JP2003270574A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner by which the occurrence of color slippage is suppressed. <P>SOLUTION: A housing 12 is formed so as to be symmetric to a center by holding the optical axis CL of Fθ lenses 18KC and 18MY in the optical scanner 10. Thus, since a thermal deformation mode is made symmetric by holding the optical axis CL even in the case that the housing 12 is thermally deformed by the temperature rising of an image forming apparatus due to driving or the like, the deformed states of mirrors 24K-24Y and cylinder mirrors 22K-22Y disposed so as to be symmetric to the center by holding the optical axis CL are made equal to the center, so that the occurrence of a difference in the deviation value of the scanning position of each color is suppressed. Thus, in the image forming apparatus to which the optical scanner 10 is attached, the occurrence of the color slippage is suppressed, so that excellent image forming is performed. <P>COPYRIGHT: (C)2003,JPO

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 used in a multicolor image forming apparatus using electrophotographic process technology.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic process technology, an electrostatic latent image is formed on a uniformly charged photosensitive member by scanning light from an optical scanning device.
This electrostatic latent image is developed with toner, and the obtained toner image on the photoconductor is transferred and fixed on a sheet to record an image. Particularly in a multicolor image forming apparatus, scanning light from an optical scanning device is applied to each of a plurality of photoconductors to form an electrostatic latent image, which is developed with toner of a different color for each photoconductor, and then the latent image is formed on a sheet. A multicolor image is recorded by superposing and transferring and fixing. An optical scanning device in such a multicolor image forming apparatus has light sources of the number of colors to be developed on one optical housing, and the laser light emitted from each light source is incident on one rotating polygon mirror. There is a system in which a deflected laser beam is imaged and scanned on a photoconductor corresponding to each laser beam. Japanese Patent Laid-Open No. 10-254212 (hereinafter referred to as Conventional Example 1) is a conventional example of an optical scanning device using this method (see FIGS. 5 to 7). That is, the optical scanning device 100 is mounted on a single optical housing 102.
One light source unit 104C, 104M, 104Y, 10
Each of the laser beams LC to LK emitted from each of the light sources 104C to 104K includes one rotary polygon mirror 10.
The image is formed and scanned on the photoconductors 112C to 112K via the fθ mirrors 108CM and 108YK as image forming elements having the fθ characteristic and the toroidal lenses 110C to 110K forming the surface tilt correction system. Where 4
The one light source unit 104C to 104K is the housing 1
02, the fθ mirrors 108CM and 108YK are all arranged on the same side with respect to the optical axis CL (see FIG. 5).
In addition, on the outer peripheral wall 114 of the optical housing 102, the mounting surfaces 114C to 114C for the light source units 104C to 104K are arranged so that the emission directions of the laser beams LC to LK of the respective light source units 104C to 104K are directed to the rotary polygon mirror 106. 11
4K is formed. Further, as another conventional example (hereinafter referred to as conventional example 2), there is an optical scanning device for a multicolor image forming apparatus shown in FIGS. Here again, the optical scanning device 120
Has four light sources 124 on a single optical housing 122.
Y, 124M, 124C, 124K (124Y-124
Laser beams LY to LK emitted from K, other reference symbols are also the same) are incident on one rotary polygon mirror 128 through the mirrors 126YM and 126CK and are deflected to scan the scanning lenses 130YM and 130CK having the fθ characteristic. Through,
Finally, images are formed and scanned on the photoconductors 132Y to 132K from the longitudinal mirrors 131Y to 131K, respectively. In the optical housing 122 of the optical scanning device 120, the light sources 124Y to 124K include scanning lenses 126YM and 126YM.
All are arranged on one side with respect to the optical axis CL of CK.
Along with this, the outer peripheral wall 1 of the optical housing 122
22A requires mounting surfaces 134Y to 134K for mounting the light source in consideration of the emission direction of the laser light, and the outer peripheral wall 12
2A is asymmetric with respect to the optical axis CL of the scanning lenses 126YM and 126CK. Furthermore, the light sources 124Y to 124K
The optical members forming the optical system from the mirrors 126YM to 126CK are all arranged on the light source side with respect to the optical axis CL.

