JP2002148910A - Color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem color image forming apparatus which can be miniaturized and manufactured at a low cost while preventing adhesion of dust and toner on the seal glass of a raster scanning unit. SOLUTION: A pair of optical path forming pates are provided in parallel with the axial direction of a photoreceptor drum across the optical path of a laser beam between each image forming engine and a raster scanning unit. Shutter members which cover the laser beam irradiation hole of the raster scanning unit from an image forming engine by suitably advancing in the optical path is provided between the optical path forming plates. Furthermore, a shutter opening/closing arm connected with all shutter members is provided to open and close all shutter members simultaneously by driving the shutter opening/ closing arm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color electrophotographic copying machine or a color laser beam printer, and more particularly to a plurality of image forming engines for forming a toner image corresponding to image information. The present invention relates to an improvement in a color image forming apparatus that obtains a color recorded image by multiply transferring a toner image formed by an image forming engine to a recording sheet.

[0002]

2. Description of the Related Art Heretofore, after a photosensitive drum has been exposed to a laser beam emitted from a raster scanning unit, an electrostatic latent image formed on the photosensitive drum by the exposure has been developed with toner and developed. A so-called laser beam printer that forms a recording image according to image information by transferring a toner image onto a recording sheet is known. In the raster scanning unit, a laser light source that emits a laser beam modulated by image information, and scans the laser beam emitted from the laser light source along the axial direction of the photosensitive drum (hereinafter, referred to as “main scanning direction”). A polygon mirror and the like are provided. A laser beam scanned by a polygon mirror that rotates at high speed is refracted and reflected by a plurality of lenses and mirrors, and then a slit-shaped irradiation port provided in a housing of a raster scanning unit. And reaches the photosensitive drum.

[0003] In order to prevent dust and toner from entering the raster scanning unit, which is a precision optical device, usually,
The irradiation port is sealed by a seal glass, and the laser beam is irradiated on the photosensitive drum through the seal glass. However, if dust or toner adheres to the seal glass, the laser beam scanned in the main scanning direction will be blocked at a specific position on the seal glass, and the recorded image will appear in the rotation direction of the photosensitive drum (hereinafter referred to as the rotation direction). ,
White streaks along the “sub-scanning direction”) occur. Such adhesion of dust or toner to the seal glass is likely to occur, for example, when a photosensitive drum or a developing device made into a cartridge is attached to or detached from an image forming apparatus. It is also caused by leaking from Further, in recent years, the size of a laser beam printer has been reduced to a tabletop, and there has been a case where a raster scanning unit has to be arranged below a developing device due to an in-machine layout for achieving such size reduction. In such a case, the toner may unintentionally drop from the developing device onto the seal glass.

For this reason, in the laser beam printer disclosed in Japanese Patent Application Laid-Open No. 4-366868, a shutter member for covering a laser beam irradiation port of a raster scanning unit is provided, and the shutter member is opened only when a photosensitive drum is exposed. In such a case, the irradiation port of the raster scanning unit is exposed, and at other times, the irradiation port is covered by a shutter member to prevent dust and toner from adhering to the seal glass as much as possible.

[0005]

On the other hand, in recent years, in order to improve the productivity of a color recorded image, a plurality of image forming engines including a photosensitive drum and a developing device are arranged in parallel and each image forming engine is arranged in parallel. A so-called tandem type in which yellow, magenta, cyan, and black toner images formed by an image engine are continuously transferred to a recording sheet or an intermediate transfer belt, thereby forming a color recorded image at high speed. Color image forming apparatuses have also appeared.

In this tandem type color image forming apparatus, since a raster scanning unit individually exposes the photosensitive drums of four image forming engines, it is tentatively disclosed in Japanese Unexamined Patent Publication No.
In order to prevent a dust or the like from adhering to the seal glass by providing a shutter member as disclosed in JP-A-366868, it is necessary to provide a shutter member for each image forming engine.
However, providing the driving means individually for the four shutter members requires extra space around each image forming engine, which not only makes it impossible to reduce the size of the color image forming apparatus, Production costs also increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the size and cost of a raster scanning unit while preventing dust and toner from adhering to a seal glass. It is an object of the present invention to provide a tandem type color image forming apparatus capable of achieving the above.

