JP2007187790A - Belt device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt device capable of always keeping a positional relation between an acting member and the external circumferential face of a belt constant even if the belt is displaced. <P>SOLUTION: The belt 40 is rotated in a predetermined direction by a drive roller 1. If a curving member 5 is displaced by stretch or shrink of the belt 40 or the belt 40 is slackened at the start of drive, the positional relation between the acting member 30 and the external circumferential surface of the belt may change. To counteract that, an opposite member 50 is disposed in contact with the internal circumferential face of the belt 40 and opposite the acting member 30 with the belt 40 between them. The opposite member 50 is formed from a material obtained by curving a resin or a light alloy. The opposite member 50 is disposed so that its curved face is in contact with the internal circumferential face of the belt 40. Accordingly, even if the belt 40 is displaced, the positional relation between the acting member 30 and the external circumferential face of the belt 40 is always kept constant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a belt device in which an endless belt is stretched by a plurality of rollers, and more particularly to a belt device including a photosensitive belt, an intermediate transfer belt, a transfer conveyance belt, and the like used in an image forming apparatus. The present invention also relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms an image using the belt device.

  A belt device of this type of image forming apparatus is known in which a part of the outer peripheral surface of an intermediate transfer belt stretched by a driving roller and a support roller is curved toward the inner peripheral surface side of the belt by a bending member. (See Patent Documents 1 and 2).

  FIG. 14 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus described in Patent Document 2. In the figure, reference numeral 1 is a driving roller, reference numerals 2 and 3 are instruction rollers, reference numeral 4 is a belt to intermediate transfer, and reference numeral 5 is a curved member.

  By bending a part of the outer peripheral surface of the belt with the bending member 5 as in this device configuration, the space occupied by the belt device is reduced, and the degree of freedom of layout of the devices arranged around the belt device is expanded. The For example, as shown in FIG. 10, if the fixing device 6 is disposed at a portion bent by the bending member 5 of the belt device, the image forming apparatus main body can be downsized.

  In the image forming apparatus shown in FIG. 14, four image forming units 10 are arranged along the outer peripheral surface of the intermediate transfer belt 4. Each image forming unit 10 includes a photoconductor 11 as an image carrier and an image forming unit that forms a toner image on the photoconductor 11. The image forming means includes a charging roller 12, an exposure device 13, a developing device 14, a photoconductor cleaning device 15, and the like. In FIG. 14, for example, cyan, magenta, yellow, and black toner images are individually formed on the photoreceptor 11 of each image forming unit 10. The toner images of the respective colors formed on the respective photoconductors 11 are primary-transferred by being sequentially superimposed on the intermediate transfer belt 4 by the primary transfer roller 16 disposed to face the respective photoconductors 11. As a result, a full-color composite toner image is formed on the intermediate transfer belt 4.

  The composite toner image formed on the intermediate transfer belt 4 is secondarily transferred onto a transfer paper 18 as a recording medium by a secondary transfer roller 17 disposed opposite to the outer peripheral surface of the belt stretched by the support roller 2. The synthesized toner image secondarily transferred onto the transfer paper 18 is fixed on the transfer paper 18 by separating the transfer paper 18 from the intermediate transfer belt 4 and feeding it to the fixing device 6.

  On the other hand, the residual toner remaining on the intermediate transfer belt 4 without being transferred to the transfer paper 18 in the secondary transfer portion is transferred by a belt cleaning device 19 disposed downstream of the secondary transfer portion in the belt rotation direction. Remove from the intermediate transfer belt 4. The belt cleaning device 19 is configured to remove residual toner on the intermediate transfer belt 4 by a cleaning blade 20 that is in contact with the outer peripheral surface of the belt. The cleaning device 19 is disposed upstream of the bending roller 5 in the belt rotation direction. As a result, the remaining toner on the intermediate transfer belt 4 can be prevented from adhering to the curved roller 5.

  By the way, in the belt device, in order to stabilize the primary transfer of the toner image onto the intermediate transfer belt 4, the drive roller 1 is often disposed downstream of the primary transfer portion in the belt rotation direction. That is, by disposing the driving roller 1 downstream of the primary transfer portion in the belt rotation direction, the belt portion corresponding to the primary transfer portion becomes the belt tension side, and the primary transfer of the toner image to the intermediate transfer belt 4 is performed. The transfer becomes stable. However, in the belt device having such a configuration, the belt portion corresponding to the secondary transfer portion is on the loose side of the belt. For this reason, the secondary transfer of the composite toner image onto the transfer paper 18 may become unstable.

As one method for solving such a problem, the bending member 5 is provided with a function as a belt tension member, and tension is applied to the belt outer peripheral surface on the downstream side in the belt rotation direction of the secondary transfer portion of the belt device. It is possible to grant.
JP-A-8-146706 JP 2000-137386 A

  However, in this type of belt device, there is considerable variation in the belt circumference between the initial use and after use. That is, in the case of a belt having an initial belt circumference of, for example, 950 mm (23 ° C.), the belt circumference itself has a tolerance of about ± 2 mm. In addition, the belt circumference is expected to expand or contract by about ± 2 mm depending on the use environment (temperature of 10 to 32 ° C.), and further, the belt circumference is expected to be extended by about 2 to 3 mm with time. Therefore, in such a belt device, it is necessary to allow for variations in the belt circumferential length of about 10 mm at the maximum.

  For this reason, as described above, in the belt device in which the bending member 5 has a function as a belt tension member, the position of the bending member 5 also varies due to variations in the belt circumferential length. For example, in a belt device having an initial belt circumference of 950 mm (23 ° C.), the bending member 5 may be displaced by 7 mm when the belt circumference changes by 10 mm.

  As described above, when the bending member 5 is displaced due to the change in the belt circumferential length, for example, in the belt device shown in FIG. 14, the positional relationship between the cleaning blade 20 and the belt outer peripheral surface is displaced. Deviation in the positional relationship with the outer peripheral surface causes the cleaning performance of the cleaning blade 20 and the life of the belt device to be reduced.

