By opening the rear cover 75, the duplex conveyance path 16 (refer to FIG. 2) is exposed. That is, the rear cover 75 is movable between a closed position in which the duplex conveyance path 16 is covered and an opened position in which the duplex conveyance path 16 is exposed to the exterior. Thereby, sheet jamming that has occurred in the duplex conveyance path 16 can be solved. Further, by having a transfer unit not shown opened in a state where the duplex conveyance path 16 is positioned at the opened position, a conveyance path 19 (refer to FIG. 2) through which passes the sheet conveyed by the conveyance roller pair 5c is opened.

Positioning Configuration of Process Unit

Next, a positioning configuration of the process unit 20 will be described with reference to FIGS. 4 to 8. FIG. 4 is a perspective view illustrating the image forming apparatus 1 in a state prior to attaching the process unit 20. FIG. 5A is a rear view and an enlarged view of the positioning configuration of the process unit 20 by a left side panel frame 73, and FIG. 5B is a rear view and an enlarged view of the positioning configuration of the process unit 20 by a right side panel frame 74.

As illustrated in FIG. 4, the process unit 20 includes a left side face 30L and a right side face 30R serving as end portions in a longitudinal direction LD that is parallel to the X direction. The left side face 30L includes a left positioning boss 21L serving as a first positioned portion and a left rotation regulating boss 22L serving as a second positioned portion, whereas the right side face 30R includes a right positioning boss 21R and a right rotation regulating boss 22R (refer to FIG. 7B). The left positioning boss 21L and the right positioning boss 21R are respectively arranged upstream of the left rotation regulating boss 22L and the right rotation regulating boss 22R in the attaching direction AD of the process unit 20. In other words, the left rotation regulating boss 22L and the right rotation regulating boss 22R are respectively arranged downstream of the left positioning boss 21L and the right positioning boss 21R in the attaching direction AD.

The apparatus body 2 of the image forming apparatus 1 includes the left side panel frame 73 and the right side panel frame 74 formed of a sheet metal member, wherein the left side panel frame 73 and the right side panel frame 74 oppose one another with a clearance therebetween in the longitudinal direction LD serving as a second direction. Noted that the left side panel frame 73 is provided on a side of the left side face 30L of the process unit 20 in the longitudinal direction LD.

As illustrated in FIGS. 4 and 5A, the left side panel frame 73 serving as a frame member includes a first left surface 81Lf and a second left surface 82Lf that extend in a direction along the attaching direction AD, i.e., Y direction, and the Z direction. The second left surface 82Lf is arranged inward of the apparatus body 2 for distance X1 from the first left surface 81Lf in the longitudinal direction LD by draw-processing the first left surface 81Lf serving as a first surface. In other words, the second left surface 82Lf is arranged closer to a center portion of the process unit 20 in the longitudinal direction LD than the first left surface 81Lf. That is, the first left surface 81Lf and the second left surface 82Lf are not coplanar. In the present embodiment, the second left surface 82Lf serving as a second surface is composed of a surface parallel to the attaching direction AD, i.e., Y direction, and the Z direction, but the present technique is not limited thereto. For example, the second left surface 82Lf can be a curved surface along the attaching direction AD, i.e., Y direction, and the Z direction.

A left positioning portion 81L with which the left positioning boss 21L can engage is formed on the first left surface 81Lf, wherein the left positioning portion 81L serving as a first positioning portion is a cutout having an upstream side in the attaching direction AD opened. In other words, the left positioning portion 81L is a first opening. Or the left positioning portion 81L is a part of a slit extending from an upstream edge of the left side panel frame 73 in the attaching direction AD. A left rotation regulating portion 82L with which the left rotation regulating boss 22L can engage is formed on the second left surface 82Lf, wherein the left rotation regulating portion 82L serving as a second positioning portion is a U-shaped cutout having an upstream side in the attaching direction AD opened. In other words, the left rotation regulating portion 82L is a second opening provided on the second left surface 82Lf of the left side panel frame 73. Since the second left surface 82Lf is formed by draw-processing, an inclined surface for guiding the left positioning boss 21L toward the left positioning portion 81L can be formed.

Since the first left surface 81Lf and the second left surface 82Lf are positioned apart from each other by distance X1 in the longitudinal direction LD, the left rotation regulating portion 82L is also arranged apart by distance X1 from the left positioning portion 81L in the longitudinal direction LD. In other words, the left rotation regulating portion 82L is arranged at a position that differs from the left positioning portion 81L in the longitudinal direction LD. That is, the left rotation regulating portion 82L is arranged closer to a center portion of the process unit 20 in the longitudinal direction LD than the left positioning portion 81L.

Similarly, as illustrated in FIGS. 4 and 5B, the right side panel frame 74 includes a first right surface 81Rf and a second right surface 82Rf that extend along the attaching direction AD, i.e., Y direction, and the Z direction. The second right surface 82Rf is arranged inward of the apparatus body 2 for distance X2 from the first right surface 81Rf in the longitudinal direction LD by draw-processing the first right surface 81Rf. That is, the first right surface 81Rf and the second right surface 82Rf are not coplanar. In the present embodiment, the first right surface 81Rf and the second right surface 82Rf are composed of a surface parallel to the attaching direction AD, i.e., Y direction, and the Z direction, but the present technique is not limited thereto. For example, the second right surface 82Rf can be a curved surface along the attaching direction AD, i.e., Y direction, and the Z direction.

A right positioning portion 81R with which the right positioning boss 21R can engage is formed on the first right surface 81Rf, wherein the right positioning portion 81R is a cutout having an upstream side in the attaching direction AD opened. A right rotation regulating portion 82R with which the right rotation regulating boss 22R can engage is formed on the second right surface 82Rf, wherein the right rotation regulating portion 82R is a U-shaped cutout having an upstream side in the attaching direction AD opened. Since the second right surface 82Rf is formed by draw-processing, an inclined surface for guiding the right positioning boss 21R toward the right positioning portion 81R can be formed.

Since the first right surface 81Rf and the second right surface 82Rf are positioned apart from each other by distance X2 in the longitudinal direction LD, the right rotation regulating portion 82R is also arranged apart by distance X2 from the right positioning portion 81R in the longitudinal direction LD. In other words, the right rotation regulating portion 82R is arranged at a position that differs from the right positioning portion 81R in the longitudinal direction LD.

FIG. 6A is a schematic view illustrating the image forming apparatus 1 in a state where the process unit 20 is attached, and FIG. 6B is an enlarged view illustrating the left positioning portion 81L and the left rotation regulating portion 82L. As illustrated in FIGS. 5A to 6B, in a state where the process unit 20 is attached to the apparatus body 2, the process unit 20 is urged from a rear side toward a front side by an urging mechanism not shown. In a state where the process unit 20 is attached to the apparatus body 2, the left positioning boss 21L and the left rotation regulating boss 22L of the process unit 20 are respectively engaged with the left positioning portion 81L and the left rotation regulating portion 82L of the left side panel frame 73. Similarly, in a state where the process unit 20 is attached to the apparatus body 2, the right positioning boss 21R and the right rotation regulating boss 22R of the process unit 20 are respectively engaged with the right positioning portion 81R and the right rotation regulating portion 82R of the right side panel frame 74.

By having the left positioning boss 21L and the right positioning boss 21R respectively engage with the left positioning portion 81L and the right positioning portion 81R, the process unit 20 is positioned with respect to the left side panel frame 73 and the right side panel frame 74 in the attaching direction AD. Further, by having the left rotation regulating boss 22L and the right rotation regulating boss 22R respectively engage with the left rotation regulating portion 82L and the right rotation regulating portion 82R, rotational movement of the process unit 20 about the left positioning boss 21L and the right positioning boss 21R is regulated. That is, the process unit 20 is positioned with respect to the left side panel frame 73 and the right side panel frame 74 in the Z direction serving as the first direction. A rotational axis which is a center of the left positioning boss 21L and the right positioning boss 21R extends in the longitudinal direction LD and overlaps with the left rotation regulating portion 82L and the right rotation regulating portion 82R when viewed in the longitudinal direction LD.

In further detail, as illustrated in FIG. 6B, the left positioning portion 81L includes projecting portions 51, 52, and 53 against which the left positioning boss 21L abuts. In a state where the process unit 20 is attached to the apparatus body 2, the left positioning boss 21L abuts against the projecting portions 51 and 52 in the attaching direction AD and is positioned thereby. In this state, the left positioning boss 21L abuts against the projecting portions 51, 52, and 53 in the Z direction, such that it is positioned in the Z direction. That is, the left positioning portion 81L positions the process unit 20 together with the left rotation regulating portion 82L in the Z direction.

Further, in a state where the process unit 20 is attached to the apparatus body 2, that is, in a state where the left positioning boss 21L is abutted against the projecting portions 51, 52, and 53, the left rotation regulating boss 22L has a gap G formed between the left rotation regulating portion 82L in the attaching direction AD. In other words, the left rotation regulating portion 82L is configured so as not to position the process unit 20 in the attaching direction AD in a state where the process unit 20 is positioned in the attaching direction AD by the left positioning portion 81L. Thereby, the process unit 20 can be positioned in the attaching direction AD reliably by the left positioning portion 81L, and the positioning accuracy of the process unit 20 can be improved.

The right positioning portion 81R and the right rotation regulating portion 82R adopt similar configurations as the left positioning portion 81L and the left rotation regulating portion 82L, such that descriptions thereof are omitted.

FIG. 6C is an enlarged view illustrating a left positioning portion 281L and a left rotation regulating portion 282L according to a modified example of the first embodiment. According to the present embodiment illustrated in FIG. 6B, the left positioning portion 81L is arranged upstream of the left rotation regulating portion 82L in the attaching direction AD, but the present technique is not limited thereto. For example, as illustrated in FIG. 6C, the left positioning portion 281L serving as a first positioning portion can be arranged downstream of the left rotation regulating portion 282L serving as a second positioning portion in the attaching direction AD.

The left positioning portion 281L has faces 251, 252, and 253, wherein the faces 251 and 253 oppose one another in the Z direction. In a state where the process unit 20 is attached to the apparatus body 2, a left positioning boss 221L serving as a first positioned portion abuts against the face 252 of the left positioning portion 281L and is positioned in the attaching direction AD. Further, at this time, the left positioning boss 221L also abuts against the faces 251 and 253 in the Z direction, by which it is also positioned in the Z direction.

The left rotation regulating portion 282L includes projecting portions 261 and 262. A left rotation regulating boss 222L serving as a second positioned portion is positioned in the Z direction by abutting against the projecting portions 261 and 262 in a state where the process unit 20 is positioned in the attaching direction AD by the left positioning portion 81L. Further, in this state, the left rotation regulating boss 222L has a gap G2 formed between the left rotation regulating portion 282L in the attaching direction AD. In other words, the left rotation regulating portion 282L is configured so as not to position the process unit 20 in the attaching direction AD in a state where the process unit 20 is positioned in the attaching direction AD by the left positioning portion 281L. Thereby, the process unit 20 can be positioned in the attaching direction AD reliably by the left positioning portion 281L, and the positioning accuracy of the process unit 20 can be improved.

FIG. 7A is a cross-sectional view taken in parallel to the XY plane of a positioning configuration of the process unit 20 by the left side panel frame 73, and FIG. 7B is a cross-sectional view taken in parallel to the XY plane of the positioning configuration of the process unit 20 by the right side panel frame 74.

As illustrated in FIG. 7A, the second left surface 82Lf on which the left rotation regulating portion 82L is formed is arranged on an inner side of the apparatus body 2 in the longitudinal direction LD with respect to the first left surface 81Lf on which the left positioning portion 81L is formed. Further, the left rotation regulating boss 22L is also arranged on the inner side of the apparatus body 2 in the longitudinal direction LD with respect to the left positioning boss 21L. Thereby, a shape of a cutout constituting the left rotation regulating portion 82L formed on the second left surface 82Lf can be formed in a relatively small area. Since the left positioning portion 81L is arranged upstream of the left rotation regulating portion 82L in the attaching direction AD, the shape of the cutout constituting the left positioning portion 81L formed on the first left surface 81Lf can also be formed in a relatively small area. As described, by reducing the area of the cutouts formed on the left side panel frame 73, the stiffness of the left side panel frame 73 can be ensured.

Similarly, as illustrated in FIG. 7B, the second right surface 82Rf on which the right rotation regulating portion 82R is formed is arranged on the inner side of the apparatus body 2 in the longitudinal direction LD with respect to the first right surface 81Rf on which the right positioning portion 81R is formed. Further, the right rotation regulating boss 22R is also arranged on the inner side of the apparatus body 2 in the longitudinal direction LD with respect to the right positioning boss 21R. Thereby, the shape of the cutout constituting the right rotation regulating portion 82R formed on the second right surface 82Rf can be formed in a relatively small area. Further, since the right positioning portion 81R is arranged upstream of the right rotation regulating portion 82R in the attaching direction AD, the shape of the cutout constituting the right positioning portion 81R formed on the first right surface 81Rf can also be formed in a relatively small area. As described, by reducing the area of the cutouts formed on the right side panel frame 74, the stiffness of the right side panel frame 74 can be ensured.

By maintaining the stiffness of the left side panel frame 73 and the right side panel frame 74, the positioning accuracy of the process unit 20 with respect to the apparatus body 2 can be improved. Further, since it is not necessary to increase the thickness of the left side panel frame 73 and the right side panel frame 74 to enhance the stiffness of the left side panel frame 73 and the right side panel frame 74, the weight and the cost of the apparatus can be cut down.

FIG. 8 is a left side view illustrating a positioning configuration of the process unit 20 by the left side panel frame 73. The left positioning portion 81L has, as illustrated in FIG. 8, sides 81La and 81Lc that oppose one another in the Z direction, and a side 81Lb that connects the sides 81La and 81Lc and that opposes the left positioning boss 21L in the attaching direction AD. Further, the left rotation regulating portion 82L has sides 82La and 82Lb that oppose one another in the Z direction.

The width of the left positioning portion 81L in the Z direction, that is, the distance between the sides 81La and 81Lc, is a width Z1. The width of the left rotation regulating portion 82L in the Z direction, that is, the distance between the sides 82La 82Lb, is a width Z2. Then, the left rotation regulating portion 82L is arranged such that at least a portion thereof overlaps with the left positioning portion 81L in the Z direction. In other words, at least a portion of the left rotation regulating portion 82L aligns with the left positioning portion 81L in the attaching direction AD when viewed in the longitudinal direction LD. Thereby, a movement locus of the left positioning boss 21L and the left rotation regulating boss 22L in the Z direction when attaching the process unit 20 to the apparatus body 2 overlap, and an area avoiding the movement locus within the apparatus body 2 can be suppressed. Thereby, the space within the apparatus body 2 can be utilized effectively, and the image forming apparatus 1 can be downsized.

Further, since the left positioning portion 81L and the left rotation regulating portion 82L are both provided on the single left side panel frame 73 composed of a sheet metal member, the positioning accuracy of the process unit 20 can be enhanced while suppressing crossing of components.

A similar configuration as that described above with reference to FIG. 8 is adopted in the right side panel frame 74, and a similar effect is exerted. According further to the present embodiment, axial centers of the left positioning boss 21L and the left rotation regulating boss 22L are at a same position in the Z direction, but the present technique is not limited thereto.

Second Embodiment

Next, a second embodiment of the preset technique will be described, wherein according to the second embodiment, a configuration of the second left surface 82Lf and the second right surface 82Rf of the first embodiment has been changed. Therefore, configurations similar to the first embodiment are either not shown or denoted with the same reference numbers in the drawing.

FIG. 9 is a schematic view illustrating an image forming apparatus 1B according to a second embodiment in a state prior to attaching a process unit 20B serving as a detachable unit. FIG. 10A is a rear view and an enlarged view illustrating a positioning configuration of the process unit 20B by a left side panel frame 73B, and FIG. 10B is a rear view and an enlarged view illustrating a positioning configuration of the process unit 20B according to a right side panel frame 74B.

As illustrated in FIG. 9, the process unit 20B includes the left side face 30L and the right side face 30R serving as end faces in the longitudinal direction LD, and faces 31L and 31R that face the downstream side in the attaching direction AD. The face 31L includes a left rotation regulating boss