[0008]

To achieve the above object, a color image forming apparatus according to the present invention comprises: a raster scanning unit for emitting a laser beam modulated by image information;
A plurality of image forming engines having a photosensitive drum exposed by the laser beam and forming a toner image corresponding to the image information, wherein the toner images formed by the respective image forming engines are multiplex-transferred to a recording sheet. Assuming a color image forming apparatus for forming a color recording image, a pair of optical paths are provided between each imaging engine and the raster scanning unit in parallel with the axial direction of the photosensitive drum with the optical path of the laser beam interposed therebetween. While the forming plate is provided, a shutter member is provided between these optical path forming plates to shield the laser beam irradiation port of the raster scanning unit from the image forming engine by appropriately advancing into the above optical path. A shutter opening / closing arm connected to the shutter is provided, and all shutter members are simultaneously opened by driving the shutter opening / closing arm. It is characterized in that it has configured to.

According to such technical means, a shutter member for shielding the laser beam irradiation port of the raster scanning unit is provided for each image forming engine, and all shutter members are connected to one opening / closing arm. By driving the opening / closing arm, all the shutter members are configured to open and close at the same time. Therefore, it is not necessary to provide a mechanism for opening and closing each shutter member. By effectively utilizing the space around the image engine, it is possible to promote downsizing and cost reduction of such an apparatus.

In the case where a plurality of shutter members are simultaneously opened and closed by a single opening / closing arm, depending on an assembling error of the shutter members with respect to the opening / closing arm, even if only some of the shutter members are completely opened, other shutter members may be opened. The member is opened only halfway, and as a result, there is a concern that exposure of the photosensitive drum by the laser beam may be hindered by the shutter member. Therefore, from this viewpoint, the shutter member and the opening / closing arm are connected via the elastic member, and even when some of the shutter members are completely opened, the remaining shutter members are moved by continuing to move the opening / closing arm. It is preferable to configure so that it can be completely opened. In addition, with this configuration, even if there is an assembly error between the opening / closing arm and the shutter member, all the shutter members can be completely closed, and dust adheres to the seal glass of the raster scanning unit. It can be performed effectively.

Further, from the same viewpoint, a flexible plate member such as a resin film is provided at the tip of the shutter member, and when the shutter member is closed, the tip of the shutter member is elastic with respect to the optical path forming plate. It is preferable to be configured so as to be pressed against.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the configuration of a tandem type color laser beam printer to which the present invention is applied. The laser beam printer includes four image forming engines 10Y, 10Y, 10Y, 10C, which form toner images for respective colors of yellow, magenta, cyan, and black.
M, 10C, and 10Bk, and an intermediate transfer belt (IB) on which a toner image is primarily transferred from each image forming engine.
T) 20, which is configured to form a full-color image by secondarily transferring the toner image multiplex-transferred onto the intermediate transfer belt 20 to the recording sheet P.

The intermediate transfer belt 20 is formed endless and is wrapped around a pair of belt transport rollers 21 and 22. The intermediate transfer belt 20 is rotated in the direction of an arrow by each of the color image forming engines 10Y, 10M, 10C and 10Bk. It is configured to receive primary transfer of the formed toner image. Further, one of the belt transport rollers 21 with the intermediate transfer belt 20 interposed therebetween.
A recording sheet P is inserted between the transfer roller 30 and the intermediate transfer belt 20 that are in pressure contact with each other, and the toner image is transferred from the intermediate transfer belt 20 to the secondary transfer roller 30. It is designed to receive secondary transfer. That is, the belt transport roller 21 functions as a backup roller of the transfer roller 30. On the other hand, a belt cleaner 23 of the intermediate transfer belt 30 is provided at a position facing the belt transport roller 22 located on the opposite side, and the toner remaining on the intermediate transfer belt 20 after the secondary transfer is removed on the intermediate transfer belt 20. Is configured to be removed from.