  That is, when the intermediate transfer belt 4 is displaced in the direction away from the cleaning blade 20 due to the displacement of the bending member 5, the contact angle and the amount of biting of the cleaning blade 20 to the belt outer peripheral surface are reduced. For this reason, in this case, the cleaning performance of the residual toner on the intermediate transfer belt 4 by the cleaning blade 20 is deteriorated. On the other hand, when the intermediate transfer belt 4 is displaced in the direction approaching the cleaning blade 20 due to the displacement of the bending member 5, the contact pressure between the cleaning blade 20 and the outer peripheral surface of the belt increases. For this reason, in this case, there is a possibility that the wear of the outer peripheral surface of the belt is accelerated or a load during rotation of the belt is increased, and the life of the belt device is reduced.

  Here, the problem that the positional deviation of the belt has on the cleaning blade 20 has been described. However, such a problem is not limited to the cleaning blade 20.

  That is, when the belt is displaced as described above, the acting member that exerts a predetermined action on the belt outer peripheral surface in a state where the predetermined positional relationship is maintained with respect to the belt outer peripheral surface on the upstream side of the bending member 5 has some adverse effect. Receive. For example, when this working member is an application member that applies a lubricant such as zinc stearate to the outer peripheral surface of the belt, the contact state between the application member and the outer peripheral surface of the belt changes due to the positional displacement of the belt, and the belt The uniform application of the lubricant is inhibited. Examples of other working members that are adversely affected by such belt misalignment include a charging member that charges the belt outer peripheral surface, a charge eliminating member that neutralizes the belt outer peripheral surface, and an exposure member that exposes the belt outer peripheral surface. .

  Here, the case where the belt is displaced due to the displacement of the bending member 5 has been described. However, such displacement of the belt is also caused by loosening of the belt when the drive roller 1 is driven to rotate. For this reason, in the belt device having the configuration in which the action member is disposed at a position on the loose side of the belt, even if the bending member 5 is not displaced, the action member is adversely affected due to the looseness of the belt. Sometimes.

  Further, here, the problem that the position shift of the intermediate transfer belt 4 gives to the working member has been described. However, this problem is not limited to the position shift of the intermediate transfer belt 4 but can be applied to other belts. For example, in the case of a photosensitive belt, if the positional relationship between the exposure member as the working member and the photosensitive belt is shifted, good latent image formation is impaired. Further, in the case of a paper transport belt for transporting transfer paper, if the positional relationship between the charging member as the working member and the paper transport belt is shifted, electrostatic adsorption of the transfer paper to the paper transport belt is unstable. become. Further, in the case of a fixing belt that fixes a toner image on a transfer paper, if the positional relationship between the releasable oil application member serving as the working member and the fixing belt is shifted, the oil application to the fixing belt becomes uneven. appear.

  The present invention has been made in consideration of the above-described problems, and provides a belt device that can always maintain the positional relationship between the action member and the belt outer peripheral surface even if the belt is displaced. For the purpose.

  Another object of the present invention is to provide an image forming apparatus that forms an image using the belt device.

  The belt device according to claim 1 of the present invention supports an endless belt, a driving roller that rotationally drives the belt in a predetermined direction, and a position on a loose side of the belt that is rotationally driven by the driving roller. A support roller, a bending member that curves the belt outer peripheral surface toward the belt inner peripheral surface side at a position downstream of the support roller in the belt rotation direction, and the belt outer periphery disposed between the support roller and the bending member. In a belt device having a working member that exerts a predetermined action on the outer peripheral surface of the belt in a state where a predetermined positional relationship is maintained with respect to the surface, the belt inner periphery is disposed at a portion facing the working member across the belt. An opposing member that abuts the surface is provided.

  According to a second aspect of the present invention, in the belt device according to the first aspect, the counter member has a belt winding angle around the support roller along a belt outer peripheral surface on the upstream side in the belt rotation direction of the support roller. The sheet conveyed in this manner is in contact with the inner peripheral surface of the belt so that the sheet can be separated from the outer peripheral surface of the belt.

  According to a third aspect of the present invention, in the belt device of the first or second aspect, the belt device includes a belt tension applying member that applies a predetermined tension to the belt, and the belt tension applying member is supported by the displacement thereof. It is arranged at a portion where the wrapping angle of the belt with respect to the roller is not changed.

  According to a fourth aspect of the present invention, in the belt device according to any one of the first to third aspects, the bending member also serves as the belt tension member.

  According to a fifth aspect of the present invention, in the belt device according to any one of the first to fourth aspects, the action member is a cleaning member that cleans the outer peripheral surface of the belt.

  According to a sixth aspect of the present invention, in the belt device according to the fifth aspect, the cleaning member is a blade that abuts against the outer peripheral surface of the belt.

  According to a seventh aspect of the present invention, in the belt device of the fifth aspect, the cleaning member is a fur brush that rotates in contact with the outer peripheral surface of the belt.

  According to an eighth aspect of the present invention, there is provided the belt device according to the fourth aspect, wherein the opposing member is configured such that the belt inner circumferential surface is in a state where the belt is contracted to the maximum and the bending member is displaced toward the belt outer circumferential surface. It arrange | positions in the position which presses, It is characterized by the above-mentioned.

  According to a ninth aspect of the present invention, in the belt device according to the eighth aspect, the working member is wound around the opposite member when the belt is contracted to the maximum and the bending member is displaced toward the outer peripheral surface of the belt. Even when the angle becomes small, the belt is arranged on the back surface of the belt at a position where the facing member contacts.

  According to a tenth aspect of the present invention, in the belt device according to any one of the first to ninth aspects, the bending member is a roller.

  According to an eleventh aspect of the present invention, in the belt device according to any one of the first to tenth aspects, the facing member is a roller.

  According to a twelfth aspect of the present invention, in the belt device according to any one of the first to eleventh aspects, the tension member is a roller.

  According to a thirteenth aspect of the present invention, in the belt apparatus according to any one of the first to twelfth aspects, the belt conveys a recording medium on which an image is recorded, and the image carrier is disposed along the outer peripheral surface of the belt. It is a transfer conveyance belt for transferring an image on a body to the recording medium.

