JPH10235933A - Laser scan unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser scan unit in which the size is reduced without causing color shift in the image to be formed on a sheet or troublesome processing of an image data. SOLUTION: An LSU 30 comprises laser light sources 70-73, polygon mirrors 31-34, polygon motors 35-38, reflectors 39-50, fθlenses 51-54 and cylindrical lenses 55-58, all of which are held integrally in a housing 59. Two polygon motors 35, 36 out of the polygon motors 35-38 are disposed vertically in two stages at a position shifted to the right side of the housing 59. Other two polygon motors 37, 38 are disposed vertically in two stages at a position shifted slightly to the left side from the center of the housing 59. At the time of forming an image, laser beams Lb, Lm, Lc, Ly generated from the laser light sources 70-73 are reflected on the polygon mirrors 31-34 turning in same direction at high speed and advance in leftward direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanning unit provided in a color image forming apparatus such as a laser color printer for irradiating a surface of a photoreceptor with a laser beam to form an electrostatic latent image. .

[0002]

2. Description of the Related Art Conventionally, four photosensitive drums for black, magenta, cyan and yellow have been arranged along a linear transport path formed by a transport belt.
A so-called tandem-type full-color printer is known in which a full-color image is obtained by sequentially superimposing and transferring each color toner image formed on the surface of each photosensitive drum onto the paper while transporting the paper by a transport belt. . FIG. 6 shows an example of a typical internal configuration of the tandem type printer.

Referring to FIG. 6, a photosensitive drum 101 for cyan, a photosensitive drum 102 for magenta, a photosensitive drum 103 for yellow, and a photosensitive drum for black are provided above a transport belt 100 whose upper surface forms a transport path of a sheet. Body drum 10
4 are arranged in this order along the sheet transport direction.
Above the photosensitive drums 101, 102, 103, and 104, a laser scanning unit 105 that generates a laser beam modulated in accordance with image data of each color is provided. The laser scanning unit 105 includes four laser scan units 106 and 107, which are respectively associated with the photosensitive drum 101 for cyan, the photosensitive drum 102 for magenta, the photosensitive drum 103 for yellow, and the photosensitive drum 104 for black. 108 and 109 are provided.

In forming an image, the surface of the photosensitive drum 101 for cyan is uniformly charged by a charger (not shown), and then the laser scan unit 10 for cyan is used.
6 is exposed by the laser beam. As a result, an electrostatic latent image corresponding to the cyan image data is formed on the surface of the photosensitive drum 101. The formed electrostatic latent image is visualized with cyan toner to become a cyan toner image, and is transferred onto a sheet conveyed by the conveyance belt 100.

Similarly, the magenta photosensitive drum 10
2. On the yellow photosensitive drum 103 and the black photosensitive drum 104, toner images corresponding to magenta, yellow and black image data are formed. The full-color image is formed by sequentially transferring the formed toner images of the respective colors on the paper on which the cyan toner image has been transferred in a superimposed manner.

[0006]

In the printer shown in FIG. 6, four laser scan units 106,
Since the 107, 108, and 109 are arranged in a line along the sheet conveyance direction, the width H of the laser scanning unit 105 in the left-right direction in FIG. 6 increases, and there is a problem that the printer body becomes large. .

In order to solve this problem, a printer having an integrated laser scanning unit is disclosed in, for example, Japanese Patent Publication No. 8-5223. FIG. 7 shows a schematic configuration of this printer. Referring to FIG. 7, a laser scanning unit 110 includes two polygon mirrors 111 and 1 for scanning a laser beam from a laser light source (not shown).
12 are provided. During image formation, the two polygon mirrors 111 and 112 are rotated at high speed by one polygon motor 113.

For example, when a laser beam Lc corresponding to cyan image data is generated from a laser light source (not shown), this laser beam Lc is reflected by a polygon mirror 111 in the direction of an arrow 122 and is reflected by a reflecting mirror 114 for cyan. It is guided to the photosensitive drum 115. The laser beam Lm corresponding to the magenta image data is reflected by the polygon mirror 112 in the direction of arrow 122,
The light is guided to the magenta photosensitive drum 117 by the reflecting mirror 116.

On the other hand, the laser beam Ly corresponding to the yellow image data is reflected by the polygon mirror 112 in the direction of the arrow 123, the optical path is bent by the reflecting mirror 118, and is irradiated on the yellow photosensitive drum 119. The laser beam Lb corresponding to the black image data is reflected in the direction of arrow 123 by the polygon mirror 111, and is guided to the black photosensitive drum 121 by the reflecting mirror 120.

