JPH0519144B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention involves changing the exposure position by adjusting the position of an exposure mirror according to the position of the transfer drum or photosensitive drum when the scanning system reaches a predetermined position. The present invention relates, for example, to an exposure position control device for a copying machine that prevents misalignment of multiple transfer images.

(Prior Art) A conventional multi-transfer copying machine, for example, scans the surface of a document multiple times (for example, three times for the three primary colors of red, green, and blue) and performs the same number of charging steps, exposure steps, and development steps. There is a method that obtains a transferred image through a transfer process and then fixes it to obtain a single copy. This multiple transfer type copying machine is equipped with mechanical synchronization means such as a cam to synchronize the operations of the scanning system, photosensitive drum, and transfer drum. We are trying to prevent this from occurring.

However, in conventional multi-transfer type copying machines, the scanning system, photosensitive drum, and transfer drum are synchronized using mechanical synchronization means such as cams, so the device itself The structure becomes complicated, and as a result, it becomes difficult to always maintain a predetermined accuracy due to mechanical play and the like. For example, even if the first scan a and the second scan b start at the same time t ₁ as shown in FIG.
Since the rising speed of the scanning system is not constant, a difference of (x ₂ -x ₁ ) occurs in the displacement x of the scanning system at time t ₂ as shown in FIG. 1B. As a result, since the photosensitive drum is moving at a substantially constant speed _V1 as shown in Fig. 1C, there is a shift in the exposure on the photosensitive drum during scans a and b, which causes a shift in the weight of the multiple transfer images. occurs. In addition, in FIG. 1B, the influence on the amount of displacement of the scanning system caused by overshoot that occurs until the scanning system reaches a constant speed upon startup is ignored. Also, since the scanning speed must be changed when changing the magnification,
This has the disadvantage that the device becomes even more complicated and larger. In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 13740/1983 discloses a method for preventing misalignment of color separated images on the photoreceptor in a multi-overlap copying machine and improving the actual copy image. be.

In this copying machine, the original color separation image is formed in order to correct the deviation of the color separation image caused by the machining accuracy of the component parts, specifically, the parallelism of the filter glass or the roundness of the photoreceptor. A predetermined number of color separation filters are sequentially moved onto the optical axis, and the angles formed between each filter surface and the optical axis are independently and variably adjusted.

However, even with such means, the deviation of the color separation images due to variations in the start-up speed of the scanning system in a multiple copying machine is not taken into consideration. In other words, this means only targets the machining accuracy of the components of the copying machine, such as the accuracy of the parallelism of the filter glass, and does not give any consideration to predicting or planning for variations in the start-up of the scanning system. Therefore, it is not possible to set the inclination angle of the filter to eliminate the poor accuracy that occurs at startup.

(Objects and Structure of the Invention) The present invention has been made in view of the above-mentioned problems, and does not cause the apparatus to become complicated or large in size, and also eliminates problems caused by variations in the start-up speed of the scanning system, for example.
A copying machine that changes the exposure position by adjusting the position of the exposure mirror according to the position of the transfer drum or photosensitive drum when the scanning system reaches a predetermined position, in order to prevent the weight of multiple transferred images from shifting. The present invention provides an exposure position control device for use in the present invention.

Hereinafter, the exposure position control device for a copying machine according to the present invention will be explained in detail.

