JP2013186437A - Belt driving device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable correction of meandering of an endless belt smoothly and stably with a simple mechanism.SOLUTION: In an intermediate transfer unit 50, an intermediate transfer belt tension roller 54 is arranged at a position nearer to an intermediate transfer belt driven roller 53 than an intermediate transfer belt driving roller 52. Sliding members 24A and 24B are externally inserted into a shaft member 21 and loosely fitted in through holes 271A and 271B and are freely slidable in the shaft direction 101. Sliding members 24A and 24B have inclined parts 242A and 242B inclining to a direction where the inclined parts are separated wider from the intermediate transfer belt tension roller 54 along the shaft direction 101, the distance from the shaft member 21 becomes shorter.

Description

  The present invention relates to a belt driving device that rotates an endless belt stretched around a plurality of stretch rollers, and an image forming apparatus including the belt drive device.

  For example, some electrophotographic image forming apparatuses include an endless belt such as an intermediate transfer belt, a secondary transfer belt, and a fixing belt. As a belt driving device for rotating such an endless belt, a plurality of stretching rollers arranged in parallel to each other for stretching the endless belt are provided, and the driving roller of the stretching rollers is driven to rotate the endless belt. What is to be known is known. The endless belt causes meandering due to variations in the outer diameter of the tension roller due to manufacturing errors, deviations in parallelism between the tension rollers due to mounting errors, and the like. Particularly in an image forming apparatus, meandering of an endless belt adversely affects image quality, so it is important to suppress the meandering of an endless belt as much as possible.

  As a technique for suppressing the meandering of the endless belt, an electric control system is known in which a deviation amount of the endless belt is detected by a sensor and a meandering correction roller is moved in accordance with a detection signal. However, the electric control method requires a sensor, an electric circuit, a drive motor, and the like, and there is a problem that the configuration becomes complicated due to an increase in the number of parts and the cost increases.

  Therefore, a technique is known that attempts to suppress meandering of the endless belt by adjusting the tension of the endless belt using a mechanical mechanism (see, for example, Patent Document 1).

  In the conventional belt driving device described in Patent Document 1, the tension roller is pivotally supported by the arm member. The arm member is rotatable along the traveling direction of the endless belt, and is biased to the downstream side in the traveling direction of the endless belt by a spring. Belt contact portions are provided on both ends of the tension roller. When the endless belt meanders, the endless belt comes into contact with the belt contact portion. As the contact width between the endless belt and the belt contact portion increases, the frictional force received by the belt contact portion increases. Therefore, the tension roller rotates by this frictional force and the biasing force of the spring, and the tension of the endless belt is increased. Is intended to increase.

JP-A-2005-162466

  However, in the conventional belt driving device described in Patent Document 1, the rotational direction of the arm member for increasing the tension of the endless belt is the same as the traveling direction of the endless belt, and therefore the amount of deviation of the endless belt is large. When the friction force received by the belt contact portion increases, the endless belt traveling force causes the arm member to fall over the top and fall downstream in the traveling direction of the endless belt, and the tension applied to the endless belt by the tension roller is extreme. The tension of the endless belt may not be adjusted. In order to prevent the arm member from exceeding the top, various settings such as the strength of the spring, the length and the mass of the arm member are difficult, and it is difficult to stably correct the meandering of the endless belt. It is also difficult to improve the meandering correction efficiency.

  An object of the present invention is to provide a belt driving device capable of correcting the meandering of an endless belt stably and efficiently with a simple mechanism, and an image forming apparatus including the belt driving device.

  The belt drive device of the present invention includes an endless belt that does not have elasticity, a plurality of stretching rollers, a shaft member, a through-hole holding member, an offset transmission member, and an urging member. The tension roller includes a first tension roller and a second tension roller that stretch an endless belt between each other, and a first tension roller between the first tension roller and the second tension roller. And a tension roller that presses the inner peripheral surface of the endless belt at a position closer to the second tension roller. The shaft member rotatably supports the tension roller. The through hole holding member has through holes through which both end portions of the shaft member are inserted. The offset transmission member is externally inserted into the shaft member so as to be adjacent to both end portions in the axial direction of the tension roller, and is loosely fitted into the through hole. The offset transmission member arranged at least downstream in the offset direction along the axial direction of the endless belt moves in the offset direction along with the offset of the endless belt. The urging member has an elastic force that urges the shaft member in a tension increasing direction in which the tension of the endless belt is increased, the working end is pivotally supported by the offset transmission member, and the base end acts in the axial direction. It is pivotally supported at a predetermined position on the opposite side of the tension roller with respect to the end portion. The offset transmission member is inserted into the through-holes so as to be movable in at least two different directions in the interval changing direction in which the interval between the shaft member and the first stretching roller is changed, and the tension increasing direction. The offset transmission member disposed at least on the downstream side in the offset direction is inclined in a direction in which the distance from the shaft member decreases as the distance from the tension roller increases in the axial direction at a portion facing the first stretching roller. It has an inclined part.

  In this configuration, both end portions of the shaft member are movable independently of each other in at least two directions different from each other in the tension increasing direction and the interval changing direction in the through hole.

  The urging member inclines in a direction approaching the offset transmission member as it goes from the end side to the center side in the axial direction of the tension roller. When the endless belt meanders and shifts to one side in the axial direction of the tension roller, at least the downstream transmission member in the offset direction moves along the axial direction of the tension roller. As a result, the inclination angle of the biasing member on the downstream side in the offset direction approaches perpendicular to the axial direction of the tension roller, and the degree of contraction of the biasing member increases. For this reason, on the downstream side of the endless belt in the axial direction of the tension roller, the pressing force of the urging member against the offset transmission member increases, the shaft member moves downstream in the direction of increasing tension, and the endless belt Tension increases. An endless belt that does not have stretchability has a property of moving along the axial direction from a stronger tension to a weaker tension. For this reason, the meandering of the endless belt is corrected by the movement of the shaft member along the tension increasing direction.