As described above, in the apparatus shown in FIG. 7, the polygon mirror 111 deflects the laser beam Lc and the laser beam Lb in opposite directions, and the polygon mirror 112 deflects the laser beam Lm and the laser beam Lb.
The laser scanning unit 110 is downsized by deflecting y in directions opposite to each other. However, FIG.
As shown by arrows 124 to 127 in FIG.
And the scanning direction of the laser beam Lm and the laser beam Ly
Since the scanning direction of the laser beam Lb is opposite to the scanning direction of the laser beam Lb, there is a large possibility that the position of the electrostatic latent image formed on the surface of each photosensitive drum is shifted. That is, for example, the ambient temperature changes and the reflecting mirrors 114, 116, 1
When similar distortion occurs in optical members such as 18 and 120, the formation positions of the electrostatic latent images formed on the photosensitive drums 115 for cyan and magenta and the photosensitive drums 119 for yellow and black The formation position of the electrostatic latent image formed on the photosensitive drum 121 for use is shifted in the opposite direction. Such a shift in the formation position of the electrostatic latent image is not preferable because it appears as a transfer shift (color shift) between the toner images of the respective colors when the toner images of the respective colors are transferred onto a sheet in a superimposed manner.

Further, if the scanning direction of the laser beam Lc and the laser beam Lm is set to the forward direction with respect to the input order of the image data to the laser scanning unit 110, the scanning direction of the laser beam Ly and the laser beam Lb is reversed. Becomes Therefore, with respect to the yellow and black image data, the image data is temporarily stored in a buffer capable of storing at least one scan line of image data, and then the stored image data is read out for each line in reverse order. Need to give to the light source. Therefore, data processing becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems, and to achieve a small-sized laser without causing color misregistration in an image formed on paper and without complicating data processing. It is to provide a scanning unit.

[0013]

According to a first aspect of the present invention, there is provided a laser scanning unit which irradiates a laser beam modulated in accordance with image data onto a surface of a photosensitive member. A laser scanning unit for forming an electrostatic latent image on a surface, comprising: a laser light source for generating at least three laser beams; and a polygon provided with the same number of laser beams for scanning at least three laser beams. A mirror, an optical member for guiding the laser beam scanned by the polygon mirror to the photoreceptor surface, a mounting frame for integrally holding the laser light source, the polygon mirror and the optical member, and the at least three laser beams. In order to scan in the same direction with each other by polygon mirrors provided as many as the number of laser beams,
Means for rotating and driving the polygon mirror.

According to the first aspect of the present invention, the laser scan unit is integrally formed by holding each member such as a polygon mirror by the mounting frame, so that the laser scan unit is independent for each laser beam. Compared with a configuration in which three or more laser scan units are arranged in a line, the space of the laser scan unit can be significantly reduced.

Further, since the laser scanning unit is integrally formed, the mounting position of the optical member is adjusted so that a good laser beam is irradiated on the photosensitive member.
If this laser scan unit is incorporated in the image forming apparatus, it is not necessary to readjust the irradiation direction of the laser beam at the time of assembling. Therefore, no labor is required for assembling the image forming apparatus.

Further, since the laser beams emitted from the laser light source are scanned in the same direction, there is little possibility that the position of the electrostatic latent image formed on the surface of the photosensitive drum is shifted. Therefore, the possibility that color misregistration occurs in the image formed on the paper is reduced. Further, since the scanning directions of the laser beams are all the same, there is no need to change the input order of the image data to the laser scanning unit, and the data processing does not become complicated.

According to a second aspect of the present invention, at least two of the polygon mirrors provided in the same number as the number of the laser beams are arranged side by side in the direction of the rotation axis of the polygon mirror. Item 4 is a laser scan unit according to Item 1. According to the second aspect of the present invention, the width of the laser scan unit can be reduced by disposing the at least two polygon motors side by side in the direction of the rotation axis of the polygon mirror.

According to a third aspect of the present invention, in the laser scanning apparatus according to the second aspect, the side-by-side polygon mirrors are commonly mounted on a rotation shaft driven by one polygon motor. Unit.
According to the third aspect of the present invention, the polygon mirrors arranged side by side are commonly attached to the rotating shaft driven by one polygon motor, so that a polygon motor is provided for each polygon mirror. Thus, the number of polygon motors can be reduced. Therefore, the number of components of the laser scan unit can be reduced, and the unit can be further downsized.