(Embodiment) Figures 2 and 3 A, B, and C show an embodiment of the present invention, in which a platen 2 on which a document 1 is placed is provided at the top of the copying machine, and a platen 2 on which the document 1 is placed at the bottom. scanning system 4 (light source lamp 4a, mirror 4b, 4
A light source lamp 4a and a mirror 4b are mounted on a carriage 5). As is clear from FIG. 3A, a sensor actuator 6 is provided at one end of the carriage 5, and a photo sensor consisting of a light emitting diode 7 and a phototransistor 8 is installed at a predetermined position in the passage through which the sensor actuator 6 passes. 9 is fixed. In addition, the scanning system 4
A photosensitive drum 12 that is exposed to scanning light is provided below the transfer unit 12a.
It is in contact with As shown in FIG. 3B, the transfer drum 13 is provided with a sensor actuator 17 on its outer periphery, which engages with a photo sensor 20 consisting of a light emitting diode 18 and a phototransistor 19 to generate a command signal for instructing the start of calculation of the number of pulses. output.
Further, the drive shaft 14 of the transfer drum is provided with a pulse generator 35 that outputs pulses in accordance with the rotation of the transfer drum 13. In addition to the above configuration, a paper feed tray 22 is provided to supply copy paper 21 to the transfer section 12a, and a charging corotron 23 and an exposure slit 2 are provided around the photosensitive drum 2.
4, and a developing section 25 for developing the electrostatic latent image on the photosensitive drum 12 (magenta, yellow-cyan developing sections 25a, 25 corresponding to green, blue, and red).
b, 25c) and a cleaner 27 for removing toner from the photosensitive drum 12 after transfer. Further, the aforementioned mirror 4e is fixed to a mirror carriage 28 which is rotated by a rotary shaft 29, as shown in FIG.
A gear 30 is fixed to 9, the gear 30 meshes with a worm gear 31, and the worm gear 31 is connected to a step motor 33 via a shaft 32. Furthermore, a transport belt 34 and a fixing section 35 are provided downstream of the transfer section 12a, and a control section 36 (for example, a microcomputer) for controlling the operation of the copying machine is provided. The control unit 36 has an input interface 36 that inputs sensor signals from various sensors (including photo sensors 9 and 20) in the copying machine or operation command signals from a console (not shown).
a, a ROM 36b that stores programs necessary for arithmetic processing of input signals, a CPU 36c that performs predetermined calculations based on the program, a RAM 36d that temporarily stores calculation results and data, and a copying machine that stores the calculation results and data. The output interface 36e outputs control signals to various controlled objects (including the light source lamp 7 and the step motor 33) or to a display section of a console (not shown).

To explain the operation in the above configuration,
After placing the original 1 on the platen 2, turn on the start key (not shown) on the console (not shown), and the scanning system 4 will move rightward from the home position at the left end of the figure under the control of the control unit 36. start moving,
Scanning of the document surface is started from the time when the edge of the document is reached. The adjustment of the exposure position according to the present invention is performed after the transfer drum 13 reaches a predetermined position of the photosensor 20 (t ₁ ), and after the scanning system starts moving and reaches a predetermined position of the photosensor 9 (t 1 ). _t2 ). Therefore, depending on the amount by which the photoreceptor or the transfer means moves during the time from when the photosensor 20 disposed on the transfer drum turns on (t ₁ ) until the photosensor 9 disposed on the scanning system turns on (t ₂ ). The angle of the exposure mirror 4e is adjusted accordingly. By doing this, it is possible to eliminate misalignment over the entire exposed image. During the first document scanning, a green filter (not shown) is placed in the optical path, and the photosensitive drum 1
2 is exposed by the green component in the scanning light. The developing section 25a develops the latent image resulting from the exposure using magenta toner, and the developed image is transferred to the copy paper 21 fed from the paper feed tray 22 and held by the transfer drum 13 at the transfer section 12a.
Thereafter, when the second document scan is performed, a blue filter (not shown) is placed in the optical path, and the photosensitive drum 12 is exposed to the blue component of the scanning light. The developing section 25b develops the latent image resulting from the exposure with yellow toner, and the copy paper 21 held by the transfer drum 13 is transferred to the transfer section 12.
Receives transcription at a. Finally, when the third document scan is performed, a red filter (not shown) is placed in the optical path and the photosensitive drum 12 is exposed to the red component in the scanning light. A developing section 25c develops a latent image based on this exposure using cyan toner,
The copy paper 21 with this developed image still gripped by the transfer drum 13 undergoes the final transfer. Below, the fourth
The control of the exposure mirror 4e will be explained in detail with reference to Figures A, B, and C. FIG. 4A shows a case where the scanning system, transfer drum, and photosensitive drum are synchronized. Prior to the start of document scanning, when the transfer drum 13 rotates together with the photosensitive drum 12, the sensor actuator 17 provided on the transfer drum 13 blocks the light from the light emitting diode 18 and turns on the photosensor 20 (time t ₁ ). As a result, a pulse detection start signal is input to the control unit 30, and the pulse generator 35
The number of pulse signals is counted. Next, when the scanning system 4 has scanned a certain distance, the carriage 5
The sensor actuator 6 provided at one end blocks the light from the light emitting diode 7 and turns on the photo sensor 9 (time t ₂ ). When the photosensor 9 is turned on, the control unit 36 finishes counting the pulse signals, compares the counted value n with a predetermined value N,
Based on the determination that N=n, no control signal is output. Next, FIG. 4B shows a case where the scanning system 4 is ahead of schedule. Prior to the start of document scanning, when the transfer drum 13 rotates, counting of pulse signals is started when the photosensor 20 is turned on, and counting of pulse signals is ended when the photosensor 9 is turned on. The control section 36 compares the count value k with a predetermined value, and outputs a control signal according to the difference of N-k since k<N, and controls the mirror 4e via the step motor 33 before the document scanning starts. Instant clockwise rotation (based on positive control signal). FIG. 4C shows a case where the scanning system 4 is behind schedule, and since P>N when comparing the count value P with a predetermined value N, the mirror 4e is rotated counterclockwise (negative (based on control signals). As is clear from the above explanation, according to the present invention, the mirror 4e is displaced clockwise or counterclockwise by an angle θ to compensate for variations in the time (t ₂ ) until the scanning system reaches a predetermined position, thereby delaying or advancing the scanning. Corrects distortion and prevents image shift. Incidentally, the displacement of the mirror 4e is shown in the relationship shown in FIG. 4 as follows.