  According to a fourteenth aspect of the present invention, in the belt device according to any one of the first to thirteenth aspects, an image on an image carrier disposed along the outer peripheral surface of the belt is primarily transferred to the belt, and the primary transfer is performed. It is an intermediate transfer belt that secondarily transfers the printed image onto a recording medium fed toward the outer peripheral surface of the belt.

  According to a fifteenth aspect of the present invention, in the belt device according to any one of the first to fourteenth aspects, the belt, the driving roller, the support roller, the bending member, the belt tension applying member, and the action member are integrated with the frame. The frame is configured to be detachably mounted at a predetermined position of an image forming apparatus that forms an image on a recording medium.

  According to a sixteenth aspect of the present invention, in the belt device according to the fifteenth aspect, driving of a drive source provided in a main body of the image forming apparatus in a state where the frame is mounted at a predetermined position of the image forming apparatus. It has a drive transmission means which transmits force to the drive roller.

  According to a seventeenth aspect of the present invention, there is provided an image forming apparatus for carrying an image, an image forming means for forming an image on the image bearing member, and an endless drive driven and rotated by a plurality of rollers. An image forming apparatus having transfer means for transferring an image formed on the image carrier to a recording medium using a belt device having a belt-like shape, wherein the belt device is any one of claims 1 to 16. It is characterized by using a belt device.

  An image forming apparatus according to an eighteenth aspect of the present invention is the image forming apparatus according to the seventeenth aspect, wherein the image forming unit can sequentially form toner images of different colors on the image carrier. It has a developing device provided with a plurality of developing devices.

  An image forming apparatus according to a nineteenth aspect of the present invention is the image forming apparatus according to the seventeenth aspect, wherein the image carrier and the image forming means constitute one image forming unit, and the image forming unit is the belt. A plurality of devices are arranged along the belt of the apparatus.

  In the present invention, when the opposing member abuts on the inner peripheral surface of the belt, the positional relationship between the acting member and the outer peripheral surface of the belt is maintained at a predetermined positional relationship, and the bending member is displaced by the expansion and contraction of the belt. Even if the belt is loosened at the start of driving, the positional relationship between the action member and the belt outer peripheral surface does not shift.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 shows an example of a belt device having a configuration common to the embodiments described later. Of the constituent elements of the belt device according to the following embodiments, those having the same configuration and function as the constituent elements shown in FIG. 14 are the same as the reference numerals assigned to these constituent elements. The description is omitted.

  As shown in FIG. 1, the belt device to which the present invention is applied has an endless belt 40, a driving roller 1, support rollers 2 and 3, and a bending member 5. In FIG. 1, the belt 40 is rotationally driven by a driving roller 1 in a predetermined direction (arrow direction in the figure). The support roller 2 is arranged to support the belt 40 at a position on the loose side of the belt 40 that is rotationally driven by the drive roller 1. The bending member 5 is disposed at a position downstream of the support roller 2 in the belt rotation direction so as to curve the belt outer peripheral surface toward the belt inner peripheral surface. In this belt device, an action member 30 is disposed between the support roller 2 and the bending member 5.

  This working member is a member that exerts a predetermined action on the belt outer peripheral surface in a state in which a predetermined positional relationship is maintained with respect to the belt outer peripheral surface of the belt 40. For example, the above-described cleaning blade 20 or the belt outer peripheral surface An application member for applying a lubricant such as zinc stearate. Further, the action member may be a charging member that charges the belt outer peripheral surface, a static elimination member that neutralizes the belt outer peripheral surface, or an exposure member that exposes the belt outer peripheral surface.

  Further, the belt 40 of the belt device may be any belt such as the intermediate transfer belt 4, the photosensitive belt, the paper conveyance belt, and the fixing belt described above.

  By the way, in such a belt device, if the bending member 5 is displaced by the expansion and contraction of the belt 40 or the belt 40 is loosened at the start of driving, the positional relationship between the action member 30 and the belt outer peripheral surface may be displaced. is there. If the positional relationship between the action member 30 and the belt outer peripheral surface is deviated, the action member 30 cannot exert a predetermined action on the belt outer peripheral surface. Such a problem can be solved by using the belt device according to each embodiment described below. Of the components of the belt device according to the following embodiments, those having the same configuration and function as the components of the belt device shown in FIG. 1 are attached to the components of the belt device. The same reference numerals are used and the description thereof is omitted.

  The belt device according to the first embodiment has the following characteristics in addition to the configuration of the belt device shown in FIG. That is, as shown in FIG. 2, a facing member 50 that abuts against the inner peripheral surface of the belt 40 is provided at a portion facing the action member 30 with the belt 40 interposed therebetween. The opposing member 50 shown in FIG. 2 is configured by bending a resin, a light alloy, or the like, and is disposed so that the curved surface is in contact with the inner peripheral surface of the belt 40.

  The belt device according to the second embodiment has the following characteristics in addition to the configuration of the belt device according to the first embodiment. That is, as shown in FIG. 3, the facing member 50 is in contact with the inner peripheral surface of the belt so that the winding angle θ of the belt around the support roller 2 becomes an angle at which the sheet S can be separated from the outer peripheral surface of the belt. That is, the support roller 2 is configured to have a function as a separating unit that separates the sheet S conveyed along the belt outer peripheral surface of the belt 40 from the belt outer peripheral surface.

  Specifically, in FIG. 3, the sheet S is conveyed in the same direction as the belt rotation direction along the belt outer peripheral surface on the upstream side of the support roller 2. In such a belt device, for example, when the belt 40 is charged, the sheet S conveyed along the belt outer circumferential surface may be wound in an electrostatic close contact with the belt outer circumferential surface. . In the belt device according to the second embodiment, the sheet S is separated from the belt outer peripheral surface of the belt 40 by the winding angle θ of the belt 40 around the support roller 2. Here, the winding angle θ of the belt 40 around the support roller 2 is an angle obtained through experiments or the like in advance so that the sheet S conveyed along the belt outer peripheral surface of the belt 40 can be smoothly separated from the belt outer peripheral surface. It is.

