JPH0429259A - Electrophotographic image forming device - Google Patents

Abstract

PURPOSE:To carrying out printing at a prescribed position regardless of the meandering of a cutform sheet by detecting the meandering of the cutform sheet before it reaches a transfer region, and moving a cylindrical lens so that a printing position in a scanning direction on the cutform sheet is in parallel to one side of the top end of the cutform sheet according to its meandering quantity. CONSTITUTION:The meandering of the cutform sheet 15 is detected by a meandering detecting sensor (L)10 serving also as a top sensor and a meandering detecting sensor (R) 11. Then, one end of a second cylindrical lens 19 is supported so as to be turned by a turn supporting part 20, and the second cylindrical lens 19 is driven by an eccentric cam 22, a spring 21, and a motor, so that the printing position in the main scanning direction of the cutform sheet 15 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrophotographic image forming apparatus that forms a printed image on a cut sheet.

[Background of the invention]

In an electrophotographic apparatus, an electrostatic latent image is formed by optical means on the surface of a photoreceptor that is charged by a charging mechanism that applies a predetermined charge to the surface of the photoreceptor coated or deposited on a conductor. . The electrostatic latent image is visualized by fine particles such as toner, and the toner is further transferred to the transfer material and then fixed onto the transfer material by a fixing device using a heat roll or the like, It is finally output as a printed matter or a copy.

Continuous form paper or single form paper is used as the transfer material, but in the case of continuous form paper, the feed holes provided on both sides of the continuous form paper are inserted into the tractor of the electrophotographic apparatus main body. Because the paper is held and fed by a paper feed mechanism called a paper feeder, stable paper feed is obtained.However, in the case of cut paper, it is transported by belts, rollers, etc., and the degree of freedom of movement of the paper in each direction is continuous. Because it is larger than paper,
Paper feeding becomes unstable. This instability led to the phenomenon that the paper sheets meandered and printing was not done in the correct position.

Here, a conventional example of how to determine a printing position in an electrophotographic apparatus using cut paper as a transfer material will be described. Note that the laser that is the light source of the latent image forming means will be described as a laser diode (LD) that can be directly switched.

In FIG. 5, a paper cut 15 is placed in a paper feeder 7, a microprocessor 3 receives a cut paper pickup signal from the control device 1 via an interface 2, and a pick-up roll 8 and a foot roll 9 are used to pick up the paper cut. The paper is sent to the transfer area 14 through the slip transport path 29. Cut paper 15
When the starting edge of the paper sheet 15 is detected by the top sensor 10, a vertical periodic signal DTP17 is sent from the microprocessor 3 to the control device 1 via the interface 2, and printing of the cut sheet 15 in the vertical direction starts as shown in FIG. Position (vertical period) 3
4 is determined.

Next, a method of determining the start of printing in the horizontal direction (horizontal period) will be explained. In FIG. 8, the laser diode 24
A laser beam 23 with a certain spread emitted from the laser beam 23 is turned into parallel light by a urimeter lens 25 and flattened by a first cylindrical lens 26 . The laser beam 23 is scanned by the scanner 27, and is quickly corrected by the fo lens 28, the second cylindrical lens 29, etc. to keep the surface tilt and the writing speed in the axial direction of the photoreceptor constant. The BD sensor 31 detects the laser beam 23 reflected from the BD mirror 30 every scan of the laser beam 23. This detection signal is transmitted from the microprocessor 3 to the control device 1 via the interface 2 as a horizontal periodic signal DBD32,
- The horizontal printing start position 35 (horizontal period) shown in FIG. 10 is determined. As shown in FIG. 9, the latent image writing signal from the control device 1 is passed through the microprocessor 3 using the above-mentioned vertical periodic signal and horizontal periodic signal as references,
By switching the laser diode 24 transmitted to the driver 33, an electrostatic latent image is formed on the photoreceptor 16 so as to print at a predetermined position on the cut paper 15.

However, in conventional electrophotographic image forming apparatuses that use cut paper, the image that is visualized at the correct position on the photoreceptor becomes distorted when transferred to the cut paper due to the above-mentioned meandering of the cut paper. As shown in FIG. 11, compared to the cut paper that was conveyed without meandering as shown by the dotted line, a problem occurred in which the paper was printed at a position deviated from the correct printing position.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a high-performance electrophotographic image forming apparatus that can print at a predetermined position regardless of the meandering of the cut paper.

[Summary of the invention]

The present invention focuses on the refractive power of the cylindrical lens, which has the ability to correct the printing position on the transfer object and correct the surface tilt by forming an electrostatic latent image in accordance with the meandering of the transfer object. A mechanism for detecting the meandering of the transferred object is provided, and the horizontal period of the control device and the latent image forming optical means are devised so that the electrostatic latent image is formed according to the signal from the detection mechanism. It was added.

[Embodiments of the invention]

A specific embodiment of the present invention will be described below with reference to FIGS. 1 to 4, and FIGS. 6 and 7.

In FIG. 1, the meandering of the cut paper 11 is detected by a meandering detection sensor (L) 10 which also serves as a top sensor and a meandering detection sensor (R) 1.
1 is detected. This detection signal is sent to the microprocessor 3, and the amount of meandering is detected by an arithmetic unit within the microprocessor 3. Detection of meandering amount will be explained in a little more detail.

As shown in FIG. 4, the meandering detection sensor (R) 10 and the meandering detection sensor (L) 11 are arranged at an interval of a distance Q(m+) in the direction perpendicular to the feeding direction of the cut paper 15. Therefore, the conveyance speed of the cut paper 15 is V (rm/sec), and the time from when the meandering detection sensor (R) 10 detects the paper to when the meandering detection sensor (L) 11 detects the paper is t( seconds) (Meandering detection sensor (L) 11 is better than Meandering detection sensor (R).
If paper is detected earlier than 10 seconds, it is set as -t (seconds).

