JP3658075B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus including a first mirror unit that folds laser light back to an image carrier, and more particularly to position adjustment of the first mirror unit.
[0002]
[Prior art]
In recent years, an image forming apparatus as shown in FIG. 6 has been proposed.
[0003]
In the figure, laser light emitted from a laser light source (not shown) is scanned in both directions by a rotating polygon mirror 103 rotating in the direction of arrow B in the figure, and cyan (C), magenta (M), yellow (Y), black It passes through fθ lenses (not shown) respectively corresponding to (BK). Scanning light beams 102C, 102M, 102Y, and 102BK that have passed through the fθ lens rotate in the direction of arrow A in the figure via the reflection mirrors 6C to 8C, 6M to 8M, 6Y to 8Y, and 6BK to 8BK. , 101M, 101Y, 101BK are scanned to form respective color images, and are transferred onto the transfer material 105 conveyed in the direction of arrow X in the figure by the transfer belt 13 to form multiple images. The transfer unit belt 13 is driven by a transfer belt driving roller 31.
[0004]
[Problems to be solved by the invention]
In such an image forming apparatus, an increase in image quality is required in recent years. One technique for improving image quality is to increase the pixel density of laser light formed on the image carrier. Increasing the pixel density means that the interval between adjacent laser light spots is reduced, which means that a smaller minute spot is required.
[0005]
In order to realize a minute spot over the entire scanning range of the laser beam, it is obvious that the common depth of the spot diameter is reduced. Therefore, the optical path length of the laser light may change due to the position error of the mirror or the image carrier, and the common depth of the spots on the image carrier may be exceeded, and the image quality may be significantly deteriorated.
[0006]
Further, when the irradiation position is shifted, the image position is shifted in the transfer material feeding direction, which causes deterioration of image quality.
[0007]
In addition, it is necessary to maintain the same accuracy even after the mirror is detached and attached for maintenance of the apparatus.
[0008]
Furthermore, in an apparatus using a plurality of laser beams, if the positions of the pixel dots in the scanning direction of the respective laser beams are not matched, the image position will be shifted, causing image quality degradation. This is because in a color image forming apparatus using one laser beam, even if the pixel dot interval in the scanning direction is not constant, a plurality of images are superimposed with the same laser beam, but the image position is not shifted. This is a problem in an apparatus using the above laser beam.
[0009]
The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to adjust the scanning length and spot shape of the laser light on the image carrier by adjusting the mirror position. An object of the present invention is to provide an image forming apparatus that can be made possible and to improve image quality.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, there are provided a laser scanning optical unit and about two mirrors that return the laser light emitted from the laser scanning optical unit and guide it to an image carrier for image formation. The laser scanning optical unit and the first mirror unit are regulated in the longitudinal direction of the mirror in an image forming apparatus that can be independently fixed to the main body of the image forming apparatus. The first mirror unit can be adjusted to adjust the parallel movement in the irradiation direction in which the laser beam from the laser scanning optical unit is irradiated, and the rotational movement about the axis perpendicular to the parallel moving surface. comprising a member, said adjustment member includes a pin projecting from the image forming apparatus main body provided on the first mirror unit, that consists of a long hole in which the pin is inserted And butterflies.
[0011]
In the present invention , at the stage where the first mirror unit is assembled to the main body of the image forming apparatus, the position of the first mirror unit is deviated from the design center position due to the component tolerance of each part. When the scanning length and spot shape of the laser beam are measured, everything is out of order.
[0012]
Therefore, the inclination of the fixed position of the first mirror unit is adjusted so that the direction perpendicular to the mirror longitudinal direction of the first mirror unit is accurately oriented in the optical axis direction of the laser light. Further, the optical path length of the laser beam to the image carrier is adjusted by translating the laser scanning optical unit in the optical axis direction so as to coincide with the adjustment value in the laser scanning optical unit. As a result, a predetermined spot shape is formed over the entire scanning length of the image carrier.
[0013]
Thus, by adjusting the fixed position of the first mirror unit, it is possible to adjust the scanning length and the spot shape while keeping the irradiation position and inclination of the laser beam on the image carrier constant.
[0014]
Therefore, a minute spot shape with a shallow depth can be formed accurately.
[0015]
In addition, a second mirror unit is provided between the first mirror unit and the image carrier to reflect the laser beam from the first mirror unit and guide it to the image carrier, and the second mirror unit can be rotated and adjusted for rotation. It is characterized by being fixed.
