JPS5955672A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus including a control device that controls the position at which an image is written onto a drum.

In a copying machine, such as a laser beam printer, which copies a large number of identical images, there are areas on the photosensitive drum that are frequently exposed and developed, and areas that are not. As a result, a phenomenon called partial deterioration occurs in the areas where exposure and development have been repeated, and when this photoreceptor drum is used to form another image next time, the developed density of the deteriorated areas deteriorates. The developed density does not increase compared to the areas that do not, and density unevenness occurs when viewed as a whole.

This is generally observed as white streaks on copy paper.

To prevent this, conventionally the photosensitive drum was axially swung to prevent light from hitting the same position. However, with this method, not only does the mechanism for swinging the drum become complicated, but also the vibration itself generated by the swinging operation often causes density unevenness in copies.

The present invention has been proposed in view of the above points, and the present invention detects the image end of a laser beam and appropriately swings the position of a beam sensor that determines the image writing position on the photosensitive drum in order to form an image without uneven density. An object of the present invention is to provide an image forming apparatus equipped with a control device.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial perspective view of an image forming apparatus equipped with a control device according to the present invention, in which Y is a light emitting body that emits laser beams S and A, 17 is a collimator that expands the beam diameter of the laser beam, 3 is a rotating polygon mirror that scans the laser beam; L is an imaging lens that forms an image of the laser beam on the electrophotographic photosensitive drum L that rotates in the direction of the arrow via the mirror q; 13
・7 is a light detection mirror and a light detection sensor unit which respectively determine the image writing position. FIG. 1 is a perspective view showing the control device according to the present invention in more detail. The light detection sensor section 7 is composed of a flexible optical fiber 20 and a photodiode IO, and the optical fiber 20 is configured to transmit a laser beam. It has a fiber end face θa for receiving light. The end of the fiber 20 is fixed to the fiber stand 2/, and the protrusion at the bottom of the fiber stand 2/ is slidable in a direction parallel to the scanning direction of the laser beam. It is fitted into the groove-shaped part unit a of the unit. Fiber stand, 2
/ is pressed against the end face of the cam 2t by the spring 3 via the rod 2/a fixed to the fiber stand 21.

The cam 2q is configured to be rotated by the intermittent suction operation of the plunger 29. That is, since the engagement arm 29a is pulled in the direction C by the plunger lever 9, the arm λB which is rotatable about the left side of the shaft 3 collapses. As a result, the shaft on which the arm unit O is attached, the gourd 27 which can be rotated around 2g, pushes the left tooth of the ratchet 2, and the ratchet, 2
Rotate the cam 2 fixed to S- by a predetermined angle. In addition, the return of arm 2 is done by the own weight of arm 2 or by the spring (
(not shown).

Next, the operation of the embodiment according to the present invention will be explained with reference to FIGS. Generally, image formation on the photosensitive drum 1 is performed as follows. That is, the laser beam emitted from the light emitting body passes through the collimator lens 17, is reflected by the rotating mirror 3, forms an image, passes through the laser beam L, is further reflected by the mirror q, and then is beamed onto the photoreceptor drum l, approximately parallel to the drum axis. The image is formed on a predetermined image scanning line 4 and scanned. By the way, the writing position of the laser beam on this image scanning line 4 is determined by the following procedure. First, the light beam emitted from the light emitter passes along the left optical path a, is reflected by the left side of the mirror q1 for detection, and reaches the light detection sensor section. After a certain period of time has passed since the sensor unit 7 detects the light, the power applied to the light emitting body is modulated according to the recorded image signal, and the light beam is made to flicker in response to the image signal. The image will be exported. When the first image is formed, Plancia and 2q make one round trip. This causes the cam 2g to rotate by a predetermined angle, so that the end face θa of the fiber coil θ moves via the rod Ω/a that engages with the cam 2da. Therefore, since the light reception time of the end face θa is shifted, the writing start position is shifted from g to 9 by a distance l in the scanning direction of the light beam. This operation is performed every time an image is formed. Note that the distance l is θ
/tsrx may be sufficient.

