Image forming apparatus

Abstract

To provide an image forming apparatus including a process unit that enables secure replacement of a developing device.SOLUTION: A process unit 25 includes a pair of side plates 61L and 61R which face each other in a left-and-right direction crossing a pull-out direction; a plurality of developing devices 35Y, 35M, 35C, and 35B which are detachably supported between the pair of side plates 61L and 61R; lock members 71 that are provided corresponding to each of the plurality of developing devices 35Y, 35M, 35C, and 35B, and movable along the left-and-right direction between a lock position in which the corresponding developing devices 35 are locked to the side plate 61R and an unlock position separating from the side plate 61R; and a biasing member that biases the lock members 71 to the lock position. An apparatus main body 3 comprises a guide portion 135 that protrudes to a direction separating from the developing device 35 in the left-and-right direction and guides one of the lock members 71 from the lock position to the unlock position with pull-out operation of the process unit 25.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a process unit that can be pulled out from a main body of the apparatus.

Background Art

[0002] As described in Patent Document 1, a tandem color image forming apparatus includes a process unit that can be pulled out from a main body of the apparatus. The process unit includes four developing devices that are arranged in parallel along a pulling-out direction and housed in a frame. The developing devices are fixed to side plates of the frame by fixing mechanisms.

[0003] The fixing mechanism includes, for example, a lock member that is supported by the frame so as to be movable in a front-rear direction. When the developing device is housed in the frame from above, the lock member is pushed downward by the developing device and retracts, and then the lock member advances and engages with the developing device.

[0004]

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When such an image forming apparatus pulls out the process unit from the main body of the apparatus, the center of gravity moves to the side of the pulled-out process unit, resulting in an unstable state. Further, when replacing the developing device, after pulling out the process unit from the main body of the apparatus, the developing device is removed, and then a new developing device is mounted. At that time, since the developing device is pushed downward to retract the lock member, a downward force is applied to the process unit. Then, the state of the image forming apparatus becomes even more unstable.

[0007] Therefore, in view of the above circumstances, an object of the present invention is to provide an image forming apparatus including a process unit in which a developing device can be stably replaced.

Means for Solving the Problems

[0008] In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus including a process unit that can be pulled out from a device main body along a predetermined pulling-out direction, wherein the process unit includes a pair of side plates facing each other in a left-right direction intersecting the pulling-out direction, a plurality of developing devices arranged in parallel along the pulling-out direction and detachably supported between the pair of side plates, a fixing position provided corresponding to each of the plurality of developing devices for fixing the corresponding developing device to the side plate, a lock member movable in the left-right direction between the fixing position and a release position spaced apart from the side plate, and a biasing member for biasing the lock member to the fixing position, the device main body is provided so as to protrude in a direction away from the developing device in the left-right direction, and includes a guide portion for guiding one of the lock members from the fixing position to the release position as the process unit is pulled out, and as one of the lock members is guided by the guide portion and moves between the fixing position and the release position as the process unit is pulled out, the developing device corresponding to the lock member is fixed to or released from the side plate.

[0009] In the present invention, when the process unit is pulled out from the device main body, one of the lock members is guided by the guide portion and moves from the fixing position to the release position, the fixing of the developing device engaged with the lock member to the side plate is released, and after the developing device corresponding to the lock member is accommodated between the pair of side plates in a state where one of the lock members has moved to the release position, the process unit is moved along the pulling-out direction until the lock member is separated from the guide portion, so that the lock member is biased by the biasing member and moves from the release position to the fixing position, and the developing device is fixed to the side plate, which may also be a feature.

[0010] In the present invention, the lock member includes a cap and an engaging portion provided integrally with the cap and engageable with the developing device. The apparatus main body includes a groove for guiding the lock member along the pulling-out direction. The guide portion is disposed above and below the groove and includes upper and lower guide pieces protruding from the groove in a direction away from the developing device in the left-right direction. When one of the lock members reaches the guide portion when the process unit is pulled out from the apparatus main body, the cap is guided by the upper and lower guide pieces and moves in a direction away from the developing device, so that the engaging portion is separated from the developing device.

[0011] In the present invention, the pulling-out direction is the front-rear direction. The engaging portion has a pair of inclined side surfaces that taper in the left-right direction when viewed from the up-down direction. The process unit further includes a through hole through which the engaging portion passes and a release lever supported so as to be movable in the pulling-out direction. By moving the release lever, the inclined side surface of the engaging portion is pushed by the edge of the opening, and the lock member moves from the fixed position toward the release position against the biasing force of the biasing member, so that the engaging portion is separated from the developing device.

