JP2011107533A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost structure for accurately positioning a stretching unit 61 on which an intermediate transfer belt 1 is stretched, to an apparatus body 70 without play, and enabling efficient belt replacement. <P>SOLUTION: The stretching unit 61 includes three frames 62 to 64. The frames 62 and 64 are connected by a connection arm 65, and the frames 63 and 64 are connected by a connection arm 66. The stretching unit 61 includes a pressing spring 67 pressing the connection arms 65 and 66 in a direction to reduce an angle formed by the connection arms 65 and 66. Notches 71a to 73a and contact parts 71b to 73b are provided in the fixed frames 71 to 73 of the apparatus body 70 respectively, and the dowels 62a, 63a, 63b, 64a and 64b of the frames 62 to 64 or a bearing 8 is engaged or abutted by the pressing force of the pressing spring 67. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus represented by a copying machine, a printer, a printing machine, and the like. Specifically, the present invention relates to a structure in which a belt unit having an endless belt is detachable from an apparatus main body.

  In recent years, in an image forming apparatus, an endless belt-like intermediate transfer belt is arranged to face an image carrier, and an image is temporarily transferred to an intermediate transfer belt by a primary transfer unit and then transferred to a recording material by a secondary transfer unit. Many configurations are used. When configured in this manner, there is an advantage that a wider variety of recording materials can be used because there is no need to directly contact the recording material with the image carrier.

  Such an intermediate transfer belt needs to be periodically replaced because its surface properties, physical characteristics, and the like are consumed and deteriorated as the image forming apparatus is used. Therefore, it is desirable that the stretching unit for stretching the intermediate transfer belt can be easily attached to and detached from the image forming apparatus main body. In addition, when the endurance life of the tension unit is longer than the endurance life of the belt, it is possible to reduce the running cost by replacing only the belt alone. For this reason, it is also desired that the belt unit can be easily detached from the tension unit. On the other hand, since the intermediate transfer belt has a plurality of transfer portions of a primary transfer portion and a secondary transfer portion, high-precision positioning at each transfer portion is required from the viewpoint of image accuracy.

  One example of a conventional structure capable of attaching / detaching the intermediate transfer belt from the image forming apparatus and positioning in the apparatus will be described with reference to FIGS. First, a schematic configuration of the intermediate transfer belt unit 10 having the intermediate transfer belt 1 will be briefly described with reference to FIGS. The intermediate transfer belt 1 is stretched by three rollers: a driving roller 2, a tension roller 3, and a secondary transfer inner roller 4. These three rollers are connected to ground.

  The driving roller 2 and the secondary transfer inner roller 4 are rotatably supported by the frame 5. Both ends of the tension roller 3 are rotatably supported by bearings 6 that are arranged so as to be movable in the left-right direction in FIG. 13 with respect to the frame 5. Moreover, the bearing 6 is urged | biased by the left direction of FIG. Therefore, even if the length of the intermediate transfer belt 1 and the dimensions of other parts are swung due to the dimensional tolerance of the parts, the position of the tension roller 3 is absorbed by shifting in the left-right direction in FIG. 13, and the intermediate transfer belt 1 is almost constant. It is stretched by tension. The intermediate transfer belt 1 supported by such rollers rotates clockwise as the driving roller 2 rotates clockwise in FIG. At this time, the tension roller 3 and the secondary transfer inner roller 4 are driven to rotate as the intermediate transfer belt 1 rotates.

  In addition, bearings 8 are attached to both ends of the driving roller 2, and dowels 9 a project from both end surfaces of the frame 5 in the front-rear direction (the axial direction of each roller, the front and back direction in FIG. 13). Then, the intermediate transfer belt unit 10 formed by stretching the intermediate transfer belt 1 on each roller supported by the frame 5 by the four points of the bearing 8 and the dowel 9a is provided at a predetermined position of the image forming apparatus main body (not shown). Position to. Further, a dowel 9b is provided in the vicinity of the secondary transfer inner roller 4 on both end faces in the front-rear direction of the frame 5, and this is intended to position a secondary transfer unit 24 described later.

  Further, primary transfer rollers 11a to 11d are arranged between the driving roller 2 and the tension roller 3 inside the intermediate transfer belt 1, and each primary transfer roller is respectively moved upward by a spring 12 in FIG. Is being energized. When the intermediate transfer belt unit 10 is mounted on the image forming apparatus main body so as to be able to form an image, each primary transfer roller is moved by the spring 12 via the intermediate transfer belt 1 and a photosensitive drum (not shown) that is an image carrier. To form a primary transfer portion.

  Next, the attaching / detaching operation of the intermediate transfer belt unit 10 from the image forming apparatus main body and the positioning in the apparatus will be described with reference to FIGS. A front guide rail 13 and a rear guide rail 14 are fixed to the front side plate and the rear side plate in the front-rear direction of the image forming apparatus main body, respectively. Guide grooves 15 are formed on the opposite sides of the guide rails 13 and 14, respectively. The intermediate transfer belt unit 10 is attached and detached by moving the intermediate transfer belt unit 10 in the left-right direction in FIG. 16 while engaging the dowels 9a protruding from the right side of FIG. .

  FIG. 17 is a view showing a state in which the intermediate transfer belt unit 10 is mounted in the apparatus main body. The final positioning of the intermediate transfer belt unit 10 is performed by the unit pressurizing mechanism 20. The unit pressurizing mechanism 20 includes a cam 21, a lever 22 that rotates the cam 21, and an arm 23 that swings based on the engagement with the cam 21. As shown in FIG. 17, when the lever 22 is rotated in a state where the intermediate transfer belt unit 10 is set in the image forming apparatus, the arms 23 provided at the front and rear of the main body rotate in the direction of the arrow in FIG. The frame 5 is urged upward in FIG. As a result, the dowel 9a of the frame 5 is drawn from the guide groove 15 into the positioning groove 16 formed in the upper part of FIG. 16, and is abutted against the wall 16a in the left direction and the wall 16b in the upper direction in FIG. Is done. At the same time, the bearing 8 provided on the shaft of the drive roller 2 is also engaged with the positioning groove 17 formed above the guide groove 15 in FIG. As described above, the intermediate transfer belt unit 10 is positioned in the main body by positioning a total of four points of the dowel 9a and the bearing 8 in the main body.

