JP2009031724A - Transfer belt device, method of assembling the same, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer belt device for enhancing a degree of freedom in design by effectively positioning biasing members in a dead space inside a transfer belt. <P>SOLUTION: The transfer belt device is provided with: rollers which are arranged in parallel and include a tension roller 11; a pair of supporting members 23a and 23b which rotatably support both ends of the rollers; the transfer belt 12 which is stretched on the rollers and is rotationally driven; and the biasing members 26a and 26b which apply a tension to the transfer belt 12 by biasing the tension roller 11 in a prescribed direction. The biasing members 26a and 26b apply the tension to the transfer belt in a straight-line direction almost parallel to the plane part of the transfer belt 12 (a direction parallel to the surface in an extending direction which is opposite to the rollers, of the transfer belt) and arranged in an area surrounded by the pair of supporting members 23a and 23b and the transfer belt 12 in a direction of traversing from one supporting member 23a (23b) to the other supporting member 23b (23a). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transfer belt device, an assembly method thereof, and an image forming apparatus including the transfer belt device.

  As a typical image transfer method in a color image forming apparatus, toner images of different colors respectively formed on a plurality of photosensitive members are directly and sequentially superimposed on a sheet conveyed by a transfer belt (transfer conveyance belt) or the like. A direct transfer method is known in which a color image is formed by transfer. As another transfer method, toner images of different colors formed in the same manner as described above are sequentially superimposed and transferred onto a transfer belt (intermediate transfer belt) to form a color image, and the color images are batched. There is an indirect transfer method that transfers to paper.

  The transfer belt used for the direct transfer method and the indirect transfer method is stretched around a plurality of rollers including a tension roller. The tension roller is biased by a biasing member such as a spring to apply a predetermined tension to the transfer belt. is doing.

  In recent years, downsizing of an image forming apparatus has been promoted, and accordingly, downsizing of a transfer belt apparatus is also required. As a conventional transfer belt device, there is one in which an urging member such as a spring is disposed inside a transfer belt which is a dead space in order to reduce the size (for example, see Patent Document 1 or 2).

JP 2002-258629 A JP 2007-72337 A JP 2000-290553 A

  When a spring or the like is used as the urging member of the tension roller, if a spring having a high spring constant is applied, the urging force is likely to fluctuate due to variations in dimensional tolerances of components and errors in assembly accuracy. For example, if the urging force of the pair of springs that urge both ends of the tension roller fluctuates due to the above-described reason and the mutual balance is lost, the running stability of the transfer belt may be reduced. This causes problems such as deterioration of the transfer belt and deterioration of image quality formed on the paper.

  In order to solve the above problem, it is preferable to apply a spring having a spring constant as low as possible to the biasing member of the tension roller. However, in order to obtain a predetermined biasing force with a spring having a low spring constant, a spring that is long to some extent is used. It is necessary to use it.

As shown in Patent Document 1 or 2, when a long spring is used in a structure in which the spring is arranged in a direction perpendicular to the roller, the spring is used as a roller in order to avoid interference between the spring and the roller. It must be arranged vertically shifted so as to intersect. Therefore, with such a spring arrangement method, it has been difficult to change the design such as making the flat space formed between the transfer belts thinner and smaller.
Further, as shown in Patent Document 3, a tension roller is connected to one end of an L-shaped lever member supported to be rotatable about an axis parallel to the axis of the tension roller, and is provided inside the transfer belt. When the tension roller is rotated by the tension spring and the tension roller is pressed against the transfer belt, a space is taken up and down, so that the flat space formed between the transfer belts can be made thinner and smaller. May be difficult.

  In view of such circumstances, the present invention can efficiently dispose a biasing member in a dead space inside a transfer belt, and can improve the degree of design freedom. An image forming apparatus provided with a belt device is to be provided.

  According to the first aspect of the present invention, a plurality of rollers including tension rollers arranged in parallel, a pair of support members that rotatably support both ends of the plurality of rollers, and the plurality of rollers are stretched. In the transfer belt apparatus including a transfer belt that rotates and a biasing member that biases the tension roller in a predetermined direction to apply tension to the transfer belt, the tension roller is movable in a linear direction. The urging member is supported, and is disposed in a direction crossing from the one support member to the other support member in a region surrounded by the pair of support members and the transfer belt.

  Since the urging member is disposed in a direction crossing from one support member to the other support member, it is possible to dispose a long urging member between the rollers while avoiding interference with a roller or the like. In other words, it is possible to employ a biasing member that is not easily affected by variations in dimensional tolerances of components or errors in assembly accuracy without increasing the interval between existing transfer belts. It is also possible to reduce the size of the transfer belt device by setting the distance between the transfer belts narrow. Thus, according to the configuration of the present invention, the degree of freedom in changing the design of the transfer belt device is improved.

  According to a second aspect of the present invention, in the transfer belt device according to the first aspect, the urging member urges both ends of the tension roller in a predetermined direction via a link means.

  By the link means, the direction of the urging force of the urging member can be changed and transmitted to the tension roller. Further, by urging both ends of the tension roller, the tension roller can be stably urged in a predetermined direction.

  According to a third aspect of the present invention, in the transfer belt device according to the second aspect, the link means is a pair of slidably disposed on the support member in a state where both ends of the tension roller are rotatably supported. A holding member and a pair of rotating members that are swingably disposed on the support member and that are engaged with the urging member and the holding member to change the urging force of the urging member in the tension direction of the transfer belt; It is what has.