Advantages of the Invention

[0012] According to the present invention, as the lock member moves in the left-right direction intersecting the pulling-out direction along with the pulling-out operation of the process unit, the developing device can be fixed to and released from the side plate. That is, when mounting or removing the developing device from the frame, it is not necessary to apply a load along the up-down direction to the process unit. Therefore, even in an image forming apparatus in which the center of gravity moves and becomes unstable when the process unit is pulled out, the developing device can be stably mounted on or removed from the frame.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11A

Figure 11B

Figure 12A

Figure 12B

Mode for Carrying Out the Invention

[0014] Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0015] Referring to FIG. 1, the overall configuration of the image forming apparatus 1 will be described. FIG. 1 is a side view schematically showing the internal configuration of the image forming apparatus 1. Up, Lo, Fr, Rr, L, and R shown in each figure indicate the upper side, lower side, front side, rear side, left side, and right side of the image forming apparatus 1, respectively.

[0016] Inside the apparatus main body 3 of the image forming apparatus 1, a paper feeding unit 5, an electrophotographic image forming unit 7, a fixing device 9, and a discharging device 11 are accommodated. On the top plate of the apparatus main body 3, a discharge port 13 and a discharge tray 15 arranged in front of the discharge port 13 are provided. Further, inside the apparatus main body 3, a main conveyance path 17 for sheets and a reversing path 19 are provided.

[0017] The paper feeding unit 5 is arranged at the lower part inside the apparatus main body 3 and includes a paper feeding cassette 21 for accommodating sheets and a paper feeding device 23 for feeding sheets from the paper feeding cassette 21.

[0018] The image forming unit 7 is arranged above the paper feeding unit 5 and includes a process unit 25, an intermediate transfer device 27, and an exposure device 29.

[0019] The process unit 25 includes a frame 31, four photosensitive drum units 33Y, 33M, 33C, and 33B (collectively referred to as the photosensitive drum unit 33) corresponding to four-color (yellow, magenta, cyan, black) toner supported by the frame 31, and developing devices 35Y, 35M, 35C, and 35B (collectively referred to as the developing device 35).

[0020] The four photosensitive drum units 33Y, 33M, 33C, and 33B are arranged side by side in the front-rear direction. The photosensitive drum unit 33 includes a photosensitive drum 41 on which an electrostatic latent image is formed, a charger 43 for charging the photosensitive drum 41, and a cleaning roller 45 for removing the toner remaining on the photosensitive drum 41. The photosensitive drum 41 is rotatable about the rotation axis in the counterclockwise direction in FIG. 1. The charger 43 and the cleaning roller 45 are arranged around the photosensitive drum 41 along the rotation direction of the photosensitive drum 41.

[0021] The four developing devices 35Y, 35M, 35C, and 35B are arranged side by side in the front-rear direction behind the corresponding four photosensitive drum units 33Y, 33M, 33C, and 33B. The developing device 35 develops, for example, the electrostatic latent image formed on the photosensitive drum 41 with toner by a one-component development method.

[0022] During maintenance or component replacement, the process unit 25 can be pulled out from the apparatus main body 3 along the front-rear direction through an opening (not shown) formed in the front side plate of the apparatus main body 3. The process unit 25 will be described later.

[0023] The intermediate transfer device 27 is disposed below the process unit 25, and includes an endless intermediate transfer belt 51, four primary transfer rollers 53 corresponding to the four photoreceptor drum units 33Y, 33M, 33C, and 33B, and a secondary transfer roller 55. The intermediate transfer belt 51 is wound around a driving roller, a driven roller, and a tension roller that are arranged apart in the front-rear direction, and runs in the clockwise direction in FIG. 1. The upper running track of the intermediate transfer belt 51 is slightly inclined downward from the rear to the front (for example, the inclination angle is 3 degrees with respect to the horizontal plane). By configuring in this way, the length of the image forming apparatus 1 in the front-rear direction can be shortened. The process unit 25 can be pulled out from the apparatus main body 3 along the pulling-out direction X along this inclined direction.

