JPH04246668A - Method for assembling image forming device - Google Patents

Abstract

PURPOSE:To prevent the reduction of exposure-unit positioning accuracy, the staining of a photosensitive body caused by a roller, and damage to a photosensitive body film by eliminating the need for the spacing roller and a bearing, a shaft, etc., of the roller. CONSTITUTION:A positioning means setting reference positions, on the surfaces of a photosensitive body 2 sides provide on both sides of exposure unit 4 is provided. The gap between the reference position and the photosensitive body 2 is measured while the constant gap between them is maintained. Then positioning is carried out by oscillating finely the exposure unit 4. As the positioning means, for example, a displacement sensor 6 of a capacitance type, reflected-light detection type or electromagnetic induction type can be employed. A simple jig, providing reference surfaces 8 on both ends, can also be used. In such a case, the gap between the reference surface 8 and the photosensitive body 2 is measured by the use of a TV camera, etc.

Description

[Detailed description of the invention]

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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling an image forming apparatus used in printers, facsimile machines, copying machines, etc. of computers. $

[Prior Art] A conventional technology is shown in FIGS. 7 and 8. In the figure, 2 is a drum-shaped photoreceptor, 4 is an exposure device such as an LED printer head, and 02 is a space roller for keeping the distance between the photoreceptor 2 and the printer head 4 constant. The space roller 02 includes bearings, shafts, etc., and rotates as the photoreceptor 2 rotates. $ However, this conventional technique has a problem in that toner adheres to the rollers 02 and the distance between the printer head 4 and the photoreceptor 2 becomes incorrect. If the distance between the head 4 and the photoreceptor 2 is out of alignment, the focus accuracy will decrease and the printing quality will deteriorate. Further, due to the friction between the rollers 02 and the photoreceptor 2, the photoreceptor layer on the surface of the photoreceptor 2 is peeled off or damaged, and there is also a problem that toner is burned and attached to the photoreceptor 2 from the rollers 02. This is not the only problem, as Space Roller 02 requires expensive parts such as bearings and shafts, and requires a long assembly time to assemble with high precision. $

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the need for space rollers and solve these problems. $

[Structure of the Invention] A method for assembling an image forming apparatus according to the present invention is to position an exposure device so that the distance between it and the photoreceptor is constant. The present invention is characterized in that a positioning means is provided, and while this reference position is maintained in a non-contact manner with the photoreceptor, the distance between the reference position and the photoreceptor is measured and the exposure device is slightly moved to perform positioning. As the positioning means, for example, a displacement sensor such as a capacitance type, a reflected light detection type, or an electromagnetic induction type is used. Furthermore, a simple jig with a reference surface provided at the tip can also be used as a positioning means. In this case, the distance between the reference surface and the photoreceptor is measured using a television camera or the like. $

According to the present invention, instead of using a space roller to maintain the distance between the photoreceptor and the exposure device, the distance is measured using a displacement sensor or the like during assembly and is kept constant. Displacement sensors, etc. shall not be in contact with the photoreceptor. The detection accuracy of a displacement sensor or the like is inversely proportional to the distance from the photoconductor, so if the distance is made small, highly accurate positioning can be achieved. $ The reference position of a displacement sensor, etc. is used for positioning, there is no need to measure the position of the entire surface of the exposure device, and assembly can be completed in a short time. Furthermore, if the output of a displacement sensor or the like is fed back to a fine movement motor or the like, assembly can be automated. $

