JPH0731437B2 - Rotation control device for image forming apparatus - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a rotation control device for a photosensitive drum in an image forming apparatus or the like.

BACKGROUND OF THE INVENTION

Generally, in an image forming apparatus such as a transfer type electrophotographic copying machine, a rotary drum type photoconductor having a photoconductive photoconductive layer on its outer peripheral surface is used, and an electrostatic latent image is formed on the photoconductive layer while rotating the photoconductive drum. An image is formed and developed with toner, and the obtained toner image is transferred to a recording sheet. In a multicolor image forming apparatus that forms a multicolor image by synthesizing a plurality of single color images, a plurality of developing devices loaded with monochromatic toner are arranged around the periphery of the photoconductor drum, and one rotation of the photoconductor drum is performed. A latent image corresponding to each color formed for each color is developed in a non-contact manner, and a multi-color toner image is formed by rotating the photosensitive drum a plurality of times. In such an image forming apparatus, it is necessary to accurately align the positions of the toner images each time the monochromatic toner images are superposed. Therefore, in order to detect the position information of the photoconductor drum, the multicolor image forming apparatus is provided with an encoder disk or the like. Since the encoder disk in this case does not need to generate fine pulses unlike the encoder of a normal image forming apparatus, the number of notches on the outer peripheral edge of the encoder disk is generally as small as 6 to 10 places. .

[Problems to be Solved by the Invention]

When the encoder disk having a small number of cutouts of 6 to 10 is used as described above, the image forming start position on the photosensitive drum is limited to the number of cutouts. In such a case, a difference in the frequency of light reception occurs on the photosensitive surface of the photoconductor drum, and the so-called light fatigue tendency is biased. Also, when an encoder disk with a small number of notches of 6 to 10 is used, the transfer start position on the photosensitive drum on the recording paper is similarly limited to the number of notches. The position where the recording paper collides with the photosensitive drum is limited. In such a case, there is a drawback that the degree of contamination of the surface of the photoconductor due to paper dust or the like from the edge of the recording paper may be uneven, or that the position of the collision may be limited, resulting in scratches at that position. I had one. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and in a rotation control device of an image forming apparatus that forms a multicolor toner image by superimposing a single color toner image, the light on the photosensitive surface due to a difference in light receiving frequency. Provided is a rotation control device in an image forming apparatus capable of extending the life of a photoconductor drum by preventing uneven distribution of fatigue, uneven distribution of paper dust on the photosensitive surface due to difference in collision frequency of recording paper, and scratches. The purpose is.

[Means for solving problems]

In the rotation control device of the image forming apparatus for controlling the rotation operation of the photoconductor drum by using the encoder disk having a plurality of cutouts on the outer peripheral edge, the above-mentioned object is that the image formation start position on the surface of the photoconductor drum is The rotation control device of the image forming apparatus is configured so that the position specified by the position specifying signal of the encoder disk can be arbitrarily changed. And preferably, the encoder disk is fixedly and releasably attached to the rotary shaft of the photoconductor drum by a clutch member so as to be achieved by a rotation control device of an image forming apparatus. More preferably, it is configured so that the minute idling time of the photosensitive drum until the image forming start signal after receiving the position designating signal of the photosensitive drum from the encoder disc can be arbitrarily changed. Is achieved by the rotation control device of the image forming apparatus.