  Further, since the tension roller presses the inner peripheral surface of the endless belt at a position closer to the second tension roller than the first tension roller, the tension roller approaches the first tension roller by the tension of the endless belt. Directional force is added. For this reason, when the endless belt meanders and shifts to one side in the axial direction of the tension roller, the first shift transmission member receives the shift force from the tension roller and moves to the downstream side in the shift direction. An inclined portion provided at a portion facing the tension roller moves to the downstream side in the offset direction while sliding with the edge of the through hole. Since the inclined portion is inclined in such a direction that the distance from the shaft member becomes shorter as it is separated from the tension roller, when the offset transmission member moves to the downstream side in the offset direction, the axis member on the downstream side in the offset direction. Moves in a direction away from the first stretching roller in the interval changing direction. The endless belt that does not have stretchability has a property of moving along the axial direction from the larger one to the smaller one with respect to the one having the larger interval between the first and second stretching rollers. Have For this reason, the meandering of the endless belt is corrected by the shaft member moving along the interval changing direction.

  Thus, the meandering of the endless belt is efficiently corrected by moving the shaft member in the two directions of the tension increasing direction and the interval changing direction.

  Further, a meandering amount of the endless belt is corrected by a simple mechanism without requiring a sensor or an electric circuit for detecting a deviation amount of the endless belt.

  Further, since the rotation direction around the base end portion of the urging member is different from the traveling direction of the endless belt, the urging member is rotated by the running force of the endless belt even if the deviation amount of the endless belt is increased. There is nothing. Therefore, the tension applied to the endless belt by the tension roller does not become extremely weak against the intention. For this reason, the meandering of the endless belt can be corrected stably.

  In the above-described configuration, the offset transmission member has a diameter-enlarged portion that is larger than the tension roller and is adjacent to both end portions of the tension roller in the axial direction, and the diameter-enlarged member in the axial direction. The sliding member includes a sliding member adjacent to the diameter-expanding member on the opposite side of the tension roller, and the sliding member is configured such that rotation about the shaft member is restricted, and the inclined portion is provided on the sliding member. it can.

  In this configuration, when the endless belt is shifted, the endless belt pushes the diameter-expanded portion, so that the diameter-expanding member moves in the axial direction. When the diameter-expanding member moves in the axial direction, a sliding force is transmitted from the diameter-expanding member, so that the sliding member also moves in the axial direction. Since the sliding member is restricted from rotating about the shaft member, the inclined portion is surely directed in the direction facing the first stretching roller. For this reason, the shaft member reliably moves in the interval changing direction along with the deviation of the endless belt, and the meandering of the endless belt is corrected. In addition, since the working end of the urging member is pivotally supported by the sliding member whose rotation is restricted, the arrangement and contraction degree of the urging member is stable when the deviation amount of the endless belt is a certain value. In addition, the tension of the endless belt is stabilized.

  Moreover, it is preferable that a through-hole holding member has a guide member which guides, sliding an inclined part in the edge part which opposes an inclined part among through-holes.

  In this configuration, when the endless belt meanders, the inclined portion slides with the guide member. By providing a member that slides on the inclined portion separately from the through-hole holding member, it becomes easy to select a material and process the contact surface so that the frictional force between the inclined portion and the inclined portion is reduced.

  Further, the offset transmission member arranged on the upstream side in the offset direction moves in the offset direction along with the offset of the endless belt, and both offset transmission members at both ends of the tension roller in the axial direction are When the far end of the inclined transmission member on the downstream side in the offset direction has a slope and the far end far from the tension roller contacts the edge of the through hole, the upstream piece in the offset direction It can comprise so that it may be comprised so that the near end part of a side near a tension roller may contact | abut the edge part of a through-hole among the inclination parts of a deviation transmission member.

  In this configuration, when the endless belt is offset in the axial direction, the portion that contacts the edge of the through hole is shifted from the far end of the inclined portion to the near end on the downstream side in the offset direction. Since the near end is larger than the far end than the far end, the shaft moves in a direction away from the first stretching roller in the interval changing direction. Further, on the upstream side in the offset direction, the portion that contacts the edge of the through hole shifts from the near end of the inclined portion to the far end. Since the distance from the shaft member is smaller at the far end than at the far end, the shaft moves in a direction approaching the first tension roller in the interval changing direction. For this reason, since the inclination of the shaft member with respect to the first stretching roller accompanying the meandering of the endless belt is larger than the case where the inclined portion is provided only in one axial transmission member, the endless belt The speed of correcting the meandering can be improved.

  The image forming apparatus according to the present invention includes the belt driving device having any one of the above-described configurations. In this configuration, the meandering of the endless belt is efficiently corrected by moving the shaft member in the two directions of the tension increasing direction and the interval changing direction.

  According to the present invention, meandering of the endless belt in the belt driving device can be corrected stably and efficiently with a simple mechanism.