[0024] The four primary transfer rollers 53 are arranged side by side in the front-rear direction in the hollow portion of the intermediate transfer belt 51. The four primary transfer rollers 53 face the photoreceptor drums 41 of the four photoreceptor drum units 33 of the process unit 25 with the intermediate transfer belt 51 interposed therebetween, and form a primary transfer nip between the intermediate transfer belt 51 and the photoreceptor drum 41. The secondary transfer roller 55 faces the driving roller with the intermediate transfer belt 51 interposed therebetween. A secondary transfer nip is formed between the intermediate transfer belt 51 and the secondary transfer roller 55.

[0025] The exposure device 29 is disposed above the process unit 25 and exposes the photoreceptor drum 41 based on image data. Specifically, the exposure device 29 is disposed above the process unit 25 behind the foremost photoreceptor drum unit 33B and the developing device 35B. And there is a space open above the foremost photoreceptor drum unit 33B and the developing device 35B.

[0026] The fixing device 9 is disposed above the secondary transfer nip. The fixing device 9 has a pressure roller and a heating roller, and forms a fixing nip between the two rollers. The discharging device 11 is disposed above the fixing device 9 and inside the discharge port 13.

[0027] The main conveyance path 17 is formed from the paper feeding device 23 of the paper feeding unit 5, passing through the secondary transfer nip and the fixing nip, and leading to the discharging device 11. The reversing path 19 branches off from the main conveyance path 17 on the downstream side of the fixing device 9 in the sheet conveyance direction, and merges into the main conveyance path 17 on the upstream side of the secondary transfer nip.

[0028] Next, the image forming operation will be briefly described. In the image forming unit 7, the photosensitive drums 41 of the respective photosensitive drum units 33 of the process unit 25 are charged by the charger 43. Thereafter, the photosensitive drum 41 is exposed by the exposure device 29 to form an electrostatic latent image based on the image data. The electrostatic latent image is developed into a toner image by the developer carried on the developing roller of the developing device 35. The toner image is transferred from the photosensitive drum 41 to the intermediate transfer belt 51 at the primary transfer nip. Thereby, a full-color toner image is formed on the intermediate transfer belt 51.

[0029] On the other hand, in the paper feeding unit 5, a sheet is conveyed from the paper feeding cassette 21 to the main conveyance path 17 by the paper feeding device 23. The sheet is conveyed to the secondary transfer nip, and at the secondary transfer nip, the toner image formed on the intermediate transfer belt 51 is transferred to one surface of the sheet. The sheet is conveyed along the main conveyance path 17 to the fixing device 9, and at the fixing nip, the toner image is fixed to the sheet. The sheet is further conveyed to the discharging device 11 and discharged to the discharge tray 15 through the discharge port 13 by the discharging device 11.

[0030] In the case of double-sided printing, the sheet with the toner image fixed on one surface is conveyed from the main conveyance path 17 to the reversing path 19, and at the secondary transfer nip, the toner image is transferred to the other surface of the sheet. Thereafter, after the toner image is fixed to the other surface of the sheet by the fixing device 9, it is conveyed to the discharging device 11 and discharged to the discharge tray 15 through the discharge port 13 by the discharging device 11.

[0031] Next, the process unit 25 will be further described with reference to FIG. 2. FIG. 2 is a perspective view showing the process unit 25. As described above, the process unit 25 includes a frame 31, and four photoreceptor drum units 33Y, 33M, 33C, 33B and developing devices 35Y, 35M, 35C, 35B supported by the frame. The photoreceptor drum unit 33 is not shown in FIG. 2.

[0032] First, the frame 31 will be described. The frame 31 includes left and right side plates 61L, 61R facing each other in the left - right direction intersecting the pulling - out direction X (see FIG. 1) of the process unit 25, and a front cover 63 disposed between the front edges of the left and right side plates 61L, 61R. The left and right lower corners of the front cover 63 are rotatably supported by the left and right side plates 61L, 61R. Thus, the front cover 63 can be rotated forward from an upright posture (see FIG. 2) standing upright between the front edges of the left and right side plates 61L, 61R.

[0033] A positioning portion (not shown) for placing and positioning the left end portion of the developing device 35 is provided on the left side plate 61L. A lock mechanism 65 (not shown in FIG. 2, see FIG. 3 etc.) for removably fixing the right end portion of the developing device 35 is provided on the right side plate 61R. An engagement opening 35a (not shown in FIG. 2, see FIG. 5 etc.) opening to the right is formed at the right end portion of the developing device 35. The lock mechanism 65 fixes the right end portion of the developing device 35 to the right side plate 61R by engaging with this engagement opening 35a. By fixing the right end portion of the developing device 35 to the right side plate 61R in this way, the developing device 35 is fixed to the frame 31.