  Further, the secondary transfer outer roller 25 supported by the secondary transfer unit 24 as shown in FIG. 18 faces the secondary transfer portion of the intermediate transfer belt unit 10. The secondary transfer unit 24 is configured to be detachable from the apparatus main body from the left side of 15. The secondary transfer unit 24 is positioned with respect to the intermediate transfer belt unit 10 by engaging the positioning groove 26 of the secondary transfer unit 24 with the dowel 9 b formed on the frame 5 of the intermediate transfer belt unit 10. The

  On the other hand, when the intermediate transfer belt 1 is detached from the intermediate transfer belt unit 10, as shown in FIG. 19, the driving roller 2 is supported and the front and rear frame connecting plates 28, 29 are supported with respect to the main body 27 of the frame 5. The drive frame 30 supported so as to be able to rotate through is rotated. By doing so, as shown in FIGS. 19 and 20, the belt tension diameter of the intermediate transfer belt unit 10 can be made smaller than the circumferential length of the intermediate transfer belt 1, and the belt replacement work can be performed with a margin.

  In addition to the above-described configuration, a configuration has been proposed in which release or pressurization of the belt tension is interlocked with attachment / detachment of the unit to / from the main body (see Patent Document 1). In this configuration, each roller has a guide groove that guides the shaft of the driving roller and a guide groove that guides the shaft of the fixed roller, and each roller is inserted to the tip of each guide groove. The configuration is such that an appropriate tension is applied to the tension roller.

Japanese Patent Laid-Open No. 2001-13800

  As described above, the replacement operation of the intermediate transfer belt is required to improve the positioning accuracy of the primary transfer unit and the secondary transfer unit in addition to the work efficiency. In particular, from the recent demand for higher image quality, the positioning of the unit may result in a misalignment that cannot be ignored even within the range of engagement play by simply engaging a dowel or pin in a hole or groove. For this reason, in the case of the structure like the conventional structure shown in FIGS. 12 to 20, the unit pressurizing mechanism 20 that pressurizes the unit is provided to eliminate backlash. Such a unit pressurizing mechanism 20 needs to deform the highly rigid intermediate transfer belt unit itself in accordance with the positioning to the image forming apparatus main body. Therefore, it is necessary to increase the applied pressure and to have a robust structure. is there. Therefore, it is inevitable that the apparatus will be increased in size and cost. Further, the unit pressurizing mechanism 20 causes an increase in work procedures when the belt is attached and detached, which is not preferable from the viewpoint of improving the efficiency of replacement work.

  Moreover, in the case of the structure described in the above-mentioned Patent Document 1, it is considered that the unit is fixed to the apparatus main body by its own weight. For this reason, there is a possibility that the position of the unit is shifted when vibration occurs in the apparatus main body. In order to eliminate such misalignment, it is necessary to provide a pressurizing mechanism that pressurizes the unit from the outside to prevent misalignment due to vibration or the like. It is inevitable that it will be high. In addition, the operation procedure at the time of attaching and detaching the belt is increased by operating the pressurizing mechanism, and the work efficiency is lowered.

  In view of the circumstances as described above, the present invention has a structure that can perform accurate positioning without wobbling and efficiently perform belt replacement work when a tension unit with a belt is attached to the apparatus main body. It is realized at a cost.

  The present invention includes an apparatus main body provided with an image carrier and a belt unit having an endless belt disposed to face the image carrier, and the belt unit is detachable from the apparatus main body. In the image forming apparatus, the belt unit includes a stretching unit that stretches the belt, and the stretching unit includes a plurality of rollers that stretch the belt and different rollers among the rollers. At least three frame bodies to be supported, at least two connection arms for respectively connecting a pair of frame bodies of each frame body, and two connection arms of each of the connection arms One end side connecting portion that rotatably connects one end portion of the two to the same frame body, and each other end portion of the two connecting arms is rotatably connected to another frame body. And an urging means for urging the two linking arms in a direction in which an angle formed by the two linking arms changes. The apparatus main body is connected to the apparatus main body of the belt unit. In the mounted state, each frame body is controlled based on the urging force by the urging means, and the movement restricting portion that restricts the movement of each frame body based on the urging force by the urging means. A rotation restricting portion that restricts rotation about the movement restricting portion.

  According to the present invention, the position of each frame body can be moved by changing the angle formed by the two connecting arms in a non-attached state to the apparatus main body. Easy to do. Further, by moving the position of each frame body in this way, the tension unit for stretching the belt can be shaped to be easily attached to and detached from the apparatus main body, so that the attachment and detachment work to the apparatus main body can be easily performed. Further, when mounted on the apparatus main body, each frame body is positioned by the movement restricting portion and the rotation restricting portion without rattling based on the urging force of the urging means for urging the two connecting arms. The As a result, when the belt unit is attached to the apparatus main body, accurate positioning can be achieved without rattling, and belt replacement work can be performed efficiently. In addition, since it is not necessary to provide a separate pressurizing mechanism, the cost can be reduced, and the belt replacement work can be made more efficient because there is no need to operate the pressurizing mechanism.