1 is a front sectional view showing a schematic configuration of an image forming apparatus including an intermediate transfer unit according to an embodiment of a belt driving device of the present invention. 2 is an enlarged view of a part of the image forming apparatus. FIG. FIG. 3 is a side sectional view of a part of the intermediate transfer unit. FIG. 4 is a diagram illustrating a state where an intermediate transfer belt is offset toward the back side. FIG. 4 is a diagram illustrating a state where an intermediate transfer belt is offset toward the front side. 2 is a schematic front sectional view of an intermediate transfer unit. FIG. FIG. 3 is a plan sectional view of a part of the intermediate transfer unit in a state where the intermediate transfer belt is shifted to the back side. It is an enlarged plan view of a sliding member. FIG. 3 is a plan view of the intermediate transfer unit in a state where the intermediate transfer belt is shifted to the back side. FIG. 3 is a plan sectional view of a part of the intermediate transfer unit in a state where the intermediate transfer belt is shifted to the front side. FIG. 4 is a plan view of the intermediate transfer unit in a state where the intermediate transfer belt is shifted to the front side. It is a perspective view which shows the modification of a sliding member.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, an image forming apparatus 100 including an intermediate transfer unit 50 according to an embodiment of a belt driving device of the present invention uses a sheet of paper based on image data generated from a document or image data input from the outside. A single color or multicolor image is formed. Examples of the paper include recording media such as plain paper, photographic paper, and OHP film.

  The image forming apparatus 100 includes an image reading unit 120, an image forming unit 110, a paper feed unit 80, and a paper discharge unit 90.

  The image reading unit 120 reads an image of a document, generates image data, and supplies the image data to the image forming unit 110.

  The image forming unit 110 includes an exposure unit 3, four image forming stations 31, 32, 33, 34, an intermediate transfer unit 50, a secondary transfer unit 60, and a fixing device 70, and performs image forming processing on a sheet.

  The intermediate transfer unit 50 includes an intermediate transfer belt 51, an intermediate transfer belt drive roller 52, an intermediate transfer belt driven roller 53, and an intermediate transfer belt tension roller 54. The intermediate transfer belt drive roller 52, the intermediate transfer belt driven roller 53, and the intermediate transfer belt tension roller 54 are arranged in parallel to each other. As the intermediate transfer belt 51, a resin film having no stretchability such as polyimide is used. The intermediate transfer belt 51 is an endless belt, and is stretched between the intermediate transfer belt driving roller 52 and the intermediate transfer belt driven roller 53 to form a loop-shaped movement path.

  The intermediate transfer belt tension roller 54 is located between the intermediate transfer belt drive roller 52 and the intermediate transfer belt driven roller 53 and closer to the intermediate transfer belt driven roller 53 than the intermediate transfer belt drive roller 52. The inner peripheral surface is pressed. The tension of the intermediate transfer belt 51 can be changed by the intermediate transfer belt tension roller 54. The intermediate transfer belt drive roller 52 is a first tension roller that stretches the intermediate transfer belt 51, the intermediate transfer belt driven roller 53 is a second tension roller, and the intermediate transfer belt tension roller 54 also moves the intermediate transfer belt 51. This is one of the tension rollers that stretch.

  Based on the image data, the image forming unit 110 forms an image of black and toner images of four hues of cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of a color image. Formed at stations 31-34. The image forming stations 31 to 34 are arranged in a line along the movement path of the intermediate transfer belt 51. The image forming stations 32 to 34 are configured in substantially the same manner as the image forming station 31.

  The black image forming station 31 includes a photosensitive drum 1, a charger 2, a developing device 4, an intermediate transfer roller 5, and a cleaner unit 6.

  The photosensitive drum 1 is an electrostatic latent image carrier, and rotates in a predetermined direction when a driving force is transmitted from a driving source (not shown). The charger 2 charges the peripheral surface of the photosensitive drum 1 to a predetermined potential.

  The exposure unit 3 irradiates the respective photosensitive drums 1 of the image forming stations 31 to 34 with laser beams modulated by image data of hues of black, cyan, magenta, and yellow. On the peripheral surfaces of the four photosensitive drums 1, electrostatic latent images based on image data of each hue of black, cyan, magenta, and yellow are formed.

  The developing device 4 supplies black toner, which is the hue of the image forming station 31, to the peripheral surface of the photosensitive drum 1, and visualizes the electrostatic latent image into a toner image.

  The outer peripheral surface of the intermediate transfer belt 51 faces the four photosensitive drums 1 in order. An intermediate transfer roller 5 is disposed at a position facing the photosensitive drum 1 with the intermediate transfer belt 51 interposed therebetween. Each of the positions where the intermediate transfer belt 51 and the photosensitive drum 1 face each other is a primary transfer position.

  A primary transfer bias is applied to the intermediate transfer roller 5 by constant voltage control with a toner charging polarity (for example, minus) and a reverse polarity (for example, plus). The same applies to the image forming stations 32-34. As a result, the toner images of the respective colors formed on the respective photosensitive drums 1 are sequentially transferred to the outer peripheral surface of the intermediate transfer belt 51 to be primarily transferred, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 51. .

  However, when image data of only a part of the hues of black, cyan, magenta, and yellow is input, only the part of the four photosensitive drums 1 corresponding to the hue of the input image data is static. An electrostatic latent image and a toner image are formed, and only a partial toner image is primarily transferred onto the outer peripheral surface of the intermediate transfer belt 51.

  The cleaner unit 6 collects the toner remaining on the peripheral surface of the photosensitive drum 1 after the primary transfer.

  The toner image primarily transferred to the outer peripheral surface of the intermediate transfer belt 51 at each primary transfer position is rotated by the intermediate transfer belt 51 and the secondary transfer belt 61 provided in the secondary transfer unit 60 and the intermediate transfer belt 51. Is conveyed to a secondary transfer position which is a position opposite to.

