Sheet conveying device and image forming apparatus

Abstract

To provide a sheet conveying device capable of suppressing vibration and deflection of a pair of conveying rollers and suppressing occurrence of wrinkles on a sheet to be conveyed.SOLUTION: A sheet conveying device 4 according to the present invention includes a first roller 43A, a second roller 43B, and a pressure applying unit 46. The pressure applying unit 46 has a pressure applying member 461 that contacts the first roller 43A from the opposite side to the second roller 43B, and a pressure applying member 462 that applies pressure to the pressure applying member 461 toward the second roller 43B. The first roller 43A has a step part 431 formed around the entire outer periphery of the first roller 43A, the outer diameter of which is smaller than the outer diameter of the contact area with the second roller 43B, and with which the pressure member 461 comes into contact.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Image forming devices such as copiers and printers include a sheet conveying device. The sheet conveying device includes a pair of conveying rollers that conveys sheets. The sheet conveying device conveys sheets one by one from a sheet supply unit that stores and stacks sheets, which are recording media used for printing (recording) images, toward an image forming unit (transfer unit), a fixing unit, and a sheet discharge unit.

[0003] For example, the conventional image forming apparatus disclosed in Patent Document 1 includes a pair of recording medium transport rollers consisting of a drive roller and a driven roller. The image forming apparatus also includes multiple rollers that press the driven roller against the drive roller. This prevents the long recording medium transport roller from wobbling or deflecting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-124081 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the conventional technology, there was a problem in that the pressure between the driven roller and the drive roller increased at the point where the roller was pressed, making it easy for wrinkles to form on the recording medium. Furthermore, there was a concern that pressing the roller for a long period of time could cause wear on the roller at the point where the pressure was higher than the surrounding area.

[0006] The present invention has been made in consideration of the above points, and aims to provide a sheet conveying device and an image forming device that can suppress vibration and deflection of the conveying roller pair and also suppress the occurrence of wrinkles in the sheet being conveyed. [Means for solving the problem]

[0007] In order to solve the above problems, the sheet conveying device of the present invention includes a first roller, a second roller, and a pressure unit. The first roller and the second roller are rotatably arranged opposite each other to form a conveying roller pair that conveys a sheet. At least one pressure unit is provided, and presses the first roller toward the second roller on the inside of both ends of the rotation axis of the conveying roller pair. The pressure unit has a pressure member that contacts the first roller from the opposite side of the second roller, and a pressure biasing member that biases the pressure member toward the second roller. The first roller is formed around the entire outer periphery of the first roller, has an outer diameter smaller than the outer diameter of the contact area with the second roller, and has a step with which the pressure member comes into contact. [Effects of the Invention]

[0008] According to the configuration of the present invention, the first roller does not contact the second roller at the step where the pressure member is pressed. This makes it possible to suppress an increase in pressure between the first roller and the second roller at the step where the pressure member is pressed. Therefore, in the sheet conveying device, it is possible to suppress vibration and deflection of the conveying roller pair and also suppress the occurrence of wrinkles in the sheet being conveyed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional front view of an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of a sheet conveying device of the image forming apparatus of FIG. [Figure 3] 3 is a perspective view of the vicinity of a pair of registration rollers of the sheet conveying device of FIG. 2. FIG. [Figure 4] 4 is a partial perspective view of the periphery of a support portion of the pair of registration rollers in FIG. 3. FIG. [Figure 5] 4 is a schematic top view of the axial center of the pair of registration rollers in FIG. 3. FIG. [Figure 6] 4 is a cross-sectional front view of the axial center of the pair of registration rollers in FIG. 3. FIG. [Figure 7] 4 is a cross-sectional perspective view of the axial center of the pair of registration rollers in FIG. 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following.

[0011] 1 is a schematic cross-sectional front view of an image forming apparatus 1 according to an embodiment. An example of the image forming apparatus 1 according to this embodiment is a tandem color printer that transfers a toner image onto a sheet S using an intermediate transfer belt 71. The image forming apparatus 1 may be a so-called multifunction peripheral that has functions such as printing, scanning (image reading), and facsimile transmission.

[0012] As shown in FIG. 1, the image forming apparatus 1 includes a sheet supply unit 3, a sheet conveying device 4, an exposure unit 5, an image forming unit 6, a transfer unit 7, a fixing unit 8, a sheet discharge unit 9, and a control unit 10, which are provided in an apparatus main body 2.

[0013] The sheet supply unit 3 is located at the bottom of the device main body 2. The sheet supply unit 3 stores multiple sheets S before printing, and separates and sends out the sheets S one by one during printing. The sheet conveying device 4 extends in the vertical direction along the side wall of the device main body 2. The sheet conveying device 4 conveys the sheet S sent out from the sheet supply unit 3 to the secondary transfer unit 73 and the fixing unit 8, and then discharges the sheet S after fixing from the sheet discharge port 4a to the sheet discharge unit 9. The exposure unit 5 is located above the sheet supply unit 3. The exposure unit 5 irradiates the image forming unit 6 with laser light controlled based on image data.

[0014] The image forming units 6 are disposed above the exposure unit 5 and below the intermediate transfer belt 71. The image forming units 6 include an image forming unit 6Y for yellow, an image forming unit 6C for cyan, an image forming unit 6M for magenta, and an image forming unit 6B for black. These four image forming units 6 have the same basic configuration. Therefore, in the following description, the identification symbols "Y," "C," "M," and "B" representing each color may be omitted unless otherwise specified.

[0015] The image forming unit 6 includes a photosensitive drum that is supported so as to be rotatable in a predetermined direction (clockwise in FIG. 1). The image forming unit 6 also includes a charging unit, a developing unit, and a drum cleaning unit that are arranged around the photosensitive drum along the direction of rotation of the photosensitive drum. A primary transfer unit 72 is arranged between the developing unit and the drum cleaning unit.

[0016] The photosensitive drum has a photosensitive layer formed on its outer circumferential surface. The charging unit charges the outer circumferential surface of the photosensitive drum to a predetermined surface potential. The exposure unit 5 exposes the outer circumferential surface of the photosensitive drum, which has been charged by the charging unit, to light, forming an electrostatic latent image of the original image on the outer circumferential surface of the photosensitive drum, with the charge attenuated. The development unit supplies toner to the electrostatic latent image on the outer circumferential surface of the photosensitive drum, developing it to form a toner image. Each of the four image forming units 6 forms a toner image of a different color. After the toner image is primarily transferred to the outer circumferential surface of the intermediate transfer belt 71, the drum cleaning unit removes and cleans any toner remaining on the outer circumferential surface of the photosensitive drum. In this way, the image forming unit 6 forms an image (toner image) that is later transferred to the sheet S.

[0017] The transfer unit 7 includes an intermediate transfer belt 71, primary transfer units 72Y, 72C, 72M, and 72B, a secondary transfer unit 73, and a belt cleaning unit 74. The intermediate transfer belt 71 is disposed above the four image forming units 6. The intermediate transfer belt 71 is supported so as to be rotatable in a predetermined direction (counterclockwise in FIG. 1), and is an endless intermediate transfer body onto which the toner images formed by each of the four image forming units 6 are sequentially superimposed and primarily transferred. The four image forming units 6 are disposed in a so-called tandem arrangement, lined up in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 71.

[0018] Primary transfer units 72Y, 72C, 72M, and 72B are disposed above image forming units 6Y, 6C, 6M, and 6B of the respective colors, with intermediate transfer belt 71 sandwiched therebetween. Secondary transfer unit 73 is disposed upstream of fixing unit 8 in the sheet conveying direction of sheet conveying device 4, and downstream of four image forming units 6Y, 6C, 6M, and 6B in the rotation direction of intermediate transfer belt 71. Belt cleaning unit 74 is disposed downstream of secondary transfer unit 73 in the rotation direction of intermediate transfer belt 71.

[0019] The primary transfer unit 72 transfers the toner image formed on the outer circumferential surface of the photosensitive drum onto the intermediate transfer belt 71. In other words, the toner image is primarily transferred onto the outer circumferential surface of the intermediate transfer belt 71 at the primary transfer units 72Y, 72C, 72M, and 72B for each color. Then, as the intermediate transfer belt 71 rotates, the toner images of the four image forming units 6 are successively superimposed and transferred onto the intermediate transfer belt 71 at a predetermined timing, thereby forming a color toner image on the outer circumferential surface of the intermediate transfer belt 71 in which toner images of four colors, yellow, cyan, magenta, and black, are superimposed.

[0020] The color toner image on the outer circumferential surface of the intermediate transfer belt 71 is transferred to the sheet S, which is fed synchronously by the sheet conveying device 4, at a secondary transfer nip formed in the secondary transfer unit 73. The belt cleaning unit 74 cleans the outer circumferential surface of the intermediate transfer belt 71 by removing toner and other adhering matter remaining on the outer circumferential surface of the intermediate transfer belt 71 after the secondary transfer. In this way, the transfer unit 7 transfers (records) the toner image formed on the outer circumferential surface of the photosensitive drum onto the sheet S.

[0021] The fixing unit 8 is disposed above the secondary transfer unit 73. The fixing unit 8 fixes the toner image to the sheet S by applying heat and pressure to the sheet S onto which the toner image has been transferred.

[0022] The sheet discharge section 9 is disposed above the transfer section 7. The sheet S on which the toner image has been fixed and printing has been completed is transported to the sheet discharge section 9. The sheet discharge section 9 takes out the printed sheet (printed material) from above.

[0023] The control unit 10 includes a CPU, an image processing unit, a memory unit, and other electronic circuits and electronic components (all not shown). The CPU controls the operation of each component provided in the image forming apparatus 1 based on control programs and data stored in the memory unit to perform processing related to the functions of the image forming apparatus 1. The sheet supply unit 3, the sheet conveying device 4, the exposure unit 5, the image forming unit 6, the transfer unit 7, and the fixing unit 8 each receive individual commands from the control unit 10 and work together to print on the sheet S. The memory unit is configured by a combination of a non-volatile storage device (not shown) such as a program ROM (Read Only Memory) or a data ROM, and a volatile storage device (not shown) such as a RAM (Random Access Memory).

[0024] Next, the configuration of the sheet conveying device 4 will be described using FIG. 2 in addition to FIG. 1. FIG. 2 is a perspective view of the sheet conveying device 4 of the image forming apparatus 1 of FIG. 1. Note that FIG. 2 does not depict components other than the main parts related to the detailed description. The sheet conveying device 4 includes a sheet conveying path 41, an opening / closing section 42, and a pair of registration rollers 43.

[0025] The sheet transport path 41 extends in a substantially vertical direction from the downstream side of the sheet supply unit 3 in the sheet transport direction, through the secondary transfer unit 73 and the fixing unit 8, to the upstream side of the sheet discharge unit 9 in the sheet transport direction. The sheet transport path 41 includes a plurality of pairs of transport rollers including a registration roller pair 43. The sheet transport path 41 transports the sheet S sent out from the sheet supply unit 3 to the secondary transfer unit 73 and the fixing unit 8 by the plurality of transport roller pairs, and further discharges the fixed sheet S from the sheet discharge port 4a to the sheet discharge unit 9.

[0026] The opening / closing unit 42 extends in the vertical direction along the side wall of the device body 2. The opening / closing unit 42 is supported by the device body 2 so as to be swingable around a rotation axis disposed at the lower end and extending in the front-to-rear direction of the device body 2 (the depth direction in the plane of FIG. 1 ), with its upper end portion as a free end. The opening / closing unit 42 can expose the sheet conveying path 41 including the periphery of the registration roller pair 43 by tilting its upper end portion to the side (to the right in FIG. 1 ) so as to move away from the device body 2. In other words, the opening / closing unit 42 is attached to the device body 2 so as to be able to open and close.

[0027] The pair of registration rollers 43 is disposed upstream of the secondary transfer unit 73 in the sheet conveying direction. The sheet S sent out from the sheet supply unit 3 passes through the sheet conveying path 41 and reaches the position of the pair of registration rollers 43. The control unit 10 corrects skew of the sheet S using the pair of registration rollers 43, and adjusts the conveyance timing of the sheet S with the toner image formation in the image forming unit 6 and the primary transfer in the transfer unit 7, and sends the sheet S toward the secondary transfer nip portion of the secondary transfer unit 73.

[0028] Next, the configuration around the pair of registration rollers 43 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a perspective view of the vicinity of the pair of registration rollers 43 of the sheet conveying device 4 in Fig. 2. Fig. 4 is a partial perspective view of the vicinity of a support portion of the pair of registration rollers 43 in Fig. 3. Note that Fig. 4 depicts an area near one end of the pair of registration rollers 43 in the axial direction.

[0029] The pair of registration rollers 43 is made up of a first roller 43A and a second roller 43B, which form a pair of transport rollers. The first roller 43A and the second roller 43B are disposed opposite each other. The first roller 43A is a drive roller that rotates when a driving force is input from a drive motor (not shown). The second roller 43B is a driven roller that comes into contact with the first roller 43A and rotates in accordance with the first roller 43A.

[0030] The first roller 43A is rotatably supported by the main body frame 2F of the apparatus main body 2. More specifically, a rotation shaft 43Ax of the first roller 43A is rotatably supported via a bearing (not shown) attached to the main body frame 2F. A bush member 44 and an opposing biasing member 45 are disposed at both axial ends of the pair of registration rollers 43.

[0031] The bushing members 44 are disposed at both axial ends of the pair of registration rollers 43. The bushing members 44 are formed in a generally rectangular parallelepiped shape extending in the opposing direction of the first roller 43A and the second roller 43B, and are supported by the main frame 2F so as to be movable in the radial direction of the first roller 43A. The bushing members 44 have a hole 44a and a bearing 44b.

[0032] The hole 44a is disposed at a location where the rotation shaft 43Ax of the first roller 43A is located, and penetrates the bushing member 44 in the axial direction of the rotation shaft 43Ax. The hole 44a is formed in a substantially cylindrical shape, and the rotation shaft 43Ax is inserted into the hole 44a. Within the range of movement of the bushing member 44 in the radial direction of the first roller 43A, the rotation shaft 43Ax does not come into contact with the inner periphery of the hole 44a.

[0033] The bearing 44b is disposed at a location where the rotation shaft 43Bx of the second roller 43B is located. The bearing 44b is fixed to the bushing member 44 and rotatably supports the rotation shaft 43Bx. In other words, the bushing member 44 rotatably supports the second roller 43B. That is, the second roller 43B is supported by the device body 2 via the bushing member 44. Furthermore, as the bushing member 44 moves in the radial direction of the first roller 43A, the second roller 43B moves in the radial direction of the first roller 43A.

[0034] The opposing biasing member 45 is disposed adjacent to the bushing member 44, on the opposite side of the first roller 43A from the second roller 43B. The opposing biasing member 45 is formed, for example, from a compression coil spring disposed so as to expand and contract in the radial direction of the first roller 43A. One end of the opposing biasing member 45 in the expansion and contraction direction is supported by the main frame 2F, and the other end is supported by the bushing member 44.

[0035] The opposing biasing member 45 biases the bushing member 44, which is movable in the radial direction of the first roller 43A, relative to the main body frame 2F. Specifically, the opposing biasing member 45 biases the bushing member 44 in a direction in which the second roller 43B approaches the first roller 43A, i.e., in the leftward direction in FIG. 4.

[0036] According to the above-mentioned support mechanism for the first roller 43A and the second roller 43B, both the first roller 43A and the second roller 43B of the resist roller pair 43 are supported by the device main body 2, thereby achieving high precision positioning and stabilization of the pressure state.

