JP2002196271A - Optical scanner and image forming device equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use respective common devices for performing an electrophotographic process by respective stations provided on both sides of a light deflector. SOLUTION: Optical device groups 32 and 33 and optical device groups 34 and 35 are arranged on both sides of the light deflector 31, and all of the incident angles α1, α2, α3 and α4 of beams on photoreceptor drums 5A, 5B, 5C and 5D are made nearly equal. The respective groups 32, 33, 34 and 35 are arranged so that distances LP1 and LP4, and LP2 and LP3 from intersections where the extension lines L1, L2, L3 and L4 of the respective beams respectively cross with respective optical axes LS1, LS2, LS3 and LS4 from the deflector 31 to the center of rotation of the deflector 31 may be equal to each other. Thus, at least distances P1 and P3 equal and the angles α1 and α4 are nearly equal, so that an electrifying device and a developing device or the like for performing the electrophotographic process are made common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for forming a light spot on a photoreceptor by using beams respectively emitted from a plurality of laser light sources, and a laser printer, a digital copier, and the like provided with the same. The present invention relates to an image forming apparatus such as a laser fax.

[0002]

2. Description of the Related Art Conventionally, an optical scanning apparatus for forming a light spot on a photoreceptor by using beams respectively emitted from a plurality of laser light sources is described in, for example, JP-A-10-18187. There are things that are. The optical scanning device includes an exposure optical system support member that supports the first exposure optical system and the second exposure optical system in which the direction of incidence of the laser beam when incident on the surface to be scanned is set to be non-parallel, in a fixed state. Can move forward and backward with respect to each photoconductor,
It is supported so that its rotational position can be adjusted around an axis parallel to the sub-scanning direction and its rotational position can be adjusted around an axis parallel to the main scanning direction.

[0005] Further, as an optical scanning device which forms a light spot on a photosensitive member using beams respectively emitted by a plurality of laser light sources, there is, for example, one shown in FIG. This optical scanning device has one motor 100
The rotating polygon mirrors 101 and 102 are mounted on the rotating shaft in two stages, and four sets of optical element groups 103, 104, 105 and 106 are sandwiched between the four semiconductor laser units (not shown) and the rotating polygon mirrors 101 and 102. Are arranged, and the beams deflected by the rotating polygon mirrors 101 and 102 are turned back by the mirrors provided for each of the optical element groups, and the photoconductors 121, 122, 123 and 1 are turned back.
24 are scanned at a constant speed.

[0004]

However, in the former optical scanning device, since the incident angles of a plurality of laser beams with respect to the photosensitive member are not parallel to each other, an apparatus for performing an electrophotographic process around the photosensitive member in each station is used. However, it is difficult to achieve the same arrangement or to arrange them in the same arrangement, so that there is a disadvantage that the space in the charging device and the developing device is particularly restricted. Also, in the latter optical scanning device, as in the former optical scanning device, the angles of incidence of the plurality of beams on the plurality of photoconductors are not constant and differ from station to station. In order to prevent each device performing the electrophotographic process from being shut off, the arrangement and size of the charging device and the developing device are changed for each station, or the charging device and the developing device are entirely Or make it smaller,
It was necessary not to block the beam. For this reason, there is a risk that the cost increases, and when the charging device, the developing device, and the like are downsized, there is a problem of reliability due to the durability and the like. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and commonly uses respective devices that execute an electrophotographic process, such as a common charging device and a developing device, at respective stations allocated to both sides of an optical deflector. It is another object of the present invention to prevent such devices from intercepting a beam incident on a photosensitive member on the way even if the mounting postures are the same.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention deflects beams emitted from a plurality of laser light sources by an optical deflector, and a plurality of optical element groups each having a corresponding mirror. In an optical scanning device that forms light spots on a plurality of photoconductors for each beam, the plurality of optical element groups are respectively arranged on both sides around the optical deflector, and the respective optical element groups are arranged. The angles of incidence of the beams incident on the respective photoconductors from the mirrors are substantially equal, and the extension lines of the respective beams incident on the respective photoconductors intersect with the respective optical axes from the optical deflectors. The distance from the optical deflector to the center of rotation is such that the optical element groups are arranged such that the optical element groups allocated to both sides are equidistant from each other. That. An image forming apparatus provided with the optical scanning device, wherein n photoconductors are provided, and each of the plurality of optical element groups arranged on both sides around the optical deflector is located at an outermost position. Each of the mirrors of the optical element group is constituted by one piece, and the distance along the optical axis direction between the centers of the n adjacent photoconductors is P,
When the distance along the optical path from the rotation center of the optical deflector to the surface to be scanned of each photoconductor is L, (n-1) × P
It is preferable that the image forming apparatus be configured to satisfy the relationship of / 2 <L.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining an arrangement relationship of each component constituting an optical scanning device according to an embodiment of the present invention, and FIG. 2 is an overall configuration diagram showing an image forming apparatus provided with the optical scanning device. It is. The color small printer as the image forming apparatus shown in FIG. 2 is a four-drum full-color electrophotographic image forming apparatus, and includes four photoconductor units 2A, 2B, 2C and 2D in the apparatus main body 1. , Are detachably attached to the apparatus main body 1. In this small-sized printer, a transfer belt 3 is mounted at a substantially center in the apparatus main body 1 so as to be rotatable between a plurality of rollers in a direction indicated by an arrow A.