  The paper feed unit 80 includes a paper feed cassette 81, a manual feed tray 82, a first paper transport path 83, and a second paper transport path 84. Paper is stored in each of the paper feed cassette 81 and the manual feed tray 82. The first paper transport path 83 is formed so as to reach the paper discharge unit 90 from each of the paper feed cassette 81 and the manual feed tray 82 via the secondary transfer position and the fixing device 70. The second paper conveyance path 84 is a paper conveyance path for double-sided printing, and is formed so that the paper on which an image is formed on one side is conveyed again to the secondary transfer position with the front and back sides reversed. Yes.

  The secondary transfer unit 60 includes a secondary transfer roller 62 in addition to the secondary transfer belt 61. The secondary transfer roller 62 is in pressure contact with the intermediate transfer belt driving roller 52 with a predetermined nip pressure across the secondary transfer belt 61 and the intermediate transfer belt 51. In order to maintain the nip pressure between the secondary transfer roller 62 and the intermediate transfer belt 51 at a predetermined value, either the secondary transfer roller 62 or the intermediate transfer belt drive roller 52 is made of a hard material (for example, metal or resin). The other is made of a soft material (for example, elastic rubber or foamable resin).

  When the sheet passes through the secondary transfer position, a secondary transfer bias having a toner charging polarity (for example, minus) and a reverse polarity (for example, plus) is applied to the secondary transfer roller 62 by constant voltage control. Thus, the toner image carried on the outer peripheral surface of the intermediate transfer belt 51 is secondarily transferred to the paper.

  The toner remaining on the intermediate transfer belt 51 after the toner image is transferred to the paper is collected by the intermediate transfer belt cleaning unit 55.

  The sheet on which the toner image is transferred is sent to the fixing device 70. The fixing device 70 includes a fixing roller 71 and a pressure roller 72. The fixing device 70 performs a fixing process for firmly fixing the toner image on the paper by heating and pressurizing the paper by rotating the paper between the fixing roller 71 and the pressure roller 72.

  The paper discharge unit 90 includes a paper discharge tray 91 and a paper discharge roller 92. The sheet on which the toner image has been fixed is discharged to a discharge tray 91 by a discharge roller 92. The paper is stored in the paper discharge tray 91 with the surface on which the toner image is fixed facing down.

  As shown in FIG. 2, the black image forming station 31 disposed on the most downstream side of the image forming stations 31 to 34 in the traveling direction of the intermediate transfer belt 51 in the region facing the image forming stations 31 to 34. A pre-transfer charger (PTC) 56 is disposed between the intermediate transfer belt driving roller 52 and the transfer roller. The pre-transfer charger 56 faces the outer peripheral surface of the intermediate transfer belt 51. A counter roller 57 is disposed so as to face the pre-transfer charger 56 with the intermediate transfer belt 51 interposed therebetween. The pre-transfer charger 56 adjusts the charge amount of the toner constituting the toner image carried on the outer peripheral surface of the intermediate transfer belt 51 before the secondary transfer. This improves the image quality of the toner image transferred to the paper.

  The secondary transfer unit 60 includes a secondary transfer belt driving roller 63, a secondary transfer belt driven roller 64, and a secondary transfer belt tension roller 65 in addition to the secondary transfer belt 61 and the secondary transfer roller 62. The secondary transfer belt 61 is an endless belt. As the secondary transfer belt 61, a rubber material having elasticity is used.

  Each of the secondary transfer roller 62, the secondary transfer belt drive roller 63, the secondary transfer belt driven roller 64, and the secondary transfer belt tension roller 65 is a tension roller that stretches the secondary transfer belt 61. The tension of the secondary transfer belt 61 can be changed by the secondary transfer belt tension roller 65.

  As shown in FIGS. 3 to 5, the intermediate transfer belt tension roller 54 that stretches the intermediate transfer belt 51 is rotatable about the shaft member 21 and slidable along the shaft member 21 in the axial direction 101. The shaft member 21 is supported. The shaft member 21 is restricted from rotating. The shaft member 21 has a uniform perfect circular cross-sectional shape in the axial direction 101.

  As an example, in FIG. 3, the left side is the front surface F side of the image forming apparatus 100, and the right side is the back surface R side of the image forming apparatus 100.

  In the axial direction 101 of the intermediate transfer belt tension roller 54, diameter expanding members 23A and 23B are arranged so as to be adjacent to both ends of the intermediate transfer belt tension roller 54, respectively. Each of the diameter-expanding members 23A and 23B has a diameter-expanded portion whose diameter is larger than that of the intermediate transfer belt tension roller 54 at the end far from the intermediate transfer belt tension roller 54 in the axial direction 101. Yes. The portions other than the enlarged diameter portion in the axial direction 101 of each of the enlarged diameter members 23A and 23B are formed to have the same diameter as the intermediate transfer belt tension roller 54. The diameter-expanding members 23A and 23B are extrapolated by the shaft member 21 and are movable in the axial direction 101, and are supported by the shaft member 21 so as to be rotatable.

  In the axial direction 101, a sliding member 24A is disposed on the opposite side of the intermediate transfer belt tension roller 54 with respect to the diameter expanding member 23A. A sliding member 24B is disposed on the opposite side of the intermediate transfer belt tension roller 54 with respect to the diameter expanding member 23B in the axial direction 101. The sliding members 24A and 24B are passed through the shaft member 21 so as to be adjacent to the diameter-expanding members 23A and 23B in the axial direction 101, and are movable in the axial direction 101. The sliding members 24A and 24B are restricted from rotating around the shaft member 21. The enlarged diameter member 23A and the sliding member 24A constitute one offset transmission member 25A, and the enlarged diameter member 23B and the sliding member 24B constitute the other offset transmission member 25B.