Optical scanning is affected by the flatness error of the image forming apparatus frame to which the optical scanning device 120 is attached and the twist of the entire image forming apparatus frame that occurs when the image forming apparatus is placed on a floor that is not horizontal. In order to prevent the device 120 from being deformed, the optical scanning device 120 is fixed to the image forming device frame at three fixing portions 136A to 136A.
It is done at 36C.

[0004]

In the optical scanning device of such a multicolor image forming apparatus, since the overlay accuracy of each color affects the image quality, the positions and inclinations of the scanning lines of each color and the image magnification are adjusted. There is a need. However, if the temperature inside the image forming apparatus rises during operation, the optical housing may be deformed due to thermal expansion, or if there is a difference in the coefficient of linear expansion between the optical housing and the frame of the image forming apparatus main body, it may occur between the fastening points of the two. There is a difference in the amount of expansion due to heat, which may cause the optical scanning device to bend or deform, causing a deviation in the optical path of the laser light emitted from the optical scanning device toward the photoconductor. Particularly, in an optical scanning device of a multicolor image forming apparatus that has a plurality of optical paths in one optical housing and scans laser light toward a plurality of photoconductors, the thermal deformation mode of the optical housing is the optical axis of the scanning lens. If both sides of the scanning line are different from each other, a difference between the inclinations of the respective scanning lines and a horizontal magnification is generated, and a color shift appears on the image. For example, in Conventional Example 1 (see FIG. 5), the outer peripheral wall 114 of the housing 102 is attached to the mounting surface 1
14C to 114K, the housing 102 (outer peripheral wall 114) is asymmetrical with respect to the optical axis CL of the fθ mirrors 108CM and 108YK. Therefore, the fθ mirror 108CM, 10
The thermal deformation mode of the housing 102 is different on both sides of the optical axis CL of 8YK. As a result, the longitudinal mirror 109M (see FIGS. 5 and 7) arranged between the fθ mirror 108CM and the toroidal lens 110 on the optical path is thermally deformed at one end (light source side end) in the scanning direction and the other end. Since the amount of movement and the direction of movement differ depending on the
The inclination of the scanning line occurs at 12M. The same thing happens for the longitudinal mirror 109Y, so the photoconductor 112Y
Although the scanning lines are tilted on the upper side as well, the amounts of change in the tilts of both scanning lines are different from each other, so that when the toner images developed from both scanning lines are superposed on the paper, they appear as color shifts. On the other hand, in the outer peripheral wall 123 that configures the optical housing 122 of the optical scanning device 120 according to Conventional Example 2, the outer peripheral wall 123A on the light source side sandwiches the optical axis CL of the scanning lenses 130YM and 130CK, and the light sources 124Y to 124K are desired. The side wall 123B on the side opposite to the light source side is configured to be a relatively straight surface including the reinforcing ribs, while the side surface 123B on the side opposite to the light source side is configured to have a concavo-convex shape including the mounting surfaces 134Y to 134K that are bent for mounting in the direction. . Therefore, the light source side (side wall 123A) of the outer peripheral wall 123 has a lower rigidity than the opposite side (side wall 123B), and the distortion due to thermal deformation increases. Further, the fixing portions 136A to 136C of the optical scanning device 120 with respect to the image forming apparatus are provided at three positions, and the positions thereof are provided at one position on the optical axis CL of the scanning lenses 130YM and 130CK, and at two positions substantially symmetrical with the optical axis CL sandwiched therebetween. Has been. Therefore, when thermal deformation occurs in the optical housing 122 due to a temperature rise in the apparatus due to driving of the image forming apparatus or the like, a difference occurs in the amount of thermal deformation between the light source side and the opposite side, and the arrows B and C shown in FIG. The entire housing 122 is twisted and deformed about the axis O passing through the fixed portion A in the direction. At this time, the longitudinal mirrors 131Y to 131K placed on the optical housing 122 increase in size from the one-point fixed side to the two-point fixed side, that is, the longitudinal mirrors 131K, 131C, 131M, and 131Y in order in accordance with the twist of the entire housing. The posture changes in the direction of the arrow shown. Therefore, the undeformed scan lines SK, SC, S guided by each longitudinal mirror
M and SY (see FIG. 10, solid line) are SK ′,
It becomes the position of SC ', SM', SY '(see the chain double-dashed line in FIG. 10), and the amount of change in each inclination is K, C, M, Y.
The amount is different in the order of. This appears as a color shift on the image. At the same time, as shown in FIG. 11, the scanning areas of the scanning lines SY 'and SK' after thermal deformation guided by the longitudinal mirror 131Y and the longitudinal mirror 131K also differ according to the twist of the entire housing, and as a result, the lateral magnification is changed. The ratio is also a: b for the scanning line SY 'and c: d for the scanning line SK', and this also appears as a color shift on the image.

