JPH05193785A - Image forming device - Google Patents

Abstract

PURPOSE:To perform lateral register correction of recording through a simple device by providing a mark detecting means on the downstream of a register roller and feeding a paper sheet on which a lateral register mark extending obliquely in the feeding direction of a paper sheet is written. CONSTITUTION:A simple lateral register mark 14 extending obliquely in the feed direction of a recording paper sheet is written in the predetermined position of a sheet, for example, a recording sheet, such as a copy sheet, and a mark detecting means 12 for detecting the lateral register mark is provided. A time between the passage of the forward end of the recording paper sheet and the passage of the mark is measured by means of a mark detecting means 12 to calculate a difference between the measured time and a preset time, and a lateral register amount is determined according to the difference therebetween. By regulating a photo writing timing according to a lateral register amount, an image can be formed in the given position of a recording paper sheet. By forming the lateral register marks on both obverse and reverse of the recording paper sheet, even in the case of making records on both obverse and reverse, reliable correction can be effected only by regulating respective photo writing timings for the obverse and reverse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser printer, a facsimile or a copying machine, and more particularly to correction of lateral registration amount of a sheet of the image forming apparatus.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a laser printer, an image is not formed at a predetermined position on a recording sheet due to the lateral displacement of the sheet, and sometimes a part of the image is not formed on the sheet. In order to solve this problem, there is a problem in that the paper is not printed because it runs out of the paper. To solve this problem, for example, according to Japanese Patent Laid-Open No. 63-149670, a paper edge detecting means extending laterally in the paper passing direction is provided, It is known that the side edge of the image is detected and compared with the reference paper edge position in the paper size detected by the paper size detection means, and the image writing position on the photosensitive drum is corrected according to the deviation amount.

In the above-mentioned conventional image forming apparatus, it is necessary to be able to detect the side edge of the sheet of each size, and the structure of the sheet edge detecting means must be complicated or expensive means must be used. There was a problem in terms of economy.
Furthermore, although one-sided recording was considered, lateral registration amount correction at the time of double-sided recording was not considered at all, and when the conventional technical idea was applied to a device that enabled double-sided recording, the control device was only that much. There was a problem that it became complicated.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems of the prior art and provides an image forming apparatus capable of lateral registration correction for single-sided recording and double-sided recording with a simple and inexpensive apparatus. That is the issue.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention solves the above-mentioned problems by feeding a sheet fed from a sheet feeding device by a registration roller at a timing, and by writing by an optical writing means. In an image forming apparatus that transfers an image formed on a sheet, fixes it by a fixing device, and discharges the sheet, a sheet having a lateral registration mark provided diagonally with respect to the sheet feeding direction is provided with mark detection means downstream from the registration roller. Is fed, the time from the leading edge of the paper to the mark is measured based on the detection signal from the mark detecting means, the difference between the measured time and the preset time is calculated, and based on the calculated difference. This is solved by an image forming apparatus characterized in that the lateral resist amount is obtained and the optical writing timing to the image carrier is adjusted according to the lateral resist amount.

[0006]

According to the present invention, a simple lateral registration mark extending obliquely with respect to the feeding direction of the recording paper is attached to a predetermined position of the recording paper such as a transfer paper, and a mark for detecting the lateral registration mark. By providing the detecting means and measuring the time from the leading edge of the recording paper to the mark by the mark detecting means and calculating the difference from the preset time, the lateral resist amount is obtained according to the difference, and the optical writing means is used. The optical writing timing is adjusted according to the lateral resist amount, and an image can be formed at a predetermined position on the recording paper. By attaching horizontal registration marks on both the front and back sides of the recording paper, even in the case of front and back side recording, reliable horizontal registration correction can be performed simply by adjusting the optical writing timings on the front and back sides.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the embodiments shown in the drawings.

In FIG. 1, as an example of an image forming apparatus, in a laser printer 1 capable of double-sided recording, a laser beam based on an image signal is projected on an image carrier 2, for example, an OPC belt by a charger 3 after charging by an optical writing device 4. Form an electrostatic latent image of the image. The latent image is developed by the developing device 5 and visualized.

The sheet feeding device 6, for example, the first sheet feeding cassette 6a
The recording paper fed by the paper feed roller 7 from either the second paper feed cassette 6b or the second paper feed cassette 6b is fed by the conveyance path 8 to the registration roller pair 9
Be transported to.

The recording paper is separated from the paper feeding device 6 by a manual insertion portion 10.
It can also be fed by hand to the registration roller pair 9.

A registration sensor 11 is arranged on the upstream side of the registration roller pair 9 and a mark detection means 11 is arranged on the downstream side thereof to detect the leading edge of the sheet and the lateral registration mark on the sheet.