On the upper surface of the transfer belt 3 in FIG. 2, the photosensitive drums 5A, 5B, 5 provided in the four photosensitive units 2A, 2B, 2C, 2D, respectively.
C, 5D so that the photoconductor units 2A to 2D are in contact with each other.
2D is provided. Developing devices 10A to 10D that use different colors of toner are provided corresponding to the photoconductor units 2A to 2D.
An optical scanning device 6 is provided above the photoconductor units 2A to 2D.
, And a duplex unit 7 is provided below.
Further, the small printer is equipped with a reversing unit 8 for reversing and discharging the transfer paper P after image formation and transporting it to the duplex unit 7 on the left side of the apparatus main body 1 in FIG.

Between the transfer belt 3 and the reversing unit 8, there is provided a fixing device 9 for fixing the image of the transfer paper on which the image has been transferred. On the downstream side of the fixing device 9 in the transfer paper transport direction, a reverse transport path 20 is formed by branching, and the transfer paper P transported there is allowed to be discharged onto a paper discharge tray 26 by a paper discharge roller pair 25. . In the lower part of the apparatus main body 1, paper feed cassettes 11 and 12 capable of storing transfer paper P having different sizes in two upper and lower stages are provided, respectively. Further, a manual tray 1 is provided on the right side of the apparatus body 1.
3 can be opened and closed in the direction of arrow B,
By opening 3, manual paper can be fed from there.

The photoconductor units 2A to 2D are units having the same configuration. The photoconductor unit 2A forms an image corresponding to yellow, the photoconductor unit 2B forms an image corresponding to magenta, The photoconductor unit 2C forms an image corresponding to cyan, and the photoconductor unit 2D
Forms an image corresponding to the black color. Then, they are arranged at intervals in the transport direction of the transfer paper. Further, the photosensitive drums 5A to 5D include a drum drive timing belt and a drum drive pulley (both not shown).
And the like, are rotationally driven clockwise in FIG.

In this compact printer, when the image forming operation is started, each of the photosensitive drums 5A to 5D rotates clockwise in FIG. Then, each of the photosensitive drums 5A
5D are uniformly charged by the charging roller 14 of each charging device. Each of the photosensitive drums 5A to 5A
The surface of D is irradiated with laser light (beam) corresponding to each color image by the optical scanning device 6. Then, the latent images on the respective photosensitive drums 5A to 5D are transferred to the developing devices 10A and 10A.
The toner is developed by B, 10C and 10D with each color toner to form a four-color toner image.

On the other hand, the transfer paper P is fed from the selected paper feed tray in the paper feed cassette 11 or 12 by the separation paper feed unit 55 or 56, and is fed to the photosensitive unit 2A.
The registration roller pair 59 provided immediately before
At an accurate timing coincident with the toner image formed on each photoconductor drum 5, it is conveyed between the photoconductor drum 5 of the photoconductor unit 2 </ b> A and the transfer belt 3. At this time, the transfer paper P is charged to a positive polarity by the paper suction roller 58 disposed near the entrance of the transfer belt 3, and thereby is electrostatically attracted to the surface of the transfer belt 3. Then, while the transfer paper P is attracted to the transfer belt 3 and is conveyed in the same direction by the rotation of the transfer belt 3 in the direction of arrow A, the toner images of each color are sequentially formed on the upper surface in FIG. When the image is transferred and passes through the photoconductor unit 2D, a full-color toner image of four colors is formed.

The transfer paper P is fused and fixed by applying heat and pressure to the transfer paper P in a fixing device 9 and thereafter passes through a paper discharge system according to a designated mode, and is discharged to the upper portion of the apparatus main body. The sheet is inverted and discharged to the paper tray 26, or is straightly discharged from the fixing device 9 and passes through the inside of the reversing unit 8. Alternatively, when the double-sided image forming mode is selected, the sheet is fed back to the reversing conveyance path 54 in the reversing unit 8, is switched back, is conveyed to the double-sided unit 7, is re-fed from there, and is In the image forming unit provided with 2A to 2D, the image is discharged after an image is formed on the back surface. Thereafter, when an instruction to form two or more images is given, the above-described image forming process is repeated.

