Belt driving device, transfer device and image forming device

Abstract

A belt drive device, a transfer device, and an image forming device are provided. The device comprises: an endless belt member; a plurality of rotating members that span the belt member and rotate about respective rotating axes extending in the width direction of the belt member; and contact members that are disposed on both sides of the belt member in the width direction and contact the belt member to suppress deviation of the belt member in the width direction. In the direction of the rotating axis, the dimension of the portion of at least one first rotating member among the plurality of rotating members that contacts the belt member is shorter than the width dimension of the belt member, and both width-direction ends of the belt member are separated from the first rotating member. The contact member comprises at least: a first contact point that contacts the belt member and presses the belt member against the first rotating member; and a second contact point that contacts the belt member closer to the width-direction end than the first contact point. At the second contact point, the angle between the contact member and the rotating axis is larger than that at the first contact point.

Description

Technical Field

[0001] The present invention relates to a belt driving device, a transfer device and an image forming device. Background Art

[0002] In devices that drive an endless belt member mounted on multiple rotating components, the belt member may sometimes experience lateral deviation in the width direction, i.e., in the direction of the rotating components' rotational axes. The force causing this lateral deviation is primarily due to the non-parallel rotational axes of the multiple rotating components. To suppress this lateral deviation, it has been proposed to provide guide members that press the widthwise ends of the belt member in directions oblique to the rotational axes (see Japanese Patent Application Publication Nos. 2003-267580 and 2005-257863).

[0003] When the guide member proposed in Patent Document 2 is provided, lateral deviation of the belt member can be suppressed compared to when no guide member is provided.

[0004] However, even with the guide members, if the rotation axes of the multiple rotating components become significantly offset from parallel and the force of lateral deviation increases, lateral deviation may not be completely suppressed. On the other hand, arranging the rotation axes of the multiple rotating components in parallel with high precision may lead to increased costs. Summary of the Invention

[0005] An object of the present invention is to provide a belt driving device, a transfer device, and an image forming apparatus capable of suppressing lateral deviation more strongly than when a guide member is arranged as described above.

[0006] According to a first aspect of the present disclosure, there is provided a belt drive device having:

[0007] annular belt member;

[0008] a plurality of rotating members that extend over the belt member and rotate about respective rotating axes extending in the width direction of the belt member; and

[0009] contact members, which are respectively arranged on both sides of the belt member in the width direction and contact the belt member to suppress the belt member from deviating in the width direction.

[0010] In the direction of the rotation axis, a portion of at least one first rotating member among the plurality of rotating members that contacts the belt member is shorter than a width dimension of the belt member, and both widthwise end portions of the belt member are separated from the first rotating member.

[0011] The contact member has at least: a first contact point, which contacts the belt member and presses the belt member against the first rotating member; and a second contact point, which contacts the belt member at a corresponding end portion in the width direction end portion closer to the first contact point, and at the second contact point, the angle between the contact member and the rotating axis is larger than that at the first contact point.

[0012] According to the second aspect of the present disclosure, the contact member is a rotating contact member that rotates about its rotation axis, and the rotating contact member includes portions having different diameters in the direction of the rotation axis.

[0013] According to the third aspect of the present disclosure, the diameter of the contact member at the center in the direction of the rotation axis of the contact member is smaller than the diameters at both ends.

[0014] According to the fourth aspect of the present disclosure, the contact member has an outer peripheral surface formed of a curved surface that is narrowed at the center in the direction of the rotation axis of the contact member.

[0015] According to the fifth aspect of the present disclosure, the bearing supporting the rotating shaft of the contact member has a shape that avoids contact with the belt member.

[0016] According to the sixth aspect of the present disclosure, the first rotating member is a rotation driving member that drives the belt member to cause the belt member to circulate.

[0017] According to the seventh aspect of the present disclosure, the contact member is arranged at a position closer to the most upstream position than the most downstream position in the region where the belt member contacts the first rotating member in the circulating direction of the belt member.

[0018] According to an eighth aspect of the present disclosure, the plurality of rotating members include a second rotating member that, together with the first rotating member, stretches the belt member, and a portion of the second rotating member that contacts the belt member is longer in the width direction than a portion of the first rotating member that contacts the belt member.

[0019] According to a ninth aspect of the present disclosure, there is provided a belt drive device comprising:

[0020] annular belt member;

[0021] a plurality of rotating members that extend over the belt member and rotate about respective rotating axes extending in the width direction of the belt member; and

[0022] contact members, which are respectively arranged on both sides of the belt member in the width direction and contact the belt member to suppress the belt member from deviating in the width direction.

