Belt unit and image forming apparatus

Abstract

To prevent a belt-like member from overriding a stretching member.SOLUTION: A belt unit 20 comprises: a belt-like member 21 that is capable of circulation movement; a stretch member 23 that is capable of axial rotation and stretches the belt-like member 21; and a rotary member 71 that is provided rotatable relative to the stretch member 23 on an axis, stretches the belt-like member 21, and has a receiving part 71b receiving, from an axial direction H, the belt-like member 21 moving in the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a belt unit and an image forming apparatus. [Background Art]

[0002] For example, Patent Document 1 discloses a belt unit including an endless conveying belt, a driving roller around which the conveying belt is stretched and to which a driving force is supplied to drive the conveying belt, and a driven roller that stretches the conveying belt. The driven roller is configured by being divided into three parts in the axial direction, and includes rollers that rotate independently of each other, and flanges that rotate integrally with the rollers disposed at both axial ends and against which edges of the conveying belt abut. The belt unit further includes friction plates disposed on both sides of the driven roller that apply a frictional force to the flange when the flange, which moves in the axial direction due to the abutment of the edge of the conveying belt, abuts against the friction plate. In addition, Patent Document 2 discloses a structure in which a tension roller is divided into a plurality of divided rollers in the axial direction, and each divided roller is configured to be rotatable independently. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2009-265421 [Patent Document 2] Japanese Unexamined Patent Publication No. 2012-63655 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Here, when the belt-shaped member stretched around a stretching member circulates, if the amount of movement of the belt-shaped member in the width direction becomes large, the belt-shaped member may ride onto a portion of the stretching member that does not contact the belt-shaped member during circulating movement, resulting in damage to the belt-shaped member. An object of the present invention is to suppress the riding of a belt-shaped member onto a stretching member. [Means for Solving the Problem]

[0005] The invention described in claim 1 comprises: a strip-shaped member configured to be capable of circulating movement; a tensioning member that is rotatable on an axis and stretches the strip-shaped member; and a rotating member provided on the axis so as to be rotatable relative to the tensioning member, which stretches the strip-shaped member and has a receiving portion that receives the strip-shaped member from the axial direction as it moves in the axial direction. The rotating member is provided at a position on the tensioning member side relative to the receiving portion of the rotating member and has a shape that becomes narrower as it approaches the receiving portion. It is a belt unit. 。 Claim 2 The invention described herein is characterized in that the shaped portion is tapered. 1 This is the belt unit described in [the document]. Claim 3 The invention described above is a belt unit according to claim 1, characterized in that when the strip-shaped member is received by the receiving portion from the axial direction, the rotating member is decelerated by the axial pressing action with other members, and a speed difference is created in which the second portion stretched by the rotating member is slower than the first portion stretched by the tensioning member. Claim 4 The invention described herein is characterized in that the other member is a fixing member provided at a position opposite to the tensioning member with respect to the receiving portion. 3 This is the belt unit described in [the document]. Claim 5 The invention described herein is characterized in that the fixing member is made of a non-metallic material. 4 This is the belt unit described in [the document]. Claim 6 The invention described herein is characterized in that the fixing member is made of metal. 4 This is the belt unit described in [the document]. Claim 7 The invention described herein comprises: an image forming unit that forms an image; a strip-shaped member configured to be able to move in a circular motion and to transfer the image formed by the image forming unit onto a recording material; a tensioning member that is rotatable on an axis and stretches the strip-shaped member; and a rotating member provided on the axis so as to be rotatable relative to the tensioning member, having a receiving portion that stretches the strip-shaped member and receives the strip-shaped member from the axial direction as it moves in the axial direction. The rotating member is provided at a position on the tensioning member side relative to the receiving portion of the rotating member and has a shape that becomes narrower as it approaches the receiving portion. It is an image forming apparatus. [Effects of the Invention]

[0006] According to the invention of claim 1 、 Compared to a configuration without a shaped section, the axial movement of the strip-shaped member can be suppressed. Claim 2 According to this, compared to cases where the shaped part is not tapered, it is possible to suppress the strip-shaped member from riding up onto the tensioning member. Claim 3 According to this invention, movement can be suppressed compared to cases where a speed difference is not used to suppress the axial movement of the strip-shaped member. Claim 4 According to this invention, movement can be suppressed compared to the case where other members are not fixed members. Claim 5 According to this invention, the frictional force can be increased compared to the case where the fixing member is not made of non-metallic material. Claim 6 According to this invention, the durability of the fixing member can be increased compared to the case where the fixing member is not made of metal. Claim 7 According to the invention, Compared to cases without a shaped part, the axial movement of the strip-shaped member is suppressed. can. [Brief explanation of the drawing]