The optical scanning device 6 deflects beams emitted from a plurality of laser light sources (not shown) corresponding to respective colors of yellow, cyan, magenta, and black by an optical deflector 31 as shown in FIG. A plurality of optical element groups 32, 33, 34, and 35 each having a corresponding mirror form a light spot on each of the four photosensitive drums 5A, 5B, 5C, and 5D for each beam corresponding to each color image. It is a device to do. In the optical scanning device 6, the optical element groups 32, 33 and the optical element groups 34, 35 are arranged on both sides with the optical deflector 31 as a center, and the respective optical element groups 32, 33, 34 are arranged. , 35 from the mirrors 41, 42, 43, 44, respectively.
B, 5C, and 5D, the angles of incidence of the beams respectively incident on the photosensitive drums 5A, 5B, 5C, and 5D.
₁ , α ₂ , α ₃ , α ₄ are all substantially equal, and the extension lines L ₁ , L ₂ , L ₃ , L _{4 of} the respective beams incident on the respective photosensitive drums 5A, 5B, 5C, 5D are optically deflected. each optical axis _LS 1 from vessel _{31, LS 2, LS 3,} LS 4 and the distance LP ₁ and LP ₄ and LP ₂ and LP ₃ from the intersection which intersect each to the rotational center of the optical deflector 31, equidistant from each other Each of the optical element groups 32, 33, 34, 35 is shown in FIG.
It is arranged at the position shown in.

The optical scanning device 6 includes an optical housing 36.
An optical deflector 31 is disposed substantially at the center of the optical deflector 31. The optical deflector 31 has rotatable polygon mirrors 38 and 39 mounted on a rotating shaft of a polygon motor 37 in two upper and lower stages. In the optical housing 36, as described above, the optical element groups 32 and 35 and the optical element groups 33 and 34 are arranged on the left and right sides in FIG. The optical element group 32 includes a two-layer fθ lens (imaging lens) 45, an imaging lens 46, and a folding mirror 41, and the optical element group 33 includes a common two-layer fθ lens 45 and a first , A reflection mirror 47, an imaging lens 49, and a reflection mirror 42 serving as a second reflection mirror. The optical element group 34 has two layers fθ
The optical element group 35 includes a lens 65, a first reflecting mirror 66, an imaging lens 67, a second reflecting mirror 62, and a reflecting mirror 43 serving as a third reflecting mirror. Lens (imaging lens) 65
, An imaging lens 68, and a folding mirror 44.

The optical element group 32 guides the beam corresponding to the yellow image to the surface of the photosensitive drum 5A, and the optical element group 33 directs the beam corresponding to the magenta image to the surface of the photosensitive drum 5B. Lead to. The optical element group 34 guides a beam corresponding to a cyan image to the surface of the photosensitive drum 5C, and the optical element group 35 guides a beam corresponding to a black image to the surface of the photosensitive drum 5D. As described above, this optical scanning device 6 has four stations that emit beams corresponding to images of yellow, magenta, cyan, and black, respectively, and the optical elements respectively located on the left and right sides in FIG. The mirrors of the groups 32 and 35 are each one of the folding mirrors 41 and 44 to constitute a quadruple tandem-type writing optical system.
Dustproof glass 16 for dustproof is attached to each outlet of the beam of each of the four stations from the optical housing 36.

The optical scanning device according to this embodiment is
In the device 6, as described above, the four optical element groups 32, 3
3, 34 and 35, and the optical element groups 32 and 33 in FIG.
On the left side of the director 31, the optical element groups 34 and 35 are located on the right side.
Each is arranged separately, and their positional relationship is
Each of the photosensitive drums 5A, 5
Each photoreceptor of the beam to be incident on B, 5C, 5D respectively
Incident angle α for drums 5A, 5B, 5C, 5D₁,
α₂, Α₃, Α₄Are all substantially equal.
Also, the photosensitive drums 5A, 5B, 5C, and 5D enter the respective photosensitive drums.
Extension L of beam to be emitted₁, L₂, L₃, L₄But light
Each optical axis LS from the deflector 31₁, LS₂, LS ₃, LS
₄From the point of intersection with the rotation center of the optical deflector 31
Distance LP to ₁And LP₄Become equal distances,
Distance LP₂And LP₃Each optic so that
Element groups 32 to 35 are arranged, respectively.