  The belt device according to the third embodiment has the following characteristics in addition to the configurations of the belt devices according to the first and second embodiments. That is, the belt device according to the third embodiment has a belt tension applying member 60 that applies a predetermined tension to the belt 40 as shown in FIG. The belt tension applying member 60 is disposed at a portion where the winding angle θ of the belt 40 with respect to the support roller 2 is not changed by the displacement. In the belt device shown in FIG. 4, the belt tension applying member 60 is provided at a site downstream of the bending member 5 in the belt rotation direction.

  Further, as shown in FIG. 5, for example, the belt tension applying member 60 may also serve as the support member 3 that supports the belt 40 at a site downstream of the bending member 5 in the belt rotation direction. The belt device shown in FIG. 5 has an advantage of being simple and inexpensive since the support member 3 also serves as the belt tension applying member 60.

  The belt device according to the fourth embodiment has the following characteristics in addition to the configuration of the belt device according to the first, second, or third embodiment. That is, as shown in FIG. 6, the bending member 5 has a configuration that also serves as the belt tension applying member 60. That is, in this belt device, the bending member 5 is elastically brought into contact with the outer peripheral surface of the belt 40 by the coil spring.

  The belt device according to the fifth example has the following characteristics in addition to the configuration of the belt device according to the first, second, third or fourth embodiment. That is, as shown in FIG. 7, it has the cleaning member of the cleaning device 19 as the action member 30. As this cleaning member, for example, a cleaning blade 20 or a fur brush 21 can be used. By this cleaning member, belt contaminants adhering to the belt outer peripheral surface of the belt 40 are removed to purify the belt outer peripheral surface. To do. That is, when the belt 40 is a toner carrier such as a photosensitive belt or a transfer belt, the residual toner on the outer peripheral surface of the belt is removed by the cleaning member. Further, when the belt 40 is a paper conveyance body such as a paper conveyance belt or a fixing belt, paper dust on the outer peripheral surface of the belt is removed by a cleaning member.

  The belt device according to the sixth embodiment has the following characteristics in addition to the configuration of the belt device according to the fourth embodiment. That is, the belt device according to the sixth embodiment defines the arrangement position of the opposing member 5, and as shown in FIG. 6, the belt device having a configuration in which the bending member 5 also serves as the belt tension applying member 60. In FIG. 8, when the belt circumferential length changes due to the expansion and contraction of the belt 40, the bending member 5 is displaced. When the belt 40 contracts to the maximum, the belt circumference becomes the minimum. Further, when the belt 40 extends to the maximum, the belt circumferential length becomes maximum. The bending member 5 is displaced according to the change in the belt circumferential length so as to absorb the slack of the belt 40 due to such a change in the belt circumferential length.

  Here, when the belt 40 is extended and the belt circumferential length becomes the maximum, even if the bending member 5 is displaced to the position shown by the broken line in FIG. There is no gap in the relationship. However, when the belt 40 contracts and the belt circumferential length becomes the minimum, the bending member 5 is displaced to the position indicated by the solid line in FIG. 8, and the positional relationship between the opposing member 50 and the belt inner circumferential surface is obtained. Misalignment may occur. The deviation in the positional relationship between the facing member 50 and the inner peripheral surface of the belt adversely affects the action member 30 as described above.

  Therefore, in this belt device, as shown in FIG. 9, even when the belt 40 is contracted to the maximum and the bending member 5 is displaced toward the belt outer peripheral surface side, the facing member 50 presses the inner peripheral surface of the belt. Next, the position of the facing member 50 is defined. Thereby, the positional relationship between the facing member 50 and the belt inner peripheral surface is always a constant positional relationship without being affected by the expansion and contraction of the belt 40.

  The belt device according to the seventh embodiment has the following characteristics in addition to the configuration of the belt device according to the sixth embodiment. That is, the belt device according to the seventh embodiment defines the arrangement position of the action member. As shown in FIG. 15, in the belt device in which the bending member 5 also serves as the belt tension applying member 60. When the belt circumferential length changes due to the expansion and contraction of the belt 40, the bending member 5 is displaced, and at that time, the winding angle of the belt 40 with respect to the facing member 50 also changes. As shown in FIG. 15, the winding angle is maximized when the circumference is maximum, and the winding angle is minimized when the circumference is minimum as shown in FIG. Here, when the circumference is minimum and the winding angle is minimum, depending on the position of the action member, there is no facing member on the back of the belt facing the action member, and the action member cannot function. It may become a state. In FIG. 16, an example of the cleaning blade 20 is given as the action member 30, but in this state, there is no opposing member (here, a roller) on the back of the blade, and the blade pressure is not sufficiently applied to the belt. There is a fear.

  Therefore, as shown in FIG. 17, even when the winding angle is minimized, the cleaning member is prevented from deteriorating by disposing the operating member at a position where the opposing member exists on the back surface of the operating member. .

  The belt device according to the eighth embodiment has the following characteristics in addition to the configurations of the belt devices according to the first to seventh embodiments. That is, in the belt device according to the eighth embodiment, as shown in FIG. 10, the bending member 5, the facing member 50, and the belt tension applying member 60 are each constituted by a roller. Here, any one or two of the bending member 5, the facing member 50, and the belt tension applying member 60 may be configured by a roller. Thus, by constituting each of these members with rollers, the contact friction between the belt inner peripheral surface and each member during the rotation of the belt 40 can be reduced.

  Next, an image forming apparatus using the belt device will be described. Of the constituent elements of the image forming apparatuses described below, those having the same configuration and function as those of the constituent elements of the image forming apparatus shown in FIG. 14 are the same as those of the image forming apparatus shown in FIG. The same reference numerals are assigned to the respective constituent elements, and the description thereof is omitted.

  FIG. 11 shows an example of an image forming apparatus that forms an image using a belt apparatus including an intermediate transfer belt as the belt 40. The image forming apparatus mainly includes an apparatus main body 100, a paper feed table 200 on which the apparatus main body is mounted, a scanner 300 mounted on the apparatus main body, and an automatic document feeder (ADF) 400 mounted thereon.

  The apparatus main body 100 is provided with a belt apparatus including an intermediate transfer belt 40 formed of an endless belt. In FIG. 11, the intermediate transfer belt 40 is stretched around the driving roller 1, the supporting rollers 2 and 3, and the bending member 5, and is driven to rotate clockwise in the drawing. In this image forming apparatus, a belt cleaning device 19 for removing residual toner remaining on the intermediate transfer belt 40 after the secondary transfer is provided as the action member 30 described above. At the facing portion of the belt cleaning device 19, the above-described facing member 50 is disposed so as to always contact the inner peripheral surface of the intermediate transfer belt 40. In the apparatus main body 100, four image forming units 10 that form toner images of black, yellow, magenta, and cyan are arranged side by side along the belt outer peripheral surface of the intermediate transfer belt 40. An exposure device 13 is provided on each of these image forming units 10. A fixing device 6 is disposed below the belt device. Further, below the fixing device 6, there is provided a sheet reversing device 22 that reverses the transfer paper 18 in order to record images on both sides of the transfer paper 18.

  In order to form an image using this image forming apparatus, a document is set on the document table of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass of the scanner 300, and the automatic document feeder 400 is closed and pressed. Next, a start switch (not shown) is pressed. As a result, when a document is set on the automatic document feeder 400, the document is conveyed onto the contact glass. When an original is set on the contact glass, the scanner 300 is immediately driven to read the original image.

  On the other hand, when the start switch is pressed, the drive roller 1 is rotated by a drive motor (not shown). Thereby, the intermediate transfer belt 40 is rotationally driven in a predetermined direction. At the same time, black, yellow, magenta, and cyan single color toner images are formed on the respective photoreceptors of the individual image forming units 10. Then, as the intermediate transfer belt 40 rotates, these single color toner images are sequentially primary transferred onto the intermediate transfer belt 40. As a result, a full-color composite toner image is formed on the intermediate transfer belt 40.

  Also, by pressing the start switch, one of the paper feed rollers 23 of the paper feed table 200 is selected and rotated. As a result, the transfer paper 18 is fed out from the corresponding one paper feed cassette 24. The transfer paper 18 is separated and conveyed one by one, and waits in a state where it abuts against the registration roller 25. The transfer paper 18 is fed between the intermediate transfer belt 40 and the secondary transfer roller 17 by the rotation of the registration roller 25 in synchronization with the composite color image on the intermediate transfer belt 40, and transferred. A color image is recorded on the paper 18.

  The transfer paper 18 after the secondary transfer is sent to the fixing device 6. Then, the secondary transfer toner image is fixed on the transfer paper 18 by heating and pressurizing by the fixing device 6. The transfer paper 18 on which the secondary transfer toner image is fixed is discharged out of the apparatus main body and stacked on the paper discharge tray 26.

  When images are formed on both surfaces of the transfer paper 18, after the image is formed on the front surface or one surface as described above, the switching claw 27 is switched to guide the transfer paper 18 to the sheet reversing device 22. The sheet reversing device 22 inverts the image forming surface of the transfer paper 18 and guides the transfer paper 18 to the secondary transfer portion again. Then, after recording and fixing an image on the back surface of the transfer paper 18, the transfer paper 18 is discharged out of the apparatus main body and stacked on the paper discharge tray 26. The residual toner remaining on the outer peripheral surface of the bell is removed from the intermediate transfer belt 40 after the secondary transfer by the belt cleaning device 19.

  The tandem type image forming apparatus configured as described above is excellent in the following points. That is, in recent years, a large amount of color documents have been handled in offices, and it is desired to provide image forming apparatuses such as full-color printers and full-color copiers that are smaller and faster than before. In response to such demands from the market, many color image forming apparatuses such as color copying machines and color printers are now being provided.

  Color image forming apparatuses include a so-called one-drum type and a tandem type. A one-drum type color image forming apparatus includes a plurality of developing units that form toner images of different colors around one photoconductor as an image carrier. Then, a composite toner image is formed on the photoconductor with these developing units, and the color image is formed by transferring the synthetic toner image on the photoconductor to a recording medium such as paper or an OHP sheet. On the other hand, a tandem type color image forming apparatus includes a plurality of image forming units each including a photoconductor and an image forming unit. Then, a single color toner image of each color is formed on each photoconductor of each image forming unit, and these single color toner images are transferred while being superimposed on a recording medium conveyed by a transfer conveyance belt or an intermediate transfer belt, thereby being combined color. An image is formed.

  Since the one-drum type image forming apparatus has only one photosensitive member, it has an advantage that it can be relatively downsized and cost can be reduced. However, since a full-color image is formed by repeating image formation a plurality of times (usually four times) using one photoconductor, there is a drawback that it is difficult to increase the speed of image formation. On the other hand, the tandem type image forming apparatus has a disadvantage that the size is increased and the cost is increased, but there is an advantage that the speed of image formation can be easily increased.

  Recently, since a demand for an apparatus that forms a full color at a speed comparable to that of a monochrome image is desired, the tandem type image forming apparatus as described above has been attracting attention.

  Tandem type image forming apparatuses include a direct transfer type and an indirect transfer type. The direct transfer tandem type image forming apparatus is configured to sequentially transfer images on the photoreceptor of each image forming unit onto a recording medium conveyed by a transfer conveyance belt. On the other hand, an indirect transfer tandem type image forming apparatus firstly performs primary transfer by sequentially superimposing images on the photoreceptor of each image forming unit on an intermediate transfer belt. Next, the primary transfer image on the intermediate transfer belt is configured to be secondary-transferred collectively onto a recording medium.

  Incidentally, a direct transfer type tandem type image forming apparatus generally has a configuration in which image forming units are juxtaposed in a horizontal direction along a transfer conveyance belt. Accordingly, the sheet feeding device for feeding the recording medium is arranged on the most upstream side of the transfer conveyance belt, and the fixing device for fixing the image transferred to the recording medium is arranged on the most downstream side. For this reason, there is a drawback that the peripheral length of the horizontal portion for conveying the recording medium of the transfer conveyance belt becomes long and the apparatus main body becomes large in the horizontal direction.