[0023] In the direction of the rotation axis, a portion of at least one first rotating member among the plurality of rotating members that contacts the belt member is shorter than a width dimension of the belt member, and both widthwise end portions of the belt member are separated from the first rotating member.

[0024] The contact member is a rotating contact member having an outer peripheral surface formed of a curved surface that is narrowed at the center in the direction of the rotation axis of the contact member.

[0025] According to a tenth aspect of the present disclosure, there is provided a transfer device comprising:

[0026] an endless belt member whose outer peripheral surface contacts a recording material and transfers an image to the recording material by applying a voltage thereto;

[0027] a plurality of rotating members that extend over the belt member and rotate about respective rotating axes extending in the width direction of the belt member; and

[0028] contact members, which are respectively arranged on both sides of the belt member in the width direction and contact the belt member to suppress the belt member from deviating in the width direction.

[0029] In the direction of the rotation axis, a portion of at least one first rotating member among the plurality of rotating members that contacts the belt member is shorter than a width dimension of the belt member, and both widthwise end portions of the belt member are separated from the first rotating member.

[0030] The contact member has at least a first contact point that contacts the belt member and a second contact point that contacts the belt member closer to the widthwise end portion than the first contact point, wherein the contact member has a larger angle with the rotation axis at the second contact point than at the first contact point.

[0031] According to an eleventh aspect of the present disclosure, there is provided a transfer device comprising:

[0032] an endless belt member, the outer peripheral surface of which is in contact with a recording material and transfers an image to the recording material by applying a voltage thereto;

[0033] a plurality of rotating members that extend over the belt member and rotate about respective rotating axes extending in the width direction of the belt member; and

[0034] contact members, which are respectively arranged on both sides of the belt member in the width direction and contact the belt member to suppress the belt member from deviating in the width direction.

[0035] In the direction of the rotation axis, a portion of at least one first rotating member among the plurality of rotating members that contacts the belt member is shorter than a width dimension of the belt member, and both widthwise end portions of the belt member are separated from the first rotating member.

[0036] The contact member is a rotating contact member having an outer peripheral surface formed of a curved surface that is narrowed at the center in the direction of the rotation axis of the contact member.

[0037] According to the 12th embodiment of the present disclosure, an image forming device is provided, which comprises: a conveying portion that conveys a recording material; an image forming portion that forms a colorant image; and a transfer device according to claim 10 or 11, which transfers the colorant image formed by the image forming portion onto the recording material conveyed by the conveying portion.

[0038] (Effect)

[0039] According to each of the above-mentioned schemes 1, 9, 10, 11 and 12, lateral deviation can be further strongly suppressed compared to the case where the above-mentioned guide components are configured, that is, compared to the case where contact components such as flat plates or simple cylindrical rollers are configured so that all contact points with the belt components have the same angle with the rotating axis.

[0040] According to each of the second and third aspects, the friction between the belt member and the contact member can be reduced.

[0041] According to the fourth aspect, a plurality of continuous contact points can be obtained.

[0042] According to the fifth aspect, it is possible to suppress the belt member from being damaged.

[0043] According to the sixth aspect, lateral deviation can be more strongly suppressed compared to a case where the first rotating member is a driven rotating member.

[0044] According to the seventh aspect, lateral displacement can be more strongly suppressed compared to a case where the contact member is arranged at a position closer to the most downstream position than the most upstream position.

[0045] According to the eighth aspect, lateral deviation can be more strongly suppressed compared to a case where the length of the second rotating member is the same as or shorter than that of the first rotating member. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic structural diagram showing one embodiment of the image forming apparatus of the present disclosure.

[0047] Figure 2 is a side view schematically showing the structure of the secondary transfer device.

[0048] Figure 3 1 is a top view schematically showing a secondary transfer device.

[0049] Figure 4 (A) shows a comparative example of a contact member, and (B) is an explanatory diagram of the principle of the contact member according to the present embodiment.

[0050] Figure 5 The figures show a first example (A) and a second example (B) of a contact member.

[0051] Figure 6 These are diagrams showing the third example (A) and the fourth example (B) of the contact member.

[0052] Figure 7 This is a diagram showing a fifth example of the contact member.

[0053] Figure 8 These are diagrams showing the sixth example (A) and the seventh example (B) of the contact member.

[0054] Figure 9 The figures show the eighth example (A) and the ninth example (B) of the contact member.

[0055] Figure 10 This is a schematic diagram of a roller-shaped contact member and a support member that supports the contact member.

[0056] Figure 11 This is a diagram showing an example of experimental data. DETAILED DESCRIPTION

[0057] Hereinafter, embodiments of the present invention will be described.

[0058] Figure 1 This is a schematic structural diagram showing one embodiment of the image forming apparatus of the present invention.