As the lateral registration mark, simple marks such as those shown in FIGS. 2 and 3 are formed on the paper by printing or the like. The direction of the straight line mark 14 can be selected from leftward descending or rightward descending as shown in the example of FIG. 3 and the example of FIG.

One lateral registration mark 14 may be provided at an appropriate position in the lateral direction of the recording paper 13 as shown in FIG.

As shown in FIG. 4, the lateral registration marks may be formed as two linear marks 14a and 14b which are symmetrical, for example, at two positions on the left and right with respect to the center of the recording paper 13 in the feeding direction. The two linear marks 14a and 14b may be marks that are in contact with each other at the paper edge as shown in the figure, or marks that are separated from each other. In this case, the mark detecting means 12
It is convenient to arrange symmetrically with respect to the center in the feeding direction as shown in FIG.

The recording paper is fed by the registration roller pair 9 at the same timing as the writing on the image carrier 2, and the image is transferred from the image carrier 2, for example, the photosensitive belt by the action of the transfer unit 15, and the fixing device 16 is provided. The sheet is fixed while passing through the sheet, passes through the sheet discharge sensor 17, and is discharged to the sheet discharge tray by the sheet discharge roller 18. The paper discharge sensor 17 detects a jam at the time of paper discharge.

When recording images on both the front and back sides of the recording paper, the paper is once stored in the double-sided paper feeding device 20 by the return path 19 branched from the paper discharge path to the paper discharge tray, and the reversing roller 21 is used.
Thus, the front and back can be reversed and the pair of registration rollers 9 can be conveyed through the double-sided paper feed path 22.

The image forming operation will be described with reference to the time chart shown in FIG.

The paper feed clutch is engaged to operate the feeding roller 7, the recording paper is conveyed, and the recording paper is detected by the registration sensor 11 and abuts on the rear registration roller pair 9. The leading edge of the recording paper comes into contact with the stopped registration roller pair 9, and the slack is given to the recording paper by feeding the feeding roller 7 for a predetermined time, and skew correction is performed. After the recording paper is slackened, the rear paper feed clutch is turned off and the paper feed roller 7 is stopped.

The recording sheet is transferred from the registration roller pair 9 to the transfer section 1
Generally, the optical writing is started before the registration sensor 11 detects the leading edge of the recording sheet due to the difference between the time for transporting the sheet to the photosensitive belt 2 and the time from the optical writing to the photosensitive belt 2 to the transfer section 15.

In the optical writing, the polygon mirror rotates the laser light by the rotation of a polygon motor (not shown) in the optical writing device 4 in the lateral direction (horizontal direction) with respect to the feeding direction on the recording paper.
First, the optical scanning is performed over an area corresponding to the width of the recording paper. DE, which is a horizontal scanning timing signal for each horizontal scanning
A TP signal is issued. Optical writing for each horizontal scanning is started with reference to the DETP signal. That is, when the optical writing time is reached, the DETP signal is generated, and after the predetermined time t _b has elapsed, the post-horizontal writing timing LGATE signal becomes valid. At the same time, vertical writing timing FG
The ATE signal is also valid. The time t _b is the optical writing device 4
And the reference position of the recording paper transport mechanism.

The time t _b can be changed and adjusted according to the correction amount of the lateral resist amount. In addition, in order to synchronize with the writing of the optical writing device 4, it is synchronized with the write clock WCLK. As an example, the time t _b allows a change of 30 pulse widths.

At the time of recording on the recording paper, the paper with the horizontal registration mark 14 is used as the first recording paper, or the paper with the horizontal registration mark is fed by the gist roller 9 prior to the recording, and the mark detection means ( By detecting the lateral registration mark 14 on the paper 13 by the mark sensor) 12, the time t _s (FIG. 2) from the leading edge of the paper to the detection of the lateral registration mark 14 is measured, and the preset time t _a (FIG. 2) is measured. It calculates a difference t _s -t _a between the detection time) when in the in the reference position indicated by broken lines. The lateral resist amount is obtained from the value of this difference.

DETP according to the lateral resist amount obtained
Adjusting the time interval t _b between the signal and the LGATE signal,
Correct the lateral registration amount. That is, the lateral resist correction is performed by adjusting the optical writing start time. The recording paper is not moved. An image is formed on the succeeding recording paper in a state where the lateral registration correction is performed.

When the time t _s can be changed by the width of 30 pulses, 30 pulses × (24.5 mm / inch / 300 dot / inch) = 2.45 mm, and the lateral resist amount of 2.45 mm can be corrected.