  Since the link means has a pair of holding members and a pair of rotating members, the direction of the urging force of the urging member can be changed and transmitted to the tension roller. Further, the tension roller can be stably urged in a predetermined direction.

  According to a fourth aspect of the present invention, in the transfer belt device according to the third aspect, the rotating member is formed of a plate material substantially parallel to the planar portion of the transfer belt, and the rotating member is substantially the same as the planar portion of the transfer belt. It is configured to be able to swing in parallel.

  As a result, the transfer belts can be narrowly formed in a direction perpendicular to the planar portion.

  According to a fifth aspect of the present invention, in the transfer belt device according to the third or fourth aspect, the pair of support members are connected by a connecting member, an attachment portion is provided inside the support member, and the rotating member is connected to the connecting member. And the front end of the rotary shaft until the rotary shaft is detached from the insertion hole. A connecting member is disposed so that the connecting member interferes.

  The connecting member can function as a retaining member for the rotating shaft. As a result, there is no need to provide a separate retaining member for the rotating shaft, so the number of parts can be reduced and the manufacturing cost can be reduced.

  According to a sixth aspect of the present invention, in the transfer belt device according to any one of the third to fifth aspects, a posture maintaining member that contacts both surfaces orthogonal to the rotation axis of the rotating member is provided.

  When the rotating member swings, the posture maintaining member supports while sliding on both surfaces of the rotating member, so that the swinging posture of the rotating member is maintained. Thereby, it is possible to prevent the rotating member from being inclined with respect to the rotating shaft, and to solve the problem that the urging force of the urging member is dispersed into unnecessary vectors and the urging force to the tension roller varies. Can do.

  A seventh aspect of the present invention is the transfer belt device according to the sixth aspect, wherein the posture maintaining member is disposed on the connecting member and the mounting portion, respectively.

  There is no need to separately provide a member for attaching the posture maintaining member, and the number of parts can be reduced to reduce the manufacturing cost.

  According to an eighth aspect of the present invention, in the transfer belt device according to any one of the first to seventh aspects, the tension roller is directly or indirectly brought into a predetermined position against the urging force of the urging member. Position holding means for holding is provided.

  In the structure in which the urging member is disposed inside the transfer belt as in the present invention, it is necessary to attach the urging member before mounting the transfer belt to the plurality of rollers. By attaching the urging member, the tension roller is urged, but the tension roller can be temporarily held by the position holding means. By holding the link means in this way, it is possible to easily attach the tension roller and attach the transfer belt to the roller. If the position of the link means is released after the transfer belt is mounted, the tension roller is biased and tension is applied to the transfer belt.

  According to a ninth aspect of the present invention, in the transfer belt device according to any one of the third to seventh aspects, a position holding unit that indirectly holds the tension roller at a predetermined position against a biasing force of the biasing member. The position holding means includes a hole formed in the rotating member, a shaft member that can be inserted into and removed from the hole, and a shaft member formed on a portion of the support member outside the transfer belt. It has a shaft holding part that can be held.

The shaft holding part holds the insertion shaft inserted into the hole of the rotating member against the urging force of the urging member, whereby the position of the rotating member can be temporarily held. Thereby, a holding member can be easily arrange | positioned so that engagement with a rotation member is possible. Then, after the transfer belt is attached, the tension is applied to the transfer belt by removing the shaft member and releasing the position of the rotating member.
Further, since the shaft holding portion is formed on the outer portion of the transfer belt of the support member, the mounted transfer belt does not hinder the shaft member extraction work, and the transfer belt may be damaged when the shaft member is extracted. Nor.

  According to a tenth aspect of the present invention, in the transfer belt device according to the third aspect, a common urging member is connected to the pair of rotating members.

  Thereby, the dispersion | variation in the urging | biasing force given to the both ends of a tension roller can be suppressed.

  According to an eleventh aspect of the present invention, in the transfer belt device according to the tenth aspect, the common urging member has an urging force generating portion and a connecting portion extending in the longitudinal direction from the urging force generating portion. It is.

  As a result, variation in the urging force applied to both ends of the tension roller can be suppressed, and the urging member can be made at low cost.

  A twelfth aspect of the present invention is an image forming apparatus including the transfer belt device according to any one of the first to eleventh aspects.

  The transfer belt device according to any one of claims 1 to 11 can be applied to an image forming apparatus.

  According to a thirteenth aspect of the present invention, there is provided a transfer belt device assembling method in which a transfer belt is stretched around a plurality of rollers including a tension roller rotatably arranged in parallel with a pair of support members. An urging member disposed in a direction crossing from one support member to the other support member in an area surrounded by the planned placement position of the transfer belt is connected to the link means, and the position holding means. Holding the link means in a predetermined position against the urging force of the urging member, and connecting the tension roller to the link means and holding the tension roller in a state where the link means is held in the predetermined position. A step of disposing a transfer belt on the outer periphery of the plurality of rollers, and a step of releasing the position holding of the link means after disposing the transfer belt on the outer periphery of the plurality of rollers. By releasing the position holding of the link means, is a method and a step of tension to the transfer belt urging force of the urging member is transmitted to the tension roller via the link means is applied.

  In this way, the tension roller, the transfer belt, and the like can be easily mounted by temporarily holding the link means so as not to be biased.

