The transfer belt is disposed above the photoconductor drum in such a way as to face and contact an outer circumferential surface of the photoconductor drum in a state where the drum unit is disposed at the attachment position. The drum unit includes a flange, a frame, a gear, and a guide member. The flange is integrally provided with the photoconductor drum by being fixed to an inner hole of a side end portion of the photoconductor drum, the side end portion being on a side of an insertion direction of the drum unit opposite to a pulling out direction. The frame is configured to rotatably support the photoconductor drum and cover a side of the photoconductor drum. The gear portion is integrally formed with an outer circumferential surface of the flange, wherein an outer diameter of the gear portion is larger than a diameter size of the photoconductor drum. The guide member is provided on an upper surface of the frame and extends in the insertion direction and the pulling out direction on both sides of an edge position, wherein the edge position is a position at which an edge portion, on the side of the insertion direction, of a surface of the transfer belt facing the photoconductor drum, is disposed in the state where the drum unit is disposed at the attachment position, and the guide member is configured to guide the edge portion upward when the drum unit is pulled out of the apparatus main body. An upper surface of the guide member includes a first guide surface and a second guide surface, wherein the first guide surface is located more on a side of a center of the photoconductor drum than the edge position, and the second guide surface is located more on the side of the insertion direction than the edge position. The first guide surface is lower than a height position of a lower end of the edge portion, and the second guide surface is higher than an upper-end position of the gear portion.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.
The following describes an embodiment of the present disclosure with reference to the attached drawings. It should be noted that the following embodiment is an example of a specific embodiment of the present disclosure and should not limit the technical scope of the present disclosure. It is noted that, for the sake of explanation, a vertical direction in an installed state of an image forming apparatus 10 where the image forming apparatus 10 is usable (the state shown in
The image forming apparatus 10 according to the present embodiment has at least a print function. The image forming apparatus 10 is a so-called tandem-type color printer.
As shown in
As shown in
Each of the image forming units 4 includes a developing device 31, a primary transfer roller 32, and a drum unit 50 including a photoconductor drum 51, and forms an image by the electrophotography system. The image forming units 4 are arranged in alignment along the front-rear direction 8 in the housing 10A, and form a color image based on a so-called tandem system. The image forming units 4 form a color toner image on a transfer belt 46 by transferring toner images of different colors from the photoconductor drums 51 to the transfer belt 46 such that the toner images are overlaid with each other. The toner image on the transfer belt 46 is transferred by the secondary transfer roller 20 to a printing sheet fed from the sheet feed cassette 24.
The intermediate transfer unit 5 is provided above the four image forming units 4. That is, the intermediate transfer unit 5 is provided above the four drum units 50. As shown in
Specifically, the transfer belt 46 is an annular belt member. The width of the transfer belt 46 is equal to the longitudinal length of the photoconductor drums 51. The transfer belt 46 includes a base layer portion and a surface layer portion that is formed on the surface of the base layer portion. The base layer portion is formed from a thermoplastic resin. For example, the thermoplastic resin is PC (polycarbonate), PVDF (polyvinylidene fluoride), PA (nylon), or PBT (polybutylene terephthalate). The surface layer portion is formed by coating the base layer portion with a thermosetting resin. For example, the thermosetting resin is PI (polyimide), PAI (polyamideimide), or AC (acrylic).
Each drum unit 50 includes a photoconductor drum 51. The photoconductor drum 51 is formed in a cylindrical shape, and is made by forming a thin photoconductive layer of an amorphous silicon (a-Si) photoconductive material on the surface of a blank pipe made of aluminum. That is, the photoconductive layer is formed on the surface of the photoconductor drum 51. An electrostatic latent image is formed on the photoconductive layer. The photoconductor drums 51 are disposed under the primary transfer rollers 32 respectively, and the transfer belt 46 is held at nip portions between the photoconductor drums 51 and the primary transfer rollers 32. It is noted that the drum unit 50 is described below.
The laser scanning device 13 is provided below the four image forming units 4. The laser scanning device 13 generates laser beams based on image data of respective colors input thereto, and irradiates the laser beams to the surfaces of the photoconductor drums 51 of the drum units 50. This allows electrostatic latent images to be formed on the surfaces of the photoconductive layers of the photoconductor drums 51.