  In order to avoid such an increase in the size of the apparatus main body in the horizontal direction, it is necessary to place the fixing device close to a separation unit where the recording medium onto which the composite toner image is transferred is separated from the transfer conveyance belt. However, with such a configuration, it is difficult to secure a sufficient interval between the separation unit and the fixing device so that the recording medium separated from the transfer conveyance belt can bend with sufficient margin. For this reason, in the configuration in which the separation unit and the fixing device are close to each other, the impact when the leading edge of the recording medium enters the fixing device (larger as the recording medium is thicker), the conveyance speed of the fixing apparatus, and the conveyance speed of the transfer conveyance belt The transfer image is liable to be adversely affected by the difference in speed.

  On the other hand, the intermediate indirect transfer type tandem type image forming apparatus can set the position of the secondary transfer portion relatively freely. Therefore, this indirect transfer tandem type image forming apparatus has an advantage that the sheet feeding device and the fixing device can be arranged below the intermediate transfer belt, and the apparatus main body can be downsized in the horizontal direction. . In addition, as described above, the recording medium separated from the intermediate transfer belt is bent between the separation unit of the intermediate transfer belt and the fixing device by disposing the paper feeding device and the fixing device below the intermediate transfer belt. It will be possible to secure a sufficient interval.

  As described above, in the tandem type image forming apparatus of the intermediate transfer system, since the fixing device can be disposed with a margin, the influence of the fixing device on image formation can be almost eliminated. In view of the above, recently, an intermediate transfer type tandem type image forming apparatus has attracted attention.

  By the way, in such an image forming apparatus, the composite toner image on the intermediate transfer belt 40 is collectively transferred onto the transfer paper 18 in the secondary transfer portion, and then the transfer paper 18 is transferred to the intermediate transfer belt 40 in the separation portion. It is necessary to ensure separation from The separability of the transfer paper 18 at this separation part also affects the material of the intermediate transfer belt 40, the entry angle of the recording medium, and the like, but is large in the winding angle θ around the support roller 2 of the intermediate transfer belt 40 in the separation part. It depends on you. If the winding angle θ of the intermediate transfer belt 40 with respect to the support roller 2 forming the separation portion is small, the separation property of the transfer paper 18 at the separation portion is deteriorated. In the worst case, the transfer paper 18 may be conveyed so as to be wound around the intermediate transfer belt 40 without being separated by the separation unit. For this reason, an image forming apparatus using such an intermediate transfer belt 40 has conventionally required a separation charger and a separation claw for assisting smooth separation of the transfer paper 18 in the separation section.

  In the image forming apparatus shown in FIG. 11, the belt outer peripheral surface of the intermediate transfer belt 40 is bent toward the belt inner peripheral surface side by the bending member 5. Therefore, in this image forming apparatus, the winding angle θ of the intermediate transfer belt 40 with respect to the support roller 2 can be sufficiently obtained. Accordingly, in this image forming apparatus, the transfer paper 18 can be smoothly separated at the separation portion of the intermediate transfer belt 40, and a separation charger and a separation claw for assisting the separation are not necessary. In addition, since the belt outer peripheral surface of the intermediate transfer belt 40 is curved toward the belt inner peripheral surface side by the bending member 5, the degree of freedom of the intermediate transfer belt 40 is increased, and the space of the belt device can be saved. Can be realized.

  Here, the rollers 1, 2, 3, 5 of the belt device are rotatably supported by a pair of frames (not shown). Further, the pair of frames are arranged to face each other so as to form a space larger than at least the width of the intermediate transfer belt 40. Further, this frame is configured to be detachable from a predetermined mounting position of the apparatus main body 100 shown in FIG. The belt device transmits a driving force of a driving source (not shown) provided in the apparatus main body 100 to the driving roller 1 in a state where the frame is mounted at a predetermined position of the apparatus main body 100. Have means. As the drive transmission means, a coupling, a bevel gear, an electromagnetic clutch, or the like can be used.

  FIG. 12 shows an example of an image forming apparatus having a configuration in which the belt 40 of the belt device is a paper conveyance belt. Of the components of the image forming apparatus, those having the same configuration and function as the components of the image forming apparatus shown in FIG. 11 are included in the components of the image forming apparatus shown in FIG. The same reference numerals are used and the description thereof is omitted.

  In FIG. 12, when the driving roller 1 rotates, the paper transport belt 40 is driven to rotate in the direction of the arrow. As a result, a toner image of each color is formed on the photoreceptor 11 of each image forming unit 10. The transfer paper 18 is fed out from the paper feed cassette 24 in synchronism with the operations for forming the toner images of the respective colors. The transfer paper 18 is separated and conveyed one by one, and waits in a state where it abuts against the registration roller 25. The transfer paper 18 is transported along the outer peripheral surface of the paper transport belt 40 in synchronization with the formation of toner images of the respective colors on the respective photoreceptors 11. The toner images of the respective colors formed on the photoreceptor 11 are sequentially superimposed and transferred onto the transfer paper 18 that is conveyed along the outer peripheral surface of the paper conveying belt 40. As a result, a color image is recorded on the transfer paper 18.

  As shown in FIG. 12, by using the belt device, even in the direct transfer type image forming apparatus, the paper feed cassette 24 can be arranged so as to bite below the belt device, and can be formed in a relatively small size. It becomes possible. Further, in this direct transfer type image forming apparatus, since the toner image is not transferred to the belt 40, it is not necessary to provide a secondary transfer portion on the outer peripheral surface of the belt. Therefore, in this image forming apparatus, as shown in FIG. 13, the belt cleaning device 19 can be disposed at a portion facing the support roller 2. Thereby, the support roller 2 can be provided with the function as the belt tension member 60, and the apparatus can be simplified and the cost can be reduced.

