JP6123382B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof.

  In a transfer unit of an image forming apparatus such as a copying machine, a printer, or a facsimile machine, there is known a structure in which a photosensitive member and a transfer member can be contacted and separated to extend the life of a transfer member and a photosensitive member facing the transfer member. Another reason for configuring the photosensitive member and the transfer member to be able to contact and separate is to prevent the transfer member / transfer unit and the photosensitive member from rubbing when the transfer member / transfer unit is detached from the image forming apparatus main body. There is.

  There are configurations in which the photosensitive member and the transfer member can be brought into contact with and separated from each other, such as a configuration in which the photosensitive member is brought into contact with and separated from the transfer member, and a configuration in which the photosensitive member and the transfer member are brought into contact with and separated from each other. In the case of using the driving means, it is known that using a low torque torque is advantageous in terms of cost and size. Further, it is known that the contact / separation torque is affected by the amount of movement of the member to be contacted / separated and the load that the member to be contacted / separated receives from, for example, the transfer belt. As for the belt tension, the larger the contact / separation movement amount, the more the belt is loosened. As a result, the belt tension is reduced, and the problem of slipping and rubbing is likely to occur.

  When using a long belt body, the lubricant and the lubricant are not applied by hand when assembling at the factory, but are applied to the image forming apparatus main body and the photosensitive member and the belt are separated from each other. It is already known that the mechanism is applied to apply the coating. Therefore, in order to satisfy these three conditions, “reducing tension drop as much as possible”, “driving in a state of being separated from the photoconductor”, and “taking sufficient distance from the photoconductor when the unit is attached / detached”, A first position where the photosensitive member and the photosensitive member are in contact, a second position where the belt and the photosensitive member are separated (driven state), and a third position where the belt and the photosensitive member are further separated (when the unit is attached / detached). A contact / separation mechanism configured to have a state) is known.

  However, even if the conventional contact / separation mechanism has the above first to third positions, the transfer member remains in contact with the drum if it is immediately cut off due to machine trouble (jamming or other abnormality). Since it is in the first position and cannot be manually moved from the first position to the third position, there is a problem that, for example, a serviceman may damage the transfer belt or the photoreceptor unit when pulling out the photoreceptor unit or the transfer unit. It was.

  Japanese Patent Application Laid-Open No. 2009-58681 (Patent Document 1) discloses an intermediate transfer belt or a photosensitive member when a transfer unit is attached or detached in the event of an immediate disconnection abnormality such as when the apparatus suddenly stops or when power is suddenly cut off. In order to prevent scratches, a contact / separation configuration is disclosed in which the belt and the photosensitive member can be separated (abutment → separation) by manual contact / separation in the event of an immediate disconnection abnormality.

However, even in this configuration, since the belt cannot be directly moved to the third position without temporarily moving from the first position to the second position, the problem that the belt and the photoconductor are damaged cannot be solved.
The same problem occurs not only in the transfer belt (intermediate transfer belt) in the intermediate transfer system but also in the transfer belt (transfer conveyance belt) in the direct transfer system.

  Accordingly, an object of the present invention is to prevent the photosensitive member and the belt member from being damaged when the image forming apparatus is detached from the main body.

In order to solve this problem, the present invention provides a belt in which an image carrier and a belt member that is stretched around a plurality of roller members and can be rotated are brought into contact with and separated from the image carrier by a contact and separation mechanism. In the image forming apparatus provided with a unit, the belt unit being detachably attached to the apparatus main body, the contact / separation mechanism includes a movable member that is movable to bring the belt body into and out of contact with the image carrier. A first position where the belt member is brought into contact with the image carrier, a second position where the belt member is separated from the image carrier, and the belt member is separated from the image carrier by a larger separation amount than the second position. A lever that can move the moving member from the first position to the third position, and the belt unit moves the moving member by the lever. Move to third position When allowed, Ri removable der the device body, a retention lever that supports the roller member for pressing the belt member to said image bearing member among the plurality of roller members, the belt unit by movement of the moving member The positioning is performed by abutting against a butting portion provided on the frame .
In addition, the present invention includes an image carrier and a belt unit configured such that a belt body that is stretched around a plurality of roller members and can be rotated is brought into contact with and separated from the image carrier by a contact and separation mechanism. In the image forming apparatus in which a belt unit is detachably attached to the apparatus main body, the contact / separation mechanism includes a movable member that moves the belt body to and from the image carrier, and the belt body to the image carrier. A first position for contacting the carrier, a second position for separating the belt from the image carrier, and a third for separating the belt from the image carrier by a larger separation amount than the second position. A lever that can move the moving member from the first position to the third position, and the belt unit moves the moving member to the third position by the lever. When you let the device book A roller member that presses the belt body against the image carrier among the plurality of roller members is supported by a lever member that is pivotally supported by a frame of the belt unit, and is swingable. The contact / separation mechanism has a slider slidably supported on the frame of the belt unit, and the roller member is moved up and down by swinging the lever member by sliding the slider. To do.

  According to the present invention, by moving the moving member of the contact / separation mechanism directly from the first position to the third position by the lever, the belt body can be separated from the image carrier by a larger separation amount than the second position. Therefore, even when an immediate disconnection abnormality occurs, such as when the apparatus suddenly stops or power is suddenly cut off due to a machine trouble, the belt unit can be attached and detached without damaging the belt body and the photoconductor.