[0059] Figure 1 The image forming apparatus 1 shown is a so-called tandem color printer. In this image forming apparatus 1, paper P is used as the recording material. In addition to paper P, plastic sheets or envelopes can also be used as the recording material. However, in the following description, paper P will be used as a representative recording material.

[0060] Image forming apparatus 1 includes four image engines 10Y, 10M, 10C, and 10K corresponding to four colors: Y (yellow), M (magenta), C (cyan), and K (black). In this embodiment, each image engine 10Y, ..., 10K forms a toner image using a so-called electrophotographic method. Each image engine 10Y, ..., 10K sequentially forms a toner image of each color on each photoreceptor drum 11Y, 11M, 11C, and 11K through the steps of charging, exposure, and development.

[0061] The image forming apparatus 1 of this embodiment adopts an indirect transfer method and includes an intermediate transfer belt 30. The image forming apparatus 1 also includes a secondary transfer device 50, a fixing device 60, and a paper conveying unit 80.

[0062] The intermediate transfer belt 30 is an endless belt stretched over belt support rollers 31 to 35 , and circulates in a counterclockwise direction indicated by arrow A via the image engines 10Y, 10M, 10C, and 10K and the secondary transfer device 50 .

[0063] In each imaging engine 10Y, 10K, primary transfer rollers 15Y, 15M, 15C, and 15K are positioned opposite the photoreceptor drums 11Y, 11K, with an intermediate transfer belt 30 interposed between the photoreceptor drums and the primary transfer rollers. Voltage is applied to the primary transfer rollers 15Y, 15K, which electrostatically attract the toner images on the photoreceptor drums 11Y, 11K to the intermediate transfer belt 30. The toner images of each color formed by the imaging engines 10Y, 10K are sequentially transferred, overlapping each other, to the intermediate transfer belt 30 by the primary transfer rollers 15Y, 15K. As a result of this transfer, a color image is formed on the intermediate transfer belt 30. The intermediate transfer belt 30, while holding the color image, moves, conveying the color image to the secondary transfer unit 50.

[0064] The secondary transfer device 50 is located so as to sandwich the intermediate transfer belt 30 with the support roller 34 , which is one of the belt support rollers 31 to 35 , and transfers a color image by sandwiching the paper P with the intermediate transfer belt 30 .

[0065] Paper sheets P are stored in a stack on a paper tray T located below the image forming apparatus 1. Paper sheets P are removed from the paper tray T one by one by a feed roller 81 and a sorting roller 82 included in a paper transport unit 80. The sheets are then transported along a transport path R in the direction indicated by arrow B by transport rollers 83. Registration rollers 84 of the paper transport unit 80 feed the paper sheets P into the secondary transfer unit 50 in accordance with the transport timing of the color image being transported by the intermediate transfer belt 30.

[0066] As will be described in detail later, the secondary transfer device 50 transfers the color image from the intermediate transfer belt 30 to the paper P by applying a voltage. The secondary transfer device 50 is an embodiment of the belt drive device of the present invention and also an embodiment of the transfer device of the present disclosure. The paper P, to which the color image has been transferred by the secondary transfer device 50, is transported to the fixing device 60 via the secondary transfer device 50 and the transport rollers 83 of the paper transport unit 80.

[0067] The image engines 10Y, 10M, 10C, and 10K correspond to an example of an image forming unit in the present invention. Furthermore, the paper conveying unit 80 corresponds to an example of a conveying unit in the present invention.

[0068] The fixing device 60 fixes the color image on the paper P by heating and pressing the paper P. The paper P to which the color image is fixed by the fixing device 60 is fed out of the image forming apparatus 1 by a feed roller 86 of the paper conveying unit 80 .

[0069] Hereinafter, the secondary transfer device 50 will be described in further detail.

[0070] Figure 2 and Figure 3 Schematic diagram showing the structure of the secondary transfer device 50. Figure 2 A side view is shown in FIG. Figure 3 A top view is shown in FIG. Figure 3 In FIG. 1 , for convenience of explanation, the structure is shown in a state where the interior of the secondary transfer device is seen through.

[0071] The secondary transfer unit 50 includes a transfer roller 51, a peeling roller 52, and an endless transfer belt 53 stretched over these rollers. The secondary transfer unit 50 is assembled into a unit by assembling each component into a transfer unit support frame 501. The transfer roller 51 and the peeling roller 52 have rotational shafts 511 and 521, respectively, which are rotatably supported by the transfer unit support frame 501. The transfer roller 51 and the peeling roller 52 are examples of the plurality of rotating members referred to in the present invention, and the transfer belt 53 is an example of the belt member referred to in the present invention.