1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic perspective view of an intermediate transfer belt unit according to the present embodiment. Similarly schematic sectional drawing. Similarly, the figure seen from the lower right of FIG. FIG. 3 is a schematic perspective view showing a state in which the intermediate transfer belt unit of the present embodiment is positioned in the apparatus main body, with the main part being pulled out. Similarly, the figure seen from the lower right of FIG. FIG. 7 is a view similar to FIG. 6, showing the force relationship acting on the intermediate transfer belt unit together. The figure which expands and shows the left half part of FIG. 6, in order to demonstrate the force relationship which acts on each frame body and a connection arm. The figure which shows an example of the specific numerical value which satisfy | fills the dynamic relationship demonstrated in FIG. FIG. 7 is a view similar to FIG. 6, illustrating an operation when the intermediate transfer belt unit of the present embodiment is detached from the image forming apparatus main body. FIG. 7 is a view similar to FIG. 6, illustrating an operation when the belt of the intermediate transfer belt unit according to the present embodiment is detached. FIG. 6 is a schematic perspective view illustrating an example of an intermediate transfer belt unit having a conventional structure. Similarly schematic sectional drawing. The schematic perspective view which shows the tension unit which removed the belt. FIG. 3 is a schematic perspective view showing an apparatus main body side structure for attaching an intermediate transfer belt unit to the apparatus main body. Similarly, the figure which cut | disconnected the front-back direction intermediate part and looked at the back guide rail from the lower right part of FIG. FIG. 3 is a schematic perspective view showing a state in which the intermediate transfer belt unit is mounted on the apparatus main body, with a main part extracted. FIG. 3 is a schematic perspective view of a secondary transfer unit. The schematic perspective view which shows the operation | movement at the time of attaching / detaching the belt of a tension unit. Similarly schematic sectional drawing.

  An embodiment of the present invention will be described with reference to FIGS. First, an outline of the image forming apparatus 40 of the present embodiment will be described with reference to FIG. The four photosensitive drums 41a to 41d, each of which is an image carrier, are charged with uniform charges on the surfaces by the charging rollers 42a to 42d, respectively. Image signals of yellow, magenta, cyan, and black are input to the laser scanners 43a to 43d, respectively, and the drum surface is irradiated with laser light in accordance with the image signals to neutralize charges and form a latent image. The latent image formed on the drum surface is developed with yellow, magenta, cyan, and black toners by developing units 44a to 44d. The toner images formed on the surfaces of the drums are primarily transferred sequentially to the surface of the intermediate transfer belt 1 which is an endless belt by primary transfer rollers 11 a to 11 d, and a full-color toner image is formed on the surface of the intermediate transfer belt 1. Is formed. The transfer residual toner on the drum is collected by drum cleaners 45a to 45d. The primary transfer rollers 11a to 11d are opposed to the photosensitive drums 41a to 41d with the intermediate transfer belt 1 interposed therebetween, thereby constituting the primary transfer portion T1.

  On the other hand, the recording material S fed from one of the cassettes 46 and 47 or the manual paper feed unit 48 is fed toward the registration roller 50 by the transport roller 49. After the leading edge of the recording material S hits the stopped registration roller 50 to form a loop, the registration roller 50 starts to rotate in synchronization with the toner image on the intermediate transfer belt 1.

  The toner image on the intermediate transfer belt 1 is secondarily transferred to the recording material S at the secondary transfer portion T2 downstream of the rotation direction of the belt of the primary transfer portion T1, and is fixed to the recording material S by heat and pressure by the fixing device 51. The Thereafter, the recording material S is discharged from the paper discharge unit 52a or 52b to the outside of the apparatus. The secondary transfer portion T2 is configured such that the secondary transfer outer roller 25 faces the secondary transfer inner roller 4 with the intermediate transfer belt 1 interposed therebetween. The transfer residual toner on the intermediate transfer belt 1 that has not been transferred in the secondary transfer portion T2 is collected by the intermediate transfer belt cleaner 53. In the image forming apparatus 40 of this embodiment, the photosensitive drums 41 a to 41 d are arranged above the intermediate transfer belt unit 60 that is a belt unit having the intermediate transfer belt 1, and below the intermediate transfer belt unit 60. A mechanism for conveying the recording material S is disposed.

  In the present embodiment, the intermediate transfer belt unit 60 is detachable from the apparatus main body 70. Accordingly, the configuration of the intermediate transfer belt unit 60 and the configuration for attaching and detaching the image forming apparatus 40 to and from the apparatus main body 70 will be described with reference to FIGS. The basic configuration and operation of the intermediate transfer belt unit 60 are the same as those of the conventional structure shown in FIGS. For this reason, the same code | symbol is attached | subjected to a part equivalent to a conventional structure, and, below, it demonstrates centering on a different part from a conventional structure.

  First, the intermediate transfer belt unit 60 is formed by stretching the intermediate transfer belt 1 on a stretching unit 61. Such a stretching unit 61 has three rollers, which are a plurality of rollers for stretching the intermediate transfer belt 1, that is, a driving roller 2, a tension roller 3, and a secondary transfer inner roller 4. Accordingly, the intermediate transfer belt 1 is stretched by three rollers, that is, a driving roller 2, a tension roller 3, and a secondary transfer inner roller 4. These three rollers are connected to ground.

  The tension unit 61 has three frame bodies 62, 63, and 64, and each of the frame bodies 62, 63, and 64 supports different rollers among the rollers. That is, the driving roller 2 is rotatably supported by the frame body 62, the tension roller 3 is rotatably supported by the frame body 63, and the secondary transfer inner roller 4 is rotatably supported by the frame 64. The frame body 62 rotatably supports the primary transfer rollers 11c and 11d in addition to the driving roller 2, and the frame body 63 supports the primary transfer rollers 11a and 11b in addition to the tension roller 3, respectively. .