1 is a cross-sectional view illustrating a color copying machine of a tandem type intermediate transfer system according to an embodiment of the present invention. FIG. 3 is a diagram schematically illustrating a toner shape. FIG. 3 is a cross-sectional view illustrating a configuration example of an intermediate transfer unit. It is a figure for demonstrating the problem of a prior art. FIG. 4 is a partial perspective view illustrating a configuration example of a contact / separation mechanism in the intermediate transfer unit illustrated in FIG. 3. It is a side view which shows the structure of the back | inner side part of the contact-and-separation mechanism. It is the figure which looked at the lever etc. from the back side of FIG. FIG. 4 is an enlarged view showing a positional relationship between a primary transfer roller holding lever and a stud. It is an enlarged view which shows the positional relationship of a 1st driven roller holding lever and a stud. It is an enlarged view which shows the positional relationship of a 2nd driven roller holding lever and a stud. It is a figure which shows the state which a primary transfer roller and the 1st and 2nd driven roller are located in a 2nd position. It is the figure which looked at the lever etc. from the back side of FIG. It is a figure which shows the state in which a primary transfer roller and the 1st and 2nd driven roller are located in a 3rd position. It is the figure which looked at the lever etc. from the back side of FIG. It is a figure which shows the state which moved the contacting / separating mechanism from the 1st position directly to the 3rd position. It is a perspective view which shows the structural example provided with two contact / separation mechanisms. It is a side view which shows a color contact / separation slider and the member attached to it. It is a fragmentary perspective view which shows the connection part vicinity of a color contact / separation mechanism and a black contact / separation mechanism. It is a front view which shows a part of cover member which covers the front surface of a belt unit. It is a figure which shows the state in which removal of the cover member was controlled.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a tandem type indirect transfer type color copying machine according to an embodiment of the present invention. Note that the present invention is not limited to the intermediate transfer method and can also be applied to a direct transfer image forming apparatus.

  In the figure, reference numeral 100 is a copying machine body, 200 is a paper feed table on which the copying machine body 100 is placed, 300 is a scanner mounted on the copying machine body 100, and 400 is an automatic document feeder (ADF) mounted thereon. is there.

  The copying machine main body 100 is provided with an endless belt-shaped intermediate transfer member 10 (belt member) in the center. In the illustrated example, the intermediate transfer member 10 is wound around three support rollers 14, 15, and 16 and can be rotated and conveyed clockwise in the drawing.

  In the illustrated example, an intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer body 10 after image transfer is provided on the left side of the second support roller 15 among the three rollers. . On the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15, four image forming units 18 of yellow, magenta, cyan, and black are laterally arranged along the conveyance direction. The tandem image forming unit 20 is arranged side by side. The image forming unit 18 is detachably provided as a process cartridge in the apparatus main body. An exposure device 21 is further provided on the tandem image forming unit 20. On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer member 10 from the tandem image forming unit 20. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a sheet.

  A fixing device 25 for fixing the transfer image on the sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. The secondary transfer device 22 described above also has a sheet transport function for transporting the image-transferred sheet to the fixing device 25. Of course, a non-contact charger may be disposed as the secondary transfer device 22, and in such a case, the sheet conveying function is performed by a separate member.

  In the illustrated example, a sheet reversing device 28 for reversing the sheet to record images on both sides of the sheet in parallel with the above-described tandem image forming unit 20 below the secondary transfer device 22 and the fixing device 25. Is provided.

  Now, when making a copy using this color copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the document is pressed by closing the automatic document feeder 400. When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the other contact glass 32. Immediately drives the scanner 300 and travels through the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34 and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.

  When a start switch (not shown) is pressed, one of the support rollers 14, 15 and 16 is rotationally driven by a drive motor (not shown), the other two support rollers are driven to rotate, and the intermediate transfer body 10 is rotated and conveyed. To do. At the same time, the individual image forming means 18 rotates the photosensitive member 40 (image carrying rotating member) to form yellow, magenta, cyan, and black monochrome images on each photosensitive member 40, respectively. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10.

  On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper bank 43 for separation. The paper is separated one by one by the roller 45 and put into the paper feed path 46, conveyed by the transport roller 47, led to the paper feed path 48 in the copying machine main body 100, abutted against the registration roller 49 and stopped. In the case of manual sheet feeding, the sheet feeding roller 50 is rotated to feed out the sheets on the manual tray 51, separated one by one by the separation roller 52, put into the manual sheet feeding path 53, and similarly stopped against the registration roller 49. .

  Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet. The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and heat and pressure are applied by the fixing device 25 to fix the transferred image. And is stacked on the sheet discharge tray 57 or put in the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is also recorded on the back surface. To discharge.

  On the other hand, the intermediate transfer body 10 after image transfer is prepared by the intermediate transfer body cleaning device 17 to remove residual toner remaining on the intermediate transfer body 10 after the image transfer, and to be used again for image formation by the tandem image forming apparatus 20. .

  The intermediate transfer belt 10 is composed of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like in a single layer or multiple layers, such as carbon black. The volume resistivity is adjusted to be in the range of 10 ^ 8 to 10 ^ 12 Ωcm, and the surface resistivity is adjusted to be in the range of 10 ^ 9 to 10 ^ 13 Ωcm. If necessary, a release layer may be coated on the surface of the intermediate transfer belt 10. Materials used for the coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluorocarbon resin), FEP (four-fluorocarbon). Fluorine resin such as ethylene fluoride-propylene hexafluoride copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.

The method of manufacturing the intermediate transfer belt 10 includes a casting method, a centrifugal molding method, and the like, and the surface thereof may be polished if necessary.
If the volume resistivity of the intermediate transfer belt 10 exceeds the above-described range, the bias required for transfer increases, which increases the power supply cost. Further, since the charging potential of the intermediate transfer belt 10 becomes high and the self-discharge becomes difficult in the transfer process, the transfer paper peeling process, etc., it is necessary to provide a static eliminating means. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays quickly, which is advantageous for static elimination by self-discharge, but toner scatter occurs because the current during transfer flows in the surface direction. End up. Therefore, the volume resistivity and surface resistivity of the intermediate transfer belt 10 in the present invention must be within the above ranges.

  The volume resistivity and the surface resistivity were measured by connecting an HRS probe (inner electrode diameter 5.9 mm, ring electrode inner diameter 11 mm) to a high resistivity meter (manufactured by Mitsubishi Chemical Corporation: Hiresta IP). The measured value 10 seconds after applying the voltage of 100V (surface resistivity is 500V) to the front and back of the was used.