In this way, a plurality of light sources are provided on one optical housing, and the laser light emitted from each light source is incident on one rotating polygon mirror to be deflected, and the deflected laser light is emitted to each laser light. In the optical scanning device of the multi-color image forming apparatus which forms and scans on the photoconductor corresponding to the above, the thermal deformation mode of the optical housing becomes asymmetric with respect to the optical axis of the scanning lens, and the color shift becomes remarkable. There is.
In particular, when the number of fixing points of the optical scanning device with respect to the image forming apparatus is three, asymmetry of thermal deformation causes a twist in the entire optical housing, which causes a difference in scanning line inclination (SKEW) between colors and a lateral magnification difference. There is a problem that the difference in fluctuation amount becomes large and the color shift on the image becomes large.

In order to eliminate the above-mentioned inconvenience, the present invention provides
An object of the present invention is to provide an optical scanning device that suppresses deformation of a housing that causes color misregistration in an image forming apparatus.

[0007]

In order to solve the above-mentioned problems, in the optical scanning device according to claim 1, a plurality of light sources for emitting a light beam and one light source for reflecting and deflecting the light beam for scanning are provided. A rotating polygon mirror, a scanning image forming optical system including a scanning lens for forming an image of the deflected light beam on a surface of a photosensitive member and scanning the surface at a constant speed, and an optical housing for mounting the scanning image forming optical system. And a fixed point of the optical housing with respect to the image forming apparatus is arranged symmetrically with respect to the optical axis of the scanning lens, and the shape of the optical housing is It is characterized in that it is substantially symmetrical with respect to the optical axis of the scanning lens.

The operation of the optical scanning device according to the first aspect will be described.

Since the fixing point of the optical housing with respect to the image forming apparatus is symmetrical with respect to the optical axis of the scanning lens disposed inside the housing, the shape of the housing is substantially symmetrical with respect to the optical axis. , The thermal deformation mode is symmetric with respect to the optical axis. Therefore, the posture change due to the thermal deformation of the optical components forming the scanning optical system disposed inside the optical housing is also symmetrical about the optical axis. As a result, the SKE between the colors formed on the surface of the photoconductor of the image forming apparatus is increased.
The difference in W variation and the difference in lateral magnification variation are reduced. As a result, color misregistration in the image forming apparatus is suppressed.

The optical scanning device according to a second aspect is the optical scanning device according to the first aspect, wherein the optical housing has an outer peripheral wall, and the shape of the outer peripheral wall is symmetrical with respect to the optical axis of the scanning lens. Is characterized by.

The operation of the optical scanning device according to the second aspect will be described.

By forming the outer peripheral wall of the housing symmetrically with respect to the optical axis of the scanning lens, twisting of the housing is suppressed, and color misregistration in the image forming apparatus is further suppressed.

An optical scanning device according to a third aspect is the optical scanning device according to the first or second aspect, in which, in the optical housing, a difference in weight between two regions with the optical axis of the scanning lens as a boundary is the entire optical housing. Is less than 5% by weight.

The operation of the optical scanning device according to the third aspect will be described.

