Image forming apparatus

Abstract

To provide a metal frame of an image forming apparatus that can achieve both the easiness of assembly of two metal plates forming the metal frame and an improvement in positioning accuracy.SOLUTION: In the image forming apparatus, a frame body 31 has a rear side plate 52 that has a plane part 52a and a bent part 52b, and a rear bottom plate 51 that supports the rear side plate 52 below the rear side plate 52, the rear bottom plate 51 having a plane part 51w1, a bent and erected part 51w2 bent substantially perpendicularly upward in the vertical direction from an end in an arrow Y direction of the plane part 51w1 and engaged and assembled with the plane part 52a, and a bent and erected part 51w4 bent substantially perpendicularly upward in the vertical direction from an end in an arrow X direction of the plane part 51w1 and engaged and assembled with the bent part 52b. When seen from the vertical direction, a portion of the bent and erected part 51w4 in contact with or in most proximity to the bent and erected pat 51w2 is located at a position different from a corner part 52h of the rear side plate 52.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer, etc.). to It relates to.

Background Art

[0002] Generally, the frame of an image forming apparatus is formed by fixing a plurality of sheet metals such as a front side plate, a rear side plate, and a stay connecting the front side plate and the rear side plate by welding or the like. By fixing each of these sheet metals with high positional accuracy, the positional accuracy between the members supported by the frame is maintained, and it becomes possible to form a high-quality image.

[0003] On the other hand, Patent Document 1 describes a configuration for assembling a first sheet metal and a second sheet metal, which are sheet metals constituting the frame of an image forming apparatus, with high positional accuracy. The configuration described in Patent Document 1 is a configuration in which a protruding portion formed on the first sheet metal is inserted into an opening formed on the second sheet metal to assemble the two. Inside the opening of the second sheet metal, a first bulging portion that abuts on one surface in the plate thickness direction of the protruding portion of the first sheet metal and a second bulging portion that abuts on the other surface are formed. By sandwiching the protruding portion from the plate thickness direction by these first bulging portion and second bulging portion, the position in the plate thickness direction of the first sheet metal with respect to the second sheet metal is determined. Further, in the direction orthogonal to the insertion direction of the first sheet metal with respect to the second sheet metal and the plate thickness direction of the first sheet metal, by making the width of the opening and the width of the protruding portion substantially the same, the position in the orthogonal direction of the first sheet metal with respect to the second sheet metal is determined.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When assembling and positioning two sheet metals that constitute the frame of an image forming apparatus, it is desirable to make it easier to assemble one sheet metal to the other. However, if the difference between the size of the opening and the thickness and width of the protruding portion is increased to achieve this, the positioning accuracy between the sheet metals decreases, and the positional accuracy between the members supported by the frame deteriorates, which may have an adverse effect on the image quality. In the conventional configuration as described above, in the configuration where the sheet metals are engaged and positioned, it has been difficult to achieve both ease of assembly and improvement in positioning accuracy.

[0006] Therefore, in view of such a situation, the present invention provides an image forming apparatus capable of achieving both ease of assembly and improvement in positioning accuracy of two sheet metals constituting a metal frame. into An object of the present invention is to provide such an apparatus.

Means for Solving the Problems

[0007] A typical configuration of the present invention for achieving the above object includes an image forming unit, a first sheet metal, and a second sheet metal connected under the first sheet metal, and includes a metal frame that supports the image forming unit. The first sheet metal includes a first portion extending along a vertical direction and including a surface extending along a first horizontal direction intersecting the vertical direction, a second portion extending along the vertical direction and including a surface extending along a second horizontal direction intersecting the vertical direction and the first horizontal direction, and a first corner formed between the first portion and the second portion. The second sheet metal includes a surface substantially parallel to the surface included in the first portion, a third portion assembled to the first portion, a surface substantially parallel to the surface included in the second portion, a fourth portion assembled to the second portion, and in the first horizontal direction, from the edge of the third portion closer to the fourth portion, in a direction intersecting the surface included in the first portion , starting from the first corner portion and moving in the direction in which the second portion extends from the first portion a fifth portion bent, and a second corner formed between the third portion and the fifth portion, and in the first horizontal direction, the first corner and the second corner are arranged at different positions.

Effects of the Invention

[0008] According to the present invention 、 it is possible to achieve both an improvement in the ease of assembly and the positioning accuracy of two sheet metals constituting a metal frame.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] <Image forming apparatus> Hereinafter, the overall configuration of the image forming apparatus according to the present invention will be described with reference to the drawings together with the operations during image formation. Note that the dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention only to these, unless otherwise specifically described.

[0011] The image forming apparatus A according to the present embodiment is an intermediate tandem type image forming apparatus that transfers four-color toners of yellow (Y), magenta (M), cyan (C), and black (K) to an intermediate transfer belt and then transfers an image to a sheet to form an image. In the following description, although suffixes Y, M, C, and K are attached to the members that use the above-mentioned toners of each color, the configurations and operations of each member are substantially the same except that the colors of the toners used are different. Therefore, the suffixes are appropriately omitted unless distinction is required.

[0012] FIG. 1 is a schematic perspective view of the image forming apparatus A. FIG. 2 is a schematic cross-sectional view of the image forming apparatus A. As shown in FIGS. 1 and 2, the image forming apparatus A includes an image forming unit 44 that forms a toner image and transfers it to a sheet, a sheet feeding unit 43 that supplies a sheet toward the image forming unit 44, and a fixing unit 45 that fixes the toner image on the sheet. An image reading unit 41 for reading an image of a document is provided above the image forming apparatus A.

[0013] The image forming unit 44 includes process cartridges 3 (3Y, 3M, 3C, 3K), a laser scanner unit 15, and an intermediate transfer unit 49. The process cartridge 3, which is an example of an image forming unit, is configured to be detachable from the image forming apparatus A and includes photosensitive drums 6 (6Y, 6M, 6C, 6K), charging rollers 8 (8Y, 8M, 8C, 8K), and developing devices 4 (4Y, 4M, 4C, 4K).

[0014] The intermediate transfer unit 49 includes primary transfer rollers 5 (5Y, 5M, 5C, 5K), an intermediate transfer belt 14, a secondary transfer roller 28, a secondary transfer opposing roller 23, a driving roller 21, and a tension roller 22. The intermediate transfer belt 14 is stretched around the secondary transfer opposing roller 23, the driving roller 21, and the tension roller 22, and the driving roller 21 rotates by the driving force of a motor (not shown), and moves circumferentially following the rotation.

[0015] Next, the image forming operation by the image forming apparatus A will be described. First, when an image forming job signal is input to a control unit (not shown), a sheet S loaded and stored in a sheet cassette 42 is sent out by a feed roller 16 to a registration roller 9. Next, the sheet S is fed into a secondary transfer portion formed by a secondary transfer roller 28 and a secondary transfer counter roller 23 at a predetermined timing by the registration roller 9.

[0016] On the other hand, in the image forming section, first, the surface of the photosensitive drum 6Y is charged by a charging roller 8Y. Then, a laser scanner unit 15 irradiates the surface of the photosensitive drum 6Y with laser light according to an image signal transmitted from an external device (not shown) or the like, and an electrostatic latent image is formed on the surface of the photosensitive drum 6Y.

[0017] Thereafter, a yellow toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum 6Y by a developing device 4Y, and a yellow toner image is formed on the surface of the photosensitive drum 6Y. The toner image formed on the surface of the photosensitive drum 6Y is primarily transferred to the intermediate transfer belt 14 by applying a bias to a primary transfer roller 5Y.

[0018] By the same process, magenta, cyan, and black toner images are also formed on the photosensitive drums 6M, 6C, and 6K. Then, by applying a primary transfer bias to the primary transfer rollers 5M, 5C, and 5K, these toner images are superposed and transferred onto the yellow toner image on the intermediate transfer belt 14. Thereby, a full-color toner image is formed on the surface of the intermediate transfer belt 14.

[0019] Note that the toner inside the developing device 4 is used by the above-described developing process, and when the amount of toner inside the developing device 4 decreases, each developing device 4 is supplied with toner of each color by toner bottles 32 (32Y, 32M, 32C, 32K). The toner bottles 32 are configured to be detachable from the image forming apparatus A.

[0020] Thereafter, as the intermediate transfer belt 14 moves in a circular motion, the full-color toner image is sent to the secondary transfer unit. Then, by applying a bias to the secondary transfer roller 28 in the secondary transfer unit, the full-color toner image on the intermediate transfer belt 14 is transferred to the sheet S.

[0021] Next, the sheet S onto which the toner image has been transferred is subjected to heating and pressurizing processes in the fixing unit 45, whereby the toner image on the sheet S is fixed to the sheet S. Thereafter, the sheet S onto which the toner image has been fixed is discharged to the discharge unit 19 by the discharge roller 18.

[0022] <Frame of the image forming apparatus> Next, the frame 31 (metal frame) of the image forming apparatus A will be described.

[0023] FIG. 3 is a perspective view of the frame 31 of the image forming apparatus A as viewed from the front side of the image forming apparatus A, and is a perspective view in a state where internal units such as the image forming unit and the exterior cover are removed from the frame 31. FIG. 4 is a perspective view of the frame 31 of the image forming apparatus A as viewed from the back side of the image forming apparatus A. The arrow X direction shown in the figure is the horizontal direction and indicates the left and right direction of the image forming apparatus A. The arrow Y direction is the horizontal direction and indicates the front and back direction of the image forming apparatus A. The arrow Z direction is the vertical direction and indicates the up and down direction of the image forming apparatus A. The front side of the image forming apparatus A is the side where a normal user stands to operate the operation unit 46 for performing settings related to image formation, and the back side is the side opposite to the front side through the frame 31. The left side of the image forming apparatus A is the left side as viewed from the front side, and the right side is the right side as viewed from the front side. Also, the front side of the image forming apparatus A is the direction in which the sheet cassette 42 is pulled out with respect to the image forming apparatus A when replenishing the sheet cassette 42 with sheets, and is the direction in which the toner bottle 32 is pulled out when replacing the toner bottle 32.

[0024] As shown in FIGS. 3 and 4, the image forming apparatus A includes a front frame 31, which, as a second support, comprises a front plate 55 (third side plate) formed of sheet metal, a left support column 56 (first support column), and a right support column 67 (second support column). The left support column 56 is connected to one end side of the front plate 55 in the direction of arrow X and supports the front plate 55. The right support column 67 is connected to the other end side of the front plate 55 in the direction of arrow X and supports the front plate 55. The right support column 67 is composed of a right support column 58 and a right support column 63 connected vertically above the right support column 58. The left support column 56 and the right support column 58 are connected by a front lower stay 57.

[0025] The image forming apparatus A also includes a rear frame 31 on its rear side, which, as a first support, comprises a rear plate 50 and a rear bottom plate 51 formed of sheet metal. The rear plate 50 is disposed opposite to the front plate 55 and supports the process cartridge 3 together with the front plate 55. The rear plate 50 is vertically divided into three parts as a rear plate 52, a rear plate 53, and a rear plate 62. The rear plate 53 (first side plate) is connected above the rear plate 52 (second side plate) in the vertical direction, and the rear plate 62 is connected above the rear plate 53 in the vertical direction. The sheet thickness of each of the sheet metals of the rear plates 52, 53, and 62 is about 0.6 mm to 2 mm.

[0026] The image forming apparatus A also includes a frame 31 that connects the front frame 31 and the rear frame 31 on its front side, which comprises a lower left stay 59, an upper left stay 60, a lower right stay 61, a middle right stay 65, an upper right stay 64, and a middle stay 54. Here, the lower left stay 59, the upper left stay 60, the lower right stay 61, the middle right stay 65, the upper right stay 64, and the middle stay 54 are an example of a connecting member that connects the rear plate 50, which is the rear frame 31, and the front plate 55, the left support column 56, and the right support column 67, which are the front frame 31, and is an example of a third support. The lower left stay 59 connects the left support column 56 and the rear plate 52. The upper left stay 60 connects the left support column 56 and the rear plate 53. The lower right stay 61 connects the right support column 58 and the rear plate 52. The middle right stay 65 connects the rear plate 53 and the right support column 58. The upper right stay 64 connects the right support column 63 and the rear plate 62. The middle stay 54 connects the front plate 55 and the rear plate 53.

[0027] Note that each member constituting the above-described frame body 31 is formed from a single sheet of sheet metal. These sheets of sheet metal are processed into a predetermined shape by drawing or the like, temporarily assembled in the assembly process described later, and then fixed through a fixing process to become the frame body 31.

[0028] <Frame body assembly process> Next, a process of assembling a plurality of sheets of sheet metal constituting the frame body 31 will be described. FIGS. 5 to 30 are diagrams showing how each sheet of sheet metal constituting the frame body 31 is assembled.

[0029] As shown in FIG. 5, when assembling each sheet of sheet metal constituting the frame body 31, a mounting table 33 as a first jig is used. The mounting table 33 has a base portion provided with positioning pins 33a and 33b, and a support column 33c erected on the base portion. First, the rear bottom plate 51 is placed on the mounting table 33.

[0030] The rear bottom plate 51 (second sheet of sheet metal) faces the mounting table 33 and includes a flat portion 51w1 (third portion) extending in the horizontal direction. Further, the rear bottom plate 51 includes bent-up portions 51w2 (fourth portion) and 51w3 where one end and the other end in the arrow Y direction (first direction) orthogonal to the vertical direction (arrow Z direction) of the flat portion 51w1 are bent upward substantially perpendicularly (89 degrees to 90 degrees). Further, the rear bottom plate 51 includes bent-up portions 51w4 (fifth portion) and 51w5 where one end and the other end in the arrow X direction (second direction) orthogonal to the vertical direction (arrow Z direction) and the arrow Y direction of the flat portion 51w1 are bent upward substantially perpendicularly (89 degrees to 90 degrees). The bent-up portions 51w2 to 51w5 are formed on at least the side that engages with the rear side plate 52.

[0031] When the rear bottom plate 51 is placed on the mounting table 33, the positioning pin 33a of the mounting table 33 is inserted into the positioning hole 51a formed in the flat portion 51w1 of the rear bottom plate 51. Thereby, the position of the rear bottom plate 51 with respect to the mounting table 33 is determined.

[0032] Next, as shown in FIG. 6, the rear side plate 52 (the first sheet metal) is inserted and assembled into the rear bottom plate 51 from the vertical direction (the direction of arrow Z). The rear side plate 52 is bent so as to have a U-shaped cross-section having three planes. The rear side plate 52 includes a flat portion 52a (the first portion) located on the back surface of the image forming apparatus A, and a bent portion 52b (the second portion) that is bent so that the bending angle with respect to the flat portion 52a is substantially perpendicular (89 degrees to 91 degrees) and extends rearward of the image forming apparatus A. The flat portion 52a and the bent portion 52b form a corner portion 52h by bending. The rear side plate 52 also includes a bent portion 52w that is bent with respect to the flat portion 52a so as to face the bent portion 52b.

[0033] On the upper portion of the flat portion 52a of the rear side plate 52, a stepped portion 52a1 is provided that is bent in the thickness direction (the direction of arrow Y) of the flat portion 52a so that a step can be formed in the direction of arrow Y between the flat portion 52a. On the upper portion of the bent portion 52b of the rear side plate 52, a stepped portion 52b1 is provided that is bent in the thickness direction (the direction of arrow X) of the bent portion 52b so that a step can be formed in the direction of arrow X between the bent portion 52b. On the upper portion of the bent portion 52w of the rear side plate 52, a stepped portion 52w1 is provided that is bent in the thickness direction (the direction of arrow X) of the bent portion 52w so that a step can be formed in the direction of arrow X between the bent portion 52w.

[0034] As shown in FIG. 6(b), on the lower portion of the flat portion 52a of the rear side plate 52, a protruding portion 52n is provided that is formed to protrude by drawing in the thickness direction thereof. Further, a through hole 51n that penetrates in the thickness direction (the direction of arrow Y) is formed in the bent-up portion 51w2 of the rear bottom plate 51. When the rear side plate 52 is assembled, the protruding portion 52n of the rear side plate 52 engages with the through hole 51n of the rear bottom plate 51. As a result, the edge portion 52n1 of the protruding portion 52n abuts against the inner wall of the through hole 51n, and movement of the rear side plate 52 in the direction opposite to the insertion direction with respect to the rear bottom plate 51 is restricted.

[0035] FIG. 7 is a perspective view of the region U1 shown in FIG. 6. Here, FIG. 7(a) shows the state before the rear side plate 52 is assembled to the rear bottom plate 51. FIG. 7(b) shows the state where the rear side plate 52 is assembled to the rear bottom plate 51. FIG. 8 is a top view of the rear bottom plate 51 in the region U1 shown in FIG. 6.

[0036] As shown in FIGS. 7 and 8, a stepped bending portion 52m (first engaging portion) is formed at the lower part of the flat portion 52a of the rear side plate 52. The stepped bending portion 52m has a portion (third bending portion) bent in the plate thickness direction (arrow Y direction) of the flat portion 52a and a portion (fourth bending portion) bent and extending in the insertion direction (arrow Z direction) with respect to the rear bottom plate 51 from that portion. The tip of the stepped bending portion 52m is an inclined portion 52m1 that inclines in a direction away from the flat portion 52a of the rear side plate 52 with respect to the insertion direction of the rear side plate 52 with respect to the rear bottom plate 51.

[0037] Also, a stepped bending portion 52p (second engaging portion) is provided at the lower part of the bending portion 52b of the rear side plate 52. The stepped bending portion 52p has a portion (fifth bending portion) bent in the plate thickness direction (arrow X direction) of the bending portion 52b and a portion (sixth bending portion) bent and extending in the insertion direction with respect to the rear bottom plate 51 from that portion. The tip of the stepped bending portion 52p is an inclined portion 52p1 that inclines in a direction away from the bending portion 52b of the rear side plate 52 with respect to the insertion direction of the rear side plate 52 with respect to the rear bottom plate 51.

[0038] When the rear side plate 52 is assembled, the stepped bending portions 52m and 52p of the rear side plate 52 engage with the bent-up portions 51w2 and 51w4 of the rear bottom plate 51. At this time, the inclined portions 52m1 and 52p1 of the rear side plate 52 abut against the bent-up portions 51w2 and 51w4 of the rear bottom plate 51, and the movement of the rear side plate 52 in the arrow Z direction is guided. As a result, the bent-up portion 51w2 of the rear bottom plate 51 is sandwiched in its plate thickness direction by the stepped bending portion 52m and the flat portion 52a of the rear side plate 52, and the bent-up portion 51w4 of the rear bottom plate 51 is sandwiched in its plate thickness direction by the stepped bending portion 52p and the bending portion 52b. In this way, the positions of the rear side plate 52 with respect to the rear bottom plate 51 in the arrow X direction and the arrow Y direction are determined.

[0039] Also, when the rear side plate 52 is inserted into the rear bottom plate 51 up to a position where the lower end portion of the rear side plate 52 abuts against the surface of the mounting base 33 on which the rear bottom plate 51 is placed, or up to a position where the portions bent from the flat portions 52a, 52b of the stepped bending portions 52m, 52p abut against the upper end portions of the bending portions 51w2 of the rear bottom plate 51, the positions of the rear side plate 52 and the rear bottom plate 51 in the arrow Z direction are determined, and the final relative positions of the rear bottom plate 51 and the rear side plate 52 are determined.

[0040] Also, bending portions 51j (second bending portions) and 51k (first bending portions) are provided on the bending portions 51w2 and 51w4 of the rear bottom plate 51 to block at least a part of the notch portions 51w6 formed in the rear bottom plate 51. The notch portions 51w6 are notches required when performing bending processing for forming the bending portions 51w2 and 51w4 of the rear bottom plate 51.

[0041] The bending portion 51j is formed by being bent substantially perpendicular (89 degrees to 91 degrees) in the arrow X direction from the end portion of the bending portion 51w4 in the arrow Y direction toward the bending portion 51w2. The bending portion 51k is formed by being bent substantially perpendicular (89 degrees to 91 degrees) in the arrow Y direction from the end portion of the bending portion 51w2 in the arrow X direction toward the bending portion 51w4. The tip portion 51j1 of the bending portion 51j is the portion closest to the bending portion 51w2 in the bending portion 51w4. In other words, the side surface portion 51k1 of the bending portion 51k is the portion closest to the bending portion 51w4 in the bending portion 51w2. The gap V1 between the tip portion 51j1 of the bending portion 51j and the side surface portion 51k1 of the bending portion 51k shown in FIG. 8 is equal to or less than the plate thickness of the bending portion 52b of the rear side plate 52. Note that the bending portion 51j and the bending portion 51k may be configured to be in contact with each other without providing the gap V1.

