JP2006208808A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which operability is improved so that maintenance, as to the operations of kits and the like, is facilitated despite its small structure. <P>SOLUTION: While a cam holder handle 41 is pushed in (FIG. 6(a), (b)), a cam follower 49 is pushed up along the cam groove 48a of an advancing/retracting cam 48, and a release cam 42 is rotated clockwise while sliding its cam face 42a over the cam face 48b of a cam 48. Consequently, an optical writing head 11 is set in a regular position. When the cam holder handle 41 is pulled forward (FIG. 6(c)(d)), the cam follower 49 is pushed down along the cam groove 48a of the advancing/retracting cam 48, and the release cam 42 is rotated counterclockwise while sliding its cam face 42a over the cam face 48b of the cam 48. Consequently, the optical writing head 11 is rotated into a retracted position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that is small and in which an image forming unit can be easily attached and detached.

  Conventionally, there is an electrophotographic image forming apparatus. Particularly in recent years, tandem that performs full-color printing (including printing or image formation, and so on) on paper (sheet-like image forming medium, and so on) using toners of four colors, cyan, magenta, yellow, and black. Type page printers have been put into practical use.

  Usually, in an electrophotographic image forming apparatus, a photoreceptor kit and a development kit are integrated into an image forming unit, and an optical writing head is further assembled into the image forming unit to form an image forming unit. The

The image formed by the image forming unit is transferred to a sheet fed from a sheet feeding device, is carried into a fixing unit, and is fixed on the sheet by heat and pressure, and is discharged outside the apparatus.
By the way, when a paper jam or image formation failure occurs, maintenance must be performed to recover from the failure. Also, when replacing old and new kits or units, replacement maintenance must be performed in the same manner.

  In such a case, instead of taking out the optical writing head, photoconductor kit, developing kit, etc. from the image forming apparatus main body and disassembling them separately, it is necessary to separate them separately so that they can be taken out separately. The work becomes troublesome and cumbersome.

For this purpose, the lid on the upper surface of the apparatus main body is opened, and the optical writing head attached to the back surface of the lid via a support member is lifted to the outside along with the rotation of the lid. There is a configuration in which the kits left inside can be taken out to the outside. (For example, see Reference Document 1.)
Also, the upper part of the main body of the apparatus is configured to be able to move largely upward, and the kits are configured to be supported on the upper part via a support member, where the kits can be pulled out to the outside. is there. (For example, see Reference 2.)
JP 09-160333 A ([Summary], FIG. 1) Japanese Patent Laying-Open No. 2001-242663 ([Summary], FIG. 5)

  However, in the method of performing maintenance by opening the upper body (a group of optical writing heads attached to the back surface of the lid via a support member) as in Patent Document 1, the lid on the upper surface is opened in a single manner around the hinge. However, the top cover also serves as a paper discharge tray. Therefore, the upper body cannot be opened without removing the image-formed paper placed on the top surface of the cover that also serves as the paper discharge tray. There is a trouble.

  In this case, as shown in Patent Document 1, there is a type in which the kit is left at the lower part of the apparatus main body and a type in which the kit is lifted upward together with the upper body, although not particularly shown. The former type that leaves the kit in the lower part of the main body can lighten the upper part of the rotating machine body. However, for the recovery processing of paper jam that occurs in the transport path below the kit, the kit must be used. Furthermore, the trouble of taking it out is attached.

  In addition, the latter type that lifts multiple kits together with the upper body, such as the latter, has a preferable structure in which excessive weight is added to the mechanism that rotates around the hinge, and fatigue over time occurs in the entire maintenance mechanism at an early stage. It was hard to say that there was.

  In Cited Document 2, since the trouble of removing the paper is eliminated and the problem of excessive load on only a part of the mechanism is solved, the operability is improved and the life of the maintenance mechanism is extended. Has been made.

However, there remains a problem that the link mechanism is complicated and the apparatus is enlarged in order to prevent the kit from being tilted using the parallel link and to support the weight of the kit.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus with improved operability that can easily perform a kit operation and a maintenance process of a paper jam restoration process in a small configuration in view of the above-described conventional situation. .

