Image-forming apparatus provided with interlocking mechanism for inputting drive force to drive roller of belt unit

An image-forming apparatus includes a main body, a drive source, an image forming section, a coupling and an interlocking mechanism. The image forming section includes a trigger part and a belt unit including: a belt; and a drive roller and a follow roller opposing each other in a first direction perpendicular to an axial direction of the drive roller. The belt is stretched over the drive roller and the follow roller to extend in the first direction. The coupling includes a movable part movable between a transmitting position transmitting a drive force from the drive source to the drive roller and an interrupting position interrupting transmission of the drive force from the drive source to the drive roller. The interlocking mechanism is configured to interlock movement of the movable part between the transmitting position and the interrupting position with movement of the trigger part.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priorities from Japanese Patent Application Nos. 2014-199760 filed Sep. 30, 2014 and 2014-199772 filed Sep. 30, 2014. The entire contents of these priority applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an image forming apparatus provided with a belt stretched over a drive roller and a follow roller.

BACKGROUND

One image-forming apparatus known in the art includes a belt unit having a belt, and a drive roller that drives the belt; a coupling having a movable part configured to advance toward and couple with the drive roller and to uncouple and retract from the drive roller; a cover configured to open and close an opening formed in a main body; and an interlocking mechanism configured to advance and retract the movable part of the coupling in association with the opening and closing of the cover. In this image-forming apparatus, the movable part is configured to be retracted from the drive roller when the cover is opened and to be coupled with the drive roller when the cover is closed.

However, in this conventional mechanism, the movable part of the coupling is configured to move in association with the opening and closing of the cover. Since the cover is frequently opened and closed when resolving paper jams, replacing toner cartridges, and the like, the movable part is frequently uncoupled from and coupled to the drive roller, even in cases when the belt unit is not being removed or mounted. Consequently, coupling portions of the movable part and the drive roller may become worn.

Further, since the movable part of the coupling is configured to move in association with the movement of the cover, the connection provided by the coupling may become unstable when the cover is not completely closed.

SUMMARY

In view of the foregoing, it is an object of the present disclosure to provide an image-forming apparatus having a configuration that does not require a movable part to uncouple from or couple with another member, such as a drive roller, except when a belt unit is being mounted or removed.

It is another object of the present disclosure to provide an image-forming apparatus that is capable of maintaining proper operations of a belt unit by ensuring that a movable part of a coupling, which functions to transmit a drive force to a drive roller of the belt unit, advances and retracts properly relative to the drive roller.

In order to attain the above and other objects, the disclosure provides an image-forming apparatus that may include: a main body; a drive source provided in the main body and configured to generate a drive force; an image forming section configured to form an image; a coupling; and an interlocking mechanism. The image forming section includes a trigger part and a belt unit. The belt unit includes a belt, a drive roller and a follow roller. The drive roller defines an axis extending in an axial direction and is configured to rotate about the axis. The follow roller opposes the drive roller in a first direction perpendicular to the axial direction, the belt being stretched over the drive roller and the follow roller and extending in the first direction. The coupling includes a movable part configured to move between a transmitting position transmitting the drive force from the drive source to the drive roller and an interrupting position interrupting transmission of the drive force from the drive source to the drive roller. The interlocking mechanism is provided in the main body and is configured to interlock movement of the movable part between the transmitting position and the interrupting position with movement of the trigger part of the image forming section.

According to another aspect, the disclosure provides an image-forming apparatus that may include: a main body; a drive source configured to generate a drive force; a belt unit attachable to and detachable from the main body; a coupling; a moving member; and an interlocking mechanism. The belt unit includes: a belt; a drive roller defining an axis extending in an axial direction and configured to rotate about the axis; and a follow roller, opposing the drive roller in a first direction perpendicular to the axial direction, the belt being stretched over the drive roller and the follow roller and extending in the first direction. The coupling includes a movable part configured to move between a transmitting position transmitting the drive force from the drive source to the drive roller and an interrupting position interrupting transmission of the drive force from the drive source to the drive roller. The moving member is configured to move between a first position and a second position in accordance with attachment and detachment of the belt unit relative to the main body, the moving member moving from the first position to the second position upon attachment of the belt unit to the main body, the moving member moving from the second position to the first position upon detachment of the belt unit from the main body. The interlocking mechanism is configured to interlock the movement of the movable part with the movement of the moving member, the interlocking mechanism being configured to move the movable part to the transmitting position in conjunction with movement of the moving member from the first position to the second position, the interlocking mechanism being configured to move the movable part to the interrupting position in conjunction with movement of the moving member from the second position to the first position.

According to still another aspect, the disclosure provides an image-forming apparatus that may include: a main body; a drive source configured to generate a drive force; a belt unit; a coupling; a plurality of photosensitive drums; a moving member; and an interlocking mechanism. The belt unit includes: a belt; a drive roller defining an axis extending in an axial direction and configured to rotate about the axis; and a follow roller opposing the drive roller in a first direction perpendicular to the axial direction, the belt being stretched over the drive roller and the follow roller and extending in the first direction. The coupling includes a movable part configured to move between a transmitting position transmitting the drive force from the drive source to the drive roller and an interrupting position interrupting transmission of the drive force from the drive source to the drive roller. The plurality of photosensitive drums is juxtaposed in the first direction. The moving member is configured to support the plurality of photosensitive drums and is configured to move between a first position and a second position relative to the main body in a second direction crossing the first direction but different from the axial direction, the moving member at the first position allowing the photosensitive drums supported by the moving member to be in contact with the belt of the belt unit, the moving member at the second position allowing the photosensitive drums supported by the moving member to be separated from the belt of the belt unit. The interlocking mechanism is configured to interlock the movement of the movable part with the movement of the moving member, the interlocking mechanism being configured to move the movable part to the transmitting position in conjunction with movement of the moving member from the first position to the second position, the interlocking mechanism being configured to move the movable part to the interrupting position in conjunction with movement of the moving member from the second position to the first position.

DETAILED DESCRIPTION

1. First Embodiment

A color printer1according to a first embodiment will be described while referring toFIGS. 1 through 8.

Directions in the following description will be based on a perspective of a user using the color printer1. Specifically, the right side ofFIG. 1will be called the “front,” the left side will be called the “rear,” the near side will be called the “left,” and the far side will be called the “right.” Further, the “top” and “bottom” ofFIG. 1will be the vertical direction of the color printer1.