[0042] FIG. 9 is a perspective view showing the processing methods of the bending-up portions 51w2 and 51w4 and the bending portions 51j and 51k in sequence. As shown in FIGS. 9(a) and 9(b), when forming the bending-up portions 51w2 and 51w4 and the bending portions 51j and 51k, first, the corner portions around the notch portion 51w6 in the rear bottom plate 51 are bent substantially vertically upward to form the bending portions 51j and 51k. Next, as shown in FIG. 9(c), one end portion in the arrow X direction and one end portion in the arrow Y direction of the flat portion 51w1 are bent up substantially vertically upward to form the bending-up portions 51w2 and 51w4. In this way, the bending-up portions 51w2 and 51w4 and the bending portions 51j and 51k are bent.

[0043] When the rear side plate 52 is assembled to the rear bottom plate 51, the provision of the bending portions 51j and 51k on the rear bottom plate 51 has the following effect. That is, as shown in FIG. 10(a), if the bending portion 51j is not provided, when the rear side plate 52 is inserted into the rear bottom plate 51, the corner portion 52h of the rear side plate 52 enters the space above the notch portion 51w6, and both the bending portion 52b and the stepped bending portion 52p of the rear side plate 52 may be inserted into one side with respect to the bending-up portion 51w4 of the rear bottom plate 51. In this case, the stepped bending portion 52p does not engage, and the bending portion 52b and the stepped bending portion 52p of the rear side plate 52 cannot sandwich the bending-up portion 51w4 of the rear bottom plate 51, so the relative position accuracy between the rear bottom plate 51 and the rear side plate 52 deteriorates.

[0044] On the other hand, as shown in FIG. 10(b), by providing the bending portion 51j on the rear bottom plate 51, when the rear side plate 52 is about to be inserted into the wrong position with respect to the rear bottom plate 51, the lower end portion of the bending portion 52b of the rear side plate 52 interferes with the bending portion 51j of the rear bottom plate 51. For this reason, the rear side plate 52 cannot be inserted all the way into the rear bottom plate 51. Therefore, it is possible to suppress the rear side plate 52 from being assembled to the wrong position with respect to the rear bottom plate 51, and it is possible to suppress the deterioration of the relative position accuracy between the rear bottom plate 51 and the rear side plate 52.

[0045] Also, as shown in Fig. 11(a), if the bending portion 51k is not provided, when the rear side plate 52 is inserted into the rear bottom plate 51, the corner portion 52h of the rear side plate 52 enters the space above the notch portion 51w6, and both the flat portion 52a and the stepped bending portion 52m of the rear side plate 52 may be inserted on one side with respect to the bending raised portion 51w2. In this case, the stepped bending portion 52m does not engage, and the bending raised portion 51w2 of the rear bottom plate 51 cannot be sandwiched between the flat portion 52a and the stepped bending portion 52m of the rear side plate 52, so the relative position accuracy between the rear bottom plate 51 and the rear side plate 52 deteriorates.

[0046] On the other hand, as shown in Fig. 11(b), by providing the bending portion 51k on the rear bottom plate 51, when the rear side plate 52 is about to be inserted into the wrong position with respect to the rear bottom plate 51, the lower end portion of the flat portion 52a of the rear side plate 52 interferes with the bending portion 51k of the rear bottom plate 51. For this reason, the rear side plate 52 cannot be inserted all the way into the rear bottom plate 51. Therefore, it is possible to suppress the rear side plate 52 from being assembled to the rear bottom plate 51 at the wrong position, and it is possible to suppress the deterioration of the relative position accuracy between the rear bottom plate 51 and the rear side plate 52.

[0047] That is, in order to ensure the strength of the rear bottom plate 51 and assemble the rear side plate 52, the bending raised portions 51w2 to 51w5 are required on the rear bottom plate 51. In order to bend the bending raised portions 51w2 to 51w5, notches such as the notch portion 51w6 are required. If the notch portion 51w6 is left as it is, as shown in Figs. 10(a) and 11(a), the rear side plate 52 may enter the space above the notch portion 51w6, and the rear side plate 52 may be assembled at the wrong position.

[0048] On the other hand, bending portions 51j and 51k are provided to block at least a part of the notch portion 51w6, and the portion of the bending-up portion 51w4 that contacts or is closest to the bending-up portion 51w2 when viewed from the vertical direction is arranged at a position different from the corner portion 52h of the rear side plate 52. With such a configuration, when the rear side plate 52 is about to be assembled at the above-described incorrect position, the bending-up portions 51w2 and 51w4 interfere with the rear side plate 52 to restrict the assembly, so that the rear side plate 52 can be prevented from being assembled at the incorrect position. Therefore, according to the configuration of the present embodiment, it is possible to achieve both an improvement in the ease of assembly and the positioning accuracy between the rear bottom plate 51 and the rear side plate 52, which are two sheet metals constituting the frame body 31.

[0049] In the present embodiment, although the configuration in which at least a part of the notch portion 51w6 is blocked by the two bending portions 51j and 51k of the rear bottom plate 51 to prevent the rear side plate 52 from being inserted into the incorrect position has been described, the present invention is not limited thereto. That is, any configuration in which the portion of the bending-up portion 51w4 that contacts or is closest to the bending-up portion 51w2 when viewed from the vertical direction is arranged at a position different from the corner portion 52h of the rear side plate 52 can obtain the same effect as described above. For example, the configuration shown in FIG. 12(a) in which the notch portion 51w6 is blocked by one bending portion 51j or the configuration shown in FIG. 12(b) in which the notch portion 51w6 is blocked by one bending portion 51k may be used.

[0050] Next, as shown in FIG. 13, the rear side plate 53 that supports the process cartridge 3 is inserted and assembled into the rear side plate 52 from the vertical direction (arrow Z direction). The rear side plate 53 is bent so as to have a U-shaped cross section having three planes. The rear side plate 53 is located at the back of the image forming apparatus A, and includes a support portion 53a that supports the process cartridge 3 and a bending portion 53b that is bent so that the bending angle with respect to the support portion 53a is substantially perpendicular (89 degrees to 91 degrees) and extends rearward of the image forming apparatus A. The support portion 53a and the bending portion 53b form a corner portion 53h by bending. The rear side plate 53 also includes a bending portion 53w that is bent with respect to the support portion 53a so as to face the bending portion 53b.

[0051] The support portion 53a (first part) of the rear side plate 53 (first sheet metal) is arranged adjacent to the flat portion 52a (third part) of the rear side plate 52 (second sheet metal) vertically above the flat portion 52a. Further, the bent portion 53b (second part) of the rear side plate 53 is arranged adjacent to the bent portion 52b (fourth part) of the rear side plate 52 vertically above the bent portion 52b. Also, the bent portion 53w of the rear side plate 53 is arranged adjacent to the bent portion 52w of the rear side plate 52 vertically above the bent portion 52w.

[0052] As shown in FIG. 13(b), a protrusion 53i is provided at the lower part of the support portion 53a of the rear side plate 53 so as to protrude by drawing in the plate thickness direction. Also, a through hole 52i penetrating in the plate thickness direction (arrow Y direction) is formed in the stepped portion 52a1 of the rear side plate 52. When the rear side plate 53 is assembled, the protrusion 53i of the rear side plate 53 engages with the through hole 52i of the rear side plate 52. Thereby, the edge portion 53i1 of the protrusion 53i abuts against the inner wall of the through hole 52i, and movement of the rear side plate 53 in the direction opposite to the insertion direction with respect to the rear side plate 52 is restricted.

[0053] FIG. 14 is a perspective view of the region U2 shown in FIG. 13. Here, FIG. 14(a) shows a state before the rear side plate 52 is assembled to the rear bottom plate 51. FIG. 14(b) shows a state where the rear side plate 52 is assembled to the rear bottom plate 51. FIG. 15 is a top view of the rear side plate 52 in the region U2 shown in FIG. 13.

[0054] As shown in FIGS. 14 and 15, a stepped bent portion 53m (first engaging portion) is formed at the lower part of the support portion 53a of the rear side plate 53. The stepped bent portion 53m has a portion (third bent portion) bent in the plate thickness direction (arrow Y direction) of the support portion 53a and a portion (fourth bent portion) bent and extending in the insertion direction (arrow Z direction) with respect to the rear side plate 52 from that portion. The tip of the stepped bent portion 53m is an inclined portion 53m1 inclined in a direction away from the support portion 53a of the rear side plate 53 with respect to the insertion direction of the rear side plate 53 with respect to the rear side plate 52.

[0055] In addition, a stepped bending portion 53p (second engaging portion) and a stopper portion 53r are provided at the lower part of the bending portion 53b of the rear side plate 53. The stopper portion 53r is formed by press working and protrudes in the direction of arrow X from the bending portion 53b. The stepped bending portion 53p has a portion (fifth bending portion) bent in the plate thickness direction (arrow X direction) of the bending portion 53b and a portion (sixth bending portion) bent and extending in the insertion direction with respect to the rear side plate 52 from that portion. The tip of the stepped bending portion 53p is an inclined portion 53p1 that is inclined in a direction away from the bending portion 53b of the rear side plate 53 with respect to the insertion direction of the rear side plate 53 with respect to the rear side plate 52.

[0056] When the rear side plate 53 is assembled, the stepped bending portions 53m, 53p of the rear side plate 53 engage with the stepped portions 52a1 (fifth portion), 52b1 (sixth portion) of the rear side plate 52. At this time, the inclined portions 53m1, 53p1 of the rear side plate 53 contact the stepped portions 52a1, 52b1 of the rear side plate 52, and the movement of the rear side plate 53 in the direction of arrow Z is guided. As a result, the stepped portion 52a1 of the rear side plate 52 is sandwiched from its plate thickness direction by the stepped bending portion 53m and the support portion 53a in the rear side plate 53, and the stepped portion 52b1 of the rear side plate 52 is sandwiched from its plate thickness direction by the stepped bending portion 53p and the bending portion 53b. In this way, the positions of the rear side plate 53 with respect to the rear side plate 52 in the directions of arrow X and arrow Y are determined.

[0057] Also, when the rear side plate 53 is inserted into the rear side plate 52 until the stopper portion 53r of the rear side plate 53 contacts the upper end portion of the stepped portion 52b1 of the rear side plate 52, the position of the rear side plate 53 and the rear side plate 52 in the direction of arrow Z is determined. In this way, the final relative position between the rear side plate 53 and the rear side plate 52 is determined.

[0058] In addition, bending portions 52j (second bending portion) and 52k (first bending portion) that close at least a part of the notch portion 52r formed in the rear side plate 52 are provided at the stepped portions 52a1, 52b1 of the rear side plate 52. The notch portion 52r is a notch required when performing bending processing for forming the stepped portions 52a1, 52b1 of the rear side plate 52.

[0059] The bent portion 52j is formed by bending substantially perpendicular (89 degrees to 91 degrees) in the arrow X direction from the end portion of the stepped portion 52a1 in the arrow Y direction toward the stepped portion 52b1. The bent portion 52k is formed by bending substantially perpendicular (89 degrees to 91 degrees) in the arrow Y direction from the end portion of the stepped portion 52b1 in the arrow X direction toward the stepped portion 52a1. The tip portion 52k1 of the bent portion 52k is the portion closest to the stepped portion 52b1 in the stepped portion 52a1. In other words, the side surface portion 52j1 of the bent portion 52j is the portion closest to the stepped portion 52a1 in the stepped portion 52b1. The gap V2 between the tip portion 52k1 of the bent portion 52k and the side surface portion 52j1 of the bent portion 52j shown in FIG. 15 is equal to or less than the plate thickness of the support portion 53a of the rear side plate 53. Note that the bent portion 52j and the bent portion 52k may be configured to be in contact with each other without providing the gap V2.

[0060] FIG. 16 is a perspective view sequentially showing the processing methods of the stepped portions 52a1 and 52b1 and the bent portions 52j and 52k. As shown in FIGS. 16(a) and 16(b), when forming the stepped portions 52a1 and 52b1 and the bent portions 52j and 52k, first, the corner portions around the notch portion 52r in the rear side plate 52 are bent substantially perpendicular to the arrow Y direction to form the bent portions 52j and 52k. Next, as shown in FIG. 16(c), the upper portions in the vertical direction of the flat portion 52a and the bent portion 52b are bent in the arrow Y direction to form the stepped portions 52a1 and 52b1. Then, as shown in FIG. 16(d), the end portion of the flat portion 52a in the arrow X direction is bent substantially perpendicular to the arrow Y direction to form the bent portion 52b. In this way, the bent-up portions 51w2 and 51w4 and the bent portions 51j and 51k are bent.

[0061] When the rear side plate 53 is assembled to the rear side plate 52, the bending portions 52j and 52k provided on the rear side plate 52 have the following effects. That is, if the bending portion 52j is not provided, when the rear side plate 53 is inserted into the rear side plate 52, the corner portion 53h of the rear side plate 53 enters the space above the notch portion 52r, and both the bending portion 53b and the stepped bending portion 53p of the rear side plate 53 may be inserted into one side with respect to the stepped portion 52b1 of the rear side plate 52. In this case, the stepped bending portion 53p does not engage, and the stepped portion 52b1 of the rear side plate 52 cannot be sandwiched by the bending portion 53b and the stepped bending portion 53p of the rear side plate 53, so the relative position accuracy between the rear side plate 52 and the rear side plate 53 deteriorates.

[0062] On the other hand, by providing the bending portion 52j on the rear side plate 52, when the rear side plate 53 is about to be inserted into the wrong position with respect to the rear side plate 52 as described above, the lower end portion of the bending portion 53b of the rear side plate 53 interferes with the bending portion 52j of the rear side plate 52. For this reason, the rear side plate 53 cannot be inserted all the way into the rear side plate 52. Therefore, it is possible to suppress the rear side plate 53 from being assembled to the rear side plate 52 at the wrong position, and it is possible to suppress the deterioration of the relative position accuracy between the rear side plate 53 and the rear side plate 52.

[0063] Also, if the bending portion 52k is not provided, when the rear side plate 53 is inserted into the rear side plate 52, the corner portion 53h of the rear side plate 53 enters the space above the notch portion 52r, and both the support portion 53a and the stepped bending portion 53m of the rear side plate 53 may be inserted into one side with respect to the stepped portion 52a1. In this case, the stepped bending portion 53m does not engage, and the stepped portion 52a1 of the rear side plate 52 cannot be sandwiched by the support portion 53a and the stepped bending portion 53m of the rear side plate 53, so the relative position accuracy between the rear side plate 52 and the rear side plate 53 deteriorates.

[0064] On one hand, by providing the bending part 52k on the rear side plate 52, when the rear side plate 53 is about to be inserted into the incorrect position described above with respect to the rear side plate 52, the lower end part of the support part 53a of the rear side plate 53 interferes with the bending part 52k of the rear side plate 52. For this reason, the rear side plate 53 cannot be inserted all the way into the rear side plate 52. Therefore, it is possible to suppress the rear side plate 53 from being assembled to the rear side plate 52 at an incorrect position, and it is possible to suppress the deterioration of the relative position accuracy between the rear side plate 52 and the rear side plate 53.

[0065] That is, in order to ensure the strength of the rear side plate 52 and to align the positions of the flat part 52a of the rear side plate 52 and the support part 53a of the rear side plate 53, and the positions of the bending part 52b of the rear side plate 52 and the bending part 53b of the rear side plate 53, the stepped parts 52a1 and 52b1 are required on the rear side plate 52. In order to bend the stepped parts 52a1 and 52b1, for example, a notch such as the notch part 52r is required. If the notch part 52r is left as it is, as described above, the rear side plate 53 may enter the space above the notch part 52r, and the rear side plate 53 may be assembled at an incorrect position.

[0066] On the contrary, by providing the bending parts 52j and 52k to block at least a part of the notch part 52r, and arranging the part that contacts or is closest to the stepped part 52a1 in the stepped part 52b at a position different from the corner part 53h of the rear side plate 53 when viewed from the vertical direction. With such a configuration, when the rear side plate 53 is about to be assembled at the incorrect position described above, the stepped parts 52a1 and 52b1 interfere with the rear side plate 53 to restrict the assembly, so it is possible to suppress the rear side plate 53 from being assembled at an incorrect position. Therefore, according to the configuration of the present embodiment, it is possible to achieve both the ease of assembly and the improvement of the positioning accuracy of the rear side plate 52 and the rear side plate 53, which are two sheet metals constituting the frame body 31.

[0067] In the present embodiment, a configuration has been described in which at least a part of the notch portion 52r is closed by the two bent portions 52j and 52k of the rear side plate 52 to prevent the rear side plate 53 from being inserted into the wrong position. However, the present invention is not limited to this. That is, as long as the portion that contacts or is closest to the stepped portion 52a1 in the stepped portion 52b1 when viewed from the vertical direction is arranged at a position different from the corner portion 53h of the rear side plate 53, the same effect as described above can be obtained. For example, similar to the bent portion 51j of the rear bottom plate 51 shown in FIG. 12(a), a configuration in which the notch portion 52r is closed by one bent portion 52j, or similar to the bent portion 51k of the rear bottom plate 51 shown in FIG. 12(b), a configuration in which the notch portion 52r is closed by one bent portion 52k may be adopted.

[0068] Next, as shown in FIG. 17, the middle stay 54 is assembled. The middle stay 54 is an optical table on which the laser scanner unit 15 is placed and is an example of a connecting member. The middle stay 54 is placed on two columns 33c provided on the mounting table 33 and is inserted into the support portion 53a of the rear side plate 53. In the present embodiment, the middle stay 54 is used as a member that supports the laser scanner unit 15. However, as long as it is a member that connects the front side plate 55 and the rear side plate 50 so that a predetermined interval is formed between them at a position between the laser scanner unit 15 and the sheet cassette 42 in the vertical direction. Also, as long as it is an exposure unit that exposes the photosensitive drum 6 with an LED instead of the laser scanner unit 15, a configuration provided between the exposure unit and the sheet cassette 42 in the vertical direction is sufficient.

[0069] The middle stay 54 has a flat portion 54w1 extending in the horizontal direction and a bent-up portion 54w2 bent vertically upward from the flat portion 54w1 at one end in the arrow Y direction of the flat portion 54w1. The middle stay 54 also has a bent-up portion 54w3 bent vertically from the flat portion 54w1 so as to face the bent-up portion 54w2, and a bent-up portion 54w4 bent vertically upward from the flat portion 54w1 at one end in the arrow X direction of the flat portion 54w1. The middle stay 54 also has a bent portion 54w5 bent vertically downward from the flat portion 54w1 at the other end in the arrow X direction of the flat portion 54w1 and extending further horizontally therefrom. A protruding portion 54a protruding in the insertion direction (arrow Y direction) with respect to the rear side plate 53 is provided on the bent-up portion 54w4 of the middle stay 54. The protruding portion 54a of the middle stay 54 is formed on the support portion 53a of the rear side plate 53 and is inserted into a through hole 150 penetrating in the plate thickness direction (arrow Y direction) of the support portion 53a. Thereby, the positions of the middle stay 54 with respect to the rear side plate 53 in the arrow X direction and the arrow Y direction are determined.

[0070] Next, as shown in FIG. 18, the front side plate 55 is assembled. The middle stay 54 is inserted into the front side plate 55. The front side plate 55 has a flat portion 55w1 extending in the vertical direction and bent-up portions 55w2 where both ends in the arrow X direction and the arrow Y direction of the flat portion 55w1 are bent forward of the image forming apparatus A, respectively. Through holes 55a and 55b penetrating in the plate thickness direction (arrow Y direction) are formed in the flat portion 55w1 of the front side plate 55. Protruding portions 54b and 54c protruding in the insertion direction (arrow Y direction) with respect to the front side plate 55 are provided on the bent-up portion 54w3 of the middle stay 54. A hook portion 54b1 protruding upward from the base end portion is provided at the tip end portion of the protruding portion 54b.

[0071] The protruding portion 54b of the middle stay 54 is inserted into the through-hole 55a formed in the flat portion 55w1 of the front side plate 55, and the protruding portion 54c is inserted into the through-hole 55b formed in the flat portion 55w1 of the front side plate 55. Thereby, the position of the front side plate 55 with respect to the middle stay 54 is determined. Further, the engaging portion 54b1 of the protruding portion 54b faces the portion above the through-hole 55a in the front side plate 55. Thereby, the engaging portion 54b1 of the middle stay 54 and the flat portion 55w1 of the front side plate 55 come into contact with each other, movement of the middle stay 54 in the direction opposite to the insertion direction with respect to the front side plate 55 is restricted, and the middle stay 54 is prevented from coming off.

[0072] Next, as shown in FIG. 19, the left support column 56 is assembled. The left support column 56 is disposed on the mounting table 33. Further, the front side plate 55 is inserted into the left support column 56. The left support column 56 is mainly formed of two planes, and has a flat portion 56w1 extending in parallel with the flat portion 55w1 of the front side plate 55 and a flat portion 56w2 bent substantially perpendicularly rearward of the image forming apparatus A from the flat portion 56w1. A through-hole 56a penetrating in the direction of arrow Y is provided at the bent portion of the boundary between the flat portion 56w1 and the flat portion 56w2 of the left support column 56. Further, a through-hole 56b penetrating in the plate thickness direction (arrow X direction) is provided in the flat portion 56w2 of the left support column 56. Further, a protruding portion 55c protruding in the insertion direction (arrow Y direction) with respect to the left support column 56 and a protruding portion 55d protruding in the plate thickness direction (arrow X direction) are provided at the bent portion 55w2 of the front side plate 55.

[0073] The protruding portion 55c of the front side plate 55 is inserted into the through-hole 56a formed in the left support column 56. Thereby, the position of the left support column 56 with respect to the front side plate 55 is determined. Further, the protruding portion 55d of the front side plate 55 engages with the through-hole 56b of the left support column 56. Thereby, the edge portion 55d1 of the protruding portion 55d abuts against the inner wall of the through-hole 56b, and movement of the front side plate 55 in the direction opposite to the insertion direction with respect to the left support column 56 is restricted.

[0074] Next, as shown in FIG. 20, the front lower stay 57 is assembled. The front lower stay 57 is placed on the mounting table 33 and inserted into the left support column 56 for assembly. The front lower stay 57 has a flat portion 57w1 which is a plane on which it is placed on the mounting table 33, and bent-up portions 57w2 where both end portions of the flat portion 57w1 in the arrow X direction and the arrow Y direction are bent vertically upward from the flat portion 57w1. A protruding portion 57a protruding in the insertion direction (arrow X direction) with respect to the left support column 56 is provided on the bent-up portion 57w2 of the front lower stay 57. A positioning hole 57b penetrating in the plate thickness direction (arrow Z direction) is formed in the flat portion 57w1 of the front lower stay 57. Further, a through hole 56c penetrating in the plate thickness direction (arrow X direction) is formed in the flat portion 56w2 of the left support column 56. Here, let the width of the upper end portion of the through hole 56c be L1 and the width of the lower end portion be L2. Also, let the width of the tip portion of the protruding portion 57a be L3 and the width of the substrate portion be L4. At this time, the relationships of L1 > L2, L4 < L3, L1 ≒ L3, and L2 ≒ L4 are satisfied.

[0075] The protruding portion 57a of the front lower stay 57 is inserted into and engaged with the through hole 56c formed in the flat portion 56w2 of the left support column 56. At this time, the protruding portion 57a is inserted from the upper side of the through hole 56c and then moved to the lower end portion of the through hole 56c by the force of the assembler or gravity. Here, when the protruding portion 57a is positioned at the lower end portion of the through hole 56c, due to the relationship of L3 > L2, the movement of the protruding portion 57a in the direction opposite to the insertion direction with respect to the through hole 56c is restricted. Also, when the front lower stay 57 is arranged on the mounting table 33, the positioning pin 33b of the mounting table 33 is inserted into the positioning hole 57b of the front lower stay 57. Thereby, the position of the front lower stay 57 with respect to the mounting table 33 is determined.

[0076] Next, as shown in FIG. 21, the right support column 58 is assembled. The right support column 58 is disposed on the mounting table 33. Further, the front side plate 55 is inserted into and assembled to the right support column 58. The right support column 58 has a flat portion 58w1 extending parallel to the flat portion 55w1 of the front side plate 55, and a flat portion 58w2 bent substantially perpendicularly forward of the image forming apparatus A from the flat portion 58w1. The assembly configuration of the right support column 58 and the front side plate 55 is the same as the assembly configuration of the left support column 56 and the front side plate 55. That is, a through hole (not shown) penetrating in the direction of arrow Y is formed in the bent portion at the boundary between the flat portion 58w1 and the flat portion 58w2 of the right support column 58. A protruding portion (not shown) formed in the bent portion 55w2 of the front side plate 55 and protruding in the insertion direction (arrow Y direction) with respect to the right support column 58 is inserted into this through hole. Further, a through hole (not shown) penetrating in the plate thickness direction (arrow X direction) is formed in the flat portion 58w2 of the right support column 58. A protruding portion (not shown) formed in the bent portion 55w2 of the front side plate 55 and protruding in the direction of arrow X engages with this through hole. Here, the left support column 56 and the right support column 58 are assembled after the front side plate 55 is assembled to the middle stay 54, but the front side plate 55 may be assembled to the middle stay 54 and the left support column 56 in such an order that the left support column 56 is placed on the mounting table 33.

[0077] When assembled up to this point, the frame body 31 becomes self - supporting. That is, the front side plate 55, the right support column 58, the left support column 56, and the front lower stay 57, which are the frame body 31 on the front side of the image forming apparatus A, the rear bottom plate 51, the rear side plates 52 and 53, which are the frame body on the rear side, and the middle stay 54, which is the frame body 31 connecting the frame body on the front side and the frame body on the rear side, are assembled, so that the frame body 31 becomes self - supporting.

[0078] Next, as shown in FIG. 22, the lower left stay 59 is assembled. The lower left stay 59 has a flat portion 59w1 extending parallel to the flat portion 56w2 of the left support column 56, and a bent-up portion 59w2 bent in the plate thickness direction (arrow X direction) of the flat portion 59w1 at the upper part of the flat portion 59w1. The lower left stay 59 is assembled by being inserted into the rear side plate 52 and the left support column 56 from the vertical direction with respect to each other. The assembly configuration between the lower left stay 59 and the left support column 56 and the assembly configuration between the lower left stay 59 and the rear side plate 52 are the same. Therefore, only the assembly configuration between the lower left stay 59 and the left support column 56 will be described here.

[0079] On the flat portion 56w2 of the left support column 56, a protruding portion 56g and a stepped bending portion 56j protruding in the insertion direction (arrow Z direction) with respect to the lower left stay 59, and a protruding portion 56h protruding in the plate thickness direction (arrow X direction) of the flat portion 56w2 are provided. The stepped bending portion 56j has a portion bent in the plate thickness direction of the flat portion 56w2 and a portion bent and extending in the insertion direction with respect to the lower left stay 59 from that portion. Further, the tip of the stepped bending portion 56j is an inclined portion 56j1 inclined in a direction away from the flat portion 56w2 with respect to the insertion direction of the left support column 56 with respect to the lower left stay 59. Further, on the flat portion 59w1 of the lower left stay 59, a through hole 59a penetrating in its plate thickness direction (arrow X direction) and a notch portion 59b notched in its plane direction are formed.

[0080] The protruding portion 56g of the left support column 56 is inserted into and engaged with the through hole 59a formed in the flat portion 59w1 of the lower left stay 59. Here, the width of the protruding portion 56g in the arrow Y direction and the width of the through hole 59a in the arrow Y direction are substantially the same. Therefore, the position of the lower left stay 59 in the arrow Y direction with respect to the left support column 56 is determined by inserting the protruding portion 56g into the through hole 59a.

[0081] Also, the stepped bending portion 56j of the left support column 56 is inserted into and engaged with the lower end portion of the flat portion 59w1 of the lower left stay 59. Thereby, the flat portion 59w1 of the lower left stay 59 is sandwiched from its plate thickness direction (arrow X direction) by the stepped bending portion 56j and the flat portion 56w2 in the left support column 56, and the position of the lower left stay 59 in the arrow X direction with respect to the left support column 56 is determined.

[0082] Further, the protrusion 56h of the left support column 56 engages with the notch 59b formed in the lower left stay 59. As a result, the edge 56h1 of the protrusion 56h abuts against the inner wall of the notch 59b, restricting the movement of the left support column 56 in the direction opposite to the insertion direction with respect to the lower left stay 59.

[0083] Next, as shown in FIG. 23, the upper left stay 60 is assembled. The lower left stay 59 is assembled by being inserted into each other from the vertical direction with respect to the rear side plate 53 and the left support column 56. The assembly configuration between the upper left stay 60 and the rear side plate 53 and the assembly configuration between the upper left stay 60 and the left support column 56 are the same. Therefore, only the assembly configuration between the upper left stay 60 and the left support column 56 will be described here.

[0084] On the flat portion 56w2 of the left support column 56, a protrusion 56d and a stepped bent portion 56e that protrude in the insertion direction (arrow Z direction) with respect to the upper left stay 60 are formed. The stepped bent portion 56e has a portion bent in the plate thickness direction (arrow X direction) of the flat portion 56w2 of the left support column 56 and a portion bent and extending in the insertion direction with respect to the upper left stay 60 from that portion. Further, the tip of the stepped bent portion 56e is an inclined portion 56e1 that inclines in a direction away from the flat portion 56w2 with respect to the insertion direction of the left support column 56 with respect to the upper left stay 60.

[0085] The upper left stay 60 has a flat portion 60w1 that extends parallel to the flat portion 56w2 of the left support column 56 and a bent-up portion 60w2 that is bent in the plate thickness direction (arrow X direction) of the flat portion 60w1 at the upper part of the flat portion 60w1. Through holes 60a and 60b that penetrate in the plate thickness direction (arrow X direction) are formed in the flat portion 60w1 of the upper left stay 60.

[0086] The protruding portion 56d of the left support column 56 is inserted into and engaged with a through hole 60a formed in the flat portion 60w1 of the upper left stay 60. Here, the width of the protruding portion 56d in the arrow Y direction is substantially the same as the width of the through hole 60a in the arrow Y direction. Therefore, when the protruding portion 56d is inserted into the through hole 60a, the position of the upper left stay 60 with respect to the left support column 56 in the arrow Y direction is determined. Further, the stepped bending portion 56e of the left support column 56 is inserted into and engaged with the through hole 60b of the upper left stay 60. Thereby, the flat portion 60w1 of the upper left stay 60 is sandwiched in the plate thickness direction (arrow X direction) by the stepped bending portion 56e and the flat portion 56w2 of the left support column 56, and the position of the upper left stay 60 with respect to the left support column 56 in the arrow X direction is determined.

[0087] Next, as shown in FIG. 24, the lower right stay 61 is assembled. The lower right stay 61 is a member that connects the rear side plate 52 and the right support column 58 facing each other, and is inserted and assembled from the front side where the right support column 58 is located in the horizontal direction (arrow Y direction) with respect to the rear side plate 52 and the right support column 58. The lower right stay 61 is connected to the right support column 58 and the rear side plate 52 so that the interval between the right support column 58 and the rear side plate 52 becomes a predetermined interval, and is a member that guarantees the transportability of the seat S. Further, since it is located near the lower right corner portion of the frame body 31, it affects the rigidity of the frame body 31. Therefore, it is particularly desirable that the lower right stay 61 be assembled with high positional accuracy. Hereinafter, the assembly configuration of the lower right stay 61 will be described in detail.

[0088] Figure 25 is a perspective view of the lower right stay 61, the rear side plate 52, and the right support column 58. Here, Fig. 25(a) shows the state before the lower right stay 61 is assembled, and Fig. 25(b) shows the state after the lower right stay 61 is assembled. First, the assembly structure of the lower right stay 61 and the rear side plate 52 will be described. As shown in Fig. 25, a bent portion 250 bent toward the front side in the direction of arrow Y is provided on the flat portion 52a of the rear side plate 52. The bent portion 250 is bent in the thickness direction of the flat portion 52a of the rear side plate 52 and is bent in the direction opposite to the bent portion 52w with respect to the flat portion 52a. Further, in the flat portion 52a of the rear side plate 52, through holes 251 penetrating in the thickness direction (arrow Y direction) of the flat portion 52a are formed around the bent portion 250. As described above, the rear side plate 52 is formed from a single sheet of sheet metal, and the through holes 251 are holes formed during the processing of the bent portion 250.

[0089] The lower right stay 61 is composed of three planes and has a U-shaped cross section. The lower right stay 61 has a flat portion 61w1 extending substantially parallel to the bent portion 52w of the rear side plate 52, and a flat portion 61w2 bent substantially perpendicular to the flat portion 61w1 in the direction of arrow X at the upper part of the flat portion 61w1. The lower right stay 61 also has a flat portion 61w3 bent so as to face the flat portion 61w2 at the lower part of the flat portion 61w1. A stepped bent portion 61a that is inserted into and engaged with the bent portion 250 of the rear side plate 52 is provided on the flat portion 61w1 of the lower right stay 61. The stepped bent portion 61a has a portion bent in the thickness direction (arrow X direction) of the flat portion 61w1 of the lower right stay 61 and a portion extending by being bent in the insertion direction (arrow Y direction) with respect to the rear side plate 52 from that portion. The stepped bent portion 61a forms through holes around the stepped bent portion 61a when being processed with respect to the flat portion 61w2, and the stepped bent portion 61a is formed by being bent with respect to the flat portion 61w2.

[0090] When the lower right stay 61 is assembled, the entire one end portion of the lower right stay 61 in the arrow Y direction is inserted into the through hole 251 of the rear side plate 52, and the stepped bent portion 61a of the lower right stay 61 is inserted into and engaged with the bent portion 250 of the rear side plate 52. Thereby, the bent portion 250 of the rear side plate 52 is sandwiched in the plate thickness direction (arrow X direction) by the stepped bent portion 61a and the flat portion 61w1 in the lower right stay 61, and the position of the lower right stay 61 in the arrow X direction (the plate thickness direction of the flat portion 61w1) with respect to the rear side plate 52 is determined.

[0091] Also, the flat portion 61w2 which is the upper surface of the lower right stay 61 and the inner wall above the through hole 251 of the rear side plate 52 face each other with a predetermined interval therebetween, and the flat portion 61w3 which is the lower surface of the lower right stay 61 contacts the inner wall below the through hole 251 due to the self-weight of the lower right stay 61. Thereby, the position of the lower right stay 61 in the vertical direction (arrow Z direction) with respect to the rear side plate 52 is determined in a state with play corresponding to a predetermined interval.

[0092] Next, the assembly structure of the lower right stay 61 and the right support column 58 will be described. As shown in FIG. 25, a insertion hole 58a into which the stepped bent portion 61b of the lower right stay 61 is inserted is formed in the flat portion 58w2 of the right support column 58. Further, the right support column 58 has a flat portion (not shown) extending in the arrow Y direction from the periphery of the insertion hole 58a in the flat portion 58w2 to the rear of the image forming apparatus A. A substantially semi-circular protrusion (not shown) protruding in the plate thickness direction (arrow X direction) is provided on this flat portion (not shown). The protrusion (not shown) is formed by drawing and is disposed at a position adjacent to the insertion hole 58a in the insertion direction (arrow Y direction) of the stepped bent portion 61b with respect to the insertion hole 58a.

[0093] Also, a stepped bent portion 61b which is inserted into and engaged with the insertion hole 58a of the right support column 58 is provided on the flat portion 61w1 of the lower right stay 61. The stepped bent portion 61b has a portion bent in the plate thickness direction (arrow X direction) of the flat portion 61w1 and a portion bent and extending from that portion in the insertion direction (arrow Y direction) with respect to the right support column 58.

[0094] In addition, around the bent step portion 61b in the flat portion 61w1 of the lower right stay 61, a through hole 61c penetrating in the thickness direction of the flat portion 61w1 is formed. The through hole 61c is disposed at a position adjacent to the bent step portion 61b in the insertion direction of the lower right stay 61 with respect to the right support column 58. As described above, the lower right stay 61 is formed from a single sheet metal, and the through hole 61c is a hole formed during the processing of the bent step portion 61b.

[0095] When the lower right stay 61 is assembled, the bent step portion 61b of the lower right stay 61 is inserted into and engaged with the insertion hole 58a of the right support column 58, and a protruding portion (not shown) of the right support column 58 is engaged with the through hole 61c of the lower right stay 61. By engaging the bent step portion 61b with the insertion hole 58a in this way, the positions of the lower right stay 61 with respect to the right support column 58 in the directions of arrow X, arrow Y, and arrow Z are determined. Also, the upper surface of the bent step portion 61b and the upper inner wall of the insertion hole 58a face each other with a predetermined gap therebetween, and the lower surface of the bent step portion 61b and the lower inner wall of the insertion hole 58a face each other with a predetermined gap therebetween. Thereby, the position of the lower right stay 61 in the direction from the rear side to the front side in the direction of arrow Y with respect to the right support column 58 is determined. With such a configuration, the positions of the lower right stay 61 with respect to the right support column 58 in the directions of arrow X, arrow Y, and the vertical direction (arrow Z direction) are determined in a state having play by a predetermined interval.

[0096] Also, in a state where the lower right stay 61 is engaged with the rear side plate 52 and the right support column 58, the movement of the lower right stay 61 in the direction opposite to the insertion direction with respect to the rear side plate 52 and the right support column 58 is restricted by the contact of a protruding portion (not shown) of the right support column 58 with the inner wall of the through hole 61c. The insertion direction of the lower right stay 61 with respect to the rear side plate 52 and the right support column 58 is a direction perpendicular to the plane of the flat portion 52a of the rear side plate 52, and is the direction from the front side to the rear side in the direction of arrow Y. The direction opposite to the insertion direction of the lower right stay 61 with respect to the rear side plate 52 and the right support column 58 is a direction perpendicular to the plane of the flat portion 52a of the rear side plate 52, and is the direction from the rear side to the front side in the direction of arrow Y.

[0097] Next, as shown in FIG. 26, the rear side plate 62 is assembled. The rear side plate 62 is inserted and assembled into the rear side plate 53 from the direction of arrow Z. The assembly configuration of the rear side plate 62 and the rear side plate 53 is the same as the assembly configuration of the rear side plate 52 and the rear side plate 53, and they are assembled in a configuration where they are inserted into each other and engaged with each other.

[0098] Next, as shown in FIG. 27, the right middle stay 65 is assembled. The right middle stay 65 is a plate-like member formed in one plane, and is a member that supports a fan for cooling an end portion in the rotational axis direction of the fixing portion 45. The right middle stay 65 is inserted and assembled into the rear side plate 53 and the right support column 58. The assembly configuration of the right middle stay 65 and the rear side plate 53 is the same as the assembly configuration of the right middle stay 65 and the right support column 58. Therefore, here, the assembly configuration of the right middle stay 65 and the rear side plate 53 will be mainly described.

[0099] A through hole 53c penetrating in the plate thickness direction (arrow Y direction) is formed in the support portion 53a of the rear side plate 53. Note that the rear side plate 53 is a member extending in the vertical direction. Further, the right middle stay 65 is provided with a protruding portion 65a that protrudes in the insertion direction (arrow Y direction) with respect to the support portion 53a of the rear side plate 53 and is inserted into the through hole 53c of the rear side plate 53 from the direction of arrow Y.

[0100] The protruding portion 65a has a base portion 65a1 that fits into the through hole 53c, and a hooking portion 65a2 that is provided on the tip side in the insertion direction from the base portion 65a1 and whose lower end portion 65a2x is located below the lower end portion 65a1x of the base portion 65a1 in the vertical direction. Further, it has an inclined portion 65a3 that inclines so that the height decreases from the upper end portion of the base portion 65a1 to the upper end portion of the hooking portion 65a2.

[0101] When the protrusion 65a is inserted into the through-hole 53c, first, the engaging portion 65a2, which is the tip of the protrusion 65a, is inserted, and then the base portion 65a1 is inserted, and the base portion 65a1 fits into the through-hole 53c. The vertical width of the base portion 65a1 of the protrusion 65a and the vertical width of the through-hole 53c are substantially the same. Also, the plate thickness of the right middle stay 65 and the width of the through-hole 53c in the direction of arrow X are substantially the same. Therefore, when the base portion 65a1 of the protrusion 65a fits into the through-hole 53c, the position in the vertical direction (arrow Z direction) of the right middle stay 65 with respect to the rear side plate 53, the insertion direction with respect to the rear side plate, and the position in the direction orthogonal to the vertical direction (arrow X direction) are determined.

[0102] Also, in a state where the base portion 65a1 of the protrusion 65a is fitted into the through-hole 53c, the lower end portion 65a2x of the engaging portion 65a2 is located at a position facing a portion below the through-hole 53c in the support portion 53a of the rear side plate 53. In the present embodiment, the lower end portion 65a2x of the engaging portion 65a2 protrudes 2 mm downward with respect to the lower end portion 65a1x of the base portion 65a1 and is provided with a 3 mm gap with respect to the opposing portion of the right middle stay facing the support portion 53a of the rear side plate 53. Here, the plate thickness of the support portion 53a of the rear side plate 53 is about 1 mm, and the length of the base portion 65a1 of the protrusion 65a in the direction of arrow Y is longer than the plate thickness of the support portion 53a of the rear side plate 53. Thereby, even if the rear side plate 53 and the right middle stay 65 are relatively inclined during assembly, the engaging portion 65a2 is caught by the support portion 53a, and movement in the direction opposite to the insertion direction of the right middle stay 65 with respect to the support portion 53a of the rear side plate 53 is restricted. Therefore, separation of the right middle stay 65 from the rear side plate 53 is suppressed, and the right middle stay 65 and the rear side plate 53 can be assembled with high positional accuracy. Also, as described above, since the assembly configuration between the right middle stay 65 and the rear side plate 53 is the same as the assembly configuration between the right middle stay 65 and the right support column 58, separation of the right middle stay 65 from the right support column 58 is suppressed, and the positional accuracy of the right middle stay 65 and the right support column 58 can be improved.

[0103] Next, as shown in FIG. 28, the right support column 63 is assembled. The right support column 63 has a flat portion 63w1 extending parallel to the flat portion 55w1 of the front side plate 55, a flat portion 63w2 bent substantially perpendicularly from the flat portion 63w1 in the direction of arrow Y, and a flat portion 63w3 bent substantially perpendicularly from the flat portion 63w2 so as to face the flat portion 63w1. The right support column 63 is assembled by being inserted into each other with the right support column 58.

[0104] FIG. 29 is an enlarged perspective view of the engaging portion between the right support column 63 and the right support column 58. Here, FIG. 29(a) shows the state before the right support column 63 and the right support column 58 are assembled, and FIG. 29(b) shows the state where the right support column 63 and the right support column 58 are assembled.

[0105] As shown in FIG. 29, on the flat portion 63w2 of the right support column 63, a protrusion 63a protruding in the thickness direction (arrow X direction) of the flat portion 63w2 and two protrusions 63b protruding in the insertion direction (arrow Z direction) with respect to the right support column 58 are provided. Here, the protrusion 63b is provided below the protrusion 63a in the vertical direction (arrow Z direction). The protrusion 63a is formed by drawing, and the amount of protrusion from the surface of the flat portion 63w2 is about 0.3 mm to 2 mm. The tip of the protrusion 63b is an inclined portion 63b1 that inclines in a direction away from the flat portion 63w2 with respect to the insertion direction of the right support column 63 of the right support column 63.

[0106] On the flat portion 58w2 of the right support column 58, a stepped bent portion 58c protruding in the insertion direction (arrow Z direction) of the right support column 58 with respect to the right support column 63 is provided. Also, at a position adjacent to the stepped bent portion 58c in the insertion direction of the right support column 58 with respect to the right support column 63, a through hole 58d penetrating in the thickness direction (arrow X direction) of the flat portion 58w2 is formed. The stepped bent portion 58c has a portion bent in the thickness direction of the flat portion 58w2 and a portion bent and extending in the insertion direction with respect to the right support column 63 from that portion. The tip of the stepped bent portion 58c is an inclined portion 58c1 that inclines in a direction away from the flat portion 58w2 with respect to the insertion direction of the right support column 58 with respect to the right support column 63.

[0107] When the right support column 63 is assembled to the right support column 58, the inclined portion 58c1 of the stepped bent portion 58c of the right support column 58 abuts against the flat portion 63w2 of the right support column 63, and the inclined portion 63b1 of the protruding portion 63b of the right support column 63 abuts against the flat portion 58w2 of the right support column 58. Thereby, the movement of the right support column 63 and the right support column 58 in the arrow Z direction is guided, and the flat portion 63w2 and the flat portion 58w2 move in a predetermined positional relationship. Further, the lower end portion of the stopper portion 63c of the right support column 63 abuts against the abutting portion 58e which is the upper end portion of the flat portion 58w2 of the right support column 58, thereby restricting the movement of the right support column 63 in the insertion direction (arrow Z direction) with respect to the right support column 58.

[0108] When the right support column 63 is assembled to the right support column 58, the stepped bent portion 58c of the right support column 58 is inserted into the flat portion 63w2 of the right support column 63 and engaged with the lower end portion of the flat portion 63w2. Thereby, the flat portion 63w2 of the right support column 63 is sandwiched from the plate thickness direction (arrow X direction) by the stepped bent portion 58c and the flat portion 58w2 in the right support column 58, and the position of the right support column 63 with respect to the right support column 58 in the arrow X direction is determined.

[0109] Further, the protruding portion 63a of the right support column 63 is engaged with the through hole 58d formed in the right support column 58. Thereby, the edge portion 63a1 of the protruding portion 63a abuts against the inner wall of the through hole 58d, and the movement of the right support column 63 in the direction opposite to the insertion direction with respect to the right support column 58 is restricted. Here, the through hole 58d is disposed at a position adjacent to the stepped bent portion 58c in the insertion direction of the right support column 58 with respect to the right support column 63. Therefore, the protruding portion 63a engaged with the through hole 58d and the stepped bent portion 58c are disposed at positions adjacent to each other in the above insertion direction.

[0110] In the present embodiment, the edge portion 63a1 of the protruding portion 63a abuts against the inner wall of the through hole 58d formed during the processing of the stepped bent portion 58c. However, a configuration in which the edge portion 63a1 of the protruding portion 63a abuts against the inner wall of another through hole different from the through hole 58d may be employed. Thereby, the movement of the right support column 63 in the direction opposite to the insertion direction with respect to the right support column 58 is restricted.

[0111] Also, in a direction (arrow Y direction) orthogonal to the thickness direction of the flat portion 63w2 of the right support column 63 and the insertion direction with respect to the right support column 58, two protruding portions 63b of the right support column 63 engage with the stepped bending portion 58c of the right support column 58 so as to sandwich the stepped bending portion 58c. Thereby, the position of the right support column 63 in the orthogonal direction with respect to the right support column 58 is determined.

[0112] In the vicinity of the stepped bending portion 58c that engages the flat portion 63w2 of the right support column 63 and the flat portion 58w2 of the right support column 58 in this way, a protruding portion 63a is provided to restrict movement of the right support column 63 in a direction opposite to the insertion direction with respect to the right support column 58. Thereby, it is possible to suppress the right support column 63 from moving in a direction opposite to the insertion direction with respect to the right support column 58 and the right support column 63 and the right support column 58 from separating and the positional accuracy from deteriorating. Therefore, the right support column 63 and the right support column 58 constituting the frame body 31 can be assembled with high positional accuracy.

[0113] Next, as shown in FIG. 30, the upper right stay 64 is assembled. The upper right stay 64 has a flat portion 64w1 extending in the horizontal direction, a flat portion 64w2 in which one end portion in the arrow X direction on the flat portion 64w1 is bent substantially perpendicular to the vertical direction, and a flat portion 64w3 in which one end portion in the arrow Y direction is bent substantially perpendicular to the vertical direction. The upper right stay 64 also has a flat portion (not shown) in which the other end portion in the arrow Y direction on the flat portion 64w1 is bent substantially perpendicular to the vertical direction. The upper right stay 64 is assembled by being inserted into the rear side plate 62 and the right support column 63. The assembly configuration between the upper right stay 64 and the rear side plate 62 and the assembly configuration between the upper right stay 64 and the right support column 63 are the same. Therefore, only the assembly configuration between the upper right stay 64 and the right support column 63 will be described here.

[0114] The flat portion 64w3 of the upper right stay 64 is composed of three bent portions 304a, 304b, and 304c that are bent in the insertion direction (arrow Z direction) with respect to the right support column 63 from the flat portion 64w1. That is, when the flat portion 64w3 is divided into three parts in the arrow X direction, there are bent portions 304a, 304b, and 304c. The bent portion 304c is disposed at a position between the bent portion 304a and the bent portion 304b in the arrow X direction, and the length of the bent portion 304c in the arrow Z direction is shorter than the lengths of the bent portions 304a and 304b in the arrow Z direction. Also, the lengths of the bent portions 304a and 304b in the arrow Z direction are the same, and the tip portions of the bent portions 304a and 304b are inclined portions 304a1 and 304b1 that are inclined in a direction away from the flat portion 64w1 with respect to the insertion direction with respect to the right support column 63.

[0115] On the flat portion 63w3 of the right support column 63, there is provided a stepped bent portion 316 that protrudes in the insertion direction (vertical direction, arrow Z direction) with respect to the upper right stay 64 and is inserted into and engaged with the upper right stay 64 so as to overlap with the bent portion 304c of the upper right stay 64 in the plate thickness direction (arrow Y direction) of the flat portion 63w3. Also, on the flat portion 63w2 of the right support column 63, there is provided a stepped bent portion 325 that protrudes in the insertion direction with respect to the upper right stay 64 and is inserted into and engaged with the flat portion 64w2 so as to overlap with the flat portion 64w2 of the upper right stay 64 in the plate thickness direction (arrow X direction) of the flat portion 63w2. Further, on the flat portion 63w2 of the right support column 63, there is provided a protrusion 330 that protrudes in its plate thickness direction (arrow X direction).

[0116] The stepped bent portion 316 has a portion bent in the plate thickness direction (arrow Y direction) of the flat portion 63w3 of the right support column 63 and a portion that is bent and extends in the insertion direction (arrow Z direction) with respect to the upper right stay 64 from that portion. Also, the tip portion of the stepped bent portion 316 is further bent from the portion bent in the insertion direction with respect to the upper right stay 64 in the stepped bent portion 316 and is an inclined portion 316a that is inclined in a direction away from the flat portion 63w3 with respect to the insertion direction with respect to the upper right stay 64.

[0117] The stepped bending portion 325 has a portion bent in the thickness direction (arrow X direction) of the flat portion 63w2 of the right support column 63, and a portion bent and extending in the insertion direction (arrow Z direction) with respect to the upper right stay 64 from that portion. Further, the tip of the stepped bending portion 325 is formed by further bending from the portion bent in the insertion direction with respect to the upper right stay 64 in the stepped bending portion 325, and becomes an inclined portion 325a that inclines in a direction away from the flat portion 63w2 with respect to the insertion direction with respect to the upper right stay 64.

[0118] When the upper right stay 64 is assembled to the right support column 63, the inclined portions 316a, 325a of the stepped bending portions 316, 325 of the right support column 63 abut against the upper right stay 64, and the inclined portions 304a1, 304b1 of the bending portions 304a, 304b of the upper right stay 64 abut against the right support column 63. Thereby, the movement of the upper right stay 64 and the right support column 63 is guided, and both move in a predetermined positional relationship.

[0119] When the stepped bending portion 316 engages with the bending portion 304c of the upper right stay 64 and the bending portions 304a, 304b engage with the flat portion 63w3 of the right support column 63, in the direction (arrow X direction) orthogonal to the insertion direction and the thickness direction of the right support column 63 and the upper right stay 64, the stepped bending portion 316 and the bending portions 304a, 304b engage alternately. Specifically, the bending portion 304a engages with the flat portion 63w3 of the right support column 63 at a position adjacent to the stepped bending portion 316 in the arrow X direction. Further, the bending portion 304b engages with the flat portion 63w3 of the right support column 63 at a position adjacent to the stepped bending portion 316 on the side opposite to the side where the bending portion 304a is disposed with respect to the stepped bending portion 316 in the arrow X direction. With such a configuration, the upper right stay 64 and the right support column 63 are firmly engaged and assembled.

[0120] Further, the protrusion 330 of the right support column 63 engages with a through hole 335 formed in the flat portion 64w2 of the upper right stay 64 and penetrating in the thickness direction (arrow X direction) of the flat portion 64w2. Thereby, the edge portion 330a of the protrusion 330 abuts against the inner wall of the through hole 335, and the movement of the upper right stay 64 in the direction opposite to the insertion direction with respect to the right support column 63 is restricted.

[0121] As described above, each sheet metal that constitutes the frame body 31 is assembled. As described above, the frame body 31 assembled in the assembly process is configured to be self - supporting. Therefore, by gripping the rear side plate 52, the left support column 56, the right support column 58, etc. of the frame body 31 and lifting the frame body 31, it can be removed from the mounting table 33.

[0122] <Frame body joining process> Next, a process of joining the frame body 31 assembled in the above - described assembly process will be described.

[0123] FIG. 31 is a perspective view of a jig 34 used for joining the frame body 31. As shown in FIG. 29, the jig 34 has a base 34a, a front support portion 34b, and a rear support portion 34c. A positioning pin 34a1 is provided on the base 34a. Also, the front support portion 34b and the rear support portion 34c are configured to be slidable with respect to the base 34a. The front support portion 34b is slidable in the directions of arrows K1 and K2, and the rear support portion 34c is slidable in the directions of arrows K3 and K4.

[0124] FIG. 32 is a perspective view of the frame body 31 and the jig 34 assembled in the above - described assembly process. As shown in FIG. 30, after the assembly process, the frame body 31 is removed from the mounting table 33 and placed on the base 34a of the jig 34. At this time, by inserting the positioning pin 34a1 of the base 34a into the positioning hole 51a of the rear bottom plate 51 and the positioning hole 57b of the front lower stay 57 of the frame body 31, the position of the frame body 31 with respect to the base 34a is determined.

[0125] As shown in FIG. 33, when joining the frame body 31, the front support portion 34b is slid in the direction of arrow K1 and the rear support portion 34c is slid in the direction of arrow K3 by an operator performing the joining process. Also, the frame body 31 is pressed from a direction orthogonal to the sliding direction and the vertical direction of the front support portion 34b and the rear support portion 34c by a pressing device (not shown). As a result, the sheet metals that constitute the frame body 31 are pressed against each other, eliminating unnecessary gaps between the sheet metals and completing the alignment.

[0126] After that, each sheet metal constituting the frame body 31 is joined by a fiber laser welding by an operator. When the joining of the frame body 31 is completed, the front support portion 34b is slid in the direction of arrow K2 and the rear support portion 34c is slid in the direction of arrow K4 by the operator, and the frame body 31 is removed from the jig 34. Thus, the frame body 31 is completed.

Explanation of Signs

[0127] 3…Process Cartridge (Image Forming Unit) 31…Frame Body (Metal Frame) 51…Rear Bottom Plate (Second Sheet Metal) 51w1…Flat Portion (Third Portion) 51w2…Bending Portion (Fourth Portion) 51w4…Bending Portion (Fifth Portion) 52…Rear Side Plate (First Sheet Metal, Second Sheet Metal) 52a…Flat Portion (First Portion, Third Portion) 52a1…Step Portion (Fifth Portion) 52b…Bending Portion (Second Portion, Fourth Portion) 52b1…Step Portion (Sixth Portion) 52h…Corner Portion 52m…Step Bending Portion (First Engaging Portion) 52p…Step Bending Portion (Second Engaging Portion) 53…Rear Side Plate (First Sheet Metal) 53a…Support Portion (First Portion) 53b…Bending Portion (Second Portion) 53h…Corner Portion 53m…Step Bending Portion (First Engaging Portion) 53p…Step Bending Portion (Second Engaging Portion) A…Image Forming Apparatus

Claims

1. An image forming unit, a first sheet metal, and a second sheet metal connected under the first sheet metal, and a metal frame that supports the image forming unit, wherein the first sheet metal, includes a first portion that extends along a vertical direction and includes a surface that extends along a first horizontal direction intersecting the vertical direction, a second portion that extends along the vertical direction and includes a surface that extends along a second horizontal direction intersecting the vertical direction and the first horizontal direction, and has a first corner formed between the first portion and the second portion, wherein the second sheet metal, includes a third portion that includes a surface substantially parallel to the surface included in the first portion and is assembled to the first portion, a fourth portion that includes a surface substantially parallel to the surface included in the second portion and is assembled to the second portion, in the first horizontal direction, from an edge of the third portion close to the fourth portion, in a direction intersecting the surface included in the first portion, a fifth portion bent from the first corner in a direction in which the second portion extends from the first portion, and has a second corner formed between the third portion and the fifth portion, wherein in the first horizontal direction, the first corner and the second corner are arranged at different positions, An image forming apparatus characterized by the above.

2. The second sheet metal further, in the second horizontal direction, includes a sixth portion bent from an edge of the fourth portion close to the third portion in a direction intersecting the surface included in the second portion, and has a third corner formed between the fourth portion and the sixth portion, wherein in the second horizontal direction, the first corner and the third corner are arranged at different positions, The image forming apparatus according to claim 1, characterized by the above.

3. The second sheet metal further has a bottom surface portion including a surface extending along the first horizontal direction and the second horizontal direction, wherein the third portion and the fourth portion are formed by being bent vertically upward from an edge of the bottom surface portion, The image forming apparatus according to claim 1 or 2, characterized by the above.

4. The second sheet metal, further includes a first side wall portion that extends along the vertical direction and includes a surface that extends along the first horizontal direction, and a second side wall portion that extends along the vertical direction and includes a surface that extends along the second horizontal direction, wherein the third portion of the second sheet metal is continuous from the first side wall portion through a first bending upward in a direction intersecting the vertical direction and a second bending upward in the vertical direction from the first side wall portion, The fourth part of the second sheet metal is continuous from the second side wall part through a third bending that extends in a direction intersecting the vertical direction and a fourth bending that extends in the vertical direction. The image forming apparatus according to claim 1 or 2, characterized in that.

5. An image forming unit, A metal frame including a first sheet metal and a second sheet metal connected below the first sheet metal, and supporting the image forming unit. The first sheet metal, A first part including a surface that extends along the vertical direction and extends along a first horizontal direction intersecting the vertical direction, A second part including a surface that extends along the vertical direction and extends along a second horizontal direction intersecting the vertical direction and the first horizontal direction, And a first corner formed between the first part and the second part. The second sheet metal, A third part including a surface substantially parallel to the surface included in the first part and assembled to the first part, A fourth part including a surface substantially parallel to the surface included in the second part and assembled to the second part, In the first horizontal direction, a fifth part bent in a direction intersecting the surface included in the first part from the edge of the third part close to the fourth part, And a second corner formed between the third part and the fifth part. In the first horizontal direction, the first corner and the second corner are arranged at different positions. The second sheet metal further, In the second horizontal direction, a sixth part bent in a direction intersecting the surface included in the second part from the edge of the fourth part close to the third part, And a third corner formed between the fourth part and the sixth part. In the second horizontal direction, the first corner and the third corner are arranged at different positions. An image forming apparatus, characterized in that.

6. The second sheet metal further has a bottom surface part including a surface extending along the first horizontal direction and the second horizontal direction, The third part and the fourth part are formed by being bent upward in the vertical direction from the edge of the bottom surface part. The image forming apparatus according to claim 5, characterized in that.

7. The second sheet metal, A first side wall part including a surface that extends along the vertical direction and extends along the first horizontal direction, And a second side wall part including a surface that extends along the vertical direction and extends along the second horizontal direction. The third portion of the second sheet metal is continuous from the first side wall portion through a first bending that extends in a direction intersecting the vertical direction from the first side wall portion and a second bending that extends in the vertical direction. The fourth portion of the second sheet metal is continuous from the second side wall portion through a third bending that extends in a direction intersecting the vertical direction from the second side wall portion and a fourth bending that extends in the vertical direction. The image forming apparatus according to claim 5, characterized in that.

Images