JPS6323466A - Picture forming device - Google Patents

Abstract

PURPOSE:To prevent the deviation of a picture in case of multiple recording by changing scanning speed magnifications in main scanning/subscanning directions of an original read means independently at the time of each picture recording. CONSTITUTION:A VIDEO signal with a different magnification from that at a 1st time is transferred from a reader section R to a printer section P in a 2nd recording. In storing known degrees of paper shrinkage alpha in advance, the scanning speed v2 of the optical system at the 2nd recording is expressed as v2=v1/alpha and the clock rate f2 is expressed as f2=alphafl, where v1 is the scanning speed of the optical system at 1st recording and f1 is the clock rate at the 1st recording. Furthermore, let the turning speed of a photosensitive drum 7 be (v) and the scanning speed magnification A in the sub scanning direction is expressed as A=v/v1. Thus, the deviation of the picture at every recording due to the shrinkage of the paper in case of multiple recording is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multi-m image forming apparatus that forms images multiple times on the same sheet of paper to obtain one composite image.

(Prior Art) A plurality of color developing units are provided, and image formation (or recording, or printing, hereinafter referred to as recording) is performed multiple times on the same sheet of paper by switching the respective developing units, and each recording is performed multiple times on the same sheet of paper. In this type of multi-recording image forming apparatus, which obtains one composite image on the cut paper by fixing each image on the cut paper, for example, a method such as an electrophotographic method in which images transferred onto the paper are thermally bonded is used. If the paper passes through a fixing device for a second time, the heat of the fixing device evaporates the moisture contained in the paper, causing the paper to shrink.

Further, when the fixing method is a method using pressure fixing using a roller or the like, the fixing process causes minute changes (shrinkage/stretching) of the paper, such as stretching of the paper due to the rolling force.

[Problem to be solved by the invention 3 In the above situations, when performing multiple recording, the second
There was a drawback in that the images from the first time onward were misaligned on the paper surface due to the paper change.

The present invention has been made by focusing on the problems of the conventional example as described above, and aims to provide an image forming apparatus of this type having a function of preventing image shift during multiple writing 2j. .

[Means for solving problems]

Therefore, in the present invention, the scanning speed magnification in the main scanning/sub-scanning direction of the original reading means is adjusted for each image recording time.
The purpose is to achieve the above object by configuring it so that it can be changed independently.

[Effect]

With the above configuration, it is possible to minimize the deviation of each rotated image due to changes in paper expansion and contraction during multiple recording.

C Example] The present invention will be described below based on Examples. FIG. 1 shows a schematic diagram of the configuration of an embodiment of a digital copying machine according to the principles of the present invention. This figure shows an example of an electrostatographic digital copying machine that forms an original image on a CCD (charge-coupled device), reads it, converts it into an electrical signal, and records this signal using a laser beam printer. (Structure) This copying machine consists of a reader section R that reads a document, and a printer section P that records an image. In the reader R, the return light from the original on the original platen 23 irradiated by the original illumination lamp 17 is reflected by the reflection mirror 18 and formed into an image on the COD unit 19 (including the processing circuit) via the imaging lens 25. and convert it into an electrical signal. After passing through the processing circuit, this electrical signal transfers the VIDEO signal to the printer section P via the relay connector 20.

In the printer section P, the VIDEO signal is modulated, and a laser drive circuit 21 sends light from a semiconductor laser 16 through a rotating polygon mirror 15 and a reflecting mirror 6.
The photosensitive (body) drum 7 is irradiated with light. 14 indicates a beam detector.

Thereafter, recording/printing is performed on the paper using a transfer agent such as toner using a known process. Note that 1 is a paper feed cassette, 2 and 24 are paper feed rollers, 3.12 is a conveyance roller, and 4
1 is a registration roller, 5 is a developing device, 8 is a primary charger, 9 is a transfer charger, 10 is a fixing roller, 11 is a paper path selector, and 13 is an intermediate tray.

(Operation) First, in the -th recording, the paper that has passed the fixing roller 10 is reversed and conveyed in the direction of arrow a by the paper path selector 11, and is temporarily stored on the intermediate tray 13.

Next, in the second recording, from the leader section R,
VIDEO signals with different magnifications are transferred and
In this case, the first time 3 stored in the intermediate tray 13
The paper on which self-recording has been completed is passed through the paper feed roller 24, double recording is performed by a known process, and then the paper is transferred to the fixing roller 10.
The paper that has passed through again is sent toward the conveyance rollers 12, and is configured to be ejected into the print tray 22.

