Transfer device and image forming apparatus

Abstract

To provide a transfer device that prevents variations in transfer pressure, avoids the interference between a transfer member and positioning members during opening and closing of a cover member, and can reduce its installation space and cost.SOLUTION: A transfer device body provided on an openable and closable cover member of an image forming apparatus body comprises a transfer member 8 and a pressure part 24 applying pressure to the transfer member 8, and the pressure part 24 has a holding member 28 and an urging member 30. When the cover member is closed, the transfer member 8 is brought into contact with and positioned by positioning members 26, 27 of the image forming apparatus body and the holding member 28 is displaced, and when the cover member is opened, a movement route C on which the transfer member 8 moves when separated from the positioning members 26, 27 takes a route not interfering with the positioning members 26, 27. The holding member 28 is fitted onto a support shaft 31 with a gap therebetween and is rotatably supported thereon. The support shaft 31 has a coaxial curved surface part 28d on its outer surface, and the transfer device body has a pressure receiving part 32a having the same curvature as the curved surface part 28d and in contact with the curved surface part 28d.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a transfer device and an image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus, a transfer nip formed by an image carrier and a transfer member such as a transfer roller is arranged vertically, and a transfer sheet, which is a recording medium, is transported vertically. In this configuration, a transfer device is known in which the position of the transfer nip is shifted upstream in the sheet transport direction from a normal position where the center lines of the image carrier and the transfer member are perpendicular to the sheet transport path, thereby improving the separability of the transfer sheet and the image carrier. In such a transfer device, the transfer member is arranged such that its center line and the center line of the image carrier are inclined at a predetermined angle (about 10 to 30 degrees) downward in the vertical direction from the normal position perpendicular to the above-mentioned sheet transport path.

[0003] In the image forming apparatus including the above-mentioned transfer device, since it is necessary to open and close the sheet transport path in the event of a transport jam of the transfer sheet, an image forming apparatus including the above-mentioned transfer device is known that is provided with a cover member having a pivot point at the lower part of the image forming apparatus main body, and configured to open and close the sheet transport path. The transfer device is configured so that the transfer member separates from the image carrier when the sheet transport path is opened. In such a transfer device in which the transfer member can be brought into contact with and separated from the image carrier, the transfer member is provided displaceably relative to the image carrier so that the transfer member contacts the image carrier at an appropriate position and with an appropriate pressure.

[0004] In an image forming apparatus in which a cover member is provided so as to be openable and closable relative to the image forming apparatus main body and a transfer member is provided so as to be displaceable relative to an image carrier, after the cover member is released from the image forming apparatus main body to open the sheet transport path, the displaceable transfer member may interfere with a member provided on the transfer device main body when the cover member is closed. When such interference occurs, problems occur in which the components of the apparatus come into contact with each other, causing malfunctions or misalignment.

[0005] In order to solve the above-mentioned problems, Patent Document 1 discloses an image forming apparatus in which an opening / closing means (23) can swing around a fulcrum (24), a bearing means (130) is positioned by a positioning means (49), and a pressing means (140) is supported by the opening / closing means (23) so as to be swingable around a fulcrum (143) at the base end side of an arm means (142) extending in the pressing direction. The arm means (142) is biased by a retaining biasing means (190) in a direction intersecting the pressing direction so that the arm means (142) is held in an initial position in which it has swung a predetermined angle in a direction away from the opening / closing means (23), and the bearing means (130) is engaged with the positioning means (49) in a non-interfering positional relationship when the opening / closing means (23) is closed. This is believed to effectively prevent interference between the bearing means (130) mounted on the opening / closing means (23) and the positioning means (49) when the opening / closing means (23) is closed.

[0006] In addition, in an image forming device in which a cover member is provided on the image forming device body so as to be able to be opened and closed in order to open the sheet transport path, and a transfer member is provided so as to be able to be displaced relative to an image carrier, a large force must be applied when closing the cover member, posing a problem of poor operability. In this configuration, particularly in the configuration in which the engaging member of the cover member is engaged with the engaged member of the image forming apparatus main body, when the direction of force acting between the engaging member and the engaged member is linear, the transfer member is directly subjected to the reaction force of the biasing member that displaces the transfer member, and therefore it is unavoidable that the operating force becomes large.

[0007] In order to solve this problem, Patent Document 2 discloses a transfer unit (60) having a transfer unit main body (91) that is rotatable relative to the image forming device main body (55), a transfer member (5) that contacts the image carrier (11) to form a transfer nip, and a pressure means (93) that presses the transfer member (5) against the image carrier (11). A lever member (66) that engages with a positioning portion (74) of the image forming device (55) is rotatably provided on the transfer unit main body (91), and an opening / closing body (15) that is provided on the image forming device main body (55) and can be opened and closed contacts the lever member (66). The transfer unit (60) can be positioned relative to the image forming device main body (55) by the rotation of the lever member (66) linked to the closing operation of the opening / closing body (15). This allows the setting force required to position the transfer unit relative to the image forming device body to be significantly reduced, contributing to improved operability and ultimately usability.Furthermore, the reduction in setting force also makes it possible to make the opening and closing body of the duplex unit lighter and smaller, thereby achieving cost reduction. Summary of the Invention [Problem to be solved by the invention]

[0008] In conventional technology, the transfer member is pressurized by a pressure section composed of a movable member and a urging member, and the transfer member is configured to be able to slide on the movable member, or the pressure section, composed of a holding member and a urging member and which presses the transfer member with the urging member, is configured to be able to swing, thereby avoiding interference between the transfer member and the positioning member when the cover member is opened and closed. However, when the accuracy of each part differs or the position of the transfer device fluctuates, the movable member does not displace sufficiently due to the influence of friction, etc., and the fluctuation is transmitted to the transfer member as it is, and a force greater than the pressing force of the urging member is applied, or the fluctuation of the movable member becomes large, and the pressing force becomes weaker than expected, resulting in an excessive fluctuation in the transfer pressure. Also, in a configuration in which the transfer member is pressed by the urging member and the pressing unit swings on the rotation fulcrum, in order to obtain a pressing force equivalent to that of the method using the movable member, it is necessary to make the force of the urging member stronger than that of the movable member method and to make the part that receives the pressing force stronger. Therefore, in order to simultaneously pressurize the transfer member and avoid interference with the positioning member, the pressing unit becomes large. The present invention aims to solve the above-mentioned problems, suppress excessive fluctuations in transfer pressure, avoid interference between the transfer member and the positioning member when the cover member is opened and closed, and provide a transfer device that is space-saving, low-cost, and can be installed in small devices. [Means for solving the problem]

[0009] The invention described in claim 1 includes a transfer device main body provided on a cover member that can be opened and closed relative to an image forming device main body, a transfer member provided on the transfer device main body and arranged to face an image carrier provided on the image forming device main body, and a pressure unit provided on the transfer device main body and presses the transfer member toward the image carrier, the pressure unit having a holding member that holds the transfer member rotatably and displaceably in a direction toward and away from the image carrier and displaceably supported on the transfer device main body, and a biasing member that biases the transfer member in a direction to contact the image carrier, and when the cover member is closed, the image forming device main body is The transfer member comes into contact with a positioning member provided and is positioned, and the holding member is displaced, and when the cover member is opened and the transfer member moves away from the positioning member, the movement path of the transfer member, which moves in conjunction with the displacement of the holding member and the opening of the cover member, takes a path that does not interfere with the positioning member, the holding member is fitted with a gap onto a support shaft provided in the transfer device main body and supported so as to be freely rotatable, and has a curved portion coaxial with the support shaft on its outer surface on the support shaft side, and the transfer device main body has a pressure receiving portion having the same curvature as the curved portion and in contact with the curved portion. Effect of the Invention

[0010] According to the present invention, it is possible to provide a transfer device which can achieve space saving and can be installed in a low-cost, small-sized image forming apparatus. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic front view of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing a transfer device during image formation according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram illustrating a transfer member and a pressure unit according to an embodiment of the present invention. [Figure 4] 5A and 5B are schematic diagrams illustrating a state of a transfer device during image formation and a state of the transfer device when a double-sided cover is open according to an embodiment of the present invention. [Diagram 5] 1 is a schematic diagram showing a transfer device when a double-sided cover is open according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Fig. 1 shows an image forming apparatus according to one embodiment of the present invention. In the figure, printer 1, which is a monochrome image forming apparatus, is provided with a removable process cartridge 2 containing black toner, located approximately in the center of a housing 3 serving as the main body of the image forming apparatus. Inside the process cartridge 2, a photosensitive drum 4 serving as an image carrier, a developing device 5, a cleaning device 6, a charging device, a static eliminator, etc. are each provided in a replaceable manner. Inside the housing 3, there are arranged an exposure device 7, a transfer device 9 having a transfer roller 8 as a transfer member, a paper feed tray 10 containing transfer sheets S as a recording medium, a fixing device 11, and the like.