Further, since the control for synchronizing the rotations of the polygon mirrors mounted on the common rotating shaft is not required, the polygon motors are not required to be provided as compared with the configuration in which a polygon motor is provided for each polygon mirror. Control can be simplified.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing the internal configuration of a digital full-color printer provided with a laser scan unit according to the present invention. This digital full-color printer includes four image forming units 10B, 10M, 10C, 1 for black, magenta, cyan, and yellow along a linear paper transport path formed by the upper surface of the transport belt 20.
0Y (hereinafter, collectively referred to as “image forming unit 1
0 ". ) Are arranged in a line, and a toner image formed by each image forming unit is sequentially superimposed on the paper P and transferred while the paper P is being transported by the transport belt 20, so that a full-color image is obtained. Is a full-color printer.

More specifically, the conveyor belt 20
An endless belt wrapped around the driving roller 22 and the driven roller 21, and is disposed substantially at the center of the printer. Below the transport belt 20, a plurality of sheets P
Is provided with a sheet feeding tray 3 capable of storing the sheet. In connection with the paper feed tray 3, a paper feed roller 5 for feeding out the paper P from the paper feed tray 3 to the paper supply path 4 one by one is provided.

When the paper feed roller 5 is rotated, the paper P becomes 1
The sheets are separated one by one and sent out from the sheet feed tray 3 onto the sheet supply path 4. Paper P sent out on paper supply path 4
Is transported by the transport roller 6 toward the registration roller 7. Then, after being temporarily stopped by the registration roller 7, the toner image is sent out onto the transport belt 20 at the same timing as the toner image forming operation (described later) in the black image forming unit 10 </ b> B.

Above the transport belt 20, a black image forming unit 10B and a magenta image forming unit 1
0M, the cyan image forming unit 10C, and the yellow image forming unit 10Y are arranged in this order along the transport direction of the paper P. Further, the image forming unit 1
Above 0, a laser scan unit 30 (hereinafter, referred to as “LSU 30”) for generating a laser beam based on image data input from an external device such as a personal computer is arranged.

Image data input from an external device is first input to an image processing unit (not shown), and is decomposed into color image data representing the densities of black, magenta, cyan, and yellow. When the obtained color image data of each color is input to the LSU 30, the laser beams Lb, Lb, which are modulated based on the color image data,
Lm, Lc, and Ly are the image forming units 10 respectively.
B, 10M, 10C, and 10Y are emitted.

The black image forming unit 10B includes:
A photosensitive drum 11B is provided which rotates at a constant speed in the direction of an arrow (clockwise in FIG. 1) during image formation.
The photoreceptor drum 11B is horizontally disposed such that its rotation axis is along a direction orthogonal to the sheet conveyance direction. Further, around the photosensitive drum 11B, the photosensitive drum 11
In order along the rotation direction of B, the main charger 12B,
A black developing device 13B and a cleaner 14B are arranged. The laser beam Lb from the LSU 30 irradiates the surface of the photosensitive drum 11B between the main charger 12B and the black developing device 13B, and
The surface of B is scanned along its axial direction.

In forming an image, the photosensitive drum 11B
Is charged to a uniform predetermined potential by the discharge of the main charger 12B, and is then exposed to the laser beam Lb from the LSU 30. Then, the charged charges in the exposed portion escape and the surface of the photosensitive drum 11B is
A portion having a high potential and a portion having a low potential are generated, and a so-called electrostatic latent image is formed.

Photosensitive drum 11B on which an electrostatic latent image is formed
Next, the black toner is attached to a portion having a low potential, facing the black developing device 13B. More specifically, the black developing device 13B includes a developing roller 15 and a sub-roller 16. Further, in the black developing device 13B, non-magnetic one-component black toner is stored, and when the developing roller 15 and the sub-roller 16 are respectively rotated in predetermined directions,
The toner is charged by friction between the developing roller 15 and the sub-roller 16 and mainly adheres to the surface of the developing roller 15. At this time, the rotation of the sub-roller 16 plays a role of helping the toner to adhere to the surface of the developing roller 15.

The developing roller 15 having the toner layer formed thereon is
The photosensitive drum 11B is rotated at a speed higher than the peripheral speed of the photosensitive drum 11B so that the toner layer contacts the surface of the photosensitive drum 11B. A predetermined voltage is applied to the developing roller 15, and the potential of the developing roller 15 is lower than the potential of the unexposed portion of the photosensitive drum 11B and higher than the potential of the exposed portion. . Therefore, when the photosensitive drum 11B comes into contact with the toner layer on the developing roller 15, the charged toner on the developing roller 15 is transferred to the photosensitive drum 11B.
The process moves to the exposure portion B (low potential portion), and the electrostatic latent image on the photosensitive drum 11B is visualized as a toner image.