  In the case of this embodiment, the tension roller 3 is rotatably supported in the vicinity of both ends by a bearing 6 that can move in the left-right direction in FIG. The bearing 6 is urged by a spring 7 in a movable direction. Therefore, even if the length of the intermediate transfer belt 1 and the dimensions of other parts are swung due to the dimensional tolerances of the parts, the position of the tension roller 3 is absorbed by shifting in the horizontal direction in FIG. 3, and the intermediate transfer belt 1 is substantially constant. It is stretched by tension. Further, when the drive roller 2 rotates in the clockwise direction in FIG. 3, the intermediate transfer belt 1 also rotates in the clockwise direction, and the tension roller 3 and the secondary transfer inner roller 4 also rotate following the rotation of the intermediate transfer belt 1. .

  Further, bearings 8 are attached to both ends of the drive roller 2, and the axial direction of the frame body 62 (the axial direction of each roller, the front-rear direction, the front and back directions of FIGS. 3, 4, 6 to 8, 10, 11). Dowels 62a are projected from both end faces. As will be described later, the frame body 62 is positioned on the image forming apparatus main body 70 by the four points of the front and rear bearings 8 and the dowels 62a. Further, dowels 63a and 63b project from both end faces in the front-rear direction of the frame body 63, and the frame body 63 is positioned on the apparatus main body 70 by these four front and rear dowels 63a and 63b as will be described later. . Similarly, dowels 64a and 64b project from the front and rear end faces of the frame body 64, and the frame body 64 is positioned on the apparatus main body 70 by these four dowels 64a and 64b.

  Further, the primary transfer rollers 11 a to 11 d on the inner side of the surface stretched by the driving roller 2 and the tension roller 3 of the intermediate transfer belt 1 are urged upward in FIG. When the intermediate transfer belt unit 60 is mounted on the apparatus main body 70 and the frame bodies 62 and 63 are positioned, the primary transfer rollers 11a to 11d are moved by the springs 12 to the photosensitive drums 41a to 41d via the intermediate transfer belt 1, respectively. To form the primary transfer portion T1.

  The tension unit 61 has two connecting arms 65 and 66 at the front and rear, and the connecting arms 65 and 66 respectively connect a pair of frame bodies of the frame bodies. . That is, the connecting arm 65 connects the frame body 62 and the frame body 64, and the connecting arm 66 connects the frame body 63 and the frame body 64 in the front-rear direction. In addition, one end of each of the two front connection arms 65 and 66 of these connection arms is rotatably connected to a dowel 64 c protruding from the front side of the same frame body 64. Similarly, one end of each of the two rear connection arms 65 and 66 is rotatably connected to a dowel 64c projecting on the rear side of the same frame body 64. In the case of this embodiment, the connection part of the one end part of the connection arms 65 and 66 and the dowel 64c is used as the one end side connection part.

  On the other hand, the other end of each of the two connecting arms 65, 66 on the front side and the rear side can be rotated by dowels 62b, 63c respectively protruding from the front and rear of the frame bodies 62, 63 which are different frame bodies. Each is linked. That is, the other end of the connecting arm 65 is connected to a dowel 62 b provided on the frame body 62, and the other end of the connecting arm 66 is connected to a dowel 63 c provided on the frame body 63. Further, in the case of this embodiment, elongated holes 65a and 66a are formed in the other ends of the connecting arms 65 and 66, respectively, so as to be long in a predetermined direction that satisfies a force relationship as will be described later. The long hole 65a of the connecting arm 65 can slide on the dowel 62b of the frame body 62, and the long hole 66a of the connecting arm 66 can slide on the dowel 63c of the frame body 63 in a direction perpendicular to the axial direction of each roller. Is engaged. That is, the other end portions of the connecting arms 65 and 66 are slidable with respect to the frame bodies 62 and 63. In the case of the present embodiment, the other end side connecting portion is constituted by the elongated holes 65a and 66a of the connecting arms 65 and 66 and the dowels 62b and 63c of the frame bodies 62 and 63.

  The tension unit 61 includes an urging spring 67 that is an urging means for urging the two connecting arms 65 and 66 in the front and rear directions in a direction in which the angle formed by the connecting arms 65 and 66 changes. . That is, each of the connecting arms 65 and 66 has a spring hooking portion 65b and 66b, respectively. The spring hooking portion 65b of the connecting arm 65 and the spring hooking portion 66b of the connecting arm 66 are respectively connected to both ends of the urging spring 67. I am passing. An urging force is applied between the connecting arms 65 and 66 in such a direction that the angle between the connecting arms 65 and 66 is closed. Accordingly, the front and rear connecting arms 65 and 66 are biased by the biasing spring 67 in the direction in which the mutual angle is closed, and the frame body 62 is connected to the other end of each connecting arm 65 and 66, respectively. , 63 are biased toward each other.

  Further, the tension unit 61 includes a restriction cam 68 that is a holding means capable of switching and holding the angle formed by the two connecting arms 65 and 66 at the front and rear to at least one predetermined angle. In the present embodiment, the restricting cam 68 is rotatably supported by at least one of the front and rear connecting arms 65, and rotates by rotating the operation handle 68a. The cam surface abuts against a part of the connecting arm 66, whereby the angle formed by the connecting arms 65, 66 is maintained at a predetermined angle. The predetermined angle is two as will be described later, but it is also possible to change the shape of the cam surface to three or more.

  Further, the apparatus main body 70 of the present embodiment fixedly supports fixed frames 71, 72, 73 at predetermined positions inside. As shown in FIGS. 5 to 7, each of these fixed frames 71 to 73 is arranged at a position adjacent to the front and rear of the intermediate transfer belt unit 60, three in total, and six in total. Of these, the fixed frame 71 is a frame body 62 that supports the driving roller 2, the fixed frame 72 is a frame body 63 that supports the tension roller 3, and the fixed frame 73 is a frame body 64 that supports the secondary transfer inner roller 4. Are arranged adjacent to each other.