[0016]
Thus, when there is a second mirror unit, the irradiation position and inclination of the laser beam on the image carrier can be accurately set by this second mirror unit, and the adjustment of the scanning length and the spot shape has been described above. Thus, it can be adjusted by the first mirror unit.
[0017]
If the adjustment position is marked after the position adjustment of the first mirror unit, the adjustment position can be accurately reproduced and re-adjusted when it is assembled after being removed for maintenance or the like.
[0018]
In addition, a plurality of laser beams are scanned on a plurality of image carriers through a plurality of first mirror units, and each first mirror unit is fixed to an image forming apparatus main body via an adjustment mechanism. It is characterized by being.
[0019]
In this way, the image positions of a plurality of laser beams can be made equal over the entire scanning area, and image displacement can be eliminated.
[0020]
Embodiment
Embodiments of the present invention will be described below.
[0021]
1 to 5 are explanatory diagrams of an image forming apparatus according to an embodiment of the present invention.
[0022]
In this image forming apparatus, a laser scanning optical unit 101 is attached to a stay 7 of the image forming apparatus main body 1 as shown in FIG.
[0023]
FIG. 4 shows details of the laser scanning optical unit 101.
[0024]
That is, four laser beams 102a to 102d of cyan, magenta, yellow, and black emitted from the laser light sources 120a to 120d are two places on the rotation plane of the rotary polygon mirror 101a and two places in the rotation axis direction, for a total of four places. The rotating polygon mirror 101a scans the laser beams 102a to 102d by rotating in the arrow A direction. Each scanned laser beam passes through the fθ lens systems 131 and 132 to form an image in a spot shape on the photoconductors 103a to 103d as image carriers.
[0025]
The laser scanning optical unit 101 is positioned in the holes 7a and 7b of the stay 7 of the main body by pins 201 and 202, and four fixing portions 133 (two are not shown because they are target shapes) are fixed to the stay 7 by screws or the like. Fixed to. The laser scanning optical unit 101 is in a unit state, and the spot shape and scanning length are adjusted with high accuracy.
[0026]
On the other hand, first mirror units 401a to 401d in which two mirrors are combined at about 90 ° are fixed on the main body stay 7, and the respective laser beams 102a to 102d are reflected substantially in parallel to be second mirror units 402a to 402d. Lead to.
[0027]
Here, details of the first mirror unit will be described with reference to FIGS.
[0028]
The description will be given by the first mirror unit 401a corresponding to the cyan image as a representative, and the other first mirror units 401b to 401d perform the same operation, so the description will be omitted.
[0029]
Although not shown, the first mirror unit 401a has a known color misregistration correction mechanism for correcting color misregistration.
[0030]
Two mirrors 6 a and 6 b are held by a holder 402. The holder 402 is held by the swing plate 403 and corrects the tilt deviation. The swing plate 403 is held by a fixed plate 404 and performs magnification shift correction independently of tilt shift.
[0031]
Here, when the direction orthogonal to the longitudinal direction of the mirrors 6a and 6b is the x-axis direction, the longitudinal direction of the mirrors 6a and 6b is the y-axis direction, and the direction orthogonal to the x-axis and y-axis is the z-axis direction, The movable plate 403 can be rotated in parallel with the zy plane around the x axis, and the swing plate 403 can be held in the fixed plate 404 so as to be rotatable around the y axis in parallel with the xz plane.
[0032]
The first mirror unit 401 a configured as described above has a position of the swing plate 403 with respect to the fixed plate 404 and a mirror holder 402 with respect to the swing plate 403 with reference to mounting reference surfaces 405 and 406 provided at both front and rear ends of the fixed plate 404. Are initially adjusted by motors 407 and 408, respectively. The attachment reference surfaces 405 and 406 position the first mirror unit 401 parallel to the xy plane and the xy plane.
[0033]
Although not shown, the motors 407 and 408 are coupled with screw shafts driven by the motors 407 and 408, screwed into nuts fixed to the swing plate 403 and the mirror holder 402, and positioned by rotation of the motors 407 and 408. It has come to be adjusted. The mirror holder 402 and the swing plate 403 by the motors 407 and 408 are used for fine adjustment of color misregistration correction.
[0034]
Next, the mirror 6a, 6b is adjusted so that the relative angle is 90 °.
[0035]
The light incident on the first mirror unit 401a thus adjusted is folded back almost in parallel as shown in FIG. 3 and guided to the second mirror unit 402a.
[0036]
Here, a method of attaching the first mirror unit 401a will be described with reference to FIGS. 1 and 2A.
[0037]
A pin 8 protrudes from the main body stay 7.