When the photosensitive drum 11B is further rotated, the black toner image formed on the surface of the photosensitive drum 11B faces the transfer roller 50B provided below the upper conveyor belt 20. On the other hand, the registration roller 7 is driven to rotate at a timing synchronized with the timing at which the black toner image faces the black transfer roller 50 </ b> B, and the paper P is fed by the transport belt 20. A predetermined voltage is applied to the black transfer roller 50B,
The black toner on the surface of the photosensitive drum 11B is drawn to the black transfer roller 50B and moves to the upper surface of the sheet P. As a result, the black toner image is transferred onto the paper P. The toner remaining on the surface of the photosensitive drum 11B after the transfer is collected by the cleaner 14B.

The paper P on which the black toner image has been transferred in this manner is transported by the transport belt 20 to the magenta image forming unit 10M. The magenta image forming unit 10M includes a photosensitive drum 11M provided in parallel with the photosensitive drum 11B, a main charger 12M, a magenta developing device 13M, and a cleaner 14M.
Is provided. The laser beam Lm output from the LSU 30 irradiates the surface of the photosensitive drum 11M between the main charger 12M and the magenta developing device 13M, and scans the surface of the photosensitive drum 11M along the axial direction. ing.

A magenta toner image is formed on the surface of the photosensitive drum 11M through the same process as in the case of black. The magenta toner image is transferred onto the paper P on which the black toner image has been transferred by the action of the magenta transfer roller 50M facing the photosensitive drum 11M with the upper conveyor belt 20 interposed therebetween. The sheet P after the transfer is transported by the transport belt 20 to the cyan image forming unit 10C.

The image forming unit 10C for cyan includes a photosensitive drum 11C provided in parallel with the photosensitive drums 11B and 11M, a main charger 12C, a cyan developing device 13C, and a cleaner 14C. LSU
The laser beam Lc output from 30 is applied to the surface of the photosensitive drum 11C between the main charger 12C and the cyan developing device 13C, and scans the surface of the photosensitive drum 11C along its axial direction. ing.

A cyan toner image is formed on the surface of the photosensitive drum 11C through the same process as in the case of black. The formed cyan toner image is transferred onto the paper P on which the black and magenta toner images have been transferred by the action of the cyan transfer roller 50C facing the photosensitive drum 11C with the transport belt 20 interposed therebetween.
The sheet P after the transfer is transported by the transport belt 20 toward the yellow image forming unit 10Y.

In the yellow image forming unit 10Y,
A photoconductor drum 11Y, a main charger 12Y, a yellow developing device 13Y, and a cleaner 14Y are provided in parallel with the photoconductor drums 11B, 11M, and 11C. The laser beam Ly output from the LSU 30 is
The surface of the photoconductor drum 11Y between the main charger 12Y and the yellow developing device 13Y is irradiated to scan the surface of the photoconductor drum 11Y along its axial direction.

A yellow toner image is formed on the surface of the photosensitive drum 11Y through the same process as in the case of black. This toner image is transferred to the yellow transfer roller 5 that faces the photosensitive drum 11Y with the conveyance belt 20 interposed therebetween.
By the function of 0Y, the cyan toner image is transferred onto the sheet P on which the cyan toner image has been transferred. The sheet P on which the toner images of the respective colors are transferred in an overlapping manner in this manner is separated from the separation charger 1.
7, the sheet is separated from the conveyor belt 20 by the discharge and is guided to the fixing unit 80. The fixing unit 80 has a heat fixing belt 83 wound around two rollers 81 and 82.
And a heat roller 8 for heating the heat fixing belt 83.
4 and a lower roller 8 provided below the heat fixing belt 83.
5 are provided. The sheet P conveyed toward the fixing unit 80 enters between the heat fixing belt 83 and the lower roller 85, is pressed, and is heated by the heat fixing belt 83. Thereby, the paper P
The upper color toners are fixed on the paper P. The paper P after the fixing process is discharged by discharge rollers 8 and 9 to a discharge section 18 formed on the upper surface of the printer main body 2.