【Example】

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings of FIGS. 1 to 4. First, the overall function of the multicolor image forming apparatus having the rotation control device of the present invention will be described with reference to FIG. In FIG. 2, A is a reading unit, B is a writing unit, C is an image forming unit, and D is a paper feeding unit. In the reading unit A, 1 is a platen glass,
The original 2 is placed on the platen glass 1. Manuscript 2
Is illuminated by fluorescent lights 5 and 6 provided on a carriage 4 moving on a slide rail 3. The movable mirror unit 8 is provided with mirrors 9a and 9b, moves on the slide rail 3, and in combination with the first mirror 7 provided on the carriage 4, the optical image of the original 2 on the platen glass 1 is lensed. Lead to the reading unit 20. The image signal is subjected to signal processing in the signal processing unit of the reading unit A, a color signal that is color-separated according to the color of the toner described below is output, and is input to the writing unit B. In the writing unit B, the laser beam generated by the semiconductor laser is rotationally scanned by the polygon mirror 32 rotated by the drive motor 30, passes through the Fθ lens 36, and is reflected by the reflecting mirror.
The optical path is bent by 37 and projected onto the surface of the photosensitive drum 40 to form a bright line. When the scanning is started, the beam is modulated by the first color signal, and the modulated beam scans on the photosensitive drum 40 which is previously uniformly charged by the charger 41. Then, a latent image corresponding to the first color is formed on the surface of the photosensitive drum. This latent image is developed by, for example, the developing device 43 loaded with red toner, and a red toner image is formed on the surface of the photosensitive drum. The obtained toner image, while being held on the surface of the photoconductor, passes under the cleaning device 70 which is separated and retracted from the surface of the photoconductor, and enters the next copy cycle. The photoconductor drum 40 is uniformly charged by the charger 41. Then, the second color signal output from the signal processing unit is input to the writing unit B, and writing is performed on the surface of the photoconductor to form a latent image in the same manner as in the case of the first color signal. . This latent image is developed by the developing device 44 loaded with the second color, for example, blue toner. This blue toner image is formed on the already formed red toner image on the surface of the photoreceptor. Reference numeral 45 denotes a developing device having black toner, which forms a black toner image on the surface of the photoconductor based on a control signal generated by the signal processing unit. AC and DC bias voltages are applied to the developing sleeves of these developing units 43, 44, and 45, jumping development is performed by a two-component developer, and development is performed in a non-contact manner with the grounded photosensitive drum 40. . The toner image developed by the first color signal, the toner image developed by the second color signal, and the toner image developed by the black toner image are superimposed on each other, and the image thus superposed is fed by the transfer pole 50 to the sheet feeding unit. It is transferred onto the recording paper 61 which is a transfer body sent by the feeding belt 62 and the feeding roller 63. The recording paper onto which the toner image has been transferred is separated from the photosensitive drum by the separating electrode 51, and is further conveyed to the fixing device 53 to be fixed and a multicolor hard copy is obtained. FIG. 1 is a perspective view showing an embodiment of a rotation control device for a photosensitive drum according to the present invention. In the figure, 80 is an encoder disk having a plurality of cutouts 80A on the outer peripheral edge, 81 is an actuator having a locking claw 81A at the tip, 82 is a solenoid, 83 is an optical sensor such as a photo interrupter, and 84 is a solenoid 82. And actuator 81
85 is a release spring for urging the actuator 81, 86 is a toothed belt for rotating the photosensitive drum 40, and 87 is an encoder disk 80 for the photosensitive drum 40.
G1 is a toothed pulley that acts on the rotating shaft 40A in a fixed or released state. The encoder disk 80 is integrally formed with the sponge clutch 87 and is loosely fitted on the rotary shaft 40A of the photosensitive drum 40.
This encoder disk 80 has 6 to 10 notches 80A
In order to allow the detection unit consisting of the light emitting means and the light receiving means of the optical sensor 83 to detect the cutout portion 80A, the optical sensor 83 is laid on the encoder disk 80 in a non-contact state. There is. The spring clutch 87 includes a frame body 87C having a plurality of claw portions 87A on the outer peripheral surface thereof, and a clutch spring 87B having one end fixed to the inner wall of the frame body 87C. The clutch spring 87B is wound around the rotary shaft 40A and is in a loosely tightened state. The winding direction of the clutch spring 87B with respect to the rotating shaft 40A is wound inward from the end of the rotating shaft 40A in the direction opposite to the rotating direction of the photosensitive drum 40. Therefore, the spring clutch 87 is the locking claw portion of the actuator 81.
When 81A engages with the claw portion 87A and stops, the clutch spring 87B in the loosely tightened state spreads on the rotary shaft 40A and releases the rotary shaft 40A. When the actuator 81 does not operate with respect to the spring clutch 87, the clutch spring 87B loosely fastened to the rotary shaft 40A rotates together with the rotary shaft 40A. The release spring 85 constantly biases the actuator 81 in a direction to release the operation from the spring clutch 87. The solenoid 82 is controlled to operate for an arbitrary time at the end of copying a certain amount (for example, 100 sheets). The control of this operation is performed by a main body control device (not shown).
81 is pulled by the continuous rod 84 to engage the locking claw portion 81A with the claw portion 87A. The toothed pulley G1 is fixed to the rotating shaft 40A and transmits the rotational driving force of the toothed belt 86 to the photoconductor drum 40. The configuration of the present embodiment is as described above, and its operation will be described below. The encoder disk 80 is fixed to the rotary shaft 40A of the photosensitive drum 40 via a spring clutch 87. The clutch spring 87B is fixed to the rotating shaft 40A in a loosely tightened state. This loosely tightened state is adjusted so that the clutch spring 87B and the rotating shaft 40A do not slip during normal rotation. In this way, the encoder disk 80 that rotates together with the photosensitive drum 40 can provide position information of the photosensitive drum 40. When the cutout portion 80A of the encoder disk 80 passes the detection portion of the optical sensor 83, information on the corresponding position of the photosensitive drum 40 to that is transmitted. The image forming process is controlled based on the signal thus detected. The actuator 81 is normally released from the spring clutch 87 by a release spring 85. solenoid
When the actuator 81 is actuated and the actuator 81 is pulled by the connecting rod 84, the actuator 81 moves against the release spring 85, and the locking claw portion 81A engages with the claw portion 87A and is formed integrally with the spring clutch 87. The encoder disc 80 stops. At this time, the clutch spring 87B is fixed to the inner wall of the frame body 87C and therefore stops rotating. Then, the entire inner circumference of the sprig length receives frictional force from the rotary shaft 40A. However, since the direction of this frictional force is opposite to the winding direction of the clutch spring 87B and acts to widen the inner diameter of the clutch spring 87B, the rotating shaft 40A is released from the clutch spring 87B, and the photosensitive drum 40 is The rotation continues and the encoder disk 80 stops. The solenoid 82 is controlled to operate for an arbitrary time at the end of copying a certain amount (for example, 100 sheets). The control of this operation is performed by a main body control device (not shown). It is preferable that the operation time of the solenoid 82 is set at random through a random number generator or the like. In this way, if the solenoid 82 is operated for an arbitrary time, the image forming start position on the surface of the photosensitive drum is arbitrarily changed with respect to the starting position designated by the starting position designation signal from the encoder disc. As a result, unevenness such as light fatigue, paper dust adhesion, and scratches on the surface of the photosensitive drum can be prevented. Further, as another embodiment, regardless of the mechanical method as described above, a minute photosensitive drum from the reception of the starting position designation signal of the photosensitive drum to the image formation start signal from the encoder disc. The same effect can be obtained by arbitrarily changing the idling time by a main body control device (not shown). FIG. 3 shows the time chart, and FIG. 4 shows an example of the flowchart. When the interruption of the drum index occurs, it is judged whether it is the first color of the first sheet, a random number is generated only when it is the first color of the first sheet, and the delay time ti is determined. The time ti is valid until the completion of a series of copying and is the time from the drum index interrupt to the optical scanning start signal. Since the delay time based on the random number is set in this way, the image forming start position on the surface of the photosensitive drum is arbitrarily changed. Therefore, even with this method, it is possible to prevent unevenness such as light fatigue on the surface of the photosensitive drum and occurrence of scratches due to paper dust. In the former of the two embodiments described above, the encoder disk is stopped, only the photosensitive drum is idle, and then the image formation is started by the position specification signal of the encoder disk. In the latter case, when the drum index and the photosensitive drum are separate members, after the position designation signal is input, the image formation is started after the delay time has elapsed and the rotation continues while being integrally synchronized according to the flow shown in FIG. It is configured to. Particularly in the latter case, when the delay time is restricted by the diameter of the photosensitive drum or the size of the transfer paper, it is possible to arbitrarily set a random number corresponding to it. Further, although the color image forming apparatus by laser writing has been described in the above embodiments, the present invention is not limited to laser writing but may be applied to an image forming apparatus or a monochrome image forming apparatus that directly uses optical scanning for reading an original as image exposure on a photoconductor. It goes without saying that it is also applicable. However, in an image forming apparatus that superimposes toner images on the photosensitive drum by a plurality of rotations of the photosensitive drum as described in the embodiments, particularly accurate alignment is performed, and the image forming start position is arbitrarily set as necessary. Since the distance can be shifted by, the effect of using the device of the present invention was remarkable.