Since the weight difference between the two regions divided by the optical axis of the scanning lens of the optical housing is within 5% of the total weight of the optical housing, the deformation due to the weight imbalance of the optical housing is suppressed. That is, since the asymmetrical deformation factors other than heat are removed, the symmetry of the deformation of the optical housing is more favorably secured. Therefore, color misregistration in the image forming apparatus is suppressed.

An optical scanning device according to a fourth aspect is the optical scanning device according to the first aspect.
3. The optical scanning device according to any one of 3 above, wherein the scanning imaging optical system is symmetrical with respect to the optical axis of the scanning lens.

The operation of the optical scanning device according to the fourth aspect will be described.

Inside the optical housing, the optical components constituting the optical scanning system are arranged symmetrically with respect to the optical axis of the scanning lens, so that the deformation of the housing becomes more symmetrical and, as a result, the image forming apparatus Color shift is further suppressed.

[0019]

DETAILED DESCRIPTION OF THE INVENTION An optical scanning device according to an embodiment of the present invention will be described.

As shown in FIG. 1, an optical scanning device 10 used in a multicolor image forming apparatus has a housing 12 inside which
A scanning optical system corresponding to four colors of black (K), cyan (C), magenta (M), and yellow (Y) is configured. The scanning optical system has four beam light sources 14K, 14C,
The light beams LK to LY emitted from 14M and 14Y (hereinafter also referred to as 14K to 14Y, other reference numerals are the same) through the illustrated optical system (the description of the individual optical members is omitted). The light enters the rotary polygon mirror 16 that rotates at a constant speed in the R direction. Each light beam L deflected by the rotating polygon mirror 16
K to LY are scanning optical systems (fθ lens) 18KC, 18
After passing MY, the corresponding mirror 20K
~ 20Y, cylinder mirror 22K ~ 22Y, mirror 2
It is sequentially reflected by 4K to 24Y and is irradiated onto the photosensitive drums 26K to 26Y of the image forming apparatus corresponding to the respective colors. As a result, the respective light beams LK to LY are mainly scanned on the photoconductor drums 26K to 26Y by the rotation of the rotary polygon mirror 16, as shown in FIG.
A latent image is formed on ~ 26Y. In this embodiment, the planes passing through the center line of the scanning range of the light beams LK to LY directed to the photoconductor drums 26K to 26Y are the scanning lenses 18KC and 1K, respectively.
It is configured to pass through the optical axis CL of 8MY.

The latent images formed on the photosensitive drums 26K to 26Y are developed by a developing device (not shown), the toner images are sequentially transferred to the transfer belt, and the toner images are transferred and fixed on the conveyed paper. To form a color image.

On the other hand, the housing 12 of the optical scanning device 10
Are formed symmetrically with respect to the optical axis (center of the scanning range) CL of the scanning optical systems 18KC and 18MY (see FIG. 1). Not only is the shape of the housing 12 including the reinforcing ribs on the bottom surface 30 (see FIG. 3) symmetrical, but also the shape of the outer peripheral wall 32 is symmetrical. That is, since the housing 12 is provided with the base 34 for disposing the cylinder mirrors 22K to 22Y and the mirrors 24K to 24Y, the outer peripheral wall 32 is a flat portion of the upper portion formed at the end of the base 34 at the portion. 32A and a mounting surface portion 32B for the beam light sources 14K to 14Y that is bent to emit a beam in a predetermined direction below the flat surface portion 32A, and the mounting surface portion 32B has beam light sources 14K, 14Y, 1
Mounting surface 36K, 36Y, 36M for mounting 4M
including. That is, the side wall 33A on the side where the beam light sources 14K to 14Y are attached and the side wall 33B on the side where the beam light sources 14K to 14Y are not attached are similarly configured, so that the outer peripheral wall 32 is formed symmetrically with respect to the optical axis CL. Further, the other mirrors 20K to 20Y and the like, such as the shape of a supporting portion (not shown) of a mirror forming a scanning image forming optical system, are symmetrical with respect to the optical axes CL of the scanning lenses 18KC and 18MY over the entire housing.