[0013] During normal image formation, in which an image is formed on one side of the transfer sheet S, an electrostatic latent image is formed on the photosensitive drum 4 by the operation of the exposure device 7, and the electrostatic latent image formed by the toner supplied from the development device 5 is visualized to become a toner image. Thereafter, one transfer sheet S stored in the paper feed tray 10 is fed by the operation of the paper feed roller 12, and the fed transfer sheet S is temporarily stopped by the registration roller pair 13. Then, the registration roller pair 13 operates so that the image forming area of ​​the transfer sheet S coincides with the toner image at the nip position between the photosensitive drum 4 and the transfer roller 8, and the photosensitive drum 4 and the transfer roller 8 come into contact with each other with the transfer sheet S interposed therebetween, and a transfer bias is applied, so that the toner image is transferred to the transfer sheet S.

[0014] Since the transfer sheet S that has passed through the transfer nip is charged by the application of a transfer bias, it is separated from the photosensitive drum 4 or transfer roller 8 by removing the charge with a charge removing needle 14, and is sent to the fixing device 11. The toner image transferred onto the transfer sheet S sent to the fixing device 11 is fused by heat and pressure, and after the image is fixed, the transfer sheet S is sent to a pair of paper discharge rollers 15 and discharged onto a paper discharge tray 16.

[0015] During double-sided image formation, in which images are formed on both sides of the transfer sheet S, the separation claw 17 is switched and then the reversing roller 18 is rotated in the opposite direction to send the transfer sheet S, with the image fixed on the first side, into a reversing path 19, and after the separation claw 17 is returned, the reversing roller 18 is rotated forward to send the transfer sheet S into a double-sided path 20. The transfer sheet S sent into the double-sided path 20 is transported again upside down by a roller pair provided in the path to the registration roller pair 13, and thereafter, an image is formed on the second side in the same process as during normal image formation.

[0016] The printer 1 is provided with a double-sided cover 21 as a cover member to open the transport path of the transfer sheet S in the event of a sheet transport jam. The double-sided cover 21 is rotatably supported on a fulcrum 22 relative to the housing 3, and is configured so that the upper end portion can be opened in the direction of the arrow A in Fig. 1. When the double-sided cover 21 is opened, the sheet transport path located downstream of the paper feed roller 12 in the sheet transport direction is opened. In this embodiment, the transfer device 8 is fixed to the double-sided cover 21 .

[0017] 2 is a schematic diagram of a transfer device 9, which is a characteristic feature of the present invention. In the figure, the transfer device 9 has a transfer frame 23 as a transfer device main body, a transfer roller 8, and a pressure unit 24. The transfer frame 23 is fixed to the double-sided cover 21 by a method such as screwing. The transfer roller 8 is disposed opposite the photosensitive drum 4, and is held by a pressure unit 24 so as to be rotatable and displaceable in a direction toward and away from the photosensitive drum 4. The pressure unit 24, which presses the transfer roller 8 against the photosensitive drum 4, holds the transfer roller 8 in a manner offset upstream of the photosensitive drum 4 in the sheet conveying direction.

[0018] 3 is a schematic diagram for explaining the transfer roller 8 and the pressure unit 24. In the figure, a stepped bearing 25 is fitted to the shaft 8a of the transfer roller 8, and a small diameter portion 25a of the bearing 25 is formed so as to be able to fit into positioning members 26, 27 which are immovable members fixed to the housing 3. The positioning members 26, 27 restrict the transfer roller 8 from moving in a direction perpendicular to a line segment B connecting the center of the photosensitive drum 4 and the center of the transfer roller 8, and perform positioning of the photosensitive drum 4 and the transfer roller 8 during the image forming operation. The end of the positioning member 26 opposite to the photosensitive drum 4 is shaped to open outward, and is formed in a shape that easily guides the small diameter portion 25a.

[0019] The bearing 25 is disposed inside a spring case 28 serving as a retaining member, and a slider 29 and a pressure spring 30 serving as a biasing member are further provided inside the spring case 28. One end of the spring case 28 on the photosensitive drum 4 side is formed with a U-shaped receiving portion 28a, and the large diameter portion 25b of the bearing 25 is fitted into the receiving portion 28a. One end of slider 29, which is slidably supported by spring case 28, abuts against large diameter portion 25b, and the other end is formed with a stopper 29a. Stopper 29a abuts against step portion 28b formed on spring case 28, thereby restricting the amount of movement of slider 29 within spring case 28. One end of a pressure spring 30 abuts against the end of the slider 29 on the stopper 29a side. The other end of the pressure spring 30 abuts against the inside of the spring case 28, and the pressure spring 30 presses the transfer roller 8 toward the photosensitive drum 4 via the slider 29 and the bearing 25.