The configuration of the image forming apparatus according to the present invention will be described below.
An image forming apparatus according to the present invention includes an image forming unit having at least a photosensitive drum on which an electrostatic latent image is formed, which is detachable in the drum axis direction. An optical writing head for optically writing a recording signal is rotatable in a direction perpendicular to the drum axis and to an optical writable position with respect to the photosensitive drum and a retracted position that does not interfere with the attachment / detachment of the image forming unit. A head support mechanism for supporting is provided.

  The head support mechanism includes, for example, an advance / retreat cam device provided in the head support mechanism and a turning cam device that is slidably engaged with the advance / retreat cam device to move the optical writing head to the optical writable position and the retracted position. Configured to pivot to a position.

  In this case, the head support mechanism is configured such that, for example, the advance / retreat cam device advances / retreats in the long axis direction, and the rotating cam device slides on the arc surface of the advance / retreat cam device in accordance with the advance / retreat of the advance / retreat cam device. The optical writing head can be configured to rotate between the optical writable position and the retracted position by pivoting.

Further, the advancing / retreating cam device may be configured to advance / retreat in the major axis direction by an operation from the outside of a cam holder squeeze that holds the advancing / retreating cam device.
Further, in this image forming apparatus, for example, the head support mechanism includes an advancing / retreating cam device having an arc surface that advances / retreats in the major axis direction and a cam groove formed on the arc surface, and responds to the advance / retreat of the advancing / retreating cam device. A rotating cam device that rotates forward or backward along the arc surface while slidingly contacting the arc surface and the cam groove, and the advance / retreat cam device causes the optical writing head to be moved by an urging member. The door is biased to rotate to the retracted position, and the door is engaged with the door to return the optical writing head to the optical writable position against the biasing force of the biasing member by closing the door. Configured to match.

  According to the present invention, the head support mechanism that rotatably supports the photosensitive drum at the optical writable position and the retracted position that does not interfere with the attachment / detachment of the image forming unit is provided. A gap can be formed in the intricate portion by changing the distance between the writing head and the photosensitive drum, and therefore, the photosensitive kit can be easily moved in the longitudinal direction thereof. It is possible to provide an image forming apparatus with improved operability of kits such as a development kit.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating an internal configuration of a secondary transfer image forming apparatus (hereinafter simply referred to as a printer) in Embodiment 1 of the present invention. A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, which includes four image forming units 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a conveyance for duplex printing. The unit 5 is configured.

  The four image forming units 2 have a configuration in which four image forming units 6 (6M, 6C, 6Y, 6K) are arranged side by side in a multistage manner from right to left in FIG. Of the four image forming units 6, three image forming units 6M, 6C and 6Y on the upstream side (the right side in the figure) are magenta (M), cyan (C) and yellow (subtractive three primary colors, respectively). A mono-color image is formed with the color toner of Y), and the image forming unit 6K forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 6 has the same configuration except for the color of the toner stored in the toner container. Accordingly, the configuration of the black (K) image forming unit 6K will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 11, and a developing roller 13 of the developing device 12 are arranged around the periphery of the photosensitive drum 7.

  The developing device 12 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the drawing. The intermediate portion is provided with a toner replenishing mechanism for the lower portion, the lower portion is provided with the above-described developing roller 13 at the side opening, the toner stirring member inside, the toner supply roller for supplying toner to the developing roller 13, and the developing A doctor blade or the like for regulating the toner layer on the roller 13 to a constant layer thickness is provided.

  The intermediate transfer belt unit 3 has an endless transfer belt 14 extending in a flat loop shape from substantially the left and right sides of the figure at the approximate center of the main unit, and the transfer belt 14 is stretched over the transfer belt 14. A driving roller 15 and a driven roller 16 are provided to circulate and move the belt 14 counterclockwise in the drawing.

  The transfer belt 14 transfers the toner image directly onto the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 3 includes a belt position control mechanism 17 in the loop of the flat loop-shaped transfer belt 14. The belt position control mechanism 17 includes a primary transfer roller 18 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 7 via the transfer belt 14.

  The belt position control mechanism 17 has three primary transfer rollers 18 corresponding to the three image forming units 6M, 6C, and 6Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. The image is transferred to the center at the same cycle, and the one primary transfer roller 18 corresponding to the black (K) image forming unit 6K is rotated at a rotation cycle different from the cycle of the three primary transfer rollers 18 for transfer. The belt 14 is moved away from the photosensitive drum 7, and the full color mode (all four primary transfer rollers 18 are in contact with the transfer belt 14) and the monochrome mode (only the primary transfer roller 18 corresponding to the image forming unit 6K is the transfer belt). 14) and all non-transfer mode (all four primary transfer rollers 18 are separated from the transfer belt 14).

  In the intermediate transfer belt unit 3, a belt cleaner unit is disposed further upstream of the uppermost image forming unit 6M on the upstream side in the belt movement direction, and is flat and thin so as to be substantially along the entire lower surface. The waste toner collection container 19 is detachably disposed.

  The paper feed unit 4 includes two paper feed cassettes 21 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the figure) of the two paper feed cassettes 21, respectively, A feeding roller 23, a separating roller 24, and a standby conveying roller pair 25 are disposed. In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 25, a secondary transfer roller 26 that is in pressure contact with the driven roller 16 via the transfer belt 14 is disposed, and the secondary transfer portion to the paper is arranged. Forming.

  A belt-type heat fixing device 27 is disposed downstream (upward in the drawing) of the secondary transfer portion, and the sheet after fixing is fixed to the belt-type heat fixing device 27 further downstream of the belt-type heat fixing device 27. A pair of carry-out rollers 28 for carrying out the paper and a pair of paper discharge rollers 31 for discharging the carried paper to a paper discharge tray 29 formed on the upper surface of the apparatus are disposed.

  The duplex printing conveyance unit 5 includes a start return path 32a that branches from the intermediate conveyance path between the carry-out roller pair 28 and the discharge roller pair 31 to the right lateral direction in the drawing, and then an intermediate return path 32b that bends downward. A terminal return path 32c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 33a, 33b, 33c, and 33d arranged in the middle of these return paths are provided. ing. The exit of the end return path 32 c communicates with a conveyance path to the standby conveyance roller pair 25 corresponding to the sheet feeding cassette 21 below the sheet feeding unit 4.

  In this example, a cleaning unit 35 and a take-in roller 36 are disposed on the upper surface of the intermediate transfer belt unit 3. The cleaning unit 35 comes into contact with the upper surface of the transfer belt 14 to scrape and remove the waste toner, and the take-in roller 36 takes over the waste toner removed by the cleaning unit 35, and a temporary storage unit of the belt cleaner unit (not shown). The accumulated waste toner is conveyed to the upper part in the dropping cylinder by a conveying screw and sent to the waste toner collecting container 19 through the dropping cylinder.

  Further, in order to bring the cleaning unit 35 into pressure contact with the transfer belt 14 with an appropriate pressure, a pressure roller 37 is provided on the intermediate transfer belt unit 3 side to press the transfer belt 14 toward the cleaning unit 35 from below. ing.

  As shown in FIG. 1, the image forming apparatus 1 does not directly transfer a toner image onto a conventional sheet, but an intermediate transfer belt on a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 25. 14 is a method of transferring a toner image through the image forming apparatus 14.

Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.
In addition, since troubles such as paper jams do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as kits concentrated on the left side of FIG. 1 may be a small space that can be replaced in the longitudinal direction. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is a perspective view showing the state in which the four optical writing heads thus miniaturized are respectively housed in the head holder and collectively held in the holder base. is there.

  FIG. 2 shows the optical writing head 11, the head holder 38, and the holder base 39. Further, for reference showing the positional relationship with these, the photosensitive drum 7 positioned directly below the optical writing head 11 via the head cover is also shown.

  3 is a cross-sectional view taken along the line AA ′ of FIG. FIG. 3 shows the optical writing head 11, the head holder 38, the holder base 39, and the photosensitive drum 7, a cam holder squeeze 41, a release cam 42 as a rotating cam, a head supporter 43, and a drum cover 44. , And the head rotation support part 45 are shown.

  4 is a cross-sectional view taken along the line BB ′ of FIG. In FIG. 4, the optical writing head 11, the head holder 38, the holder base 39, and the photosensitive drum 7, and the cam holder grudge 41 interposed between the head holder 38 and the optical writing head 11, The release cam 42, the head supporter 43, and the head spring 46 are shown.

  FIG. 5A is a perspective view showing the configuration shown in FIG. 4 with the holder base 39 removed, and FIG. 5B is a perspective view showing the configuration shown in FIG. 5A with the head holder 38 removed. is there. As shown in FIG. 5 (b), the cam holder ridge 41 is integrally attached to a cam holder 47 that extends along the longitudinal direction of the head supporter 43.

  The cam holder 47 holds, at both ends thereof, an advancing and retreating cam 48 having an arcuate concave cam surface whose cross section is substantially ¼ of a circle having a shape substantially divided into four in the radial direction of the cylinder. In FIG. 5 (b), the advancing / retreating cam 48 is viewed from the convex outer side.

  A gentle helical cam groove 48a reaching the convex outer side is formed on the arc-shaped concave cam surface inside the advance / retreat cam 48. The advancing / retracting cam 48 is configured to be movable back and forth in the longitudinal direction on the head supporter 43 by operating the cam holder squeezing 41, but rotation around the shaft is prohibited.

  FIG. 6A is a perspective view showing the configuration in the vicinity of the cam holder kneading 41 when the optical writing head 11 is at the normal position (optical writing position), with the viewing angle being slightly enlarged. 6 (b) is a perspective view seen from the substantially lateral direction.

  FIG. 6 (c) is a diagram showing a state when the optical writing head 11 is released from the normal position from the state of FIG. 6 (a), and FIG. FIG. FIG. 6E is an enlarged perspective view showing the configuration of the main part of the release cam 42.

The release cam 42 is configured to be rotatable around its axis, but is prohibited from moving in the longitudinal direction.
Further, as shown in FIGS. 6A and 6C, the drum cover 44 is a member that extends from the upper side to the right side of the photosensitive drum 7, and is developed to the upper side at the concave portion 44a that extends to the right side. A toner cartridge of the developing device 12 is disposed, and a developing unit in which a developing roller 13 of the developing device 12 and other toner supply members are disposed is disposed below.

  As shown in FIG. 6 (e), the release cam 42 is formed with a cam follower 49 that fits into the cam groove 48a of the advance / retreat cam 48 on the cam surface 42a. Accordingly, the release cam 42 is engaged with the cam groove 48a and the cam surface 48b of the advance / retreat cam 48.

  As shown in FIG. 6 (b), in the state where the cam holder ridge 41 is pushed in the back direction (left side in the figure), the cam follower 49 is formed along the cam groove 48a formed in a gentle spiral shape, that is, obliquely. Is pushed up.

  As the cam follower 49 is pushed up, the release cam 42 slides the cam surface 42a against the concave cam surface 48b of the advance / retreat cam 48 as shown in FIG. It rotates about the axis in the clockwise direction of FIG. 6 (a).

  In this state, the position of the cam surface 48b of the advance / retreat cam 48 with respect to the release cam 42 changes so as to be farther from the axis of the release cam 42 than before the release cam 42 rotates. In this state, the optical writing head 11 is set to the normal position by the biasing force of the head spring 46 shown in FIG.

  On the other hand, as shown in FIG. 6 (d), when the cam holder squeeze 41 is pulled out in the front direction (right side in the figure), the cam follower 49 is lowered along the cam groove 48a formed in a spiral shape (oblique). Pushed down.

  As the cam follower 49 is pushed down, the release cam 42 slides the cam surface 42a on the concave cam surface 48b of the advance / retreat cam 48 as shown in FIG. It rotates about the axis in the counterclockwise direction of FIG. 6 (c).