  According to a fourteenth aspect of the present invention, in the method for assembling the transfer belt device according to the thirteenth aspect, after the transfer belt is mounted on the outer periphery of a plurality of rollers, the position holding means is operated outside the transfer belt, Releases the position holding of the link means.

  After the transfer belt is mounted, the position holding unit can be easily operated from the outside of the transfer belt to release the position holding of the link unit. The mounted transfer belt does not hinder the shaft member extraction work, and there is no possibility of damaging the transfer belt when the shaft member is extracted.

  According to the transfer belt device of the present invention, the urging member can be efficiently disposed in the dead space inside the transfer belt. Thereby, the freedom degree of the design change of a transfer belt apparatus improves. For example, a design that employs a long biasing member in order to improve the running stability of the transfer belt, or reduces the size by narrowing the space between the transfer belts becomes easy.

  Also in the image forming apparatus provided with the transfer belt device of the present invention, the same effects as the transfer belt device can be exhibited.

  According to the assembly method of the transfer belt device of the present invention, the link means on which the urging force acts is held at a predetermined position, so that the assembling work of the tension roller, the transfer belt and the like is facilitated.

  FIG. 1 is an overall configuration diagram showing an outline of an image forming apparatus provided with a transfer belt device of the present invention. The main part of the image forming apparatus will be described below with reference to FIG. The image forming apparatus includes four process units 1K, 1C, 1M, and 1Y for forming images with developers of black, cyan, magenta, and yellow corresponding to color separation components of a color image.

  The process units 1K, 1C, 1M, and 1Y have the same configuration except that they store different color toners. The configuration of one process unit 1K will be described as an example. The process unit 1K includes an image carrier 2, a cleaning unit 3, a charging unit 4, a developing unit 5, and the like. The process unit 1K is detachably attached to the main body of the image forming apparatus.

  An exposure unit 7 is disposed above each process unit 1K, 1C, 1M, 1Y. The exposure device 7 is configured to emit laser beams (L1 to L4) from a laser diode based on image data.

  A transfer belt device 8 is disposed below each process unit 1K, 1C, 1M, 1Y. The transfer belt device 8 includes a transfer belt 12 for transferring a toner image formed on the image carrier 2 as shown in FIGS. 1 and 2 (indirect transfer system). The transfer belt 12 is configured to be rotatively driven across four primary transfer rollers 91, 92, 93, 94, a driving roller 10, a tension roller 11, and a cleaning backup roller 15 that face each image carrier 2. Yes. A secondary transfer roller 13 is disposed facing the driving roller 10, and a belt cleaning device 14 is disposed facing the cleaning backup roller 15.

  At the lower part of the image forming apparatus, a paper feed cassette 16 capable of storing a large number of sheets as a sheet-like recording medium and a paper feed roller 17 for feeding the paper from the paper feed cassette 16 are provided. On the way from the paper feed roller 17 to the nip between the secondary transfer roller 13 and the driving roller 10, a registration roller pair 18 for temporarily stopping the paper is provided.

  A fixing device 19 is provided above the nip between the secondary transfer roller 13 and the driving roller 10. The fixing device 19 includes a fixing roller 19a that includes a heat source such as a halogen lamp (not shown), and a pressure roller 19b that rotates while contacting the fixing roller 19a with a predetermined pressure.

  Above the fixing device 19, a pair of paper discharge rollers 20 for discharging the paper to the outside is disposed. The paper discharged by the paper discharge roller pair 20 is configured to be stacked on a paper discharge tray 21 formed by recessing the upper cover inward.

  Between the transfer belt device 8 and the paper feed cassette 16, a waste toner container 22 for storing waste toner is disposed. A waste toner transfer hose (not shown) extending from the belt cleaning device 14 is connected to the entrance of the waste toner container 22.

The basic operation of this image forming apparatus will be described below.
In FIG. 1, when the paper feed roller 17 is rotated by a paper feed signal from a control unit of the image forming apparatus (not shown), only the uppermost paper stacked on the paper feed cassette 16 is separated to the registration roller pair 18 side. Sent out. When the leading edge of the paper reaches the nip of the registration roller pair 18, the paper is put on standby to take timing (synchronization) with the toner image formed on the transfer belt 12.

Next, an image forming operation will be described.
The process unit 1K will be described as an example. First, the charging unit 4 charges the surface of the image carrier 2 to a uniform high potential. Based on the image data, the surface of the image carrier 2 is irradiated with the laser beam L1 from the exposure device 7, and the potential of the irradiated portion is lowered to form an electrostatic latent image. The toner is transferred to the surface portion of the image carrier 2 on which the electrostatic latent image is formed by the developing means 5 to form (develop) a black toner image. Then, the toner image formed on the image carrier 2 is transferred to the transfer belt 12. In the other color process units 1C, 1M, and 1Y, toner images are similarly formed on the image carrier 2, and the four color toner images are transferred to the transfer belt 12 so as to overlap.

  Each cleaning unit 3 removes residual toner adhering to the surface of the image carrier 2 after the intermediate transfer process. Thereafter, a neutralization device (not shown) neutralizes residual charges on the image carrier 2 after cleaning.

  The registration roller pair 18 and the paper feed roller 17 resume driving, and the paper is sent to the secondary transfer roller 13 in synchronization with the toner image superimposed on the transfer belt 12. Then, the secondary transfer roller 13 transfers the toner image superimposed and transferred onto the fed paper.

