JP2015062075A - Image forming apparatus or transfer unit detachable from image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an attachment/detachment direction of a transfer unit from being limited by other members of an image forming apparatus.SOLUTION: An image forming apparatus includes: a first unit having an endless belt stretched by a plurality of stretching members; and a second unit having a cleaning member which comes into contact with the endless belt of the first unit to remove toner on the endless belt. In a transfer unit detachable from the image forming apparatus, the second unit swings with respect to the first unit around a rotation shaft of one of the stretching members of the first unit, and comes into contact with a guide member of the image forming apparatus to change an attitude with respect to the first unit.

Description

  The present invention relates to an image forming apparatus or a transfer unit to which a removable transfer unit is inserted and mounted.

  Conventionally, a toner image formed on a photosensitive drum of a plurality of process cartridges is primarily transferred to an intermediate transfer belt in each primary transfer portion, and the toner image on the intermediate transfer belt is secondarily transferred to a recording medium in a secondary transfer portion. A color image forming apparatus is known.

  In such an image forming apparatus, the toner remaining on the intermediate transfer belt after the secondary transfer is removed by the intermediate transfer belt cleaning device and collected in a waste toner collecting container. A technique has been proposed in which the intermediate transfer belt cleaning device and the intermediate transfer belt are integrated as an intermediate transfer unit so as to be detachable from the image forming apparatus main body (Patent Document 1). Accordingly, waste toner can be collected without leaking, and maintenance work such as repair, inspection, and replacement of the intermediate transfer belt and the intermediate transfer belt cleaning device can be easily performed.

  An image forming apparatus having such an intermediate transfer unit is shown in FIGS. As shown in FIG. 10, the intermediate transfer unit 50 is arranged from one side of the image forming apparatus main body to the other side. In the intermediate transfer unit 50, a plurality of process cartridges 53 are arranged below the intermediate transfer belt 51. Further, in the intermediate transfer unit 50, the intermediate transfer belt cleaning device 52 is integrally fixed to one end portion of the intermediate transfer belt 51 so as to be arranged in parallel with the process cartridge 53. As shown in FIG. 11, an opening 54 is provided on the side where the intermediate transfer belt cleaning device 52 is disposed (on the left side of the apparatus main body in the drawing) so that the intermediate transfer unit 50 can be pulled out. An opening / closing member 55 is provided so as to be openable and closable. Accordingly, the intermediate transfer unit 50 can be pulled out in the horizontal direction from the intermediate transfer belt cleaning device 52 side.

JP 2001-0775374 A

  However, in the image forming apparatus shown in FIGS. 10 and 11, the intermediate transfer unit 50 is integrally fixed with the intermediate transfer belt cleaning device 52 bent with respect to the intermediate transfer belt 51. Therefore, in order to pull out the intermediate transfer unit 50 from the apparatus main body, it can be pulled out only from the intermediate transfer belt cleaning device 52 side so as not to interfere with the process cartridge 53. In other words, the intermediate transfer unit 50 in which the two units are integrated is an opening that automatically draws out the arrangement of the intermediate transfer belt cleaning device 52 that is the other unit with respect to the intermediate transfer belt 51 that is one unit. The arrangement of the part 54 is also determined. For this reason, the degree of freedom in design is limited by the arrangement of the intermediate transfer belt cleaning device 52.

  An object of the present invention is to prevent other members of the image forming apparatus from limiting the attaching / detaching direction of the transfer unit.

  To achieve the above object, the present invention provides a first unit including an endless belt stretched by a plurality of stretch members, and a toner on the endless belt in contact with the endless belt of the first unit. A transfer unit detachably attached to the image forming apparatus, wherein the second unit includes a plurality of stretching members provided in the first unit. One of the stretching members is swingable with respect to the first unit around the rotation axis, and changes the posture with respect to the first unit by contacting a guide member provided in the image forming apparatus. Is possible.

  According to the present invention, since the second unit of the transfer unit can swing, it is possible to make the transfer unit attach / detach direction unrestricted by another member of the image forming apparatus.