[0072] The transfer roller 51 is driven by the transfer motor 56 and rotates clockwise as indicated by the arrow C, thereby driving the transfer belt 53. The transfer belt 53 is a rubber belt with appropriate elasticity, and receives the driving force of the transfer roller 51 and moves along the transfer belt 53. Figure 2 The circular movement is in the clockwise direction indicated by the arrow D.

[0073] The transfer roller 51 presses the transfer belt 53 against the intermediate transfer belt 30 from the inner side of the transfer belt 53. When the paper P is conveyed between the transfer belt 53 and the intermediate transfer belt 30, the paper P is sandwiched between the transfer belt 53 and the intermediate transfer belt 30 and conveyed in the circular direction. The transfer roller 51 is also connected to a power source (not shown), which applies a transfer bias to the transfer roller 51. This transfer bias transfers the color image on the intermediate transfer belt 30 to the paper P while the paper P passes between the transfer belt 53 and the intermediate transfer belt 30.

[0074] The peeling roller 52 is a driven roller having a smaller diameter than the transfer roller 51 and rotates following the movement of the transfer belt 53. The peeling roller 52 sharply bends the moving direction of the transfer belt 53, thereby peeling the leading end of the paper P placed on the transfer belt 53 from the transfer belt 53.

[0075] Here, the length L1 of the portion of the transfer roller 51, excluding the rotation axis 511, that contacts the transfer belt 53 is shorter than the width W of the transfer belt 53. The ends of the transfer belt extend from the transfer roller 51 without contacting the transfer roller 51. Furthermore, contact members 54 are disposed at each end of the transfer roller 51. These contact members 54 contact the transfer belt 53 to press the transfer belt 53 against the transfer roller 51. These contact members 54 function to suppress lateral deviation of the transfer belt 53 in the width direction of the transfer belt 53 (the direction in which the rotation axis 511 of the transfer roller 51 extends).

[0076] On the other hand, the length L2 of the portion of the peeling roller 52 excluding the rotation shaft 521 that contacts the transfer belt 53 is longer than the length L1 of the transfer roller 51 and is the same as the width W of the transfer belt in this embodiment.

[0077] The details of the contact member 54 and the effects of the difference in length between the transfer roller 51 and the peeling roller 52 will be described later.

[0078] The secondary transfer unit 50 includes a cleaning blade 55, the edge of which contacts the outer peripheral surface of the transfer belt 53. The cleaning blade 55 is fixed to the transfer unit support frame 501. As the transfer belt 53 moves, the edge of the cleaning blade 55 rubs against the outer peripheral surface of the transfer belt 53. Toner and other contaminants adhering to the transfer belt 53 are rubbed by the cleaning blade 55 and removed from the transfer belt 53.

[0079] In addition, Figure 3 In the figure, the cleaning blade 55 and the transfer motor 56 are omitted.

[0080] Figure 4 The figure (A) shows a comparative example of a contact part and the figure (B) shows the principle of the contact part of this embodiment. Figure 4 Only one end portion in the width direction of the transfer belt 53 is shown in FIG. 1 , but the same applies to the other end portion.

[0081] When the rotation axis 511 of the transfer roller 51 and the rotation axis 521 of the peeling roller 52 deviate from parallelism, a force is generated that causes the transfer belt 53 to move in the width direction (the direction in which the rotation axis 511 of the transfer roller 51 extends). The direction in which the transfer belt 53 moves in the width direction is different depending on the direction of the parallel deviation. Here, it is assumed that a force is generated in the width direction. Figure 4 The force acts in the direction of movement of the end side shown (direction of arrow D).

[0082] Figure 4 (A) shows a flat plate-shaped contact member 59 as a comparative example. The contact member 59 of this comparative example may be a roller that is rotatable about a rotation axis 591 and has a uniform diameter in the direction of the rotation axis 591.

[0083] If the Figure 4 As shown in (A), when the transfer belt 53 is pressed obliquely relative to the rotation axis 511 of the transfer roller 51 by the contact member 59, a force acts in the direction of arrow E to push back the transfer belt 53, which is about to advance in the direction of arrow D. The greater the force in this pushing-back direction, the more it can overcome the larger force that moves in the direction of arrow D. The ability to overcome the larger force that moves in the direction of arrow D means that the parallelism between the transfer roller 51 and the peeling roller 52 can be lowered, which means that the precision of the components can be reduced, the assembly tolerance can be increased, and cost reduction can be achieved.

[0084] In this Figure 4 In the comparative example shown in (A), the push-back is performed using a flat contact member 59 or a roller having a uniform diameter, i.e., the contact member 59. Using such a contact member 59 allows for push-back with a greater force than when no contact member 59 is provided, thereby allowing for a corresponding tolerance in the accuracy of the components and in assembly.