The transfer roller is obtained by applying a foamed resin agent to a metal core (iron, SUS, AI, etc.). The thickness of the foamed resin agent is 2 mm to 10 mm, but is not limited thereto.
It is preferable that the shape factor SF-1 of the toner used in the color copying machine of the present embodiment is in the range of 100 to 180, and the shape factor SF-2 is in the range of 100 to 180. FIG. 2 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

  The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

SF-2 = {(PERI) ² / AREA} × (100π / 4) Expression (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

  Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.

  When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered and the cleaning property when attached to the transfer means is also lowered, which is not preferable.

  The toner particle size is preferably in the range of 4 to 10 μm in terms of volume average particle size. When the particle size is smaller than this, it becomes a cause of background stains during development, fluidity is deteriorated, and further, it tends to agglomerate. On the other hand, when the particle size is larger than this, it is impossible to obtain a high-definition image due to toner scattering or resolution deterioration. In this example, a toner having a volume average particle diameter of 6.5 μm was used.

Next, the configuration of the intermediate transfer unit, which is a feature of the present invention, will be described.
In the embodiment, the intermediate transfer member 10 that is an endless belt member wound around a plurality of support rollers is configured to be detachable from the image forming apparatus main body as an intermediate transfer unit. The intermediate transfer unit 1 to be described below is different from the belt body (intermediate transfer body 10) in the tensioned form shown in FIG. 1, but can be applied to the copying machine shown in FIG. The features of the present invention will be described using the intermediate transfer unit 1.

  FIG. 3 is a cross-sectional view illustrating a configuration example of the intermediate transfer unit. In the intermediate transfer unit 1 shown in this figure, an endless belt body 10 includes a driving roller 101, a plurality of driven rollers 102 to 111, a tension roller 112, a plurality of transfer rollers (primary transfer rollers) 113, and a secondary transfer counter roller. 114. The intermediate transfer unit 1 of this example has four types of modes: a full color mode (hereinafter referred to as FC mode), a black mode (hereinafter referred to as Bk mode), a lubricant application mode during standby, and a mode when the unit is attached and detached. Corresponding to the mode, the tensioning form of the belt body 10 can be changed.

  FIG. 3A shows a belt locus in the FC mode. In the FC mode, the belt body 10 is in contact with all the four photoconductors 40. At this time, the four primary transfer rollers 113, the first driven roller 102, the second driven roller 103, and the tenth driven roller 111 are located at a first position where the belt body 10 contacts the photoconductor 40.

  FIG. 3B shows a belt locus in the Bk mode. In the Bk mode, the primary transfer roller 113 (at the right end in the drawing) corresponding to the first driven roller 102, the second driven roller 103, and the black photosensitive member 40K is in contact with the belt member 10 and pushes up the belt member 10 ( However, the three primary transfer rollers 113 and the tenth driven roller 111 other than the black photosensitive member 40K are moved to the second position, and the belt member 10 and the left three photosensitive members 40 are located. (Other than the black photoconductor 40K) is not in contact. The second position is a position where the belt body 10 is separated from the photoreceptor 40.

  FIG. 3C shows a belt locus in the lubricant application mode. In the lubricant application mode, the four primary transfer rollers 113, the first driven roller 102, the second driven roller 103, and the tenth driven roller 111 move to the second position, and the belt body 10 is moved to all the photoconductors 40. It is separated from.

  FIG. 3D shows a belt locus in the unit attachment / detachment mode. In the unit attachment / detachment mode, the four primary transfer rollers 113, the first driven roller 102, the second driven roller 103, and the tenth driven roller 111 are moved to the third position, and the belt body 10 is moved from all the photoconductors 40. It is widely separated. The third position is a position where the belt body 10 is separated from the photoconductor 40 larger than the second position. By moving the roller described above to the third position, the belt body 10 is more sensitive than in the lubricant application mode. Separated from the body 40.

  The belt 10 is brought into contact with and separated from the black photosensitive member 40K by moving the first driven roller 102, the primary transfer roller 113 (for black), and the second driven roller 103. Each roller moves to a first position where the belt member and the photosensitive member contact each other, a second position where the belt member and the photosensitive member are separated from each other, and a third position where the belt member is separated from the photosensitive member larger than the second position. It is the structure to do.

  The contact and separation of the belt 10 with respect to the color photoconductors 40Y, 40M, and 40C are performed by the movement of the tenth driven roller 111 and the three primary transfer rollers 113 (except for black). Each roller moves to a first position where the belt member and the photosensitive member contact each other, a second position where the belt member and the photosensitive member are separated from each other, and a third position where the belt member is separated from the photosensitive member larger than the second position. It is the structure to do.

  Note that the above-described configuration in which the photosensitive member and the belt member are brought into contact with and separated from each other is an example, and is not limited thereto. For example, the number of photoconductors may be one or more, and the number of rollers that perform contact and separation operations is also arbitrary.

Here, the problems of the prior art will be described with reference to FIG. 4 is FIG. 6 of JP 2011-64762 A (Patent Document 2).
As shown in FIG. 4, if two cams (72, 74) are used, a contact / separation configuration in which the roller member can be moved from the first position to the third position can be made. The bracket 81 holding the rollers 91, 62 </ b> K, 75 rotates about the rotation fulcrum 82.

  The first position (a) in FIG. 1 is positioned by the cam 72. Since this position is a contact position, the cam 72 is usually rotated using a drive motor. It may be done manually, but in this case, the life of the photoconductor and transfer member will be extended, which is to be operated by the user each time the contact is put on standby. Since it is not possible to achieve this, a drive motor is usually used.

  In the second position (b), the state shown in FIG. The cam 72 is rotated by the drive motor so that the bracket 81 and the cam 72 are separated, and the bracket 81 is in contact with the cam 74.