[0020] The other end of the spring case 28 is provided with a hole 28c which serves as a pivot point for the spring case 28, and a support shaft 31 provided in the transfer frame 23 is fitted into the hole 28c with a certain gap. The outer peripheral surface on the other end side of the spring case 28 is formed in an arc shape coaxial with the hole 28c, and forms a curved surface portion 28d. On the transfer frame 23 side corresponding to the curved surface portion 28d, a receiving member 32 is provided which has a pressure receiving portion 32a formed in a concave shape with the same curvature as the curved surface portion 28d against which the curved surface portion 28d can come into comfortable contact.

[0021] Fig. 4 is a schematic diagram showing the state of the transfer device 9 during image formation and the state of the transfer device 9 when the double-sided cover 21 is open. During image formation, the transfer device 9 is in the solid line position in Fig. 4, i.e., the state shown in Fig. 2, and when the double-sided cover 21 is opened for sheet jam removal or the like, it is in the state shown in the two-dot chain line position in Fig. 4. The state shown in the two-dot chain line position in Fig. 4 is shown in Fig. 5. When double-sided cover 21 is opened in the direction of arrow A from the state shown in Fig. 1, support shaft 31 is displaced from the solid line position (Fig. 2) to the two-dot chain line position (Fig. 5) in Fig. 4. At this time, pressure spring 30 in pressure section 24 expands, and transfer roller 8 moves in the receiving section 28a in the direction toward photosensitive drum 4 until stopper 29a abuts against step portion 28b. After stopper 29a abuts against step portion 28b and the movement of slider 29 is restricted, transfer roller 8 moves away from photosensitive drum 4.

[0022] After the separation, the transfer roller 8 moves linearly along the positioning members 26, 27 from the solid line position (FIG. 2) in FIG. 4 to the two-dot chain line position (FIG. 5), while the pressure unit 24 rotates about the support shaft 31. Then, when the transfer roller 8 moves to the two-dot chain line position (FIG. 5) in FIG. 4, the movement path C of the small diameter portion 25a shown in FIG. 5, which is the movement path of the transfer member accompanying the opening of the double-sided cover 21, no longer interferes with the positioning member 26, so that the double-sided cover 21 can be opened without the bearing 25 colliding with the positioning members 26, 27, and the sheet transport path can be opened.

[0023] In the above-mentioned configuration, when the transfer roller 8 is pressed against the photosensitive drum 4 by the urging force of the pressure spring 30, the curved surface portion 28d comes into contact with the pressure receiving portion 32a, and the pressure receiving portion 32a receives the pressure force from the pressure unit 24. When the curved surface portion 28d comes into contact with the pressure receiving portion 32a, a certain gap is provided between the support shaft 31 and the hole portion 28c, and the support shaft 31 and the hole portion 28c are in a non-contact state (a state in which almost no pressure force acts even if they are in contact).

[0024] Generally, in a transfer device that directly pressurizes a transfer member with the biasing force of a biasing member, a suitable strength is required so that the part receiving the pressure force is not damaged. In the transfer device 9 of the present invention, the pressure force acting on the transfer roller 8 is received by the pressure receiving part 32a of the receiving member 32 that is a part of the transfer frame 23, so that the pressure force does not act on the support shaft 31. Therefore, it is not necessary to configure the support shaft 31 to be strong enough to support the pressure force, and the support shaft 31 can be made thin even if it has a shaft shape that is in the same range as the transfer frame 23, which achieves space saving and provides a transfer device that can be installed in a small image forming device at low cost.

[0025] Furthermore, when the double-sided cover 21 is opened, the spring case 28 is displaced due to the pressure from the pressure section 24 as the double-sided cover 21 is displaced. However, as described above, the support shaft 31 and the hole section 28c are fitted together with a gap, and since no load acts on the pressure receiving section 32a when the pressure is released, the pressure section 24 can oscillate smoothly, i.e., the double-sided cover 21 can oscillate smoothly. This makes it possible to directly pressurize the transfer member with the urging member while simultaneously opening and closing the cover member including the transfer device without interference, in a space-saving configuration.

[0026] In addition, in an embodiment of the present invention, as shown in FIG. 3, the pressure receiving portion 32a is provided within a range including a line segment B, which is an extension line along the pressure direction of the transfer roller 8 against the photosensitive drum 4, i.e., on the extension line of the line segment B. With this configuration, the pressure acting on the transfer roller 8 can be reliably received by the pressure receiving portion 32a of the receiving member 32, and space saving can be reliably achieved.