[0007] [Figure 1] This is a front view showing the overall configuration of the image forming apparatus. [Figure 2] This is a schematic diagram showing a part of the configuration of the transfer conveyor belt unit according to this embodiment. [Figure 3] This figure shows the conveyor belt moving in the axial direction. [Figure 4] This diagram illustrates the case where the end portion of the conveyor belt is received by the receiving portion of the pulley. (a) shows the state where the contact portion of the pulley is separated from the washer, and (b) shows the state where the contact portion is in contact with the washer. [Figure 5] This is a block diagram illustrating the interaction between the conveyor belt, the pressure roll, and the pulley. [Figure 6] It is a diagram illustrating the behavior of a conveyance belt. [Figure 7] It is a schematic diagram showing a part of the configuration of a transfer conveyance belt unit according to a modified example, where (a) shows a state where the contact portion of the pulley is separated from the fixed holding member, and (b) shows a state where the contact portion is in contact with the fixed holding member. MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front view showing the overall configuration of an image forming apparatus 1. The image forming apparatus 1 includes an image forming section 10 that forms an image on a sheet P, which is an example of a recording material, based on image data.

[0009] The image forming section 10 is provided with an image forming unit 11 that forms a black (K) toner image (image). The image forming unit 11 is provided with a photosensitive drum 12, a charger 13 that charges the photosensitive drum 12, and a laser exposure device 14 that exposes the photosensitive drum 12.

[0010] The photosensitive drum 12 is charged by the charger 13. Further, the photosensitive drum 12 is exposed by the laser exposure device 14, and an electrostatic latent image is formed on the photosensitive drum 12. Further, each image forming unit 11 is provided with a developing device 15 that develops the electrostatic latent image formed on the photosensitive drum 12, and a cleaner 16 that cleans the surface of the photosensitive drum 12 after transfer.

[0011] The image forming section 10 is also provided with a transfer conveyance belt unit 20 that transfers the black toner image formed on the photosensitive drum 12 onto the sheet P and conveys the sheet P, and a fixing device 30 that fixes the toner image transferred onto the sheet P to the sheet P.

[0012] The transfer conveyor belt unit 20 includes a conveyor belt 21 that conveys the paper P from the transfer section T toward the fixing device 30, a transfer roll 22 located upstream of the conveyor belt 21 and facing the photoreceptor drum 12 to which the transfer voltage is applied, and a pressing roll 23 for pressing the conveyor belt 21 toward the photoreceptor drum 12. The transfer roll 22 has a crown shape and a foamed rubber layer.

[0013] Furthermore, the transfer conveyor belt unit 20 includes a peeling roll 24 located downstream of the conveyor belt 21 in the paper conveying direction, which peels the paper P from the conveyor belt 21, and a blade 25 that cleans the surface of the conveyor belt 21 after conveying. A transport guide 26 is provided on the upstream side of the transfer transport belt unit 20 in the paper transport direction to guide the paper P to the transfer section T. In addition, a chute 27 is provided between the transport belt 21 and the fixing device 30 to guide the paper P transported by the transport belt 21 to the fixing device 30.

[0014] In this example, the transfer transport belt unit 20 is driven by the motor that drives the photoreceptor drum 12, but it is also possible to use an example where the transfer transport belt unit 20 is driven by a motor separate from the motor that drives the photoreceptor drum 12. The transfer conveyor belt unit 20 is an example of a belt unit, the conveyor belt 21 is an example of a strip-shaped member, and the pressing roll 23 is an example of a tensioning member.

[0015] The fixing device 30 is provided with a pressure roll 31 and a fixing roll 32. The pressure roll 31 is pressed against the fixing roll 32 and pressurizes the paper P passing between the fixing roll 32 and the pressure roll 31. The pressure roll 31 comprises a core, an elastic layer covering the core, a release layer further covering the elastic layer, and a heating source located in the center of the core. The fixing roll 32 also comprises a core, an elastic layer covering the core, a release layer further covering the elastic layer, and a heating source located in the center of the core.

[0016] The image forming apparatus 1 includes a control unit 40 that controls each functional unit provided in the image forming apparatus 1, and an image processing unit 50 that performs image processing on image data from a personal computer (PC) or an image reading device. The control unit 40 and the image processing unit 50 are configured as ASICs (Application Specific ICs). Alternatively, the control unit 40 and the image processing unit 50 may be implemented using a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory) for executing software and performing calculations.