  (C) The third position in the figure is positioned by a cam 72 (or both 74 and 72), and the cam 72 is normally rotated by a manual lever or the like. This is because the third position is either when the transfer unit is attached or detached, or when the photosensitive unit is attached or detached, so the frequency is low.

  The problem is that the cam 72 remains in the state shown in FIG. 5 (a) because the drive motor does not rotate in the event of an immediate disconnection abnormality, such as when the device suddenly stops due to an abnormality such as a jam. At this time, even if another cam 74 is rotated, the first position is maintained instead of the third position. Even if the user or service person turns the manual lever to pull out the transfer unit or the photoconductor unit at the time of an immediate disconnection abnormality, the photoconductor and the transfer member are damaged because they remain in the first position.

  Returning to the description of the embodiment, FIG. 5 is a partial perspective view showing a configuration example of the contact / separation mechanism in the intermediate transfer unit 1 shown in FIG. This figure shows a mechanism for contacting and separating a roller member corresponding to the black photosensitive member 40K.

  As shown in FIG. 5, three roller members, a primary transfer roller 113K (for black), a first driven roller 102, and a second driven roller 103, are disposed between the front and rear frames 115F and 115R of the intermediate transfer unit 1. Has been. There are levers for supporting each roller on the front side and the back side. That is, the first driven roller holding levers 116F and 116R for supporting the first driven roller 102, the primary transfer roller holding levers 117F and 117R for supporting the primary transfer roller 113K, and the second driven roller holding lever for supporting the second driven roller 103. 118F, 118R. Each holding lever is rotatably supported by the front and rear frames 115F and 115R. Note that “F” after the symbol represents Front (front), and “R” represents Rear (rear). The contact / separation sliders 119F and 119R (the front contact / separation slider 119F is hidden behind the front frame 115F and cannot be seen) are attached to the front and rear frames 115F and 115R, respectively.

  In the conventional example of FIG. 4 and the like, three (or two) rollers are held by one bracket (the bracket 81 in the example of FIG. 4). ) Lever (bracket). Thereby, the movement amount of each roller can be individually designed by the shape of each roller holding lever or the like. In the conventional integrated type, the distance between the rollers cannot be individually controlled.

  Further, in the embodiment, the first cam 120 and the second cam 121 for moving (moving) the contact / separation sliders 119F and 119R are provided on the back side and the front side (hidden from the front frame 115F and cannot be seen). Reference numeral 122 denotes a drive shaft that rotates the first cam 120. Reference numeral 123 denotes a drive shaft for rotating the second cam 121. The first cam 120 is configured to automatically rotate by a cam drive motor 154. On the other hand, the second cam 121 is configured to be manually rotated by a cam rotation handle 155. The cam drive motor 154 is attached to a bracket 156 that holds the motor and the gear train, and rotates the drive shaft 122 using a timing belt and a pulley to rotate the first cam 120.

  FIG. 6 is a side view showing the configuration of the back side portion of the contact / separation mechanism described in FIG. 5. In FIG. 6, the rear side (R side) portion of the contact / separation mechanism is shown and described, but the same applies to the front side (F side) portion. Hereinafter, description will be given without F and R indicating front and rear.

  Ball bearings 124 and 124 (slider positioning ball bearings) attached to the frame 115 are fitted into two elongated holes provided in the slider 119, so that the slider 119 can slide in the left-right direction in FIG. Yes. Further, the ball bearings 124 and 124 position the slider 119 in the vertical direction. Positioning in the left-right direction is performed by the first cam 120. A slider tension spring 125 is installed on the frame 115 and the slider 119, and the slider 119 urged in the right direction in the drawing hits the first cam 120 (the cam receiving ball bearing 129 attached to the slider 119 is lowered). Positioning in the left-right direction is made by hitting the first cam 120 rotating at the dead point (bottom dead center with respect to the ball bearing 129).

  Between the first driven roller holding lever 116, the primary transfer roller holding lever 117, the second driven roller holding lever 118, and the frame 115, tension springs 126, 127, and 128 are respectively constructed to urge the holding levers. Yes. In FIG. 6, the tension springs 126, 127, and 128 urge each holding lever to rotate counterclockwise in the figure.

  FIG. 6 shows a state in which the primary transfer roller 113 (for black), the first driven roller 102 and the second driven roller 103 are located at the “first position” described above. At this “first position”, the second cam 121 is not in contact with the slider 119. The positioning of the holding levers 116, 117, 118 of each roller in the “first position” will be described with reference to FIG.

  FIG. 7 is a diagram illustrating the positioning of the holding levers 116, 117, and 118 in the “first position”, and is a view of each lever and the like from the back side of FIG. Therefore, the left and right are opposite to those in FIG.

  The first driven roller 102 and the second driven roller 103 are positioned in the vertical direction with the first driven roller holding lever 116 (the slave reference 116a) and the studs 130 and 131 as the abutting portions provided on the transfer frame 115. This is done by the two driven roller holding levers 118 (subordinate reference 118a) abutting each other. The primary transfer roller 113 (for black) and its holding lever 117 are positioned in the vertical direction when the primary transfer roller 113 abuts against the photosensitive member with the belt body 10 (not shown) interposed therebetween.

  In the embodiment, the studs 130 and 131 attached (fixed) to the transfer frame 115 are used as the abutting parts. However, the abutting part is not limited to the studs, and a part of the sheet metal frame is bent as the abutting part. Alternatively, if the frame is made of resin, the abutting portion may be formed integrally with the frame. The shape of the abutting portion is not limited to a cylindrical shape such as a stud, and may be a curved surface or a flat surface. Further, even when a stud is used as the abutting portion, not only a metal but also a resin or other appropriate material can be used. Furthermore, the shape of the stud is not limited to a cylindrical shape, and may be an appropriate shape such as a prismatic shape.

