JP4808413B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copying machine, and a facsimile machine, for example, a printer, includes a transfer belt unit for transferring a toner image onto a sheet. The transfer belt unit includes a drive roller, an idle roller, and the drive roller. As a transfer member that is stretched between an idle roller and travels along an image forming portion of each color, and on the back side of the belt, the belt is pressed against a photosensitive drum as an image carrier of each image forming portion. A transfer roller is provided and positioned with respect to the main body of the printer. Each of the transfer rollers is positioned with respect to the transfer belt unit (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2002-60039

  However, in the conventional printer, since each transfer roller is positioned with respect to the transfer belt unit, if the transfer belt unit is distorted (distorted) with respect to the apparatus main body, the transfer roller is also distorted with respect to the apparatus main body. End up. In that case, each transfer roller is not pressed uniformly against the photosensitive drum, white spots occur in the image, and the image quality deteriorates.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that solves the problems of the conventional printer and can uniformly press a transfer member against an image carrier and can improve image quality. To do.

  For this purpose, the image forming apparatus of the present invention includes an image carrier, an apparatus main body, at least two rollers, a belt stretched between the rollers, and a frame, and is detachable from the apparatus main body. And a developer image formed on the image carrier is recorded by being loosely fitted in a hole formed in the frame in the belt unit. A transfer member for transferring to a medium, and disposed on the apparatus main body, formed by bending a plate-like member, and rotatably supporting the image carrier and the transfer member and positioning with respect to the apparatus main body One end supported by the support member, and when the belt unit is attached to the apparatus main body, the roller unit is loosely fitted with a large play in the hole formed in the frame. And a biasing member for urging the member to the image bearing member.

  According to the present invention, an image forming apparatus includes an image carrier, an apparatus main body, at least two rollers, a belt stretched between the rollers, and a frame, and is detachable from the apparatus main body. And a developer image formed on the image carrier is recorded by being loosely fitted in a hole formed in the frame in the belt unit. A transfer member for transferring to a medium, and disposed on the apparatus main body, formed by bending a plate-like member, and rotatably supporting the image carrier and the transfer member and positioning with respect to the apparatus main body And a transfer part that is supported at one end by the support member and loosely fitted in a hole formed in the frame when the belt unit is attached to the apparatus main body. The and a biasing member for urging the image bearing member.

  In this case, since the positions of the image carrier and the belt unit are determined by the support member, even if the frame is distorted, the relative position between the transfer member and the image carrier does not change. Therefore, since the transfer member can be pressed uniformly against the image carrier, white spots are not generated in the image, and the image quality can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer as an image forming apparatus will be described.

  FIG. 2 is a schematic view of the printer according to the first embodiment of the present invention.

  In the figure, P1 to P4 are black, yellow, magenta, and cyan image forming units, and each of the image forming units P1 to P4 includes a photosensitive drum unit 22 as an image carrier unit, and the photosensitive drum unit 22. And an LED head 23 as an exposure device disposed opposite to the photosensitive drum 24 as an image carrier. Reference numeral 11 denotes a transfer belt unit as a belt unit which is detachably disposed on the printer main body. The transfer belt unit 11 is connected to a drive source (not shown) and receives a first roller. A driving roller 12, an idle roller 13 as a second roller, a belt 14 stretched between the driving roller 12 and the idle roller 13 and run along the image forming portions P1 to P4 of the respective colors, On the back side of the belt 14, a transfer roller 15 as a transfer member that presses the belt 14 against each photosensitive drum 24, a frame 16, and the like are provided.

  Reference numeral 21 denotes a sheet as a recording medium. The sheet 21 is conveyed from a paper feeding unit (not shown), skew-corrected by the registration roller pair 20, and further conveyed, and each image forming unit by the belt 14. It is conveyed along P1 to P4.