  The fixed frames 71 to 73 restrict the movement of the frame bodies 62 to 64 based on the urging force of the urging spring 67 when the intermediate transfer belt unit 60 is attached to the apparatus main body 70. It has the notches 71a-73a which are a movement control part. Each of the frame bodies 62 to 64 also has contact portions 71 b to 73 b that are rotation restricting portions that restrict rotation about the movement restricting portion based on the biasing force by the biasing spring 67. 5-7, the regulating cam 68 is not in contact with the connecting arm 66, and the urging force of the urging spring 67 is distributed to the frame bodies 62, 63, 64, thereby causing each frame body to move. It is positioned in the apparatus main body 70.

  That is, the fixed frame 71 is formed long in the left-right direction in FIG. 6, and both end portions protrude downward in FIG. At the end of the fixed frame 71 opposite to the fixed frame 72, a notch 71a is formed so as to have a pair of inclined surfaces (butting surfaces) that are inclined in a direction to open downward as viewed in FIG. ing. And the bearing 8 fixed to the rotating shaft of the driving roller 2 supported by the frame body 62 is engaged in the notch 71a so as to be sandwiched between the two inclined surfaces. As shown in FIG. 7, the frame body 62 is doweled in the counterclockwise direction in FIG. 7 based on the contact between the sliding support surface 65c of the elongated hole portion 65a and the dowel 62b by the urging force F of the urging spring 67. A moment M1 centered on 64c acts and is biased in a direction approaching the frame body 63. Therefore, the bearing 8 is engaged with the notch 71a, and the frame body 62 is prevented from moving based on the moment M1 applied by the urging force F, and the bearing 8 is not loosely engaged with the notch 71a. Match.

  Further, at the end of the fixed frame 71 on the fixed frame 72 side, the abutting portion 71b is a surface that opposes the moment direction centering on the engaging portion between the bearing 8 and the notch 71a (this moment direction and (Surfaces in a direction perpendicular to each other). In the case of the illustrated example, this surface is formed substantially parallel to the horizontal direction in FIGS. And the dowel 62a which protruded from the frame body 62 is made to contact | abut to the contact part 71b. That is, a moment about the engaging portion between the bearing 8 and the notch 71a acts on the frame body 62 in the clockwise direction in FIG. 7 due to the moment M1. For this reason, the dowel 62a contacts the contact portion 71b by this moment. Thus, in a state where the urging force F of the urging spring 67 is applied to the frame body 62, the bearing 8 is engaged with the notch 71a, and the dowel 62a is brought into contact with the contact portion 71b. The reaction forces Fo1 and Fs1 act on the frame body 62. As a result, the moment M1 and the reaction forces Fo1 and Fs1 are balanced, and the positioning of the frame body 62 to the apparatus main body 70 is achieved.

  Further, the fixed frame 72 is also formed long in the left-right direction in FIG. 6, and both end portions are protruded downward in FIG. At the end of the fixed frame 72 opposite to the fixed frame 71, a notch 72a is formed so as to have a pair of inclined surfaces (abutment surfaces) that are inclined in a direction of opening toward the lower side of FIG. Yes. In the illustrated example, the inclination angle of the inclined surface on the fixed frame 71 side is steep with respect to the left-right direction in FIG. 6, and the inclination angle of the opposite inclined surface is made gentle with respect to the left-right direction in FIG. . And the dowel 63a which protruded in the notch 72a near the edge part by the side of the tension roller 3 of the frame body 63 is engaged so that it may be pinched | interposed between both inclined surfaces. As shown in FIG. 7, the frame body 63 has a dowel 64c in the clockwise direction in FIG. 7 based on the contact between the sliding support surface 66c of the elongated hole portion 66a and the dowel 63c by the urging force F of the urging spring 67. A moment M <b> 2 centering on is applied and is biased in a direction approaching the frame body 62. Therefore, the dowel 63a is engaged with the notch 72a and the frame body 63 is prevented from moving based on the moment M2 applied by the urging force F, and the dowel 63a is not loosely engaged with the notch 72a. Match.

  In addition, at the end of the fixed frame 72 on the fixed frame 71 side, a contact portion 72b is a surface (this moment direction and the surface opposite to the moment direction centering on the engaging portion between the dowel 63a and the notch 72a). (Surfaces in a direction perpendicular to each other). In the case of the illustrated example, this surface is formed substantially parallel to the horizontal direction in FIGS. Then, a dowel 63 b that projects in the vicinity of the end of the frame body 63 on the side opposite to the tension roller 3 is brought into contact with the contact portion 72 b. That is, the moment centering on the engaging portion between the dowel 63a and the notch 72a acts on the frame body 63 in the counterclockwise direction of FIG. 7 due to the moment M2. For this reason, the dowel 63b contacts the contact portion 72b by this moment. Thus, in a state where the urging force F of the urging spring 67 is applied to the frame body 63, the dowel 63a is engaged with the notch 72a, and the dowel 63b is brought into contact with the contact portion 72b. Reaction forces Fo2 and Fs2 act on the frame body 63 from the front. As a result, the moment M2 and the reaction forces Fo2 and Fs2 are balanced, and the positioning of the frame body 63 to the apparatus main body 70 is achieved.

  The fixed frame 73 is formed in a substantially L shape as a whole, and has a portion disposed in the vertical direction in FIG. 6 and a portion disposed in the left-right direction in FIG. A notch 73a is formed in an L-shape having a surface (abutting surface) on the left side and the lower side in FIG. 6 at the upper end portion in FIG. is doing. And the dowel 64a which protruded in the notch 73a in the position which deviated to the upper side and the left side of FIG. 6 rather than the dowel 64c which connected the one end part of the connection arms 65 and 66 of the frame body 64 between both surfaces is provided. Engage so that it is pinched. As shown in FIG. 7, the frame body 64 has a moment M3 in the counterclockwise direction of FIG. 7 applied to the dowel 64c, which is a connecting portion between the connecting arms 65, 66 and the frame body 64, by the reaction force of the moments M1, M2. It acts and is urged in the direction away from the frame bodies 62 and 63. Therefore, when the dowel 64a is engaged with the notch 73a, the frame body 64 is prevented from moving by the urging force F, and the dowel 64a is engaged with the notch 73a without rattling.