(Magnification Variation Method) Next, the magnification variation method for the above-mentioned "second" recording will be explained based on the magnification variation means block diagram in the soda section P in FIG.

The scaling factor at this time is calculated as follows.

Namely, known paper relations! The I rate α is memorized in advance, and the scanning speed of the optical system at the time of the first recording is set to V.
l, and the clock rate is f, then the scanning speed of the optical system during the second recording ■2 is V 2 '' V 1
/α, and the clock rate f2 is f2=αf. Note that the rotational speed (or circumferential speed) of the photosensitive drum 7
, and the scanning speed magnification in the sub-scanning direction is A, then A =
It is given by v/v, and the drum rotational speed (■) and the optical system scanning speed (■1) at the time of the first recording are the same, so to speak, they are equal in magnification.

In Figure 2, DRc is a CCD driver circuit, DRs
is a sequence driver circuit. The basic concept of variable magnification is to make the speed of the DCC thermomotor 37d variable in the sub-scanning direction. The CPU calculates the speed based on the magnification corresponding to the expansion/contraction ratio stored in advance, and further calculates the PLL (phase locked loop) frequency corresponding to the speed and scans it to the T10 latch (1) 58.
A certain fixed value is set for the return trip, and the optical system returns at high speed.This is done by the CPU.
The value stored in the ROM is this ■/○ latch (+) 58
This is done by presetting to . Therefore, when enlarging the image twice, it is moved at the same speed as when it is the same size, and when it is reduced to A, it is moved at twice the speed. The main scan is
This method samples the serial signal (after A/D conversion) of the CCD 19 that is output at a constant frequency at a clock rate that corresponds to the magnification. For example, when enlarging by 2 times, sampling at a clock rate twice the CCD clock rate means that for 1 bit of source information, data can be obtained by increasing by 1 bit. When scaling down by %, sampling at a clock rate twice the CCD clock rate. By sampling at the station clock rate, data obtained by thinning out 1 bit for every 2 bits of source information can be obtained. The CPU calculates this clock rate based on the magnification corresponding to the expansion/contraction rate, and sets it in the T10 latch (2) 50 before starting the sub-scanning. The CCD 19 has a 2628-bit configuration, including 36 dummy bits and 2592 effective bits. The driving frequency is 7.569 KH2, and the signal line φ is the clock line 55. The clock for scaling is a VCO (voltage controlled oscillator) based on the same source oscillation as φ1 and the value of T10 latch (2) 50.
The frequency oscillated by 49 is synchronized with PLL48 and φ2
This forms a variable frequency.

A 2592-bit analog signal output from the CCD 19 is amplified by an AMP 42 and applied to an AGC (automatic gain control circuit) 43. The AGC 43 detects the white level because the white level changes due to long-term changes in the light intensity of the fluorescent lamp, the background of the document, etc., and clamps the white level so that the relative change is applied to the A/D converter 44. This is a circuit that does this. The output of the AGC 43 is A/D converted at 44 and converted into 6-bit parallel bits which are binary.

Next is the φ11 circuit of 45, but since the conversion time due to A/D conversion differs depending on each bit, it is latched again by φ to synchronize. Also, of course,
The address counter of the shift memory 57-1, 57-2 is operated by the φ2 clock. As a result of the above, the shift memory 57-1.57-2 can hold 2592 bits when the data is the same size, 1296 bits when the data is multiplied by %, and 5184 bits when the data is multiplied by 2.

The speed of the sub-scanning DC motor 37d is set by T10 latch in the CPU. (1) The value preset in 58 is manually input to the VCO 59, and the oscillation frequency caused by kneading is synchronized with the source oscillation and PLL 60 and applied to the surf circuit 61. It is controlled by.

By the above-described operation, the deviation between the first and second recorded images is substantially minimized, and the quality of the two images is improved.

(Other Embodiments) In the above-mentioned embodiments, in a system in which a leading margin is provided, a mechanism for better preventing printing misalignment by changing the timing of forming the leading margin between the first printing and the second printing. state

FIG. 3 is a diagram showing the positional relationship between the photosensitive drum and the registration roller, FIG. 4 is a timing chart of each signal, and FIG. 5 is a diagram showing the control signal relationship between the printer section and the reader section.