  Meanwhile, in the photosensitive drum unit 22, a charging roller as a charging device, a developing roller as a developer carrying member that holds toner as a developer, a cleaning blade as a cleaning device, and the like are provided around the photosensitive drum 24. Arranged. The charging roller uniformly and uniformly charges the surface of the photosensitive drum 24, and the LED head 23 writes image data on the photosensitive drum 24 to form an electrostatic latent image. Subsequently, the developing roller attaches toner to the electrostatic latent image to form a toner image as a developer image on the photosensitive drum 24.

  Next, when the paper 21 is conveyed between the photosensitive drum 24 and each transfer roller 15 by the belt 14 and passes, the toner images of the respective colors are sequentially transferred onto the paper 21 and transferred onto the paper 21. An image is formed. Then, the sheet 21 on which the toner image is formed is further conveyed and sent to a fixing device 25 as a fixing device disposed downstream of the transfer belt unit 11, and the color toner image is formed on the sheet by the fixing device 25. 21 is fixed to form a color image.

  Next, an assembly unit of each photosensitive drum unit 22 and the transfer belt unit 11 will be described.

  FIG. 1 is a first perspective view showing an essential part of an assembly unit according to the first embodiment of the present invention, FIG. 3 is an exploded perspective view of the assembly unit according to the first embodiment of the present invention, and FIG. 5 is a first perspective view of an assembly unit according to the first embodiment of the invention, FIG. 5 is a second perspective view showing the main part of the assembly unit according to the first embodiment of the present invention, and FIG. FIG. 7 is a front view showing the main part of the assembly unit in the first embodiment, FIG. 7 is a perspective view showing the arrangement state of the spring in the first embodiment of the present invention, and FIG. 8 is the first embodiment of the present invention. FIG. 9 is a perspective view showing the mounting state of the bearing in the first embodiment of the present invention, FIG. 10 is a perspective view of the bearing in the first embodiment of the present invention, FIG. 11 shows an apparatus book according to the first embodiment of the present invention. FIG. 12 is a plan view showing the mounting state of the transfer roller in the first embodiment of the present invention, FIG. 13 is a perspective view of the transfer belt unit in the first embodiment of the present invention, and FIG. These are the 2nd perspective views of the assembly unit in the 1st Embodiment of this invention.

  In the figure, reference numeral 11 denotes a transfer belt unit. The transfer belt unit 11 is disposed in the main body of the apparatus together with the photosensitive drum unit 22 (FIG. 2), and a support member that determines the positions of the photosensitive drum 24 and the transfer belt unit 11. It is detachably attached to the apparatus main body sheet metals 30 and 31 constituting the. The apparatus main body sheet metals 30 and 31 are attached to the bottom member fr at a predetermined interval and are formed so as to protrude vertically, and the first rising parts 301 and 311 and the first rising parts 301 and 311 are formed. First horizontal portions 302 and 312 formed horizontally from the upper end, second rising portions 303 and 313 formed so as to protrude vertically from the tips of the first horizontal portions 302 and 312, and the second The second horizontal portions 304 and 314 formed horizontally from the upper ends of the rising portions 303 and 313 are provided. The grooves 30a to 30c are formed from the first rising portion 301 to the first horizontal portion 302, and the grooves 30d are formed from the second rising portion 303 to the second horizontal portion 304. Grooves 31 a to 31 c are formed from the part 311 to the first horizontal part 312, and a groove 31 d is formed from the second rising part 313 to the second horizontal part 314.

  In the transfer belt unit 11, the driving roller 12 and the idle roller 13 are formed in the grooves 30a, 30b, 31a, and 31b formed in the apparatus main body metal plates 30 and 31 with the ends corresponding to the driving roller 12 and the idle roller 13, respectively. By entering, it is positioned with respect to the apparatus main body. Each transfer roller 15 is positioned with respect to the apparatus main body by entering the grooves 30c and 31c formed in the apparatus main body sheet metal 30 and 31 with the end portions corresponding to the transfer rollers 15.

