JP5108622B2 - Belt device and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a belt device provided with belt members such as an intermediate transfer belt, a transfer conveyance belt, a transfer belt, and a photosensitive belt. In particular, the present invention relates to a belt apparatus and an image forming apparatus that are configured to be able to be drawn forward with respect to the image forming apparatus main body.

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, a tandem type color image forming apparatus provided with an intermediate transfer belt (belt member) is known (for example, see Patent Document 1).
Specifically, four photosensitive drums (image carriers) are arranged side by side so as to face the intermediate transfer belt (belt member). The four transfer rollers are in pressure contact with the four photosensitive drums via the intermediate transfer belt. On these four photosensitive drums, black (black), yellow, magenta, and cyan toner images are formed, respectively. Then, the toner images of the respective colors formed on the respective photoconductive drums are transferred onto the intermediate transfer belt in an overlapping manner. Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred onto a recording medium as a color image.

In such an image forming apparatus, the intermediate transfer belt device can be pulled forward with respect to the main body of the image forming device so that maintenance of the intermediate transfer belt device (belt device) provided with the intermediate transfer belt can be easily performed. There are many things.
Specifically, in Patent Document 1 or the like, a transfer module in which an intermediate transfer belt is installed is placed on an intermediate transfer belt device (transfer unit). After the intermediate transfer belt device (transfer unit) is pulled forward with respect to the image forming apparatus main body, the transfer module placed on the intermediate transfer belt device can be removed upward.

JP 2004-341087 A

  The above-described image forming apparatus disclosed in Patent Document 1, for example, when the intermediate transfer belt (belt member) is replaced, after the intermediate transfer belt apparatus (belt apparatus) is pulled forward with respect to the image forming apparatus main body, the intermediate transfer belt It was necessary to remove the transfer module placed on the belt device upward. For this reason, the maintainability (maintenance workability) of the intermediate transfer belt device including replacement of the intermediate transfer belt is low.

In order to solve such a problem, the intermediate transfer belt device including the replacement of the intermediate transfer belt can be maintained while the intermediate transfer belt device is pulled forward with respect to the image forming apparatus main body. It is preferable to do.
However, in this case, the state where the intermediate transfer belt device is pulled out from the image forming apparatus main body is continued for a long time, so that the frame of the intermediate transfer belt device is deformed and affects the image quality of the output image. May cause problems. In particular, in a large-sized image forming apparatus, the weight of the intermediate transfer belt apparatus becomes large, and this is a problem that cannot be ignored.
In addition, in a configuration in which most of the outer periphery of the intermediate transfer belt is covered with a frame as in the conventional apparatus, the intermediate transfer belt can be replaced with the intermediate transfer belt apparatus pulled out forward with respect to the main body of the image forming apparatus. I couldn't do it in action.

  The present invention has been made to solve the above-described problems, and provides a belt device and an image forming apparatus that have high maintainability of the apparatus including replacement of a belt member without causing deformation of the apparatus. It is in.

  A belt device according to a first aspect of the present invention is a belt device installed so as to be able to be pulled forward with respect to an image forming apparatus main body, and is an endless belt member supported by a plurality of roller members; Two lateral frames that are outside the outer periphery of the belt member and are respectively held by two slide rails installed in the image forming apparatus main body, and are erected between the two lateral frames at the rear, The rear shafts of the plurality of roller members are rotatably supported and have a box-shaped structure, and the front shafts of the plurality of roller members are rotatably supported, and the belt member is A front frame having a projection surface smaller than an inner periphery, a support frame that cantilever-supports the front frame with respect to the rear frame, the horizontal frame, and the rear frame. While it is installed between both frame near the junction with the arm, but with a reinforcing member formed in a triangular shape, a.

  According to a second aspect of the present invention, in the belt device according to the first aspect, the reinforcing member is disposed so as to be separated from the belt member by 20 mm or more in the height direction. It is.

  According to a third aspect of the present invention, in the belt device according to the first or second aspect of the present invention, the lateral frame is disposed so as to be separated from the belt member by 35 mm or more in the lateral direction. It has been done.

  A belt device according to a fourth aspect of the present invention is the belt device according to any one of the first to third aspects, wherein the support frame is formed in a box shape.

  According to a fifth aspect of the present invention, in the belt device according to the first to fourth aspects, the slide rail is configured so that the device can be pulled out in two stages. .

  A belt device according to a sixth aspect of the present invention is a belt device installed so as to be drawable with respect to the image forming apparatus main body, and an endless belt member supported by a plurality of roller members; A plurality of horizontal frames that are respectively held on a plurality of slide rails outside the outer periphery of the belt member and installed on the image forming apparatus main body; A rear frame that rotatably supports the rear shaft portion of the roller member, and a projection surface that rotatably supports the front shaft portions of the plurality of roller members and that is smaller than the inner periphery of the belt member when viewed from the pulling direction. And a support frame that cantilever-supports the front frame with respect to the rear frame.

  According to a seventh aspect of the present invention, in the belt device according to any of the first to sixth aspects, the rear frame rotatably supports the rear shaft portion of the roller member. A temporary bearing having an inner diameter larger than the outer diameter of the rear shaft portion of the roller member is axially centered from the position of the rear bearing. The front frame is provided with a front bearing that rotatably supports the front shaft portion of the roller member.

  According to an eighth aspect of the present invention, in the belt device according to the seventh aspect, the holding member is supported by the temporary bearing and the front bearing when the holding member is mounted on the rear frame. The roller member includes a tapered portion for guiding the rear shaft portion to the rear bearing, and the rear shaft portion of the roller member is provided with a tapered portion at an end thereof.

According to a ninth aspect of the present invention, there is provided the belt device according to the eighth aspect, wherein the axial distance from the front bearing to the temporary bearing is D1 from the front bearing to the rear bearing. The distance in the axial direction is D2, the clearance between the temporary bearing and the rear shaft portion is δ, and the vertical distance from the inner diameter portion of the rear bearing to the lower end of the tapered portion of the holding member is M1. And when the vertical distance from the upper end to the lower end of the tapered portion of the rear shaft portion is M2,
δ <(D2 / D1) · (M1 + M2)
This relationship is established.

According to a tenth aspect of the present invention, in the belt device according to the eighth or ninth aspect, a vertical direction from the inner diameter portion of the rear bearing to the upper end of the tapered portion of the holding member is provided. When the distance is M3 and the height of the R portion formed in the inner diameter portion of the rear bearing is M4,
M2 + M4> M3
This relationship is established.

  According to an eleventh aspect of the present invention, in the belt device according to any of the seventh to tenth aspects, the roller member has a center of gravity position between the front bearing and the temporary bearing. It was formed as shown in

  A belt device according to a twelfth aspect of the present invention is the belt device according to any of the seventh to eleventh aspects, wherein the rear frame is a positioning member that is positioned with respect to the image forming apparatus main body. The plate-shaped main frame that is installed is joined to a bent subframe, and the holding member is detachably installed on the main frame.

  According to a thirteenth aspect of the present invention, in the belt device according to the twelfth aspect of the present invention, the main frame includes a plurality of studs in which female screw portions for screwing the holding member are formed. The holding member includes a plurality of boss portions that are formed with a hole through which a screw that is screwed into the female screw portion passes and that abuts against end surfaces of the plurality of studs.

  A belt device according to a fourteenth aspect of the present invention is the belt device according to any one of the seventh to thirteenth aspects, wherein the holding member is provided with a drive motor for driving the roller member, A gear train for transmitting the driving force of the drive motor to the rear shaft portion of the roller member is provided.

  According to a fifteenth aspect of the present invention, in the belt device according to the fourteenth aspect, the holding member includes an encoder disk installed on the rear shaft portion of the roller member, and the encoder disk. An opposing encoder sensor is provided internally.

  According to a sixteenth aspect of the present invention, in the belt device according to the fifteenth aspect, the holding member includes a partition member provided between the gear train and the encoder disk.

  A belt device according to a seventeenth aspect of the present invention is the belt device according to any one of the seventh to sixteenth aspects, wherein a seal member is installed between the holding member and the rear frame. .

  The belt device according to the invention of claim 18 is the belt device according to any of claims 7 to 17, wherein the holding member is made of aluminum.

  According to a nineteenth aspect of the present invention, in the belt device according to any of the seventh to eighteenth aspects, the temporary bearing is formed of a low friction material.

  A belt device according to a twentieth aspect of the present invention is a belt device which is installed so as to be drawable with respect to the image forming apparatus main body, and is an endless belt member supported by a plurality of roller members. A holding member holding a rear bearing for rotatably supporting the rear shaft portion of the roller member, and having an inner diameter larger than an outer diameter of the rear shaft portion of the roller member A rear frame provided with a temporary bearing closer to the center in the axial direction than a position of the rear bearing, and a front frame provided with a front bearing rotatably supporting a front shaft portion of the roller member. .

  An image forming apparatus according to a twenty-first aspect of the present invention includes the belt device according to any one of the first to twentieth aspects and the image forming apparatus main body.

  An image forming apparatus according to a twenty-second aspect of the present invention is the image forming apparatus according to the twenty-first aspect, wherein the front frame is fixed to the main body of the image forming apparatus while the belt device is stored in the main body of the image forming apparatus. The fixing member to be attached is detachably installed.

  In the present application, “front” is defined as the side on which the operator pulls out the belt device with respect to the image forming apparatus main body (the front side in the pulling direction). Further, “rear” is defined as a side opposite to “front” and a rear side in the pulling direction of the belt device. Further, the “lateral direction” is defined as a horizontal direction orthogonal to the drawing direction.

  The present invention cantilever the front frame having a projection surface smaller than the inner periphery of the belt member when viewed from the front with respect to the rear frame, and provides strength against the force applied to the apparatus when pulled out from the image forming apparatus main body. Since the efficiency is increased, the belt device and the image forming apparatus can be provided that have high maintainability of the apparatus including replacement of the belt member without causing deformation of the apparatus.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing an image forming unit thereof.
As shown in FIG. 1, an intermediate transfer belt device 15 as a belt device is installed in the center of the image forming apparatus main body 100. Further, image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 (belt member) of the intermediate transfer belt device 15. Yes.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging unit 4Y disposed around the photosensitive drum 1Y, a developing unit 5Y, and a cleaning unit 2Y. , And a static elimination unit (not shown). Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding image is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, the photosensitive drum 1Y is driven to rotate counterclockwise in FIG. 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (in the exposure process). is there.).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing portion 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 (belt member) and the transfer roller 9Y (primary transfer roller), and the toner image on the photosensitive drum 1Y is intermediately transferred at this position. Transferred onto the belt 8 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is collected in the cleaning unit 2Y by the cleaning blade 2a (cleaning). Process.)
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, a laser beam L based on image information is irradiated from the exposure unit 7 disposed above the image forming unit onto the photosensitive drums 1M, 1C, and 1K of the image forming units 6M, 6C, and 6K. Is done. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, referring to FIG. 3, the intermediate transfer belt device 15 (belt device) includes an intermediate transfer belt 8, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, tension rollers 12B and 12C, and a correction roller. 13, the regulation roller 14, the meandering detection unit 80, the abnormality detection unit 88, the photo sensor 90, the intermediate transfer cleaning unit 10, and the like. The intermediate transfer belt 8 is stretched and supported by a plurality of roller members 12A to 12C, 13, and 14, and is endlessly moved in the direction of the arrow in FIG. 3 by the rotational drive of one roller member (drive roller) 12A. .

Four transfer rollers 9Y, 9M, 9C, and 9K (primary transfer rollers) respectively sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form primary transfer nips. Yes. Then, a high voltage (transfer bias) opposite to the polarity of the toner is applied to the transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the tension roller 12B sandwiches the intermediate transfer belt 8 from the secondary transfer roller 19 to form a secondary transfer nip. Then, a high voltage (secondary transfer bias) opposite to the polarity of the toner is applied to the secondary transfer roller 19. As a result, the four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip (secondary transfer step). ). At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is removed.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed. The configuration and operation of the intermediate transfer belt device 15 as a belt device will be described in more detail later with reference to FIGS.

Here, referring to FIG. 1, the recording medium P transported to the position of the secondary transfer nip is fed to the paper feeding unit 26 (or laterally fed) disposed below the apparatus main body 100. From the paper section) via the paper feed roller 27, the registration roller pair 28, and the like.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged out of the apparatus by a pair of discharge rollers (not shown). The transferred P discharged from the apparatus by the pair of paper discharge rollers is sequentially stacked on the stack unit as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the developing unit in the image forming unit will be described in more detail with reference to FIG.
The developing unit 5Y includes a developing roller 51Y that faces the photosensitive drum 1Y, a doctor blade 52Y that faces the developing roller 51Y, two transport screws 55Y disposed in the developer containing unit, and an opening in the developer containing unit. A toner replenishment path 43Y that communicates with each other via a toner density, a density detection sensor 56Y that detects a toner density in the developer, and the like. The developing roller 51Y includes a magnet fixed inside, a sleeve rotating around the magnet, and the like. In the developer accommodating portion, a two-component developer composed of a carrier and toner is accommodated.

The developing unit 5Y configured as described above operates as follows.
The sleeve of the developing roller 51Y rotates in the direction of the arrow in FIG. The developer carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates. Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range.
Thereafter, the toner replenished in the developer accommodating portion circulates through the two separated developer accommodating portions while being mixed and stirred together with the developer by the two conveying screws 55Y (movement in the direction perpendicular to the paper surface of FIG. 2). .) The toner in the developer is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

  The developer carried on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. The developer on the developing roller 51Y is conveyed to a position facing the photosensitive drum 1Y (development area) after the developer amount is made appropriate at this position. The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field formed in the development area. Thereafter, the developer remaining on the developing roller 51Y reaches the upper portion of the developer accommodating portion as the sleeve rotates, and is detached from the developing roller 51Y at this position.

Next, the intermediate transfer belt device 15 (belt device) according to the first embodiment will be described in detail with reference to FIGS.
FIG. 3 is a configuration diagram showing an intermediate transfer belt device 15 as a belt device. FIG. 4 is a schematic view of a part of the intermediate transfer belt device 15 as viewed in the width direction. FIG. 5 is a perspective view showing the vicinity of the meandering detection unit 80 in the intermediate transfer belt device 15. FIG. 6 is a perspective view showing the vicinity of the abnormality detection unit 88 in the intermediate transfer belt device 15.

  3 and 4, the intermediate transfer belt device 15 (belt device) includes an intermediate transfer belt 8 as a belt member, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, a tension roller 12B, 12C, the correction roller 13, the regulation roller 14, the meandering detection unit 80, the abnormality detection unit 88, the photo sensor 90, the intermediate transfer cleaning unit 10, and the like.

  The intermediate transfer belt 8 as a belt member is disposed so as to abut on the photosensitive drums 1Y, 1M, 1C, and 1K (image carriers) as four image carriers that respectively carry toner images of respective colors. . The intermediate transfer belt 8 is stretched and supported mainly by five roller members (the drive roller 12, the tension rollers 12B and 12C, the correction roller 13, and the regulation roller 14).

In the first embodiment, the intermediate transfer belt 8 is made of a single layer or a plurality of layers of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), and the like. In this configuration, a conductive material such as carbon black is dispersed. The intermediate transfer belt 8 is adjusted so that the volume resistivity is in the range of 10 ⁷ to 10 ¹² Ωcm and the surface resistivity on the back side of the belt is in the range of 10 ⁸ to 10 ¹² Ωcm. The intermediate transfer belt 8 is set to have a thickness in the range of 80 to 100 μm. In the first embodiment, the thickness of the intermediate transfer belt 8 is set to 90 μm. The peripheral length of the intermediate transfer belt 8 is set to 2197.5 mm.
If necessary, a release layer can be coated on the surface of the intermediate transfer belt 8. At that time, materials used for the coating are ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four A fluororesin such as fluorinated ethylene-hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
Further, as a method for manufacturing the intermediate transfer belt 8, there are a casting method, a centrifugal molding method, and the like, and a step of polishing the surface is performed as necessary.

  The transfer rollers 9Y, 9M, 9C, and 9K are in pressure contact with the corresponding photosensitive drums 1Y, 1M, 1C, and 1K through the intermediate transfer belt 8, respectively. Specifically, the yellow transfer roller 9Y is pressed against the yellow photosensitive drum 1Y via the intermediate transfer belt 8, and the magenta transfer roller 9M is contacted with the magenta photosensitive drum 1M via the intermediate transfer belt 8. The cyan transfer roller 9C is pressed against the cyan photosensitive drum 1C via the intermediate transfer belt 8, and the black (black) transfer roller 9K is black (black) via the intermediate transfer belt 8. And the photosensitive drum 1K.

The four transfer rollers 9Y, 9M, 9C, and 9K are configured to separate the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K by a contact / separation mechanism (not shown).
Specifically, among the four transfer rollers 9Y, 9M, 9C, and 9K, the three color transfer rollers 9Y, 9M, and 9C are configured to be integrally movable in the vertical direction. Further, the black transfer roller 9K is configured to be movable up and down independently. Then, the four transfer rollers 9Y, 9M, 9C, and 9K move to the positions indicated by the broken lines in FIG. 3, so that the intermediate transfer belt 8 is separated from the photosensitive drums 1Y, 1M, 1C, and 1K (to the positions indicated by the broken lines). It is movement and is the state of FIG. The operation of separating the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K is performed to reduce wear deterioration of the intermediate transfer belt 8, and is mainly performed during non-image formation. . The black transfer roller 9K can be moved up and down independently in the single color mode (when a monochrome image is formed), and the three color transfer rollers 9Y, 9M, and 9C. Is moved downward to separate the color photosensitive drums 1Y, 1M, and 1C from the intermediate transfer belt 8 (the state shown in FIG. 8).

  As described above, in the first embodiment, when the color mode (the mode for forming a color image) is selected, all of the four photosensitive drums 1Y, 1M, 1C, and 1K are operated by the contact / separation mechanism. The intermediate transfer belt 8 is in contact with the intermediate transfer belt 8 (the state shown in FIG. 3). When the single color mode (a mode for forming a single color image) is selected, the intermediate transfer belt 8 is brought into contact with only one photoconductive drum 1K by the contact / separation mechanism, and the other three photoconductors. The drums 1Y, 1M, and 1C are configured to be separated from the intermediate transfer belt 8 (the state shown in FIG. 8).

The drive roller 12A is rotationally driven by a drive motor 70. As a result, the intermediate transfer belt 8 travels in a predetermined traveling direction (clockwise in FIG. 3). The drive motor 70 is a stepping motor and is operated by a drive signal (pulse signal) from the drive 71 controlled by the control unit 72.
One tension roller 12B is in contact with the secondary transfer roller 19 via the intermediate transfer belt 8. Another tension roller 12 </ b> C is in contact with the outer peripheral surface of the intermediate transfer belt 8. An intermediate transfer cleaning unit 10 (cleaning blade) is installed between the tension rollers 12B and 12C.

Here, in the intermediate transfer belt device 15 according to the first exemplary embodiment, a meandering detection unit 80 (detection unit) that detects the displacement of the intermediate transfer belt 8 in the width direction (the vertical direction in FIG. 3) is installed. Has been. Specifically, the meandering detection unit 80 detects the amount of displacement (meandering speed) per unit time in the width direction of the intermediate transfer belt 8.
More specifically, with reference to FIG. 5, the meandering detection unit 80 includes a swinging member 82 that contacts the end in the width direction of the intermediate transfer belt 8, a distance measuring sensor 81 that detects the amount of displacement of the swinging member 82, A spring 83 that urges the moving member 82 in a direction to contact the intermediate transfer belt 8 is formed.

The swing member 82 includes a first arm portion 82a, a rotation support shaft 82b, a second arm portion 82c, and the like. One end of the first arm portion 82a is in contact with the end portion in the width direction of the intermediate transfer belt 8, and the other end is fixed to the rotation support shaft 82b. The rotation support shaft 82b is rotatably supported by the frame of the intermediate transfer belt device 15. One end of the second arm portion 82c is fixed to the rotation support shaft 82b. One end of a spring 83 is connected to the center of the second arm portion 82c. The other end of the spring 83 is connected to the frame of the device 15.
With such a configuration, the swinging member 82 swings following the displacement in the width direction of the intermediate transfer belt 8 (closer to the belt in the direction indicated by the broken line in FIG. 5) (FIG. 5). (It is a swing in the direction of the solid double arrow in the middle) In the first embodiment, the intermediate transfer belt 8 is set to travel at 440 mm / second in the traveling direction (in the direction of the arrow in FIG. 5) during normal operation.

  A distance measuring sensor 81 is installed above the other end of the second arm portion 82c of the swing member 82 (fixed to the frame of the device 15). The distance measuring sensor 81 is mainly composed of a light emitting element (infrared light emitting diode) and a position detecting element (PSD) arranged side by side in the horizontal direction. Infrared light emitted from the light emitting element is reflected by the surface of the second arm portion 82c and enters the position detection element as reflected light. At this time, the incident position of the reflected light incident on the position detecting element changes depending on the distance between the distance measuring sensor 81 and the surface of the second arm portion 82c, and the output value of the light receiving element (ranging sensor 81) is proportional to the change. Changes. Thereby, the amount of displacement in the width direction of the intermediate transfer belt 8 (distance from the surface of the second arm portion 82c) can be detected. Specifically, when the output value of the distance measuring sensor 81 is smaller than a predetermined value (voltage V0), the intermediate transfer belt 8 is displaced in the plus direction with respect to the target position (position displacement to the right in FIG. 5). When the output value of the distance measuring sensor 81 is larger than a predetermined value (voltage V0), the intermediate transfer belt 8 is displaced in the minus direction with respect to the target position (to the left in FIG. 5). This is a displacement of.

In the first embodiment, an abnormal belt shift is also detected (abnormality detection) by the meandering detection unit 80 during normal image formation (during printing) or the like.
Specifically, the belt by the correction roller 13 is set based on the detection result of the meandering detection unit 80, with a belt shift (position shift) of ± 0.5 mm with respect to the target position (position shift 0 mm) as an allowable range (print allowable range). Perform misalignment correction. Then, when the belt shift (position shift) of the intermediate transfer belt 8 is outside the detection range (± 1 mm) of the meander detection unit 80, it is assumed that a relatively large belt shift has occurred, and the apparatus is forcibly stopped. At the same time, the abnormality detection is displayed on the display unit (not shown) of the apparatus main body 100.
In addition to the abnormality detection by the meandering detection unit 80, abnormality detection by the abnormality detection unit 88 is also performed. The reason for detecting the belt-side anomaly in this way is to reliably detect the anomaly even if the meandering detector 80 breaks down or the control software runs away.

Here, in the vicinity of the meandering detection unit 80, a regulating roller 14 that regulates displacement in a direction different from the width direction and the traveling direction of the intermediate transfer belt 8 is installed. Specifically, the regulating roller 14 is close to the contact position between the swing member 82 (first arm portion 82a) and the intermediate transfer belt 8 (upstream in the running direction of the intermediate transfer belt 8 with respect to the contact position). Side.)
With such a configuration, the direction perpendicular to the width direction of the intermediate transfer belt 8 in the meandering detection unit 80 (the contact position between the swinging member 82 and the intermediate transfer belt 8) is the direction perpendicular to the paper surface of FIG. Is reduced. In other words, since the belt tension of the intermediate transfer belt 8 is increased by the restriction roller 14, the displacement of the meandering detection unit 80 in the orthogonal direction is restricted. Therefore, the meandering detection unit 80 detects a displacement component in a direction different from the width direction and the traveling direction in addition to a detection component (a detection component in the width direction) that should be detected originally. It is reduced. That is, the accuracy of detection of the intermediate transfer belt 8 near the belt by the meandering detection unit 80 is improved.

When the displacement (meandering speed) of the intermediate transfer belt 8 is detected by the meandering detection unit 80, the displacement in the width direction of the intermediate transfer belt 8 is corrected by the correction roller 13 (correction means) based on the detection result. .
Here, referring to FIG. 3, the correction roller 13 is on the upstream side in the running direction of the intermediate transfer belt 8 with respect to the photosensitive drums 1 </ b> Y, 1 </ b> M, 1 </ b> C, and 1 </ b> K, and on the inner peripheral surface of the intermediate transfer belt 8. It arrange | positions so that it may contact | connect. Then, referring to FIG. 4, the correction roller 13 swings in the X1 and X2 directions around the swing center 13a by a drive cam (not shown) of the swing mechanism 73 operating at a predetermined angle. It is configured to move.
With this configuration, when the intermediate transfer belt 8 is displaced to the right (belt side) in FIG. 4, the correction roller 13 is swung in the X2 direction by the swing mechanism 73 based on the detection result, and the intermediate transfer belt The displacement correction of the belt 8 is performed. On the other hand, when the intermediate transfer belt 8 is displaced to the left side, based on the detection result, the correction roller 13 is swung in the X1 direction by the swing mechanism 73, and the displacement of the intermediate transfer belt 8 is corrected. As a result, the quality of the color image is deteriorated due to the meandering of the intermediate transfer belt 8, or the intermediate transfer belt 8 is greatly displaced in the width direction (being close to the belt) and comes into contact with other members to cause the intermediate transfer belt 8 to move. Defects etc. that are damaged are suppressed.

In the intermediate transfer belt device 15 according to the first exemplary embodiment, referring to FIG. 4, an abnormality detection unit 88 is installed at a position that is a predetermined distance away from both ends in the width direction of the intermediate transfer belt 8.
As shown in FIG. 6, the abnormality detection unit 88 optically moves the arm member 90 that contacts the intermediate transfer belt 8 that is largely deviated from the belt, and the movement of the arm member about the rotation support shaft 90 b caused by the contact of the intermediate transfer belt 8. An overrun detection sensor 89 (optical sensor) for detecting the position of the arm member 90, a spring 91 for maintaining the posture of the arm member 90, and the like.

  Specifically, referring to FIG. 6, the arm member 90 includes a first arm portion 90 a, a rotation support shaft 90 b, a second arm portion 90 c, and the like. The first arm portion 90a is disposed at a position 5 mm away from the widthwise end portion of the intermediate transfer belt 8 having one end at a normal position, and the other end is fixed to the rotation support shaft 90b. The rotation support shaft 90 b is rotatably supported by the frame of the intermediate transfer belt device 15. One end of the second arm portion 90c is fixed to the rotation support shaft 90b, and the other end is disposed between the light emitting portion 89a and the light receiving portion 89b of the overrun detection sensor 89. One end of a spring 91 is connected to the center of the second arm portion 90c. The other end of the spring 91 is connected to the frame of the device 15. Although not shown, a part of the second arm portion 90 c is in contact with the positioning portion of the frame of the device 15 by the urging force of the spring 91.

With such a configuration, the arm member 90 swings in contact with the intermediate transfer belt 8 when a large belt shift exceeding 5 mm occurs on the intermediate transfer belt 8 (in the direction of the solid arrow in FIG. 6). Oscillating.)
Such a state is detected by the overrun detection sensor 89. That is, the state in which the tip of the second arm portion 90c is separated from the light emitting portion 89a and the light receiving portion 89b is recognized by the light emitted from the light emitting portion 89a being received by the light receiving portion 89b.
When abnormality is detected by the abnormality detection unit 88 (overrun detection sensor 89) in this way, the driving of the intermediate transfer belt 8 (drive roller 12A) is stopped, the photosensitive drums 1Y, 1M, 1C, 1K, and the first. 2 The driving of the transfer roller 19 is stopped, and the photosensitive drums 1Y, 1M, 1C, and 1K and the second transfer roller 19 are forcibly separated from each other. The serviceman call is displayed on the display (the serviceman needs to be repaired).
In the first embodiment, with reference to FIG. 3, the secondary transfer roller 19 is configured to move in a freely detachable manner relative to the intermediate transfer belt 8 (moving in the direction of the arrow). .

  Further, the intermediate transfer belt device 15 according to the first exemplary embodiment is provided with a photo sensor 90 with reference to FIGS. 3 and 4. Here, the photo sensor 90 detects the position and density of the toner image (patch pattern) carried on the intermediate transfer belt 8, and optimizes the image forming conditions. Specifically, the position shift of each color toner image (patch pattern) formed on the intermediate transfer belt 8 through the image forming process described above is optically detected by the photosensor 90, and exposure is performed based on the detection result. The exposure timing of the photosensitive drums 1Y, 1M, 1C, and 1K by the unit 7 is adjusted. Further, the density (toner density) of the toner image (patch pattern) formed on the intermediate transfer belt 8 through the above-described image forming process is optically detected by the photosensor 90 and developed based on the detection result. The toner density of the developer stored in the unit 5 is adjusted.

Hereinafter, the frame configuration of the intermediate transfer belt device 15 and the maintenance method such as replacement of the intermediate transfer belt 8 which are characteristic in the first embodiment will be described in detail with reference to FIGS.
FIG. 9 is a top view illustrating a state in which the intermediate transfer belt device 15 is accommodated in the image forming apparatus 100. FIG. 10 is a top view showing a state in which the intermediate transfer belt device 15 is pulled out from the image forming apparatus 100. FIG. 11 is a top view showing a state in which the intermediate transfer belt device 15 is further pulled out from the image forming apparatus 100. FIG. 12 is a perspective view showing the intermediate transfer belt device 15. FIG. 13 is a schematic view showing the slide rails 140 and 150. FIG. 14 is a perspective view showing the rear frame 110. FIG. 15 is a perspective view showing the support frame 120.

  As shown in FIG. 9, the intermediate transfer belt device 15 is held by the image forming apparatus main body 100 via slide rails 140 and 150 (sliders). The slide rails 140 and 150 are installed outside the outer periphery of the intermediate transfer belt 8 (or outside the intermediate transfer belt device 15) and in the image forming apparatus main body 100. The slide rail includes a holding unit 140 fixed on the apparatus main body 100 side, and a slide rail main body 150 installed to be slidable with respect to the holding unit 140. With such a configuration of the slide rails 140 and 150, as shown in FIG. 10 or FIG. 11, the intermediate transfer belt device 15 is attached to the apparatus main body 100 by an operation of an operator who performs maintenance of the intermediate transfer belt device 15. On the other hand, it is held by the apparatus main body 100 in a state of being pulled forward.

  Referring to FIGS. 9 to 12, the frame (housing) of the intermediate transfer belt device 15 includes two left and right horizontal frames 130, a rear frame 110, a front frame 115, three support frames 120, and a reinforcing frame as a reinforcing member. 125, etc. These frames are formed of a steel material such as stainless steel. Also, welding is mainly used for joining the frames.

  The two horizontal frames 130 are respectively held by slide rails (slide rail main body 150) disposed outside the intermediate transfer belt device 15. The rear frame 110 is fixed to the slide rail (slide rail main body 150) via the horizontal frame 130.

The rear frame 110 is installed between the two horizontal frames 130 on the rear side (upward in FIG. 9). Further, the rear frame 110 rotatably supports shaft portions (rear shaft portions) of the plurality of roller members 12A to 12C, 13, 14A, and 14B via bearings.
Further, the rear frame 110 has a box structure as shown in FIG. Specifically, a flat plate member 110a (main frame) and a plate member 110b (subframe) bent into a U-shape are welded (welding at a welded portion 110c in the drawing) to form a box. A rear frame 110 of the mold structure is formed. Thus, by making the rear frame 110 a box-shaped structure, the torsional strength is increased without increasing the weight of the rear frame 110 so that the deformation of the entire frame can be suppressed.

The front frame 115 is fixed to the rear frame 110 via the support frame 120. The front frame 115 rotatably supports the shaft portions (front shaft portions) of the plurality of roller members 12A to 12C, 13, 14A, and 14B via bearings. That is, both end shaft portions of the plurality of roller members 12A to 12C, 13, 14A, and 14B are rotatably supported by the rear frame 110 and the front frame 115 via the bearings.
Here, the front frame 115 is viewed from the front (the lower side in FIG. 9 and in the pulling direction). The inner periphery of the intermediate transfer belt 8 (the inner periphery of the intermediate transfer belt 8 in a state where the belt tension is released). The projection surface is smaller than 10, the intermediate transfer belt 8 can be inserted and removed without causing the intermediate transfer belt 8 to interfere with the front frame 115 in a state where the intermediate transfer belt device 15 is pulled out from the apparatus main body 100. .
More specifically, the length of the front frame 115 in the longitudinal direction (the left-right direction in FIG. 9) is set shorter than the span connecting the outermost peripheral positions of the drive roller 12A and the correction roller 13. Further, a gap (at least enough for the operator to perform belt replacement work) is provided between the front frame 115 and the horizontal frame 130. Specifically, in the first embodiment, the horizontal frame 130 is in the horizontal direction (in the left-right direction in FIG. 9) with respect to the intermediate transfer belt 8 (the intermediate transfer belt 8 installed in the belt device 15). Is) spaced apart by 35 mm or more. Thereby, the intermediate transfer belt 8 can be easily attached to and detached from the apparatus 15 in the width direction.

Each of the three support frames 120 is disposed so as to support the front frame 115 with respect to the rear frame 110.
Here, one support frame 120 (refer to FIG. 12 is a support frame close to the secondary transfer roller 19) is formed in a box shape as shown in FIG. As a result, the torsional strength is increased without significantly increasing the weight of the support frame 120, and deformation of the entire frame can be suppressed.
Referring to FIG. 15, an electrical component 200 such as a high-voltage power source for applying a bias to the transfer rollers 9Y, 9M, 9C, and 9K is installed inside the box-shaped support frame 120. As a result, when the operator is performing maintenance on the intermediate transfer belt device 15, problems such as damage to the electrical component 200 or electric shock by touching the high-voltage power supply are suppressed.

A reinforcing frame 125 as a reinforcing member is installed between both the frames 110 and 130 in the vicinity of the joint portion between the horizontal frame 130 and the rear frame 110. As a result, the torsional strength of the frame 110 after being bridged between the two horizontal frames 130 is increased, and the joining strength of both the frames 110 and 130 is increased.
Here, the reinforcing frame 125 (reinforcing member) is formed in a substantially triangular shape. Thereby, it functions efficiently as a reinforcing member without greatly reducing the space near the joint between the horizontal frame 130 and the rear frame 110.
In the first embodiment, the reinforcing frame 125 is disposed so as to be separated from the intermediate transfer belt 8 by 20 mm or more in the height direction (in the direction perpendicular to the paper surface of FIG. 9). Accordingly, it is possible to reduce a problem that the intermediate transfer belt 8 interferes with the reinforcing frame 125 and is damaged when the intermediate transfer belt 8 is replaced without increasing the size of the apparatus 15 so much.

  In the first embodiment, the fixing member for fixing the front frame 115 to the image forming apparatus main body 100 in a state where the intermediate transfer belt device 15 is housed in the image forming apparatus main body 100 (the state shown in FIG. 9). The fixed plate 160 is detachably installed. The fixing plate 160 as a fixing member prevents the intermediate transfer belt device 15 from sliding to the front side when the intermediate transfer belt device 15 is not maintained, and cantileverly supports the front frame 115 except during maintenance. In order to improve the strength of the entire frame, the front frame 115 is detachably installed on the front side of the apparatus main body 100 so as to be engaged by screw fastening or the like.

The intermediate transfer belt 8 is pulled forward from the intermediate transfer belt device 15 in the following procedure.
First, the fixing plate 160 (fixing member) is removed from the apparatus main body 100 by the operator. Thereafter, the intermediate transfer belt device 15 is pulled out to the operation side (near side) in a state where the grip portion (not shown) of the intermediate transfer belt device 15 is gripped (the movement in the direction of the white arrow in FIG. 10). 10 is not in a state where the entire intermediate transfer belt device 15 is completely exposed from the apparatus main body 100, but in a state where a part of the intermediate transfer belt device 15 is exposed from the apparatus main body 100 (intermediate transfer belt). 8 is the exposed state.)
Referring to FIG. 10, in the state where the intermediate transfer belt device 15 is pulled out and held, the belt tension is released by the movement of the tension roller 12C. Thereafter, the intermediate transfer belt 8 is pulled out to the operation side (front side) (moving in the direction of the arrow in FIG. 10), and the removal of the belt from the intermediate transfer belt device 15 is completed.
The operation when the new intermediate transfer belt 8 is attached to the intermediate transfer belt device 15 is performed in the reverse order of the above-described removal procedure. As described above, in the first embodiment, the intermediate transfer belt 8 can be exchanged with one action in a state where the intermediate transfer belt device 15 is pulled forward with respect to the image forming apparatus main body 100.
In addition, the above-described attaching / detaching operation of the intermediate transfer belt device 15 is not limited to the replacement operation of the intermediate transfer belt 8, but is performed when jam processing is performed when a jam occurs in the vicinity of the belt device 15. Also done.

Here, in the first embodiment, referring to FIG. 10 and FIG. 11, the slide rails 140 and 150 are configured so that the intermediate transfer belt device 15 can be pulled out in two stages. That is, as shown in FIG. 10, the intermediate transfer belt device 15 pulled out from the apparatus main body 100 can be further pulled out from the apparatus main body 100 (the state shown in FIG. 11).
Specifically, referring to FIG. 13, a spherical engagement member 141 urged by a spring is installed in the slide rail holding portion 140, and a hemispherical groove 151 is formed in the slide rail main body 150 of the slide rail. is set up.

When the intermediate transfer belt device 15 is pulled out from the state shown in FIG. 9, the slide rails 140 and 150 are moved from the state shown in FIG. 13A to the state shown in FIG. 13B (the engaging member 141 is engaged with the groove 151). In this state, the operator feels a click feeling.), And stops in the state shown in FIG. 10 (the first-stage drawing position).
Thereafter, when the intermediate transfer belt device 15 is further pulled out from the state shown in FIG. 10, the slide rails 140 and 150 change from the state shown in FIG. 13B to the state shown in FIG. 13C (the relationship between the engaging member 141 and the groove 151). The operation is shifted to the state of FIG. 11 (the second-stage drawing position). Even in the state of FIG. 11, the engaging member 141 of the holding portion 140 is engaged with a groove portion (not shown) of the slide rail main body 150 so that the operator can feel a click feeling.

Here, the state of FIG. 11 is a state where the entire intermediate transfer belt device 15 is completely exposed from the apparatus main body 100 (a state where the drive motor 70 is exposed). Specifically, in the first embodiment, the distance M between the rear frame 110 and the apparatus main body 100 is set to be about 300 mm.
Referring to FIG. 11, the components such as the drive motor 70 fixed to the rear frame 110 are maintained in a state where the intermediate transfer belt device 15 is pulled out and held.
The operation of attaching the intermediate transfer belt device 15 to the apparatus main body 100 after the maintenance is completed is performed in the reverse procedure to the above-described procedure for pulling out.

  In the first embodiment, as shown in FIGS. 10 and 11, even if the intermediate transfer belt device 15 is pulled out and held and left unattended for a long time, the rear frame 110 on which the torsional load concentrates is box-shaped. In addition to the structure, the reinforcement frame 125 is installed between the rear frame 110 and the lateral frame 130, and the support frame 120 is further shaped like a box, so that deformation of the entire frame can be suppressed. Thereby, it is possible to suppress the deterioration of the image quality of the output image due to the frame deformation of the intermediate transfer belt device 15.

  As described above, in the first embodiment, the front frame 115 having a projection surface smaller than the inner periphery of the intermediate transfer belt 8 (belt member) as viewed from the front is cantilevered with respect to the rear frame 110, and Since the mechanical strength against the force applied to the intermediate transfer belt device 15 (belt device) when it is pulled out from the image forming apparatus main body 100 is efficiently increased, the intermediate transfer belt device 15 is not deformed, and the intermediate transfer belt device 15 is not deformed. Maintenance of the intermediate transfer belt device 15 including replacement of the transfer belt 8 can be improved.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 16 is a configuration diagram showing a main part of the intermediate transfer belt device according to the second embodiment, and is a side sectional view showing the vicinity of the drive roller 12A. FIG. 17 is a diagram illustrating a procedure for assembling the drive roller 12A to the intermediate transfer belt device 15. FIG. 18 is a diagram illustrating the intermediate transfer belt device 15 with the holding member 175 removed. FIG. 19 is an exploded perspective view showing the vicinity of the rear side of the drive roller 12A. FIG. 20 is a diagram illustrating the intermediate transfer belt device 15 in a state where the holding member 175 is mounted. FIG. 21 is a schematic view showing the vicinity of the rear shaft portion 12Ab of the drive roller 12A.
The intermediate transfer belt device 15 according to the second embodiment is different from that of the first embodiment in that a temporary bearing 173 is installed on the rear frame 110.

  Similarly to the first embodiment, the intermediate transfer belt device 15 according to the second embodiment also has an intermediate transfer belt 8, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, and tension rollers 12B and 12C. , The correction roller 13, the regulation roller 14, the meandering detection unit 80, the abnormality detection unit 88, the photo sensor 90, the intermediate transfer cleaning unit 10, and the like (see FIG. 3 and the like). Further, the intermediate transfer belt device 15 in the second embodiment also has two horizontal frames 130, a rear frame 110, a front frame 115, a support frame 120, a reinforcing frame 125, etc., as in the first embodiment. Thus, a frame (housing) is formed and held on the image forming apparatus main body 100 via slide rails 140 and 150 (see FIG. 9 and the like). Further, as described above with reference to FIG. 14, the rear frame 110 is formed in a box-shaped structure by joining a bent subframe 110b to a plate-shaped main frame 110a by welding. . Positioning studs 110d as positioning members for positioning with the image forming apparatus main body 100 are installed on the main frame 110a of the rear frame 110. Specifically, the positioning stud 110d of the rear frame 110 is engaged with a hole (not shown) formed in the housing of the image forming apparatus main body 100, and the intermediate transfer belt device with respect to the image forming apparatus main body 100 is engaged. 15 positions will be determined.

Referring to FIG. 16, drive roller 12 </ b> A as a roller member is rotationally driven by drive motor 70 through gear trains 70 a and 177. As a result, the intermediate transfer belt 8 travels in a predetermined traveling direction (clockwise in FIG. 3). Since the driving roller 12A has a rubber layer formed on the surface thereof, the friction coefficient with the intermediate transfer belt 8 is increased and the intermediate transfer belt 8 can be gripped with certainty.
Since the accuracy (speed stability) of the running speed of the intermediate transfer belt 8 is greatly related to the image quality of the output image, the drive roller 12A is controlled to be driven to rotate at a desired rotation speed. Specifically, referring to FIG. 16, FIG. 19, and FIG. 21, an encoder disk 178 (radial slits are radially formed on the outer peripheral portion) is installed on the rear shaft portion 12Ab of the drive roller 12A, and the rear frame. An encoder sensor 179 (consisting of a light emitting element and a light receiving element) is installed at 110 so as to sandwich the encoder disk 178. Although not shown, an encoder disk is also installed on the shaft portion of the driven roller (one of the plurality of roller members 12A to 12C, 13, and 14 excluding the driving roller 12A). An encoder sensor is installed so as to sandwich the encoder disk. Then, the fluctuation of the pulse output from the encoder sensor facing the encoder disk that rotates with the driven roller is detected and fed back to the input pulse of the drive motor 70 to control the rotational speed of the drive roller 12A. Further, a pulse output from the encoder sensor 179 facing the encoder disk 178 rotating with the drive roller 12A is detected, and from the difference between the detected value and the detected value of the pulse output from the encoder sensor on the driven roller side, The thickness variation of the intermediate transfer belt 8 is obtained, and the rotational speed of the drive roller 12A is corrected and controlled.

Here, referring to FIG. 16 and the like, in the intermediate transfer belt device 15 according to the second embodiment, a holding cover 175 as a holding member holding the rear bearing 172 is detachably installed on the rear frame 110. ing. The rear bearing 172 rotatably supports the rear shaft portion 12Ab of the drive roller 12A. Further, in the rear frame 110, a temporary bearing 173 having an inner diameter larger than the outer diameter (shaft diameter) of the rear shaft portion 12Ab of the drive roller 12A is located in the axially central side of the position of the rear bearing 172 (FIG. 16). It is installed on the right side.)
On the other hand, the front frame 115 is provided with a front bearing 171 that rotatably supports the front shaft portion 12Aa of the drive roller 12A.

With such a configuration, the drive roller 12 </ b> A (roller member) includes the front bearing 171 and the rear bearing 172 at normal times (when the intermediate transfer belt device 15 is attached to the image forming apparatus main body 100). Thus, the intermediate transfer belt device 15 is rotatably supported. On the other hand, when the intermediate transfer belt device 15 is pulled out from the image forming apparatus main body 100 and the holding cover 175 is taken out from the rear frame 110 at the time of maintenance, the driving roller 12A has the front bearing 171 and the temporary bearing. 173 and the intermediate transfer belt device 15. Therefore, even if the intermediate transfer belt device 15 is pulled out from the image forming apparatus main body 100 and the intermediate transfer belt device 15 is cantilevered by the slide rails 140 and 150, the frame is deformed. Since one end (rear shaft portion 12Ab) of 12A is supported by a temporary bearing 173 having a clearance, a problem that an unbalanced load due to frame deformation is applied to the driving roller 12A is suppressed.
That is, when the driving roller 12A is supported by three or more bearings (for example, when a ball bearing having no clearance is installed at the position of the temporary bearing 173), the intermediate transfer belt device 15 is moved to the slide rail 140, during maintenance. If the frame is deformed by being cantilevered by 150, the driving roller 12A is subjected to an unbalanced load accompanying the deformation of the frame, the straightness of the driving roller 12A is reduced, and the coaxiality of a plurality of bearings is lost. End up. As a result, when the intermediate transfer belt device 15 is operated at normal times, the driving roller 12A receives a large stress in the rotation period and breaks in the worst case. On the other hand, when the drive roller 12A is supported by only two bearings without providing the temporary bearing 173, the posture of the drive roller 12A is not stabilized until the two bearings are set on the intermediate transfer belt device 15, and the Assembling workability and maintenance workability of the transfer belt device 15 are deteriorated.
In the second embodiment, since the provisional bearing 173 having a clearance is provided in addition to the front bearing 171 and the rear bearing 172, the assembling workability of the intermediate transfer belt device 15 is improved and the image forming apparatus. Maintenance such as replacement of the driving roller 12A can be easily performed while the intermediate transfer belt device 15 is pulled out from the main body 100.

Hereinafter, a more detailed description will be given with reference to FIGS.
The front shaft bearing 171 and the rear bearing 172 that hold the drive roller 12A in the radial direction during normal operation are ball bearings. The rear bearing 172 is press-fitted into a holding cover 175 (holding member). Further, the drive motor 70 is held by the holding cover 175 by screw fastening. The gear 177 installed on the rear shaft 12 </ b> Ab of the drive roller 12 </ b> A meshes with the drive gear 70 a installed on the motor shaft of the drive motor 70. The distance between the rotation axes of the two gears 70 a and 177 is accurately determined by the holding cover 175. The holding cover 175 is configured to include the gear trains 70a and 177, the encoder disk 178, and the encoder sensor 179 described above, and prevents dust such as toner from entering the gear trains 70a and 177. And the problem that the encoder disk 178 and the encoder sensor 179 become dirty and the detection accuracy decreases.
Further, the holding cover 175 (holding member) is formed of a material having high heat dissipation such as aluminum. Thereby, the heat generated in the holding cover 175 is directly dissipated to the outside of the holding cover 175 or indirectly dissipated through the rear frame 110, and the encoder sensor 179 malfunctions due to heat, Problems such as the rear bearing 172 locking due to heat are suppressed.

The temporary bearing 173 is made of a low friction material such as polyacetal or oil-impregnated sintered metal, and a clearance δ (see FIG. 18) with respect to the rear shaft portion 12Ab of the drive roller 12A is set to about 0.7 mm. ing.
If the clearance δ with respect to the rear shaft portion 12Ab of the drive roller 12A is set large, dust may adhere to the encoder disk 178, the encoder sensor 179, etc. provided in the holding cover 175. If the clearance δ is set small, the above-described effect of installing the temporary bearing 173 may not be sufficiently exhibited. In the second embodiment, considering this, the clearance δ is set to about 0.7 mm.
Further, in consideration of the case where the temporary bearing 173 provided with the clearance is in contact with the rear shaft portion 12Ab, there is a problem even if the temporary bearing 173 functions as a bearing during the operation of the intermediate transfer belt device 15. The temporary bearing 173 is formed of a low-friction material so that no occurrence occurs.

Next, a procedure for assembling the drive roller 12A to the frame of the intermediate transfer belt device 15 at the time of manufacture will be described.
Referring to FIG. 17, first, a front bearing 171 is attached to the frame of the intermediate transfer belt device 15 (the rear frame 110, the front frame 115, the lateral frame 130, the reinforcing frame 125, etc. are joined by welding). After the rear shaft portion 12Ab of the press-fitted drive roller 12A is inserted in the arrow W1 direction, the front bearing 171 is set in the arrow W2 direction to engage with the front frame 115. At this time, the driving roller 12A is only supported on one side by the front bearing 171, and the posture of the driving roller 12A is not fixed and is in an unstable state. Thereafter, a thrust stopper (not shown) that engages with the outer ring of the front bearing 171 is screwed to the front frame 115 to restrict movement of the front bearing 171 in the thrust direction (axial direction).
Thereafter, the temporary bearing 173 is inserted into the rear frame 110 as shown in FIG. As a result, the driving roller 12A has a stable posture within the range of the clearance δ between the temporary bearing 173 and the rear shaft portion 12Ab. In such a state of the driving roller 12A, the posture remains unstable within the range of the clearance δ, but is sufficiently stable to perform the subsequent work.

  In the second embodiment, the center of gravity of the drive roller 12A is configured to be between the front bearing 171 and the temporary bearing 173. When the position of the center of gravity of the drive roller 12A is not between the front bearing 171 and the temporary bearing 173, when the drive roller 12A is supported by the front bearing 171 and the temporary bearing 173, a large load is applied on the front side due to the lever principle. The driving roller 12A is unstablely supported by the bearing 171 and the temporary bearing 173.

  Thereafter, the encoder disk 178 and the gear 177 are installed on the rear shaft portion 12Ab, and the encoder sensor 179 is also attached at this time. Further, as shown in FIG. 19, the drive motor 70 and the holding cover 175 holding the rear bearing 172 are inserted from the rear of the drive roller 12A. Although illustration is omitted, the holding cover 175 is attached to a stud fixed to the main frame 110 a of the rear frame 110.

Here, referring to FIG. 20, the holding cover 175 has the rear shaft portion 12Ab of the driving roller 12A supported by the temporary bearing 173 and the front bearing 171 when the rear cover 110 is mounted on the rear bearing. A taper portion 175a (guide portion) for guiding to 172 is provided. Further, the rear shaft portion 12Ab of the driving roller 12A is provided with a tapered portion 12Ab1 (C surface) at the end thereof.
As shown in FIG. 20, in a state where the holding cover 175 is not attached to the rear frame 110, the drive roller 12 </ b> A is inclined by a clearance δ from the temporary bearing 173. For this reason, when the holding cover 175 is mounted on the rear frame 110, the driving roller 12A must be scooped up by the holding cover 175. In the second embodiment, since the tapered portion 175a is provided in the vicinity of the rear bearing 172 of the holding cover 175 and the tapered portion 12Ab1 is provided at the end of the rear shaft portion 12Ab of the driving roller 12A, By moving 175 in the direction of the white arrow in FIG. 20, a component force in the direction of scooping up the rear shaft portion 12Ab of the drive roller 12A is exerted by the gradient of both the tapered portions 12Ab1, 175a, and the rear shaft portion 12Ab and the rear The side bearing 172 is smoothly engaged.

In order to enable smooth engagement between the rear shaft portion 12Ab and the rear bearing 172, the device is preferably configured as follows.
Referring to FIGS. 16, 18, and 20, the axial distance from the front bearing 171 to the temporary bearing 173 is D1, and the axial distance from the front bearing 171 to the rear bearing 172 is D2. The clearance between the rear shaft portion 12Ab and the rear shaft portion 12Ab is δ, the vertical distance from the inner diameter portion of the rear bearing 172 to the lower end of the taper portion 175a of the holding cover 175 is M1, and the taper portion 12Ab1 of the rear shaft portion 12Ab. When the vertical distance from the upper end to the lower end of M is M2,
δ <(D2 / D1) · (M1 + M2)
The relationship is established. In the above equation, the relationship D1: δ = D2: (M1 + M2) is approximately the relationship between the rear shaft portion 12Ab and the rear bearing 172 under the condition that the distance D1 is extremely larger than the clearance δ. This is a geometrically derived and derived boundary condition for engagement.

Furthermore, when the vertical distance from the inner diameter portion of the rear bearing 172 to the upper end of the tapered portion 175a of the holding cover 175 is M3, and the height of the R portion formed on the inner diameter portion of the rear bearing 172 is M4. In addition,
M2 + M4> M3
It is preferable that the relationship is established. By forming the inner diameter portion (R portion) of the rear bearing 172 in this way, the rear shaft portion 12Ab of the driving roller 12A is scooped up by the taper portion 175a of the holding cover 175, and then the rear shaft portion is mounted on the rear bearing 172. A series of operations until 12Ab is inserted is performed more smoothly.
In the second embodiment, the distance D1 is 417 mm, the distance D2 is 442 mm, the clearance δ is 1 mm, the distance M1 is 2 mm, the distance M2 is 1 mm, the distance M3 is 1 mm, and the distance is related to the above two expressions. M4 is set to 0.3 mm.

Hereinafter, maintenance around the drive roller 12A of the intermediate transfer belt device 15 will be described.
The drive roller 12A is appropriately replaced and maintained due to deterioration of the rubber layer on the surface. Further, when wear deterioration occurs in the gear 177 of the drive roller 12A or when a failure occurs in the encoders 178 and 179, those parts are inspected or replaced.
For example, when exchanging the gear 177, the intermediate transfer belt device 15 is pulled out from the apparatus main body 100 as shown in FIG. 177 is exchanged.
In this way, the intermediate transfer belt device 15 is cantilevered while being pulled out during maintenance. For this reason, the frame of the intermediate transfer belt device 15 is considered so as to maintain a sufficient strength, but a minute deflection still occurs in the frame. This deflection occurs substantially parallel to the axial direction of the drive roller 12A. For this reason, if the clearance δ between the temporary bearing 173 and the rear shaft portion 12Ab is set to 0 (when the driving roller 12A is supported by three bearings), the bearings tend to be separated from each other on the same straight line. Therefore, a large stress is generated in the drive roller 12A, causing fatigue. Therefore, it is necessary to provide an appropriate clearance δ between the temporary bearing 173 and the rear shaft portion 12Ab.

Again, instead of the temporary bearing 173 in the second embodiment, a normal bearing (the clearance δ with the rear shaft portion 12Ab is not provided, and is hereinafter referred to as “medium bearing”). Consider the case where
In this case, the drive roller 12A is fixed by the front bearing 171 and the middle bearing, and the rear bearing 172 is set along the drive roller 12A. Therefore, since the driving roller 12A is fixed by the middle bearing at the time of manufacture, the subsequent assemblability is very good. However, at the time of maintenance, as described above, the three bearings are not aligned in a straight line with the intermediate transfer belt device 15 being pulled out. Therefore, by sufficiently weakening the rigidity of the holding cover 175 that holds the rear bearing 172, It is necessary to consider that the driving roller 12A is not stressed. Further, when the drive roller 12A is replaced with the intermediate transfer belt device 15 pulled out, the rear bearing 172 is fixed on an axial straight line formed by the front bearing 171 and the middle bearing with the frame bent. When the transfer belt device 15 is mounted on the apparatus main body 100 and the deflection of the frame is removed, the three bearings try not to line up in the same straight line. Therefore, unless the stress on the driving roller 12A is released by sufficiently reducing the rigidity of the holding cover 175, the driving roller 12A is subjected to stress every time it rotates, leading to fatigue failure. However, if the holding cover 175 is formed of a low-rigidity material such as resin, various problems such as difficulty in dissipating heat generated by the drive motor 70 or the like occur.
On the other hand, in the second embodiment, the provisional bearing 173 having a sufficient clearance δ is provided in addition to the front bearing 171 and the rear bearing 172, so that there is no side effect and the intermediate transfer belt does not occur. The assembly workability of the apparatus 15 is improved, and maintenance such as replacement of the driving roller 12A can be easily performed while the intermediate transfer belt apparatus 15 is pulled out from the image forming apparatus main body 100.

  Referring to FIG. 21, in the second embodiment, partition member 180 is installed inside holding cover 175 between gear trains 70 a and 177 and encoder disk 178. Specifically, the partition member 180 is a donut-shaped plate member formed of Mylar or the like, and is inserted between the gear 177 and the encoder disk 178 and on the rear shaft portion 12Ab. As a result, even when grease is applied to the tooth surfaces of the gear trains 70a and 177, it is possible to suppress a problem that the grease is scattered and adhered to the encoder disk 178 and the encoder sensor 179 and the detection accuracy of the encoder is lowered. The

  As described above, also in the second embodiment, as in the first embodiment, the front frame 115 having a projection surface smaller than the inner periphery of the intermediate transfer belt 8 (belt member) when viewed from the front is used as the rear frame 110. The intermediate transfer belt device can be supported in a cantilevered manner and the mechanical strength against the force applied to the intermediate transfer belt device 15 (belt device) when it is pulled out from the image forming apparatus main body 100 is efficiently increased. The maintenance of the intermediate transfer belt device 15 including the replacement of the intermediate transfer belt 8 can be improved without causing deformation of the intermediate transfer belt 8.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 22 is a schematic perspective view showing a main part of the intermediate transfer belt device 15 according to the third embodiment, and is a schematic perspective view showing an installation state of the holding member 175 on the rear frame 110. FIG. 23A is a top view showing the installation state of the holding member 175 to the intermediate transfer belt device 15, and FIG. 23B is a view of the holding member 175 as viewed from below in FIG.
In the intermediate transfer belt device 15 according to the third exemplary embodiment, a holding member 175 is installed on the main frame 110 a of the rear frame 110.

The intermediate transfer belt device 15 in the third embodiment is also configured in the same manner as that in the second embodiment.
Here, in the intermediate transfer belt device 15 according to the third exemplary embodiment, the holding cover 175 (holding member) is detachably installed on the main frame 110 a of the rear frame 110. Specifically, referring to FIGS. 22 and 23, four studs 110e each having a female screw portion for fastening the holding cover 175 with screws are fixed to the main frame 110a. On the other hand, the holding cover 175 is formed with four boss portions 175b (projecting toward the stud 100e) that contact the end surface of the stud 110e. The boss portion 175b is formed with a hole portion 175b1 through which a screw 190 screwed into the female screw portion of the stud 110e passes.
A positioning stud 110d as a positioning member for positioning the image forming apparatus main body 100 is also fixed to the main frame 110a of the rear frame 110. Specifically, the positioning stud 110d of the rear frame 110 is engaged with a hole (not shown) formed in the housing of the image forming apparatus main body 100, and the intermediate transfer belt device with respect to the image forming apparatus main body 100 is engaged. 15 positions will be determined.

Here, the main frame 110a of the rear frame 110 is designed such that the positional relationship with the front frame 115 is high in accuracy, and components (for example, various types) where the relative positional relationship with the front frame 115 is important. The roller member or the like is set so that the position is determined by the front frame 115 and the main frame 110a. On the other hand, the sub-frame 110b has a function of strongly supporting the main frame 110a, and is not designed so that the positional relationship with the front frame 115 becomes high in accuracy.
In this way, by installing the holding cover 175 on the main frame 110a via the stud 110e, the positional relationship of the holding cover 175 with respect to the front frame 115 is determined with high accuracy. It will be set with high accuracy.

  Further, in the third embodiment, the holding cover 175 is installed on the main frame 110a by bringing the four boss portions 175b into contact with the end surfaces of the studs 110e of the main frame 110a. With such a configuration, by setting only the flatness of the four boss portions 175b of the holding cover 175 with high accuracy, the main frame can be set without setting the flatness of the entire wide range of the opposed surfaces of the holding cover 175 with high accuracy. The holding cover 175 can be accurately positioned with respect to 110a. Therefore, the yield of the holding cover 175 is increased, and the component cost can be reduced.

In the third embodiment, a seal plate 192 and a sponge seal 193 are installed as a seal member between the holding cover 175 and the rear frame 110.
Specifically, the seal plate 192 as a seal member is formed of a flexible material such as Mylar, and is attached to either the holding cover 175 or the rear frame 110 with a double-sided tape, and the holding cover 175 and the rear frame 110. The floating substance such as toner is prevented from entering from above.
The sponge seal 193 as a seal member is a rectangular annular elastic member formed of foamed polyurethane or the like, and is circumferentially attached to the outer peripheral surface of the facing surface of the holding cover 175 facing the rear frame 110. Thus, foreign matter such as toner is prevented from entering between the holding cover 175 and the rear frame 110.

  As described above, also in the third embodiment, the front frame 115 having a projection surface smaller than the inner periphery of the intermediate transfer belt 8 (belt member) when viewed from the front is used as the rear frame 110 as in the above embodiments. The intermediate transfer belt device can be supported in a cantilevered manner and the mechanical strength against the force applied to the intermediate transfer belt device 15 (belt device) when it is pulled out from the image forming apparatus main body 100 is efficiently increased. The maintenance of the intermediate transfer belt device 15 including the replacement of the intermediate transfer belt 8 can be improved without causing deformation of the intermediate transfer belt 8.

  In each of the above embodiments, the present invention is applied to a belt device (intermediate transfer belt device 15) using the intermediate transfer belt 8 as a belt member. On the other hand, the present invention is also applied to a belt device using a transfer conveyance belt as a belt member (a belt device that transfers a plurality of color toner images onto a recording medium while conveying the recording medium on the belt member). The invention can be applied. The present invention is also applied to a belt apparatus using a transfer belt (which functions as the secondary transfer roller in the present embodiment and is an endless belt-shaped transfer member) as a belt member. can do. Furthermore, the present invention is also applied to a belt device using a photosensitive belt (which functions as the photosensitive drum in the present embodiment and is an endless belt-shaped photosensitive member) as a belt member. can do. In these cases, the same effects as those of the above embodiments can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 2 is a configuration diagram illustrating a belt device installed in the image forming apparatus of FIG. 1. It is the schematic which looked at a part of belt device in the width direction. It is a perspective view which shows a meandering detection part. It is a perspective view which shows an abnormality detection part. FIG. 3 is a schematic diagram illustrating a belt device when an intermediate transfer belt is separated. It is the schematic which shows the belt apparatus at the time of monochromatic mode. FIG. 3 is a top view illustrating a state in which a belt device is accommodated in the image forming apparatus. It is a top view which shows the state which pulled out the belt apparatus. It is a top view which shows the state which pulled out the belt apparatus further. It is a perspective view which shows a belt apparatus. It is the schematic which shows a slide rail. It is a perspective view which shows a rear frame. It is a perspective view which shows a support frame. It is a block diagram which shows the principal part of the belt apparatus in Embodiment 2 of this invention. It is a figure which shows the assembly | attachment procedure of the drive roller to a belt apparatus. It is a figure which shows the belt apparatus of the state from which the holding member was taken out. It is a disassembled perspective view which shows the vicinity of the rear side of a drive roller. It is a figure which shows the belt apparatus of the state with which a holding member is mounted | worn. It is the schematic which shows the vicinity of the rear side shaft part of a drive roller. It is a schematic perspective view which shows the principal part of the belt apparatus in Embodiment 3 of this invention. It is a figure which shows the installation state of the holding member to a belt apparatus.

Explanation of symbols

8 Intermediate transfer belt (belt member),
12A-12C, 13, 14 roller member,
12Aa front shaft, 12Ab rear shaft, 12Ab1 taper,
15 Intermediate transfer belt device (belt device),
100 Image forming apparatus body (apparatus body),
110 back frame,
110a main frame, 110b subframe,
110d positioning stud (positioning member), 110e stud,
115 Previous frame,
120 support frame,
125 Reinforcement frame (reinforcement member),
130 horizontal frame,
140 holding part (slide rail),
150 slide rail body (slide rail),
171 Front bearing,
172 rear bearing,
173 temporary bearings,
175 Holding cover (holding member),
175a taper part, 175b boss part,
178 Encoder disc, 179 Encoder sensor,
180 partition member,
192 Seal plate (seal member), 193 Sponge seal (seal member).

Claims (22)

A belt device installed so as to be able to be pulled forward with respect to the image forming apparatus main body,
An endless belt member supported by a plurality of roller members;
Two lateral frames respectively held by two slide rails installed on the image forming apparatus main body outside the outer periphery of the belt member;
A rear frame that is installed rearward between the two horizontal frames, rotatably supports the rear shafts of the plurality of roller members, and has a box-shaped structure;
A front frame that rotatably supports the front shafts of the plurality of roller members, and has a projection surface that is smaller than the inner periphery of the belt member when viewed from the front,
A support frame that cantilever-supports the front frame with respect to the rear frame;
A reinforcing member that is installed between both the frames in the vicinity of the joint between the horizontal frame and the rear frame, and is formed in a triangular shape,
A belt device comprising:   The belt device according to claim 1, wherein the reinforcing member is disposed so as to be separated from the belt member by 20 mm or more in a height direction.   3. The belt device according to claim 1, wherein the lateral frame is disposed to be separated from the belt member by 35 mm or more in a lateral direction.   The belt device according to claim 1, wherein the support frame is formed in a box shape.   The belt device according to any one of claims 1 to 4, wherein the slide rail is configured so that the device can be pulled out in two stages. A belt device installed so as to be drawable with respect to the image forming apparatus main body,
An endless belt member supported by a plurality of roller members;
A plurality of horizontal frames respectively held on a plurality of slide rails installed on the image forming apparatus main body outside the outer periphery of the belt member;
A rear frame that is installed between the plurality of horizontal frames and rotatably supports rear shafts of the plurality of roller members;
A front frame that rotatably supports front shafts of the plurality of roller members, and has a projection surface that is smaller than the inner periphery of the belt member as viewed from the pull-out direction;
A support frame that cantilever-supports the front frame with respect to the rear frame;
A belt device comprising: The rear frame is detachably provided with a holding member holding a rear bearing for rotatably supporting the rear shaft portion of the roller member, and from the outer diameter of the rear shaft portion of the roller member. A temporary bearing having a larger inner diameter than the position of the rear bearing on the center side in the axial direction,
The belt device according to claim 1, wherein the front frame includes a front bearing that rotatably supports the front shaft portion of the roller member. The holding member includes a taper portion for guiding the rear shaft portion of the roller member supported by the temporary bearing and the front bearing to the rear bearing when mounted on the rear frame. ,
The belt device according to claim 7, wherein the rear shaft portion of the roller member is provided with a tapered portion at an end portion thereof. The axial distance from the front bearing to the temporary bearing is D1, the axial distance from the front bearing to the rear bearing is D2, and the clearance between the temporary bearing and the rear shaft is δ. The vertical distance from the inner diameter portion of the rear bearing to the lower end of the tapered portion of the holding member is M1, and the vertical distance from the upper end to the lower end of the tapered portion of the rear shaft portion is M2. When
δ <(D2 / D1) · (M1 + M2)
The belt device according to claim 8, wherein the following relationship is established. When the vertical distance from the inner diameter portion of the rear bearing to the upper end of the tapered portion of the holding member is M3, and the height of the R portion formed on the inner diameter portion of the rear bearing is M4,
M2 + M4> M3
The belt device according to claim 8, wherein the following relationship is established.   The belt device according to any one of claims 7 to 10, wherein the roller member is formed such that a center of gravity thereof is between the front bearing and the temporary bearing. The rear frame is formed by joining a bent subframe to a plate-like main frame on which a positioning member for positioning with the image forming apparatus main body is installed,
The belt device according to any one of claims 7 to 11, wherein the holding member is detachably installed on the main frame. The main frame includes a plurality of studs formed with female screw portions for screwing the holding member,
The said holding member was provided with the some boss | hub part which contact | abuts the end surface of these studs while the hole part which the screw threadedly engaged with the said female thread part penetrates was formed. Belt device.   The holding member is provided with a drive motor that drives the roller member, and a gear train that transmits a driving force of the drive motor to the rear shaft portion of the roller member. The belt device according to any one of claims 7 to 13.   The belt device according to claim 14, wherein the holding member includes an encoder disk installed on the rear shaft portion of the roller member and an encoder sensor facing the encoder disk.   The belt device according to claim 15, wherein the holding member includes a partition member provided between the gear train and the encoder disk.   The belt device according to any one of claims 7 to 16, wherein a seal member is installed between the holding member and the rear frame.   The belt device according to any one of claims 7 to 17, wherein the holding member is made of aluminum.   The belt device according to any one of claims 7 to 18, wherein the temporary bearing is formed of a low friction material. A belt device installed so as to be drawable with respect to the image forming apparatus main body,
An endless belt member supported by a plurality of roller members;
A holding member holding a rear bearing that rotatably supports the rear shaft portion of the roller member is detachably provided, and a temporary member having an inner diameter larger than the outer diameter of the rear shaft portion of the roller member. A rear frame provided with a bearing closer to the center in the axial direction than the position of the rear bearing;
A front frame including a front bearing that rotatably supports a front shaft portion of the roller member;
A belt device comprising:   21. An image forming apparatus comprising the belt device according to claim 1 and the image forming apparatus main body.   The image forming apparatus according to claim 21, wherein a fixing member for fixing the front frame to the image forming apparatus main body is detachably installed in a state where the belt device is housed in the image forming apparatus main body.

Images