Below the intermediate transfer belt 20, the four image forming engines 10Y, 10M, 10C and 10B described above are provided.
k are arranged in parallel so that a toner image formed according to image information of each color is primarily transferred to the intermediate transfer belt 20. These four image forming engines are arranged in the order of yellow 10Y, magenta 10M, cyan 10C, and black 10Bk along the rotation direction of the intermediate transfer belt 20, and form the black image which will be used most frequently. The image engine 10Bk is arranged closest to the secondary transfer position. In addition, these image forming engines 10Y, 10Y
Below the M, 10C, and 10Bk, a raster scanning unit 40 that exposes the photosensitive drum 11 provided in each image forming engine in accordance with image information is provided. The raster scanning unit 40 includes all image forming engines 10Y, 10M,
Four semiconductor lasers (not shown) that emit a laser beam Bm modulated according to image information of each color and are shared by 10C and 10Bk, and these four laser beams Bm are rotated at a high speed and a photoconductor is used. A polygon mirror 41 that scans along the axial direction of the drum 11; Each laser beam Bm scanned by the polygon mirror 41 travels along a predetermined path while being reflected by a mirror (not shown), and then passes through each of the image forming engines through an irradiation port 42 provided above the raster scanning unit 40. 10
The Y, 10M, 10C, and 10Bk photosensitive drums 11 are exposed.

The image forming engines 10Y, 10M, 1
Reference characters 0C and 10Bk denote a photosensitive drum 11, a charging roller 12 for charging the photosensitive drum 11 to a uniform background potential, and an electrostatic roller formed on the photosensitive drum 11 by exposure to the laser beam Bm. A developing device 13 for developing a latent image to form a toner image; and a drum cleaner 14 for removing residual toner and paper dust from the surface of the photosensitive drum 11 after transferring the toner image to the recording sheet P. It is configured such that a toner image corresponding to image information of each color can be formed on the photosensitive drum 11. The developing device 13 is of a type using a two-component developer in which a toner and a carrier are mixed. In order to omit maintenance of replacement of the developer due to aging, the toner and the carrier are supplied from a replenishment cartridge (not shown). A so-called trickle developing method of replenishing the mixed developer and automatically discharging the deteriorated developer is used.

Each of the image forming engines 10Y, 10M, 10C,
The primary transfer roller 15 is positioned at a position facing the photoconductor drum 11 of 10 Bk so as to sandwich the intermediate transfer belt 20.
Y, 15M, 15C, and 15Bk are provided. By applying a predetermined transfer bias voltage to the transfer rollers 15Y, 15M, 15C, and 15Bk, the photosensitive drum 11 and the transfer rollers 15Y, 15M, and 15C are applied. , 1
5Bk, an electric field is formed, and the charged toner image on the photosensitive drum 11 is transferred to the intermediate transfer belt 20 by Coulomb force.

On the other hand, the recording sheet P is transferred from the paper feed cassette 2 stored in the lower portion of the printer housing 1 to the inside of the printer, specifically, to a secondary transfer position where the intermediate transfer belt 20 and the secondary transfer roller 30 are in contact. Supplied. Paper feed cassette 2
Is configured to be set by being pushed into the lower portion of the printer housing 1 from the front side of the printer housing (the front side in FIG. 1), and the upper portion of the set paper feed cassette 2 is inserted into the cassette 2. A pickup roller 24 and a paper feed roller 251 for pulling out the stored recording sheet P are provided side by side. Further, a retard roller 26 for preventing double feeding of the recording sheet P is provided at a position facing the paper feed roller 25.

The transport path 27 for the recording sheet P inside the printer is provided substantially vertically along the left side surface of the printer housing 1 and is drawn out of the paper feed cassette 2 located at the bottom of the printer housing 1. The recording sheet P rises along the sheet transport path 27, receives the transfer of the toner image at the above-described secondary transfer position, and is sent to the fixing device 3 provided immediately above the secondary transfer position. Then, the recording sheet P on which the toner image is fixed by the fixing device 3 is discharged face-down to a discharge tray 1a provided at an upper portion of the printer housing 1 via a discharge roller 28. still,
In FIG. 1, reference numeral 29 denotes a registration roller that controls the timing at which the recording sheet P enters the secondary transfer position.