[0017] In the image forming apparatus 1, the image processing unit 50 performs image processing on image data from a PC or image reader, and the processed image data is supplied to the image forming unit 11. Then, in the image forming unit 11, the photoreceptor drum 12 rotates in the direction of arrow A, is charged by the charger 13, and is exposed by the laser exposure unit 14, which emits light based on the image data transmitted from the image processing unit 50. As a result, an electrostatic latent image relating to a black image is formed on the photoreceptor drum 12. Then, the electrostatic latent image formed on the photoreceptor drum 12 is developed by the developer unit 15, and a black toner image is formed on the photoreceptor drum 12.

[0018] The image forming apparatus 1 includes, as a paper transport system, a paper tray 60 for holding paper P, a pickup roll 61 for picking up and transporting the paper P accumulated in the paper tray 60 at a predetermined timing, and a transport roll 62 for transporting the paper P fed out by the pickup roll 61. It also includes, as a paper transport system, a resist roll 63 for feeding the transported paper P to the transfer section T at a predetermined timing.

[0019] More specifically, the image forming apparatus 1 is equipped with a detection sensor 51 that detects the leading edge of the paper P supplied to the transfer section T. The detection sensor 51 is positioned in front of the transfer section T. When the detection sensor 51 detects the leading edge of the paper P in front of the transfer section T, the paper is temporarily stopped, and the paper P is advanced to the transfer section T by the register roll 63 in time with the arrival of the black toner image from the photoreceptor drum 12 at the transfer section T. The black toner image is then transferred to the paper P in the transfer section T, where the transfer roll 22 presses against the photoreceptor drum 12.

[0020] In the fixing device 30, the paper P is sandwiched between the pressure roll 31 and the fixing roll 32. Specifically, the paper P is sandwiched between the pressure roll 31, which is moving in a counterclockwise direction, and the fixing roll 32, which is rotating in a clockwise direction. This pressurizes and heats the paper P, fixing the toner image on the paper P. After fixing is complete, the paper P is transported to the paper stacking section by the discharge roll.

[0021] In the transfer conveyor belt unit 20, when the conveyor belt 21 moves in a circular motion, there is a risk that the conveyor belt 21 may come into contact with the fixing member located at the end of the pressing roll 23, for example, due to its movement towards the fixing member. To address this, one method is to provide tapered sections at both ends of the pressing roll 23, where the central portion of the pressing roll 23 is formed to have a larger diameter. In other words, the end portion of the conveyor belt 21 is wrapped around the tapered section of the pressing roll 23, suppressing its movement towards the fixing member and preventing the conveyor belt 21 from coming into contact with the fixing member. However, it is conceivable that the suppression of the movement of the conveyor belt 21 relative to the pressing roll 23 by the tapered shape of the pressing roll 23 may not be sufficient. Therefore, in this embodiment, an additional member capable of relative rotation to the pressing roll 23 is placed on the axis of the pressing roll 23, and a configuration is adopted that receives the conveyor belt 21 when the conveyor belt 21 moves in the axial direction. Details will be described later.

[0022] Figure 2 is a schematic diagram showing part of the configuration of the transfer conveyor belt unit 20 according to this embodiment, and is a diagram illustrating the holding structure of the pressure roll 23 that tensions the conveyor belt 21. Note that in Figure 2, the upper part of the conveyor belt 21 is omitted in order to show the pressure roll 23 and the pulley 71 described later. Note that the conveyor belt 21 is tensioned on two or more axes.

[0023] As shown in Figure 2, the pressing roll 23 of the transfer conveying belt unit 20 has an intermediate portion 23a located midway with respect to the axial direction H, and cylindrical small-diameter ends 23b that form the ends of the pressing roll 23 and are formed to be smaller in diameter than the intermediate portion 23a. The pressing roll 23 is rotatable around axis J. The middle section 23a of the pressure roll 23 has an axial length H smaller than the width of the conveyor belt 21.

[0024] The small-diameter end 23b of the pressing roll 23 is inserted into a recess in the fixed holding member 28. This fixed holding member 28 is fixed to the frame (not shown) of the image forming apparatus 1 (see Figure 1). Thus, both ends of the pressing roll 23 are rotatably held by the pair of fixed holding members 28.

