JP3481394B2 - Image forming apparatus with optical scanning length adjustment mechanism - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having an optical scanning length adjusting mechanism, and more particularly to adjusting the optical path length to the photoconductor by changing the reflection angle from the reference position of the reflecting mirror to the front and back. The present invention relates to an image forming apparatus having an optical scanning length adjusting mechanism.

[0002]

2. Description of the Related Art Heretofore, various methods and apparatuses have been known for forming a multicolor image on a recording medium by transferring an image on a photoconductor exposed by a plurality of different light sources to a transfer body. Since these are multicolor images, first, the process of exposing and developing the photoconductor with the light source of the laser light in which the data is modulated on the photoconductor corresponding to a plurality of colors and then transferring it to the transfer body is performed a plurality of times. The image of each color is transferred to the same position on the transfer body. Therefore, unless these are transferred to the same position on the transfer body, the reproducibility of the image is deteriorated, and the contrast is poor and a blurred image is formed.

The reason why images from a plurality of different light sources are not transferred to the same position on the photoconductor is that the light emitting positions of the plurality of light sources are different, so that the exposure position on the photoconductor is deviated. It depends on the exposure timing of the optical system that exposes the latent image on the surface of the photoconductor, the magnification of the optical system, the inclination of the optical system, the manufacturing / assembly error of these mechanical parts, and the like.

The exposure timing can be adjusted and set so that an image is transferred to the same position on the photoconductor by electrically providing a suitable time lag. Further, as for the inclination of the photoconductor with respect to the transfer body, there is known a technique for improving the image shift by mechanically adjusting the inclination of the photoconductor to correct it, which can be solved. Further, the magnification and inclination of the optical system can be minimized by sharing the same optical system as much as possible or by using the same parts.

[0005]

However, according to the above-mentioned conventional technique, the parts are manufactured with high accuracy, the exposure timing is electrically set, the tilt of the magnification of the optical system is minimized, and the tilt of the photosensitive member is minimized. Even if is adjusted, the image shift phenomenon still occurs. That is, in FIG. 1, in the case of two photoconductors and two laser light sources, the laser position for irradiating the photoconductor 4A is deviated due to an assembly error even with the photoconductor 4B as a reference.

To explain this, in FIG. 3, the laser light emitted from the laser light source 1A is reflected by the polygon mirror 2 and is condensed on the surface 4Aa of the photosensitive member 4A via the condensing lens 3 for scanning, and the optical path 11 is formed. , 11 and Pa on the surface of the photoconductor.

In this case, Pa is a design position on the photoconductor, and Pb and Pc are positions where the photoconductor surface moves back and forth due to an assembly error. Considering Pa as a reference, when the position of the reflection mirror 7 moves back and forth from the design value and the distance S between the rear surface of the scanning condenser lens 3 and the surface of the photoconductor 4A changes, Pb of the photoconductor surface, The scanning distance changes like Pb, Pc, or Pc.

Therefore, as shown in FIG.
However, if the laser beam is set to scan between the photoconductor surfaces Pa, Pa, the scanning distance on the photoconductor 4A is set as Pb, Pb, or Pc, Pc on the photoconductor surface. Then, [D (distance between Pb and Pb) -E (distance between Pa and Pa)] / 2 = ΔD or [E (distance between Pa and Pa) -F (distance between Pc and Pc) ] / 2 = ΔE will be displaced. Therefore, at least the image shift occurs due to the error of the optical scanning length after the polygon mirror.

In view of the above circumstances, an object of the present invention is to provide an image forming apparatus provided with an optical scanning length adjusting mechanism capable of preventing image misalignment by adjusting the optical path length to a photosensitive member. Is.

[0010]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus equipped with an optical scanning length adjusting mechanism, in which a reflecting mirror for deflecting light from a light source and guiding it onto a photoconductor bus, and the reflecting mirror are attached. An image forming apparatus including an optical scanning length adjusting mechanism that has an arm configured to change a distance between a photoconductor and a reflection mirror and is swingable around an arbitrary fulcrum of the arm, Pass the light reflection point at the reference position of the reflection mirror and the focus on the generatrix on the photoconductor,
And, with the diameter of a small diameter circle having a laser incident light passing through the light reflection point as a tangent line as a radius, and when drawing a large diameter circle having a laser incident light passing through the light reflection point as a tangent line, the reflection mirror It is characterized in that a swing fulcrum of the arm is provided on a straight line orthogonal to the extension line at an intersection of the reflection surface extension line and the large diameter circle.