[0085] However, when the force of the transfer belt 53 advancing in the direction of arrow D is large, the transfer belt 53 bulges upward from the transfer roller 51 as shown by the dotted line, thereby reducing the force in the push-back direction. Therefore, a contact member that can withstand the larger force of the transfer belt 53 advancing in the direction of arrow D is required.

[0086] exist Figure 4 The shape of the contact member 54 is not shown in FIG. Figure 5 The diagram will be shown later.

[0087] Should Figure 4The contact member 54 shown in (B) includes: a first contact point d1, which contacts the transfer belt 53 and makes the transfer belt 53 press against the transfer roller 51; and a second contact point d2, which contacts the transfer belt 53 at a position closer to the end side in the width direction than the first contact point d1. At the second contact point d2, the contact member 54 contacts the transfer belt 53 with a larger angle α2 with the rotating shaft 511 than at the first contact point d1. As a typical example, at the first contact point d1, the angle α1 between the contact member 54 and the rotating shaft 511 is 0°, that is, the transfer belt 53 is pressed in a direction parallel to the rotating shaft 511. In addition, at the second contact point d2, the contact member 54 presses the transfer belt 53 in a direction with an angle α2 of 45° with the rotating shaft 511. In this way, it is possible to suppress Figure 4 The bulge of the transfer belt 53 shown by the dotted line in (A) is Figure 4 Compared to the flat contact member 59 shown in FIG. (A), the contact member 54 can overcome a larger force advancing in the direction of arrow D. In addition, at the first contact point d1, the angle α1 between the contact member 54 and the rotating shaft 511 may not be 0°. For example, the transfer belt 53 may be pressed at an angle smaller than the angle α2 at the second contact point d2, such as α1 = 15°.

[0088] Various specific examples of the contact member in this embodiment will be described below.

[0089] Figure 5 The figures show a first example (A) and a second example (B) of a contact member.

[0090] Figure 5 The first example of the contact member 54A shown in FIG. 5A has a bent flat plate shape. Furthermore, the contact member 54A is arranged so that its first surface 541 facing inward is parallel to the rotation axis 511 and the first surface 541 and the second surface 542 are in contact with the transfer belt 53. The transfer belt 53 circulates while sliding relative to the contact member 54A.

[0091] Here, the end portion 531 of the transfer belt 53 in the width direction, which is separated from the contact member 54A, is bent in the direction opposite to the direction in which it is bent by the contact member 54A, that is, in a direction parallel to the rotation axis 511. The end portion 531 in the width direction of the transfer belt 53 is bent in this direction, thereby increasing the rigidity of the portion of the transfer belt 53 pressed by the contact member 54A, and being able to overcome the force of movement in the direction of arrow D with a stronger force. Figure 3As shown, in this embodiment, the peeling roller 52 has a length L2 that is longer than the transfer roller length L1 and approximately the same as the width W of the transfer belt 53. Therefore, compared to a case where the peeling roller 52 has the same length as the transfer roller 51, the end portion of the transfer belt 53 in the width direction is pulled by the peeling roller 52, and the end portion 531 of the transfer belt 53 is strongly bent in a direction opposite to the direction in which it is bent by the contact member 54A, that is, in a direction closer to parallel with the rotation axis 511, further increasing the rigidity of the end portion of the transfer belt 53. Regarding this point, all contact members in the second example and beyond are identical, and repeated description is omitted.

[0092] also, Figure 5 The contact member 54B of the second example shown in (B) has a shape obtained by bending a flat plate to form a curved surface. Furthermore, the contact member 54B is arranged so that the portion closest to the center of the transfer belt 53 in the width direction is parallel to the rotation axis 511, and the entire surface of the contact member 54B facing inward is in contact with the transfer belt 53. Figure 5 Similarly to the first example of (A), the transfer belt 53 circulates while sliding against the contact member 54B.

[0093] The contact member 54B of the second example contacts the transfer belt 53 at a plurality of points that are different and continuous in the width direction, including the reference point. Figure 4 The first contact point d1 and the second contact point d2 described in (B) of FIG. This allows the portion of the transfer belt 53 that is in contact with the contact member 54B to be maintained in a target shape.

[0094] Like the contact members 54A and 54B in the first and second examples, the contact member referred to in the present invention may be a member that slides relative to the transfer belt 53 .

[0095] Figure 6 These are diagrams showing the third example (A) and the fourth example (B) of the contact member.