  Further, the contact portion 73b is opposed to the moment direction around the engaging portion between the dowel 64a and the notch 73a at the right end portion in FIG. 6 of the portion disposed in the left-right direction of the fixed frame 73. It is formed so as to have a smooth surface (a surface in a direction perpendicular to the moment direction). In the case of the illustrated example, this surface is formed substantially parallel to the horizontal direction in FIG. And the dowel 64b which protruded from the dowel 64c of the frame body 64 to the lower side and the right side of FIG. That is, a moment about the engaging portion between the dowel 64a and the notch 73a acts on the frame body 64 in the clockwise direction in FIG. 7 due to the moment M3. For this reason, the dowel 64b contacts the contact portion 73b by this moment. In this way, the dowels 64a are engaged with the notches 73a and the dowels 64b are brought into contact with the contact portions 73b in a state where the reaction forces of the moments M1 and M2 are applied to the frame body 64. Reaction forces Fo3 and Fs3 act on the frame body 64. As a result, the moment M3 and the reaction forces Fo3 and Fs3 are balanced, and the frame body 64 is positioned on the apparatus main body 70.

  In addition, the surface which comprises each notch 71a-73a and each contact part 71b-73b considers the direction of the force which acts on each frame body 62-64 with the urging | biasing force of the urging | biasing spring 67. Form. Therefore, for example, if the direction of the urging force of the urging spring 67 and the connecting position by the connecting arms 65 and 66 are different, the design is appropriately changed according to this.

  Next, conditions that satisfy the above relationship will be described. FIG. 8 is a view for explaining how the urging force F of the urging spring 67 acting on the connecting arm 66 is distributed to the frame bodies 63 and 64. A coordinate system having the origin O as a dowel 64a for restricting the movement of the frame body 64 is taken as shown in FIG. 8, and the angle in the x-axis direction is 0, and the direction counterclockwise from the x-axis is positive. An angle with respect to the x-axis of a line connecting the dowel 64c serving as the rotation center of the connecting arm 66 and the origin O is φp, and a distance from the origin O to the dowel 64 is rp. The angle between the line connecting the dowel 64c and the spring hook 66b with respect to the x-axis is φf, the distance from the dowel 64c to the spring hook 66b is a, and the angle of the biasing force F of the biasing spring 67 with respect to the x-axis is α. To do. The angle between the line connecting the dowel 64c and the dowel 63c of the frame 63 and the sliding support surface 66c of the elongated hole portion 66a with respect to the x axis is φn, the distance from the dowel 64c to the sliding support surface 66c is b, The angle with respect to the x-axis of the vertical drag N received by the connecting arm 66 at the dynamic support surface 66c is β.

Here, the moment Mpf around the dowel 64c received by the connecting arm 66 with the spring force F is:
Mpf = a * F * SIN (α−φf) (1)
It becomes. On the other hand, the moment Mpn due to the normal force N generated on the sliding support surface 66c is
Mpn = b * N * SIN (β−φn) (2)
It becomes. From the balance of moment of the connecting arm 66 around the dowel 64c,
Mpf + Mpn = 0 (3)
From (1), (2), (3),
N = −a * F * SIN (α−φf) / (b * SIN (β−φn)) (4)
It becomes. Therefore, when the x component of the force received by the dowel 64c from the connecting arm 66 is fpx and the y component is fpy, the following is obtained.
fpx = F * COSα + N * COSβ
= F * COSα−a * F * SIN (α−φf) * COSβ / (b * SIN (β−φn)) (5)
fpy = F * SINα + N * SINβ
= F * SINα-a * F * SIN (α-φf) * SINβ / (b * SIN (β-φn)) (6)

Furthermore, the moment Mop around the dowel 64a that restricts the movement of the frame body 64 is:
Mop = rp * COSφp * fpy−rp * SINφp * fpx (7)
It is expressed.

On the other hand, the frame body 63 having the dowel 63c that contacts the sliding support surface 66c receives a force in the direction opposite to N in FIG. If the x component of this force is fqx and the y component is fqy,
fqx = −N * COSβ
= A * F * SIN (α−φf) * COSβ / (b * SIN (β−φn))
... (8)
fqy = −N * SINβ
= A * F * SIN (α−φf) * SINβ / (b * SIN (β−φn))
... (9)
It becomes.

If the angle of the line connecting the dowel 63a that restricts the movement of the frame body 63 and the sliding support surface 66c with respect to the x axis is φq, and the distance from the dowel 63a to the sliding support surface 66c is rq, the dowel 63c of the frame body 63 The moment Mon around is
Mon = rq * COSφq * fqy−rq * SINφq * fqx (10)
It becomes.

Generalizing the above relationship, the moment M around the dowel that restricts the movement of the frame body, which occurs in the frame body having a plurality of rotation support portions and sliding support surfaces,
M = Σ (Mapi) + Σ (Monj) (11)
It is expressed.

On the other hand, the angle of the line connecting the contact position between the dowel 64b and the contact portion 64b of the frame body 64 in FIG. 8 and the origin O with respect to the x axis is φs, and the distance from the origin O to this contact position is rs. The angle with respect to the x-axis of the normal line at the contact position is γ. In this case, if the frame body 64 is in stable contact, the drag S generated in the contact portion 64b has the following relationship.
M + rs * S * SIN (γ−φs) = 0 (12)
∴S = −M / (rs * SIN (γ−φs)) (13)

  If this S is positive with respect to all the frame bodies 62 to 64, the pressing force to the contact portions 62b to 64b is secured, and the intermediate transfer belt unit 60 is satisfactorily positioned on the apparatus main body 70 without rattling. it can.