Further, the housing 12 is provided with fixing portions 40A to 40C for attaching to the image forming apparatus, the fixing portion 40A is provided on the optical axis CL on one side surface, and the fixing portions 40B and 40C are provided. It is provided in a symmetrical position with the optical axis CL on the other side. Each fixed part 40A-4
Each of the 0C has a hole 42 and is fixed to the apparatus with a bolt or the like.

In addition to the above, the housing 12 is provided with bosses 46 and 48 for independently guiding the label sticking position, which are present on the harness holding projection 44 and the outer peripheral wall 32.

The operation of the optical scanning device 10 thus constructed will be described.

When the internal temperature of the apparatus rises due to the driving of the optical scanning device 10 or the image forming apparatus to which the optical scanning device 10 is attached and the housing 12 is thermally deformed, the fixing portion 40A is fixed.
Since the arrangement of ˜40 C and the shape of the housing 12 are symmetrical with respect to the optical axis CL of the fθ lenses 18KC and 18MY, the thermal deformation modes of the housing 12 are symmetrical on both sides of the optical axis CL. As a result, the amount of movement and the direction of movement due to thermal deformation are equal at the light source side end and the other end of the mirror 24K, and therefore, the inclination of the scanning line and the lateral magnification change do not occur on the photoconductor 26K.

Further, the side wall 33A to which the light source is attached
Since there is no difference in the amount of deformation between the side wall 33B and the side wall 33B that faces it, the torsional deformation of the housing 12 as described in the conventional example (see FIGS. 10 and 11) does not occur. Therefore, the inclination of the scanning line and the lateral magnification change due to the torsional deformation of the housing 12 do not occur.

It should be noted that the bosses 46 and 48 for independently guiding the label attachment position, which are present on the harness holding protrusion 44 and the wall surface, are provided.
In the housing 12, the f.theta.
It may not be provided symmetrically with respect to the optical axis CL of 8KC and 18MY.

An optical scanning device according to the second embodiment of the present invention will be described. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The optical scanning device 50 according to this embodiment is shown in FIG.
As shown in FIG. 5, the shape of the housing 12 is the same as that of the first embodiment, but the beams LK to LY are incident on the rotary polygon mirror 16 from the beam light sources 14K and 14Y, the beam light sources 14C and 14M, and the beam light sources 14K to 14Y. By arranging the mirrors 52K and 52Y to be mirrored and the mirrors 52C and 52M at symmetrical positions with respect to the optical axis CL, the beam light source 1
The optical paths from 4K to 14Y to the rotary polygon mirror 16 (arrangement of optical components forming the optical system) are also set symmetrically with the optical axis CL interposed therebetween.

The operation of the optical scanning device 50 thus constructed will be described.

Optical scanning device 50, or optical scanning device 50
If the temperature inside the apparatus rises due to the driving of the image forming apparatus to which the is attached and thermal deformation occurs, the thermal deformation modes of the housing 12 are symmetrical on both sides of the optical axis as in the first embodiment. The inclination of the scanning line and the lateral magnification change do not occur above.

The beam light sources 14K and 14Y, the beam light sources 14C and 14M, and the mirrors 52K, 52Y and 52, respectively.
Since C and 52M are provided symmetrically with respect to the optical axis CL,
The optical system from the beam light sources 14K to 14Y to the incidence on the rotary polygon mirror 16 is also symmetrical with respect to the optical axes CL of the scanning lenses 18KC and 18MY, and the optical axes CL of the scanning lenses 18KC and 18MY are used as boundaries in the entire optical scanning device. Since there is no difference in weight between the two areas, torsional deformation of the housing is less likely to occur.

Among the components involved in the scanning of the laser light emitted from the optical housing 12 according to this embodiment and one light source (for example, the light source 14K), the scanning lenses 18KC and 18MY are with respect to the optical axis CL. Table 1 shows the weights of the materials arranged on one side.