Schematic sectional view of the image forming apparatus Cross section of intermediate transfer unit Perspective view of intermediate transfer unit Top view of the intermediate transfer unit Front view of intermediate transfer unit A perspective view showing a mounting portion of the intermediate transfer unit Perspective view showing the mounting operation of the intermediate transfer unit Sectional view showing completion of mounting of intermediate transfer unit Sectional view showing completion of mounting of intermediate transfer unit Sectional drawing of the image forming apparatus which concerns on a prior art example The perspective view of the image forming apparatus which concerns on a prior art example

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

  An image forming apparatus having a detachable transfer unit will be described with reference to FIGS. In the following description, first, the overall configuration of the image forming apparatus will be described with reference to FIG. Next, the configuration of the primary transfer unit will be described with reference to FIGS. Next, the operation of mounting the primary transfer unit to the apparatus main body will be described with reference to FIGS. Finally, the positioning of the primary transfer unit to the apparatus main body will be described with reference to FIGS.

(Overall configuration of image forming apparatus)
First, the overall configuration of the image forming apparatus will be described with reference to FIG. An image forming apparatus 100 shown in FIG. 1 includes four process cartridges arranged in parallel with an inclination with respect to the horizontal direction. Each of the process cartridges 7 (7a to 7d) includes an electrophotographic photosensitive drum 1 (1a to 1d) as one image carrier.

  The electrophotographic photosensitive drum (hereinafter referred to as “photosensitive drum”) 1 is driven to rotate clockwise in FIG. 1 by a driving member (not shown). Around the photosensitive drum 1, the following process means 2, 3, 4, 5, 6 acting on the photosensitive drum are arranged in order according to the rotation direction. That is, the charging roller 2 (2a to 2d) for uniformly charging the surface of the photosensitive drum 1, the developing unit 4 (4a to 4d) for developing the electrostatic latent image using toner as a developer, and the post-transfer A cleaning member 6 (6a to 6d) for removing toner remaining on the surface of the photosensitive drum 1 is disposed. Further, a laser unit is irradiated on the basis of the image information to form an electrostatic latent image on the photosensitive drum 1, and four color developer (hereinafter referred to as “toner”) images on the photosensitive drum 1 are formed. An intermediate transfer belt 5 that is collectively transferred is disposed. Here, the photosensitive drum 1, the charging roller 2, the developing unit 4, and the cleaning member 6 are integrally formed as a cartridge to constitute a process cartridge 7 that can be attached to and detached from the mounting portion of the image forming apparatus.

  The intermediate transfer belt 5 is stretched around a driving roller 10, a tension roller 11, and a secondary transfer counter roller 33. Further, a primary transfer roller 12 (12a to 12d) is disposed inside the intermediate transfer belt 5 so as to face each of the photosensitive drums 1 (1a to 1d), and a transfer bias is applied by a bias applying unit (not shown). Is applied.

  In the toner image formed on the photosensitive drum 1, each photosensitive drum 1 rotates in the arrow Q direction, the intermediate transfer belt 5 rotates in the arrow R direction, and a positive bias is applied to the primary transfer roller 12. As a result, primary transfer is sequentially performed on the intermediate transfer belt 5. Then, the four-color toner images are conveyed to the secondary transfer unit 15 in a state where the intermediate transfer belt 5 is overlaid.

  On the other hand, the toner remaining on the surface of the photosensitive drum 1 after the toner image transfer is removed by the cleaning member 6, and the removed toner is collected in a removed toner chamber in the photosensitive unit 26 (26a to 26d).

  In synchronization with the image forming operation, a sheet as a recording medium is conveyed by a conveying unit including the feeding device 13 and the registration roller pair 17. The feeding device 13 includes a feeding cassette 24 that stores the sheet S, a feeding roller 8 that feeds the sheet S, and a conveyance roller pair 16 that conveys the fed sheet S. The feeding cassette 24 is configured so that it can be pulled out toward the front of the apparatus in FIG. After the user pulls out the feeding cassette 24 and removes it from the apparatus main body, the sheet supply is completed by setting the sheet S and inserting it into the apparatus main body. The sheets S stored in the feeding cassette 24 are pressed against the feeding roller 8, separated one by one by the separation pad 9 (friction piece separation method), and conveyed by the conveying roller pair 16.

  Then, the sheet S conveyed from the feeding device 13 is conveyed to the secondary transfer unit 15 by the registration roller pair 17. In the secondary transfer unit 15, a positive bias is applied to the secondary transfer roller 18, whereby the four color toner images on the intermediate transfer belt 5 are secondarily transferred to the conveyed sheet S.

