JP2002031856A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device which can assure the position accuracy of an exposure section when an upper unit is closed. SOLUTION: A main scanning exposure unit 30 is movably mounted at the upper unit 14. When the upper unit 14 is closed, a roll 96 disposed on the main scanning exposure unit 30 abuts the outer peripheral surface of a platen roll 26 and the positions of the main scanning direction and sub-scanning direction and exposure focal length with respect to the platen roll 26 are determined. A magnet 98 attracts a stopper 100 by magnetic force to fix the main scanning exposure unit 30, thereby exhibiting a vibration proof function.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for thermally transferring an image exposed on a photosensitive material to paper.

[0002]

2. Description of the Related Art In a thermal transfer type image forming apparatus for thermally transferring an image exposed on a photosensitive material to paper, the photosensitive material is wound around a platen roll in an exposure section, and is intermittently fed in a sub-scanning direction. Some devices expose an image in the main scanning direction. After water is applied to the photosensitive material to which the image has been exposed, it is superposed on paper and wound around a developing drum, and the image is thermally transferred from the photosensitive material to paper.

In such an image forming apparatus, the applicant of the present invention has constituted the image forming apparatus by an upper unit and a lower unit, and a boundary (open surface) between the upper unit and the lower unit as a conveying path of the photosensitive material. Has proposed an invention that facilitates the jamming process.

However, when the opening and closing operations of the upper unit and the lower unit are repeated, occurrence of backlash or the like at the hinge portion is expected (there is a limit in positioning on the side plate frame). How to position the main scanning direction and sub-scanning direction of the exposure unit on the unit side and the focal length at the time of exposure, and how to position the developing drum (upper unit side) in the lower unit are problems. Have been.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of guaranteeing the positional accuracy of an exposure unit and a developing drum when an upper unit is closed in consideration of the above fact.

[0006]

According to the first aspect of the present invention, the upper unit and the lower unit are separated from each other by a transport path of the photosensitive material sent from the photosensitive material supply unit to the developing unit through the exposure unit. Can be opened and closed. Accordingly, the jam of the photosensitive material can be accessed not from the width direction of the photosensitive material but from the surface direction of the photosensitive material. For this reason, jam processing can be easily performed without generating wrinkles in the photosensitive material.

The exposure section includes a sub-scanning exposure unit (lower unit side) for feeding the photosensitive material in the sub-scanning direction, and a main scanning exposure unit for exposing the photosensitive material on the sub-scanning exposure unit in the main scanning direction. The main scanning exposure unit is movably attached to the upper unit by floating means.

When the upper unit is closed,
Since the positioning means positions the main scanning exposure unit with respect to the sub-scanning exposure unit, the positional relationship between the sub-scanning exposure unit and the main-scanning exposure unit is maintained even if play occurs at the hinges of the upper unit and the lower unit. It is.

Further, the main scanning exposure unit need only be mounted on the upper unit so as to be movable (floating), so that it can be assembled roughly.

According to the second aspect of the present invention, the positioning means is provided in the main scanning exposure unit and contacts the platen roll constituting the sub-scanning exposure unit so that the positioning means can be moved in the main scanning direction.
The roll includes a roll that determines the position in the sub-scanning direction and the exposure focal length, and a magnet that is provided between the upper unit and the lower unit and that keeps the roll in contact with the platen roll.

When the upper unit is closed, the roll comes into contact with the outer peripheral surface of the platen roll, and the position in the main scanning direction, the sub scanning direction, and the exposure focal length are determined. In addition, the main scanning exposure unit and the sub-scanning exposure unit are fixed by the magnetic force of the magnet, and exhibit an anti-vibration function.

According to the third aspect of the present invention, the positioning means is provided between the bearing and the shaft, the bracket being provided in the main scanning exposure unit and abutting against the outer peripheral surface of the bearing of the platen roll constituting the sub-scanning exposure unit. It comprises a spring member for pressing the bracket against the side surface of the bearing, and a stopper provided on the side of the sub-scanning exposure unit for restricting the rotation of the bracket when the main-scanning exposure unit comes into contact therewith.

In this configuration, when the upper unit is closed,
The bracket abuts on the outer peripheral surface of the bearing to determine the position of the main scanning dew unit in the sub-scanning direction with respect to the platen roll, and the exposure focal length.