  The sheet on which the toner image has been transferred is conveyed to the fixing device 19. The sheet sent to the fixing device 19 is sandwiched between the fixing roller 19a and the pressure roller 19b, and the unfixed toner image is heated and pressed to be fixed on the sheet. The sheet on which the toner image is fixed is sent out from the fixing device 19 to the discharge roller pair 20 and is discharged to the discharge tray 21 by the discharge roller pair 20.

  In addition, after the toner image on the transfer belt 12 is transferred to a sheet, residual toner adheres on the transfer belt 12, and the residual toner is removed from the transfer belt 12 by the belt cleaning device 14. The toner removed from the transfer belt 12 is conveyed to a powder container 22 and collected by waste toner conveying means (not shown).

Hereinafter, the transfer belt device which is a characteristic part of the present invention will be described.
2 is a perspective view of the transfer belt device 8 of the present invention, and FIG. 3 is a perspective view showing a state in which the transfer belt 12 and the belt cleaning device 14 are removed from the transfer belt device 8 of FIG. As shown in FIG. 2, the transfer belt device 8 has a dimensional ratio that is set large in the length direction indicated by the arrow X and the width direction indicated by the arrow Y, and small in the thickness direction indicated by the arrow Z. Is formed.

  In FIG. 3, the transfer belt device 8 has a pair of resin support members 23a and 23b. The pair of support members 23a and 23b have a channel structure with a rectangular cross section, and are connected by two metal connection members 24 and 25 in the vicinity of both ends. Both ends of the tension roller 11 are rotatably supported at the front ends of the support members 23a and 23b, and both ends of the driving roller 10 are rotatably supported at the back ends of the drawings. ing. Further, four primary transfer rollers 91, 92, 93, 94 and a cleaning backup roller 15 are rotatably supported between the tension roller 11 and the driving roller 10. When the transfer belt device 8 is mounted on the image forming apparatus main body, the plurality of rollers such as the support members 23a and 23b and the tension roller 11 are disposed in the horizontal direction (see FIG. 1).

FIG. 4 is a plan view of the transfer belt device 8 of FIG. 3 as viewed from above. As shown in FIG. 4, the transfer belt device 8 includes a pair of urging members 26a and 26b for urging both ends of the tension roller 11 downward in the drawing (in a linear direction substantially parallel to the flat portion of the transfer belt). And a pair of link means 27a, 27b. In this case, the flat portion of the transfer belt refers to a portion corresponding to a stretched surface where the transfer belt 12 in FIG. 2 faces a plurality of image carriers.
The urging members 26a and 26b are arranged in a direction crossing from one support member 23a (23b) to the other support member 23b (23a). In this embodiment, the urging members 26a and 26b are coil springs and are disposed at right angles to the support members 23a and 23b. A coil spring having a low spring constant, whose urging force is not easily affected by variations in dimensional tolerances of components or errors in assembly accuracy, is employed.

  Each of the link means 27a and 27b has rotating members 28a and 28b that are curved in a substantially C shape in plan view, and longitudinal holding members 29a and 29b. As shown in FIG. 4, the biasing members 26 a and 26 b and the rotating members 28 a and 28 b are counted as the first and second primary transfer rollers 94 and 93 from the tension roller 11 in a state where the transfer belt device 8 is viewed in plan. It is arranged between.

  Hereinafter, the structures of the urging members 26a and 26b, the rotating members 28a and 28b, the holding members 29a and 29b, and the like will be described in detail. Since these structures are symmetrical with respect to the center in the width direction of the transfer belt device, only one side of the structure will be described.

  FIG. 5 shows the left support member 23a, the biasing member 26a, the rotation member 28a, the holding member 29a, and the like in FIG. In FIG. 5, the right side of the support member 23a is referred to as the inside, and the left side is referred to as the outside. The rotation member 28a is disposed so as to be rotatable about the rotation shaft 31 with respect to the support member 23a. A hook-like latching portion 32 is formed at one end portion inside the rotating member 28a, and one end 55 formed in a ring shape of the biasing member 26a is latched on the latching portion 32. The other end 56 of the urging member 26 a formed in a ring shape is hooked on a hook-shaped hook portion 30 provided in the middle portion of the connecting member 24. Note that the latching structures of the both ends of the urging member 26a, the rotating member 28a, and the connecting member 24 are not only the ring and hook latching structures, but also hook latching structures, or other known latching structures. A structure can be adopted.

  On the other hand, the other end portion of the rotating member 28a is arranged to enter the inside through an inner window portion 35 formed on the inner side surface of the support member 23a. The rotating member 28a has a cam portion 36 in which the edge of the other end portion is formed in an arc shape or the like.

  The holding member 29a is a metal longitudinal member, and one end of the tension roller 11 is rotatably attached to the lower end of the drawing. The holding member 29a is attached to the outer side surface of the support member 23a, and is configured to be slidable in the longitudinal direction of the support member 23a. Therefore, the tension roller 11 can move in the linear direction in conjunction with the sliding of the holding member 29a. Specifically, as shown in FIG. 6, the holding member 29 a has two long holes 38, 38 formed in the longitudinal direction, and a stopper 39 such as a screw is inserted into each long hole 38 from the outside. The tip of the stopper 39 is fixed to the support member 23a. In FIG. 6, reference numeral 40 denotes a pressing member that presses the holding member 29 a from the outside, and the pressing member 40 is pressed toward the holding member 29 a by the stopper 39.