  After the transfer belt unit 11 is mounted on the apparatus main body, the photosensitive drum unit 22 is formed on the apparatus main body sheet metals 30 and 31 with the shafts 24 a and 24 b of the photosensitive drum 24 corresponding to the respective photosensitive drums 24. By positioning into the grooves 30d and 31d, positioning is performed with respect to the apparatus main body. In FIG. 3, only one photosensitive drum 24 is shown. However, the four photosensitive drums 24 have shafts 24a and 24b inserted into predetermined grooves 30d and 31d of the apparatus main body sheet metals 30 and 31, respectively. , Positioned relative to the apparatus body.

  Next, the attachment state with respect to the apparatus main body of each assembly unit is demonstrated. In this case, the relationship between the transfer roller 15 and the apparatus main body sheet metal 30 will be described. However, since the relationship between the transfer roller 15 and the apparatus main body sheet metal 31 is the same, the description thereof is omitted.

  The transfer roller 15 housed in the transfer belt unit 11 passes through the hole 16 a of the frame 16 constituting the transfer belt unit 11 and is movably disposed with respect to the frame 16. The bearings 35 made of a non-conductive material are detachably attached to both ends. The transfer roller 15 is attached to a bearing 35 by an e-ring 36, and is slidably and rotatably supported in a hole 35b of the bearing 35. Further, when the transfer belt unit 11 is mounted on the apparatus main body, the transfer roller 15 and the bearing 35 are shaped so as not to contact the hole 16 a of the frame 16.

  When the transfer belt unit 11 is mounted on the apparatus main body, the bearing 35 enters the groove 30c of the apparatus main body sheet metal 30. In the bearing 35 and the apparatus main body sheet metal 30, the surface 35c and the surface 30e are replaced by the surface 35d and the surface 30f. Are in contact with each other and moved along the groove 30 c and moved up and down together with the transfer roller 15.

  Further, as shown in FIG. 12, the step surface 15a of the transfer roller 15 and the surface 35a of the bearing 35 are in contact with each other. Therefore, the bearing 35 positions the transfer roller 15 in the axial direction.

  Further, a spring 37 comprising a coil spring as an urging member is disposed on the apparatus main body side. The spring 37 is externally fitted to a protrusion 30 h formed on the apparatus main body sheet metal 30, and when the transfer belt unit 11 is mounted on the apparatus main body, the spring 37 hits the surface 35 f of the bearing 35 and causes the bearing 35 and the transfer roller 15 to move. A biasing force is applied toward the photosensitive drum 24, that is, from the inner surface of the belt 14 toward the outer surface of the belt 14 with a predetermined biasing force. As a result, when the transfer belt unit 11 is mounted on the apparatus main body, the transfer roller 15 is pressed by the urging force against the photosensitive drum 24 arranged to face the transfer roller 15 via the belt 14.

  Reference numeral 38 denotes an electrode disposed in contact with the end face 15 b of the transfer roller 15, and a predetermined transfer voltage generated during printing by a power source (not shown) is applied to the transfer roller 15 via the electrode 38.

  Next, a method for assembling the assembly unit having the above configuration will be described.

  First, when the transfer belt unit 11 is mounted on the apparatus main body, the end portions of the drive roller 12 and the idle roller 13 enter the grooves 30a, 30b, 31a, 31b of the apparatus main body sheet metal 30, 31, and in the drive roller 12 and the idle roller 13, respectively. The position on the apparatus main body sheet metal 30, 31 is determined. Accordingly, the transfer belt unit 11 is positioned with respect to the apparatus main body.

  The bearing 35 attached to the transfer roller 15 enters the grooves 30c and 31c of the apparatus main body sheet metals 30 and 31, and the transfer roller 15 is positioned on the apparatus main body sheet metals 30 and 31 in the axial direction and the conveyance direction of the paper 21. Is decided. At this time, as described above, the spring 37 urges the bearing 35 and the transfer roller 15 with a predetermined urging force from the inner surface of the belt 14 toward the outer surface of the belt 14, and the apparatus main body sheet metals 30 and 31 and the photoconductor. The position of the transfer roller 15 with respect to the drum 24 is determined. The transfer roller 15 is pressed against the photosensitive drum 24 through the belt 14 with a constant pressing force. Accordingly, each transfer roller 15 is positioned with respect to the apparatus main body.

  As described above, in this embodiment, when the transfer belt unit 11 is mounted on the apparatus main body, the transfer belt unit 11 and each transfer roller 15 are both positioned with respect to the apparatus main body, Since they are not in contact, even if the frame 16 is distorted as shown in FIG. 14, the relative position between the transfer roller 15 and the photosensitive drum 24 does not change. Accordingly, each transfer roller 15 can be uniformly pressed against the photosensitive drum 24, so that no white spots occur in the image and the image quality can be improved.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol, and the effect of the same embodiment is used about the effect of the invention by having the same structure. .

  FIG. 15 is a perspective view showing the main part of the assembly unit in the second embodiment of the present invention, FIG. 16 is a front view showing the main part of the assembly unit in the second embodiment of the present invention, and FIG. The perspective view which shows the attachment state of the bearing in the 2nd Embodiment of invention, FIG. 18 is an exploded perspective view of the assembly unit in the 2nd Embodiment of this invention.

  In the present embodiment, as shown in the drawing, a bearing member 41 made of a non-conductive material for rotatably supporting a transfer roller 15 as a transfer member is attached to the apparatus main body sheet metal 30. For this purpose, the apparatus main body sheet metal 30 includes a first rising portion 301 formed to protrude vertically, a first horizontal portion 302 formed horizontally from the upper end of the first rising portion 301, A second rising portion 303 is formed to protrude vertically from the tip of the first horizontal portion 302, and a second horizontal portion 304 is formed horizontally from the upper end of the second rising portion 303. . Grooves 30a, 30c, and 30k are formed from the first rising portion 301 to the first horizontal portion 302, and a groove 30d is formed from the second rising portion 303 to the second horizontal portion 304. The groove 30k includes a wide insertion / removal portion a1 and a narrow guide portion a2 formed above the insertion / removal portion a1, and the bearing member 41 is inserted into and removed from the insertion / removal portion a1. The

  On the other hand, the bearing member 41 includes grooves 41 a and 41 b formed in the height direction on both side surfaces, and concave surfaces 41 d for supporting small diameter portions at both ends of the transfer roller 15 on the upper surface.

  Therefore, the bearing member 41 is inserted into the insertion / removal portion a1 and fitted into the grooves 41a and 41b on the edges 30i and 30j on both sides of the groove 30k, so that the bearing member 41 is moved vertically along the edges 30i and 30j. Can be moved.

  In this case, the position of the bearing member 41 on the apparatus main body sheet metal 30 in the axial direction of the transfer roller 15 and the conveyance direction of the paper 21 as a recording medium is determined by the grooves 41a and 41b and the edges 30i and 30j. Further, the spring 37 as an urging member on the apparatus main body side contacts the surface 41c of the bearing member 41, urges the bearing member 41 upward, and the bearing member 41 abuts against the stopper 30q of the apparatus main body sheet metal 30.

  When the transfer belt unit 11 serving as a belt unit is mounted on the apparatus main body, the transfer roller 15 disposed in the transfer belt unit 11 hits the concave surface 41d of the bearing member 41, and the bearing member in the conveyance direction of the paper 21 The position on 41 is determined. In addition, 31k is a groove.

  In the assembly unit configured as described above, when the transfer belt unit 11 is not attached to the apparatus main body, the bearing member 41 is abutted against the stopper 30q and receives a force from above, along the grooves 41a and 41b. Can be moved downward.