[0037] Next, a more detailed configuration of the vicinity of the pair of registration rollers 43 will be described with reference to Fig. 5 to Fig. 7 in addition to Fig. 3. Fig. 5, Fig. 6 and Fig. 7 are a schematic top view, a sectional front view and a sectional perspective view of the central part in the axial direction of the vicinity of the pair of registration rollers 43 in Fig. 3. The sheet conveying device 4 further includes a pressure unit 46.

[0038] The pressure applying unit 46 is disposed inside both axial end portions of the pair of registration rollers 43. More specifically, in this embodiment, the pressure applying unit 46 is disposed at one location in the center of the pair of registration rollers 43 in the axial direction. At least one pressure applying unit 46 needs to be disposed, and multiple pressure applying units 46 may also be disposed. The pressure applying unit 46 has a pressure applying member 461 and a pressure applying member 462. The first roller 43A also has a step portion 431 disposed opposite the pressure applying unit 46.

[0039] The pressure member 461 is disposed on the opposite side of the second roller 43B across the first roller 43A. The pressure member 461 contacts the first roller 43A from the opposite side of the second roller 43B. The tip portion of the pressure member 461 that faces the first roller 43A is formed in a rectangular parallelepiped shape. The tip surface of the pressure member 461 that contacts the first roller 43A is formed as a curved surface that follows the circumferential surface of the stepped portion 431 of the first roller 43A.

[0040] The pressure biasing member 462 is disposed adjacent to the pressure member 461, on the opposite side of the first roller 43A from the second roller 43B. The pressure biasing member 462 is formed, for example, by a compression coil spring disposed so as to expand and contract in the radial direction of the first roller 43A. One end of the pressure biasing member 462 in the expansion and contraction direction is supported by the main frame 2F, and the other end is supported by the pressure member 461.

[0041] The pressure biasing member 462 biases the pressure member 461, which is movable in the radial direction of the first roller 43A, relative to the main body frame 2F. That is, the pressure biasing member 462 biases the pressure member 461 toward the second roller 43B. More specifically, the pressure biasing member 462 biases the pressure member 461 in a direction in which the first roller 43A approaches the second roller 43B, that is, to the right in FIG. 6.

[0042] The step portion 431 is disposed opposite the pressure member 461 and comes into contact with the pressure member 461. The outer diameter D1 of the step portion 431 is smaller than the outer diameter D2 of the contact area of ​​the first roller 43A with the second roller 43B. The step portion 431 is formed around the entire outer periphery of the first roller 43A. The step portion 431 is formed in a cylindrical shape whose central axis coincides with the contact area of ​​the first roller 43A with the second roller 43B.

[0043] Additionally, the length L1 of the step portion 431 in the axial direction is longer than the length L2 of the pressure member 461 in the axial direction. The pressure member 461 comes into contact with the first roller 43A in an area inside the step portion 431 in the axial direction.

[0044] According to the above configuration, the first roller 43A does not contact the second roller 43B at the stepped portion 431 where the pressure member 461 is pressed. This makes it possible to suppress an increase in pressure between the first roller 43A and the second roller 43B at the portion where the pressure member 461 is pressed. Therefore, in the sheet conveying device 4, it is possible to suppress vibration and bending of the registration roller pair 43 and also suppress the occurrence of wrinkles in the sheet S being conveyed.

[0045] Furthermore, since the pressure unit 46 is disposed in one location in the axial center of the pair of registration rollers 43, it is possible to increase the pressure between the first roller 43A and the second roller 43B uniformly across both regions on one side and the other side of the axial direction of the pair of registration rollers 43. This makes it possible to enhance the effect of suppressing vibration and deflection of the pair of registration rollers 43.

[0046] More specifically, the pressure applying unit 46 biases the pressure applying member 461 toward the upstream side in the sheet conveying direction with respect to the central axis 43By of the second roller 43B, i.e., toward the lower side of the central axis 43By in Fig. 6, using the pressure applying member 462. In other words, the pressure applying unit 46 biases the pressure applying member 461 toward the upstream side in the sheet conveying direction with respect to the nip portion N of the registration roller pair 43, i.e., toward the lower side of the nip portion N in Fig. 6.