  Returning to FIG. 5, the holding member 29 a has a cam receiving portion 34 protruding toward the support member 23 a, and the cam receiving portion 34 enters the inside from an outer window portion 37 formed on the outer side surface of the support member 23 a. Arranged. The holding member 29a is configured to be slidable within a range in which the cam receiving portion 34 can move in the outer window portion 37 in the vertical direction in the figure. And the cam part 36 of the rotation member 28 is arrange | positioned at this cam receiving part 34 so that contact is possible.

  As shown in the simplified diagram of FIG. 7, in a state where the transfer belt 12 is mounted on the tension roller 11, the primary transfer rollers 94, 93, etc., the rotating member 28 a is stretched between the primary transfer rollers 94, 93. It is formed in a plate shape that faces the inner surface of the 12 planar portions (stretched portions) and is substantially parallel to the inner surface. The rotating member 28a is configured to swing substantially parallel to the planar portion. In this embodiment, the rotation member 28a is disposed substantially parallel to the upper and lower planar portions of the transfer belt 12, but one or the plane of the transfer belt 12 closer to the rotation member 28a. You may arrange | position substantially parallel with respect to a shape-shaped part.

  In FIG. 7, the urging member 26a is disposed in a flat space formed between the transfer belts 12, and the urging member 26a is also a planar portion of the transfer belt 12 like the rotating member 28a. It is arrange | positioned so that it may become substantially parallel with respect to.

  8 is a cross-sectional view taken along the line AA in FIG. As shown in the figure, a mounting portion 41 is integrally protruded inside the support member 23a. The connecting member 24 is disposed across the upper portion of the attachment portion 41 in the figure, and the rotating member 28 a is disposed between the attachment portion 41 and the connecting member 24. The rotating shaft 31 is inserted into the through hole 43 formed in the rotating member 28a and the insertion hole 42 formed in the attachment portion 41, and the rotating member 28a is rotatably attached. At the upper end of the rotary shaft 31 in the figure, there is a head portion 33 that is enlarged in the radial direction, and prevents the rotary shaft 31 from falling down due to interference between the head portion 33 and the upper surface of the rotary member 28a in the drawing. Yes. Further, the connecting member 24 is disposed so as to face the head portion 33 of the rotating shaft 31, and the connecting member 24 and the head portion 33 interfere with each other until the rotating shaft 31 is detached from the insertion hole 42 in the upward direction in the figure. It is configured. In the figure, the head portion 33 and the connecting member 24 are not in contact with each other, but the connecting member 24 may be provided in contact with the head portion 33.

  As a material of the rotating shaft 31, it is preferable to apply a material having high wear resistance such as metal. Thereby, the fluctuation | variation of the urging | biasing force accompanying the deformation | transformation of the rotating shaft 31 and the increase in sliding resistance by the rotating shaft 31 being worn by sliding with the rotating member 28a can be prevented. Further, in order to prevent wear due to sliding between the rotating member 28a and the rotating shaft 31, the rotating shaft 31 may be formed integrally with the rotating member 28a by a press or the like.

  In FIG. 8, a mounting portion 44 is integrally provided on the inner side of the support member 23a above the mounting portion 41. A screw hole 46 is formed in the attachment portion 44, and the connecting member 24 is fixed by screwing a screw 45 into the screw hole 46.

  Further, posture maintaining members 47 and 48 are attached to the attachment portion 44 and the attachment portion 41, respectively. The posture maintaining member 47 attached to the attachment portion 44 is disposed so as to come into contact with the upper surface of the rotating member 28a in the figure, and the attachment portion 44 and the posture maintenance member 47 are formed by protrusions and recesses that can be fitted to each other. It is attached (see FIG. 5).

  On the other hand, the posture maintaining member 48 attached to the attachment portion 41 includes two small protrusions, and the tips of these small protrusions are in contact with the lower surface of the rotating member 28a in the figure. Three or more small protrusions may be provided. Also, the posture maintaining member 47 on the upper side in the figure may be a plurality of small protrusions.

  Further, the posture maintaining member 47 may be formed integrally with the connecting member 24 as shown in FIG. In this embodiment, a part of the metal connecting member 24 is pressed and protruded to form the posture maintaining member 47.

  As shown in FIG. 10, the transfer belt device 8 of the present invention includes position holding means 49 that holds the tension roller 11 in a predetermined position indirectly against the urging force of the urging member 26a. The position holding means 49 includes a hole portion 50 formed in the rotating member, a shaft member 51 that can be inserted into and removed from the hole portion 50, and a shaft holding portion 52 formed in the support member 23a. The position of the hole 50 is an end of the rotating member 28a and a portion that has entered the support member 23a. The shaft holding portion 52 is a groove having a shape corresponding to the outer peripheral shape of the shaft member 51, and the hole portion 50 and the shaft holding portion 52 are arranged on a coaxial straight line. In FIG. 10, a two-dot chain line indicates an edge of the transfer belt 12 when it is stretched. The shaft holding portion 52 is disposed outside the end edge of the transfer belt 12.