As shown inFIG. 1, the color printer1as an example of an image-forming apparatus includes a main body10. Within the main body10, primarily provided are a sheet-feeding section2for supplying sheets P of paper to be printed, an image-forming section3for forming images on the sheets P supplied by the sheet-feeding section2, and a sheet-discharging section4for discharging sheets P from the main body10after the image-forming section3has formed images thereon.

The sheet-feeding section2is provided in a bottom portion of the main body10. The sheet-feeding section2primarily includes a sheet tray21configured to accommodate the sheets P of paper, and a sheet-feeding mechanism22for supplying the sheets P from the sheet tray21to the image-forming section3. The sheet-feeding mechanism22is configured to separate the sheets P in the sheet tray21and supply the sheets P one at a time to the image-forming section3.

The image-forming section3primarily includes an exposure unit30, an image-forming unit40, a belt unit50, a belt cleaner60, and a fixing unit70.

The exposure unit30is provided in an upper portion of the main body10. Although not shown in the drawings, the exposure unit30includes a laser light-emitting unit, a polygon mirror, lenses, reflecting mirrors, and the like.

The image-forming unit40is arranged between the sheet-feeding section2and the exposure unit30. The image-forming unit40primarily includes four process units4, and a holder42for retaining the four process units41that are juxtaposed in a front-rear direction. The holder42can be moved between a mounted position inside the main body10(shown inFIG. 1) and a removed position withdrawn from the main body10.

The process units41are attachable to and detachable from the holder42. Each process unit41includes a photosensitive drum43(as an example of a photosensitive member), a charger44, and a developing roller46, as well as a supply roller, a thickness-regulating blade, and a toner-accommodating portion for which reference numerals have been omitted.

The belt unit50is provided between the sheet-feeding section2and the image-forming unit40. The belt unit50can be mounted in and removed from the main body10. The belt unit50primarily includes a drive roller51, a follow roller52, an endless conveying belt53(as an example of a belt) stretched over the drive roller51and follow roller52, and four transfer rollers54.

The direction in which the conveying belt53is stretched taut by the drive roller51and follow roller52is the front-rear direction and is an example of a first direction. However, the first direction may be specified through a different expression. For example, the first direction may be specified as a direction in which the photosensitive drums43that contact the conveying belt53are juxtaposed.

The conveying belt53has a top surface53A, and a bottom surface53B. The top surface53A extends in the front-rear direction and contacts each of the photosensitive drums43. The bottom surface53B also extends in the front-rear direction and contacts a cleaning roller61of the belt cleaner60described next. Further, a drive force generated by a drive source M, such as a motor, is configured to be transmitted to the drive roller51. When the drive roller51is driven to rotate by this drive force, the conveying belt53circulates counterclockwise inFIG. 1.

The belt cleaner60is disposed below the belt unit50. The belt cleaner60includes the cleaning roller61, and a collection box62. The cleaning roller61contacts the bottom surface53B of the conveying belt53. Toner collected from the conveying belt53is configured to be collected in the collection box62. A backup roller56is disposed inside the loop formed by the conveying belt53such that the conveying belt53(bottom surface53B) is nipped between the backup roller56and the cleaning roller61.

The fixing unit70is disposed rearward of the image-forming unit40and the belt unit50. The fixing unit70includes a heating roller71, and a pressure roller72disposed to oppose the heating roller71and in pressure contact with the heating roller71.

In an image-forming operation of the image-forming section3, the charger44applies a uniform charge to a surface of the corresponding photosensitive drum43, after which the exposure unit30irradiates laser beams (indicated by chain lines inFIG. 1) in a high-speed scan to expose the surfaces of the respective photosensitive drums43and form electrostatic latent images thereon. The supply rollers of the process units41supply toner from the corresponding toner-accommodating portions to the corresponding developing rollers46, and the toner on the surfaces of the developing rollers46is maintained at a uniform thickness by the corresponding thickness-regulating blades.

The toner carried on the surfaces of the developing rollers46is then supplied to the electrostatic latent images formed on the corresponding photosensitive drums43to produce toner images on the photosensitive drums43. Thereafter, a sheet P supplied onto the conveying belt53is conveyed between the photosensitive drums43and conveying belt53(transfer rollers54), whereby the toner images formed on the respective photosensitive drums43are sequentially transferred to and superposed on the sheet P. After the toner images have been transferred onto the sheet P, the sheet P is conveyed between the heating roller71and pressure roller72of the fixing unit70to thermally fix the transferred toner image to the sheet P.

The sheet-discharging section4includes a curved discharge path81and a plurality of conveying rollers82for conveying the sheets P. The discharge path81extends upward from the exit point of the fixing unit70and subsequently curves frontward. After the toner image is thermally fixed to the sheet P in the fixing unit70, the conveying rollers82convey the sheet P along the discharge path81and discharge the sheet P onto a discharge tray12provided on a top surface of the main body10.

A front cover11is provided on a front end portion of the main body10and serves as a front wall that can be opened and closed. When the front cover11is opened, a user can pull the holder42out from the main body10to the removed position in order to remove the process units41from the holder42. By removing the holder42at the removed position from the main body10, the user can remove the belt unit50from the main body10.

Next, a detailed structure near the belt unit50will be described.

As shown inFIG. 2, the belt unit50includes a frame55that rotatably supports the drive roller51and the follow roller52.

The drive roller51includes a shaft51S extending in the left-right direction (seeFIGS. 3A and 4). The shaft51S defines an axis extending in an axial direction parallel to the left-right direction. The drive roller51can rotate about this axis extending in the axial direction upon receipt of the drive force from the drive source M.

The frame55has a left wall part55A, a right wall part55B and a front wall part55C. The left wall part55A and right wall part55B are respectively disposed outward (on the left and right sides) of both rollers51and52in a left-right direction. The front wall part55C bridges front ends of the both side wall parts55A and55B. Grip parts C1are provided on an upper portion of the front wall part55C and protrude forward therefrom. The user can grip the grip parts C1when mounting and removing the belt unit50relative to the main body10.

The right wall part55B includes: a body part B1that is elongated in the front-rear direction; and a bearing part B2, an engaging part B3, and a supported part B4that protrude rightward from a right surface of the body part B1. Similarly, the left wall part55A includes: a body part A1that is elongated in the front-rear direction; a bearing part A2that protrudes rightward from a right surface of the body part A1; and an engaging part A3and a supported part A4that protrude leftward from a left surface of the body part A1.