θ=1/2 tan ^-1 e/L where θ is the displacement angle of mirror 4e, and L is the displacement angle of mirror 4e.
The distance between e and the photosensitive drum 12, and e is the amount of displacement of the electrostatic latent image. Incidentally, sufficient correction can be made with e≦1.5 mm. Note that rotation adjustment is performed for each scan.

Although the above embodiments have been described as a registration correction device for a multi-transfer type copying machine, it is also possible to adjust the amount of deviation of the optical system that occurs during assembly.

(Effects of the Invention) As explained above, the exposure position control device for a copying machine according to the present invention adjusts the angle of the exposure mirror according to the position of the transfer drum or photosensitive drum when the scanning system reaches a predetermined position. Since the exposure position is changed by changing the exposure position, it is possible to avoid complicating or increasing the size of the device, and also to prevent deviations in the weight of multiple transfer images due to deviations in color separation images due to variations in the start-up speed of the scanning system. .

[Brief explanation of the drawing]

FIG. 1A is an explanatory diagram showing variations in the start-up of the scanning system. FIGS. 1B and 1C are explanatory diagrams showing the relationship between the timing of counting the number of pulses and the registration position.
FIG. 2 is an explanatory diagram showing the structure of the exposure position control device for a copying machine according to the present invention. FIG. 3A is an explanatory diagram showing a sensor actuator provided in the scanning system and a photo sensor that engages with it. FIG. 3B is an explanatory diagram showing a sensor actuator provided on the transfer drum and a sensor provided on the outer periphery of the transfer drum. FIG. 3C is an explanatory diagram showing a mirror displacement means. FIGS. 4A to 4C are time charts showing operations according to the present invention. Fifth
The figure is an explanatory diagram showing the relationship between the amount of rotation of the mirror and the amount of correction of the incident position on the photosensitive drum. Explanation of symbols, 1... Original, 2... Platen, 4... Scanning system, 5... Carriage, 6... Actuator for sensor, 9... Photo sensor, 12... Photosensitive drum, 12
a... Transfer section, 13... Transfer drum, 17... Sensor actuator, 20... Photo sensor, 21... Copy paper, 25... Developing section, 28... Mirror carriage, 29... Rotating shaft, 30... Gear, 31... Worm gear, 32 ...Shaft, 33...Step motor, 36...Control unit.

Claims (1)

[Scope of Claims] 1. A document is scanned by a scanning system, and the document image is exposed to a photoreceptor multiple times through an optical system composed of lenses, mirrors, etc., and each exposed document image is In a copying machine that performs multiple copies by repeating development and transfer, the mirror has rotational movement means for changing the exposure point on the photoreceptor in the moving direction of the photoreceptor, and the photoreceptor or the transfer means is predetermined. a command means for outputting a reference timing signal when the reference timing signal is outputted and the scanning system reaches the reference position of the scanning system; An exposure position control device for a copying machine, comprising: a detecting means; and a mirror control means for rotationally moving the mirror by a predetermined amount in accordance with the amount of movement detected by the detecting means.