When a full-color image is formed by the color laser beam printer constructed as described above, first, the raster scanning unit 40 operates the image forming engines 10Y, 10M, 10C and 10B in accordance with the image information of each color.
k, the photosensitive drums 11 are exposed at a predetermined timing, whereby the image forming engines 10Y, 10M, 10C, 1
On the photoconductor drum 11 of 0Bk, a toner image corresponding to the image information is formed. Each imaging engine 10Y, 10M, 10M
The toner images formed at C and 10Bk are sequentially transferred to the rotating intermediate transfer belt 20, and a multi-toner image in which the toner images of the respective colors overlap is formed on the intermediate transfer belt 20. On the other hand, the recording sheet P is sent out from the paper feed cassette 2 at a predetermined timing, and
At a timing when the toner image primarily transferred onto the secondary transfer position reaches the secondary transfer position, the toner image is inserted between the secondary transfer roller 30 and the intermediate transfer belt 20. Thus, the multiple toner image on the intermediate transfer belt 20 is secondarily transferred to the recording sheet P. Then, the fixing device 3 fixes the toner image on the recording sheet P on which the secondary transfer has been performed, whereby a full-color image is completed on the recording sheet P.

FIG. 2 is an enlarged sectional view showing the structure between the image forming engine 10M and the raster scanning unit 40. However, in this figure, the intermediate transfer belt 20 and the primary transfer roll 15M are omitted. Although not shown in FIG. 1, the raster scanning unit 40 and each image forming engine 10Y,
A middle plate 50 provided with an optical path forming plate, a shutter member, and the like, which will be described later, is provided between the raster scanning unit 40 and each of the image forming engines 10Y, 10M, 10C, and 10Bk. Is partitioned. Each imaging engine 10Y, 10M, 10C, 10
Bk is a process cartridge 51 in which the photosensitive drum 11, the drum cleaner 14, and the charging roller 12 are integrated.
And a developing cartridge 52 of the developing device 13 itself. Each of the cartridges 51 and 52 is inserted from the front side into the printer, and is positioned at a position shown in FIG. 2 by a frame (not shown). Is configured. On the other hand, the laser beam Bm is applied to the upper surface of the housing of the raster scanning unit 40 by each of the image forming engines 10Y and
Irradiation ports 43 for emitting light to the photoconductor drums 11 of 0M, 10C, and 10Bk are formed.
Is formed in an elongated slit shape from the front side to the rear side (rear side in FIG. 2). In addition, this irradiation port 4
Reference numeral 3 is covered with a seal glass 44, and the laser beam Bm is configured to pass through the seal glass 44 and reach the photosensitive drum 11.

The middle plate 50 is provided with an entrance 53 for the laser beam Bm so as to overlap with the irradiation opening 43 of the raster scanning unit 40. This entrance 53
A pair of optical path forming plates 54 and 55 is provided between the optical path forming plate 54 and the photosensitive drum 11 so as to sandwich the optical path of the laser beam Bm. The optical path forming plates 54 and 55 form an optical path chamber 56. Each of the optical path forming plates 54 and 55 is provided over the entire length of the slit-shaped entrance 53, and the optical path forming plate 54 located on the charging roller 12 side with respect to the entrance 53 is fixed to the middle plate 50. It is erected in a state. On the other hand, an optical path forming plate 55 located on the side of the developing unit 13 at the entrance 53 is integrated with the developing unit 13 to constitute a developing cartridge 52, and the developing cartridge 52 is mounted in a printer. Is positioned at the position. In addition, the entrance 53 formed in the middle plate 50
A pair of incident port forming members 57 and 58 are fixed to both sides of, respectively. When the user cleans the surface of the seal glass 44 of the raster scanning unit 40, the entrance forming members 57 and 58 function as guide rails for guiding the cleaning member along the longitudinal direction of the seal glass 44. I have. Reference numeral 59 in FIG. 2 is a seal member for sealing between the entrance port forming member 57 and the optical path forming plate 55.