[0096] Figure 6 The contact member 54C of the third example shown in (A) is a roller having two diameters, a large diameter portion 543 and a small diameter portion 544, and freely rotating around a rotation axis 545. Figure 6 As shown in FIG. 5A , the contact member 54C is arranged to press the transfer belt 53 in a direction perpendicular to the rotation axis of the transfer roller 51 via the large diameter portion 543 and to press the transfer belt 53 obliquely inward via the small diameter portion 544 .

[0097] Should Figure 6 The contact member 54C of the third example shown in (A) contacts the transfer belt 53 and rotates freely as the transfer belt 54 moves. Figure 5Compared with the sliding contact members 54A and 54B shown, there is less possibility of hindering the smooth running of the transfer belt 54.

[0098] In addition, similarly to the contact member 54C of the third example, Figure 6 The contact member 54D of the fourth example shown in FIG. (B) is a roller that is rotatable about a rotation axis 545. In the contact member 54D of the fourth example, one end 546a in the direction of the rotation axis 545 has a maximum diameter, the other end 546b has a minimum diameter, and a curved surface that is concave inward and serves as an outer surface is formed between the two ends 546a and 546b.

[0099] The contact member 54D contacts the transfer belt 53 at a plurality of points including the outer surface of the concave surface, that is, at different and continuous positions in the width direction. Figure 4 Thus, similar to the contact member 54B of the second example, the portion of the transfer belt 54 that contacts the contact member 54B can be maintained in a target shape.

[0100] Figure 7 This is a diagram showing a fifth example of the contact member.

[0101] Should Figure 7 The contact member 54E of the fifth example shown is a roller consisting of a large-diameter portion 543 and a small-diameter portion 544. It has a T-shape in a cross-sectional view taken along a plane including a rotation axis 545 and is rotatable about the rotation axis 545. Furthermore, as shown in the figure, the contact member 54E is positioned so that the rotation axis 545 is parallel to the rotation axis 511 of the transfer roller 51. The small-diameter portion 544 presses the transfer belt 53 perpendicularly to the rotation axis 511, while the large-diameter portion 543 presses the transfer belt 53 laterally with its side surface 543a.

[0102] Figure 8 These are diagrams showing the sixth example (A) and the seventh example (B) of the contact member.

[0103] also, Figure 9 The figures show the eighth example (A) and the ninth example (B) of the contact member.

[0104] These Figure 8 、 Figure 9 The contact members 54F, ..., 54J of the sixth to ninth examples shown are rollers rotatable about the rotation axis 545, with the diameter of the center smaller than that of the ends in the direction of the rotation axis 545. Each of these will be described below.

[0105] exist Figure 8In the contact member 54F of the sixth example shown in FIG. 5A , both end portions 546a and 546b in the direction of the rotation axis 545 have a large diameter, and the center portion 547 sandwiched between these end portions 546a and 546b has a small diameter. Figure 8 As shown in FIG. 5A , the contact member 54F presses the transfer belt 53 in a direction perpendicular to the rotation axis of the transfer roller 51 with one end 546 a and presses the transfer belt 53 obliquely inward with the other end 546 b.

[0106] exist Figure 8 In the contact member 54G of the seventh example shown in (B), the diameter of the two end portions 546a, 546b in the direction of the rotation axis 545 is narrowed from the respective end edges 548a, 548b toward the center, so that the contact member 54G has a conical shape, and the central portion 547 sandwiched between these two end portions 546a, 546b is a cylindrical shape with a small diameter. Figure 8 As shown in FIG. 5B , the contact member 54G presses the transfer belt 53 against the transfer roller 51 via one end portion 546 a and presses the transfer belt 53 obliquely inward via the other end portion 546 b .

[0107] exist Figure 9 In the contact member 54H of the eighth example shown in FIG. 5A , the diameter of the contact member 54H decreases as the two end edges 548a and 5468b in the direction of the rotation axis 545 move toward the center, so that the contact member 54H has a conical shape, with the center being the thinnest diameter. Figure 9 As shown in FIG. 5A , the contact member 54H presses the transfer belt 53 against the transfer roller 51 at a portion close to one end edge 548 a and presses the transfer belt 53 obliquely inward at a portion close to the other end edge 548 b.

[0108] Figure 9 The contact member 54J of the ninth example shown in FIG. 5B has an outer peripheral surface 549 formed of a curved surface whose central portion in the direction of the rotation axis 545 is narrowed. Figure 9 As shown in FIG. 5B , the contact member 54J presses the transfer belt 53 over the entire area of its outer peripheral surface 549 in the direction of the rotation axis 545 .

[0109] Such as these Figures 5 to 9 As shown, contact members of various shapes can be adopted as the contact member 54 in this embodiment.

[0110] Next, a description will be given of a bearing in which freely rotatable rollers are used as the contact members 54 .