), the meandering amount of the paper is tan(
vXt/Q).

According to the meandering amount, correction according to the present invention is applied so that printing is performed at a predetermined position even on the meandering cut paper 15.

As shown in FIG. 3, the second cylindrical lens 19 has a characteristic that when the incident position of the laser beam 23 is shifted by ΔQ in the sub-scanning direction, the laser beam converges on the surface of the photoreceptor 16 with a shift of ΔQ. Therefore, depending on the amount of meandering, for example, as shown in FIG. By driving the second cylindrical lens 19 in the direction of the arrow,
The print position of the cut sheet 15 in the main scanning direction is corrected.

With the method described above, the printing position in the main scanning direction is set at a predetermined position as shown in FIG. 6, but no correction is made in the sub-scanning direction.

This horizontal correction will be explained below.

As shown in FIG. 4, the cut paper 15 has a meandering angle of 0
With the point as the origin, it shifts in the X direction by an amount of X=Ysinθ. Therefore, if the horizontal writing start position is advanced (or delayed) by Ysino, printing will be performed at a predetermined position on the meandering cut paper 15. To explain specifically, if the scanning time of the laser beam is tr (seconds), the distance that the paper travels during tr (seconds) is tr (seconds) Xv (mm/second)
becomes. Therefore, every tr (seconds), the paper cut sheet 15 shifts by vXt rXs i n0 minutes compared to the case without meandering in the X direction, so this amount is given by the horizontal synchronization signal DBD32. Just do it earlier (or later) than when you start writing.

With this process, as shown in FIG. 7, it is possible to accurately print on the cut paper 15C without any deviation in printing position according to meandering.

In the embodiment described above, the cylindrical lens arranged to correct the surface tilt of the mirror motor was used as the printing position correction means in the main scanning direction, but in the optical system in which the cylindrical mirror is arranged, the cylindrical mirror is similarly used. I can do it.

In addition, in the above embodiment, a meandering correction mechanism was not provided on the sheet feeding system side, but a so-called resist mechanism that temporarily stops the sheet conveyed from the paper feeder and corrects the meandering there. A well-known meandering correction means such as meandering correction using a roller is disposed closer to the paper feeder than the meandering detection means, and after the meandering correction is performed, meandering is detected and the present invention is applied to achieve higher printing position accuracy. You can get it.

〔Effect of the invention〕

According to the present invention, since a latent image is formed according to the meandering of the cut paper, good printing position accuracy can be obtained. Furthermore, this allows the main body of the apparatus to have a large margin against meandering, thereby improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of an electrophotographic image forming apparatus showing an embodiment of the present invention, FIG. 2 is a schematic diagram of a cylindrical lens drive mechanism according to the present invention, and FIG. 3 is a diagram showing the refractive power of the cylindrical lens. FIG. 4 is an explanatory diagram for specifically explaining the present invention. FIGS. 6 and 7 are explanatory diagrams for explaining the effects of the present invention. Figure 8, 9th
FIG. 1 is a control circuit diagram of an electrophotographic image forming apparatus showing a conventional example, and FIGS. 10 and 11 are explanatory diagrams illustrating defects in the conventional technology. In the figure, 1 is a control device, and 7 is a paper feed device. 10 is a top sensor, 11 is a paper meandering detection sensor (L)
, 14 is a transfer area, 15 is a cut sheet, 16 is a photoreceptor, 18
19 is the meandering detection signal, 19 is the first cylindrical lens, and 2 is the meandering detection signal.
3 is a laser diode, 27 is a scanner, 28 is an fθ lens, 34 is a vertical print start position, and 35 is a horizontal print start position. Name of patent applicant Hitachi Koki Co., Ltd. Figure 11) Figure 4 and a half Figure 6) Figure 8 Figure 110 Figure Lz-A'A') Figure l1

Claims (1)

[Scope of Claims] 1. An optical means for forming a latent image on a photoreceptor of an electrophotographic image forming apparatus includes a laser, a scanning means for deflecting and scanning a laser beam emitted from the laser in a main scanning direction, and the scanning means The laser beam is composed of a lens system designed to move at a constant speed on the surface of the photoreceptor, and a cylindrical lens having a surface tilt correction ability, and the latent image forming optical means allows the laser beam to In an electrophotographic image forming apparatus that forms an electrostatic latent image on a body according to an image, develops it in a developing machine, and then transfers it to a cut paper that is a transfer material, a feeding device that supplies the cut paper is used. , a means for feeding the cut paper to the transfer area in response to a signal from a control device, and detecting meandering of the cut paper before the leading edge of the cut paper in the running direction reaches the transfer area; The detecting means determines the printing position in the scanning direction on the cut paper according to the detected meandering amount of the cut paper, regardless of the meandering of the cut paper. An electrophotographic image forming apparatus comprising means for moving the cylindrical lens so that it is parallel to one side of the cylindrical lens. 2. The meandering detection means is located at such a position that the time required for the cut paper to move from the detection means to the transfer area is longer than the time required from formation of the latent image on the photoreceptor to transfer; 2. The electrophotographic image forming apparatus according to claim 1, further comprising a sheet meandering correcting means located closer to the paper feeding device than the meandering detecting means. 3. The electrophotographic image forming apparatus according to claim 1, wherein the printing start position in the main scanning direction is corrected for each scan in accordance with the detection of the meandering amount of the cut paper.