First, by turning on the power, it enters the standby state, and after the standby is finished,
The printer section P sends a ready signal (RDY) to the reader section R to inform it that it is ready for printing. When the reader section R receives the RDY signal, it issues a print command (PRNT).
Send to printer section P. Upon receipt of the PRNT signal, the pre-rotation sequence begins. When the pre-rotation sequence is completed, the printer section P sends a vertical synchronization request signal (VSREQ) to the reader section R. When the reader section R receives the VSREQ signal, it sends a vertical synchronization signal (VSYNC) to the printer section P. When the printer section P receives the VSYNC signal, it starts a printing sequence.

The reader section R receives a horizontal synchronization signal (BD
, BD: differential signal), horizontal synchronization signal, and VSYN
A video signal (VDO') synchronized with C.

VDO: differential signal) is sent to the printer section P.

Then, the semiconductor laser 16 is turned on together with this video signal,
Turn off.

Here, the time from when the reader section R outputs the VSYNC signal to when it outputs the next video signal is made constant. VS
The time from when the YNC signal is output until the registration roller 4 starts moving is changed between the first printing and the second printing.

First, let Tv (constant) be the time from when the VSYNC signal is output to when the video signal is output, and the - time from the VSYNC signal until the registration roller 4 moves during the first printing.
Let it be TR□.

In Fig. 3, the length from the laser irradiation position on the photosensitive drum 7 to the transfer position is 10 cm], the length from the registration roller 4 to the transfer position is X (+nm), and the paper conveyance speed is V.
(mm/sec), the length of the tip margin is Y (mm)
, where α is the rate of thermal contraction due to the first printing, it is expressed as follows. Therefore, the paper feeding timing drives the registration rollers 4 based on TR1. As a result, the paper is conveyed in synchronization with the image on the photosensitive drum 7, and the image is printed at a predetermined position.

However, if the second printing is done at the TRI timing (
1-α) Printing deviation of Y (mm) occurs. Therefore, the time TR□ from the VSYNC signal to the drive of the registration roller 4 at the time of second printing may be set. This eliminates printing misalignment.

In the above embodiment, the time from when the VSYNC signal is output to when the video signal is output is constant, but here, the VSYNC
The time from the signal to drive the registration roller 4 is constant (TR
). The time from when the VSYNC signal is output from the soda section R to when the video signal is output is determined separately for the first and second printing based on the expansion/contraction ratio of the paper, the position of the document, and the speed of the optical system. TVI (Se
c,), then it becomes.

Further, Tv2 at the time of second printing is sufficient. As a result, the first printing and the second printing start coincide with each other.

Note that with this method, it is only necessary to change the timing of sending the video signal from the reader section R between the first printing and the second printing, and there is no change on the printer section P side.

In addition, in the case of - writing, the first printing and the second printing,
By shifting the timing of image formation, it becomes possible to achieve better results.

In the above embodiments, an example of application to a digital copying machine capable of overlapping recording of two colors has been described; however, the present invention is not limited to only a digital copying machine, but can also be applied to a multiplex digital copying machine capable of recording three or more colors. can do.

Further, the printer is not limited to the laser beam printer in the above embodiments, and may be, for example, an LED printer.
, an LCD printer, or an ion radiation printer.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to minimize image distortion during multiple recording in an image forming apparatus.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration of an embodiment of a digital copying machine according to the present invention, FIG. 2 is a block diagram of a magnification variable means in the reader section, and FIG. 3 is a diagram showing the positional relationship between the photosensitive drum and the registration roller. 4 is a diagram showing the once-time mark of each signal timing, and FIG. 5 is a diagram showing the relationship between the control signals of the reader and the printer. 7...Photosensitive drum 10...Fixed roller tS-...Semiconductor laser 19--COD unit 23...Original platen P...-Printer Section (image recording means) R-...
・Soda part (manuscript reading means) α...Paper expansion/contraction rate Soda foot 0992g Darkness ρ Arrival 1 I w/1 Blind number Listen I Genealogy Figure 5

Claims (2)

[Claims] (1) In an image forming apparatus having an output means for reading a document with a light receiving element, converting it into an electrical signal, and converting the electrical signal into an image, and having a multiplex recording function, each recording time of the multiplex recording is provided. An image forming apparatus characterized in that the image forming apparatus comprises means for independently changing the scanning speed magnification of the document reading means in the main scanning and sub-scanning directions. (2) The image forming apparatus according to claim 1, wherein the scanning speed magnification change in the main scanning direction and the sub-scanning direction is performed in accordance with a predetermined expansion/contraction ratio of the paper.