[0038]
On the other hand, the fixing plate 404 is provided with a long hole 409 into which the pin 8 is inserted. The pin 8 and the long hole 409 allow the first mirror unit 401a to be perpendicular to the mirror longitudinal direction (x-axis direction). ) Is movable, and an adjustment mechanism for restricting movement is configured in the mirror longitudinal direction (y-axis direction). In this state, the first mirror unit 401a has two degrees of freedom of rotation around the pin 8 extending in the z-axis direction on the xy plane and translation in the x direction.
[0039]
Then, the fixing plate 404 is rotated so that the optical axis of the laser beam 102a is orthogonal to the mirror longitudinal direction (y-axis direction), so that the x-axis and the optical axis coincide. Further, the optical path length of the laser beam 102a to the photoconductor 103a is laser-scanned by translating the first mirror unit 401a in the x-axis direction in the xy plane along the attachment reference surfaces 405 and 406 and the elongated hole 409. Since it can be made to coincide with the adjustment value in the optical unit 101, the scanning magnification (scanning length of the laser beam 102a on the photosensitive member 101a) is reproduced. When the scanning magnification is reproduced, the optical path length is reproduced, so that the spot shape is reproduced over the entire scanning area.
[0040]
Here, the meaning of adjusting the rotation of the fixed plate 404 will be additionally described.
[0041]
2B and 2C, in FIG. 2B, since the mirrors 6a and 6b are orthogonal to the laser beam 102a, the total scanning length is L on the photosensitive member 103a, and the scanning length to the middle point is L1 = L2.
[0042]
In FIG. 2C, since the mirrors 6a and 6b are not orthogonal to the laser beam 102a, the scanning length to the middle point on the surface of the photosensitive member 103a is P1 ≠ P2. In this case, the total scanning length P can be set to P = L by moving the first mirror unit 401a in the x-axis direction. However, although the total scanning length is P = L as described above, the lengths up to the midpoint are L1 ≠ P1 and L2 ≠ P2, resulting in image misalignment. Therefore, by rotating the fixed plate 404, it is possible to make an adjustment such that P1 = P2 = L1 = L2 while maintaining P = L.
[0043]
Next, the adjustment plate 9 and 10 is fixed to the fixing plate 404 of the first mirror unit 401a fixed to the stay 7 with the fixing tool 11 such as a screw after the adjustment is completed so that the adjustment position of the fixing plate 404 is uniquely determined. It is fixed with a fixture 11 such as an abutment or a screw. In this way, even when the first mirror unit 401a is removed from the main body stay 7 and returned to the stay 7 after performing maintenance or the like, the position reproducibility is obtained by abutting the fixing plate 404 against the adjustment plates 9 and 10. It is done.
[0044]
The laser beam 102a reflected by the first mirror unit 401a is reflected by the second mirror unit 402a and applied to the photosensitive member 103a.
[0045]
The configuration of the second mirror unit 402a will be described with reference to FIG.
[0046]
That is, the mirror 6 c is held by the holder 501 with the springs 502 and 503. The holder 501 has urging means (not shown) (not shown) at three points of a protrusion 504a provided at the opening edge of the rear plate 504 of the main body and the adjustment plates 505a and 505b attached to the opening edge of the front plate 505. The spring is pressed and held.
[0047]
Next, a method for adjusting the irradiation position by the second mirror unit 402a will be described.
[0048]
When one adjustment plate 505a is moved in the x direction relative to the other adjustment plate 505b, the mirror 6c rotates in the R direction and the laser beam 102a also rotates in the R direction, and the irradiation position on the photosensitive member 103a. However, the front plate 505 side and the rear plate 504 side change by the same amount.
When the adjustment plates 505a and 505b are moved in the x direction by the same amount, the mirror 6c is raised only on the front plate 505 side, and the inclination of the laser beam 102a on the photosensitive member 103a can be adjusted.
[0049]
In the above description, the scanning length and spot shape of the laser beam 102a can be adjusted by adjusting the position of the first mirror unit 401a, and the tilt and irradiation position of the laser beam 102a can be adjusted by adjusting the position of the second mirror unit 402a. The actual adjustment procedure will be described below.
[0050]
The laser scanning optical unit 101 is adjusted so that the scanning length and the spot shape become desired values at a position corresponding to the photoconductor 103a in a single unit state.
[0051]
The laser scanning optical unit 101 is fixed to the main body stay 7 as described above.
[0052]
The first mirror unit 401a and the second mirror unit 402a are temporarily fixed so as to be in the design position. When the laser beam 102a is scanned in this state and the scanning length, spot shape, irradiation position, and inclination are measured on the surface of the photosensitive member 103a, everything is out of order. This is because the first mirror unit 401a, the second mirror unit 402a, the photoconductor 103a, and the like are shifted from the design center value due to the intersection of parts. Therefore, first, the second mirror unit 402a is adjusted as described above to adjust the irradiation position and inclination of the laser light 102a to desired values.
[0053]
Next, the scanning length on the photoconductor 103a is adjusted by adjusting the first mirror unit 401a as described above. When the scanning length is adjusted in the image forming apparatus main body 1 to be the same as the value when the laser scanning optical unit 101 is single, the spot shape is also adjusted at the same time.
[0054]
At this time, the first mirror unit 401a is moved in the x direction in FIG. 2, but it is clear from FIG. 1 that the position of the optical axis of the laser beam 102a emitted from the first mirror unit 401a is unchanged. is there. Therefore, it is possible to adjust the scanning length and the spot shape while maintaining the irradiation position and inclination adjusted by the second mirror unit 402a first.
[0055]
By performing the same thing as the above adjustment also about the other laser beams 102b-102d, all the laser beams can be adjusted equally. In the above example, an image forming apparatus using a plurality of laser beams has been described, but it goes without saying that the same effect can be obtained when applied to an image forming apparatus using only one laser beam.
[0056]
【The invention's effect】
As described above, according to the present invention, it is possible to adjust the scanning length and spot shape of the laser beam on the image carrier by adjusting the position of the first mirror unit while keeping the irradiation position and inclination constant. High-quality image formation can be performed.
[0057]
In particular, a minute spot having a shallow depth can be reliably reproduced on the apparatus main body.
[0058]
Further, if the second mirror unit is fixed so as to be tiltable and rotatable, the irradiation position and inclination of the laser beam on the image carrier can be accurately set by the second mirror unit.
[0059]
Furthermore, if the adjustment position is marked after the position adjustment of the first mirror unit, the adjustment position can be accurately reproduced and re-adjustment is not required when it is assembled after being removed for maintenance or the like.
[0060]
In the case of an image forming apparatus that forms and multiplexes a plurality of images with a plurality of laser beams, if each first mirror unit can be adjusted, the image positions of the plurality of laser beams are equalized over the entire scanning area. Image misalignment can be eliminated.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing a first mirror unit and its optical path of an image forming apparatus according to an embodiment of the present invention.
2A is a schematic plan view of the first mirror unit of FIG. 1, and FIGS. 2B and 2C are explanatory diagrams for explaining the effect when the first mirror unit is rotated. FIG. It is.
3 is an overall configuration diagram of an image forming apparatus to which the first mirror unit of FIG. 1 is applied.
4 is a schematic perspective view of the laser scanning optical device of FIG. 3. FIG.
FIG. 5 is a schematic perspective view of the second mirror unit of FIG. 3;
FIG. 6 is a schematic perspective view of a conventional image forming apparatus.
[Explanation of symbols]
101 Laser scanning optical units 401a to 401d First mirror units 402a to 402d Second mirror units 102a to 102d Laser beams 103a to 103d Photosensitive members (image carriers)
6a, 6b Mirror 403 Oscillating plate 404 Fixed plate 405, 406 Mounting reference plane 8 Pin 9 Adjustment plate 10 Adjustment plate 11 Fixing tool

Claims (4)

A laser scanning optical unit; and a first mirror unit in which two mirrors that fold back the laser light emitted from the laser scanning optical unit and guide it to an image carrier for image formation are combined at about 90 °. In the image forming apparatus, the unit and the first mirror unit can be independently fixed to the image forming apparatus main body.
The movement in the longitudinal direction of the mirror is restricted, and the first mirror unit is translated in the irradiation direction in which the laser beam from the laser scanning optical unit is irradiated, and the rotation is performed around an axis perpendicular to the plane to be translated. An image having an adjustment member capable of adjusting movement, the adjustment member comprising a pin protruding from the main body of the image forming apparatus and an elongated hole provided in the first mirror unit into which the pin is inserted. Forming equipment.   A second mirror unit is provided between the first mirror unit and the image carrier to reflect the laser beam from the first mirror unit and guide it to the image carrier, and the second mirror unit is tilted and fixed so as to be rotatable. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein after the position of the first mirror unit is adjusted, a reproducible mark is added to the adjusted position.   A plurality of laser beams are scanned on a plurality of image carriers through a plurality of first mirror units, and each first mirror unit is fixed to an image forming apparatus main body so that its position can be adjusted. The image forming apparatus according to claim 1, 2, or 3.

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