Further, the bracket is pressed against the side surface of the bearing by the spring member, and the position in the main scanning direction is determined.
Further, since the stopper provided on the sub-scanning exposure unit contacts the main-scanning exposure unit to restrict the rotation of the bracket, the stopper does not shift due to vibration or the like. It is preferable that a spring be provided on the back surface of the main scanning exposure unit and the bracket be pressed against the bearing together with the main scanning exposure unit.

According to the fourth aspect of the present invention, the floating means is constituted by a swinging means for supporting the main scanning exposure unit so as to be swingable in two axial directions. That is, the main scanning exposure unit can move in the vertical direction and the sub-scanning direction.

On the other hand, a positioning means is provided in the main scanning exposure unit, and a substantially L-shaped bracket abutting from two axial directions on an outer peripheral surface of a bearing of a platen roll constituting the sub-scanning exposure unit; A biasing means is disposed between the upper units and biases the main scanning exposure unit in two axial directions, and a pressing spring which presses a side surface of the bracket to position the main scanning exposure unit in the main scanning direction. ing.

In this configuration, when the upper unit is closed,
A substantially L-shaped bracket comes into contact with the outer peripheral surface of the bearing from two axial directions, and the position of the main scanning dew unit in the sub scanning direction with respect to the platen roll and the exposure focal length are determined. At this time, since the urging means urges the main scanning dew unit in two axial directions, no backlash is generated between the bracket and the bearing, and high-precision positioning, position reproducibility, and vibration isolation are achieved. it can.

Further, since the bracket is pressed against the outer peripheral surface of the bearing, there is no fear of abrasion or vibration as compared with the case where the bracket is pressed directly against the platen roller. Further, the position of the main scanning dew unit in the main scanning direction is accurately determined by the pressing spring that presses the side surface of the bracket.

According to the fifth aspect of the present invention, the floating means is provided in the mounting opening formed on the upper unit side and in the main scanning exposure unit, and the latch claw is swingably suspended from the mounting opening with one touch. And is composed of

In this configuration, the main scanning exposure unit can be attached to the upper unit with one touch by suspending the latch claw from the attachment opening. For this reason, the main scanning exposure unit can be easily attached and detached, and maintenance can be facilitated.

According to the invention described in claim 6, the developing section includes the developing drum movably attached to the upper unit. Then, when the upper unit and the lower unit are closed, positioning means provided on the lower unit positions the developing drum with respect to the lower unit.

In the invention according to claim 7, the positioning means is constituted by a fitting portion for determining the position in the sub-scanning direction and the main scanning direction by fitting the shaft portion of the developing drum.

In this configuration, when the upper unit is closed,
The shaft portion of the developing drum is fitted with the fitting portion, and the positions in the sub-scanning direction and the main scanning direction are determined. For this reason, even if play occurs at the hinge portions of the upper unit and the lower unit, the positional accuracy of the developing drum is ensured.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS.
The image forming apparatus 10 according to the embodiment includes a lower unit 12,
The lower unit 12 is composed of an upper unit 14 that can be opened upward around a hinge 13.

The lower unit 12 and the upper unit 14
Can be divided on the basis of the transport path of the photosensitive material 18. Thereby, the jam processing of the photosensitive material 18 is performed.
Since access is possible not from the width direction of the photosensitive material 18 but from the surface direction of the photosensitive material 18, jam processing can be easily performed without wrinkling of the photosensitive material 18.

Further, by employing such an opening mechanism, the image forming apparatus 1 of the present embodiment in which the photosensitive material 18 to which the image has been transferred is wound on a waste reel 40 without being cut.
0 jam processing can be performed. The upper unit 14
The lower unit 12 is locked by the latch lever 38 latching an engaging portion (not shown). On the other hand, in the lower unit 12, a photosensitive material magazine 20 is detachably mounted. The upper cover 16 of the light-sensitive material magazine 20 can be opened, and the light-sensitive material 1 stored inside in the closed state is closed.
8 is shaded. The photosensitive material 18 is supplied to the supply reel 1.
The photosensitive material 18 is unwound together with the nip roller 21 by rotating the supply reel 17 by driving means (not shown).

Further, a feed roller 23 is attached to the lower unit 12. When the upper unit 14 is closed, the feed roller 23 nips the photosensitive material 18 with a nip roller 22 mounted on the upper unit 14 side, and sends out the photosensitive material 18 to a platen roll 26 constituting an exposure unit.

The photosensitive material 18 sent to the platen roll 26 is wound around the platen roll 26 and nipped by a nip roller 28. Thus, the photosensitive material 1
By exposing 8 around the platen roll 26 and exposing,
No wrinkles or the like occur in the width direction of the photosensitive material 18, and the flatness of the exposed surface can be ensured. Next, each time the scanning head (not shown) of the main scanning exposure unit 30 arranged in the upper unit 14 moves in the main scanning direction and scans the photosensitive material 18, the platen roll 26 is driven intermittently to 18 is stepped in the sub-scanning direction.

The photosensitive material 18 on which the image has been exposed is conveyed onto a support table 34, and is coated with water by a water absorbing coating member 36 provided in a coating tank 38.

The photosensitive material 18 which has been coated with water is supplied to a developing drum 42 as a developing section in which a halogen lamp is incorporated.
Is wound around by tension rollers 44 and 46 at a constant pressure. The wound photosensitive material 18 is superimposed on the paper P from above while being heated, and the image is transferred.

Next, the photosensitive material 18 to which the image has been transferred is taken up on a waste reel 40. Thus, the photosensitive material 1
8 is not cut, and the supply reel 17 is discarded from the supply reel 17.
The photosensitive material 12 itself functions as a belt that applies a constant pressure to the paper P.

On the other hand, a paper P wound around a supply reel 50 is set in a receiving magazine 48 arranged in the upper unit 14. The paper P is pulled out by a nip roller 52 and cut by a paper cutter 54 into a predetermined length.
8 and is wound around the developing drum 42 while being superposed on the photosensitive material 18.

The paper P on which the image has been transferred from the photosensitive material 18 is peeled off from the developing drum 42 by a peeling claw (not shown), guided by the transport roller 60 and the guide plate, and reaches the tray 62.

Next, a positioning mechanism in the exposure section of the image forming apparatus according to the first embodiment will be described with reference to FIGS.

Main scanning exposure unit 30 constituting an exposure section
Is provided with a box-shaped housing 66 whose bottom is open. An exposure scanning unit 68 is housed in the housing 66. Support shafts 70 project from both sides of the exposure scanning unit 68. The support shaft 70 is slidably supported by a vertically long hole 72 formed in a side wall of the housing 66 and is prevented from falling off by a ring 71. With this configuration, the exposure scanning unit 68 is movable with respect to the upper unit 14.

One end of a coil spring 76 is fixed to the ceiling wall of the housing 66. This coil spring 76
Is attached to the ceiling wall of the exposure scanning section 68, and urges the exposure scanning section 68 downward. Thereby, when the exposure scanning unit 68 is in the free state, the support shaft 70
2 at the end.

Further, on both sides of the bottom surface of the exposure scanning section 68,
An L-shaped bracket 78 is attached. When the upper unit 14 is closed, the bracket 78 includes a base portion 78A that comes into contact with the outer peripheral surface of a bearing 82 attached to the rotating shaft 80 of the platen roll 26,
And a leg 78B corresponding to the second side surface 82A.

On the other hand, the rotating shaft 80 of the platen roll 26
Is rotatably supported by a bearing 84 attached to the side wall 12A of the lower unit 12, and is fixed by a retaining ring 86.

Between the bearing 84 and the bearing 82, an insertion spring 90 having a circular hole 88 formed at the center and through which the rotating shaft 80 passes is disposed. Both ends of the insertion spring 90 are bent in a direction facing each other.
The leg 78B of the bracket 78 enters between the A and the side surface of the bearing 82, and the leg 78
B is pressed against the side surface of the bearing 82.

A receiving plate 92 projects outward from the side wall 12A. The receiving unit 92 includes the upper unit 14
Is closed, a slide shaft 94 for guiding the scanning head of the main scanning exposure unit 30 in the main scanning direction comes into contact with the slide shaft 94 for positioning in the sub-scanning direction.
The bracket 78 is restricted so as not to rotate around two.

Next, the operation of the positioning mechanism will be described.

When the upper unit 14 is closed, the base 78A of the bracket 78 comes into contact with the outer peripheral surface of the bearing 82, and the position of the exposure scanning unit 68 in the sub scanning direction with respect to the platen roll 26 and the exposure focal length are determined. At this time, a slide shaft 94 that guides the scanning head in the main scanning direction comes into contact with the receiving plate 92, thereby positioning the scanning head in the sub-scanning direction and restricting the bracket 78 from rotating around the bearing 82. In this state, the coil spring 76 presses the exposure scanning unit 68 toward the platen roll 26, so that there is no backlash in the contact portion.

On the other hand, the leg 78B of the bracket 78 enters between the bent piece 90A of the insertion spring 90 and the bearing 82, and is pressed against the side surface of the bearing 82 by the urging force of the insertion spring 90. Thus, the position of the exposure scanning unit 68 in the main scanning direction is determined. Therefore, the upper unit 1
No matter how many times the unit 4 and the lower unit 12 are opened and closed, optical positional accuracy is always maintained.

Next, a positioning mechanism in an exposure section of the image forming apparatus 11 according to the second embodiment will be described with reference to FIGS.

In the second embodiment, the exposure scanning section 68 is movably attached to the housing 66 and includes a coil spring 76.
The first embodiment is the same as the first embodiment except that a hard roll 96 is used as the positioning means.

A pair of the rolls 96 are arranged on both sides of the bottom surface of the exposure scanning section 68 at a predetermined distance in the sub-scanning direction. When the roll 96 contacts the outer peripheral surface of the platen roll 26 at two places, the position (exposure point) in the sub-scanning direction and the exposure focal length are determined. Also, by contacting at two places so as to straddle the platen roll 26, the first
It is not necessary to separately provide a member for regulating the rotation of the exposure scanning unit 68 like the bracket of the embodiment. Further, the end surface 96A of the roll 96 contacts the inner surface of the side wall 12A of the lower unit 12, and determines the position of the exposure scanning unit 68 in the main scanning direction.

In the lower unit 12, a magnet 98 is provided. Then, when the upper unit 14 is closed, the magnet 98 attracts the stopper 100 projecting outside the exposure scanning unit 68. Thereby, the positional accuracy of the exposure scanning unit 68 and the platen roll 26 in the main scanning direction and the sub-scanning direction is ensured.

Next, a positioning mechanism in the exposure section of the image forming apparatus 17 according to the third embodiment will be described with reference to FIGS.

The third embodiment is substantially the same as the first embodiment in the basic structure, except that a latch claw 120 is provided above the exposure scanning section 68, and this latch claw 120 is
6 in that it is hung by a mounting opening 122 formed in the side wall of No. 6 and can swing in two axial directions (H direction and V direction).

The latch claw 120 has a claw portion 120B that projects obliquely outward from the upper end of the base portion 120A.
When the exposure scanning unit 68 is housed in the housing 66, the exposure scanning unit 68 is pushed by the inner wall of the housing 66 and elastically deforms.
Is reached and elastically restored, and is suspended from the mounting port 122 in a state of protruding outside the mounting port 122.

The width B of the claw portion 120B is
22 and the thickness T of the claw portion 120B is set to be smaller than the height h of the mounting port 122, so that the exposure scanning section 68 can swing in two axial directions as described above. ing.

One end of a coil spring 76 is fixed to the ceiling wall of the housing 66. This coil spring 76
When the exposure scanning unit 68 is housed in the housing 66, the other end of the exposure scanning unit 68 hits the ceiling wall of the exposure scanning unit 68,
Is biased downward (V direction). Further, the housing 66
A leaf spring 124 bent in a V-shape is attached to the side wall. The bent portion of the plate spring 124 is
8, the exposure scanning section 68 is urged in the sub-scanning direction (H direction).

On the other hand, a substantially L-shaped bracket 128 is mounted on the bottom surface of the exposure scanning section 68. When the upper unit 14 is closed, the bracket 128 abuts on the outer peripheral surface of the bearing 82 from two axial directions. A pressing spring 126 is provided between the bearing 84 and the bearing 82.
Is arranged. Bracket 1 is attached to this pressing spring 126.
The side surface of the exposure scanning unit 68 is pressed against the frame and the other bracket 128 (the right bracket in FIG. 9) is pressed against the frame to position the exposure scanning unit 68 in the main scanning direction.

Next, the operation of the positioning mechanism will be described.

In the third embodiment, the claw portion 12 of the latch claw 120
0B into the mounting opening 122, the exposure scanning unit 68
Is swingably suspended from the housing 66 with one touch. For this reason, the attachment and detachment of the exposure scanning unit 68 is facilitated, and maintenance is also facilitated.

When the upper unit 14 is closed, the bracket 128 comes into contact with the outer peripheral surface of the bearing 82 from the biaxial directions of the H direction and the V direction, and the position of the exposure scanning unit 68 with respect to the platen roll 26 in the sub scanning direction, and The exposure focal length is determined. In this state, the coil spring 76 and the leaf spring 124 press the exposure scanning unit 68 toward the platen roll 26, so that there is no backlash at the abutting portion of the bracket 128, and high-precision positioning, position reproducibility, and prevention are achieved. Vibration can be achieved.

Further, the side surface of the bracket 128 contacts the pressing spring 126, and the position of the exposure scanning section 68 in the main scanning direction is determined. Therefore, no matter how many times the upper unit 14 and the lower unit 12 are opened and closed, optical positional accuracy is always maintained.

Next, a positioning mechanism in the developing section of the image forming apparatus 15 according to the fourth embodiment will be described with reference to FIGS.

The bearing 64 attached to the end of the rotating shaft 102 of the developing drum 42 constituting the developing section is supported by a long hole 106 formed in the shaft plate 104, and is supported in the front-rear direction (the upper unit is closed). When viewed in the sub-scanning direction). Also, the rotating shaft 102
, A retaining ring 108 is attached so as not to get out of the elongated hole 106.

On the other hand, a U-shaped stopper 110 is arranged on the side plate 12A of the lower unit 12 in a front view. The inner width of the fitting portion 110A of the stopper 110 is
An invitation surface 110B that is substantially equal to the outer diameter of the rotating shaft 102 and that widens the opening at the entrance of the fitting portion 110A is formed so that the rotating shaft 102 can easily enter the fitting portion 110A.

With such a configuration, the upper unit 14
Is closed, the rotating shaft 102 of the developing drum 42 fits with the stopper 110, and the positions of the developing drum in the sub-scanning direction and the main scanning direction are determined on the inner side surface and the bottom surface of the fitting portion 110A, so that the positional accuracy is improved. Secured.

[0062]

According to the present invention, when the upper unit is closed, the positional accuracy of the exposure unit and the developing drum can be guaranteed.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a state in which an upper unit of an image forming apparatus according to a first embodiment is opened.

FIG. 2 is a side view illustrating a state where an upper unit of the image forming apparatus according to the first embodiment is closed.

FIG. 3 is a perspective view of an exposure unit of the image forming apparatus according to the first embodiment.

FIG. 4 is an exploded perspective view of an exposure unit of the image forming apparatus according to the first embodiment.

FIG. 5 is a sectional view of an exposure unit of the image forming apparatus according to the first embodiment.

FIG. 6 is a side view illustrating a state in which an upper unit of the image forming apparatus according to the second embodiment is opened.

FIG. 7 is a side view illustrating a state where an upper unit of the image forming apparatus according to the second embodiment is closed.

FIG. 8 is a perspective view of an exposure unit of the image forming apparatus according to the second embodiment.

FIG. 9 is a perspective view of an image forming apparatus according to a third embodiment before a main scanning exposure unit is assembled.

FIG. 10 is a perspective view illustrating a relationship between a main scanning exposure unit and a flatten roll of an image forming apparatus according to a third embodiment.

FIG. 11 is a perspective view illustrating a relationship between a main scanning exposure unit and a flatten roll of an image forming apparatus according to a third embodiment.

FIG. 12 is a side view illustrating a relationship between a main scanning exposure unit and a flatten roll of an image forming apparatus according to a third embodiment.

FIG. 13 is a side view illustrating a relationship between a main scanning exposure unit and a flatten roll of the image forming apparatus according to the third embodiment.

FIG. 14 is a front view illustrating a relationship between a main scanning exposure unit and a flatten roll of the image forming apparatus according to a third embodiment.

FIG. 15 is a side view illustrating a state where an upper unit of the image forming apparatus according to the fourth embodiment is opened.

FIG. 16 is a side view illustrating a state where an upper unit of the image forming apparatus according to the fourth embodiment is closed.