  As shown in FIG. 11, when the cam receiving portion 34 receives a pressing force from the cam portion 36 of the rotating member 28 a, the cam receiving portion 34 can move until it abuts against the lower edge of the outer window portion 37 in the figure. . That is, the two-dot chain line in the figure shows a state in which the rotating member 28a is swung (rotated) to the maximum in the direction in which the urging force acts. The shaft holding portion 52 rotates in the state in which the rotating member 28a is somewhat moved in the direction (clockwise) opposite to the direction of the urging force shown by the arrow in the figure from the state where the rotating member 28a is maximally swung. It is provided on a straight line coaxial with the hole 50 of the member 28a. In other words, the gap 50 can be formed between the rotating member 28a (the cam portion 36) and the cam receiving portion 34 in a state where the hole portion 50 is arranged on a straight line coaxial with the shaft holding portion 52. ing. By configuring in this way, the urging member 26a can be put in a resting state, so that the assemblability is improved.

  FIG. 12 shows another embodiment of the transfer belt device 8 of the present invention. In the figure, a pair of rotating members 28a and 28b are connected by one (common) biasing member 26c. In the case of the embodiment of FIG. 12, variation in the urging force applied to both ends of the tension roller 11 can be suppressed as compared with the case of the embodiment of FIG. 4. Further, as shown in FIG. 12, by providing a long spring as the urging member 26c, a spring having a lower spring constant can be employed, and the structure is less susceptible to the influence of variations in dimensional tolerances. .

  FIG. 13 shows still another embodiment of the transfer belt device 8 of the present invention. The urging member 26d of this embodiment has an urging force generating portion 53 and a connecting portion 54 extending from the urging force generating portion 53 in the longitudinal direction. For example, the urging force generating portion 53 is a coiled spring portion, and the connecting portion 54 is a linear wire portion extending from the coiled portion. The end portion on the biasing force generating portion 53 side and the end portion on the connecting portion 54 side are connected to a pair of rotating members 28a and 28b. In the case of the embodiment of FIG. 13 as well, both ends of the tension roller 11 are urged by the common urging member 26d, so that variation in the urging force applied to both ends of the tension roller 11 can be suppressed. In addition, the embodiment shown in FIG. 13 has a shorter coil-like spring portion than the embodiment shown in FIG. It should be noted that the connecting portions 54, 54 may be disposed on both ends of the urging force generating portion 53.

  Further, the urging member can be arranged as shown in FIG. FIG. 14 is a simplified view of the transfer belt device 8 of the present invention as viewed from the front. That is, in the figure, the arrow Y direction and the arrow Z direction indicate the same width direction and thickness direction as in FIG. 2, and the upper and lower two-dot chain lines indicate the cross section of the transfer belt 12. As shown in FIG. 14, the pair of urging members 26 e and 26 f are disposed so as to be inclined with respect to the transverse section of the transfer belt 12. The coupling member 24 is provided with two latching portions 30a and 30b, and the latching portions 30a and 30b are arranged at different positions in the thickness direction Z (height direction). Then, the biasing member 26e is bridged from the one latching portion 30a to the rotating member 28a separated from the latching portion 30a, and another biasing member 26f is bridged from the other latching portion 30b to the rotating member 28b spaced apart from the latching portion 30b. The urging members 26e and 26f are arranged in parallel to each other. In this way, the urging members 26e and 26f can be disposed longer by making the urging direction of the urging members 26e and 26f oblique. Therefore, a spring having a lower spring constant can be adopted, and it is less susceptible to the influence of variations in dimensional tolerances. Further, both ends of the urging members 26e and 26f may be shifted obliquely with respect to the longitudinal direction of the support members 23a and 23b (relative to the support members 23a and 23b) (not shown).

  As described above, according to the configuration of the present invention, the urging member 26a is disposed in the transverse direction, so that the urging member 26a can be disposed longer in the flat space in the transfer belt 12. As a result, a member having a low spring constant can be applied as the urging member 26a, and the urging member 26a is less likely to be affected by variations in dimensional tolerances of components and errors in assembly accuracy. Further, as shown in FIG. 7, the rotation member 28a is configured to rotate substantially parallel to the planar portion of the transfer belt 12, so that the flat space between the transfer belts 12 is formed in the thickness direction Z. It can be designed small. Further, in FIG. 7, if the urging member 26 a and the rotating member 28 a are disposed between the primary transfer rollers 93 and 94, the flat space can be further reduced in the thickness direction Z. Thus, the degree of freedom in design is improved by employing the configuration of the transfer belt device of the present invention.

  Hereinafter, the biasing action of the tension roller 11 will be described. Since the urging action to both ends of the tension roller 11 is the same, the urging action to one end of the tension roller 11 will be described as an example with reference to FIG.

  In FIG. 5, the urging member 26a is attached in a state where the contraction force always acts. When the end of the rotating member 28a connected to the urging member 26a is pulled to the right in the drawing by the urging member 26a, the rotating member 28a swings counterclockwise about the rotating shaft 31.

  When the rotating member 28a swings counterclockwise, the cam portion 36 of the rotating member 28a presses the cam receiving portion 34 of the holding member 29a, and the holding member 29a slides downward along the support member 23a in the figure. . As a result, the tension roller 11 attached to the holding member 29a also moves downward in the figure. In this way, the tension roller 11 is urged and moved downward in the figure, whereby the tensioned transfer belt 12 (not shown) is pressed from the inside to apply tension.