  The toner remaining on the intermediate transfer belt 5 after the secondary transfer to the sheet S is removed by the transfer belt cleaning device 23, and the removed toner passes through a waste toner conveyance path (not shown) and reaches the back surface portion of the device. The waste toner is collected into a disposed waste toner collecting container (not shown).

  On the other hand, the fixing device 14 as a fixing unit applies heat and pressure to the toner image formed on the sheet S and fixes the toner image. The fixing belt 14a has a cylindrical shape and is guided by a belt guide member (not shown) to which heat generating means such as a heater is bonded. The fixing belt 14a and the pressure roller 14b form a fixing nip with a predetermined pressure contact force.

  Then, the sheet S on which the unfixed toner image conveyed from the image forming unit is formed is heated and pressed at the fixing nip between the fixing belt 14a and the pressure roller 14b, and the unfixed toner image on the sheet S is heated. Is established. Thereafter, the fixed sheet S is discharged to the discharge tray 20 by the discharge roller pair 19.

(Configuration of primary transfer unit)
Next, the configuration of the intermediate transfer unit 101 as the primary transfer unit will be described with reference to FIGS. 2 is a schematic sectional view of the intermediate transfer unit 101, FIG. 3 is a perspective view of the intermediate transfer unit 101, FIG. 4 is a top view of the intermediate transfer unit 101, and FIG. 5 is a front view of the intermediate transfer unit 101.

  The intermediate transfer unit 101 is a detachable unit in which a transfer belt unit 25 that is a first unit and a transfer belt cleaning device 23 that is a second unit that operates in contact with the transfer belt unit 25 are integrally provided. The intermediate transfer unit 101 is detachably attached to the image forming apparatus main body.

  Here, the transfer belt unit 25 includes an intermediate transfer belt 5 that is an endless belt that is stretched by a driving roller 10 that is a plurality of stretching members, a tension roller 11, and a secondary transfer counter roller 33. Further, the transfer belt unit 25 includes four primary transfer rollers 12 (12 a to 12 d) provided at positions facing the respective photosensitive drums 1 via the belt 5.

  As shown in FIG. 2, the transfer belt cleaning device 23 has a cleaning blade 31 as a cleaning member that contacts the intermediate transfer belt 5 and scrapes off residual toner on the intermediate transfer belt 5 (on the endless belt). The transfer belt cleaning device 23 includes a cleaning blade support plate 32 for maintaining the posture of the cleaning blade 31, and a blade pressure spring 34 for pressing the cleaning blade 31 against the intermediate transfer belt 5. Further, the transfer belt cleaning device 23 includes a screw 35 for sending the residual toner removed from the intermediate transfer belt 5 to a collection container.

  The transfer belt cleaning device 23 is provided so as to be able to swing with respect to the transfer belt unit 25 about an axis line in a direction orthogonal to the insertion direction. Specifically, as shown in FIGS. 3 and 4, the transfer belt cleaning device 23 is swingably supported by the transfer belt unit 25 with the shafts 11 a and 11 b of the tension roller 11 as fulcrums. That is, the transfer belt cleaning device 23 is centered on the shafts (rotating shafts) 11a and 11b that are the rotation centers of the tension roller 11 located on the innermost side in the unit insertion direction among the plurality of stretching members of the transfer belt unit 25. To swing. As shown in FIG. 5, the posture of the transfer belt cleaning device 23 with respect to the transfer belt unit 25 is different before and after the image forming apparatus main body is mounted. As for the posture of the transfer belt cleaning device 23 with respect to the transfer belt unit 25, the posture shown by the broken line in FIG. 5 is the first posture A at the start of insertion (before attachment), and the posture shown by the solid line in FIG. The second posture B after mounting).

  As shown in FIG. 4, the transfer belt cleaning device 23 is provided with positioning bosses 36 a and 36 b for determining the posture when the transfer belt cleaning device 23 is attached to the apparatus main body 100. The transfer belt unit 25 is provided with guided portions 37 a and 37 b when the intermediate transfer unit 101 is attached to the apparatus main body 100. In FIG. 4, 10a and 10b are drive roller shafts, and 10c and 10d are drive roller bearings attached to the drive roller shaft. The positioning bosses 36a and 36b of the transfer belt cleaning device 23, the guided portions 37a and 37b of the intermediate transfer unit 101, and the tension roller shafts 11a and 11b are guided members guided by guide members in the apparatus main body, which will be described later. is there. These guided members are respectively provided on both sides in a direction orthogonal to the insertion direction of the intermediate transfer unit 101.