From these relationships, the photosensitive drums 5A, 5A
Distance P along the optical axis between the centers of B ₁And the photosensitive drum
Distance P along the optical axis direction between the centers of 5C and 5D₃Equal
And the photosensitive drums 5A and 5D
Incident angle α₁, Α₄Is also the same as mentioned above
And the beams corresponding to the yellow and black images
At each station to be handled, the photosensitive drums 5A, 5D
The electrophotography process to arrange each around
Equipment such as a charging device and a developing device for
Even if they are arranged in a common mounting posture,
A 、 Be sure to cut off the beam incident on 5D
Can be done. Therefore, each
Stations can use common equipment, so cost
Beam can be suppressed, and the beam
There is no need to downsize each device to avoid interruptions
In this way, stable performance can be maintained for a long time
Therefore, high reliability can be obtained.

The optical scanning device 6 according to this embodiment
Then, the positional relationship between the optical element groups 32 and 33 is represented by LP
It is set to ₁ -LP ₂ = 2LP _2. Therefore, LP ₁
-LP _2, the incident angle alpha _1, since alpha ₂ are the same photosensitive drum 5A, equal to the distance _{P 1} between 5B center, the _LP 1 -LP ₂ is a 2LP _2, LP ₂ is above since equal LP _{3 as, LP 1 -LP 2 = LP 2} +
LP ₃ and P ₁ = P ₂ . Thereby, P ₁
= P ₂ = P ₃ and the photosensitive drums 5A, 5B, 5
The distances along the optical axis direction between the centers of C and 5D are all the same. Therefore, in all of the four stations of yellow, magenta, cyan, and black, each device for executing the electrophotographic process around the photoconductor can be shared.

Incidentally, the optical scanning device 6 includes an extension line of the beam incident on each of the photosensitive drums 5A and 5D,
Folding mirror 4 at the intersection with the optical axis from optical deflector 31
The optical element groups 32 and 3 are arranged by disposing the optical element groups 1 and 44, respectively.
5 is configured to guide the beam to the photosensitive drums 5A and 5D by using only one mirror each. Therefore, 1
When a large number of mirrors are used in one station, the scanning lines are likely to bend or tilt due to the stacking of the accuracy of the parts holding each mirror and the surface accuracy of the mirrors themselves. However, by using a single mirror, the accuracy can be prevented from lowering due to the stacking of the mirrors, so that the alignment accuracy can be improved and the image quality can be improved. Further, as described above, when a large number of mirrors are used in one station, the scanning lines can be formed simply by improving the accuracy of the parts holding the respective mirrors and the surface accuracy of the mirrors themselves. When trying to solve the problem of bending and tilting, the cost may increase significantly, and even if this is done, there may be a problem in terms of productivity, but as in this embodiment, one mirror is used. If the number of sheets is increased, those problems can be solved and cost increase can be suppressed.

Further, in the optical scanning device 6, the distances LP ₁ and LP ₄ from the center of rotation of the optical deflector 31 to the turning mirrors 41 and 44 are n for the number of photosensitive drums and n for each of the photosensitive drums. The distance along the optical axis direction between the centers of the adjacent photosensitive drums is P (= P ₁ = P ₂ = P ₃ ), and the distance from the rotation center of the optical deflector 31 to the scanning surface of each of the photosensitive drums 5A to 5D. When each distance along the optical path is L, (n−
1) The relationship of × P / 2 <L is satisfied. The distance L is specifically, for example, LP ₁ + L ₁ in the case of the optical element group 32. Thus, as described above (n
-1) By configuring the optical scanning device so as to satisfy the relationship of × P / 2 <L, the writing optical system can be arranged according to a certain rule regardless of the number of photosensitive drums used. In addition, the number of folding mirrors can be reduced, and the layout of the optical system can be standardized, so that the development efficiency can be improved.

FIG. 3 is a schematic diagram similar to FIG. 1 showing another embodiment of the optical scanning device according to the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals. The optical scanning device according to this embodiment has the above (n-1) × P / 2 <
In a state where the relationship of L is satisfied, each station has three mirrors. That is, the second folding mirror 72 and the optical element group 32 '
The third reflection mirror 73 is added to change the optical path, and the optical element group 33 ′ changes the position of the second reflection mirror 42, and the third reflection mirror 83 is added to change the optical path. The second folding mirror 9 is added to the group 35 '.
The second and third folding mirrors 93 are added to change the optical path. In this case, since three mirrors are used for all the optical element groups, the accuracy of the scanning line bending and inclination is the same as that of the conventional three mirrors used for each station, but the mirrors are not used. Since the optical path can be bent and arranged by an amount corresponding to the larger number, the size of the optical housing 36 'for housing the entire writing optical system can be reduced. Accordingly, there is an advantage that the size of the entire image forming apparatus can be reduced.