  In the belt device according to each of the embodiments, the opposing member 50 abuts on the belt inner peripheral surface of the belt 40, so that the belt outer peripheral surface and the action member 30 maintain a constant positional relationship. Thereby, even if the bending member 5 is displaced due to the expansion and contraction of the belt 40 or the belt 40 is loosened at the start of driving, the positional relationship between the action member 30 and the belt outer peripheral surface is not displaced. In particular, in the belt device according to the second embodiment, the winding angle θ of the belt 40 around the support roller 2 with the facing member 50 in contact with the belt inner circumferential surface of the belt 40 causes the sheet S to move from the belt outer circumferential surface. The angle can be separated. Therefore, the sheet S conveyed along the belt outer peripheral surface of the belt 40 is smoothly separated from the belt outer peripheral surface by the winding angle θ of the belt 40 around the support roller 2. In the belt device according to the third embodiment, the winding angle θ of the belt 40 with respect to the support roller 2 does not change even when the belt tension applying member 60 is displaced. In the belt device according to the fourth embodiment, tension is applied to the belt 40 by the bending member 5 that also serves as the belt tension applying member 60. Thereby, it is not necessary to provide the belt tension member 60 independently, and the cost of the belt device can be reduced. Further, in the belt device according to the fifth embodiment, the facing member 50 keeps the cleaning blade 20 and the fur brush 21 of the belt cleaning device 19 as the action member 30 and the belt outer peripheral surface in a predetermined positional relationship. Become. Thereby, the belt outer peripheral surface of the belt 40 is stably cleaned. In the belt device according to the sixth embodiment, the opposing member 50 and the belt inner peripheral surface always maintain a constant positional relationship without being affected by the expansion and contraction of the belt 40. Thereby, even if the belt 40 contracts and the belt circumferential length becomes the minimum, the positional relationship between the facing member 50 and the belt inner circumferential surface does not shift. In the belt device according to the seventh embodiment, any one, two, or all of the bending member 5, the facing member 50, and the belt tension applying member 60 are provided on the inner peripheral surface of the belt 40. It comes in contact while rotating. Thereby, the contact friction between the belt inner peripheral surface and each member during the rotation of the belt 40 is reduced, and the belt 40 is stably rotated. Further, wear due to friction on the belt inner peripheral surface of the belt 40 is reduced, and the belt life can be extended.

  That is, in the present invention, an endless belt, a driving roller for driving and rotating the belt in a predetermined direction, a supporting roller for supporting the belt at a loose side position of the belt driven and rotated by the driving roller, and the supporting A bending member that bends the outer peripheral surface of the belt toward the inner peripheral surface of the belt at a position downstream of the roller in the belt rotation direction, and is disposed between the support roller and the bending member and has a predetermined positional relationship with respect to the outer peripheral surface of the belt In a belt device having an action member that exerts a predetermined action on the outer peripheral surface of the belt in a state where the belt is maintained, an opposing member that contacts the inner peripheral face of the belt is provided at a portion that faces the action member across the belt. In this belt device, the counter member is brought into contact with the inner peripheral surface of the belt, whereby the position of the action member and the outer peripheral surface of the belt is increased. Relationship will be maintained in a predetermined positional relationship. Accordingly, even if the bending member is displaced due to the expansion and contraction of the belt or the belt is loosened at the start of driving, the positional relationship between the action member and the belt outer peripheral surface does not occur.

  In the belt device, the counter member may be configured to remove a sheet conveyed along the belt outer circumferential surface on the upstream side in the belt rotation direction of the support roller from the belt outer circumferential surface. By setting the angle so as to be able to be separated, reliable separation can be achieved. And a belt tension applying member for applying a predetermined tension to the belt, and the belt tension applying member is disposed at a position where the belt winding angle with respect to the support roller is not changed by the displacement. No loss of sex. Further, since the bending member also serves as the belt tension member, the number of parts can be reduced and the cost can be reduced. Moreover, the said action member can be used as the cleaning member which cleans the said belt outer peripheral surface. The cleaning member may be a blade that contacts the outer peripheral surface of the belt or a fur brush that rotates in contact with the cleaning member.

  According to the present invention, the counter member is disposed at a position that presses the inner peripheral surface of the belt even when the belt is contracted to the maximum and the bending member is displaced toward the outer peripheral surface of the belt. Even when the circumferential length changes, the positional relationship between the opposing member and the belt inner circumferential surface can be made constant. Further, in such a belt device, even when the belt contracts to the maximum and the bending member is displaced toward the outer peripheral surface of the belt so that the wrapping angle of the belt with respect to the opposing member becomes small, By disposing the action member at a position where the member comes into contact, even when the belt circumferential length is changed and the winding angle is minimized, deterioration of the effect of the action member can be prevented. Further, by using the bending member as a roller, the contact friction between the belt and the bending member, the belt and the opposing member, and the belt and the tension member can be reduced. Furthermore, the belt can correspond to a transfer conveyance belt that conveys a recording medium on which an image is recorded, and transfers an image on an image carrier disposed along the outer peripheral surface of the belt to the recording medium. In the belt, an image on an image carrier disposed along the outer peripheral surface of the belt is primarily transferred, and an intermediate image in which the primary transfer is secondarily transferred to a recording medium fed toward the outer peripheral surface of the belt. It can correspond to a transfer belt.

  The belt, the driving roller, the supporting roller, the bending member, the belt tension applying member, and the action member are integrally stored in a frame, and the frame is a predetermined position of the image forming apparatus that forms an image on a recording medium. It can be set as the structure with which it is mounted | worn. In such a belt device, a device having a drive transmission means for transmitting a driving force of a driving source provided in a main body of the image forming apparatus to the driving roller in a state where the frame is mounted at a predetermined position of the image forming apparatus. Yes.

  Furthermore, the present invention provides a belt device comprising an image carrier that carries an image, an image forming unit that forms an image on the image carrier, and an endless belt that is stretched and driven by a plurality of rollers. Each of the belt devices described above can be employed in an image forming apparatus having a transfer means for transferring an image formed on the image carrier using a recording medium to a recording medium. In such an image forming apparatus, the image forming unit is adapted to an apparatus having a developing device having a plurality of developing devices capable of sequentially superposing and forming toner images of different colors on the image carrier. it can. Further, the present invention can be applied to an apparatus in which the image carrier and the image forming means constitute one image forming unit, and a plurality of the image forming units are arranged along the belt of the belt device.

Schematic configuration diagram showing the configuration of a belt device common to each embodiment of the present invention 1 is a schematic configuration diagram showing the configuration of a belt device according to a first embodiment of the present invention. The schematic block diagram which shows the structure of the belt apparatus based on 2nd Example of this invention. The schematic block diagram which shows the structure of the belt apparatus based on 3rd Example of this invention. The schematic block diagram which shows the other structure of the belt apparatus based on 3rd Example of this invention. The schematic block diagram which shows the structure of the belt apparatus based on the 4th Example of this invention. The schematic block diagram which shows the structure of the belt apparatus based on the 5th Example of this invention. Schematic configuration diagram showing the behavior of the belt in the belt device according to each embodiment of the present invention. The schematic block diagram which shows the structure of the belt apparatus based on the 6th Example of this invention. The schematic block diagram which shows the structure of the belt apparatus based on the 8th Example of this invention. 1 is a schematic configuration diagram showing an example of an image forming apparatus of the present invention. Schematic configuration diagram showing another example of the image forming apparatus of the present invention FIG. 12 is a main part schematic diagram showing another configuration example of the image forming apparatus shown in FIG. Schematic configuration diagram showing an example of a conventional image forming apparatus The schematic block diagram which shows one of the structural examples of the belt apparatus which concerns on the 7th Embodiment of this invention. Schematic block diagram which shows the other structural example of the belt apparatus which concerns on the 7th Embodiment of this invention. Schematic configuration diagram showing still another configuration of a belt device according to a seventh embodiment of the present invention.

Explanation of symbols

1: Drive roller 2: Support roller (separation roller)
3: Support roller 4, 40: Belt (intermediate transfer belt, paper transport belt)
5: Curved member 6: Fixing device 10: Image forming unit 11: Photoconductor 12: Charging roller 13: Exposure device 14: Developing device 15: Photoconductor cleaning device 16: Primary transfer roller 17: Secondary transfer roller 18: Transfer Paper 19: Belt cleaning device 20: Cleaning blade 21: Fur brush 24: Paper feed cassette 30: Action member 50: Opposing member 60: Belt tension member 100: Main body 200: Paper feed table 300: Scanner 400: Automatic document feeder S: Sheet θ: Rolling angle of belt around roller

Claims (19)

An endless belt, a driving roller that rotationally drives the belt in a predetermined direction, a support roller that supports the belt at a position on the loose side of the belt that is rotationally driven by the driving roller, and a belt rotation direction of the support roller A curved member that curves the belt outer peripheral surface toward the belt inner peripheral surface at a downstream position, and a state in which a predetermined positional relationship is maintained with respect to the belt outer peripheral surface, disposed between the support roller and the curved member In the belt device having an action member that exerts a predetermined action on the outer peripheral surface of the belt, a facing member that contacts the inner peripheral surface of the belt is provided at a portion that faces the action member across the belt. Belt device. 2. The belt device according to claim 1, wherein the opposing member is configured to transfer a sheet conveyed along a belt outer peripheral surface of the support roller, the belt winding angle upstream of the support roller in the belt rotation direction. A belt device, wherein the belt device is in contact with the inner peripheral surface of the belt so that the angle can be separated from the belt. 3. The belt device according to claim 1, further comprising: a belt tension applying member that applies a predetermined tension to the belt, wherein the belt tension applying member does not change a winding angle of the belt with respect to the support roller due to the displacement thereof. A belt device comprising: 4. The belt device according to claim 1, wherein the bending member also serves as the belt tension member. 5. The belt device according to claim 1, wherein the action member is a cleaning member that cleans the outer peripheral surface of the belt. 6. 6. The belt device according to claim 5, wherein the cleaning member is a blade that abuts against the outer peripheral surface of the belt. 6. The belt device according to claim 5, wherein the cleaning member is a fur brush that rotates in contact with the outer peripheral surface of the belt. 5. The belt device according to claim 4, wherein the facing member is disposed at a position that presses the inner peripheral surface of the belt even when the belt is contracted to the maximum and the bending member is displaced toward the outer peripheral surface of the belt. A belt device characterized by. 9. The belt device according to claim 8, wherein the acting member is a rear surface of the belt even when the belt is contracted to the maximum and the bending member is displaced toward the outer peripheral surface of the belt so that the winding angle of the belt with respect to the opposing member is reduced. The belt device is arranged at a position where the facing member contacts. 10. The belt device according to claim 1, wherein the bending member is a roller. The belt device according to claim 1, wherein the facing member is a roller. 12. The belt device according to claim 1, wherein the tension member is a roller. 13. The belt device according to claim 1, wherein the belt conveys a recording medium on which an image is recorded, and transfers an image on an image carrier disposed along the outer peripheral surface of the belt to the recording medium. A belt device which is a transfer conveyance belt. 14. The belt device according to claim 1, wherein an image on an image carrier disposed along the outer peripheral surface of the belt is primarily transferred to the belt, and the primary transferred image is directed toward the outer peripheral surface of the belt. A belt device, which is an intermediate transfer belt for secondary transfer to a fed recording medium. 15. The belt device according to claim 1, wherein the belt, the driving roller, the support roller, the bending member, the belt tension applying member, and the action member are integrally stored in a frame, and the frame is stored in a recording medium. A belt device having a configuration in which it is detachably mounted at a predetermined position of an image forming apparatus for forming an image. 16. The belt transmission device according to claim 15, wherein a driving force of a driving source provided in a main body of the image forming apparatus is transmitted to the driving roller in a state where the frame is mounted at a predetermined position of the image forming apparatus. A belt device characterized by comprising: An image carrier that carries an image, an image forming unit that forms an image on the image carrier, and an endless belt that is driven and rotated by being stretched by a plurality of rollers. An image forming apparatus having a transfer unit that transfers an image formed on a carrier onto a recording medium, wherein the belt apparatus is the belt apparatus according to any one of claims 1 to 16. apparatus. 18. The image forming apparatus according to claim 17, wherein the image forming unit includes a developing device including a plurality of developing units capable of sequentially superposing and forming toner images of different colors on the image carrier. An image forming apparatus. 18. The image forming apparatus according to claim 17, wherein the image carrier and the image forming unit constitute one image forming unit, and a plurality of the image forming units are arranged along the belt of the belt device. An image forming apparatus.