The above is one cycle of the image forming operation when a full-color image is formed on the paper P. FIG.
FIG. 2 is a cross-sectional view showing a simplified configuration of the LSU 30.
In the following description, the state shown in FIG. 2, LSU 30 includes four laser light sources 70 to 73 conceptually shown in FIG.
, Four polygon mirrors 31 to 34, four polygon motors 35 to 38, and a plurality of optical members including reflecting mirrors 39 to 50, fθ lenses 51 to 54, and cylindrical lenses 55 to 58. These members are respectively mounted at predetermined positions in a housing 59 as a mounting frame, and are integrally held and housed by the housing 59.

Of the four polygon motors 35 to 38,
The two polygon motors 35 and 36 are arranged in a position deviated to the right of the housing 59 so as to be overlapped in two stages at predetermined intervals in the vertical direction. The other two polygon motors 3
The reference numerals 7 and 38 are arranged at a position slightly to the left of the center of the housing 59 at predetermined intervals in the up-down direction so as to be stacked in two stages.

Further, four polygon motors 35 to 38 are provided.
Is provided in a state where the respective rotating shafts 60 to 63 extend upward. Rotation axis 6 of polygon motor 35
0, a polygon mirror 32 is attached, and a rotation axis 61 of the polygon motor 36 is attached to the polygon mirror 3.
1 is attached. The polygon mirror 34 is attached to the rotating shaft 62 of the polygon motor 37, and the polygon mirror 33 is attached to the rotating shaft 63 of the polygon motor 38. During image formation, the polygon motors 35 to 38 are rotated at high speed in the same direction at the same speed, and the polygon mirrors 31 to 34 are rotated at high speed in the same direction.

When black color image data is input to the LSU 30, a laser beam Lb modulated based on the color image data is emitted from the black laser light source 70 toward the black polygon mirror 31.
The laser beam Lb is scanned by being reflected by the polygon mirror 31 rotating at a high speed. The scanned laser beam Lb proceeds to the left and enters the fθ lens 51. The laser beam Lb that has passed through the fθ lens 51 travels rightward after its optical path is turned back by the reflecting mirrors 39 and 40. Then, the optical path is bent downward by the reflecting mirror 41, and after passing through the cylindrical lens 55, is irradiated on the surface of the black photosensitive drum 11B. The cylindrical lens 55 is for shaping the laser beam Lb to form a small beam spot on the surface of the photosensitive drum 11B.

The laser beam Lm emitted from the magenta laser light source 71 is scanned by being reflected by a high-speed rotating magenta polygon mirror 32. The scanned laser beam Lm proceeds to the left and is guided to the reflecting mirror 42 via the fθ lens 52. The laser beam Lm guided to the reflecting mirror 42 is
The optical path is turned back by 43 and proceeds rightward. Then, the light path is bent downward by the reflecting mirror 44, and after passing through the cylindrical lens 56, the light is irradiated on the surface of the magenta photosensitive drum 11M.

Further, the laser beam Lc emitted from the cyan laser light source 72 is scanned by the cyan polygon mirror 33 and proceeds to the left. The laser beam Lc from the polygon mirror 33 is
Is guided to the reflecting mirror 45 through the optical path, and the optical path is turned back by the reflecting mirrors 45 and 46 to travel rightward. Then, after the optical path is bent downward by the reflecting mirror 47 and passes through the cylindrical lens 57, the photosensitive drum 11 for cyan
The surface of C is irradiated.

The laser beam Ly emitted from the yellow laser light source 73 is scanned by the yellow polygon mirror 34 and travels to the left. The laser beam from the polygon mirror 34 is guided to the reflecting mirror 48 via the fθ lens 54, and the optical path is turned back by the reflecting mirrors 48 and 49, and travels rightward. Then, after the optical path is bent downward by the reflecting mirror 50 and passes through the cylindrical lens 58, the yellow photosensitive drum 11
The surface of Y is irradiated.

As described above, the laser beams Lb, Lm, Lc, Ly generated from the laser light sources 70 to 73 are respectively reflected by the polygon mirrors 31 to 34 rotating at high speed in the same direction, and travel leftward in FIG. I do. Therefore, the beam spots formed by the laser beams Lb, Lm, Lc, Ly on the surfaces of the photoconductor drums 11B, 11M, 11C, 11Y form the photoconductor drums 11B, 11M, 11Y.
The surfaces of 11C and 11Y are scanned in the same direction along each axial direction. Therefore, there is little possibility that the positions of the respective electrostatic latent images for black, magenta, cyan and yellow formed on the surface of the photosensitive drum are shifted.

This is because when the optical members such as the fθ lenses 51 to 54 and the cylindrical lenses 55 to 58 are distorted, the photosensitive drums 11B, 11M, 11C, 11Y
This is because the electrostatic latent image formed on the surface of the image is displaced in the same direction. If the scanning direction of the laser beam Lb and the scanning direction of the laser beam Lc are opposite, for example, the electrostatic latent image formed on the photosensitive drum 11B and the electrostatic latent image formed on the photosensitive drum 11C However, there is a possibility that positional shifts occur in opposite directions, and noticeable color shift occurs in an image formed on a sheet. Therefore, according to this embodiment, there is less possibility that color misregistration occurs in an image formed on a sheet as compared with the configuration shown in FIG.

The laser beams Lb, Lm, Lc, L
Since the scanning directions of y are all the same, there is no need to change the input order of the image data to the laser scan unit 30, and the control of the image processing unit does not become complicated. Further, the polygon motors 35 and 36 (polygon mirrors 31 and 32) are arranged in two upper and lower stages at positions deviated to the right of the housing 59, and the polygon motors 37 and 38 (polygon mirrors 33 and 34) are positioned at the center of the housing 59. Since the laser scanning unit 105 is disposed on the left side of the laser scanning unit 105 at a slightly upper left position, the width of the laser scanning unit 30 in the left-right direction (photosensitive drum 11B, 11M, 11C and 11Y) can be configured to be small. That is, the optical path of the laser beam Lb and the optical path of the laser beam Lm are superimposed on each other, and the optical path of the laser beam Lc and the laser beam Lm are overlapped.
Since the optical path of y is vertically overlapped, the width along the irradiation direction of the laser beam after being reflected by the polygon mirrors 31 to 34 of the laser scan unit 30 can be reduced.

In the case where the four laser scan units 106 to 109 are independently configured as shown in FIG. 6, before the laser scan units 106 to 109 are incorporated into the printer main body, color shift or the like may occur in the image. It is necessary to adjust the position of the optical member for each of the laser scan units 106 to 109 so as to obtain a good laser beam which does not cause the laser beam. In addition, when installing the laser scan units 106 to 109 in the printer main body, it is necessary to adjust the mounting positions of the laser scan units 106 to 109 so that the laser beams irradiated to the photosensitive drums 101 to 104 are parallel to each other. There is also. That is, in order to prevent color misregistration, the work of adjusting the mounting position of the optical member and the operation of each of the laser scan units 106 to
The work of adjusting the mounting position of the printer 9 is required, and the work of assembling the printer body is troublesome.

However, according to this embodiment, the LSU
If the mounting positions of the above optical members are adjusted so that good laser beams Lb, Lm, Lc, Ly are obtained before the LSU 30 is incorporated into the printer body, the LSU 30 can be assembled into the printer body. It is not necessary to perform the complicated adjustment work as described above. Therefore, the labor required for assembling the printer body is reduced.

FIG. 3 is a sectional view schematically showing the configuration of the LSU according to the second embodiment. The LSU 30a according to the second embodiment is to be used in place of the LSU 30 in FIG. In FIG. 3,
Portions equivalent to those shown in FIG. 2 are denoted by the same reference numerals. In the following description, differences from the LSU 30 according to the above-described first embodiment will be particularly described.

In the LSU 30 according to the above-described first embodiment, the four polygon motors 35 to 38 are provided in a state where the respective rotating shafts 60 to 63 extend upward. However, the LSU 30 according to the second embodiment
In a, the polygon motors 35 and 37 are provided in a state where the respective rotating shafts 60 and 62 extend downward. That is, the polygon motors 35 and 37 are provided above the polygon motors 36 and 38, respectively.
0 and 62 are arranged to face the polygon mirrors 31 and 33, respectively.

Therefore, when the polygon motors 35 to 38 are all rotated in the same direction, the polygon mirrors 31,
33 and the polygon mirrors 32 and 34 rotate in opposite directions, and the laser beams Lb and Lc
And the scanning directions of the laser beams Lm and Ly are opposite to each other. Therefore, in the second embodiment, the polygon motors 35 and 37 are driven to rotate at the same speed in the opposite direction to the polygon motors 36 and 38. As a result, since the rotation directions of the polygon mirrors 31 to 34 are all the same, the scanning directions of the four laser beams Lb, Lm, Lc, Ly are the same, and the same operation as the LSU 30 according to the above-described first embodiment. The effect can be achieved.

FIG. 4 is a simplified sectional view showing the configuration of the LSU according to the third embodiment. The LSU 30b according to the third embodiment is to be used instead of the LSU 30 in FIG. In FIG. 4,
Parts equivalent to those shown in FIG. 2 are denoted by the same reference numerals. LSU3 according to the third embodiment
In FIG. 0b, the polygon motors 35 and 36 are arranged in a vertically deflected position on the right side of the housing 59 in two vertical stages. The polygon motor 35 is provided in a state where the rotating shaft 60 extends downward. The polygon motor 36 is provided in a state where the rotating shaft 61 extends upward. At the time of image formation, when the rotation direction of the polygon motor 36 is set to the forward direction, the polygon motor 35 is rotated in the reverse direction, and the polygon mirror 31 and the polygon mirror 32 are rotated in the same direction. Thereby, the laser beams Lb and Lm are respectively transmitted to the polygon mirrors 31 and 32.
Are scanned in the same direction by the polygon mirror 31,
Go left 32.

On the other hand, the polygon motors 37 and 38 are arranged in two upper and lower stages at positions deviated to the left side of the housing 59. The polygon motor 37 is provided with the rotating shaft 62 extending upward, and the polygon motor 38 is provided with the rotating shaft 63 extending downward. The laser beams Lc and Ly scanned by the polygon mirrors 33 and 34 travel rightward from the polygon mirrors 33 and 34, respectively.

During image formation, when the rotation direction of the polygon motor 36 is set to the forward direction, the polygon motor 37 is rotated in the reverse direction, and the polygon motor 38 is rotated in the forward direction. As a result, the polygon mirror 33 and the polygon mirror 34 are rotated in a direction opposite to that of the polygon mirror 31. Therefore, the scanning direction of the laser beams Lc and Ly traveling rightward from the polygon mirrors 33 and 34 coincides with the scanning direction of the laser beam Lb.

As described above, also in the configuration of the third embodiment, since the scanning directions of the four laser beams Lb, Lm, Lc, and Ly are the same, the same operation and effect as those of the first embodiment are provided. be able to. FIG. 5 is a cross-sectional view schematically showing a characteristic portion of the configuration of the LSU according to the fourth embodiment. LSU 30c according to the fourth embodiment
Is to be used instead of the LSU 30 in FIG. In FIG. 5, the same parts as those shown in FIG. 2 are denoted by the same reference numerals.

In the above-described first embodiment, the polygon mirror 31 and the polygon mirror 32 are rotated in the same direction, and the polygon mirror 33 and the polygon mirror 34 are rotated in the same direction. Focusing on this point, in the LSU 30c according to the fourth embodiment, the upper polygon motor 35
Are omitted, and the polygon mirror 31 and the polygon mirror 32 are attached to the rotating shaft 61 of the polygon motor 36. The polygon motor 37 is omitted, and the polygon mirror 33 and the polygon mirror 34 are attached to the rotation shaft 63 of the polygon motor 38.

According to this configuration, since only two polygon motors are required, the width of the LSU 30c in the vertical direction can be reduced as compared with the LSU 30 according to the first embodiment. Also, a polygon mirror 31 and a polygon mirror 32
Are rotated by a common polygon motor 36 to rotate the polygon mirror 31 and the polygon mirror 32.
This eliminates the need for control for synchronizing the rotation with. Similarly, control for synchronizing the rotation of the polygon mirror 33 with the rotation of the polygon mirror 34 is not required. Therefore, the control of the polygon motor can be simplified as compared with the first to third embodiments.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above-described fourth embodiment, a configuration in which the polygon motor is omitted in the laser scan unit according to the first embodiment is described, but, of course, the laser scan units according to the second and third embodiments are used. Also, the polygon motor can be omitted.

In the fourth embodiment, a configuration in which both the polygon motors 35 and 37 are omitted has been described as an example. However, it is needless to say that a configuration in which only one of the polygon motors is omitted may be adopted. Good. Furthermore, in the above-described first to fourth embodiments, only the configuration in which the polygon mirror is attached to the rotation axis of the polygon motor has been described. However, the polygon mirror is attached to the rotation axis provided separately from the rotation axis of the polygon motor. It may be configured to be attached, and the separately provided rotating shaft is rotationally driven by a polygon motor.

In the first to third embodiments described above, the rotation axis 60 of the polygon motor 35 and the rotation axis 61 of the polygon motor 36 are provided on the same axis, and the rotation axis 62 of the polygon motor 37 is provided. And the rotating shaft 63 of the polygon motor 38 are provided on the same axis. However, the polygon motors 35 and 36 are not necessarily
0 and the rotating shaft 61 need not be provided so as to be located on the same axis, and may be provided shifted in the left-right direction. Similarly, the polygon motors 37 and 38 may be provided shifted in the left-right direction.

The arrangement of the reflecting mirror, the fθ lens, the cylindrical lens and the like is not limited to the positions shown in FIGS. 2 to 4, but can be changed as appropriate within a range where the optical path length of each laser beam is the same. Further, in the above-described first to fourth embodiments, the laser scan unit that generates four laser beams of black, magenta, cyan, and yellow has been described. For example, three laser beams of magenta, cyan, and yellow are generated. It is also possible to configure as a laser scan unit that performs the operation.

In the above description, the case where the laser scanning unit according to the present invention is provided in a tandem-type full-color printer is described as an example. It may be provided in a copying machine or the like. In addition, various changes can be made within the scope described in the claims.

[0062]

According to the first aspect of the present invention, since the laser scanning unit is integrally formed, three or more laser scanning units independent for each laser beam are arranged in a line. In comparison, the space for the laser scan unit can be significantly reduced.

Further, since the laser scanning unit is integrally formed, the mounting position of the optical member is adjusted so that a good laser beam is irradiated on the photosensitive member, and this laser scanning unit is mounted on the image forming apparatus. If incorporated, there is no need to readjust the irradiation direction of the laser beam or the like at the time of assembling. Therefore, no labor is required for assembling the image forming apparatus.

Further, since the scanning directions of the laser beams are all the same, there is little possibility that the position of the electrostatic latent image formed on the surface of the photosensitive drum is shifted. Therefore, the possibility that color misregistration occurs in the image formed on the paper is reduced. In addition, since the scanning directions of the laser beams are all the same, there is no need to change the input order of the image data to the laser scanning unit, and the data processing does not become complicated.

According to the second aspect of the present invention, the width of the laser scan unit can be reduced by disposing at least two polygon motors side by side in the direction of the rotation axis of the polygon mirror. According to the third aspect of the present invention, the number of polygon motors can be reduced as compared with a configuration in which a polygon motor is provided for each polygon mirror. Therefore, the size of the laser scan unit can be further reduced.

In the case of polygon mirrors mounted on a common rotating shaft, control for synchronizing the rotations of the polygon mirrors is not required. Control can be simplified.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view showing an internal configuration of a digital full-color printer provided with a laser scan unit according to the present invention.

FIG. 2 is a simplified cross-sectional view illustrating a configuration of a laser scan unit according to the first embodiment.

FIG. 3 is a simplified cross-sectional view illustrating a configuration of a laser scan unit according to a second embodiment.

FIG. 4 is a simplified cross-sectional view illustrating a configuration of a laser scan unit according to a third embodiment.

FIG. 5 is a simplified cross-sectional view showing a characteristic portion of a configuration of a laser scan unit according to a fourth embodiment.

FIG. 6 is a simplified cross-sectional view showing an example of a typical configuration of a conventional tandem-type full-color printer.

FIG. 7 is a perspective view showing another configuration example of a conventional tandem type full color printer.

[Explanation of symbols]

11B, 11M, 11C, 11Y Photoconductor drum 30, 30a, 30b, 30c Laser scan unit (LSU) 31-34 Polygon mirror 35-38 Polygon motor 39-50 Reflector 51-54 fθ lens 55-58 Cylindrical lens 59 Housing 70-73 laser light source

Claims (3)

[Claims] 1. A laser scanning unit for irradiating a surface of a photoreceptor with a laser beam modulated in accordance with image data to form an electrostatic latent image on the surface of the photoreceptor, comprising at least three lasers. A laser light source for generating a beam, a polygon mirror provided in the same number as the number of laser beams for scanning at least three laser beams, and an optical member for guiding the laser beam scanned by the polygon mirror to the photoreceptor surface. A mounting frame for integrally holding a laser light source, a polygon mirror, and an optical member; and the above-mentioned at least three laser beams being scanned in the same direction by polygon mirrors provided in the same number as the number of the laser beams. Means for rotationally driving the polygon mirror. 2. The laser scan according to claim 1, wherein at least two of the polygon mirrors provided in the same number as the number of the laser beams are arranged side by side in the direction of the rotation axis of the polygon mirror. unit. 3. The laser scanning unit according to claim 2, wherein said polygon mirrors arranged in parallel are commonly mounted on a rotating shaft driven to rotate by one polygon motor.