Further, the reaction force Fox and Foy on the frame bodies 62 to 64 generated in the bearing 8 and the dowels 63a and 64a that restrict the movement at that time are as follows.
Fox = −1 * (Σ (Fpx) + Σ (Fqx) + S * COSγ) (14)
Foy = −1 * (Σ (Fpy) + Σ (Fqy) + S * SINγ) (15)
It becomes.

  Then, forces opposite to the resultant direction of the reaction forces Fox and Foy act on the fixed frames 71 to 73 of the apparatus main body 70 from the respective frame bodies 62 to 64. For this reason, when the positioning of the frame bodies 62 to 64 with respect to the fixed frames 71 to 73 is abutted, the positions of the frame bodies 62 to 64 are determined by receiving a force in the direction opposite to the resultant force direction. It is necessary to arrange two abutting surfaces so that

  This is a condition that requires that the angle formed by the vector (-Fox, -Foy) and the two butted surfaces be an acute angle. When the movement restricting portion (notches 71a to 73a) of the unit is configured with two abutting surfaces as described above, there is an advantage that an intermediate transfer belt unit described later can be easily attached and detached.

  FIG. 9 shows an example of specific numerical values satisfying such a dynamic relationship. 9 is a numerical value related to the connecting arm 66, and a supporting point No2 is a numerical value related to the connecting arm 65. Further, since only one connecting arm is connected to each of the frame bodies 62 and 63, it is a numerical value related to each connecting arm. In addition, the coordinates and the symbols of the introduction are appropriately replaced so as to satisfy the relationship described above and FIG. That is, in the description of FIG. 8, symbols are determined for the connection arm 66, but in FIG. 9, this is also replaced with the same symbol for the connection arm 65.

  Next, an operation for attaching / detaching the intermediate transfer belt unit 60 to / from the image forming apparatus main body 70 and an operation for attaching / detaching the intermediate transfer belt 1 from the stretching unit 61 will be described. First, when the intermediate transfer belt unit 60 is removed from the apparatus main body 70, as shown in FIG. 10, the cam surface that is farthest from the rotation center of the regulation cam 68 is obtained by rotating the regulation cam 68 with the operation handle 68a. Is brought into contact with the connecting arm 66. Then, the angle between the connecting arms 65 and 66 is switched to the state shown in FIG. In this state, the connecting arm 66 comes into contact with the cam surface farthest from the rotation center of the regulating cam 68 by the biasing force of the biasing spring 67, and the angle between the connecting arms 65 and 66 is regulated and held in the state shown in FIG. . Therefore, the width of the intermediate transfer belt unit 60 in the vertical direction in FIG. 10 can be reduced (the interval between the frame bodies 63 and 64 is reduced). In this state, for example, as shown in FIG. 10, the dowels 63 a and 63 b of the frame body 63 can be easily separated from the notches 72 a and the abutting portions 72 b of the fixed frame 72. If the positioning of one frame body on the fixed frame is released, the other parts can be easily released, so that the intermediate transfer belt unit 60 can be easily detached from the apparatus main body 70.

  On the other hand, when the intermediate transfer belt unit 60 is attached to the apparatus main body 70, the shape of the stretching unit 61 is deformed so that the vertical width in FIG. This makes it difficult for the intermediate transfer belt 1 stretched on the stretching unit 61 to be brought into contact with other members inside the apparatus main body 70 when inserted into the apparatus main body 70, and prevents the intermediate transfer belt 1 from being damaged. it can. Then, after inserting the intermediate transfer belt unit 60 so as to be in the state shown in FIG. 10, the cam surface of the regulating cam 68 is removed from the connecting arm 66 by rotating the operation handle 68 a. Thereby, based on the urging force of the urging spring 67, the bearings 8 and dowels 62a, 63a, 63b, 64a, and 64b of the frame bodies 62 to 64 are notched to the notches 71a to 73a of the fixed frames 71 to 74, and the contact portions. Each of the members 71b to 73b engages or abuts without rattling. As a result, the intermediate transfer belt unit 60 can be easily positioned with respect to the apparatus main body 70.

  Further, when the intermediate transfer belt 1 is detached from the stretching unit 61 outside the image forming apparatus main body 70, as shown in FIG. 11, the regulating cam 68 is rotated to rotate the operating handle 68a, thereby regulating cam 68. The cam surface closest to the rotation center is brought into contact with the connecting arm 66. Then, the angle between the connecting arms 65 and 66 is switched to the state shown in FIG. In this state, the connecting arm 66 comes into contact with the cam surface closest to the rotation center of the regulating cam 68 by the biasing force of the biasing spring 67, and the angle between the connecting arms 65 and 66 is regulated and held in the state shown in FIG. For this reason, the stretch length between the rollers 2, 3, 4 is shorter than the circumferential length of the intermediate transfer belt 1, so that the intermediate transfer belt 1 can be easily attached to and detached from the stretch unit 61.

  According to the present embodiment, as described above, the position of each of the frame bodies 71 to 73 is moved by changing the angle formed by the two connecting arms 65 and 66 in the front and rear directions in the non-attached state to the apparatus main body 70. Therefore, the intermediate transfer belt 1 can be easily attached to and detached from the stretching unit 61. In particular, in the case of the present embodiment, the angles of the connecting arms 65 and 66 can be switched and held by the restriction cam 68 as described above, so that the angles of the connecting arms 65 and 66 can be easily changed and the intermediate transfer belt 1 can be attached and detached. Work can be done more easily.