The X-axis is the direction of light incident on the reflection mirror.
The Y axis is aligned with the X axis and the central axis of the photoconductor.
When the light reflection point of the reflection mirror at the reference position is the center (0, 0) of the XY coordinate axis on the XY coordinate axes extending in the orthogonal direction, the linear equation orthogonal to the extension line is Y = −tan (θ / 2) × X−2L / sin θ (where θ is the reflection angle of the reflection mirror at the reference position, L is the distance from the reflection point of the reflection mirror to the photoconductor). Is an effective means.

Further, the position on the straight line where the swing fulcrum of the arm is provided is provided on the photoreceptor side from the intersection of the reflection surface extension line of the reflection mirror and the large diameter circle, which is an effective means of the present invention. is there.

In FIGS. 1 and 2, a reflecting mirror 7A for reflecting the light from the laser light source 1A to the photosensitive drum (photosensitive member) 4A is planted in the mirror mounting arm 6 and biases the arm 6 clockwise. At the same time, by bringing the reflecting mirror 7A into contact with the cam shaft 16 and rotating about the shaft core 6a,
The light reflection angle on the bus line of the photoconductor 4A is formed to be displaceable.

Passing through the light reflection point Q1 at the reference position of the reflection mirror 7A and the focal point on the bus line of the photoconductor 4A,
Moreover, the small diameter circle 12 having the laser incident light passing through the light receiving point Q4 as a tangent line, the diameter (2 × r) of the small diameter circle 12 being the radius R, and the laser incident light passing through the light reflecting point Q1 are A large diameter circle 13 which is a tangent line, a large diameter circle 13 which inscribes the small diameter circle 12 at the light reflection point Q1, and an intersection 13a with the reflection surface extension line 15 of the reflection mirror 7A are orthogonal to the extension line 15. If you draw the line 14 and
An axis 6a of the mirror mounting arm 6 is provided on the straight line 14 to configure it.

The laser light having the optical path 11 is reflected by the reflecting mirror 7A as a laser light having the optical path 11a at a reflection angle θ, and the cam shaft 16 is rotated to urge the laser light clockwise. Mounting arm 7
A can be rotated back and forth around the axis 6a from the reference position of the reflection mirror. As a result, the laser light is displaced like the optical paths 11b and 11c, and the photoconductor 4
The optical path length of the laser beam to A can be adjusted.

The X-axis is the direction of light incident on the reflection mirror.
The Y axis is aligned with the X axis and the central axis of the photoconductor.
When the light reflection point Q1 of the reflection mirror at the reference position is the center (0, 0) of the XY coordinate axis on the XY coordinate axes extending in the orthogonal direction, the linear expression 14 orthogonal to the extension line 15 is Y = − tan (θ / 2) × X−2L / sin θ (where θ is the reflection angle of the reflection mirror at the reference position, L is the distance from the reflection point of the reflection mirror to the photoreceptor). .

Therefore, by rotating the cam shaft 16, the mirror mounting arm 6 biased in the clockwise direction can rotate back and forth from the reference position of the reflection mirror about the axis 6a. The optical path 11a of the laser light reflected by the reflection mirror 7A at a reflection angle θ is displaced like 11b or 11c by rotating around the axis 6a of the reflection mirror 7A, and is moved to the photoconductor 4A. The optical path length of the laser light is adjusted. At this time,
The exposure point Q4 on the photoconductor 4A does not move, and the laser beam is exposed at the same focus position.

The axis 6a of the mirror mounting arm 6
May be located at any position on the straight line 14 and may be located on the left side from the intersection 13a between the large diameter circle 13 and the reflecting surface extension line 15 of the reflecting mirror 7A, as indicated by 6'in FIG. On the right side of the intersection 13a, that is, the photoconductor 4
When the axis 6a of the mirror mounting arm 6 is provided on the A side,
Can be placed close to the photoconductor and the intermediate transfer member,
It is desirable because it can be made compact without providing an extra space.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Only.

In the image forming apparatus according to the embodiment of the present invention, as shown in FIG. 1, a light beam from a laser light source 1A is optically scanned by a polygon mirror 2, a scanning condenser lens 3A, a reflection mirror 7A and the like. An electrostatic latent image is formed on the photosensitive drum (photosensitive member) 4A, which is an image bearing member, by the system. Although not shown, the photosensitive drum 4A is provided with a charger for charging the drum, a developing device (for example, black color and magenta color), a cleaning blade for removing residual toner, and the like.

The surface of the photosensitive drum 4A contacts an intermediate transfer sheet 17 (outer surface), which is a resistor having a volume resistivity of 10 ¹⁰ to 10 ¹⁴ Ωcm in a medium resistance region and a thickness of 150 μm. It is molded with a certain amount of polycarbonate, polyimide, polyether ether ketone, or the like.