The sheet feed cassette 24 is provided in a bottom portion (the lowest portion) of the housing 10A. Printing sheets of a predetermined size are stored in the sheet feed cassette 24. The sheet feed cassette 24 is supported in the housing 10A in a detachable manner. The sheet feed cassette 24 is attached to a predetermined attachment position in the housing 10A. A vertical conveyance path 26 is formed in a rear side inside the housing 10A, wherein the vertical conveyance path 26 extends from the sheet feed cassette 24 to the fixing device 16 via the secondary transfer roller 20. In addition, a sheet feed unit 24A is provided in proximity to a rear-end portion of the sheet feed cassette 24. In a state where the sheet feed cassette 24 is attached to the attachment position, the sheet feed unit 24A picks up, one by one, the printing sheets stacked on the sheet feed cassette 24, and feeds the printing sheet toward the vertical conveyance path 26.
The secondary transfer roller 20 is provided in the rear side inside the housing 10A at a position facing the driving pulley 5A. The toner image is transferred from the transfer belt 46 to the printing sheet by the secondary transfer roller 20.
The fixing device 16 is provided above the secondary transfer roller 20. The fixing device 16 fixes the toner image to the printing sheet by adding heat to the printing sheet. The fixing device 16 includes a pair of rollers: a heating roller 16A and a pressure roller 16B. In the fixing device 16, the printing sheet conveyed thereto from the secondary transfer roller 20 is conveyed while being nipped between the heating roller 16A and the pressure roller 16B. At this time, heat is transmitted from the heating roller 16A to the printing sheet, and the toner on the printing sheet is fused and fixed to the printing sheet. This allows a color image to be formed on the printing sheet.
As shown in
The following describes the photoconductor drum 51 and the configuration of the drum unit 50 that includes the photoconductor drum 51, with reference to
As described above, the image forming apparatus 10 includes the drum unit 50. The drum unit 50 rotatably supports the photoconductor drum 51, and as shown in
The charging roller 52 is configured to uniformly charge the surface of the photoconductor drum 51 to a certain potential, and is a roller-like rotator. The charging roller 52 is provided below the photoconductor drum 51. A support shaft is provided on each of opposite ends of the charging roller 52 in the longitudinal direction. The support shafts are rotatably supported by the frame 54. The cleaning portion 53 is configured to remove toner that has remained on the surface of the photoconductor drum 51, and includes, in an inside thereof, cleaning members such as a brush roller and a cleaning blade. The cleaning portion 53 is integrally attached to the frame 54.
The drum units 50 are disposed at predetermined attachment positions in the housing 10A. The drum units 50 are slidably supported by an inner frame or the like of the housing 10A such that they can be inserted and pulled out horizontally with respect to the housing 10A. In the present embodiment, the drum units 50 can be horizontally inserted along the left-right direction 9 from the right side of the housing 10A, and pulled out in a direction reverse to the insertion direction. When the drum units 50 are inserted into the innermost portion of the housing 10A and attached to the attachment positions, the image formation becomes available.
Here, as the image formation is repeatedly performed, the photoconductive layers on the surfaces of the photoconductor drums 51 of the drum units 50 are gradually deteriorated or worn. When the photoconductive layers are deteriorated, chargeability is reduced; and when the photoconductive layers are worn out, the surfaces of the photoconductor drums 51 are not charged to a certain potential, both resulting in reduction of image quality. As a result, the photoconductor drums 51 need to be replaced at a predetermined replacement timing. In the present embodiment, the photoconductor drums 51 are respectively provided in the drum units 50. As a result, when the photoconductor drums 51 are replaced, the drum units 50 need to be pulled out from the housing 10A. In addition, when maintenance is performed to the inside of the image forming apparatus 10, the drum units 50 need to be pulled out as necessary.
The frame 54 is a housing of the drum unit 50. The frame 54 is elongated in one direction. The frame 54 is detachably attached to the inner frame or the like of the housing 10A in a state where its longitudinal direction matches the left-right direction 9. The frame 54 supports opposite ends of the rotation shaft 62. The rotation shaft 62 supports the photoconductor drum 51 such that the photoconductor drum 51 can rotate around the rotation shaft 62. The frame 54 includes support portions 63 and 64 that are separated from each other in the left - right direction 9. The rotation shaft 62 is rotatably supported by the support portions 63 and 64. In addition, the frame 54 includes a side cover portion 61 that covers a rear-side part of the circumferential surface of the photoconductor drum 51. The side cover portion 61 extends along the left-right direction 9, connecting the support portion 63 and the support portion 64. The cleaning member is provided inside the side cover portion 61.
As shown in
A shaft hole 66 (see
The rotation shaft 62 passes through the support portion 63 and protrudes to the left side. On the other hand, an input gear 69 is provided on the inner frame of the housing 10A, wherein the input gear 69 is configured to receive a rotational driving force transmitted from a driving source such as a motor (not shown). When the drum unit 50 is attached to the housing 10A, a left end portion 62A of the rotation shaft 62 is inserted in a shaft hole formed at the center of the input gear 69. The rotational driving force is transmitted from the input gear 69 to the flange 65 via a joint 74 that is described below, and is further transmitted from the flange 65 to the photoconductor drum 51. Upon receiving the rotational driving force, the photoconductor drum 51 rotates around the rotation shaft 62 in a predetermined rotation direction.
As shown in
Specifically, the flange 65 includes a pressure input portion 65A, a gear portion 65B, and a shaft portion 65C, and these portions are integrally formed by a metal molding. The flange 65 is formed from a resin member.
The pressure input portion 65A is a cylindrical portion protruding from the right side surface of the gear portion 65B outward (rightward) in the axial direction.
The pressure input portion 65A is inserted and fitted in the inner hole of the photoconductor drum 51 by pressure. This allows the pressure input portion 65A to be fixed to the photoconductor drum 51. It is noted that the shaft hole 66 is formed at the central portion of the flange 65, more specifically at the central portion of the pressure input portion 65A. The rotation shaft 62 is inserted in the shaft hole 66.
The gear portion 65B is integrally formed on the outer circumferential surface of the flange 65. The outer diameter of the gear portion 65B is larger than the diameter size of the photoconductor drum 51. The gear portion 65B is coupled with a cleaning roller (not shown) for cleaning the charging roller 52 so that drive can be transmitted. During a rotation of the photoconductor drum 51, the rotational driving force is transmitted from the gear portion 65B to the input gear of the cleaning roller, and the cleaning roller for the charging roller 52 is rotated. To provide excellent transmission of the rotational driving force and reduce the driving sound and wear during the connection driving, lubricant such as silicone grease is applied to the gear portion 65B. It is noted that in the present embodiment, the gear portion 65B is a helical gear that has teeth inclined in the axial direction. Of course, the gear portion 65B may be a spur gear or a bevel gear.
The shaft portion 65C protrudes from the left side surface of the gear portion 65B outward (leftward) in the axial direction. In a state where the pressure input portion 65A of the flange 65 is fixed to the left end portion 51A of the photoconductor drum 51, the shaft portion 65C protrudes outward in the axial direction from the center of the left side surface of the gear portion 65B. The shaft portion 65C is smaller in diameter than the gear portion 65B and the pressure input portion 65A. The shaft portion 65C is formed in the shape of a cylinder whose inside is hollow. The inner diameter of the shaft portion 65C is larger than the outer diameter of the cylindrical portion 74A of the joint 74. As a result, the cylindrical portion 74A can be inserted in an inner hole of the shaft portion 65C. In the present embodiment, the cylindrical portion 74A is inserted in the inner hole of the shaft portion 65C, and the flange 65 and the joint 74 are engaged and coupled with each other in the circumferential direction. For example, an engaging rib (not shown) extending in the axial direction is provided on the outer circumferential surface of the cylindrical portion 74A, an engaging groove (not shown) extending in the axial direction is provided on the inner surface of the shaft portion 65C, and when the cylindrical portion 74A is inserted in the inner hole of the shaft portion 65C, the engaging rib is inserted in the engaging groove. This makes it possible for the shaft portion 65C and the cylindrical portion 74A to be coupled with each other in the circumferential direction, and move relative to each other in the axial direction.
The joint 74 is provided on the left side of the flange 65. The joint 74 receives the rotational driving force input to the input gear 69, and transmits the rotational driving force to the flange 65. As shown in
As shown in
A cylindrical protection cover 77 is provided to cover the cylindrical portion 74A of the joint 74 and the shaft portion 65C of the flange 65. The protection cover 77 is inserted in an opening 63A formed in the support portion 63 such that a part of the protection cover 77 is exposed to outside. An inclined surface 63B is formed on an upper end portion of the support portion 63 on the side of the insertion direction D1. The inclined surface 63B plays a role of a guide surface that, when the drum unit 50 is inserted in the housing 10A, abuts on an edge portion of the transfer belt 46 and guides the edge portion to rise upward.
Here, in the drum unit 50, in a case where the outer diameter (addendum circle diameter) of the gear portion 65B of the flange 65 is larger than the outer diameter of the photoconductor drum 51, when the drum unit 50 is pulled out of the housing 10A during replacement or maintenance, the gear portion 65B may be caught by an edge portion 46A of the transfer belt 46, and the edge portion 46A may be damaged. As a result, conventionally, a well-known retreating mechanism is provided in the image forming apparatus 10, such as a mechanism that, when the drum unit 50 is pulled out, lowers the drum unit 50 in a direction (downward) away from the transfer belt 46, or a mechanism that moves the transfer belt 46 upward before the drum unit 50 is pulled out. However, since, as described above, the transfer belt 46 is formed from a resin member and suspended between the driving pulley 5A and the driven pulley 5B with a predetermined tension, slack would be generated on the transfer belt 46. As a result, when the transfer belt 46 and the photoconductor drum 51 are relatively separated from each other by the retreating mechanism, the transfer belt 46 may be in a state of being in contact with the photoconductor drum 51. When the drum unit 50 is pulled out in such a state, the gear portion 65B would be caught by the edge portion 46A of the transfer belt 46 that is located on the side of the insertion direction D1. Even if the gear portion 65B is not caught by the edge portion 46A, if the gear portion 65B contacts the surface of the edge portion 46A during the pulling out, the lubricant applied to the gear portion 65B adheres to the surface of the transfer belt 46. This may reduce adhesion or transferability of the toner image on the surface of the transfer belt 46, and cause reduction in image quality.
In view of the above-described problem, in the drum unit 50 of the present embodiment, a guide member 80 is provided on the upper surface of the side cover portion 61 of the frame 54. Furthermore, a film member 90 (an example of the cover member of the present disclosure) is provided so as to cover the gear portion 65B of the flange 65. The provision of the guide member 80 and the film member 90 prevents the gear portion 65B of the flange 65 from contacting the transfer belt 46 when the drum unit 50 is pulled out.
The guide member 80 guides the edge portion 46A (see
In the present embodiment, the guide member 80 is provided on the upper surface of the side cover portion 61 near an end of the side cover portion 61 on the side of the insertion direction D1. The guide member 80 extends on both sides of an edge position P1 (see
As shown in
With the guide member 80 configured as described above being provided in the drum unit 50, when the drum unit 50 is pulled out from the attachment position in the housing 10A, first the guide member 80 abuts on the edge portion 46A of the transfer belt 46. Then, during the process of pulling out the drum unit 50, the edge portion 46A is guided from the first guide surface 81 to the inclined guide surface 83, and then to the second guide surface 82. This causes the edge portion 46A to rise to at least the upper-end position P3 of the gear portion 65B. As a result, the gear portion 65B does not contact the edge portion 46A when the drum unit 50 is pulled out of the housing 10A. This prevents the edge portion 46A from being damaged by contact.
It is noted that in the case where the guide member 80 is provided independently of the frame 54, the guide member 80 is not necessarily formed from the resin member as the frame 54 is, but may be formed from a material that is soft enough to absorb the impact of the contact with the edge portion 46A, and rigid enough to raise the edge portion 46A upward at the contact.
As shown in
The film member 90 is a film made of, for example, polyester. As shown in
As shown in
With the film member 90 configured as described above being provided, the gear portion 65B does not directly contact the lower surface of the transfer belt 46 when the drum unit 50 is pulled out. As a result, the lubricant applied to the gear portion 65B does not adhere to the lower surface of the transfer belt 46. This prevents reduction of adhesion or transferability of the toner image on the lower surface of the transfer belt 46.
In addition, with the configuration where the film member 90 protrudes in the insertion direction D1 from an end portion of the gear portion 65B on the side of the insertion direction D1, even if the lubricant moves in the insertion direction D1 from the gear portion 65B when the flange 65 is rotated, the lubricant is prevented from climbing over the film member 90 and moving to the transfer belt 46 located at a higher position. In particular, in a case where a helical gear is used as the gear portion 65B, and the helical gear is inclined toward the upstream in the rotation direction of the flange 65, the lubricant is apt to move in the insertion direction D1. According to the present embodiment, the film member 90 protrudes in the insertion direction D1 from an end portion of the gear portion 65B on the side of the insertion direction D1. This configuration effectively prevents the lubricant from adhering to the transfer belt 46.
It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.
Number | Date | Country | Kind |
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2015-241834 | Dec 2015 | JP | national |