The bearing parts A2and B2are cylindrical-shaped portions provided on rear ends of the respective side wall parts55A and55B. The bearing parts A2and B2rotatably support respective end portions of the shaft51S of the drive roller51(seeFIG. 4). The shaft51S of the drive roller51has a left end on which a belt-side coupling51A is provided. A body-side coupling130is provided on the main body10as an example of a movable part. The body-side coupling130can couple to and uncouple from the belt-side coupling51A. Together, the body-side coupling130and the belt-side coupling51A constitute a coupling CP that functions as a switch for transmitting and interrupting the drive force from the drive source M to the drive roller51. Four recessed parts51B are formed in the belt-side coupling51A at regular intervals in a circumferential direction thereof for receiving a pair of protruding parts133B described later (seeFIGS. 3A and 4).

The body-side coupling130is configured to advance toward and retract from the belt-side coupling51A in the left-right direction, i.e., the axial direction of the drive roller51. The body-side coupling130can move between an interrupting position (shown inFIGS. 2 and 4) for interrupting the transmission of the drive force from the drive source M to the drive roller51, and a transmitting position (shown inFIG. 5) for transmitting the drive force from the drive source M to the drive roller51. In other words, in the interrupting position, the body-side coupling130is uncoupled from the belt-side coupling51A and retracted leftward in the axial direction of the drive roller51. In the transmitting position, the body-side coupling130is coupled with the belt-side coupling51A.

As shown inFIGS. 4 and 5, a body-side drive gear140is rotatably provided on the main body10. The body-side drive gear140supports the body-side coupling130so that the body-side coupling130can move in the axial direction of the drive roller51. The body-side drive gear140includes a gear part141for receiving the drive force from the drive source M, and a protruding part142that protrudes from a center portion of the gear part141toward the body-side coupling130.

The body-side coupling130includes a cylindrical part131, a flange132, and a joint133provided on a right end of the cylindrical part131. The cylindrical part131receives the protruding part142of the body-side drive gear140inserted therein so that the cylindrical part131can move relative to the protruding part142in the axial direction but can engage the protruding part142in a rotating direction of the cylindrical part131. On the right end of the cylindrical part131, a groove131A is formed to be recessed leftward. The groove131A extends in a radial direction of the cylindrical part131.

The flange132protrudes radially outward from an outer peripheral surface of the cylindrical part131and has an annular shape. As shown inFIG. 6A, a compression coil spring150is disposed between the flange132and the body-side drive gear140. The compression coil spring150is an example of a biasing member and functions to apply a biasing force to the body-side coupling130toward the belt-side coupling51A.

The joint133functions to transmit the drive force from the body-side drive gear140to the drive roller51via the body-side coupling130, even when the axis of the cylindrical part131constituting the body-side coupling130is offset from the axis of the drive roller51. The joint133includes a disc-shaped base part133A, the pair of protruding parts133B that protrudes rightward from the base part133A, and an engaging part133C that engages in the groove131A formed in the right end of the cylindrical part131. The engaging part133C engaging in the groove131A can move in a first radial direction (specifically, in a radial direction of the cylindrical part131).

The protruding parts133B are disposed on a right surface of the base part133A to be spaced apart from each other in a second radial direction orthogonal to the first radial direction. When inserted into two of the four recessed parts51B formed in the belt-side coupling51A that are arranged in a radial direction of the belt-side coupling51A, the protruding parts133B are capable of moving in the second radial direction while engaging with the recessed parts51B in the rotating direction. With this arrangement, the joint133can transmit the drive force from the body-side drive gear140to the belt-side coupling51A while the belt-side coupling51A and cylindrical part131are engaged with each other in the rotating direction, even when the axis of the belt-side coupling51A is radially offset from the axis of the body-side drive gear140. Specifically, the cylindrical part131and joint133move relative to each other in the first radial direction, and the recessed parts51B and joint133move relative to each other in the second radial direction, enabling the drive force to be transmitted even when the axes of the body-side drive gear140and belt-side coupling51A are radially offset from each other.

As shown inFIGS. 3A and 3B, the bearing parts A2and B2are supported by a pair of restricting parts14provided on the main body10. The restricting parts14function to restrict displacement of the drive roller51through the bearing parts A2and B2in the vertical direction (as an example of a second direction).

Each restricting part14includes a rear part14A extending vertically, an upper part14B extending forward from a top edge of the rear part14A, and a lower part14C extending forward from a bottom edge of the rear part14A. That is, each restricting part14is open at a front side thereof in the front-rear direction. The lower part14C extends farther forward than the upper part14B.

The upper parts14B and corresponding lower parts14C define vertical gaps therebetween that are slightly larger than the outer diameter of the bearing parts A2and B2such that the outer peripheral surfaces of the bearing parts A2and B2can be fitted into these gaps. With this configuration, the upper parts14B can restrict upward movement of the respective bearing parts A2and B2, while the lower parts14C can restrict downward movement of the same.

The rear parts14A function to restrict movement (displacement) of the drive roller51in the front-rear direction, and specifically to restrict rearward movement of the drive roller51. The rear parts14A are disposed rearward of and adjacent to the corresponding bearing parts A2and B2of the belt unit50when the belt unit50is mounted in the main body10. However, the rear parts14A may be disposed at a position spaced away from the bearing parts A2and B2of the belt unit50when the belt unit50is mounted in the main body10, provided that the rear parts14A are positioned near the bearing parts A2and B2.

The body-side coupling130described above is disposed on the axis of the drive roller51whose rearward movement is restricted by the rear parts14A.

The restricting parts14have a cross-sectional shape that appears like an angular “U” that has been rotated sideways. Since the bearing parts A2and B2can be fitted into and supported by the corresponding restricting parts14, the belt unit50is allowed to pivot about the axis of the drive roller51during attachment and detachment of the belt unit50relative to the main body10.

The engaging parts A3and B3are configured to engage with corresponding pressing members110provided in the main body10, as shown inFIG. 3A. The pressing members110are arranged to interpose the belt unit50therebetween in the axial direction when the belt unit50is attached to the main body10. The left and right pressing members110are an example of a moving member and examples of a first moving part and a second moving part). The engaging parts A3and B3are example of a trigger part. The engaging parts A3and B3are tapered such that their bottom ends grow gradually narrower toward the bottom. The engaging parts A3and B3are disposed at a position forward of the drive roller51by a first distance L1and rearward of the grip parts C1by a second distance L2larger than the first distance L1. More specifically, the first distance L1is the distance from the axis of the drive roller51(i.e., from the fulcrum point about which the belt unit50is caused to pivot during attachment thereof to the main body10) to the point at which the engaging parts A3and B3act on the pressing members110. The second distance L2is the distance from this point of action to the rearmost side of the grip parts C1.