  When the rotating member 28 a is formed in a plate shape (thin in the direction of the rotation axis), the rotation member 28 a is easily inclined with respect to the rotation shaft 31. When the rotating member 28a is inclined with respect to the rotating shaft 31, the urging force of the urging member 26a is dispersed into unnecessary vectors, thereby causing a variation in the urging force on the tension roller 11 or the rotation member 28a. There arises a problem that the friction between the rotating shafts 31 increases. Therefore, in the present invention, when the rotating member 28a rotates, the posture maintaining members 47 and 48 support while being in sliding contact with both surfaces of the rotating member 28a (see FIG. 8), so that the swinging posture of the rotating member 28a is maintained. . As a result, the occurrence of the above problems is prevented. Further, in FIG. 8, the posture maintaining member 48 that supports the lower surface of the rotating member 28a is formed with two small protrusions, so that the contact resistance between the small protrusions and the rotating member 28a can be reduced, and smooth swinging can be achieved. Can maintain dynamic movement.

Next, a method for assembling the transfer belt device of the present invention will be described.
First, each roller such as the driving roller 10 and the primary transfer rollers 91 to 94 excluding the tension roller 11 is attached between the pair of support members 23a and 23b. As shown in FIG. 8, the rotation member 28a is rotatably attached to the attachment portion 41 of the support member 23a. And the attitude | position maintenance member 47 and the connection member 24 are attached to the attachment part 44 in order.

  As shown in FIG. 10, the rotation member 28a is swung around the rotation shaft 31, and the hole 50 of the rotation member 28a is arranged on a straight line substantially coaxial with the shaft holding portion 52 of the support member 23a. Then, the shaft member 51 is inserted into the hole 50 of the rotating member 28a from the shaft holding portion 52 side. The distal end of the inserted shaft member 51 comes into contact with the support member 23a and stops with the proximal end of the shaft member 51 slightly protruding from the shaft holding portion 52 (not shown).

  Both ends of the urging member 26a are latched to the latching portion 32 of the rotating member 28a and the latching portion 30 of the connecting member 24 (see FIG. 5). In this state, an urging force is generated in the urging member 26a in a contracting direction, and this urging force acts on the rotating member 28a. However, since the shaft member 51 inserted through the rotating member 28a is held against the biasing force by the shaft holding portion 52, the rotating member 28a is held at a predetermined position.

  Similarly, the other members on the other support member 23b side are also assembled so that the rotating member is held in position against the urging force of the urging member.

  As shown in FIG. 15, the endless transfer belt 12 is moved in the width direction indicated by the arrow in the figure, and is mounted on the outer periphery of each of the rollers such as the drive roller 10 and the primary transfer rollers 91, 92, 93, 94. Thereafter, the tension roller 11 is inserted into a predetermined position inside the transfer belt 12, and holding members 29 a and 29 b are attached to both ends of the tension roller 11.

  As shown in FIG. 5, the cam receiving part 34 of each holding member 29a, 29b is inserted in the outer window part 37 of corresponding support member 23a, 23b. When the cam receiving portion 34 is inserted into the outer window portion 37, the rotary member 28a (28b) is held in position, so that the cam receiving portion 34 is not pressed from the cam portion 36 and the cam receiving portion 34 is cammed. It can be easily arranged to face the portion 36.

  Then, the stopper 39 is fixed while pressing the holding members 29a and 29b with the pressing member 40, and the holding members 29a and 29b are slidably attached to the support members 23a and 23b (see FIG. 6).

  Thereafter, the shaft member 51 is extracted to release the position holding of the rotating members 28a and 28b. The rotating members 28a and 28b whose position holding has been released can swing by receiving the urging force of the urging members 26a and 26b. Due to the urging action described above, the urging force of the urging members 26a and 26b is transmitted to both ends of the tension roller 11 via the rotating members 28a and 28b and the holding members 29a and 29b, and tension is applied to the transfer belt 12. Is done.

  When the urging member and the rotating member are provided inside the transfer belt as in the transfer belt device of the present invention, the urging member and the rotating member must be attached before the transfer belt is mounted on the roller. However, when the urging force of the urging member is applied to the rotating member, it is difficult to attach the holding member, the tension roller, or the transfer belt. Therefore, as in the above assembly method, the rotating member is temporarily held by the shaft member or the like, so that the holding member, the tension roller, the transfer belt, and the like can be easily attached. Further, since the shaft member is disposed outside the transfer belt, the shaft member can be easily pulled out (operated) after the transfer belt is mounted to release the rotation member.

  The above assembling method is an example of the assembling method of the transfer belt device according to the present invention, and the assembling procedure can be changed without departing from the gist of the present invention. For example, after the shaft member 51 is inserted into the rotating members 28a and 28b and held at a predetermined position, the holding members 29a and 29b and the tension roller 11 are first attached to the support members 23a and 23b, and then the transfer belt 12 is attached. You may wear it.

  Further, it is preferable to reduce the protruding amount of the shaft member 51 from the support members 23 a and 23 b so that the transfer belt 12 is not caught by the shaft member 51 when the transfer belt 12 is mounted on the outer periphery of each roller. Further, it is desirable that the end portions of the shaft member 51 that protrude from the support members 23a and 23b are formed on a spherical surface or the like so that the transfer belt 12 is not damaged even if the transfer belt 12 is caught on the shaft member 51. Further, a position holding means for directly fixing the tension roller 11 may be provided.