  By positioning the holding lever against the abutting part provided on the frame of the belt unit, (1) There is less stacking of parts and excellent positional accuracy. (2) When the worn and rubbed parts wear over time But there is an effect that the position does not change.

(1) Excellent positional accuracy For example, the positioning of the first driven roller 102 at the “first position” is determined by the holding lever 116. The holding lever 116 is pivotally supported on the transfer frame 115 by a rotation shaft 132 (FIG. 6). The main reference is the rotation shaft 132 provided on the transfer frame 115, and the secondary reference is also an abutting portion provided on the transfer frame 115. Stud 130).

  The positioning of the roller 91 in FIG. 4, which is a conventional example, is determined by the holding bracket 81. The holding bracket 81 is a main reference: a rotation fulcrum 82 provided on the belt unit frame, and a secondary reference: a cam 72 installed on a rotatable shaft provided on the belt unit frame. In this configuration, the sub-reference is increased by one part. In general, the pivotable shaft is installed on the frame via a sliding bearing or a ball bearing. In that case, one more part is added. When the number of sub-standards increases by one or two parts, the part tolerance increases, and the positional accuracy decreases (when compared with the embodiment).

(2) Position does not change over time In many cases, there are parts that rub the moving part. For example, in FIG. 4, which is a conventional example, the cam 72 and the bracket 81 rub. Therefore, one of them is scraped over time, and the position changes. On the other hand, in the present embodiment, since the “first position” used for image formation is positioned by abutment, it is not rubbed and is not easily scraped. Therefore, the position does not change with time. In the “second position” and “third position”, which will be described later, since the parts are rubbed with each other, there is a possibility that the position of the member may change due to scraping, but the second and third positions are not images. Since it is the position at the time of separation, accuracy is not necessary.

  7 are enlarged views for explaining the relationship between the abutting portions provided on the slider 119 and the above-mentioned holding levers. It is shown in FIGS.

  FIG. 8 is an enlarged view showing the positional relationship between the primary transfer roller holding lever 117 for holding the primary transfer roller 113 (for black) and the abutting portion, and corresponds to the “enlarged view B” portion of FIG. A stud 137 as an abutting portion projects from the slider 119, and a hole 117 a of the holding lever 117 is fitted into the stud 137. When the primary transfer roller 113 (and its holding lever 117) is in the first position, the stud 137 is not in contact with the holding lever 117. In the drawing, a gap is opened between the wall surface of the hole 117 a of the holding lever 117 and the stud 137. What is important here is that the stud 137 and the holding lever 117 must not contact at the first position.

  FIG. 9 is an enlarged view showing the positional relationship between the first driven roller holding lever 116 holding the first driven roller 102 and the abutting portion, and corresponds to the “enlarged view C” portion of FIG. A stud 136 as an abutting portion is projected from the slider 119, and the concave portion 116 a of the holding lever 116 is fitted to the stud 136. When the first driven roller holding lever 116 is in the first position, the stud 136 is not in contact with the holding lever 116. In the drawing, a gap is opened between the wall surface of the recess 116 a of the holding lever 116 and the stud 136. What is important here is that the stud 136 and the holding lever 116 must not contact in the first position.

  FIG. 10 is an enlarged view showing the positional relationship between the second driven roller holding lever 118 that holds the second driven roller 103 and the abutting portion, and corresponds to the “enlarged view A” portion of FIG. A stud 138 as an abutting portion projects from the slider 119, and the concave portion 118 a of the holding lever 118 is fitted to the stud 138. When the second driven roller holding lever 118 is in the first position, the stud 138 is not in contact with the holding lever 118. In the figure, a gap is opened between the wall surface of the recess 118 a of the holding lever 118 and the stud 138. What is important here is that the stud 138 and the holding lever 118 must not contact each other in the “first position”.

  The abutting portion provided on the slider 119 is not limited to the studs (137, 138, 139) of the embodiment, and the slider 119 is made of sheet metal, as is the abutting portion provided on the transfer frame 115. If there is, a part thereof may be bent to form an abutting part, or if the slider 119 is made of resin, the abutting part may be formed integrally with the slider. The shape of the abutting portion is not limited to a cylindrical shape such as a stud, and may be a curved surface or a flat surface. Further, even when a stud is used as the abutting portion, not only a metal but also a resin or other appropriate material can be used. Furthermore, the shape of the stud is not limited to a cylindrical shape, and may be an appropriate shape such as a prismatic shape.

FIG. 11 shows a state where the primary transfer roller 113 (for black), the first driven roller 102, and the second driven roller 103 are positioned at the “second position” described above.
The first cam 120 rotates to the top dead center (top dead center with respect to the cam receiving ball bearing 129) and holds the slider 119. That is, the first cam 120 rotates from the position shown in FIG. 6 to the top dead center shown in FIG. 11, thereby pushing the cam receiving ball bearing 129 and moving the slider 119 leftward from the position shown in FIG. When the slider 119 moves leftward from the position shown in FIG. 6, the first driven roller holding lever 116 pivotally supported on the frame 115 by the rotary shaft 132 rotates clockwise in the drawing, and the position shown in FIG. Become. By the rotation of the holding lever 116, the first driven roller 102 moves (lowers) from the “first position” to the “second position”. In this “second position”, the second cam 121 is not in contact with the slider 119 as in the “first position”.

  FIG. 12 is a diagram for explaining the positioning of the holding levers 116, 117, and 118 in the “second position”, in which each lever and the like are viewed from the back side of FIG. Therefore, the left and right are opposite to those in FIG.

  As described above, when the slider 119 moves from the position shown in FIG. 6 to the position shown in FIG. 11, the studs 136, 137, and 138 provided on the slider 119 come into contact with the holding levers 116, 117, and 118, respectively. push. As a result, the levers rotate, the rollers are lowered from the “first position” to the “second position”, and the belt member 10 is separated from the photoreceptor 40.