[0025] To further explain, a pulley 71 and a washer 72 are rotatably held at the small-diameter end 23b of the pressing roll 23. The pulley 71 and washer 72 are located between the middle section 23a of the pressing roll 23 and the fixed holding member 28. The pulley 71 held at the small-diameter end 23b is movable in the axial direction H. The pulleys 71 are located at each of the left and right ends of the pressing roll 23, forming a pair.

[0026] The pulley 71 is a separate component from the pressure roll 23 and is rotatable around the axis J. Furthermore, the pulley 71 is rotatable relative to the pressure roll 23. The pulley 71 is an example of a rotating component. The pulley 71 has a hole 71a that penetrates in the axial direction H and has an inner diameter corresponding to the outer diameter of the small diameter end 23b of the pressing roll 23, as well as a receiving portion 71b, a tapered portion 71c, and a contact portion 71d.

[0027] The receiving portion 71b is located between the tapered portion 71c and the contact portion 71d, and has a flange shape formed around its entire circumference with a larger outer diameter than the contact portion 71d. Furthermore, the end face of the receiving portion 71b on the tapered portion 71c side functions as a receiving surface that receives the end portion 21b of the conveyor belt 21. This receiving surface is formed in a flat shape, not an uneven shape. In this embodiment, the outer diameter of the receiving portion 71b is the same as the outer diameter of the pressing roll 23, but it may be made larger than the outer diameter of the pressing roll 23 if it is possible to secure a gap with other parts. For example, the length may be increased by the thickness of the conveyor belt 21.

[0028] The tapered portion 71c has a linear inclined surface on its outer surface that becomes narrower and has a smaller outer diameter as it approaches the receiving portion 71b. In other words, the inclined surface of the tapered portion 71c has its smallest outer diameter on the receiving portion 71b side and its largest outer diameter on the pressing roll 23 side of the inclined surface. The pulley 71 contacts the conveyor belt 21 with the outer surface of the tapered portion 71c, thereby allowing it to rotate together with the pressure roll 23 due to the rotational energy of the conveyor belt 21. While it is preferable that this maximum outer diameter is the same as the outer diameter of the pressing roll 23, it may also be smaller than the outer diameter of the pressing roll 23. The tapered portion 71c is located on the pressing roll 23 side relative to the receiving portion 71b. The tapered portion 71c is an example of a shaped portion. In this embodiment, the tapered portion 71c is formed on a straight inclined surface, but it is not limited to this. It can also be formed on a curved inclined surface, for example, by bulging outward or concave inward.

[0029] When the contact portion 71d is held by the small-diameter end portion 23b of the pressing roll 23, it is positioned opposite the washer 72. In the pulley 71, when the receiving portion 71b receives the end portion 21b of the conveyor belt 21, the contact portion 71d is pressed against the washer 72. Due to the frictional force generated by this pressing, the pulley 71, which was previously rotating at the same speed as the pressing roll 23, slows down and begins to rotate at a lower speed than the pressing roll 23. In addition, the contact portion 71d of the pulley 71 and the washer 72 are configured to create a speed difference between the pulley 71 and the pressing roll 23.

[0030] Furthermore, the pulley 71 has a small-diameter portion 71e between the receiving portion 71b and the tapered portion 71c, with an outer diameter smaller than the minimum outer diameter of the tapered portion 71c. In other words, the tapered portion 71c is not formed continuously with the receiving portion 71b in the axial direction H. Furthermore, in this embodiment, the pulley 71 is provided with a tapered portion 71c, but it is not limited to this, and instead of a tapered portion 71c, it may be a circumferential portion formed with the same diameter.

[0031] The washer 72, like the fixing and holding member 28, is a fixed-side member, and in this embodiment, it is a ring-shaped member used as a fastening member when attaching with screws, for example. The washer 72 is made of metal, but is not limited to this, and may be made of a non-metallic material such as rubber, which has a relatively high coefficient of friction. The washer 72 has a flat surface, but is not limited to this, and may have an uneven shape to achieve a higher coefficient of friction.

[0032] In this embodiment, the washer 72 is a fixed member, but it is not limited to this. It may also be rotatable relative to the fixed holding member 28, but with a higher resistance to rotation than the pulley 71 so that frictional force is generated when it comes into contact with the pulley 71. The washer 72 is a component that is pressed against the pulley 71, and is an example of other components, and an example of a fixing component.