The laser light source 1 is attached to the photosensitive drum 4B.
The light beam from B is a polygon mirror 2 and a scanning condenser lens 3
An electrostatic latent image is formed on the photosensitive drum (photoconductor) 4B, which is an image carrier, by an optical scanning system including B, the reflection mirror 7B, and the like. Although not shown, the photosensitive drum 4B is provided with a charger for charging the drum, a developing device (for example, cyan color and yellow color), a cleaning blade for removing residual toner, and the like.

Therefore, the photosensitive drums 4A and 4B are sequentially developed one by one from the developing device for each rotation of the drum and transferred to the intermediate transfer sheet 17 by Coulomb force. After the transfer of one color is completed, the photosensitive drum removes toner with a cleaning blade (not shown), and then another color is developed on the photosensitive drum. Specifically, the photosensitive drum 4
The black color is transferred from A to the intermediate transfer sheet 17 and then rotated to the position of the photosensitive drum 4B.
Cyan color 7 is transferred from the photosensitive drum 4B.

After transferring the black color to the intermediate transfer sheet 17, the photosensitive drum 4A removes the residual toner with a cleaner, develops the magenta color, and transfers the magenta color to the intermediate transfer sheet 17. Similarly, on the photosensitive drum 4B, after transferring the cyan color, residual toner is removed by a cleaner, and yellow is developed, so that the transfer is performed.

Next, the optical scanning length adjusting mechanism used in the image forming apparatus that operates as described above will be described. As shown in FIG. 1, a reflection mirror 7A that reflects the light from the laser light source 1A to the photoconductor 4A is embedded in the mirror mounting arms 6 and 6. The arms 6 and 6 are integrally provided by a shaft pillar 18, the shaft pillar 18 is rotatably supported by a ground plate (not shown), and is urged clockwise by a spring 19 wound around the shaft pillar 18. The reflection mirror 7A is formed so as to be displaceable with respect to the photoconductor 4A by being brought into contact with a cam shaft 16 provided on a base plate (not shown) and rotating about the axis 6a.

Further, in this embodiment, when the reflection mirror 7A is rotated, the reflected light to the photosensitive drum 4A is reflected by the photosensitive drum 4A.
It is characterized in that the axis 6a of the mirror mounting arm 6 is arranged at a position where the same point on A is exposed and does not deviate from the exposure point before rotation.

As shown in FIG. 2, the light reflection point Q1 at the reference position of the reflection mirror 7A is taken as the XY coordinate axis (0, 0), and the laser light entering along the X-axis along the optical path 11 is the light reflection point Q1. From the optical path 11a, and the light receiving point Q4 on the photosensitive drum 4A is exposed by the optical path 11a. At this time, if the length of the optical path 11a toward the light reflection point Q1 and the light reception point Q4 on the photosensitive drum 4A is L, the radius r of the small diameter circle 12 passing through the light reflection point Q1 and the light reception point Q4 is , R =
It is represented by L / 2 sin θ.

On the other hand, at the light reflection point Q1, the radius R of the large diameter circle 13 inscribed by the small diameter circle 12 is R = 2r =
It is represented by 2 × L / 2 sin θ = L / sin θ. When the extension line 15 of the reflection surface 7Aa of the reflection mirror 7A having the laser beam at the light reflection point Q1 is extended within the large diameter circle 13, the extension line 15 intersects the intersection 13a on the large diameter circle 13. . At this intersection 13a, a straight line 14 orthogonal to the extension line 15 intersects with an intersection 13b at which a center line passing through the light reflection point Q1 and the center 0 of the large diameter circle 13 intersects with the large diameter circle 13.

If the light reflection point Q1 at the reference position of the reflection mirror 7A is the XY coordinate axis (0, 0), this straight line 14 is Y = -tan (θ / 2) × X-2L / sin θ. It is represented by (1).

The axis 6a of the mirror mounting arm 6 is located at an intersection 13a of a large diameter circle 13 inscribed in the small diameter circle 12 at the light reflection point Q1 and an extension line 15 of the reflection surface 7Aa of the reflection mirror 7A. It is provided on a straight line 14 (Y) represented by the formula (1), which is orthogonal to the extension line 15.

Therefore, when the cam shaft 16 is rotated,
The mirror mounting arm 6 can be rotated back and forth around the axis 6a from the reference position of the reflection mirror 7A.
By this operation, the reflected light path is displaced to 11b or 11c and both are exposed at the light receiving point Q4 on the photosensitive drum 4A, and the reflected light paths 11a, 11b and 11c are not displaced from the light receiving point Q4.