(Mounting operation of the primary transfer unit to the main unit)
Next, a mounting operation when mounting the intermediate transfer unit 101 to the apparatus main body 100 will be described with reference to FIGS. FIG. 6 is a perspective view showing a mounting portion mounted on the apparatus main body 100 of the intermediate transfer unit 101. FIG. 7 is a perspective view showing a state in which the intermediate transfer unit 101 is mounted on the apparatus main body 100.

  The intermediate transfer unit 101 is configured to be detachable from the apparatus main body 100. By adopting such a configuration, maintenance work such as repair, inspection, and replacement of the intermediate transfer belt 5 or the transfer belt cleaning device 23 can be performed with a simple operation, so that the usability of the apparatus main body 100 is improved. Can be made.

  Further, in order to reduce the size of the apparatus main body 100 in the horizontal direction and to reduce the size of the apparatus main body 100, the process cartridge 7 is disposed obliquely with respect to the horizontal direction as shown in FIG. In accordance with the arrangement of the cartridge 7, the intermediate transfer unit 101 is also arranged obliquely with respect to the horizontal direction.

  The mounting direction of the intermediate transfer unit 101 with respect to the apparatus main body 100 is the arrow F direction shown in FIG. In the following description, the right side of the apparatus main body 100 shown in FIG. 1 is the front side in the mounting direction of the primary transfer unit, and the left side is the back side in the mounting direction.

  As shown in FIGS. 6 and 7, the image forming apparatus 100 includes an open / close member 38 that covers an opening (insertion opening) 45 for inserting the intermediate transfer unit 101 into the apparatus main body 100.

  When the intermediate transfer unit 101 is attached to the apparatus main body 100, the opening / closing member 38 is first opened. Although not shown, the secondary transfer roller 18 is provided on the opening / closing member 38 and moves together with the opening / closing member 38. The opening / closing member 38 forms a part of the outer appearance surface of the apparatus main body 100. When the opening / closing member 38 is opened, it is possible to remove the jammed sheet S from the opened opening 45, and the fixing device can be attached and detached. The opening / closing direction of the opening / closing member 38 can be opened / closed in the vertical direction, but may be configured to be openable / closable in the horizontal direction.

  When the opening / closing member 38 is opened, the attachment portion 39 of the intermediate transfer unit 101 attached to the apparatus main body 100 is exposed inside the apparatus main body 100 together with the sheet S conveyance path and the registration roller pair 17.

  As shown in FIG. 6, mounting guides 40 and 41 extending diagonally upward from the right side to the left side of the apparatus main body 100 are provided on the front side and the back side of the apparatus main body 100 of the mounting portion 39. The mounting guides 40 and 41 are guide members for guiding the intermediate transfer unit 101 inserted into the mounting portion 39 from the opening 45.

  Then, the intermediate transfer unit 101 is guided while the positioning bosses 36a and 36b, the tension roller shafts 11a and 11b, and the guided portions 37a and 37b of the intermediate transfer unit 101 are sequentially guided by the front and back mounting guides 40 and 41, respectively. Is inserted in the direction of arrow F. After the intermediate transfer unit 101 is inserted to a predetermined insertion position inside the apparatus main body 100, the opening / closing member 38 is closed to complete the mounting of the intermediate transfer unit 101.

(Positioning of the primary transfer unit to the main unit)
Next, the positioning of the intermediate transfer unit 101 with respect to the apparatus main body 100 will be described in more detail with reference to FIGS.

  In the following description, positioning of the intermediate transfer unit 101 on the front side of the main body with respect to the mounting guide 40 on the front side of the apparatus main body 100 will be described. A mounting guide 41 and a guided member of the front side and the target shape are also provided on the back side of the main body of the apparatus main body 100 and the intermediate transfer unit 101, and the intermediate transfer unit 101 is inclined on the front side and the back side of the apparatus main body. It is configured to be installed without any problems.

  Before the intermediate transfer unit 101 is mounted, the transfer belt cleaning device 23 for the intermediate transfer belt unit 25 maintains the first posture on a substantially straight line so that the bottom surface of the unit is substantially flat as shown in FIGS. It is energized as follows.