  In this state, the position of the cam surface 48b of the advance / retreat cam 48 with respect to the release cam 42 changes so as to be closer to the axis of the release cam 42 than before the release cam 42 rotates. Since the shaft position of the release cam 42 does not move, the cam surface 48b, that is, the advance / retreat cam 48 is the cam surface 42a of the release cam 42 by the amount that the cam surface 48b of the advance / retreat cam 48 changes so as to approach the axial direction of the release cam 42. Is pushed to the left in FIG. 6 (c).

  As a result, the head supporter 43 is slightly rotated in the counterclockwise direction as shown in FIG. 6C together with the advance / retreat cam 48 with the head rotation support portion 45 as a fulcrum. By slight rotation of the head supporter 43, a slight gap is formed between the optical writing head 11 and the drum cover 44 immediately above the photosensitive drum 7.

  If this slight gap is formed, the photosensitive drum 7, that is, the photosensitive kit can be pulled out in the axial direction without causing interference with the optical writing head 11. The position setting after the replacement of the photoconductor kit is completed by the operation of the cam holder squeeze 41 similar to the case described in FIGS. 6 (a) and 6 (b).

  Although not particularly illustrated, the image forming apparatus 1 shown in FIG. 1 is provided with an open / close door for maintenance on the front surface (the front side in the depth direction of the paper in FIG. 1). The kits such as the above-described photoreceptor kits are pulled out in the axial direction after the opening / closing door is opened.

  Therefore, an urging member for urging the cam holder 47 to push forward is provided, and the cam holder 47 is automatically pushed toward the front of the apparatus by the urging force of the urging member when the door is opened. Then, when the door is opened, a gap is automatically formed between the optical writing head 11 and the drum cover 44 as shown in FIGS. 6C and 6D. It is convenient that the photoreceptor kit can be pulled out in the axial direction immediately after the opening / closing door is opened.

  In addition, the shape of the cam holder ridge 41 is changed from a vertical shape to a horizontal shape, and is configured to be in sliding contact with the inside of the door, and the cam holder ridge 41 is biased by the door when the door is closed. It is configured to be pushed inside against the biasing force of the member.

  As a result, as shown in FIGS. 6 (a) and 6 (b), the optical writing head 11 and the drum cover can be simply closed by closing the opening / closing door without taking the trouble of pushing the cam holder grinder 41. The gap between the optical writing head 11 and the optical writing head 11 is automatically set to the normal position.

(Embodiment 2)
Next, positioning of the optical writing head 11 and the photosensitive drum 7 will be described below as a second embodiment.

  FIG. 7 is a sectional view showing the image forming unit 6 also shown in the first embodiment together with the head holder 38. The head holder 38 holds the optical writing head 11. Further, the developing device 12 shown in FIG. 1 is divided into an upper toner cartridge 51 and a lower developing portion 52 as shown in FIG.

  Further, the photosensitive drum 7 and the developing unit 52 are integrally incorporated via a drum cover 44. In addition to the developing roller 13 already described, the developing unit 52 has a toner supply roller 53 for supplying toner to the developing roller 13 and a layer of toner supplied on the developing roller 13 with a certain thickness. A doctor blade 54 or the like is provided.

  As described with reference to FIGS. 6A to 6D, when the photosensitive drum 7 and the optical writing head 11 are relatively in contact with each other, when the optical writing head 11 is set at the normal position, Usually, a positioning device such as an abutment pin or a slide cam is often used for the positioning. In this example, a spacer is used for positioning between the photosensitive drum 7 and the optical writing head 11.

FIGS. 8A, 8B, and 8C are diagrams showing the arrangement positions of the spacers as the second embodiment on the photosensitive drum.
FIG. 9 (a) is a diagram showing an actual assembled state of the spacer as the second embodiment, and FIG. 9 (b) is a diagram showing an operating state together with FIG. 9 (a).

  In FIGS. 8A, 8B, and 8C, the spacer 55 is shown as a single unit for easy understanding of the arrangement position on the photosensitive drum. Rather than being arranged alone as shown in FIGS. 8 (a), (b) and (c), it is integrated with the bearing 56 of the charging roller 9 as shown in FIGS. 9 (a) and (b). Attached.

  As shown in FIG. 8A, the spacer 55 is disposed so as to be in sliding contact with the boundary portion 58 of the flange 57 (57a, 57b) at both ends of the photosensitive drum 7 with the drum portion 7-1. . Thereby, as shown in FIG. 9A, the interval between the photosensitive drum 7 and the optical writing head 11 is positioned.

  As shown in FIGS. 8B and 8C, the flange 57a at one end of the photosensitive drum 7 has a boundary portion 58 with the drum portion 7-1, a gear portion 59, and a main body drive. It consists of an engaging part 61 with the system.

Further, the flange 57b at the other end of the photosensitive drum 7 includes a boundary portion 58 with the drum portion 7-1 and a gear portion 62 as shown in FIG.
The engaging portion 61 is rotated by being engaged with the drive system of the main body apparatus, and is engaged with the rotation system of the image forming unit by the gear portions 59 and 62 at both ends, and is arranged in the image forming unit. The rotational drive is transmitted to the rotating member provided.

  The charging roller 9 shown in FIG. 1 is made of a conductive resin sponge, and when the image forming apparatus 1 is performing printing operation, the charging roller 9 is pressed against the photosensitive drum 7 as shown in FIG. is doing. As described above, the photosensitive drum 7 and the charging roller 9 are rotated in the same tangential direction at the same linear velocity during the printing operation of the image forming apparatus 1, so that the charging roller 9 is not affected by deformation or the like.

  However, when the printing operation of the image forming apparatus 1 is interrupted or stopped, the sponge-like surface of the charging roller 9 is deformed while the charging roller 9 is kept in pressure contact with the photosensitive drum 7. When the image forming apparatus 1 starts the printing operation, the initialization charging by the charging roller 9 is not uniformly performed, and the toner image is not properly developed on the photosensitive drum 7.

  Therefore, when the printing operation of the image forming apparatus 1 is interrupted or stopped, the charging roller 9 is released from the pressure contact with the photosensitive drum 7 as shown in FIG. Various methods (mechanisms or mechanisms) for releasing the charging roller 9 from the pressure contact with the photosensitive drum 7 have been conventionally proposed or put into practical use.

  In this example, the bearing 56 of the charging roller 9 is moved in conjunction with the separation and contact between the photosensitive drum 7 and the optical writing head 11 to thereby press the charging roller 9 against the photosensitive drum 7 (FIG. 9 ( a) (see Fig. 9 (b)) and the pressure release operation (see Fig. 9 (b)).

  The spacer 55 of this example is integrated with the bearing 56 of the charging roller 9 as described above, and thus interlocks with the operation of pressing and releasing the charging roller 9 against the photosensitive drum 7. As a result, the spacer 55 is in contact with and away from both ends of the photosensitive drum 7, and the both ends of the optical writing head 11 are in contact with and away from the spacer 55.

  Since the spacer 55 is integrated with the bearing 56 of the charging roller 9 as described above, the position does not fluctuate even when the photosensitive drum 7 and the optical writing head 11 are separated from each other, as shown in FIG. As described above, when the photosensitive drum 7 and the optical writing head 11 are in contact with each other, they are always inserted at the same position, and thereby the interval between the photosensitive drum 7 and the optical writing head 11 is set. Is always positioned stably.