  The sliding member 24A is inserted through the through hole 221A of the device frame 22A and the through hole 271A of the through hole holding member 27A. The through-hole holding member 27A is disposed on the opposite side of the intermediate transfer belt tension roller 54 with respect to the apparatus frame 22A and is supported by the apparatus frame 22A.

  The sliding member 24B is inserted through the through hole 221B of the device frame 22B and the through hole 271B of the through hole holding member 27B. The through-hole holding member 27B is disposed on the opposite side of the intermediate transfer belt tension roller 54 with respect to the apparatus frame 22B and is supported by the apparatus frame 22B.

  The sliding members 24A and 24B are at least two different from each other in the tension increasing direction 102 in which the tension of the intermediate transfer belt 51 is increased and the interval changing direction 103 in which the interval of the shaft member 21 with respect to the intermediate transfer belt driving roller 52 is changed. The through holes 271 </ b> A and 271 </ b> B are respectively inserted so as to be movable in the direction. As a result, both end portions of the shaft member 21 can also move independently of each other in at least two different directions of the tension increasing direction 102 and the interval changing direction 103.

  The through hole 221A of the apparatus frame 22A is formed to be larger than the through hole 271A so as to face all the edges of the through hole 271A from the intermediate transfer belt tension roller 54. Similarly, the through hole 221B is formed larger than the through hole 271B.

  The intermediate transfer unit 50 further includes urging members 26A and 26B.

  The biasing member 26A includes a first bracket 261A, a second bracket 262A, a mandrel 263A, and an elastic member 264A. The first bracket 261A is pivotally supported by the sliding member 24A. The second bracket 262A is pivotally supported by the through-hole holding member 27A at a predetermined position opposite to the intermediate transfer belt tension roller 54 with respect to the pivot point of the first bracket 261A. That is, the base end portion of the urging member 26A is pivotally supported by the through-hole holding member 27A at a predetermined position on the opposite side of the intermediate transfer belt tension roller 54 with respect to the working end portion.

  The mandrel 263A has one end fixed to one of the first bracket 261A and the second bracket 262A, and is inserted through the other bracket so as to be displaceable. As an example, the mandrel 263A has one end fixed to the second bracket 262A and is inserted through the first bracket 261A so as to be displaceable. The elastic member 264A is disposed between the first bracket 261A and the second bracket 262A. Since the elastic member 264A expands and contracts along the mandrel 263A, the direction of the elastic force does not distort even if the degree of contraction increases.

  The urging member 26B includes a first bracket 261B, a second bracket 262B, a mandrel 263B, and an elastic member 264B, and is configured in the same manner as the urging member 26A. The first bracket 261B is pivotally supported by the sliding member 24B. The second bracket 262B is pivotally supported by the through-hole holding member 27B at a predetermined position opposite to the intermediate transfer belt tension roller 54 with respect to the pivot point of the first bracket 261B.

  In other words, the shaft fulcrum of the second brackets 262A and 262B is disposed closer to the end of the shaft member 21 than the shaft fulcrum of the first brackets 261A and 261B in the axial direction 101.

  As described above, the urging member 26A is disposed so as to be inclined toward the sliding member 24A in the axial direction 101 of the intermediate transfer belt tension roller 54 from the end side toward the center side. The urging member 26 </ b> B is disposed so as to be inclined toward the sliding member 24 </ b> B as it goes from the end side to the center side in the axial direction 101 of the intermediate transfer belt tension roller 54.

  The shaft fulcrums of the second brackets 262A and 262B are disposed on the opposite side of the intermediate transfer belt 51 with respect to the shaft member 21. Therefore, the urging members 26 </ b> A and 26 </ b> B urge the shaft member 21 in a direction in which the tension of the intermediate transfer belt 51 is increased.

  FIG. 4 shows a state in which the intermediate transfer belt 51 is displaced from the ideal position in the width direction to be traveled, that is, a meander is caused. When the intermediate transfer belt 51 meanders and shifts to one side in the axial direction 101, for example, the back surface R side, the end in the width direction of the intermediate transfer belt 51 pushes the diameter-enlarged portion of the diameter-expanding member 23B. Is transmitted to the diameter expanding member 23B. The offset force is also transmitted from the diameter-expanding member 23B to the sliding member 24B. In this way, as the intermediate transfer belt 51 is displaced toward the back surface R, the displacement transmission member 25B on the downstream side in the displacement direction moves along the shaft member 21 toward the back surface R side.

  As a result, the inclination angle of the biasing member 26B on the downstream side in the offset direction with respect to the axial direction 101 approaches perpendicular to the axial direction 101, and the degree of contraction of the biasing member 26B increases. For this reason, the pressing force of the urging member 26B against the shaft member 21 is increased on the downstream side of the intermediate transfer belt 51 in the axial direction 101 in the axial direction 101 of the intermediate transfer belt tension roller 54, that is, the back surface R side. Tension increases.

  Further, the offset transmission member 25 </ b> A arranged on the upstream side in the offset direction moves downstream in the offset direction by the elastic force of the biasing member 26 </ b> A along with the offset of the intermediate transfer belt 51. Thereby, the inclination angle of the biasing member 26A on the upstream side in the offset direction with respect to the axial direction 101 approaches parallel to the axial direction 101, and the degree of contraction of the biasing member 26A becomes small. For this reason, on the upstream side in the offset direction of the intermediate transfer belt 51 in the axial direction 101, the pressing force of the biasing member 26A against the offset transmission member 25A becomes small, and the tension of the intermediate transfer belt 51 becomes weak.

  Since the endless belt that does not have elasticity has a property of moving from a stronger tension to a weaker tension, the intermediate transfer belt 51 moves to the front surface F side. As a result, meandering of the intermediate transfer belt 51 toward the back surface R is corrected.

  FIG. 5 shows a state where the intermediate transfer belt 51 meanders to the front surface F side. Also in this case, as in the case shown in FIG. 4, when the intermediate transfer belt 51 meanders and shifts to the front surface F side, the end in the width direction of the intermediate transfer belt 51 pushes the enlarged diameter portion of the enlarged diameter member 23A. Accordingly, the offset transmission member 25A on the downstream side in the offset direction, that is, on the front surface F side, moves along the shaft member 21 to the front surface F side. Accordingly, the degree of contraction of the biasing member 26A on the downstream side in the offset direction is increased, and the tension of the intermediate transfer belt 51 on the front surface F side is increased. Further, the tension of the intermediate transfer belt 51 becomes weak on the upstream side in the offset direction, that is, on the back surface R side. Therefore, the intermediate transfer belt 51 moves to the back surface R side. As a result, meandering of the intermediate transfer belt 51 toward the front surface F is corrected.

  In this manner, the intermediate transfer belt 51 meanders and pushes the enlarged diameter portions of the enlarged diameter members 23A and 23B, so that both end portions of the shaft member 21 move along the tension increasing direction 102, and the downstream side in the offset direction. Since the tension of the intermediate transfer belt 51 is increased and the tension on the upstream side is weakened, the force to move to the front F side and the force to move to the rear R side of the intermediate transfer belt 51 is balanced. The position in the width direction of the intermediate transfer belt 51 is maintained at the position.

  Further, a meandering amount of the intermediate transfer belt 51 is corrected by a simple mechanism without requiring a sensor or an electric circuit for detecting the amount of deviation of the intermediate transfer belt 51.

  Further, the urging member 26A is in pressure contact with the intermediate transfer belt tension roller 54 and the rotation direction of the urging member 26A around the shaft fulcrum of the second bracket 262A and the rotation direction of the urging member 26B around the fulcrum of the second bracket 262B. Since the traveling direction of the partial intermediate transfer belt 51 is different, the urging members 26 </ b> A and 26 </ b> B are not rotated by the traveling force of the intermediate transfer belt 51 even when the amount of deviation of the intermediate transfer belt 51 increases. Therefore, the tension applied to the intermediate transfer belt 51 by the intermediate transfer belt tension roller 54 does not become excessively weak. For this reason, the meandering of the intermediate transfer belt 51 can be corrected stably.

  The surface including the locus of rotation around the base end of each of the urging members 26A and 26B and the traveling direction of the intermediate transfer belt 51 at the portion in pressure contact with the intermediate transfer belt tension roller 54 are orthogonal to each other. Is preferred. As a result, even if the deviation amount of the intermediate transfer belt 51 is increased, the biasing members 26A and 26B are more reliably prevented from rotating by the running force of the intermediate transfer belt 51. For this reason, the meandering of the intermediate transfer belt 51 can be corrected more stably.

  Further, since the diameter expanding members 23A and 23B are rotatable, friction between the intermediate transfer belt 51 and the diameter expanding members 23A and 23B is reduced, and wear at both ends of the intermediate transfer belt 51 is reduced.

  Further, since the working end portions of the urging members 26A and 26B are pivotally supported by the sliding members 24A and 24B whose rotation about the shaft member 21 is restricted, there is a certain amount of deviation of the intermediate transfer belt 51. In this case, the arrangement and the degree of contraction of the urging members 26A and 26B are stabilized, and the accuracy of the meandering correction of the intermediate transfer belt 51 is further improved.

  Further, since the base end portions of the biasing members 26A and 26B are pivotally supported by the through hole holding members 27A and 27B, the base end portions of the biasing members 26A and 26B are pivoted separately from the through hole holding members 27A and 27B. Since there is no need to provide a supporting member, the number of parts can be reduced.

  In the intermediate transfer unit 50, in addition to moving the shaft member 21 along the tension increasing direction 102 along with the offset of the intermediate transfer belt 51, the intermediate transfer belt 50 can also be moved along the interval changing direction 103. 51 meandering can be corrected. A specific configuration will be described below.

  As shown in FIG. 6, the intermediate transfer belt tension roller 54 is between the intermediate transfer belt drive roller 52 and the intermediate transfer belt driven roller 53 and is closer to the intermediate transfer belt driven roller 53 than the intermediate transfer belt drive roller 52. At the position, the inner peripheral surface of the intermediate transfer belt 51 is pressed. For this reason, a force in a direction approaching the intermediate transfer belt driving roller 52 is applied to the intermediate transfer belt tension roller 54 by the tension of the intermediate transfer belt 51.

  As shown in FIGS. 7 and 8, the sliding member 24 </ b> A is separated from the intermediate transfer belt tension roller 54 in the axial direction 101 at a portion facing the intermediate transfer belt drive roller 52, and the distance from the shaft member 21. 242A which inclines in the direction which becomes short.

  As an example, the sliding member 24A includes a large-diameter portion 241A, an inclined portion 242A, and a small-diameter portion 243A in order from the side closer to the diameter-expanding member 23A along the axial direction 101. The large diameter portion 241A and the small diameter portion 243A are cylindrical. The inclined portion 242A has a truncated cone shape. A distance L1 between the distal end of the inclined portion 242A farther from the intermediate transfer belt tension roller 54 and the shaft member 21 is a distance L2 between a near end closer to the intermediate transfer belt tension roller 54 and the shaft member 21. Small compared to The sliding member 24B is configured similarly to the sliding member 24A, and has a large diameter portion 241B, an inclined portion 242B, and a small diameter portion 243B.

  The first bracket 261 </ b> A of the urging member 26 </ b> A has a U shape and is disposed so as to sandwich the sliding member 24 </ b> A in the interval changing direction 103. The action shaft 28 </ b> A penetrates in the interval changing direction 103 in a portion of the large diameter portion 241 </ b> A of the sliding member 24 </ b> A that does not intersect the shaft member 21. The first bracket 261A is pivotally supported by the action shaft 28A on both sides of the sliding member 24A in the interval changing direction 103. A gap is provided between the first bracket 261A and the sliding member 24A, and the sliding member 24A is displaceable in the interval changing direction 103 along the action shaft 28A in the first bracket 261A.

  Similarly, the first bracket 261B of the urging member 26B has a U-shape and is arranged so as to sandwich the sliding member 24B in the interval changing direction 103. The sliding member 24B is located in the first bracket 261A. It can be displaced in the interval changing direction 103 along the action axis 28B.

  The through-hole holding member 27A has a guide member 291A that guides while sliding the inclined portion 242A at the edge of the through-hole 271A that is closer to the intermediate transfer belt drive roller 52 in at least the interval changing direction 103. . In this embodiment, the through hole holding member 27A has guide members 291A and 292A at both edges of the through hole 271A in the interval changing direction 103, respectively. Similarly, the through hole retaining member 27B has guide members 291B and 292B at the edge of the through hole 271B.

  When the intermediate transfer belt 51 meanders and shifts to one side in the axial direction 101 of the intermediate transfer belt tension roller 54, for example, the rear surface R side, the sliding member 24B receives the offset force from the intermediate transfer belt tension roller 54 and the rear surface. When moving to the R side, the sliding member 24B moves to the back R side while the inclined portion 242B slides with the guide member 291B provided at the edge of the through hole 271B.

  Since the inclined portion 242B is inclined in such a direction that the distance from the shaft member 21 becomes shorter as it is separated from the intermediate transfer belt tension roller 54, when the sliding member 24B moves to the rear surface R side, as shown in FIG. On the back R side, the shaft member 21 moves in a direction away from the intermediate transfer belt driving roller 52 in the interval changing direction 103. On the other hand, on the front surface F side, the shaft member 21 moves in a direction approaching the intermediate transfer belt driving roller 52 in the interval changing direction 103.

  The intermediate transfer belt 51 that does not have elasticity has a front F-side end portion and a rear surface R of the shaft member 21 with respect to a tension roller having a larger interval between the intermediate transfer belt driving roller 52 and the intermediate transfer belt driven roller 53. It has the property of moving along the axial direction 101 from the end portion having the larger interval among the side end portions toward the end portion having the smaller interval. For this reason, when the intermediate transfer belt 51 is shifted to the back surface R side, the space between the back surface R side end portion of the shaft member 21 and the intermediate transfer belt driving roller 52 is larger than the front surface F side end portion. The belt 51 moves to the front surface F side. Therefore, the meandering of the intermediate transfer belt 51 is corrected by the shaft member 21 moving along the interval changing direction 103 along with the meandering of the intermediate transfer belt 51.

  In this way, the meandering of the intermediate transfer belt 51 is efficiently corrected by moving the shaft member 21 in the two directions of the tension increasing direction and the interval changing direction. Therefore, according to the intermediate transfer unit 50, the meandering of the intermediate transfer belt 51 can be corrected stably and efficiently with a simple mechanism.

  FIG. 10 shows a state in which the intermediate transfer belt 51 meanders to the front surface F side. Also in this case, as in the case shown in FIG. 7, when the intermediate transfer belt 51 meanders and is shifted to the front surface F side, the inclined portion 242A moves to the edge of the through hole 271A when the sliding member 24A moves to the front surface F side. The sliding member 24A moves to the front surface F side while sliding with the guide member 291A provided in the section.

  Since the inclined portion 242A is inclined in such a direction that the distance from the shaft member 21 becomes shorter as it is separated from the intermediate transfer belt tension roller 54, when the sliding member 24A moves to the front surface F side, as shown in FIG. On the front surface F side, the shaft member 21 moves in a direction away from the intermediate transfer belt driving roller 52 in the interval changing direction 103. On the other hand, on the rear surface R side, the shaft member 21 moves in a direction approaching the intermediate transfer belt driving roller 52 in the interval changing direction 103.

  For this reason, when the intermediate transfer belt 51 is shifted to the front surface F side, the distance between the front surface F side end portion and the intermediate transfer belt driving roller 52 is larger than the back surface R side end portion of the shaft member 21. The belt 51 moves to the rear surface R side. Therefore, the meandering of the intermediate transfer belt 51 is corrected by the shaft member 21 moving along the interval changing direction 103 along with the meandering of the intermediate transfer belt 51.

  In this manner, the intermediate transfer belt 51 meanders and pushes the enlarged diameter portions of the enlarged diameter members 23A and 23B, whereby the sliding members 24A and 24B move along the axial direction 101 and both end portions of the axial member 21. Is also moved along the interval changing direction 103, the meandering of the intermediate transfer belt 51 is corrected.

  As shown in FIG. 12, the distance between the sliding member 24 </ b> A and the shaft member 21 decreases as the sliding member 24 </ b> A moves away from the intermediate transfer belt tension roller 54 along the axial direction 101 at the portion facing the intermediate transfer belt drive roller 52. What is necessary is just to have the inclination part which inclines in a direction, and is not limited to having the large diameter part 241A and the small diameter part 243A. Further, the inclined portion 242A is not limited to the truncated cone shape.