  When the transfer belt unit 11 is mounted on the apparatus main body, the end of the transfer roller 15 in the transfer belt unit 11 rides on the concave surface 41d of the bearing member 41, and the position on the bearing member 41 in the conveyance direction of the paper 21 is It is decided. The transfer roller 15 is smoothly slid on the bearing member 41 and rotated.

  When the photosensitive drum unit 22 is mounted on the apparatus main body, the transfer roller 15 is pushed down by the photosensitive drum 24 as an image carrier, but the spring 37 pushes the transfer roller 15 through the bearing member 41 to the belt 14. Is pressed against the photosensitive drum 24. Therefore, the position of the transfer roller 15 on the apparatus main body sheet metal 30 in the vertical direction is determined. In this way, each transfer roller 15 is positioned with respect to the apparatus main body.

  In the present embodiment, a bearing member 41 is provided on the apparatus main body side instead of the bearing 35, and the shafts at both ends of the transfer roller 15 are directly attached to the apparatus main body. There is no need to attach any accessories. Therefore, the transfer belt unit 11 can be easily attached to and detached from the apparatus main body.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by giving the same code | symbol, About the effect of invention by having the same structure, the effect of the embodiment Is used.

  19 is a perspective view showing the main part of the assembly unit according to the third embodiment of the present invention, FIG. 20 is a front view showing the main part of the assembly unit according to the third embodiment of the present invention, and FIG. FIG. 22 is an exploded perspective view showing an essential part of an assembly unit in the third embodiment of the invention, FIG. 22 is a perspective view of a bearing in the third embodiment of the present invention, and FIG. 23 is a third embodiment of the present invention. FIG. 24 is a perspective view showing a main part of another example of the assembly unit according to the third embodiment of the present invention.

  In this case, the spring 37 as the urging member is connected to the power source 45 on the apparatus main body side, and the bearings 46 attached to both ends of the transfer roller 15 as the transfer member are formed of a conductive material.

  The apparatus main body sheet metal 30 includes a first rising portion 301 formed so as to protrude vertically, a first horizontal portion 302 formed horizontally from the upper end of the first rising portion 301, the first The second rising portion 303 is formed to protrude vertically from the tip of one horizontal portion 302, and the second horizontal portion 304 is formed horizontally from the upper end of the second rising portion 303. Grooves 30a and 30m are formed from the first rising portion 301 to the first horizontal portion 302, and a groove 30d is formed from the second rising portion 303 to the second horizontal portion 304.

  Insulating members 47 made of an insulating material having an L-shaped cross section are attached to both edges of each groove 30m (in FIG. 21, the insulating members 47 are attached to both edges of one groove 30m. Actually, the grooves 47a are attached to both edges of all the grooves 30m.) A groove 47a is formed between the insulating members 47, and the position of the transfer roller 15 is determined in the conveyance direction of the paper 21.

  When the transfer belt unit 11 is mounted on the apparatus main body, each bearing 46 enters each groove 47a, and in the bearing 46 and the apparatus main body sheet metal 30, the surface 46c and the surface 47d are brought into contact with each other, and the surface 46d and the surface 47c are brought into contact with each other. In this state, it slides along the groove 30 m and is moved up and down together with the transfer roller 15.

  In the present embodiment, a voltage necessary for transfer at the time of printing is directly applied to the transfer roller 15 through the spring 37 from the apparatus main body side.

  As described above, in the present embodiment, the voltage necessary for the transfer can be supplied to the transfer roller 15 using the spring 37 urging the transfer roller 15, so that it is not necessary to use an electrode. . Therefore, since the number of parts can be reduced, not only can the structure of the printer be simplified, but also the cost of the printer can be reduced.

  In the present embodiment, as shown in FIG. 24, a spring 51 composed of a leaf spring as an urging member can be used. The spring 51 is attached to the apparatus main body side and connected to a power source 45 on the apparatus main body side.

  When the transfer belt unit 11 is attached to the apparatus main body, the transfer roller 15 is rotatably supported at the upper end of the spring 51. The spring 51 urges the transfer roller 15 from the inner surface of the belt 14 toward the outer surface of the belt 14 with a predetermined urging force.

  Accordingly, the position of the transfer roller 15 on the apparatus main body sheet metal 30 in the vertical direction is determined. In this way, each transfer roller 15 is positioned with respect to the apparatus main body.

  In printing, a voltage necessary for transfer at the time of printing is directly applied to the transfer roller 15 through the spring 51 from the apparatus main body side.

  As described above, in this embodiment, a bearing for rotatably supporting the transfer roller 15 is not required, and an electrode for applying a voltage to the transfer roller 15 is not required. In addition to simplifying the structure of the printer, the cost of the printer can be reduced.

  Next, a fourth embodiment of the present invention will be described.

  FIG. 25 is a perspective view of a transfer belt unit according to the fourth embodiment of the present invention.

  In this case, the frame 16, the transfer roller 15, and the bearing 35 are prevented from contacting each other between the frame 16 of the transfer belt unit 11 as a belt unit and the bearing 35 attached to the transfer roller 15 as a transfer member. A buffer member 55 for buffering is disposed. The buffer member 55 is attached to the frame 16 and is slid with the bearing 35. The buffer member 55 is hardened so as not to affect the position of the transfer roller 15, which is positioned by the apparatus main body when the transfer belt unit 11 is attached to the apparatus main body.

  When the transfer belt unit 11 is not attached to the apparatus main body, the movement of the transfer roller 15 is forced by the buffer member 55 via the bearing 35, so that force is applied to the transfer roller 15, the transfer belt unit 11 and the like. Even if added, the bearing 35 attached to the transfer roller 15 and the frame 16 are not in direct contact.

  Thus, in the present embodiment, in the transfer belt unit 11 that is not attached to the apparatus main body, the buffer member 55 is provided between the bearing 35 attached to the transfer roller 15 and the frame 16 of the transfer belt unit 11. Therefore, when the transfer belt unit 11 is mounted on the apparatus main body, the transfer roller 15 or the bearing 35 is placed at a predetermined position on the apparatus main body. Can be set easily.

  Further, since the transfer roller 15 or the bearing 35 and the frame 16 of the transfer belt unit 11 can be prevented from interfering with each other, it is possible to prevent each element of the transfer belt unit 11, the frame 16 and the like from being damaged. it can.

  Next, a fifth embodiment of the present invention will be described.

  FIG. 26 is a perspective view of a transfer belt unit according to the fifth embodiment of the present invention.

  In this case, a fixing member 58 as a position forcing member for fixing the bearing 35 to the frame 16 is detachably disposed between the frame 16 and the bearing 35. That is, when the fixing member 58 is attached to the frame 16, the fixing member 58 blocks the movement of the bearing 35, and the position of the transfer roller 15 as the transfer member is determined and fixed by the bearing 35. Further, the transfer roller 15 is supported rotatably. On the other hand, when the fixing member 58 is removed from the frame 16, the transfer roller 15 and the bearing 35 can be freely moved.

  As described above, in this embodiment, the fixing member 58 that prevents the movement of the bearing 35 is attached to the frame 16 of the transfer belt unit 11 as a belt unit that is not attached to the apparatus main body, so that the transfer belt unit 11 can be moved. Since the bearing 35 and the transfer roller 15 can be prevented from moving relative to each other when not in use or transported, each element of the transfer belt unit 11, the frame 16 and the like can be prevented from being damaged. Can do.

  In this embodiment, an example in which the transfer belt unit 11 is mounted on the apparatus main body from above is described. However, the transfer belt unit 11 can be mounted from the front and side.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a 1st perspective view which shows the principal part of the assembly unit in the 1st Embodiment of this invention. 1 is a schematic diagram of a printer according to a first embodiment of the present invention. It is a disassembled perspective view of the assembly unit in the 1st Embodiment of this invention. It is a 1st perspective view of the assembly unit in the 1st Embodiment of this invention. It is a 2nd perspective view which shows the principal part of the assembly unit in the 1st Embodiment of this invention. It is a front view which shows the principal part of the assembly unit in the 1st Embodiment of this invention. It is a perspective view which shows the arrangement | positioning state of the spring in the 1st Embodiment of this invention. It is a figure which shows operation | movement of the spring in the 1st Embodiment of this invention. It is a perspective view which shows the attachment state of the bearing in the 1st Embodiment of this invention. It is a perspective view of the bearing in the 1st Embodiment of this invention. It is a perspective view of the apparatus main body sheet metal in the 1st Embodiment of this invention. It is a top view which shows the attachment state of the transfer roller in the 1st Embodiment of this invention. FIG. 3 is a perspective view of a transfer belt unit according to the first embodiment of the present invention. It is a 2nd perspective view of the assembly unit in the 1st Embodiment of this invention. It is a perspective view which shows the principal part of the assembly unit in the 2nd Embodiment of this invention. It is a front view which shows the principal part of the assembly unit in the 2nd Embodiment of this invention. It is a perspective view which shows the attachment state of the bearing in the 2nd Embodiment of this invention. It is a disassembled perspective view of the assembly unit in the 2nd Embodiment of this invention. It is a perspective view which shows the principal part of the assembly unit in the 3rd Embodiment of this invention. It is a front view which shows the principal part of the assembly unit in the 3rd Embodiment of this invention. It is a disassembled perspective view which shows the principal part of the assembly unit in the 3rd Embodiment of this invention. It is a perspective view of the bearing in the 3rd Embodiment of this invention. It is a perspective view of the apparatus main body sheet metal in the 3rd Embodiment of this invention. It is a perspective view which shows the principal part of the other example of the assembly unit in the 3rd Embodiment of this invention. It is a perspective view of the transfer belt unit in the 4th Embodiment of this invention. It is a perspective view of the transfer belt unit in the 5th Embodiment of this invention.

Explanation of symbols

11 Transfer belt unit 12 Drive roller 13 Idle roller 14 Belt 15 Transfer roller 15
16 Frame 21 Paper 30, 31 Device body sheet metal 37, 51 Spring 41 Bearing member 55 Buffer member 58 Fixing member

Claims (7)

(A) an image carrier;
(B) an apparatus body;
(C) a belt unit that includes at least two rollers, a belt stretched between the rollers, and a frame, and is detachably disposed on the apparatus body;
(D) In the belt unit, a transfer member that is loosely fitted into the hole formed in the frame and transfers the developer image formed on the image carrier to a recording medium. When,
(E) a support member that is disposed in the apparatus main body, is formed by bending a plate-like member, supports the image carrier and the transfer member rotatably, and positions the image carrier relative to the apparatus main body;
(F) One end is supported by the support member, and when the belt unit is attached to the apparatus main body, the transfer member loosely fitted in a hole formed in the frame is directed toward the image carrier. And an urging member for urging the image forming apparatus.   The image forming apparatus according to claim 1, further comprising a bearing member that is detachably disposed with respect to the support member and rotatably supports the transfer member.   The image forming apparatus according to claim 2, wherein when the belt unit is attached to the apparatus main body, the transfer member and the bearing member are prevented from contacting the frame. (A) the biasing member is connected to a power source;
(B) The image forming apparatus according to claim 1, wherein the voltage of the power source is applied to the transfer member via an urging member. (A) the biasing member is made of a conductive material;
The image forming apparatus according to claim 1, wherein the support member is made of an insulating material.   The image forming apparatus according to claim 1, wherein a buffer member is disposed between the frame and the transfer member.   The image forming apparatus according to claim 1, wherein a position forcing member is disposed between the frame and the transfer member.

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