[0111] Figure 10 Schematic diagram of a roller-shaped contact member and a supporting member supporting the contact member. Figure 9 The contact member 54J shown in (B) of FIG. 1 is similar to the rollers of other shapes. The contact member 54J has an outer peripheral surface 549 composed of a curved surface narrowed in the center.

[0112] Here, a support member 57 for supporting the contact member 54J is shown. The support member 57 is fixed to Figure 2 、 Figure 3 The transfer device support frame 501 is shown. The support member 57 has two arms 571 and 572, and the contact member 54J is rotatably supported on the support member 57 using these arms 571 and 572 as bearings.

[0113] As described above, the extreme end 531 of the transfer belt 53 is bent in a direction parallel to the rotation axis 511 of the transfer roller 51. Therefore, if the arm 572, which is the bearing of the contact member 54J on the side closest to the extreme end 531, moves even slightly, it will come into contact with the extreme end 531 of the transfer belt 53, potentially damaging the transfer belt 53. The arm 572 needs to be shaped to avoid contact with the transfer belt 53.

[0114] Then, return Figure 2 and Figure 3 , the configuration location of the contact component 54 is described.

[0115] The contact member 54 is a member that presses the transfer belt 53 against a member that faces the contact member 54 across the transfer belt 53, and therefore requires a pad member that presses against the back side of the transfer belt 53. Figure 3 As shown in the figure, in this embodiment, the transfer roller 51 is used as a backing member for the contact member 54, as shown by the solid line. Specifically, the transfer roller 51 is a roller that drives the transfer belt 53, that is, a roller that applies tension to the transfer belt 53. This allows for greater force to be overcome when the transfer belt 53 is biased to one side, compared to when the contact member 54' shown by the dotted line is provided on the side of the peeling roller 52, which is a driven roller.

[0116] In addition, Figure 3 In FIG. 5 , the entire contact member 54′ indicated by the dotted line overlaps with the peeling roller 52, but this will be described later. Figure 11 instructions.

[0117] Furthermore, in the case where the contact member 54 is provided on the transfer roller 51 side, as shown in FIG. Figure 2 As shown, the contact member 54 is preferably arranged at a position where the transfer belt 53 contacts the transfer roller 51 in the circular moving direction of the transfer belt 53. Figure 2 More specifically, in this embodiment, the most downstream position in the left half of the area shown is not arranged near the most upstream position. Figure 25. The contact member 54 is shown at the most downstream side, but is arranged near the most upstream position. This is because the tension of the transfer belt 53 at the most upstream side is relatively high, and arranging the contact member 54 at the portion of the transfer belt 53 where the tension is relatively high can better overcome the larger force that causes the transfer belt 53 to deflect to one side.

[0118] Figure 11 This is a diagram showing an example of experimental data.

[0119] The vertical axis is the inclination angle of the rotation axis 521 of the peeling roller 52 relative to the rotation axis 511 of the transfer roller 51. In addition, the horizontal axis (A) is the case where no contact member is provided, and (B) and (C) are the cases where a contact member is provided. Figure 4 (A) shows a cylindrical roller with a uniform diameter in the direction of the rotating shaft 591, (D) and (E) are provided with Figure 8 The roller shown in (D) has an outer peripheral surface 549 formed by a curved surface whose central portion in the direction of the rotation axis 545 is narrowed. Here, (B) and (D) are Figure 2 、 Figure 3 In the case where the contact member 54' is provided on the side of the peeling roller 52, (C) and (E) are Figure 2 、 Figure 3 In the case where the contact member 54 is indicated by a solid line in FIG. 5 , the contact member 54 is arranged on the transfer roller 51 side. When the contact member 54 'is arranged on the peeling roller 52 side, the contact member 54 is arranged on the peeling roller 52 side. Figure 3 The lengths L1 and L2 shown are opposite, that is, a transfer roller with a length of L2 and a peeling roller with a length of L1 are used. Figure 3 The positional relationship of the contact member 54' indicated by the dotted line relative to the peeling roller 52 is the same as Figure 3 The positional relationship of the contact member 54 indicated by the solid line with respect to the transfer roller 51 is the same.

[0120] In this Figure 11 Among them, (A) to (C) correspond to comparative examples, and (D) and (E) correspond to examples.

[0121] If the Figure 11 As shown, when a roller having an outer peripheral surface 549 formed of a curved surface with a narrowed center portion in the direction of the rotation axis 545 is provided, it is possible to overcome the lateral deviation of the transfer belt 53 even when the rotation axis 521 of the peeling roller 52 is tilted at a large angle. Furthermore, a comparison of (D) and (E) shows that providing a roller on the side of the transfer roller 51 (driving roller) is more effective in dealing with lateral deviations with a large angle than providing a roller on the side of the peeling roller 52 (driven roller).