[0047] According to the above configuration, the biasing force of the pressure biasing member 462 acts on the upstream side of the rotation direction of the first roller 43A, which is the drive roller, with respect to the nip portion N. This increases the gripping force on the sheet S entering the nip portion N, and increases the conveying force of the sheet S by the first roller 43A. Therefore, it is possible to improve the conveying performance of the sheet S by the registration roller pair 43.

[0048] As described above, by biasing pressure member 461 toward the upstream side in the sheet conveying direction relative to central axis 43By of second roller 43B, which is a driven roller, second roller 43B may be more likely to move downstream in the sheet conveying direction. However, the movement of second roller 43B downstream in the sheet conveying direction can be prevented by the support mechanisms at both axial end portions of first roller 43A and second roller 43B.

[0049] Furthermore, according to the above configuration, the pressure unit 46 is provided so as to face the first roller 43A, which is a drive roller, relative to the second roller 43B, which is a driven roller. This makes it possible to improve the conveyance performance of the sheet S by the registration roller pair 43 while suppressing vibration and deflection of the first roller 43A and the second roller 43B and the occurrence of wrinkles in the sheet S being conveyed.

[0050] According to the above configuration, the pressure unit 46 is provided for the registration roller pair 43. With regard to the registration roller pair 43, vibration and deflection of the roller pair and the occurrence of wrinkles in the conveyed sheet S are suppressed, and further, it is possible to improve the performance in correcting skew of the sheet S and adjusting the conveyance timing of the sheet S.

[0051] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0052] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing that forms images of multiple colors by sequentially overlapping them, but the image forming apparatus is not limited to this type. The image forming apparatus may be a non-tandem type image forming apparatus for color printing or a monochrome image forming apparatus. [Industrial Applicability]

[0053] The present invention can be used in a sheet transport device and an image forming apparatus. [Explanation of symbols]

[0054] 1. Image forming device 2. Device body 2F Main frame 3 Sheet supply unit 4 Sheet transport device 41 Sheet transport path 43 Registration roller pair (transport roller pair) 43A First Roller 43Ax Rotating shaft 43B 2nd roller 43Bx Rotating Axis 43By center axis line 44 Bush member 45 opposing biasing member 46 Pressure section 431 Step 461 Pressure Member 462 Pressure biasing member N Nip section S seat

Claims

1. a first roller and a second roller that constitute a conveying roller pair that are rotatably arranged opposite to each other and convey a sheet; at least one pressure unit that presses the first roller toward the second roller on the inner side of both end portions of the conveying roller pair in the axial direction; Equipped with The pressure applying unit is a pressure member that contacts the first roller from the opposite side of the second roller; a pressure biasing member that biases the pressure member toward the second roller; and The first roller has a stepped portion formed around the entire outer periphery of the first roller, an outer diameter smaller than the outer diameter of the contact area with the second roller, and with which the pressure member comes into contact.

2. The sheet conveying device according to claim 1 , wherein the pressure unit is disposed at a center in the axial direction of the pair of conveying rollers.

3. 2. The sheet transport device according to claim 1, wherein the pressure applying unit applies pressure to the pressure applying member toward an upstream side in the sheet transport direction with respect to a central axis of the second roller.

4. The first roller is a driving roller that rotates when a driving force is input thereto, The second roller is a driven roller that rotates in accordance with the first roller by coming into contact with the first roller.

2. The sheet transport device according to claim 1.

5. the first roller is rotatably supported by a main body frame of the device main body; a bushing member supported by the main body frame so as to be movable in a radial direction of the first roller and which rotatably supports the second roller; an opposing biasing member that biases the bushing member in a direction in which the second roller approaches the first roller; The sheet conveying device according to claim 1 , further comprising:

6. An image forming apparatus comprising the sheet conveying device according to any one of claims 1 to 5.

7. 7. The image forming apparatus according to claim 6, wherein the pair of transport rollers is a pair of registration rollers that corrects skew of the sheet and also performs the above.

Images