[0035]

[Table 1] It can be seen from Table 1 that among the components involved in the scanning of one color, the weight of the components arranged on one side of the optical axes CL of the scanning lenses 18KC and 18MY corresponds to approximately 5% of the weight of the optical housing. Recognize. Therefore, the optical scanning device 50
(See Fig. 4) The parts that are involved in the scanning of the four colors, that is, the weight unbalance equivalent to about 20% of the weight of the optical housing, is not created in advance, and the torsional deformation due to the weight imbalance is minimized. can do.

From the above, it is desirable that the unbalanced amount of the weight of the single housing is equal to or less than the weight of the components involved in scanning for at least one color. Therefore, it is preferable that the weight difference between the two regions having the optical axis of the scanning lens as a boundary is within 5% of the entire optical housing. As a result, even in the optical scanning device having the optical system which is asymmetric with respect to the optical axis of the scanning lens as in the first embodiment (see FIG. 1), the torsional deformation due to the weight imbalance can be minimized.

[0037]

As described above, in the optical scanning device of the present invention, since the optical housing has a symmetrical shape with respect to the optical axis of the scanning lens, the difference in SKEW fluctuation amount between the colors and the left and right at the time of thermal deformation. The difference in the amount of change in magnification is reduced. Therefore, a good image without color shift can be obtained.

Further, by making the optical system from the light source to the photosensitive member symmetric with respect to the optical axis of the scanning lens, the difference in weight between the two regions bounded by the optical axis of the scanning lens in the entire optical scanning device. It suppresses twisting deformation of the optical housing due to weight imbalance.

[Brief description of drawings]

FIG. 1 is a plan view of an optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a side view of the optical scanning device according to the first embodiment of the present invention.

FIG. 3 is a bottom view of the optical scanning device according to the first embodiment of the present invention.

FIG. 4 is a plan view of an optical scanning device according to a second embodiment of the present invention.

FIG. 5 is a plan view of an optical scanning device according to Conventional Example 1.

FIG. 6 is a perspective view of an optical scanning device according to Conventional Example 1.

FIG. 7 is a side view of an image forming apparatus to which an optical scanning device according to related art 1 is attached.

FIG. 8 is a plan view of an optical scanning device according to Conventional Example 2.

FIG. 9 is a side view of an optical scanning device according to Conventional Example 2.

FIG. 10 is a diagram illustrating a color misregistration state in the optical scanning device according to Conventional Example 2.

FIG. 11 is a diagram illustrating a deformed state of a housing in the optical scanning device according to the second conventional example.

[Explanation of symbols]

10, 50 ... Optical scanning device 12 ... Optical housing CL ... Optical axis of scanning lens

Continued front page    (72) Inventor Junichi Morooka             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office (72) Inventor Naohiro Tada             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office F-term (reference) 2C362 AA46 BA04 BA50 BA52 BA53                       BA85 DA03                 2H045 AA01 BA22 BA34 DA04 DA41                 5C051 AA02 CA07 DB22 DB24 DB30                       EA01                 5C072 AA03 BA12 DA02 DA04 DA21                       HA02 HA06 HA09 HA13 QA14                       QA17 XA05

Claims (4)

[Claims] 1. A plurality of light sources for emitting a light beam, one rotating polygonal mirror for reflecting and deflecting the light beam, and the deflected light beam are imaged on a surface of a photoconductor and scanned at a constant speed. An optical scanning device provided in a multicolor image forming apparatus, comprising: a scanning image forming optical system including a scanning lens; and one optical housing on which the scanning image forming optical system is mounted. An optical scanning device, wherein fixed points of the optical housing are arranged symmetrically with respect to the optical axis of the scanning lens, and the shape of the optical housing is substantially symmetrical with respect to the optical axis of the scanning lens. 2. The optical scanning device according to claim 1, wherein the optical housing has an outer peripheral wall, and the shape of the outer peripheral wall is symmetrical with respect to the optical axis of the scanning lens. 3. The optical housing according to claim 1, wherein the difference in weight between two regions bounded by the optical axis of the scanning lens is within 5% of the total weight of the optical housing. Optical scanning device. 4. The scanning imaging optical system is symmetrical with respect to the optical axis of the scanning lens.
The optical scanning device according to claim 1.