[0122] here, Figures 5 to 9Various shapes of contact members 54A, ..., 54H are shown, but the contact members in the present invention are not limited to these shapes. Figure 4 As shown in (B), a contact component only needs to have at least a first contact point that contacts the transfer belt and presses the transfer belt against the transfer roller or the peeling roller, and a second contact point that contacts the transfer belt at a side closer to the width end of the transfer belt 53 than the first contact point. At the second contact point, the contact component contacts the transfer belt at a larger angle to the rotation axis of the transfer roller or the peeling roller than at the first contact point.

[0123] Furthermore, in the above embodiments, an electrophotographic image forming apparatus is used as an example. However, the present invention can also be applied to transfer devices and image forming apparatuses other than electrophotographic ones. For example, it can also be applied to inkjet image forming apparatuses. Specifically, it can also be applied to image forming apparatuses that use an inkjet head to draw an ink image on an intermediate transfer body and transfer the ink image from the intermediate transfer body to paper. Furthermore, it can also be applied to image forming apparatuses of other types, as long as they transfer an image onto a recording material.

[0124] Furthermore, in an image forming apparatus, the present invention can also be applied to belt members other than the transfer belt, for example, a conveying device between a transfer device and a fixing device.

[0125] Furthermore, the present invention can also be applied to belt members other than image forming apparatuses.

Claims

1. A belt drive device comprising: annular belt member; a rotating member that stretches over the belt member and rotates about an axis extending in the width direction of the belt member; as well as a rotating contact member that contacts the belt member and suppresses deviation of the belt member in the width direction; The rotation contact member is arranged at a position spanning a first portion of the belt member and a second portion of the belt member, the first portion of the belt member extending parallel to the rotation axis direction of the rotation member, and the second portion of the belt member being located outside the first portion in the width direction of the belt member and curved toward the rotation axis of the rotation member. The rotating contact member has at least: a first contact point that contacts the first portion of the belt member and presses the belt member against the rotating member; and a second contact point that contacts the second portion of the belt member closer to the widthwise end than the first contact point, wherein the rotational contact member has a larger angle with the rotation axis at the second contact point than at the first contact point.

2. The belt drive device according to claim 1, wherein The rotary contact member is a rotating contact member that rotates around its rotation axis, and the rotating contact member has portions having different diameters in the direction of the rotation axis.

3. The belt drive device according to claim 2, wherein: The diameter of the rotary contact member at the center in the direction of the rotation axis of the rotary contact member is smaller than the diameters at both ends.

4. The belt drive device according to claim 3, wherein: The rotary contact member has an outer peripheral surface formed of a curved surface that is narrowed at the center in the direction of the rotation axis of the rotary contact member.

5. The belt drive device according to any one of claims 2 to 4, wherein A bearing supporting the rotating shaft of the rotating contact member has a shape that avoids contact with the belt member.

6. The belt drive device according to any one of claims 1 to 4, wherein: The rotating member is a rotation driving member that drives the belt member to cause the belt member to circulate.

7. The belt drive device according to claim 6, wherein: The rotation contact member is arranged at a position closer to the most upstream position than the most downstream position in the region where the belt member contacts the rotation member in the circulating direction of the belt member.

8. The belt drive device according to any one of claims 1 to 4, wherein: The length of the portion of the second rotating member that stretches the belt member together with the rotating member and that contacts the belt member in the width direction is longer than the length of the portion of the rotating member that contacts the belt member in the width direction.

9. A transfer device comprising: an endless belt member, the outer peripheral surface of which is in contact with a recording material and transfers an image to the recording material by applying a voltage thereto; a rotating member that stretches over the belt member and rotates about an axis extending in the width direction of the belt member; as well as a rotating contact member that contacts the belt member and suppresses deviation of the belt member in the width direction; The rotation contact member is arranged at a position spanning a first portion of the belt member and a second portion of the belt member, the first portion of the belt member extending parallel to the rotation axis direction of the rotation member, and the second portion of the belt member being located outside the first portion in the width direction of the belt member and curved toward the rotation axis of the rotation member. The rotating contact member has at least: a first contact point that contacts the first portion of the belt member and presses the belt member against the rotating member; and a second contact point that contacts the second portion of the belt member closer to the widthwise end than the first contact point, wherein the rotational contact member has a larger angle with the rotation axis at the second contact point than at the first contact point.

10. An image forming apparatus comprising: a conveying portion that conveys a recording material; an image forming section that forms a toner image; and The transfer device according to claim 9 transfers the toner image formed by the image forming section onto the recording material conveyed by the conveying section.

Images