[0027] In the above embodiment and modified example, an example was shown in which a monochrome printer 1 was used as an image forming apparatus to which the present invention can be applied, but the image forming apparatus to which the present invention can be applied is not limited to this, and the present invention can also be applied to full-color printers, copying machines, facsimiles, multi-function machines, etc. Also, while the photosensitive drum 4 was exemplified as an image carrier, the image carrier is not limited to this, and may be, for example, an intermediate transfer belt that carries an intermediate transfer image. In the above embodiment, a configuration is shown in which a transfer sheet S is used as the recording medium on which an image is formed, but this transfer sheet S is not limited to recording paper, but also includes cardboard, postcards, roll paper, envelopes, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, OHP film, resin films, etc., and any sheet-like material on which an image can be formed may be used.

[0028] For example, aspects of the present invention are as follows. [1] A transfer device body provided on a cover member that can be opened and closed relative to an image forming device body, a transfer member provided on the transfer device body and arranged to face an image carrier provided on the image forming device body, and a pressure unit provided on the transfer device body and presses the transfer member toward the image carrier, the pressure unit having a holding member that holds the transfer member rotatably and displaceably in a direction toward and away from the image carrier and displaceably supported on the transfer device body, and a biasing member that biases the transfer member in a direction to contact the image carrier, and when the cover member is closed, the transfer device body provided on the image forming device body the transfer member comes into contact with and is positioned on a positioning member fitted in the transfer device body, and the holding member is displaced; when the cover member is opened and the transfer member moves away from the positioning member, the movement path of the transfer member, which moves in conjunction with the displacement of the holding member and the opening of the cover member, takes a path that does not interfere with the positioning member; the holding member is fitted with a gap onto a support shaft provided in the transfer device body and supported so as to be freely rotatable; and the outer surface of the support shaft side has a curved portion coaxial with the support shaft, and the transfer device body has a pressure receiving portion having the same curvature as the curved portion and in contact with the curved portion. [2] The transfer device according to [1], wherein the pressure receiving portion is provided within a range including an extension line along a pressure direction of the transfer member against the image carrier. [3] An image forming apparatus comprising the transfer device according to [1] or [2].

[0029] Although a preferred embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the spirit of the present invention described in the claims, unless otherwise specifically limited in the above description. The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention. [Explanation of symbols]

[0030] 1. Image forming device (printer) 3 Image forming device main body (housing) 4 Image carrier (photoconductor drum) 8 Transfer member (transfer roller) 21 Cover material (double-sided cover) 23 Transfer device body (transfer frame) 24 Pressurizing section 26,27 Positioning member 28 Retaining member (spring case) 28d curved part 30 Pressurizing member (pressure spring) 31 Spindle 32a Pressure receiving part C. Transfer member movement path (movement trajectory of small diameter part) [Prior art documents] [Patent documents]

[0031] [Patent Document 1] JP 2020-52109 A [Patent Document 2] Patent No. 5157688

Claims

1. a transfer device body provided on a cover member that is openable and closable relative to the image forming device body; a transfer member provided in the transfer device main body and arranged to face an image carrier provided in the image forming device main body; a pressure unit that is provided in the transfer device main body and presses the transfer member toward the image carrier, the pressure unit holds the transfer member rotatably and displaceably in a direction toward and away from the image carrier, and includes a holding member supported displaceably on the transfer device body, and a biasing member biasing the transfer member in a direction toward and away from the image carrier; When the cover member is closed, the transfer member comes into contact with a positioning member provided in the image forming apparatus body, and is positioned, and the holding member is displaced. when the cover member is opened and the transfer member is separated from the positioning member, a moving path of the transfer member which moves in association with the displacement of the holding member and the opening of the cover member takes a path that does not interfere with the positioning member, the holding member is rotatably supported by being fitted with a gap to a support shaft provided on the transfer device body, and has an outer surface on the support shaft side, which has a curved surface portion coaxial with the support shaft, The transfer device main body has a pressure receiving portion that has the same curvature as the curved surface portion and is in contact with the curved surface portion.

2. 2. The transfer device according to claim 1, The transfer device according to claim 1, wherein the pressure receiving portion is provided within a range including an extension line along a pressure direction of the transfer member against the image carrier.

3. 3. An image forming apparatus comprising the transfer device according to claim 1.

Images