FIG. 17 is a perspective view of a developing unit of an image forming apparatus according to a fourth embodiment.

FIG. 18 is a perspective view of a developing unit of an image forming apparatus according to a fourth embodiment.

[Explanation of symbols]

 Reference Signs List 12 Lower unit 14 Upper unit 26 Platen roll (sub-scanning exposure unit) 30 Main scanning exposure unit 42 Developing drum 70 Support shaft (floating means) 72 Slot (floating means) 76 Coil spring (biasing means) 78 Bracket (positioning means) 82 bearing (bearing) 90 leaf spring (spring member, positioning means) 92 receiving plate (stopper, positioning means) 94 slide shaft (positioning means) 96 roll (positioning means) 98 magnet (positioning means) 100 stopper 102 rotating shaft (positioning) Means) 110A Fitting part (positioning means) 120 Latch claw (floating means, swinging means) 122 Mounting port (floating means, swinging means) 124 Leaf spring (biasing means) 126 Pressing spring 128 Bracket Door

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Maeda 1900, Ifuna-cho, Suzuka-shi, Mie Suzuka Fuji Xerox Co., Ltd. (72) Inventor Akihiko Kobayashi 1900, Ifuna-cho, Suzuka-shi, Mie Suzuka Fuji Xerox F term (reference) 2H071 AA02 BA16 DA02 DA08 EA06 2H076 AB60 2H106 BH00 2H112 AA03 AA05 BA23 BA24 BC10

Claims (7)

[Claims] 1. An image forming apparatus wherein an upper unit can be opened and closed with respect to a lower unit by a transport path of a photosensitive material sent from a photosensitive material supply unit to a developing unit via an exposure unit. A sub-scanning exposure unit provided in the lower unit for feeding the photosensitive material in the sub-scanning direction; a main scanning exposure unit for exposing the photosensitive material on the sub-scanning exposure unit in the main scanning direction; Floating means for movably attaching the unit to the upper unit; and positioning means for positioning the main scanning exposure unit relative to the sub-scanning exposure unit when the upper unit is closed. Image forming apparatus. 2. The positioning device according to claim 1, wherein the positioning unit is provided in the main scanning exposure unit, and determines a position in a main scanning direction, a sub scanning direction, and an exposure focal length by contacting a platen roll constituting the sub scanning exposure unit. 2. The image forming apparatus according to claim 1, further comprising: a roll; and a magnet provided between the upper unit and the lower unit, the magnet maintaining the roll in contact with the platen roll. 3. apparatus. 3. A bracket provided in said main scanning exposure unit, said positioning means being in contact with an outer peripheral surface of a bearing of a platen roll constituting said sub-scanning exposure unit, and a spring pressing said bracket against a side surface of said bearing. 2. The image forming apparatus according to claim 1, further comprising a member, and a stopper provided on the side of the sub-scanning exposure unit and in contact with the main-scanning exposure unit to restrict rotation of the bracket. 3. 4. The floating means comprises swing means for swingably supporting the main scanning exposure unit in two axial directions, wherein the positioning means is provided in the main scanning exposure unit, and A substantially L-shaped bracket that abuts the outer peripheral surface of a bearing of a platen roll constituting an exposure unit from the two axial directions, and is disposed between the main scanning exposure unit and the upper unit; 2. A biasing means for biasing in an axial direction, and a pressing spring for pressing a side surface of the bracket to position the main scanning exposure unit in the main scanning direction.
An image forming apparatus according to claim 1. 5. The mounting device according to claim 1, wherein the floating unit includes a mounting port formed on the upper unit side, and a latch claw provided on the main scanning exposure unit and suspended by the mounting port in a one-touch manner. The image forming apparatus according to claim 4, wherein the image forming apparatus is configured. 6. An image forming apparatus in which an upper unit can be opened and closed with respect to a lower unit by a transport path of a photosensitive material sent from a photosensitive material supply unit to a development processing unit via an exposure unit. The processing unit includes a developing drum movably attached to the upper unit, and a positioning unit for positioning the developing drum with respect to the lower unit when the upper unit is closed is provided on the lower unit side. An image forming apparatus comprising: 7. The positioning means is provided on the lower unit side, and is constituted by a fitting part which fits with a shaft part of the developing drum to determine a position in a sub-scanning direction and a main scanning direction. The image forming apparatus according to claim 6.