The electrostatic latent image formed by exposure to the light beam is developed by a developing device (not shown), and the toner image thus formed is transferred to the paper p conveyed in the direction of the arrow by a transfer charger (not shown). transcribed.

-G- Fig. 3 shows another embodiment of the fiber, the end of which is fixed to the fiber stand 2 and slides on the mounting stand 2.

The swing of the fiber table 2 is caused by the rotation of the pinion 31 driven by the servo motor 3θ.
This is done by transmitting the information to b.

FIG. 7 shows an embodiment in which the sensor section and the cassette 33 swing in synchronization. A cassette 33 that stores the transfer paper p and sends it out from there is loaded on a cassette stand 3.2 and slides in the direction d perpendicular to the conveyance direction of the transfer paper p. A fiber stand 21 to which a fiber end 0 is fixed is fixed to the cassette stand arm 3.2a and moves as the cassette 33 swings. In this way, when the starting position of the image on the drum l is shifted by 4 as described above, the moving path of the transfer paper is also shifted by l in the same direction, thereby preventing the image from protruding or missing from the transfer paper. The cassette stand 32 is swung by the rotation of the pinion 31 that engages with the rack portion 3.2b.

The rotation of the pinion 3 is performed by a drive motor 3θ.

FIG. S shows an example implemented by driving the wire q2. The cassette 33 is loaded on the cassette stand 32 and reciprocates in the d direction. Fiber column 0 fixed on fiber table 21
It is also possible to reciprocate the same distance in the same direction as the cassette 33. 3
θ is a motor, and the rotation of the drive pulley g/ is transmitted to the wire q2, and the cassette table 32 and the sensor table 21 are swung simultaneously. 36 to qθ are wire pulleys, and 11-2 to 11-2 are rotating shafts. In the embodiment shown in Figure 1 and 2, in which the sensor section 7 and the cassette 33 are configured to swing in synchronization, the writing start position and the copy paper move in the same direction and the same distance for each copying process, so that the sensor part 7 and the cassette 33 are oscillated in synchronization. Even if the image position moves in the direction of the drum axis, the image position on the transfer paper does not change.

As described above, according to the present invention, it is possible to prevent partial deterioration of the photosensitive drum when a large number of identical images are copied.

Therefore, the durability of the photosensitive drum is improved. Furthermore, it is possible to eliminate density unevenness in a copied image.

In the embodiment, a laser beam is used as a means for forming an image on a photoreceptor, but it is obvious that other means, such as ordinary light, can also be applied. Further, in the embodiment, the light detection sensor section is moved every time one image is formed, but it is also possible to move the light detection sensor section every two or more image formations as long as the photosensitive drum is not deteriorated. Furthermore, it is of course possible to appropriately determine the direction of movement of the position.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of an image forming apparatus equipped with a control device according to the present invention, FIG. 1 is a perspective view showing the control device according to the present invention in further detail, and FIG. 3 is a perspective view of another embodiment. Figures 1 and 2 are perspective views of improved embodiments. l...Photosensitive drum. Co... Luminous body. 3... Rotating mirror. q ... mira -. B... Image scanning line. 7... Light detection sensor section. ni・7...Writing start position. lO...Photodiode. lA...Imaging lens. 17...Collimator. 20...Fiber. 21...Fiber stand. Yu/a...ro tsu de. 21b...Rack section. 22...Mounting stand. 22a... Groove. , 23... spring. ,! G... cam. YuS...Ratchet. 27... Melon. ,! 9...Plancia. 3θ...Motor. 3rd...pinion. 32...Cassette stand. 33...Cassette. 36~tio...Wire pulley. 9/... Drive pulley. q2... wire. t3~q7...Rotation axis. K - Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] An image forming apparatus including a light detection sensor unit that controls the writing position of an image scanning line on a photoreceptor drum by receiving light from a light emitter in advance, An image forming apparatus for a copying machine, comprising a control device that controls the movement of the writing start position of the image scanning line by moving it every time image formation is completed a number of times greater than or equal to 7″!Takeko.