  Further, as described above, by moving the position of each of the frame bodies 71 to 73, the stretching unit 61 that stretches the intermediate transfer belt 1 can be formed into a shape that can be easily attached to and detached from the apparatus main body 70. Can be easily attached and detached. In particular, in the case of the present embodiment, the angles of the connecting arms 65 and 66 can be switched and held by the restriction cam 68 as described above, so that the angles of the connecting arms 65 and 66 can be easily changed and attached to and detached from the apparatus main body 70. Work can be done more easily. In this case, the other ends of the connecting arms 65 and 66 are slidable with respect to the frame bodies 62 and 63 in a direction perpendicular to the axial direction of the rollers. For this reason, it becomes easy to match the positional relationship of each frame body 62-64 with the position of the fixed frames 71-73 of the apparatus main body 70, and the above-mentioned attachment / detachment work can be performed more easily.

  Furthermore, the bearings or dowels of the frame bodies 62 to 64 are fixed to the fixed frames 71 to 64 on the basis of the biasing force of the biasing spring 67 that biases the two connecting arms 65 and 66 at the front and rear when the device body 70 is mounted. It engages or abuts on each notch or abutting portion of 73 without rattling. As a result, the intermediate transfer belt unit 60 can be accurately positioned at the desired position of the apparatus main body 70 without rattling. In particular, in the case of a structure having a primary transfer portion T1 and a secondary transfer portion T2 as in this embodiment, accurate positioning is required at each of these transfer portions T1 and T2. In the case of the present embodiment, the intermediate transfer belt unit 60 can be positioned without rattling on the apparatus main body 70, so that even with such a structure, accurate positioning can be performed at each of the transfer portions T1 and T2. As a result, when the intermediate transfer belt 1 unit 60 is mounted on the apparatus main body 70, accurate positioning can be achieved without rattling, and belt replacement work can be performed efficiently.

  In the case of the present embodiment, as described above, the intermediate transfer belt unit 60 can be positioned on the apparatus main body 70 without rattling, and therefore it is not necessary to provide a separate pressurizing mechanism for this positioning. As a result, the cost can be reduced and the efficiency of the belt replacement work can be improved because the pressure mechanism need not be operated.

  As described above, in the case of the present embodiment, high-precision positioning in the apparatus main body 70 of the intermediate transfer belt unit 60 with a simple configuration without using a complicated pressurizing mechanism, unit detachment, and belt detachment work ease. It is possible to achieve both high image quality, low cost, and ease of maintenance.

  In the above-described embodiment, the configuration in which the number of frame bodies is three and the number of connecting arms is two at the front and rear has been described. However, the number of frame bodies may be at least three, and the number of connecting arms is at least two. good. For example, in the case of a structure in which there are four frame bodies A, B, C, and D, the frame bodies A, B, and C and the frame bodies A, B, and D each have a dynamic relationship as in the present embodiment. What is necessary is just to comprise. In this case, a total of four connecting arms are required, at least two for each. Further, even in the present embodiment as described above, the connecting arm is arranged at the intermediate portion in the roller axial direction of each frame body, and even if there are three frame bodies, two connecting arms are used as described above. A simple configuration can also be realized. Moreover, although the fixed frames 71 to 73 are separate bodies, they may be integrated.

  Further, in the present embodiment, the case where the present invention is applied to the configuration of the intermediate transfer system has been described. However, the present invention directly uses an endless belt disposed opposite to each photosensitive drum as a recording material conveyance belt. The present invention can also be applied to a transfer system configuration. That is, the present invention can also be applied to a structure in which the recording material is conveyed to the transfer portion of each photosensitive drum by the recording material conveyance belt and is directly transferred from the photosensitive drum to the recording material. The present invention can also be applied to an image forming apparatus having another known configuration such as a one-drum structure in addition to the tandem structure as described above.

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer belt (belt), 2 ... Drive roller, 3 ... Tension roller, 4 ... Secondary transfer inner roller, 40 ... Image forming apparatus, 41a-41d ... Photosensitive Drum (image carrier), 60... Intermediate transfer belt unit (belt unit), 61... Tension unit, 62 to 64... Frame body, 62 a, 62 b, 63 a, 63 b, 63 c, 64 a, 64 b 64c ... Dowels, 65, 66 ... Connecting arms, 65a, 66a ... Long holes, 67 ... Biasing springs (biasing means), 68 ... Restriction cams (holding means), 70 ... device main body, 71 to 73 ... fixed frame, 71a to 73a ... notch (movement restricting part), 71b to 73b ... contact part (rotation restricting part)

Claims (4)

An image forming apparatus comprising: an apparatus main body including an image carrier; and a belt unit having an endless belt disposed to face the image carrier, the belt unit being detachable from the apparatus main body. ,
The belt unit includes a tension unit that stretches the belt,
The tension unit is
A plurality of rollers for stretching the belt;
At least three frame bodies that support different rollers among the rollers, and
At least two connection arms for connecting a pair of frame bodies of the frame bodies, respectively,
One end side connecting portion that rotatably connects one end portion of each of the two connecting arms of the connecting arms to the same frame body;
The other end side connection part which connects each other end part of the two connection arms to another frame body so that rotation is possible, and
Biasing means for biasing the two connecting arms in a direction in which the angle formed by the two connecting arms changes;
The apparatus main body is
A movement restricting portion for restricting movement of each frame body based on the urging force of the urging means when the belt unit is attached to the apparatus main body;
An image forming apparatus comprising: a rotation restricting portion that restricts each frame body from turning about the movement restricting portion based on an urging force of the urging means.   Each said other end side connection part makes the other end part of the said connection arm slidable to the direction orthogonal to the axial direction of each said roller with respect to the said frame body, The Claim 1 characterized by the above-mentioned. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the tension unit includes a holding unit capable of switching and holding an angle formed by the two connecting arms to at least one predetermined angle.   The belt unit transfers a toner image formed on the surface of the image carrier onto the surface of the belt by a primary transfer unit, and transfers the toner image transferred to the surface of the belt to the belt of the primary transfer unit. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is an intermediate transfer belt unit that transfers to a recording material at a secondary transfer portion downstream in the rotation direction. 5.

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