When the distance between the rear end of the scanning condenser lens 3A and the reflection mirror 7A is K, the optical scanning length S between the rear end and the photosensitive drum 4A is represented by S = K + L,
At the light reflection points Q1, Q2, and Q3, the above S, K, and L
, S1, S2, S3, K1, K2, K3, L respectively
If 1, L2, L3, then K2>K1> K3, L2> L
1> L3, S2>S1> S3, and the optical path length to the photoconductor can be adjusted.

Therefore, when the photosensitive member 4B is set to the optical scanning length of Pa, Pa of 4Aa shown in FIG. 3, and the photosensitive member 4A has the optical scanning length of Pc and Pc of 4AC, for example, The upper arm 6 in FIG. 2 is rotated leftward to adjust the optical scanning length to be large so as to match Pa, Pa, or to be in the middle between Pa and Pc like 4Ad so that both of them are adjusted. Image error can be reduced.

The axis 6 of the mirror mounting arm 7A
a may be any position on the straight line 14 and is 6'in FIG.
As described above, it may be located on the left side from the intersection 13a of the large-diameter circle 13 and the reflection surface extension line 15 of the reflection mirror 7A, but the axis 6a of the mirror mounting arm 6 is located on the photoconductor 4A side. When it is provided, it can be placed close to the photoconductor and the intermediate transfer member, and it can be made compact without providing an extra space.

As described above, the present embodiment has a simple structure, has fewer adjustment points than the conventional one, and can easily cause image misalignment of the multicolor image forming apparatus on an improved assembly line or at the time of service in which parts are replaced. Can be adjusted.

[0036]

As described above in detail, the present invention provides an image forming apparatus provided with an optical scanning length adjusting mechanism capable of preventing image misalignment by adjusting the optical path length to a photosensitive member. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus including an optical scanning length adjusting mechanism according to the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of an optical scanning length adjusting mechanism.

FIG. 3 is an explanatory diagram illustrating an image shift.

[Explanation of symbols]

1 Laser light source (1A, 1'A, 1
B) 2 Polygon mirror 3 Condensing lens for operation (3A, 3
B) 4 photosensitive drum (photoconductor) 5 intermediate transfer body 6 mirror mounting arm 7 reflection mirror (7A, 'B) 11 optical path 12 small diameter circle 13 large diameter circle

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-4-251816 (JP, A) JP-A-6-24032 (JP, A) JP-A-6-109997 (JP, A) JP-A-6- 127020 (JP, A) JP-A 9-218470 (JP, A) JP-A 60-112020 (JP, A) JP-A 62-23014 (JP, A) JP-A 64-37525 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/04-1/207 B41J 2/44 G02B 26/10-26/12 G03G 13/04-13/056 G03G 15/04-15 / 056

Claims (3)

(57) [Claims] 1. A reflection mirror, which deflects light from a light source and guides the light onto a photoconductor bus, and an arm configured to change the distance between the photoconductor and the reflection mirror by mounting the reflection mirror. In an image forming apparatus having an optical scanning length adjusting mechanism configured to be swingable around an arbitrary fulcrum of an arm, a light reflection point at a reference position of the reflection mirror and a focus on a generatrix on the photoconductor are passed. In addition, when the diameter of a small diameter circle having a laser incident light passing through the light reflection point as a tangent line is a radius and a large diameter circle having a laser incident light passing through the light reflection point as a tangent line is drawn, the reflection mirror An image forming apparatus having an optical scanning length adjusting mechanism, wherein a swing fulcrum of the arm is provided on a straight line orthogonal to the extension line at the intersection of the reflection surface extension line and the large diameter circle. 2. The X axis is in the direction of light incident on the reflection mirror.
And the Y axis is orthogonal to the X axis and the central axis of the photoconductor.
When the light reflection point of the reflection mirror at the reference position is the center (0, 0) of the XY coordinate axis on the XY coordinate axis extending in the direction Y, the linear equation orthogonal to the extension line is Y = -tan (θ / 2) × X−2L / sin θ (where θ is the reflection angle of the reflection mirror at the reference position, L is the distance from the reflection point of the reflection mirror to the photoreceptor). Claim 1
An image forming apparatus provided with the optical scanning length adjusting mechanism described. 3. The position on the straight line where the swing fulcrum of the arm is provided is provided on the photoconductor side from the intersection of the extension line of the reflection surface of the reflection mirror and the large diameter circle.
Alternatively, an image forming apparatus including the optical scanning length adjusting mechanism described in 2.