Two lateral registration marks 14 shown in FIG.
a and 14b and two mark detecting means 12 are provided, the reference time t _sR of the difference (t _cR −t _cL ) between the reading times t _cR and t _cL of the two lateral registration marks 14 a and 14 b, _{respectively.} , T _sL difference (t _sR −t _sL ), the difference value (t _cR −
t _cL ) − ( _tsR −t _sL ), and the lateral resist amount corresponding to the difference is calculated. In this case, it is not necessary to measure the time from the leading edge of the paper.

When recording on both sides of the recording paper, by adding the lateral registration marks 14 or 14a, 14b on both sides of the recording paper, the lateral registration correction can be easily and accurately performed on the respective surfaces by the above. There is no need to provide special equipment for both sides.

As an example of the control device, the configuration shown in FIG. 6 is used, and when the lateral resist amount is obtained, the amount can be stored in the readable / writable nonvolatile memory E ² PROM. . By storing the data in the E ² PROM, even if the power is turned off, the subsequent image formation can be performed under the stored lateral registration correction.

[0028]

According to the present invention, it is possible to easily make a correction so as to eliminate the lateral registration amount of the recording paper only by using the recording paper with the lateral registration mark.

When two lateral registration marks are provided, the correction can be made by directly detecting the marks, and the correction accuracy can be improved.

It is possible to correct the lateral resist amounts on both sides in exactly the same way as when only one side is recorded by simply applying lateral resist marks on both sides of the recording paper, so that the front and back sides can be accurately aligned. It is now possible to record images.

When each correction amount can be recorded in the nonvolatile memory, the correction amount is recorded even if the power is turned off once. Therefore, the same lateral registration correction can be maintained in subsequent image formation.

According to the present invention, when sheets of the same size are superposed and fed from the same sheet feeding device, the lateral registration mark is attached to the first sheet to obtain the lateral registration amount, and thereafter the feeding is performed. With respect to the paper apparatus, the same lateral registration correction can be performed, which simplifies the work and enables accurate lateral registration correction.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an example of an image forming apparatus according to the present invention.

FIG. 2 is a schematic view of an example of a lateral registration mark attached to a sheet.

FIG. 3 is a schematic view showing another example of a lateral registration mark.

FIG. 4 is a schematic view showing another example of a lateral registration mark.

FIG. 5 is an operation time chart of the image forming apparatus.

FIG. 6 is a configuration block diagram of an example of a control device.

[Explanation of symbols]

 1 Image Forming Device 2 Image Carrier 4 Optical Writing Device 6 Paper Feeding Device 9 Registration Roller Pair 10 Manual Feed Port 11 Registration Sensor 12 Mark Detection Means 13 Recording Paper 14 Horizontal Registration Marks 15 Transfer Section 16 Fixing Device 20 Double-sided Paper Feeding Device

Claims (4)

[Claims] 1. A sheet fed from a sheet feeding device is fed by a registration roller at a timing, an image formed on an image carrier is transferred based on writing by an optical writing unit, and fixed by a fixing device. In the image forming apparatus that discharges the sheet, the mark detecting means is provided downstream from the registration roller, and the sheet with the lateral registration mark extending obliquely to the sheet feeding direction is fed, and the detection signal by the mark detecting means is sent. Based on this, the time from the front edge of the paper to the mark is measured, the difference between the measured time and the preset time is calculated, and the lateral resist amount is calculated based on the calculated difference. The image forming apparatus is characterized in that the optical writing timing to the image carrier is adjusted. 2. The horizontal registration mark is provided at two places on the left and right with respect to the center of the sheet in the sheet feeding direction, and the mark detecting means is provided.
Individually arranged side by side in the paper feed direction, the difference between the detection times of the horizontal registration marks by the two mark detection means is measured, and the difference is compared with a preset time difference to obtain the lateral registration amount. The image forming apparatus according to claim 1, wherein the optical writing timing to the image forming apparatus carrier is adjusted according to the lateral resist amount. 3. The sheet after fixing is formed by reversing the front and back sides through a double-sided sheet feeding device so that it can be circulated and fed to a registration roller, and the lateral registration marks are provided on both front and back sides of the recording sheet, and the mark detecting means Measure the time from the front edge of the paper to the lateral registration mark on each of the front and back sides of the paper, calculate the difference between the measured time and the preset time, and obtain the lateral registration amount. The image forming apparatus according to claim 1, wherein the optical writing timing on the image carrier is adjusted on each of the front surface and the back surface. 4. The obtained lateral resist amount is stored in a readable / writable non-volatile memory.
The image forming apparatus according to any one of 3 above.