  As shown in FIG. 8, the mounting guide 40 provided in the mounting portion 39 of the apparatus main body 100 is in order from the upstream side toward the downstream side in the insertion direction, the first guide portion 40b, the second guide portion 40d, and the third guide. It has a portion 40f. The three guide portions are formed such that the width in which the mounting guide 40 sandwiches each guided member narrows stepwise toward the downstream side in the insertion direction. Among these, the second guide portion 40d is narrower than the first guide portion 40b and has a width for fitting the tension roller shaft 11a. The third guide portion 40f is narrower than the second guide portion 40d and has a width for fitting the positioning boss 36a.

  When the intermediate transfer unit 101 is attached to the apparatus main body 100, the positioning boss 36a of the transfer belt cleaning device 23 is first aligned with the inlet 40a of the attachment guide 40 as shown in FIG. Then, when the intermediate transfer unit 101 is inserted in the direction of the arrow F with the positioning boss 36 a along the lower surface of the first guide portion 40 b of the mounting guide 40, the tension roller shaft 11 a is then moved to the first guide of the mounting guide 40. Guided by the portion 40b. When the intermediate transfer unit 101 is further pushed in the direction of arrow F, the guided portion 37 a of the intermediate transfer belt unit 25 is guided by the first guide portion 40 b of the mounting guide 40.

  If the intermediate transfer unit 101 is continuously pushed in the direction of arrow F, the positioning boss 36a of the transfer belt cleaning device 23 reaches the bent portion 40e of the second guide portion 40d of the mounting guide 40. Thereafter, as shown in FIG. 8, the positioning boss 36a is guided by the second guide portion 40d of the mounting guide 40, and the transfer belt cleaning device 23 gradually swings around the tension roller shaft 11a to start changing its posture. .

  Then, immediately before the intermediate transfer unit 101 is completely attached to the apparatus main body 100, as shown in FIG. 9, the drive roller bearing 10c attached to the drive roller shaft 10a contacts the lock lever 43 provided on the apparatus main body 100. Reach position.

  The lock lever 43 is provided on the apparatus main body 100 side and rotates around a rotation center 43a. The lock lever 43 is biased in the direction of arrow G by the lock lever spring 44 around the rotation center 43a.

  If the intermediate transfer unit 101 is further pushed in the direction of arrow F after the drive roller bearing 10c reaches a position where it contacts the lock lever 43, the lock lever 43 receives a force from the drive roller bearing 10c and is in a direction opposite to the arrow G direction. Retract while rotating. When the drive roller bearing 10c passes the apex 43b of the lock lever 43, the lock lever 43 rotates in the direction of arrow G along the drive roller bearing 10c by the urging force of the lock lever spring 44.

  When the drive roller bearing 10c hits the positioning portion 42 provided in the apparatus main body 100, the intermediate transfer unit 101 stops and the mounting is completed. The lock lever 43 fixes the intermediate transfer unit 101 to the apparatus main body 100 while pressing the drive roller bearing 10 c against the positioning portion 42.

  At this time, the tension roller shaft 11a reaches the second guide portion 40d of the mounting guide 40 and is in a fitted state in a direction substantially perpendicular to the mounting direction of the intermediate transfer unit 101. Thereby, the position of the intermediate transfer belt unit 25 in the intermediate transfer unit 101 is determined. Further, the transfer belt cleaning device 23 is brought into a fitted state when the positioning boss 36 a reaches the third guide portion 40 f of the mounting guide 40. As a result, the transfer belt cleaning device 23 stops swinging about the tension roller shaft 11a as the center of rotation and finishes changing to a second posture different from the first posture before mounting, as shown in FIG. The position is determined. In this way, the transfer belt unit 25 and the transfer belt cleaning device 23 that form the intermediate transfer unit 101 are each positioned in the apparatus main body 100 by the mounting guide 40 (41).

  As described above, the intermediate transfer unit 101 is integrated with the transfer belt unit 25 so that the transfer belt cleaning device 23 can swing. As a result, the posture of the transfer belt cleaning device 23 with respect to the transfer belt unit 25 changes in accordance with the mounting guides 40 and 41 in the intermediate transfer unit 101 during the mounting process. For this reason, the mounting / removal direction of the intermediate transfer unit 101 and the position of the opening are not limited by the arrangement relationship between the two integrated units 23 and 25. Furthermore, the attaching / detaching direction of the intermediate transfer unit 101 is not limited by a member such as a process cartridge in the apparatus. Thereby, the freedom degree of design improves.

  Further, by using the intermediate transfer unit 101 in which the transfer belt cleaning device 23 is swingably integrated with respect to the transfer belt unit 25, the intermediate transfer unit 101 can be pulled out from the transfer belt unit 25 side. As a result, the opening / closing member 38 of the opening for attaching / detaching the unit can be used as an opening / closing member for jamming the sheet S and an opening / closing member for replacing the fixing device.

  In the above-described embodiment, four process cartridges that can be attached to and detached from the image forming apparatus main body are used. However, the number of the process cartridges is not limited, and may be set as necessary. Further, the guide member is not limited to the rail-shaped member as described above, and may be another member that changes the posture of the second unit relative to the first unit, such as a protrusion inside the apparatus main body.

  In the above-described embodiment, a process cartridge including a photosensitive drum and a charging unit (charging roller 2), a developing unit (developing unit 4), and a cleaning unit (cleaning member 6) as a process unit acting on the drum is integrated. Illustrated. However, the process cartridge is not limited to this, and may be a process cartridge integrally including any one of a charging unit, a developing unit, and a cleaning unit in addition to the photosensitive drum.

  In the above-described embodiment, the printer is exemplified as the image forming apparatus having the transfer unit detachably. However, the present invention is not limited to this, and other image forming apparatuses such as a copying machine and a facsimile machine, Alternatively, the image forming apparatus may be another image forming apparatus that combines these functions. Also, an image forming apparatus that uses a transfer unit including an intermediate transfer belt, sequentially transfers toner images of respective colors on the belt, and transfers the toner images carried on the belt to a recording medium in a batch. However, it is not limited to this. An image forming apparatus that uses a transfer unit including a recording medium conveyance belt as an endless belt and sequentially superimposes and transfers toner images of respective colors onto a recording medium carried on the belt. The same effect can be obtained by applying the present invention to a transfer unit used in these image forming apparatuses.

A ... First posture B ... Second posture 1 ... Photoconductor drum 5 ... Intermediate transfer belt 7 ... Process cartridge 10 ... Drive roller 10a, 10b ... Drive roller shaft 10c, 10d ... Drive roller bearing 11 ... Tension roller 11a, 11b ... tension roller shaft 12 ... primary transfer roller 23 ... transfer belt cleaning device 25 ... transfer belt unit 31 ... cleaning blade 33 ... secondary transfer opposing rollers 36a and 36b ... positioning bosses 37a and 37b ... guided portion 38 ... opening and closing member 39 ... installation parts 40, 41 ... installation guide 40a ... inlet part 40b ... first guide part 40d ... second guide part 40e ... bent part 40f ... third guide part 42 ... positioning part 43 ... lock lever 43a ... rotation center 43b ... Apex 44 ... Lock lever spring 45 ... Opening 100 ... Image formation Location 101 ... intermediate transfer unit

Claims (9)

A first unit comprising an endless belt stretched by a plurality of stretch members, and a second unit comprising a cleaning member that contacts the endless belt of the first unit and cleans the toner on the endless belt And a transfer unit that is detachable from the image forming apparatus,
The second unit is swingable with respect to the first unit around the rotation axis of one of the plurality of stretching members provided in the first unit, and the image forming apparatus The transfer unit is capable of changing a posture with respect to the first unit by contacting a guide member included in the transfer unit.   The transfer unit according to claim 1, wherein the transfer unit is inserted into the image forming apparatus first from the second unit.   The second unit is centered on a rotation axis of a stretching member disposed on the innermost side when viewed from an insertion port provided in the image forming apparatus, among the plurality of stretching members provided in the first unit. The transfer unit according to claim 1, wherein the transfer unit is swingable with respect to the first unit.   The transfer unit according to claim 3, wherein the tension member disposed on the innermost side is a tension roller for applying tension to the endless belt.   5. The transfer unit according to claim 1, wherein the second unit includes a positioning boss for positioning the second unit with respect to the image forming apparatus.   6. The transfer unit according to claim 5, wherein the positioning boss is guided by a guide member included in the image forming apparatus, whereby a posture of the second unit with respect to the first unit is changed.   7. The endless belt included in the first unit is an intermediate transfer belt that carries and conveys a toner image formed on an image carrier. 7. Transcription unit.   The transfer unit according to any one of claims 1 to 6, wherein the endless belt of the first unit is a recording medium conveyance belt that carries and conveys a recording medium.   9. The image forming apparatus according to claim 1, wherein the transfer unit is a transfer unit according to claim 1.

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