  At this time, the holding lever 116 (the secondary reference 116a) and the holding lever 118 (the secondary reference 118a) that have been in contact with the studs 130 and 131 in the “first position” are separated from the studs 130 and 131.

  Further, the primary transfer roller 113 is positioned in the vertical direction by abutting against the photosensitive member 40 with the belt member 10 interposed therebetween, but is not in contact with the photosensitive member 40 and the belt member 10 at the “second position”. The stud 137 is positioned by pushing the holding lever 117 and rotating the lever.

Next, the “third position” will be described.
FIG. 13 shows a state in which the primary transfer roller 113 (for black), the first driven roller 102 and the second driven roller 103 are positioned at the “third position” described above.

  When the cam rotation handle 155 (FIG. 5) is manually rotated, the second cam 121 rotates, abuts against and pushes the bracket 139 attached to the slider 119, and moves the slider 119 to the left in the figure. . Compared with the “second position” in FIG. 11, the second cam 121 is not in contact with the bracket 139 at the “second position”, but the second cam 121 rotates and pushes the bracket 139 at the “third position”. You can see how they are. The slider 119 has moved further to the left (left in FIGS. 11 and 13) than the “second position”. When the slider 119 moves further than the “second position”, the holding levers 116, 117, and 118 of the rollers further rotate, and the rollers are positioned further below the “second position”.

  Note that the top dead center of the second cam 121 (top dead center relative to the bracket 139) is a leftward position in FIG. FIG. 13 shows a state of transition from the state of FIG. 11 (“second position”) to the “third position”, and the first cam 120 is rotated to the top dead center. The ball bearing 129 is not in contact. Direct movement from the “first position” to the “third position” will be described later.

  FIG. 14 is a diagram for explaining the positioning of the holding levers 116, 117, and 118 in the “third position”, and is a view of each lever and the like from the back side of FIG. Therefore, the left and right are opposite to those in FIG.

  When the slider 119 moves further than the “second position” (in the right direction in FIG. 14), the studs 136, 137, and 138 provided on the slider 119 come into contact with the holding levers 116, 117, and 118, respectively. Press each lever. As a result, each lever rotates, each roller is lowered to the “third position”, and the belt member 10 is further separated from the photosensitive member 40.

  Since the slider 119 has moved more than the “second position”, the holding levers 116, 117, and 118 are pushed more than in the “second position” and the amount of rotation is larger. In addition, it can be seen that the slider 119 is further moved from the positions of the ball bearings 124 and 124 (slider positioning ball bearings) in the long hole of the slider 119.

Next, direct movement from the “first position” to the “third position” will be described.
Although the “first position” has been described with reference to FIG. 6, as described above, the cam receiving ball bearing 129 of the slider 119 pulled by the spring 125 in the “first position” is at the bottom dead center. It hits the cam 120. On the other hand, in FIG. 15 in which the cam rotation handle 155 (FIG. 5) is manually rotated to directly move from the “first position” to the “third position”, the first cam 120 is the same as in the “first position”. Although it is in the direction (bottom dead center), the cam receiving ball bearing 129 and the first cam 120 are separated from each other. That is, even when the first cam 120 is in the “first position” direction (bottom dead center), the slider 119 is moved “by rotating the second cam 121 manually (by rotating the cam rotation handle 155). It can be moved directly from the “first position” to the “third position”. Thereby, each roller also moves directly from the “first position” to the “third position”.

  In the image forming apparatus of this embodiment, when an immediate disconnection abnormality occurs, for example, when the apparatus suddenly stops due to a machine trouble (jam or other abnormality) or when power is suddenly cut off, the “first position” Each roller that has been in contact with the photoreceptor 40 with the intermediate transfer member 10 (belt member) in between is manually rotated as described with reference to FIG. The intermediate transfer member 10 (belt member) can be exposed to light even when the intermediate transfer unit or the image forming unit (process cartridge) is pulled out or returned from the apparatus main body for abnormal processing. It can be separated from the body 40. Therefore, it is possible to prevent the belt member and the photoconductor from being damaged when being attached and detached. Further, even when the intermediate transfer unit or the image forming unit (process cartridge) is not attached or detached, it is possible to prevent the belt member and the photosensitive member from being damaged when the power is restored or turned on again.

  In the above description, the configuration of the primary transfer roller 113K (for black), the first driven roller 102, and the second driven roller 103 corresponding to the black photoconductor 40K has been described, but the primary corresponding to other color photoconductors. The transfer roller 113 and the tenth driven roller 111 (FIG. 3) can be basically handled with the same configuration.

Next, a configuration example of the contact / separation mechanism corresponding to each photoconductor of a color other than black will be described.
FIG. 16 is a perspective view illustrating a configuration example including two contact / separation mechanisms. The contact / separation mechanism (hereinafter referred to as the black contact / separation mechanism) corresponding to the black photoconductor 40K has already been described above. Therefore, the contact / separation mechanism (hereinafter referred to as color contact / separation mechanism) corresponding to the photoconductors of other colors. (Referred to as a separation mechanism).

The basic structure and operation of the color contact / separation mechanism and the concept of the contact / separation method are the same as those of the black contact / separation mechanism.
In FIG. 16, a collar contact / separation slider 142 is attached to a frame 115R on the back side so as to be slidable in the frame longitudinal direction (parallel to a belt body not shown). The color contact / separation slider 142 is also attached to the frame 115F on the front side, but is not visible because of the back side of the frame. A collar contact / separation motor 140 is mounted on the front surface of the front frame 115F via a bracket 141. The collar contact / separation motor 140 rotates a collar contact / separation cam described later.

  FIG. 17 is a side view showing the collar contact / separation slider 142 and members attached thereto. Basically, it is the same as the slider 119 in the black contact / separation mechanism. In FIG. 17, the back side (R side) portion of the contact / separation mechanism is illustrated and described, but the front side (F side) portion is the same, and will be described below without F and R indicating front and rear.