The pressing members110constitute part of pressing mechanisms100and function to press the corresponding engaging parts A3and B3forward toward position fixing parts15provided in the main body10. The pressing members110can pivot between an initial position shown inFIG. 6B(as an example of a first position) and a pressing position shown inFIGS. 3A and 7B(as an example of a second position). The pressing mechanisms100and position fixing parts15are provided one each on the left and right sides of the belt unit50. That is, the pressing mechanisms100are arranged to interpose the belt unit50therebetween in the axial direction when the belt unit50is attached to the main body10. Likewise, the position fixing parts15are arranged to interpose the belt unit50therebetween in the axial direction when the belt unit50is attached to the main body10. The left and right position fixing parts15are examples of a positioning part, a first positioning part and a second positioning part.

Each pressing member110includes a pivot shaft part111, a first arm part112, a guide part113and a second arm part114. The pivot shaft part111is supported by the main body10to allow the pressing member110to pivotally move about the pivot shaft part111. The first arm part112extends upward from the pivot shaft part111and configured to hold the corresponding engaging part A3or B3against the corresponding position fixing part15. The guide part113protrudes rearward from a top end portion of the first arm part112. The second arm part114extends forward from the pivot shaft part111. The top end portion of the first arm part112has a front end portion that has a tapered shape that grows gradually narrower toward the respective engaging part A3or B3.

When the belt unit50is removed from the main body10, top surfaces of the guide parts113are angled relative to the horizontal plane, as shown inFIG. 6B. Specifically, the top surfaces of the guide parts113are sloped relative to paths defined by the corresponding engaging parts A3and B3while the belt unit50makes pivotal movement during mounting of the belt unit50on the main body10. In this way, the guide parts113guide the corresponding engaging parts A3and B3while the belt unit50is being mounted until the engaging parts A3and B3become interposed between the corresponding first arm parts112and position fixing parts15.

In addition to the pressing member110, each pressing mechanism100includes a tension coil spring120as an example of an urging member, a first urging part and a second urging part. The tension coil spring120has one end that is engaged with a distal end of the second arm part114constituting the corresponding pressing member110, while the other end of the tension coil spring120is engaged with a spring engaging part16provided in the main body10. With this arrangement, the tension coil springs120can urge the corresponding pressing members110normally toward their initial position (shown inFIG. 6B) from the pressing position (shown inFIGS. 3 and 7B). Being urged by the tension coil springs120, the pressing members110press the corresponding engaging parts A3and B3forward against the corresponding position fixing parts15, thereby fixing the front-rear position of the belt unit50. When the engaging parts A3and B3are removed from between the corresponding pressing members110and position fixing parts15, the pressing members110are brought into contact with the position fixing parts15, thereby being restricted from pivoting farther clockwise. The pressing members110are thus maintained in their initial position.

The supported parts A4and B4are supported from below by a pair of left and right support parts17disposed in the main body10. The supported parts A4and B4are positioned between the respective engaging parts A3and B3and the grip parts C1in the front-rear direction, and specifically are positioned closer to the grip parts C1. Each of the side wall parts55A and55B of the frame55is provided, on respective front ends thereof, with a bearing52A that rotatably supports the follow roller52, a guide hole52B that supports the bearing52A such that the bearing52A can move in the front-rear direction, and a compression coil spring52C that urges the bearing52A forward. With this configuration, the follow roller52is urged in a direction away from the drive roller51(i.e., frontward), applying suitable tension to the conveying belt53.

As shown inFIGS. 4 and 5, an interlocking mechanism200is provided on the left side of the belt unit50for interlocking the left pressing member110with the body-side coupling130. The interlocking mechanism200includes a first link210coupled to the left pressing member110, a second link220coupled to the first link210, and a third link230coupled to the second link220. The third link230also has a cam235for pressing the body-side coupling130leftward.

As shown inFIGS. 6A through 7B, the first link210is an elongated member extending in the front-rear direction. The first link210has a front end that is pivotably coupled to the top end portion of the first arm part112constituting the pressing member110. The first link210is also supported by a guide (not shown) provided in the main body10so as to be capable of moving in the front-rear direction. With this configuration, the left pressing member110is configured to press the first link210rearward so that the first link210can move rearward when the pressing member110pivots from the initial position to the pressing position, and the left pressing member110pulls the first link210forward when pivoting from the pressing position to the initial position. A first coupling shaft211is provided on a rear end portion of the first link210for coupling with the second link220.

The second link220is an elongated member that extends vertically when the pressing member110is in its initial position. The second link220has a bottom end portion formed with a first elongate hole221for engaging with the first coupling shaft211. The second link220has a top end portion in which a second elongate hole222is formed for engaging with a second coupling shaft234provided on the third link230described later. The second link220is also formed with a support hole223between the first elongate hole221and second elongate hole222, for enabling the second link220to be pivotably supported on a support shaft (not shown) provided in the main body10.

With this configuration, the first link210is configured to press the bottom end portion of the second link220rearward when the first link210moves rearward so that the second link220can pivot clockwise as shown inFIG. 7B. Conversely, the first link210is configured to pull the bottom end portion of the second link220forward when moving in the forward direction so that the second link220can pivot counterclockwise as shown inFIG. 6B.

The third link230is an elongated member that extends in the front-rear direction. The third link230is supported by a guide (not shown) provided in the main body10so as to be capable of moving in the front-rear direction. The third link230has a first segment231elongated in the front-rear direction, a second segment232extending leftward from a rear edge of the first segment231, and a third segment233extending rearward from a left edge of the second segment232.

The first segment231has a front end portion on which the second coupling shaft234is provided for engaging in the second elongate hole222of the second link220. With this configuration, the second link220can pull the third link230forward when pivoting clockwise as shown inFIG. 7Band push the third link230rearward when pivoting counterclockwise as shown inFIG. 6B.

The cam235is provided on a front end portion of the third segment233and protrudes leftward therefrom. The cam235has a rear surface serving as a cam surface235A that slopes relative to the left-right direction. More specifically, the cam surface235A slopes leftward toward the front side for pushing the flange132of the body-side coupling130leftward when the cam235moves rearward in order to move the body-side coupling130into the interrupting position. The cam235has a left surface serving as a retaining surface235B configured to retain the body-side coupling130in the interrupting position by supporting the flange132of the body-side coupling130.

Next, operations of the interlocking mechanism200will be described.