[Embodiment] An embodiment is shown in FIGS. 1 and 2. In the figure, 2
The photoreceptor is a drum-shaped photoreceptor having a photoreceptor film made of amorphous silicon or the like on its surface, and may also be made of an OPC film or the like in the form of a belt. Reference numeral 4 denotes an exposure device, which here uses an LED printer head, but may also be a laser printer head, a liquid crystal shutter printer head, or the like. Although the exposure device 4 is provided on the outside of the photoreceptor 2 here, the same applies to the case where the exposure device 4 is provided on the inside. Reference numeral 6 denotes a displacement sensor, which measures the distance d between the sensor and the photoreceptor 2 based on the change in capacitance between the sensor and the photoreceptor. The capacitance C between the displacement sensor 6 and the photoreceptor 2 is calculated as follows: where the dielectric constant of air is ε and the area of the capacitance measurement part is S, C=
It becomes ε・S/d. The displacement sensor 6 is attached to both ends of the exposure device 4,
A reference surface 8 is provided at the tip for positioning. Displacement sensor 6
The sensitivity of is inversely proportional to the distance d from the photoreceptor 2. On the other hand, the exposure device 4 and the photoreceptor 2 need to be spaced apart according to the focal length. Therefore, the displacement sensor 6 is made to protrude from the exposure device 4, and positioning is performed by setting the distance from the photoreceptor 2 to, for example, the order of mm or less. 10 is an amplification circuit for a detection signal of capacitance C; 12
14 is a capacitance/displacement conversion circuit for converting the capacitance C into a distance d, and 14 is a fine movement means for slightly moving the exposure device 4 back and forth using a signal from the conversion circuit 12. $ FIG. 3 shows the structure of the fine movement means 14. 16 is a die on which the exposure device 4 is mounted, and a threaded rod 18 and a guide shaft 20 are passed through the die 16. Threaded rod 18, guide shaft 20
is attached to a frame (not shown), and a motor (not shown) or the like is connected to the threaded rod 18. Also, the die 16 is a threaded rod 1
It is screwed together with 8. When the threaded rod 18 is rotated, the die 16 moves back and forth by one pitch of the screw for each rotation, allowing fine adjustment of the distance d between the die 16 and the photoreceptor 2. When the exposure device 4 is attached to the inner surface of the photoreceptor 2, for example, the displacement sensor 6 is held by an arm, and the arm is slightly moved back and forth. $ Figures 4 and 5 show other displacement sensors. The displacement sensor 26 in FIG. 4 is a combination of a light emitter 28 and a photoreceptor 30, and the photoreceptor 30 detects the light reflected by the photoreceptor 2, and from the position of the maximum light intensity, Measure the distance between. For example, if the photoreceptor 2 is located at the position indicated by the solid line in the figure, the photoreceptor 30
The intensity of the reflected light is at its maximum approximately at the center, but if it shifts to the position indicated by the chain line, the position at which the intensity of the reflected light is at its maximum shifts. In the displacement sensor 26 of FIG. 4, the positions and orientations of the reference planes 32 and 34 are important, and these reference planes are used as reference positions. $ The displacement sensor 36 in FIG. 5 uses a coil 38. Applying a current to coil 38 generates a magnetic field. This magnetic field causes an eddy current to flow through the photoreceptor 2, and changes in the magnetic field caused by this are fed back to changes in the current of the coil 38 and are detected, thereby measuring the distance from the photoreceptor 2. $ FIG. 6 shows a simpler method of assembling an image forming apparatus. In the figure, 40 is a positioning jig, and a reference surface 8 is provided at the tip. 42 is a television camera, 44 is an amplification circuit for the video signal of the television camera 42, and 46 is a video/displacement conversion circuit for detecting the distance between the photoreceptor 2 and the reference surface 8 from the video signal. $ Assembly of an image forming apparatus in an example will be explained. Figure 1
- In the case of FIG. 5, displacement sensors 6 and the like are attached to both ends of the exposure device 4 with high precision. The installation accuracy is, for example, ±50μ, including the flatness within the exposure device 4 and the installation error of the reference surface 8.
It is within the permissible range of about m. This is set in the fine movement means 14, and the distance from the photoreceptor 2 is adjusted. The sensitivity of the displacement sensor 6 and the like is inversely proportional to the distance d from the photoreceptor 2, and is measured by reducing the distance d. In the case of the embodiment shown in FIG. 1, the capacitance between the displacement sensor 6 and the photoreceptor 2 is inversely proportional to the distance d, so this is amplified by the amplifier circuit 10 and converted to the distance d by the capacitance/displacement conversion circuit 12. Feedback is given to the fine movement means 14 to keep the interval constant. $ In the case of a popular model, the exposure device 4 is placed in the correct position and then fixed, and the displacement sensor 6, fine movement means 14, etc. are removed from the exposure device 4. In the case of high-end machines, the image forming apparatus is shipped with the displacement sensor 6, fine movement means 14, etc. installed, and the distance between the photoreceptor 2 and the exposure device 4 is automatically kept constant during use. $ In the case of the embodiment shown in FIG. 6, the distance between the reference surface 8 and the photoreceptor 2 is monitored by the television camera 42, and fed back to the fine movement means 14 to fix the exposure device 4 at the correct position. After fixing, the television camera 42, fine movement means 14, etc. are removed. $

[Effect of the invention] This invention eliminates the need for space rollers,
(1) Eliminates the need for roller bearings and shafts,
(2) Eliminate deterioration in positioning accuracy of the exposure device due to contamination of the rollers; (3) Prevent contamination of the photoreceptor from the rollers and damage to the photoreceptor film. This invention further provides: (4) Since the sensitivity of displacement sensors, etc. is inversely proportional to the distance from the photoconductor, the distance can be reduced and assembled with high precision (
5) Eliminates the need to position the entire exposure unit by positioning the reference position provided on a displacement sensor, etc., (6) facilitates automation of assembly using displacement sensors, etc., and (7) enables non-contact Perform assembly to prevent damage to the photoreceptor.

[Brief explanation of the drawing]

[Figure 1] Front view of the example

[Figure 2] Side view of the embodiment

[Figure 3] Side view of the fine movement means used in the example

[Figure 4]
Front view of the displacement sensor used in the example

[Figure 5] Front view of the displacement sensor used in the example

[Figure 6] Front view of the second embodiment

[Figure 7] Front view of conventional example

[Figure 8] Side view of conventional example

[Explanation of symbols]

2 Photoreceptor 4 Exposure device 6, 26, 36 Displacement sensor 8, 32, 34 Reference plane 14 Fine movement means 16 Dice 18 Threaded rod 28 Luminous body 30 Photoreceptor 38 Coil 40 Jig 42 TV camera

Claims (1)

[Claims] 1. A method for assembling an image forming apparatus in which an exposure device is positioned so that the distance between the exposure device and the photoconductor is constant; The exposure device is positioned by measuring the distance between the reference position and the photoconductor and slightly moving the exposure device while keeping the position out of contact with the photoconductor.
How to assemble an image forming device.