[0034] Next, the lock mechanism 65 will be described with reference to FIG. 3. FIG. 3 is a perspective view showing the lock mechanism 65. The lock mechanism 65 includes four lock members 71 provided for each developing device 35 and movably supported in the left - right direction (a direction intersecting the pulling - out direction X) on the right side plate 61R, and a release lever 73 movably supported along the front - rear direction on the inner surface of the right side plate 61R.

[0035] First, the right side plate 61R will be described with reference to FIGS. 3 and 4. FIG. 4 is a cross-sectional perspective view showing the opening 81 and the cylindrical portion 83 of the right side plate 61R. Four square-shaped openings 81 corresponding to the four developing devices 35Y, 35M, 35C, and 35B are formed in the right side plate 61R.

[0036] As shown in FIG. 4, a cylindrical portion 83 is formed along the periphery of the opening 81 on the outer surface of the right side plate 61R. The cylindrical portion 83 has a through-hole 85 extending along the left-right direction. The through-hole 85 has a lower-stage portion 85a, a middle-stage portion 85b, and an upper-stage portion 85c in this order from the side of the opening 81. The lower-stage portion 85a has a square cross-sectional shape same as that of the opening 81. The middle-stage portion 85b has a vertically long substantially rectangular (rounded rectangle) cross-sectional shape. The length in the major axis direction of the cross-section of the middle-stage portion 85b is shorter than the length of one side of the cross-section of the lower-stage portion 85a. The upper-stage portion 85c has a horizontally long substantially rectangular (rounded rectangle) cross-sectional shape intersecting the middle-stage portion 85b at a right angle.

[0037] Also, as shown in FIG. 3, front and rear guide protrusions 87 are formed on the inner surface of the right side plate 61R at the same height position above the four openings 81.

[0038] Next, the lock member 71 will be described with reference to FIG. 5. FIG. 5 is a cross-sectional view showing the lock member 71. The lock member 71 includes a lock lever 91 that can be engaged with the engagement opening 35a of the developing device 35, a cap 93 provided integrally with the lock lever 91, and a coil spring 95 externally fitted to the lock lever 91.

[0039] First, the lock lever 91 will be described with reference to FIG. 6A. FIG. 6A is a perspective view showing the lock lever 91. The lock lever 91 has a columnar shaft 101, an engagement portion 103 provided at one end of the shaft 101 and capable of engaging with the engagement opening 35a, and a fixing portion 105 provided at the other end of the shaft 101 and fixedly and movably integrated with the cap 93.

[0040] The engaging portion 103 has a frustum of a pyramid shape, with a rectangular top surface 103a, a square bottom surface 103b that is parallel to the top surface 103a and has a larger area than the top surface 103a, a pair of parallel trapezoidal side surfaces 103c, and a pair of inclined side surfaces 103d that are inclined from the bottom surface 103b toward the top surface 103a. One end of the shaft 101 is fixed to the center of the bottom surface 103b.

[0041] The fixing portion 105 has a substantially rectangular parallelepiped shape, with a substantially rectangular (rounded rectangle) parallel top surface 105a and bottom surface 105b, a pair of arc-shaped side surfaces 105c, and a pair of parallel rectangular side surfaces 105d. The length along the major axis direction of the cross-section of the fixing portion 105 is longer than the diameter of the shaft 101, and the length along the minor axis direction is equal to the diameter of the shaft 101. The other end of the shaft 101 is fixed to the center of the bottom surface 105b. Also, in the circumferential direction of the shaft 101, the pair of trapezoidal side surfaces 103c of the engaging portion 103 and the pair of arc-shaped side surfaces 105c of the fixing portion 105 are arranged in the same direction, and the pair of inclined side surfaces 103d of the engaging portion 103 and the pair of rectangular side surfaces 105d of the fixing portion 105 are arranged in the same direction.

[0042] Also, the lengths in the major axis direction and minor axis direction of the cross-section of the fixing portion 105 are equivalent to the lengths in the major axis direction and minor axis direction of the cross-sections of the middle portion 85b and upper portion 85c of the through-hole 85 of the cylindrical portion 83 of the right side plate 61R.