When attaching the belt unit50to the main body10, the user grips the grip parts C1and inserts the belt unit50into the main body10, as shown inFIG. 8. The user lowers the rear end of the belt unit50to a prescribed position in the main body10until the bearing parts A2and B2are resting on the lower parts14C of the corresponding restricting parts14. Next, the user pushes the rear end of the belt unit50rearward while sliding the bearing parts A2and B2over the lower parts14C, inserting the bearing parts A2and B2between the corresponding upper parts14B and lower parts14C. Once the bearing parts A2and B2contact the rear parts14A, the rear parts14A restrict the bearing parts A2and B2from moving further rearward.

Subsequently, the user pivotally moves the front end of the belt unit50downward about the axis of the drive roller51. At this time, the engaging parts A3and B3contact the corresponding guide parts113of the pressing members110. By pushing the grip parts C1further downward, the engaging parts A3and B3press the guide parts113of the pressing members110rearward against the urging force of the tension coil springs120. Consequently, the pressing members110pivot from the initial position shown inFIG. 8toward the pressing position shown inFIGS. 7Aand B until the engaging parts A3and B3are inserted between the corresponding pressing members110and position fixing parts15. At this time, the engaging parts A3and B3are pressed against the position fixing parts15, thereby fixing the front-rear position of the belt unit50. Note, by setting the second distance L2between the grip parts C1and the engaging parts A3and B3greater than the first distance L1from the drive roller51to the engaging parts A3and B3, a lever effect can be utilized so that the user need only apply a small amount of force to the grip parts C1in order to push the engaging parts A3and B3between the corresponding pressing members110and position fixing parts15.

Further, when the left pressing member110pivots from the initial position to the pressing position, the first link210moves rearward, causing the second link220to pivot clockwise inFIG. 8and the third link230to move forward. Consequently, the retaining surface235B of the cam235slides off the flange132of the body-side coupling130, and the biasing force of the compression coil spring150moves the body-side coupling130from the interrupting position to the transmitting position, at which time the body-side coupling130is coupled to the belt-side coupling51A.

At about the same time that the engaging parts A3and B3enter between the corresponding pressing members110and position fixing parts15, the supported parts A4and B4come to a rest on the corresponding support parts17, as illustrated inFIG. 3. Therefore, both front and rear ends of the belt unit50are supported from below by the lower parts14C of the restricting parts14and the support parts17.

When removing the belt unit50from the main body10, first the user grips the grip parts C1and lifts the front end of the belt unit50upward so that the belt unit50pivots about the axis of the drive roller51. At this time, the engaging parts A3and B3are extracted from between the pressing members110and position fixing parts15, and the urging force of the tension coil springs120causes the pressing members110to pivot clockwise inFIG. 6Bfrom the pressing position to the initial position.

At this time, the first link210moves forward, causing the second link220to pivot counterclockwise inFIG. 6Band moving the third link230rearward. Consequently, the cam surface235A of the cam235pushes the flange132of the body-side coupling130leftward. The body-side coupling130therefore moves from its transmitting position to its interrupting position against the biasing force of the compression coil spring150and, hence, is retracted from the belt-side coupling51A. Subsequently, the user pulls the bearing parts A2and B2out of the corresponding restricting parts14to complete removal of the belt unit50from the main body10.

The color printer1according to the first embodiment described above can obtain the following operational and technical advantages.

The body-side coupling130is configured to move in order to couple with or uncouple from the belt-side coupling51A only when the belt unit50is mounted in and removed from the main body10. Accordingly, unlike a conventional configuration in which an input-side coupling is advanced and retracted in association with opening and closing of a front cover, the body-side coupling130is prevented from coupling with and uncoupling from the belt-side coupling51A, except when the belt unit50is mounted and removed relative to the main body10.

By providing the tension coil springs120for urging the pressing members110from their pressing position toward their initial position, the tension coil springs120can effectively return the pressing members110to their initial positions.

Since the tension coil springs120used for operating the interlocking mechanism200are also used for positioning the belt unit50, this arrangement reduces the number of required parts.

The belt unit50can be effectively positioned by providing the position fixing parts15, pressing members110, and tension coil springs120on both left and right sides of the belt unit50. By interlocking only one of the pressing members110with the interlocking mechanism200, the structure of the first embodiment is simpler than a structure that interlocks both pressing members with interlocking mechanisms, for example.

By providing the body-side coupling130, which is a movable part of the coupling CP, in the main body10, the structure of the belt unit50in the present embodiment can be made simpler than a structure that provides the movable part on the belt unit, for example, thereby facilitating the attaching and detaching operations for the belt unit50. Further, when the belt unit50is designed as a replaceable part, the cost of replaceable parts can be reduced.

The restricting parts14provided for restricting the vertical displacement of the drive roller51can restrain fluctuations in the vertical position of the drive roller51when the color printer1incurs external disturbances, such as vibrations or impacts. Accordingly, the color printer1according to the first embodiment can ensure more stable behavior of the conveying belt53, suppressing irregularities in printed positions of images.

When pivoting the belt unit50about the axis of the drive roller51, the bearing parts A2and B2that may have a tendency to move rearward are restrained from moving rearward by the restricting parts14, thereby suppressing changes in the front-rear position of the drive roller51when the belt unit50is pivoted. Further, the body-side coupling130is provided along the axis of the drive roller51whose movement in the vertical and rearward directions is restrained by contact between the restricting parts14and the bearing parts A2and B2. Since the body-side coupling130is advanced toward and retracted from the drive roller51whose position changes very little, the body-side coupling130can be effectively coupled with and uncoupled from the drive roller51.

Since the second distance L2from the grip parts C1to the engaging parts A3and B3is greater than the first distance L1from the drive roller51to the engaging parts A3and B3, the pressing members110can be more effectively operated than a structure whose distance from the drive roller to the engaging parts is greater than the distance from the engaging parts to the grip parts. This is because the engaging parts A3and B3at the point of action can apply a sufficiently large force to the pressing members110, even when very little force is applied to the grip parts C1at the point of effort

2. Variations to the First Embodiment

While the pressing members110that fix the position of the belt unit50serve as an example of the moving member in the first embodiment described above, the present disclosure is not limited to this configuration. Any member that engages and moves with the belt unit50when the belt unit50is mounted in and removed from the main body10may serve as the moving member. Further, the moving members do not need to be members that move through an engagement with the belt unit50, but may be members that are moved due to a user's operation or the like when the user mounts or removes the belt unit50.

For example,FIGS. 9 and 10show a locking member300according to a variation of the first embodiment as another example of the moving member. The locking member300of this variation is configured to lock the position of a belt unit350mounted in the main body10. The locking member300of this variation also serves as the trigger part. InFIGS. 9 and 10, like parts and components are designated with the same reference numerals as the first embodiment.