FIG. 4 is a schematic diagram similar to FIGS. 1 and 3 showing still another embodiment of the optical scanning device according to the present invention, and portions corresponding to FIGS. 1 and 3 are denoted by the same reference numerals. I have. The optical scanning device according to this embodiment is similar to the optical scanning device shown in FIGS.
Is an intermediate example of the optical scanning device shown in FIG. 1, and the mirror of the optical element group 35 ″ located on the outside is composed of two mirrors. That is, the second folding mirror of the optical element group 35 ″ on the outside. Change the position of the mirror 92 and turn the mirror 9
An optical path is constituted by 2 and the folding mirror 44. The station having two mirrors is a station for forming a black image. By doing so, the accuracy of the scanning line bend and tilt can be improved. Therefore, this can be used as a reference for alignment. As described above, in the embodiment of the optical scanning device according to the present invention, the beam is applied to the photosensitive drum in FIGS.
Has been described in the case where the light is incident on the position of the second quadrant at the illustrated position, but the optical scanning device according to the present invention may be any device that satisfies the above-described relationship of (n-1) × P / 2 <L.
The present invention can be applied to a case where the beam is incident on any of the first to fourth quadrants.

[0023]

As described above, according to the present invention, the following effects can be obtained. According to the optical scanning device of the first aspect, in the plurality of optical element groups distributed to both sides of the optical deflector, the angles of incidence of beams respectively incident on the respective photoconductors from the mirrors of the respective optical element groups are substantially equal. It is arranged so that the distance from the intersection of the extension line of each beam incident on each photoreceptor to each optical axis from the optical deflector to the rotation center of the optical deflector is equal to each other. Therefore, even if a common charging device and developing device are used at each station distributed to both sides of the optical deflector and they are arranged in a common mounting position, they block the beam incident on the photoconductor halfway. Can be prevented. Therefore, it is possible to suppress an increase in cost and obtain high reliability with stable performance.

According to the image forming apparatus of the present invention, since each of the outermost mirrors of each of the optical element groups allocated to both sides of the optical deflector is constituted by one sheet, one station is formed. If a large number of mirrors are used in the scan line, the scanning line is likely to bend or tilt due to the stacking of the accuracy of the parts holding each mirror and the surface accuracy of the mirror itself, Since a reduction in accuracy due to the stacking can be prevented, the image quality can be improved by improving the alignment accuracy. Further, since the number of parts is reduced by minimizing the number of mirrors, the cost can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an arrangement relationship of each component constituting an optical scanning device according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram illustrating an image forming apparatus including the optical scanning device.

FIG. 3 is a schematic view similar to FIG. 1, showing another embodiment of the optical scanning device according to the present invention;

FIG. 4 is a schematic view similar to FIGS. 1 and 3, showing still another embodiment of the optical scanning device according to the present invention.

FIG. 5 is a perspective view showing an example of a conventional optical scanning device that forms a light spot on a photosensitive member using beams respectively emitted from a plurality of laser light sources.

[Explanation of symbols]

5A to 5D: photosensitive drum 6: optical scanning device 31: optical deflector 32, 33, 34, 35, 32 ', 33', 35 ', 3
5 ": optical element group 41, 42, 43, 44, 47, 62, 66, 69: folding mirror

Claims (2)

[Claims] An optical deflector deflects a beam emitted from each of a plurality of laser light sources to form a light spot on a plurality of photoconductors for each beam by a plurality of optical element groups each having a corresponding mirror. In the optical scanning device to be formed, the plurality of optical element groups are distributed and arranged on both sides with the optical deflector as a center, and the light of the beam which is incident on each photoconductor from the mirror of each optical element group. The angles of incidence on the body are substantially equal, and the distance from the intersection of the extension of each beam incident on each photoreceptor with each optical axis from the optical deflector to the center of rotation of the optical deflector is An optical scanning device, wherein the optical element groups are arranged so that the optical element groups distributed to both sides are equidistant from each other. 2. An image forming apparatus provided with the optical scanning device according to claim 1, wherein n optical members are provided, and the plurality of optical element groups distributed to both sides around the optical deflector. Each of the mirrors of each optical element group located on the outermost side is constituted by one piece, and the distance along the optical axis direction between the centers of the n photoconductors adjacent to each other is P,
When the distance along the optical path from the rotation center of the optical deflector to the surface to be scanned of each photoconductor is L, (n-1) × P
/ 2 <L.