The leading end of the optical path forming plate 55 integrated with the developing device 13 on the photosensitive drum 11 side is
The optical path forming plate 55 protrudes toward the charging roller 12 side from the closest position between the developing unit 13 and the developing unit 13 so that the optical path forming plate 55 receives the toner cluster even if the toner cluster unintentionally drops from the developing unit 13. This prevents the seal glass 44 of the raster scanning unit 40 from being stained. An optical path chamber 56 formed by a pair of optical path forming plates 54 and 55
The opening on the photosensitive drum 11 side is narrower than the entrance 53 formed in the middle plate 50, and is formed in a substantially triangular cross section. The middle plate 50 is provided with substantially triangular partition walls 60 and 61 (see FIG. 3) corresponding to the front side and the rear side of the optical path chamber 56.
Dust is prevented from entering the optical path chamber 56 from the front side and the rear side.

Further, in order to prevent the toner cloud from entering the optical path chamber 56 from the opening on the photosensitive drum 11 side, in the printer of this embodiment, as shown by a broken line in FIG. A traversing airflow is formed. An air duct 62 for blowing air between the charging roller 12 and the optical path forming plate 54 is provided on the middle plate 50 below the charging roller 12, and the air duct 62 has a front side of the middle plate 50. All imaging engines 10Y, 10M, 1 provided along
A common front duct (not shown) is connected to OC and 10Bk. Therefore, the air sucked into the front duct by a fan (not shown) is
Y, 10M, 10C, and 10Bk, enters the air duct 62, spreads in the air duct 62 in the axial direction of the photoconductor drum 11, and then extends along the back surface of the optical path forming plate 54. Is blown away. Further, an exhaust duct 63 is provided on the middle plate 50 below the developing device 13, and all the image forming engines 10 </ b> Y and 10 </ b> Y provided on the exhaust duct 63 along the rear side of the middle plate 50 are provided. A common rear duct (not shown) is connected to 10M, 10C, and 10Bk. Therefore, the air blown to the photosensitive drum 11 is
It flows into the exhaust duct 63 through the space between the optical path forming plate 55 and the YY, 10M, 10C, and 10Bk, and is discharged outside the machine through the rear duct. Since the gap between the middle plate 50 and the raster scanning unit 40 is sealed by a sealing member (not shown), a pair of optical path forming plates 54 and 5 are provided.
The optical path chamber 56 sandwiched between the photosensitive drums 11 does not become a negative pressure with respect to the atmosphere around the photosensitive drum 11 where the air flow is formed, and the air flow flows to the exhaust duct 63 without entering the storage chamber 56. . As a result, the toner cloud generated around the photosensitive drum 11 does not enter the optical path chamber 56 but is discharged out of the apparatus together with the airflow, and the seal glass 4 of the raster scanning unit 40 is removed.
4 can be effectively prevented from being stained by the toner.

Nevertheless, it is not preferable from the standpoint of quietness to operate the fan that blows air into the air duct 62 at all times, and the power is wasted. And the toner cloud is hardly generated, that is, each image forming engine 10Y,
In a situation where the toner image forming operation is not performed at 10M, 10C, and 10Bk, the fan is stopped and the formation of the airflow is stopped. However, even when the image forming operation is not performed, dust or toner may enter the optical path chamber 56 from the opening on the photosensitive drum 11 side. When the sheet is pulled out of the apparatus, the opening of the optical path chamber 56 is exposed to the outside. Therefore, there is a danger that dust enters the optical path chamber 56 from this opening and adheres to the seal glass 44 of the raster scanning unit 40. There is.

For this reason, in the printer of the present embodiment, a swingable shutter member 64 is provided in the optical path chamber 56,
When the image forming operation is not performed, the seal glass 44 is shielded from the image forming engines 10Y, 10M, 10C, and 10Bk by moving the shutter member 64. FIG. 2 shows that the shutter member 64 is open, and the laser beam Bm crosses the optical path chamber 56 and the photosensitive drum 1
1 shows a state in which exposure is possible. The shutter member 64 indicated by a dashed line in FIG. 2 is in a state where the optical path of the laser beam Bm is closed, and the shutter member 64 connects the laser beam irradiation port 43 of the raster scanning unit 40 to the image forming engines 10Y, 10M, and 10M. It shields from 10C and 10Bk. The swing end of the shutter member 64 has PE
A flexible resin film 65 made of T or the like is attached in a protruding state, and when the shutter member 64 is set to a closed position indicated by a dashed line, the resin film 65 is attached.
Is pressed against the optical path forming plate 55 and is closely attached to the optical path forming plate 55 in a bent state. Further, FIG.
Although not shown in the drawing, the entrance opening forming member 58 located below the shutter member 64 is provided with a seal member that comes into contact with the end on the fulcrum side when the shutter member 64 is closed. ing. Thus, when the shutter member 64 is closed, the inside of the optical path chamber 56 is completely divided into two by the shutter member 64, and dust and floating toner that have entered from the openings of the optical path chamber 56 on the side of the image forming engines 10Y, 10M, 10C, and 10Bk. Entrance 5 of middle plate 50
3, the seal glass 44 of the raster scanning unit 40
Can completely be prevented from adhering.