Specifically, in this variation, the locking member300is configured to pivot between a restricting position (the position inFIG. 10) in which the locking member300is engaged with the belt unit350attached to the main body10and restricts movement (displacement) of the belt unit350, and a release position (the position inFIG. 9) in which the locking member300does not restrict movement of the belt unit350to allow detachment of the belt unit350from the main body10.

More specifically, the locking member300is provided leftward of the belt unit350and is positioned closer to the front side of the belt unit350than the rear side. The locking member300includes a pivot shaft part310supported in the main body10, a first extension part320that extends forward from the pivot shaft part310when the locking member300is in the restricting position, and a second extension part330that extends downward from the pivot shaft part310when the locking member300is in the restricting position. The locking member300is configured to pivotally move about the pivot shaft part310.

The first extension part320is provided with an operating part321, and a pair of engaging protrusions322. The operating part321is provided on a front end of the first extension part320and is operated by the user. The engaging protrusions322are formed rearward and downward of the operating part321. The engaging protrusions322are capable of engaging with a pin357(an example of an engaged part) provided on the belt unit350. An elongate hole331is formed in a bottom end of the second extension part330. The elongate hole331engages with a coupling shaft212provided on a front end portion of a first link210A of an interlocking mechanism200A. In this variation, the first link210A extends further forward than the first link210of the first embodiment.

By coupling the locking member300to the first link210A in this way, the body-side coupling130can move in association with the locking member300via the interlocking mechanism200A. Specifically, when the locking member300is moved from the release position to the restricting position, the cam235moves off the body-side coupling130, allowing the body-side coupling130to move from its interrupting position to its transmitting position through the biasing force of the compression coil spring150. When the locking member300moves from the restricting position to the release position, the cam235(retaining surface235B) presses the body-side coupling130leftward against the biasing force of the compression coil spring150, moving the body-side coupling130from the transmitting position to the interrupting position.

Here, a holding part (not shown) may also be provided for holding the locking member300in either the release position or the restricting position. For example, a shallow recessed part may be formed in one of the locking member300and main body10, while a protruding part that protrudes slightly and is capable of engaging in the recessed part may be provided on a remaining one of the locking member300and main body10. The locking member300may be held in either the release position or the restricting position through the engagement of the protruding part and recessed part, and the engagement between the protruding part and recessed part may be broken when the user applies force to the locking member300.

With the construction of the variation described above, the belt unit350can be mounted in and removed from the main body10when the locking member300is in the release position, but cannot be mounted or removed when the locking member300is in the restricting position because movement of the belt unit350is restricted by the engagement of the engaging protrusions322and the pin357. Normally, the user operates the locking member300only when mounting and removing the belt unit350. Since the body-side coupling130in this construction is coupled with or uncoupled from the belt-side coupling51A when the locking member300is operated through a normal user operation and only when the user is mounting or removing the belt unit350, the body-side coupling130is prevented from coupling with or uncoupling from the belt-side coupling51A except when mounting or removing the belt unit350, unlike the conventional structure in which the movable part of the coupling is advanced or retracted in association with the movement of the front cover.

Incidentally, the moving member may be configured to move linearly, for example, and does not need to pivot like the pressing members110of the first embodiment and the locking member300of the variation described above.

3. Second Embodiment

Next, a color printer1A according to a second embodiment will be described with reference toFIGS. 11 through 15B, wherein like parts and components are designated with the same reference numerals as the first embodiment in order to avoid duplicating explanation. The color printer1A of the second embodiment has a similar structure as that of the color printer1of the first embodiment, but is provided with an interlocking mechanism400, instead of the interlocking mechanism200.

The interlocking mechanism200of the first embodiment is configured to associate the movement of the body-side coupling130with attachment and detachment of the belt unit50relative to the main body10. On the other hand, the interlocking mechanism400of the second embodiment is configured to associate the movement of the body-side coupling130with attachment and detachment of the holder42relative to the main body10.

In the second embodiment, when accommodated in the main body10, the holder42is configured to move vertically between a first position (the state shown inFIG. 1) in which the photosensitive drums43are in contact with the conveying belt53, and a second position (the state shown inFIG. 11) in which the photosensitive drums43are separated from the conveying belt53. Here, the vertical direction (upward and downward direction) is an example of a second direction. Further, as in the first embodiment, the holder42can move in the front-rear direction between the second position and a fifth position shown inFIG. 12. This fifth position corresponds to the removed position in the first embodiment. In the fifth position, nearly an entire top portion of the holder42(the portion corresponding to the process units41) is exposed outside the main body10.

The holder42can be removed from the main body10after being placed at the fifth position.

Here, movement of the holder42from the first position to the fifth position is facilitated by guides (not shown) provided in left and right frames constituting the main body10. Note that while the holder42moves vertically between the first and second positions in the second embodiment, the holder42may be configured to move in a direction slightly sloped relative to the vertical direction, i.e., in a direction that includes both a vertical component and a front-rear component.

The holder42includes a pair of (left and right) side walls42A. An engaging protrusion42B is provided on the left side wall42A, i.e., the side wall42A on the body-side coupling130side, as illustrated inFIG. 13A. The engaging protrusion42B protrudes leftward from an outer surface of the left side wall42A for engaging with the interlocking mechanism400. The engaging protrusion42B serves as the trigger part in the second embodiment. The interlocking mechanism400is provided on the left side (one side in the left-right direction) of the belt unit50for interlocking the holder42(engaging protrusion42B) with the body-side coupling130.

Specifically, referring toFIG. 13B, the engaging protrusion42B has a bottom portion serving as a first engaging part42C that engages with the interlocking mechanism400when the holder42moves from the second position to the first position. The engaging protrusion42B has a top portion serving as a second engaging part42D that engages with the interlocking mechanism400when the holder42moves from the first position to the second position. That is, the first engaging part42C and second engaging part42D constituting the engaging protrusion42B also serve as the trigger part. Further, the left and right side walls42A of the holder42have bottom surfaces42E. Two protruding parts42F are formed on the bottom surfaces42E of both side walls42A at both front and rear ends thereof, for a total of four protruding parts42F. The protruding parts42F protrude downward from the bottom surfaces42E. Each protruding part42F has a bottom surface serving as a contact surface42G configured to contact a mounting surface (not shown) formed in the color printer401for placing the holder42thereon mounted in the main body10(also seeFIG. 11).

The contact surfaces42G are arranged below the photosensitive drums43, i.e., on the belt unit50side of the photosensitive drums43. That is, the contact surfaces42G are arranged closer to the belt unit50than the photosensitive drums43are to the belt unit50. The engaging protrusion42B is arranged above the contact surfaces42G, i.e., on the photosensitive drum43side of the contact surfaces42G. That is, the engaging protrusions42B are arranged closer to the photosensitive drums43than the contact surfaces42G are to the photosensitive drums43.

As shown inFIG. 13A, the interlocking mechanism400is provided on the left side of the belt unit50for engaging with the engaging protrusion42B of the holder42. The interlocking mechanism400includes a first link410to be coupled to the engaging protrusion42B, a second link420coupled to the first link410, and a third link430coupled to the second link420. The third link430is provided with a cam435for pressing the body-side coupling130leftward.

More specifically, as shown inFIGS. 14A and 15A, the first link410is an elongated member extending in the vertical direction and is supported on the main body10so as to be capable of moving vertically. More specifically, the main body10includes a pair of guide parts13(an example of a holding part) configured to interpose the first link410therebetween in the front-rear direction to hold the first link410. The first link410has a front-rear width slightly larger than a distance between the pair of guide parts13in the front-rear direction. Hence, when an external force is not being applied to the first link410, the first link410is maintained at its vertical position by friction with the pair of guide parts13. When an external force is applied to the first link410, the first link410is moved vertically while being supported by the guide parts13.

The first link410has an upper end portion in which a slit411is formed to extend in the front-rear direction. The slit411is open on its front end, allowing the engaging protrusion42B to be inserted thereinto. When the holder42is lowered from the second position (seeFIG. 15A) to the first position (seeFIG. 14A), the first engaging part42C of the engaging protrusion42B presses against a bottom surface of the slit411so that the first link410is lowered together with the holder42to its third position corresponding to the first position of the holder42(shown inFIGS. 14A and 14B). Thus, when the holder42is supported in its first position by the main body10, the first link410is held in its third position by the guide parts13.

Similarly, when the holder42is raised from the first position to the second position, the second engaging part42D of the engaging protrusion42B presses against a top surface of the slit411so that the first link410rises together with the holder42, moving to its fourth position corresponding to the second position of the holder42, as shown inFIGS. 15A and 15B. When the holder42is subsequently moved from the second position to the fifth position and the engaging protrusion42B is extracted from the slit411, the guide parts13maintain the first link410in the fourth position.

The first link410also includes a first coupling shaft412positioned below the slit411for coupling with the second link420. A pair of guide surfaces413is formed on front edges of the slit411that define the opening of the slit411. The guide surfaces413slope respectively upward and rearward toward the front side for expanding the opening of the slit411vertically and function to guide insertion of the engaging protrusion42B into the slit411.

The second link420is an L-shaped member configured of a pivot shaft part421, a first extension part422and a second extension part423. The pivot shaft part421is provided at a corner portion of the “L” shape of the second link420. The pivot shaft part421is supported by the main body10to permit the second link420to pivot about the pivot shaft part421. The first extension part422extends diagonally downward and forward from the pivot shaft part421when the holder42is in the first position (seeFIG. 14A). The second extension part423extends diagonally downward and rearward from the pivot shaft part421when the holder42is in the first position. The first extension part422is formed with a first elongate hole422A for engaging with the first coupling shaft412of the first link410. The second extension part423has a lower end portion in which a second elongate hole423A is formed for engaging with a second coupling shaft434provided on the third link430described later.

With this configuration, the first link410presses the first extension part422of the second link420downward when moving downward, causing the second link420to pivot clockwise as shown inFIG. 14A. When the first link410moves upward, the first link410pulls the first extension part422of the second link420upward, causing the second link420to pivot counterclockwise as shown inFIG. 15A.

The third link430is supported in the main body10so as to be capable of moving in the front-rear direction. The third link430primarily includes a first segment431elongated in the front-rear direction, and a second segment432that extends rearward from a rear end of the first segment431. The second segment432has a thicker left-right dimension than the first segment431(seeFIGS. 14B and 15B).

The second coupling shaft434is provided on the first segment431for engaging in the second elongate hole423A of the second link420. With this configuration, the second link420can push the third link430rearward when pivoting clockwise as shown inFIG. 14A, and can pull the third link430forward when pivoting counterclockwise as shown inFIG. 15A.

The cam435is provided on a rear portion of the second segment432and protrudes leftward therefrom. The cam435has a front surface serving as a cam surface435A that slopes relative to the left-right direction. More specifically, the cam surface435A slopes leftward toward the rear side for pushing the flange132of the body-side coupling130leftward when the cam435moves frontward in order to move the body-side coupling130into the interrupting position. The cam435has a left surface serving as a retaining surface435B configured to retain the body-side coupling130in the interrupting position by supporting the flange132of the body-side coupling130.

Next, operations of the interlocking mechanism400according to the second embodiment will be described.

To mount the holder42in the main body10, the user first moves the holder42from its fifth position (shown inFIG. 12) to the second position (shown inFIG. 11). Through this operation, the engaging protrusion42B of the holder42becomes inserted in the slit411formed in the first link410, as shown inFIG. 15A.

Next, the user lowers the holder42from the second position to the first position utilizing the weight of the holder42itself. At this time, the first link410moves downward together with the holder42, causing the second link420to pivot clockwise and the third link430to move rearward, as illustrated inFIG. 14A. As a result of this operation, the retaining surface435B of the cam435slides off the flange132of the body-side coupling130, as shown inFIG. 14B. Consequently, the body-side coupling130moves from the interrupting position to the transmitting position by the biasing force of the coil spring150and couples with the belt-side coupling51A.

To pull the holder42out of the main body10, the user first lifts the holder42from its first position to its second position, as shown inFIG. 15A. At this time, the first link410moves upward, causing the second link420to pivot counterclockwise and the third link430to move forward. Consequently, the cam surface435A of the cam435pushes the flange132of the body-side coupling130leftward to move the flange132onto the retaining surface435B. The body-side coupling130thus moves from its transmitting position to its interrupting position against the biasing force of the coil spring150and is retracted from the belt-side coupling51A. Next, the user pulls the holder42from its second position to its fifth position. Through this operation, the engaging protrusion42B of the holder42is extracted from the slit411formed in the first link410while the guide parts13hold the first link410at the fourth position.

The depicted structure according to the second embodiment can obtain the following operational and technical advantages.

In a conventional structure that associates movement of a coupling with movement of a front cover, the connection formed by the coupling may become unstable when the front cover has not been completely closed. However, in the color printer1A of the second embodiment, the interlocking mechanism400is provided for moving the body-side coupling130to the transmitting position, in which a drive force is transmitted to the belt-side coupling51A, in association with movement of the holder42to the first position, at which the photosensitive drums43are in contact with the conveying belt53. In this state, the conveying belt53of the belt unit50can operate properly during image formation.

Since the interlocking mechanism400is operated in conjunction with vertical movement of the holder42, the weight of the holder42can be used to effectively operate the interlocking mechanism400.

The engaging protrusion42B can move the first link410while engaged therewith when the holder42moves both upward and downward. Therefore, the interlocking mechanism400can be configured without providing a spring or the like for returning a first link to the fourth position. That is, it is possible to configure an interlocking mechanism with a spring for urging the first link toward the fourth position, whereby the first link is moved to the third position using an engaging protrusion on the holder to press down on the top surface of the first link against the urging force of the spring, and the first link returns to the fourth position by the urging force of this spring when the holder is raised; but the interlocking mechanism400according to the second embodiment does not require such a spring. Further, since the spring in this type of structure applies a constant upward force to the holder, the state of contact between the photosensitive drums and the conveying belt may degrade over time. However, since the interlocking mechanism400of the second embodiment does not employ a spring, such degraded contact between the photosensitive drums43and the conveying belt53can be avoided.

Since the engaging protrusion42B is provided on the side wall42A constituting the holder42, i.e., on the side of the body-side coupling130, the structure of the interlocking mechanism400can be made simpler than a structure that provides an engaging protrusion on the side of the holder opposite the input-side coupling, for example.

By providing the engaging protrusion42B above the contact surfaces42G of the holder42, the engaging protrusion42B does not come into contact with the mounting surfaces or the like in the color printer1A when the contact surfaces42G of the holder42are placed on the corresponding mounting surfaces. This arrangement enables the holder42to be supported in a stable state on the mounting surfaces.

When the holder42is moved from the second position to the fifth position, the guide parts13maintain the first link410at its fourth position. Hence, the body-side coupling130can effectively be held at the interrupting position while the holder42is pulled to the fifth position. Further, since the first link410is maintained at the fourth position, the engaging protrusion42B of the holder42can be reliably inserted into the slit411when the holder42is moved back from the fifth position to the second position.

By moving the holder42from the second position to the fifth position, the holder42can be exposed on the outside of the main body10, facilitating operations for replacing the process units41and the like.

Other than above, similar technical advantages as the first embodiment can also be obtained in the structure of the second embodiment.

4. Variations to the Second Embodiment

While the guide parts13are examples of the holding part in the second embodiment described above, the holding part may be configured as a spring. For example,FIG. 16Ashows a spring510as another example of the holding part. The spring510is configured to retain the first link410at the fourth position. More specifically, a pair of guide parts518is provided in the main body10for supporting the first link410so that the first link410can move vertically. Here, the guide parts518define a gap therebetween that is slightly larger than the front-rear width of the first link410. The main body10is also provided with a spring support part511that supports the spring510, and a restricting wall512that restricts the first link410from moving further upward (i.e., in the direction away from the third position) from the fourth position shown inFIG. 16A.

In this variation, the spring510can suitably maintain the first link410in the fourth position. Note that the spring110may be configured to have a weak urging force that is merely sufficient to maintain the first link410in the fourth position and need not have a larger urging force for moving the first link410from the third position to the fourth position.

As another variation to the second embodiment,FIG. 16Bshows an engaging protrusion620as another example of the holding part. The engaging protrusion620of this variation is provided in the main body10and is configured to engage with an engaged protrusion614formed on the first link410to hold the first link410in the fourth position. Both the engaged protrusion614and the engaging protrusion620are low-profile protrusions and are configured to disengage when the weight of the holder42is applied. With this configuration, the engagement between the engaged protrusion614and engaging protrusion420can properly maintain the first link410in the fourth position.

Further, the gap between the guide parts13of the second embodiment may be greater than the front-rear width of the first link410, provided that sufficient frictional force is generated between the retaining surface435B of the cam435and the flange132of the body-side coupling130. This frictional force can also maintain the first link410in the fourth position through the third link430and second link420as frictional force generated by the flange132suppresses rearward movement of the third link430. Here, the holding part of this case is the body-side coupling130that possesses the flange132.

In the second embodiment, the engaging protrusion42B is provided on the holder42and the slit411is formed in the first link410. However, the opposite configuration is also possible; namely, the slit may be formed in the holder and the engaging protrusion that enters the slit may be provided on the first link. In this case, the top surface formed in the slit serves as the first engaging part, while the bottom surface formed in the slit serves as the second engaging part.

5. Other Variations and Modifications

The cam235of the first embodiment and the cam435of the second embodiment are both configured to move in a direction orthogonal to the axial direction of the drive roller51. However, alternative configurations are conceivable. For example, the cam may have a plurality of cam surfaces arranged concentrically with the axis of the movable part. This cam may be configured to pivot about this axis such that its cam surfaces move in a circumferential direction and press against the movable part.

The conveying belt53as an example of the belt in the first and second embodiments described above is stretched over two rollers (drive roller51and follow roller52). Alternatively, the belt may be looped around a drive roller and two or more follow rollers, for example. In this case, the first direction is the direction in which the belt is stretched between the drive roller and the follow roller disposed upstream of the drive roller in the circulating direction of the belt.

In the first and second embodiments described above, the conveying belt53for conveying the sheets P of paper serves as an example of the belt. However, the belt may be a transfer belt or the like for carrying toner images and transferring the images onto paper. Further, the photosensitive member may be a member other than the photosensitive drum43, such as a belt-like photosensitive member.

In the first and second embodiments described above, the body-side coupling130is provided in the main body10as the movable part, and the belt-side coupling51A is provided on the belt unit50. However, the movable part may be provided on the belt unit while the member that the movable part couples with and uncouples from may be provided in the main body.

While both of the interlocking mechanism200of the first embodiment and the interlocking mechanism400of the second embodiment described above have three links (210-230and410-430) respectively, the number of links may be modified as desired. Further, the interlocking mechanism may be configured of members other than links, such as a pinion gear and a rack gear.

While the tension coil spring120serves as an example of the urging member, the urging member may be a compression coil spring, a leaf spring, or a torsion spring, for example. Similarly, the biasing member is not limited to the compression coil spring150but may be a tension coil spring, a leaf spring, or a torsion spring, for example.

While the disclosure is applied to a color printer in the depicted embodiments, the disclosure may also be applied to another image-forming apparatus, such as a copy machine or a multifunction device.