[0033] Figure 3 shows the state in which the conveyor belt 21 has moved in the axial direction H. Figure 4 illustrates the case in which the end portion 21b of the conveyor belt 21 is received by the receiving portion 71b of the pulley 71, where (a) shows the state in which the contact portion 71d of the pulley 71 is separated from the washer 72, and (b) shows the state in which the contact portion 71d is in contact with the washer 72. Note that Figures 4(a) and 4(b) illustrate the axial pressing action when the pulley 71 is pressed in the axial direction H (see Figure 3) by the conveyor belt 21. In Figure 4(a), the gap G is shown in dimensions that are easily visible, but it is sufficient that the frictional force between the pulley 71 and the washer 72 increases due to the pressing action, and the gap G does not necessarily have to be of a size that is easily visible.

[0034] As shown in Figure 3, when the conveyor belt 21 moves axially H, the end portion 21b of the conveyor belt 21 abuts against the end face of the receiving portion 71b of the pulley 71. When the conveyor belt 21 is stopped by this abutment, the pulley 71 is pushed in the direction of the washer 72.

[0035] More specifically, when the conveyor belt 21 is not abutting against the receiving portion 71b of the pulley 71, the contact portion 71d of the pulley 71 is slightly separated from the washer 72 by a gap G, as shown in Figure 4(a). On the other hand, when the conveyor belt 21 abuts against the receiving portion 71b, the conveyor belt 21 pushes the receiving portion 71b toward the washer 72, eliminating the gap G, and as shown in Figure 4(b), the rotating pulley 71 rotates while in contact with the fixed washer 72. Furthermore, by providing the pulley 71 with a tapered section 71c, the edge of the conveyor belt 21 can bend toward the shaft J, and compared to when the pulley 71 does not have a tapered shape, the required height of the guide at the receiving section 71b can be achieved in a smaller space.

[0036] Next, we will explain the difference in the behavior of the conveyor belt 21 between Figure 4(a) and Figure 4(b). Figure 5 is a block diagram illustrating the interaction between the conveyor belt 21, the pressure roll 23, and the pulley 71, and Figure 6 is a diagram illustrating the behavior of the conveyor belt 21. In Figure 5, for the sake of explanation, the width direction of the conveyor belt 21 is shown divided into a central portion 21a and two end portions 21b. The central portion 21a refers to the region in contact with the middle portion 23a of the pressure roll 23, and the end portions 21b refer to the region not in contact with the middle portion 23a. The central portion 21a is an example of the first portion, and the end portions 21b are an example of the second portion.

[0037] When the conveyor belt 21 is not in contact with either of the pair of pulleys 71 (see Figures 2 and 4(a)), the rotating conveyor belt 21 drives the pressing roll 23 and the pulleys 71 to rotate, as shown in Figure 5(a). That is, the central portion 21a of the conveyor belt 21 that is in contact with the pressing roll 23 rotates the pressing roll 23, and the end portion 21b that is in contact with the pulleys 71 rotates the pulleys 71. In this way, the central portion 21a and the end portion 21b of the conveyor belt 21 act to maintain the rotational speed of the pressing roll 23 and the pulleys 71, so that the pressing roll 23 and the pulleys 71 rotate at the same speed.

[0038] On the other hand, when the conveyor belt 21 is abutting against one of the pair of pulleys 71 (see Figures 3 and 4(b)), the pulley 71 rotates while in contact with the fixed washer 72, as described above, and is decelerated by the axial pressing action. That is, as shown in Figure 5(b), when the pulley 71 decelerates, the end portion 21b of the conveyor belt 21 moves at a lower speed than the central portion 21a due to the frictional force with the pulley 71. In this way, as the conveyor belt 21 comes into contact with the pulley 71, the speed difference between the end portion 21b and the central portion 21a of the conveyor belt 21 increases, causing the end portion 21b of the conveyor belt 21 to slow down.

[0039] To explain further, as shown in Figure 6, when the central portion 21a of the conveyor belt 21 rotates at speed Va and the end portion 21b rotates at speed Vb (Va > Vb), the speed difference ΔV, which is the difference between speeds Va and Vb, generates a force that causes the conveyor belt 21 to return towards the center. This makes it possible to prevent damage to the conveyor belt 21 due to riding up onto the pressure roll 23. Furthermore, in this embodiment, as described above, since the pulley 71 is equipped with a tapered portion 71c, the decelerated end portion 21b of the conveyor belt 21 wraps around the tapered portion 71c, thereby suppressing the amount of movement of the conveyor belt 21.

[0040] In this embodiment, the pressing roll 23 is configured to be stretched over the conveyor belt 21, but it is not limited to this configuration. The pressing roll may only contact and stretch over the conveyor belt 21 when the conveyor belt 21 moves in the axial direction H, and may not stretch over the conveyor belt 21 in other cases.