  Ball bearings 143 and 143 (shown only on one side) attached to the frame 115 are fitted into two elongated holes provided in the collar contact / separation slider 142, so that the slider 142 can slide in the horizontal direction of FIG. It has become. A slider tension spring 144 is installed on the frame 115 and the slider 142. The slider 142 has a cam receiving ball bearing 151. The slider 142 urged rightward in the drawing by the tension spring 144 is positioned in the left-right direction when the cam receiving ball bearing 151 abuts against the collar contact / separation cam 145.

  In the state of FIG. 17 (“first position”), the collar contact / separation cam 145 is rotated to the bottom dead center (bottom dead center with respect to the ball bearing 151), and the collar contact / separation cam 145 has a cam receiving ball bearing. 151 is hitting. The collar contact / separation cam 145 rotates to the top dead center (the top dead center with respect to the cam receiving ball bearing 151) to push the cam receiving ball bearing 151 and move the slider 142 leftward from the position shown in FIG. Move to.

  A primary transfer roller holding lever 147 that holds each primary transfer roller 113 is rotatably supported by a rotation shaft that is implanted in the frame 115. A tension spring 148 is provided between each primary transfer roller holding lever 147 and the frame 115 to urge each holding lever. In FIG. 13, each tension spring 148 urges each holding lever 147 to rotate counterclockwise in the figure.

  The tenth driven roller 111 is held by a driven roller holding lever 149 that is rotatably supported by the frame 115. A tension spring 150 is installed between the driven roller holding lever 149 and the frame 115 to urge the holding lever counterclockwise in the drawing. The driven roller holding lever 149 urged by the tension spring 150 abuts against an abutment reference (not shown) for positioning.

  For positioning the primary transfer roller holding lever 147 and the driven roller holding lever 149 (the primary transfer roller 113 and the tenth driven roller 111) to the “first position”, “second position”, and “third position”, the black contact is used. Since the configuration is exactly the same as that of the separation mechanism, illustration and description are omitted. Since the color contact / separation mechanism is manually set to the “third position” together with the black contact / separation mechanism, this will be described next.

FIG. 18 is a partial perspective view showing the vicinity of the contact portion between the collar contact / separation mechanism and the black contact / separation mechanism and the second cam.
A bracket 139 is mounted near the end of the slider 119 of the black contact / separation mechanism. The second cam 121 comes into contact with the abutting surface 139a of the bracket 139. By manually rotating the second cam 121 with the cam rotation handle 155 (FIG. 5), the black contacting / separating mechanism is The third position.

  A cam abutting surface 142 a is provided at the end of the collar contact / separation slider 142. The cam abutting surface 142a is provided as a surface parallel to the abutting surface 139a of the bracket 139, and is located next to the abutting surface 139a of the bracket 139. The second cam 121 is configured to simultaneously abut against the abutment surface 139a of the bracket 139 and the cam abutment surface 142a of the collar contact / separation slider 142 when rotating, so that both can be pressed.

  With such a configuration, the black contact / separation mechanism and the collar contact / separation mechanism can be simultaneously moved to the “third position” by manually rotating the second cam 121. The black contact / separation mechanism and collar contact / separation mechanism can move both from the “second position” to the “third position” at the same time, or move both from the “first position” directly to the “third position”. It can also be made.

  Furthermore, when one of the black contact / separation mechanism and the color contact / separation mechanism is in the “first position” and the other is in the “second position”, both can be simultaneously moved to the “third position”. For example, when an immediate disconnection abnormality occurs in the black mode (the state of FIG. 3B) in the embodiment, the black contact / separation mechanism at the “first position” and the color contact / separation mechanism at the “second position” Can be simultaneously moved to the “third position”.

  As described above, when an immediate disconnection abnormality occurs, the black contact / separation mechanism and the collar contact / separation mechanism are moved directly from the “first position” to the “third position” so that the rollers supported by these mechanisms are moved to the “first position”. The intermediate transfer member 10 (belt member) can be separated from the photoreceptor 40 by being lowered to “three positions”. Therefore, it is possible to prevent the belt member and the photosensitive member from being damaged when the intermediate transfer unit or the image forming unit (process cartridge) is attached or detached. Further, even when the intermediate transfer unit or the image forming unit (process cartridge) is not attached or detached, it is possible to prevent the belt member and the photosensitive member from being damaged when the power is restored or turned on again.

  The configuration in which the black contact / separation mechanism and the collar contact / separation mechanism are simultaneously moved to the “third position” is not limited to the configuration illustrated here, and any configuration may be used as long as the two sliders 119 and 142 can be pushed by one cam.

  Alternatively, the two sliders 119 and 142 may be pushed using two cams arranged on the same axis. When two cams are used, the amounts of movement of the black contact / separation mechanism and the collar contact / separation mechanism can be made different by making the shapes of the respective cams different.

  By the way, in the image forming apparatus of the embodiment, the belt unit (intermediate transfer unit 1) is detached from an opening (not shown) provided on the front surface of the apparatus main body. And after attaching a belt unit to an apparatus main body, the cover member attached to a main body is provided so that the front surface of a belt unit may be covered. Of course, this cover member is a member that can be attached to and detached from the apparatus main body. In order to attach and detach the belt unit to and from the apparatus main body, it is necessary to remove this cover member from the apparatus main body. In other words, when the cover member is attached to the apparatus main body, attachment / detachment of the belt unit is restricted.

FIG. 19 is a front view illustrating a part of the cover member that covers the front surface of the belt unit.
As shown in this figure, the cover member 160 is provided with an opening 161 through which the cam rotation handle 155 (see also FIG. 5) can pass. However, the opening 161 has a shape that allows the cam rotation handle 155 to pass through only when the cam rotation handle 155 is tilted sideways.

  On the other hand, as shown in FIG. 20, in the state where the cam rotation handle 155 is in the vertical direction (rotated from the state of FIG. 19), the cover member 160 is caught by the cam rotation handle 155, and the cover member 160 is moved. It cannot be removed from the main unit.

  The position (posture) of the cam rotation handle 155 shown in FIG. 20 is the position (posture) of the handle 155 when the above-described holding levers and rollers are in the “first position” or the “second position”. The position (posture) of the cam rotation handle 155 shown in 19 is the position (posture) of the handle 155 when the above-mentioned holding levers and rollers are in the “third position”.

  Therefore, when each roller (and the holding lever) is in the “first position” or the “second position”, the handle 155 interferes with the cover member 160 in the vertical direction, so that the cover member 160 cannot be removed, and the belt Unit attachment / detachment is restricted. Then, when each roller (and the holding lever) is moved to the “third position”, the handle 155 does not interfere with the cover member 160, and the belt unit can be attached and detached by removing the cover member 160. With such a configuration, a foolproof function is provided to prevent contact between the belt member (the intermediate transfer belt 10 in the embodiment) and the image carrier (photosensitive drum 40).

  In the embodiment, the belt member attachment / detachment is restricted and released by the cover member 160. Instead of this, a lock mechanism (such as a claw member) interlocking with the movement of the cam rotation handle 155 is provided. The mechanism may be configured to engage with or disengage from the main body in conjunction with the movement of the cam rotation handle 155, thereby restricting attachment / detachment of the belt unit and releasing the restriction.

  As mentioned above, although this invention was demonstrated based on the example of illustration, this invention is not limited to this. The belt member as the intermediate transfer member can be stretched in an appropriate form. Further, the configuration of the transfer unit or the intermediate transfer unit can be changed as appropriate within the scope of the present invention. The shape of the holding lever that supports each roller is merely an example. The amount of movement of the slider and the amount of movement of each roller can be set as appropriate.

  As the image forming apparatus, any configuration can be adopted as long as the present invention is applicable. The present invention can be applied not only to the intermediate transfer system but also to a direct transfer system. In the case of the direct transfer method, there is a transfer conveyance belt that transfers an image onto a recording medium while conveying the recording medium, and the present invention can be applied to this. In the case of the tandem type, the color order of the image forming unit is arbitrary. The image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile machine, or a multifunction machine having a plurality of functions.

1 Intermediate transfer unit 10 Intermediate transfer belt (intermediate transfer body, belt body)
40 photoconductor (image carrier)
101 Driving roller 102 First driven roller 103 Second driven roller 111 Tenth driven roller 113 Primary transfer roller 115 Frame of intermediate transfer unit 116 First driven roller holding lever 117 Primary transfer roller holding lever 118 Second driven roller holding lever 119 Separation slider 120 First cam 121 Second cam 124 Slider positioning ball bearings 130 and 131 Studs 136 to 138 Stud 140 Collar contact / separation motor 142 Color contact / separation slider 147 Primary transfer roller retention lever 149 Followed roller retention lever 154 Cam drive motor 155 Cam rotation handle

JP 2009-58681 A JP 2011-64762 A

Claims (7)

An image carrier and a belt unit that is configured to be able to contact with and separate from the image carrier by a contact / separation mechanism, and a belt member that is stretched around a plurality of roller members and is rotatable. In the detachable image forming apparatus,
The contact / separation mechanism includes a movable member that is movable to bring the belt body into contact with and separated from the image carrier, a first position where the belt body abuts on the image carrier, and the belt body as the image carrier. A second position for separating the carrier from the carrier and a third position for separating the belt from the image carrier by a larger separation amount than the second position;
The moving member has a lever that can move from the first position to the third position, and the belt unit can be attached to and detached from the apparatus body when the moving member is moved to the third position by the lever. der is,
A holding lever that supports a roller member that presses the belt body against the image carrier among the plurality of roller members is abutted against an abutting portion provided on a frame of the belt unit by the movement of the moving member. An image forming apparatus. An image carrier and a belt unit that is configured to be able to contact with and separate from the image carrier by a contact / separation mechanism, and a belt member that is stretched around a plurality of roller members and is rotatable. In the detachable image forming apparatus,
The contact / separation mechanism includes a movable member that is movable to bring the belt body into contact with and separated from the image carrier, a first position where the belt body abuts on the image carrier, and the belt body as the image carrier. A second position for separating the carrier from the carrier and a third position for separating the belt from the image carrier by a larger separation amount than the second position;
The moving member has a lever that can move from the first position to the third position, and the belt unit can be attached to and detached from the apparatus body when the moving member is moved to the third position by the lever. And
A roller member that presses the belt body against the image carrier among the plurality of roller members is supported by a lever member that is pivotally supported by a frame of the belt unit and is swingable.
The contact / separation mechanism has a slider slidably supported on the frame of the belt unit,
An image forming apparatus, wherein the roller member is moved up and down by swinging the lever member by sliding the slider. Having two contact / separation mechanisms;
The lever, the said movable member in the two separation mechanism, and wherein the movable to the third position at the same time from the first position, the image forming apparatus according to claim 1 or 2. The lever, the moving member, characterized in that it also can be moved to the third position from the second position, the image forming apparatus according to any one of claims 1-3. The lever can move both the moving members to the third position even when one of the moving members in the two contact / separation mechanisms is in the first position and the other is in the second position. The image forming apparatus according to claim 3 or 4 . The image carrier or an image forming unit including the image carrier is detachably provided in the apparatus main body,
And performing detachment of the image bearing member or the image forming unit at the third position, the image forming apparatus according to any one of claims 1-5. A transfer roller disposed so as to be opposed to the image carrier with the belt member interposed therebetween, and provided so as to be movable between a position pressed against the image carrier member and a position separated from the image carrier member; the transcription roller, an image forming apparatus according to any one of claims 1-6, characterized in that for positioning abutted against the image bearing member sandwich the belt member by the movement of the moving member.