The entrance forming member 58 located below the pivot point of the shirt member 64 has a groove-shaped collection pocket 66 along the longitudinal direction of the shutter member 64.
When dust or the like attached to the surface of the shutter member 64 on the side of the image forming engines 10Y, 10M, 10C, and 10Bk is opened, the dust drops into the collection pocket 66 when the shutter member 64 is opened. It can be collected inside. In addition, in the printer of this embodiment, one of the optical path forming plates 55 forming the optical path chamber 56 is integrated with the developing cartridge 52. Therefore, by removing the developing cartridge 52, the inside of the optical path chamber 56 is exposed to the outside. It is also configured so that dust and toner attached to the shutter member 64 or collected in the collection pocket 66 can be easily cleaned.

FIG. 3 is a perspective view showing the entirety of the middle plate 50 provided between the raster scanning unit 40 and each of the image forming engines 10Y, 10M, 10C and 10Bk.
As shown in this figure, the image forming engines 10Y, 10M, 10C,
Four laser beam entrances 53 are formed corresponding to 10 Bk, and the above-described substantially triangular partition walls 60 and 61 are provided upright on the front side and the rear side of the entrance 53. The shutter member 64 is provided so as to be sandwiched between the front and rear partition walls 60, 61, and is configured to swing about an axis supported by the partition walls 60, 61. .
On the front side of the middle plate 50, a plate-shaped shutter opening / closing arm 70 is provided along the arrangement direction of the four imaging engines 10Y, 10M, 10C, and 10Bk.
When the arm 70 is pulled toward the black imaging engine 10Bk by the solenoid 71 as a driving means, that is, in the direction of the arrow A in the drawing, the arm 70 is provided for each of the imaging engines 10Y, 10M, 10C, and 10Bk. All of the four shutter members 64 thus opened simultaneously allow the exposure of the photosensitive drum 11 with the laser beam Bm. Similarly, when the shutter opening / closing arm 70 is pushed in the direction opposite to the direction of arrow A in the figure, all the shutter members 64 are simultaneously closed, and the seal glass 44 of the raster scanning unit 40 is moved to the image forming engines 10Y and 10M. , 10
C and 10Bk.

FIG. 4 is a perspective view showing the relationship between the shutter opening / closing arm 70 and the solenoid 71. A notch 72 is provided at the tip of the shutter opening / closing arm 70 on the side of the black image forming engine 10Bk, and a drive arm 73 is engaged with the notch 72. The drive arm 73 is swingably held about a support shaft 74, one end of which is engaged with the reciprocating arm 75 of the solenoid 71, and the other end of which is engaged with the shutter opening / closing arm 70 as described above. Therefore, by turning on / off the solenoid 71, the drive arm 73 swings about the support shaft 74, and the shutter opening / closing arm 70 moves forward and backward accordingly. FIG. 4 shows that the shutter member 64 has the laser beam Bm.
3 shows a state in which the optical path is closed.