2 is a cross-sectional view illustrating an internal configuration of a secondary transfer image forming apparatus (printer) according to Embodiment 1. FIG. It is the perspective view which looked at the state where the head holder which accommodated four optical writing heads was collectively held by the holder base from the lower part. FIG. 3 is a cross-sectional view taken along the line AA ′ in FIG. 2. FIG. 3 is a cross-sectional view taken along the line BB ′ in FIG. 2. FIG. 5A is a perspective view in which the holder base is removed from the configuration shown in FIG. 4, and FIG. 5B is a perspective view in which the head holder is removed from FIG. (a) is a perspective view showing the configuration near the cam holder squeeze when the optical writing head is in the normal position, (b) is a perspective view seen substantially from the side, and (c) is from the state of (a). FIG. 7 is a diagram showing a state when the optical writing head is released from the normal position, (d) is a perspective view seen from substantially the lateral direction, and (e) is an enlarged perspective view showing a configuration of a main part of the release cam. It is sectional drawing which shows an image forming unit with a head holder. (a), (b), (c) is a figure which shows the arrangement | positioning position to the photosensitive drum of the spacer as Embodiment 2. FIG. (a) is a figure which shows the actual installation state of the spacer as Embodiment 2, (b) is a figure which shows the operation state with (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Image formation part 3 Intermediate transfer belt unit 4 Paper feed part 5 Duplex printing conveyance unit 6 (6M, 6C, 6Y, 6K) Image formation unit 7 (7m, 7c, 7y, 7k) Photosensitive drum 7-1 Drum unit 8 Cleaner 9 Charging roller 11 Optical writing head 12 Developer 13 Developing roller 14 Transfer belt 15 Driving roller 16 Driven roller 17 Belt position control mechanism 18 Primary transfer roller 19 Waste toner collection container 21 Paper feed cassette 22 Paper take-out roller 23 Feed roller 24 Rolling roller 25 Standby transport roller pair 26 Secondary transfer roller 27 Belt-type heat fixing device 28 Transport roller pair 29 Paper discharge tray 31 Paper discharge roller pair 32a Start return path 32b Intermediate return path 32c End return path 33a, 33b 33c, 33d Return roller pair 35 Cleaning unit 36 Rolling roller 37 Pressing roller 38 Head holder 39 Holder base 41 Cam holder squeezing 42 Release cam 43 Head supporter 44 Drum cover 44a Recessed portion 45 Head rotation support portion 46 Head spring 47 Cam holder 48 Advance / retreat cam 48a Cam groove 48b Cam surface 49 Cam follower 51 Toner cartridge 52 Developing section 53 Toner supply roller 54 Doctor blade 55 Spacer 56 Bearing

Claims (5)

In an image forming apparatus comprising an image forming unit having at least a photosensitive drum on which an electrostatic latent image is formed, detachably in the drum axis direction,
An optical writing head for optically writing a recording signal corresponding to image formation information to the photosensitive drum is in a direction perpendicular to the drum axis, and a position where optical writing is possible with respect to the photosensitive drum and attachment / detachment of the image forming unit. An image forming apparatus comprising: a head support mechanism that rotatably supports a retracted position without any hindrance.   The head support mechanism is configured to move the optical writing head to the optical writable position and the retracted position by rotating an advance / retreat cam device provided in the head support mechanism and a rotation cam device slidingly engaged with the advance / retreat cam device. The image forming apparatus according to claim 1, wherein the image forming apparatus is rotated.   The head support mechanism is configured such that the advance / retreat cam device advances / retreats in the major axis direction, and the turning cam device rotates forward / reversely in sliding contact with the arc surface of the advance / retreat cam device according to the advance / retreat of the advance / retreat cam device. 3. The image forming apparatus according to claim 2, wherein the optical writing head is rotated to the optical writable position and the retracted position.   4. The image forming apparatus according to claim 3, wherein the advance / retreat cam device advances / retreats in a major axis direction by an operation from outside of a cam holder squeeze that holds the advance / retreat cam device. The head support mechanism is
An advancing and retracting cam device having an arc surface that advances and retracts in the long axis direction and a cam groove formed on the arc surface;
A rotating cam device that rotates forward or backward along the arc surface while slidingly contacting the arc surface and the cam groove according to the advance / retreat of the advance / retreat cam device;
With
The advance / retreat cam device is urged by an urging member to rotate the optical writing head to the retracted position, and the optical writing head resists the urging force of the urging member by closing the opening / closing door. The image forming apparatus according to claim 1, wherein the image forming apparatus is engaged with the open / close door to return the image to the optical writable position.