[0041] Although this embodiment has been described, other configurations may be adopted. That is, in this embodiment, the pulley 71 is decelerated by the friction generated between the conveyor belt 21 and the fixed washer 72 when the conveyor belt 21 abuts against the pulley 71, but this is not the only configuration. Modifications will be described below. Figure 7 is a schematic diagram showing part of the configuration of a modified transfer conveyor belt unit 20, where (a) shows the state in which the contact portion 71d of the pulley 71 is separated from the fixed holding member 28, and (b) shows the state in which the contact portion 71d is in contact with the fixed holding member 28. Figure 7 corresponds to Figure 4 which describes this embodiment. Note that since the modified embodiment has the same basic configuration as this embodiment, its illustration and description may be omitted.

[0042] As shown in Figure 7(a), the modified transfer conveyor belt unit 20 does not have a washer 72 (see Figure 4), unlike in this embodiment. Therefore, the pulley 71 is adjacent to the fixed holding member 28.

[0043] Furthermore, the modified transfer conveyor belt unit 20 differs from this embodiment in that it includes a fixed opposing member 73 that faces the end face of the receiving portion 71b of the pulley 71. The fixed opposing member 73 is located on the opposite side of the conveyor belt 21 from the receiving portion 71b. The fixed opposing member 73 may be made of metal, or it may be made of a non-metallic material, such as rubber. The fixed opposing member 73 is an example of another member, and is an example of a fixed member.

[0044] When the conveyor belt 21 is not abutting against the receiving portion 71b of the pulley 71, as shown in Figure 7(a), the receiving portion 71b of the pulley 71 is slightly separated from the fixed opposing member 73 by a gap G.

[0045] On the other hand, when the conveyor belt 21 abuts against the receiving portion 71b of the pulley 71, the conveyor belt 21 pushes the receiving portion 71b toward the fixed opposing member 73, eliminating the gap G. As shown in Figure 7(b), the rotating pulley 71 rotates while in contact with the fixed opposing member 73. This makes it possible to achieve the same behavior of the conveyor belt 21 as in this embodiment (see Figure 6).

[0046] Furthermore, although this embodiment describes a transfer method in which the image is transferred from the photosensitive drum 12 (see Figure 1) to the paper, it may also be applied to a transfer method in which the image is transferred to the paper via an intermediate transfer body. [Explanation of Symbols]

[0047] 1…Image forming apparatus, 10…Image forming section, 20…Transfer conveyor belt unit, 21…Conveyor belt, 21a…Central section, 21b…End section, 23…Pressing roll, 71…Pulley, 71b…Receiving section, 71c…Tapered section, 72…Washer, 73…Fixed opposing member

Claims

1. A strip-shaped member configured to allow circulating movement, A tensioning member that is rotatable on an axis and stretches the strip-shaped member, The rotating member is provided on the shaft so as to be rotatable relative to the tensioning member, and has a receiving portion that tensions the strip-shaped member and receives the strip-shaped member as it moves in the axial direction from the axial direction, The rotating member is a belt unit provided at a position on the tensioning member side relative to the receiving portion of the rotating member and having a shape that becomes narrower as it approaches the receiving portion.

2. The belt unit according to claim 1, characterized in that the aforementioned shaped portion is tapered.

3. The belt unit according to claim 1, characterized in that when the strip-shaped member is received by the receiving portion from the axial direction, the rotating member is decelerated by the axial pressing action with other members, resulting in a speed difference in which the second portion stretched by the rotating member is slower than the first portion stretched by the tensioning member.

4. The belt unit according to claim 3, characterized in that the other member is a fixing member provided at a position opposite to the tensioning member with respect to the receiving portion.

5. The belt unit according to claim 4, characterized in that the fixing member is made of nonmetal.

6. The belt unit according to claim 4, characterized in that the fixing member is made of metal.

7. An image forming unit that forms an image, A strip-shaped member configured to allow cyclic movement and to transfer the image formed by the image forming unit to a recording material, A tensioning member that is rotatable on an axis and stretches the strip-shaped member, The rotating member is provided on the shaft so as to be rotatable relative to the tensioning member, and has a receiving portion that tensions the strip-shaped member and receives the strip-shaped member as it moves in the axial direction from the axial direction, The rotating member is provided at a position on the tensioning member side relative to the receiving portion of the rotating member and has a shape that becomes narrower as it approaches the receiving portion.

Images