[0043] Next, the cap 93 will be described with reference to FIGS. 6B and 6C. FIG. 6B is a cross-sectional view showing the cap 93, and FIG. 6C is a front view showing the cap 93. The cap 93 has a disk portion 111 and a cylindrical portion 113 provided on one end face of the disk portion 111. A through-hole 115 extending in the axial direction is formed at the center of the disk portion 111. The cross-sectional shape of the through-hole 115 is the same as the cross-sectional shape of the fixing portion 105 of the lock lever 91. Further, a recess 117 that intersects the through-hole 115 at a right angle when viewed axially is formed on the outer surface of the disk portion 111. The depth of the recess 117 is approximately the same as the height (thickness) of the fixing portion 105. Also, two gentle convex portions 119 (not shown in FIGS. 6B and 6C, see FIG. 8) are formed diagonally on the inner surface of the disk portion 111. The two convex portions 119 are arranged along the major axis direction of the recess 117.

[0044] The cylindrical portion 113 is formed coaxially with the through-hole 115 between the through-hole 115 and the two convex portions 119.

[0045] Next, the process of assembling the lock member 71 to the right side plate 61R will be described with reference to FIG. 7. FIG. 7 is a perspective view showing the lock member 71 and the right side plate 61R. First, as shown in FIG. 7(a), the lock lever 91 is held in a posture where the fixing portion 105 is horizontally long (the major axis direction is along the front-rear direction), and a coil spring 95 is externally fitted to the shaft 101 from the side of the fixing portion 105. Then, the fixing portion 105 is inserted into the opening 81 of the right side plate 61R from the inside.

[0046] As shown in FIG. 7(b), the tip of the lock lever 91 (the fixed part 105 and the tip of the shaft 101) protrudes from the cylindrical part 83 through the through hole 85 of the cylindrical part 83 from the opening 81. The coil spring 95 is disposed between the bottom surface 103b of the engaging part 103 of the lock lever 91 and the periphery of the through hole 85 of the cylindrical part 83 of the right side plate 61R. Then, the lock lever 91 is rotated 90 degrees. As a result, the fixed part 105 of the lock lever 91 assumes a vertically long posture (a posture in which the long axis direction is along the vertical direction). As a result, the lock lever 91 is prevented from coming out of the cylindrical part 83. Further, the engaging part 103 assumes a tapered posture in which the inclined side surfaces 103d (see FIG. 6A) are arranged in the front-rear direction and face the inside of the right side plate 61R when viewed from above.

[0047] Thereafter, the cap 93 is placed over the tip of the lock lever 91 protruding from the cylindrical part 83 of the right side plate 61R. That is, the cap 93 is maintained in a vertically long posture (a posture in which the long axis direction is along the vertical direction) with respect to the through hole 115, and the fixed part 105 of the lock lever 91 is inserted into this through hole 115.

[0048] Then, as shown in FIG. 7(c), the cylindrical part 113 of the cap 93 is placed over the cylindrical part 83 of the right side plate 61R. Further, the lock lever 91 is pushed into the opening 81 of the right side plate 61R against the biasing force of the coil spring 95. When the lock lever 91 is pushed in until the engaging part 103 is inserted from the opening 81 of the right side plate 61R into the lower stage part 85a (see FIG. 4) of the cylindrical part 83, the fixed part 105 protrudes outward from the cap 93. Thereafter, the cap 93 is rotated 90 degrees. As a result, as shown in FIG. 7(d), both the concave part 117 of the disk part 111 of the cap 93 and the orientation of the fixed part 105 of the lock lever 91 become vertically long (the long axis direction is along the vertical direction).

[0049] After the force pressing the lock lever 91 is released, as shown in FIG. 7(e), the lock lever 91 is biased by a coil spring 95 toward the inside of the right side plate 61R with respect to the cylindrical portion 83 of the right side plate 61R, and the engaging portion 103 of the lock lever 91 protrudes inward beyond the right side plate 61R. Further, the fixing portion 105 of the lock lever 91 is fitted into the recess 117 of the disc portion 111 of the cap 93. Thereby, the assembly of the lock member 71 to the right side plate 61R is completed.

[0050] Next, the release lever 73 will be described with reference to FIG. 3. The release lever 73 is a plate-like member that is long in the front-rear direction, and four rectangular through-holes 121 corresponding to the four openings 81 of the right side plate 61R are formed therein. Further, front and rear guide openings 123 are formed above the four through-holes 121. The guide openings 123 are oblong in shape and long in the front-rear direction.

[0051] The release lever 73 is supported movably along the front-rear direction on the inner surface of the right side plate 61R. Specifically, the front and rear guide openings 123 of the release lever 73 are inserted into the front and rear guide projections 87 of the right side plate 61R. Further, the front end of the release lever 73 is connected to the front cover 63 (see FIG. 2) of the frame 31. When the front cover 63 is closed, the four through-holes 121 are aligned in the left-right direction with the four openings 81 of the right side plate 61R. On the other hand, when the front cover 63 is opened, the release lever 73 is guided by the guide projections 87 and moves forward, and the four through-holes 121 are spaced forward from the four openings 81 of the right side plate 61R.

[0052] Next, with reference to FIG. 2, the structure for supporting the process unit 25 on the apparatus main body 3 will be described. As described above, the process unit 25 can be pulled forward through an opening formed in the front surface of the apparatus main body 3. On the inner surfaces of the right and left side plates (not shown) of the apparatus main body 3, left and right guide rails 131 (only the right guide rail 131 is shown in FIG. 3) for supporting the process unit 25 so as to be movable in the front-rear direction are provided. In the left guide rail (not shown), a groove that engages with a guide portion (not shown) provided on the left side plate 61L of the process unit 25 is formed along the front-rear direction.

[0053] As shown in FIG. 2, in the right guide rail 131, grooves 133 that engage with four lock members 71 of the process unit 25 are formed along the front-rear direction. The width (height) of the groove 133 is equal to the outer diameter of the cylindrical portion 113 of the cap 93 of the lock member 71, and the cylindrical portion 113 of the cap 93 is engaged with the groove 133. The groove 133 opens at the front edge of the guide rail 131. On the outer surface of the guide rail 131, a guide portion 135 is provided at the front end of the groove 133.

[0054] The guide portion 135 will be described with reference to FIG. 2 and also FIG. 8. FIG. 8 is a view of the guide portion 135 as seen from above. The guide portion 135 includes upper and lower guide pieces 137 provided above and below the groove 133. As shown in FIG. 8, the upper and lower guide pieces 137 are substantially trapezoidal when viewed from the up-down direction, and have a top portion 137a, a rear inclined portion 137b that inclines rearward from the rear end of the top portion 137a, and a front inclined portion 137c that inclines forward from the front end of the top portion 137a. A shallow recess 139 is formed at the center of the top portion 137a. The upper and lower guide pieces 137 are formed, for example, by punching out a part of the guide rail 131 and processing it.

[0055] In a state where the process unit 25 is housed in the apparatus main body 3, as shown in FIG. 2, the four lock members 71 (the cylindrical portions 113 of the caps 93) are engaged with the groove 133 behind the guide portion 135.

[0056] In the process unit 25 having the above configuration, the operations of removing the developing device 35 from the frame 31 and attaching the developing device 35 to the frame 31 will be described with reference to FIGS. 2, 5, 8, etc., FIGS. 9 and 10. FIG. 9 is a perspective view showing the process unit 25 pulled out from the apparatus main body 3, and FIG. 10 is a cross-sectional view showing the lock member 71 separated from the developing device 35.

[0057] In the process unit 25, as shown in FIG. 2, the four developing devices 35 are each fixed to the right side plate 61R via the lock member 71. Specifically, as shown in FIG. 5, the lock lever 91 of the lock member 71 is biased by a coil spring 95, and the engaging portion 103 protrudes inward (the side closer to the developing device 35) from the right side plate 61R, passes through the through hole 121 of the release lever 73, and is inserted into the engaging opening 35a of the developing device 35. Thereby, the developing device 35 is fixed to the right side plate 61R. The position where the engaging portion 103 protrudes inward from the right side plate 61R is set as the fixed position of the lock lever 91.

[0058] At the time of maintenance or component replacement, the process unit 25 is pulled forward along the left and right guide rails 131 through the opening in the front of the apparatus main body 3. At this time, the cylindrical portions 113 of the caps 93 of the four lock members 71 of the process unit 25 move forward in the grooves 133 of the guide rails 131.

[0059] Eventually, as shown in FIG. 9, the cylindrical portion 113 of the cap 93 of the foremost locking member 71 corresponding to the foremost developing device 35B reaches the guide portion 135 of the groove 133. Then, the disk portion 111 of the cap 93 of the locking member 71 rides on the rearwardly inclined portions 137b (see FIG. 8) of the upper and lower guide pieces 137 of the guide portion 135. Thereafter, when the process unit 25 is further pulled forward, as shown in FIGS. 8 and 10, the disk portion 111 of the cap 93 of the locking member 71 rides from the rearwardly inclined portions 137b to the top portions 137a of the upper and lower guide pieces 137. As a result, the cap 93 moves outward (the side away from the developing device 35). Then, as shown in FIG. 10, the lock lever 91 fixed integrally with the cap 93 moves outward, the engaging portion 103 is separated from the engaging opening 35a of the developing device 35, and is accommodated in the lower stage portion 85a of the through hole 85 of the cylindrical portion 83 through the through hole 121 of the release lever 73 and the opening 81 of the right side plate 61R.

[0060] Thereafter, by lifting the foremost developing device 35B corresponding to the foremost locking member 71, the developing device 35 can be removed from the frame 31. The position where the engaging portion 103 of the lock lever 91 is accommodated in the through hole 85 of the cylindrical portion 83 of the right side plate 61R is defined as the release position. Since the exposure device 29 is not disposed above the guide portion 135 and a predetermined space is open, after lifting the developing device 35 into this space, it is pulled forward through the opening of the front side plate of the apparatus main body 3.

[0061] Also, as shown in FIG. 8, since the two convex portions 119 provided on the disk portion 111 of the cap 93 enter the concave portions 139 formed on the top portions 137a of the upper and lower guide pieces 137, the movement of the process unit 25 when removing the developing device 35 is restricted.

[0062] When removing the developing device 35 other than the foremost developing device 35B, the process unit 25 may be pulled out until the locking member 71 corresponding to the relevant developing device 35 reaches the guide portion 135.

[0063] On the other hand, when attaching the removed developing device 35 to the frame 31, the process unit 25 is pulled out from the apparatus main body 3 until the lock member 71 corresponding to the relevant developing device 35 reaches the guide portion 135. As a result, as described above, the lock member 71 is guided by the guide portion 135 and moves to the release position (see FIG. 10). Then, the developing device 35 is accommodated in the frame 31 from above.

[0064] Then, the process unit 25 is pushed backward until the lock member 71 separates from the guide portion 135. Then, the lock member 71 separates from the guide portion 135, and the lock lever 91 of the lock member 71 is biased by the coil spring 95, causing the lock member 71 to move to the fixed position. Thus, the coil spring 95 is an example of a biasing member that biases the lock member 71 to the fixed position in the present invention. As a result, the engaging portion 103 of the lock lever 91 is inserted into the engaging opening 35a of the developing device 35 (see FIG. 5). Thereby, the developing device 35 is fixed to the frame 31.

[0065] As described above, according to the present invention, the lock member 71 moves in the left - right direction (a direction intersecting the pulling - out direction X) along with the pulling - out operation of the process unit 25, so that the developing device 35 can be fixed to and released from the side plate 61. That is, when attaching or detaching the developing device 35 from the frame 31, it is not necessary to apply a load along the vertical direction to the process unit 25. Therefore, even in an image forming apparatus in which the center of gravity moves and becomes unstable when the process unit 25 is pulled out, the developing device 35 can be stably attached to or detached from the frame 31.

[0066] Furthermore, in the operation of pulling out the process unit 25, since the lock member 71 automatically moves between the fixed position and the release position, it is not necessary to perform a special operation when fixing or releasing the developing device 35.

[0067] Next, the operation of removing all four developing devices 35 from the frame 31 will be described with reference to FIGS. 11A to 12B. FIGS. 11A and 11B show the release lever 73 and the lock member 71 with the front cover 63 closed, and FIGS. 12A and 12B show the release lever 73 and the lock member 71 with the front cover 63 open. FIGS. 11B and 12B are views of the lock member 71 seen from above.

[0068] When removing all four developing devices 35 from the frame 31, first, the process unit 25 is pulled out from the apparatus main body 3. At this time, it is not necessary to position any of the lock members 71 in the guide portion 135, and the process unit 25 is pulled out to a position where the rearmost developing device 35Y can be removed.

[0069] In this state, as shown in FIG. 11A, the front cover 63 is closed. Also, as shown in FIG. 11B, the lock member 71 has moved to the fixed position. That is, the engaging portion 103 of the lock lever 91 of the lock member 71 protrudes inward from the through hole 121 of the release lever 73 and is inserted into the engaging opening 35a of the developing device 35Y (see also FIG. 11A). As shown in FIG. 11B, the engaging portion 103 has a tapered shape inward when viewed from above, that is, the inclined side surfaces 103d are arranged in the front-rear direction.

[0070] Thereafter, as shown in FIG. 12A, the front cover 63 is opened (rotated forward). Then, the release lever 73 connected to the front cover 63 is guided by the guide projection 87 of the right side plate 61R and moves forward. As a result, the rear edge of the through hole 121 of the release lever 73 hits the inclined side surface 103d of the engaging portion 103 of the lock lever 91 protruding from the through hole 121. Thereby, the engaging portion 103 is pushed outward, and the lock lever 91 starts to move rightward against the biasing force of the coil spring 95.

[0071] Furthermore, when the release lever 73 moves forward, eventually, as shown in FIG. 12B, the top surface 103a of the engaging portion 103 of the lock lever 91 is pushed in by the outer surface of the release lever 73. In this way, the locking member 71 moves in the direction from the fixed position toward the release position, and the engaging portion 103 separates from the engaging openings 35a of all the developing devices 35. Thereafter, by lifting the developing device 35, all the developing devices 35 can be removed from the frame 31.

[0072] In this way, by simply opening the front cover 63, the fixing of all the developing devices 35 to the frame 31 can be released.

[0073] Although the present invention has been described with respect to specific embodiments, the present invention is not limited to the above embodiments. Those skilled in the art can modify the above embodiments without departing from the scope and gist of the present invention.

Explanation of Reference Numerals

[0074] 1 Image forming apparatus 3 Apparatus main body 25 Process unit 35 Developing device 61L, 61R Side plates 71 Locking member 73 Release lever 93 Cap 95 Coil spring (biasing member) 103 Engaging portion 133 Groove 135 Guide portion 137 Upper and lower guide pieces

Claims

1. An image forming apparatus including a process unit that can be pulled out from a device body along a predetermined pulling direction, wherein the process unit includes a pair of side plates facing each other in a left-right direction intersecting the pulling direction, a plurality of developing devices arranged in parallel along the pulling direction and detachably supported between the pair of side plates, locking members provided corresponding to each of the plurality of developing devices, the locking members being movable along the left-right direction between a fixed position for fixing the corresponding developing device to the side plate and a release position spaced apart from the side plate, a biasing member for biasing the locking member to the fixed position, and the device body includes a guide portion provided so as to project in a direction away from the developing device in the left-right direction, and guiding one of the locking members from the fixed position to the release position as the process unit is pulled out, An image forming apparatus, characterized in that as one of the locking members is guided by the guide portion and moves between the fixed position and the release position as the process unit is pulled out, the developing device corresponding to the locking member is fixed to or released from the side plate.

2. When the process unit is pulled out from the device body, one of the locking members is guided by the guide portion and moves from the fixed position to the release position, and the fixing of the developing device engaged by the locking member to the side plate is released. After the developing device corresponding to the locking member is accommodated between the pair of side plates with the locking member in the moved release position, the process unit is moved along the pulling direction until the locking member is separated from the guide portion, so that the locking member is biased by the biasing member and moves from the release position to the fixed position, and the developing device is fixed to the side plate. The image forming apparatus according to claim 1, characterized in that

3. The locking member includes a cap, and an engaging portion provided integrally with the cap and engageable with the developing device, the device body includes a groove for guiding the locking member along the pulling direction, the guide portion includes upper and lower guide pieces disposed above and below the groove and projecting from the groove in a direction away from the developing device in the left-right direction, When one of the lock members reaches the guide portion when the process unit is pulled out from the apparatus main body, the cap is guided by the upper and lower guide pieces and moves in a direction away from the developing device, so that the engaging portion is separated from the developing device. The image forming apparatus according to claim 2, characterized in that.

4. The pulling-out direction is the front-rear direction, The engaging portion has a pair of inclined side surfaces that are tapered in the left-right direction when viewed from the up-down direction, The process unit further includes a release lever that has a through hole through which the engaging portion passes and is supported so as to be movable in the pulling-out direction, By moving the release lever, the inclined side surface of the engaging portion is pushed by the edge of the through hole, and the lock member moves from the fixed position toward the release position against the biasing force of the biasing member, so that the engaging portion is separated from the developing device. The image forming apparatus according to claim 3, characterized in that.

Images