  As described above, the embodiment in which the transfer belt apparatus of the present invention is applied to an indirect transfer type image forming apparatus has been described. However, the structure of the present invention is such that a sheet for transferring an image is attracted to the belt surface. The present invention can be similarly applied to a direct transfer type image forming apparatus including a transfer belt to be conveyed.

1 is an overall configuration diagram of an image forming apparatus including a transfer belt device of the present invention. It is a perspective view of the transfer belt device. FIG. 3 is a perspective view showing a state where a transfer belt and the like are removed from the transfer belt device of FIG. 2. FIG. 4 is a plan view of FIG. 3. It is a top view which shows the principal part of FIG. It is a simplified diagram showing the attachment structure of the holding member. It is a simplified diagram of the transfer belt device. It is AA arrow sectional drawing of FIG. It is sectional drawing which shows the modification of FIG. It is a perspective view which shows the position holding means of the said transfer belt apparatus. It is a top view which shows the principal part of FIG. It is a top view which shows other embodiment of the transfer belt apparatus of this invention. It is a top view which shows another embodiment of the transfer belt apparatus of this invention. It is a simplification figure showing other ways of arrangement of a biasing member. It is a perspective view for demonstrating the mounting method of a transfer belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Transfer belt apparatus 10 Drive roller 11 Tension roller 12 Transfer belt 23a, 23b Support member 24 Connecting member 26a, 26b Energizing member 27a, 27b Link means 28a, 28b Rotating member 29a, 29b Holding member 31 Rotating shaft 41 Mounting part 42 Insertion Hole 47 Posture maintenance member 48 Posture maintenance member 49 Position holding means 50 Hole portion 51 Shaft member 52 Shaft holding portion 53 Energizing force generating portion 54 Connecting portion 91-94 Primary transfer roller

Claims (14)

A plurality of rollers including tension rollers arranged in parallel; a pair of support members that rotatably support both ends of the plurality of rollers; a transfer belt that is stretched around the plurality of rollers and rotationally driven; In the transfer belt device provided with a biasing member for biasing the tension roller in a predetermined direction to apply tension to the transfer belt,
The tension roller is supported so as to be movable in a linear direction,
The transfer belt, wherein the urging member is disposed in a direction that is traversed from the one support member to the other support member in a region surrounded by the pair of support members and the transfer belt. apparatus.   The transfer belt device according to claim 1, wherein the urging member urges both ends of the tension roller in a predetermined direction via a link unit.   The link means is provided with a pair of holding members slidably disposed on the support member in a state where both ends of the tension roller are rotatably supported, and swingably disposed on the support member. The transfer belt device according to claim 2, further comprising a pair of rotating members that are engaged with the urging member and the holding member and change the urging force of the urging member in a tension direction of the transfer belt.   4. The rotating member is formed of a plate material substantially parallel to the planar portion of the transfer belt, and the rotating member is configured to be swingable substantially parallel to the planar portion of the transfer belt. Transfer belt device.   The pair of supporting members are connected by a connecting member, an attachment portion is provided inside the support member, the rotating member is disposed between the connecting member and the attaching portion, and the tip of the rotating shaft of the rotating member is arranged. The coupling member is disposed so that the coupling member is inserted into an insertion hole formed in the attachment portion and the base end of the rotation shaft interferes with the coupling member until the rotation shaft is detached from the insertion hole. Item 5. The transfer belt device according to Item 3 or 4.   6. The transfer belt device according to claim 3, further comprising a posture maintaining member that makes contact with both surfaces orthogonal to a rotation axis of the rotation member.   The transfer belt device according to claim 6, wherein the posture maintaining member is disposed on each of the connecting member and the attachment portion.   The position holding means for holding the tension roller in a predetermined position directly or indirectly against the urging force of the urging member is provided. Transfer belt device.   Position holding means for indirectly holding the tension roller at a predetermined position against the urging force of the urging member, the position holding means includes a hole formed in the rotating member, and a hole formed in the hole. 8. The shaft member according to claim 3, further comprising: a shaft member that can be inserted and removed; and a shaft holding portion that is formed on a portion of the support member outside the transfer belt and can hold the shaft member. The transfer belt device according to 1.   The transfer belt device according to claim 3, wherein a common biasing member is connected to the pair of rotating members.   The transfer belt device according to claim 10, wherein the common urging member includes an urging force generation portion and a connecting portion extending from the urging force generation portion in a longitudinal direction thereof.   An image forming apparatus comprising the transfer belt device according to claim 1. In a method of assembling a transfer belt device in which a transfer belt is stretched around a plurality of rollers including a tension roller rotatably disposed in parallel with a pair of support members.
An urging member disposed in a direction crossing from one support member to the other support member in a region surrounded by the pair of support members and the position where the transfer belt is to be disposed is connected to the link unit. And holding the link means at a predetermined position against the urging force of the urging member by the position holding means;
A step of connecting a tension roller to the link means in a state where the link means is held at a predetermined position and disposing a transfer belt on the outer periphery of a plurality of rollers including the tension roller;
Releasing the position holding of the link means after disposing a transfer belt on the outer periphery of the plurality of rollers;
And transferring the urging force of the urging member to the tension roller via the linking means so as to apply tension to the transfer belt by releasing the position holding of the linking means. Assembling method of belt device.   14. The transfer belt according to claim 13, wherein after the transfer belt is mounted on the outer periphery of a plurality of rollers, the position holding unit is operated outside the transfer belt to release the position holding of the link unit. Device assembly method.

Images