  As an example, the sliding member 24 </ b> A can be configured to have an inclined surface 244 </ b> A in a portion closer to the intermediate transfer belt driving roller 52 in the interval changing direction 103. The inclined surface 244A constitutes an inclined portion. The same applies to the sliding member 24B.

  A distance L3 between the distal end of the inclined surface 244A farther from the intermediate transfer belt tension roller 54 and the shaft member 21 is a distance L4 between a near end closer to the intermediate transfer belt tension roller 54 and the shaft member 21. Small compared to.

  The intermediate transfer belt tension roller 54 is positioned between the intermediate transfer belt drive roller 52 and the intermediate transfer belt driven roller 53 and at a position closer to the intermediate transfer belt drive roller 52 than the intermediate transfer belt driven roller 53. Even when the inner peripheral surface 51 is arranged to be pressed, the meandering of the intermediate transfer belt 51 can be corrected efficiently.

  The through holes 271A and 271B are preferably provided with guide members 291A, 292A, 291B and 292B, respectively, but the inclined portions 242A and 242B are not necessarily provided with the guide members 291A, 292A, 291B and 292B. Slides along the edges of the through holes 271A and 271B, so that the meandering of the intermediate transfer belt 51 can be corrected.

  Further, of the offset transmission members 25 </ b> A and 25 </ b> B, the offset transmission member disposed at least downstream in the offset direction along the axial direction 101 of the intermediate transfer belt 51 moves along the axial direction 101 together with the intermediate transfer belt 51. Then, the meandering correction effect of the intermediate transfer belt 51 is exhibited. The offset transmission member arranged on the upstream side in the offset direction also moves along the axial direction 101 together with the intermediate transfer belt 51, so that the meandering correction effect of the intermediate transfer belt 51 is further increased.

  Further, the diameter-expanding members 23A and 23B can be configured integrally with the intermediate transfer belt tension roller 54.

  The present invention can be applied to devices other than the intermediate transfer unit 50 as long as it is a belt drive device for an endless belt that does not have elasticity, and can correct meandering of the endless belt.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

21 Shaft member 22A, 22B Device frame 23A, 23B Expanding member 24A, 24B Sliding member 242A, 242B Inclined portion 244A, 244B Inclined surface 25A, 25B Offset transmission member 26A, 26B Energizing member 261A, 261B First bracket 262A , 262B Second bracket 263A, 263B Mandrel 264A, 264B Elastic member 27A, 27B Through hole holding member 271A, 271B Through hole 28A, 28B Action shaft 291A, 292A, 291B, 292B Guide member 50 Intermediate transfer unit (belt drive unit)
51 Intermediate transfer belt 54 Intermediate transfer belt tension roller 100 Image forming apparatus 101 Axial direction 102 Tension increasing direction 103 Interval changing direction

Claims (5)

An endless belt having no elasticity,
A first tension roller and a second tension roller that stretch the endless belt between each other; and between the first tension roller and the second tension roller and from the first tension roller. A plurality of tension rollers including a tension roller that presses the inner peripheral surface of the endless belt at a position close to the second tension roller;
A shaft member that rotatably supports the tension roller;
A through hole holding member having a through hole through which both end portions of the shaft member are inserted, and
An offset transmission member that is externally inserted into the shaft member so as to be adjacent to both ends in the axial direction of the tension roller and that is inserted through the through-hole, and the offset direction along the axial direction of the endless belt An offset transmission member arranged at least on the downstream side of the endless belt moves in the offset direction along with the offset of the endless belt; and
The shaft member has an elastic force that urges the endless belt in a tension increasing direction in which the tension of the endless belt is increased, the working end is pivotally supported by the offset transmission member, and the base end is the action in the axial direction. An urging member that is pivotally supported at a predetermined position on the opposite side of the tension roller with respect to the end, and
The offset transmission member is inserted into the through-hole so as to be movable in at least two different directions, ie, an interval changing direction in which the interval between the shaft member and the first stretching roller is changed, and the tension increasing direction. ,
The offset transmission member disposed at least on the downstream side in the offset direction is at a distance from the shaft member so as to be separated from the tension roller along the axial direction at a portion facing the first stretching roller. A belt driving device having an inclined portion that is inclined in a direction in which the angle becomes shorter. The offset transmission member has a diameter-expanded portion that is larger than the tension roller and is adjacent to both end portions of the tension roller in the axial direction, and the diameter-expanded member in the axial direction. Including a sliding member adjacent to the diameter-expanding member on the opposite side of the tension roller, and the sliding member is restricted from rotating about the shaft member,
The belt driving device according to claim 1, wherein the inclined portion is provided on the sliding member.   The belt driving device according to claim 1, wherein the through-hole holding member has a guide member that guides while sliding the inclined portion at an edge portion of the through-hole that faces the inclined portion. The offset transmission member arranged on the upstream side in the offset direction moves in the offset direction along with the offset of the endless belt,
Both of the offset transmission members at both ends of the tension roller in the axial direction have the inclined portion,
When the far end of the inclined portion of the offset transmission member on the downstream side in the offset direction is in contact with the edge of the through hole, the offset on the upstream side in the offset direction 4. The belt driving device according to claim 1, wherein a proximal end portion of the inclined portion of the transmission member that is closer to the tension roller is configured to abut against an edge portion of the through hole.   An image forming apparatus comprising the belt driving device according to claim 1.

Images