FIG. 5 is a perspective view showing a connecting portion between the shutter opening / closing arm 70 and the shutter member 64. A notch 76 is formed in the shutter opening / closing arm 70 at a position adjacent to each partition wall 60.
The connection piece 78 erected on the support shaft 77 of the notch 4
6 is fitted. Therefore, the shutter opening / closing arm 70
When the is moved forward and backward, the connecting piece 78 is pushed and pulled, and the shutter member 64 is opened and closed accordingly. Particularly, in the printer of this embodiment, the connecting piece 78 is formed of a resin film in order to surely open and close all the shutter members 64. For example, when the shutter opening / closing arm 70 is pulled toward the black image forming engine 10Bk to open all the shutter members 64, if there is a formation error of the notch 76 with respect to the shutter opening / closing arm 70, etc. Even if one of the shutter members 64 is completely opened, the other shutter members 64 may not be completely opened. When such a situation occurs, the laser beam Bm for exposing the photosensitive drum 11 is opened halfway.
4, and the image forming engine cannot form a toner image.
However, if an elastic member such as a flexible resin film is used as the connection piece 78, the resin film bends to absorb an extra stroke of the shutter opening / closing arm 70. Even if the shutter member 64 is fully opened, the remaining shutter member 64 can be completely opened by further moving the shutter opening / closing arm 70.

In the tandem-type color laser beam printer of the present embodiment configured as described above, the four color laser beam printers provided on the middle plate 50 corresponding to the respective image forming engines 10Y, 10M, 10C and 10Bk. Since the shutter member 64 is opened and closed by one driving means 71, the shutter member 64 can be opened and closed with a compact configuration, and the space in the printer can be effectively utilized to reduce the size of the printer. Is possible. Further, by using the elastic member 78 at the connecting portion between the shutter opening / closing arm 70 and the shutter member 64, even though all the shutter members 64 are opened and closed by the single driving means 71, these shutter members 64 are opened and closed. Can be completely opened or closed, and troubles such as interruption of the laser beam Bm by the half-open shutter member 64 do not occur.

[0031]

As described above, according to the color image forming apparatus of the present invention, all shutter members provided for each image forming engine are simultaneously opened and closed by driving one opening and closing arm. Accordingly, the laser beam irradiation port of the raster scanning unit can be appropriately shielded from each image forming engine, so that it is not necessary to provide a mechanism for opening and closing a shutter member for each image forming engine. It is possible to achieve miniaturization and cost reduction while preventing adhesion of dust and toner to the seal glass.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a tandem type color laser beam printer to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a structure between an image forming engine and a raster scanning unit according to the embodiment.

FIG. 3 is a perspective view showing a middle plate according to the embodiment.

FIG. 4 is a perspective view showing a combined state of a shutter opening / closing arm according to the embodiment and a solenoid for driving the arm.

FIG. 5 is a perspective view showing a connection state between a shutter opening / closing arm and a shutter member according to the embodiment.

[Explanation of symbols]

10Y, 10M, 10C, 10Bk ... imaging engine, 4
0: raster scanning unit, 54, 55: optical path forming plate, 6
4 shutter member, 70 shutter opening / closing arm, B
m ... Laser beam

Claims (5)

[Claims] 1. A raster scanning unit for emitting a laser beam modulated by image information, and a plurality of image forming engines having a photosensitive drum exposed by the laser beam and forming a toner image corresponding to the image information. A color image forming apparatus that forms a color recorded image by multiplex-transferring toner images formed by the respective image forming engines onto a recording sheet, wherein the laser beam is provided between each image forming engine and a raster scanning unit. A pair of optical path forming plates are provided in parallel with the axial direction of the photosensitive drum with the optical path therebetween, and the laser beam irradiation port of the raster scanning unit is formed between the optical path forming plates by appropriately advancing to the optical path. A shutter member is provided to shield the shutter members, and a shutter opening / closing arm connected to all shutter members is provided. The color image forming apparatus characterized by being configured so as to simultaneously open and close all of the shutter member by driving the shutter opening and closing arm. 2. The color image forming apparatus according to claim 1, wherein the shutter opening / closing arm and the shutter member are connected via an elastic member. 3. The color image forming apparatus according to claim 1, wherein when the shutter member blocks an optical path of the laser beam, a tip of the shutter member is elastically pressed against the optical path forming plate. apparatus. 4. According to the opening and closing operation of the shutter member,
2. The color image forming apparatus according to claim 1, further comprising a collection pocket for storing dust adhering to a surface of the shutter member facing the image forming engine. 5. The color image forming apparatus according to claim 1, wherein at least one of the pair of optical path forming plates facing each other with the optical path of the laser beam interposed therebetween is detachably provided. apparatus.