【The invention's effect】

By the rotation control device of the image forming apparatus of the present invention, the image forming start position designated by the encoder disk is no longer limited on the surface of the photosensitive drum, and the light fatigue of the surface of the photosensitive drum,
It is possible to prevent uneven distribution such as paper dust adhesion and scratches.
It has become possible to provide a rotation control device for an image forming apparatus that extends the life of the photosensitive drum.

[Brief description of drawings]

FIG. 1 is a perspective view of a rotation control device in an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a block diagram of a multicolor image forming apparatus, and FIG. 3 is a timing chart of another embodiment of the present invention. FIG. 4 is a flowchart thereof. 40 ... Photosensitive drum, 40A ... Rotating shaft 80 ... Encoder disk, 80A ... Notch 81 ... Actuator, 82 ... Solenoid 83 ... Optical sensor, 84 ... Connecting rod 85 ... Release spring , 86 …… Toothed belt 87 …… Spring clutch (clutch member) G1 …… Toothed pulley

Claims (3)

[Claims] 1. A rotation control device for an image forming apparatus, wherein an encoder disk having a plurality of cutouts on its outer peripheral edge is used to control the rotation operation of a photoconductor drum. Is configured so that it can be arbitrarily changed with respect to the position designated by the position designation signal from the encoder disc. 2. The rotation of the image forming apparatus according to claim 1, wherein the encoder disk is fixedly and releasably attached to a rotary shaft of the photosensitive drum by a clutch member. Control device. 3. A slight idling time of the photosensitive drum up to an image formation start signal after receiving the position specifying signal of the photosensitive drum from the encoder disk is arbitrarily changeable. The rotation control device for an image forming apparatus according to claim 1, wherein: