JPH01189667A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the accuracy of image positioning by calculating the registered starting timing at the time of centering according to the reference data and the amount of image movement. CONSTITUTION:To copy an original at the center of a copying paper, considering the image exposure as the reference the paper feeding start and the registered start are deviated the same amount as the image movement. When carrying out centering when copying, the mean value is obtained from data stored in a RAM 102, and this mean value is used as the reference. Thus by finding the registered starting time, the most appropriate registered timing for centering is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention can be applied to an image forming apparatus such as a copying machine having a centering mode.

[Prior art]

2. Description of the Related Art Conventionally, in a copying machine or the like, depending on the selection of original size, copying magnification, and transfer size, an image may be copied on one side of the transfer paper.

In order to avoid the above-mentioned problems, copying machines have been provided that are provided with a mode called a centering mode so that the image is transferred to the center of the transfer paper.

However, when such image movement is performed, depending on the timing, it is necessary to perform transfer positioning before image exposure, so the transfer paper is normally stopped at the registration position during copying, and then after image exposure starts. , it is not possible to control the positioning of the image on the photoreceptor and the transfer paper by starting the registration after the scanner reaches constant speed movement.

When moving the image, when the registration start and exposure start are reversed, the control includes periods with large variations such as the scanner run-up period and acceleration period, making it difficult to achieve image position accuracy and reducing the difference between devices. was big.

Furthermore, it was not possible to adjust the image position during centering using normal registration adjustment.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that improves image position accuracy during centering.

〔composition〕

In order to achieve the above object, the present invention provides an image forming apparatus having a centering mode in which the image forming position on transfer paper is varied and an image of a document is transferred to the center of the transfer paper, and a transfer mode in which no centering operation is performed. a sampling means for sampling the registration start timing at the time; a calculation means for calculating reference data for centering operation from the sampled timing data;
The present invention is characterized by comprising a calculation means for calculating registration start timing during centering in accordance with the reference data and the amount of image movement.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

FIG. 1 is a front view showing a copying apparatus to which the present invention can be applied. In the figure, this copying device includes a copying device main body,
ADF (automatic document feeder/discharge device) 6o.

Sorter 70. Automatic double-sided processing unit 1-80. It consists of a group of optional units such as a paper feed unit. The paper feed system that supplies recording sheets has five stages. That is, the first
The paper feed system and the second paper feed system are provided in the main body of the copying machine.
A second paper feeding unit, which is a third paper feeding system, and a third paper feeding unit, which includes a fourth paper feeding system and a fifth paper feeding system, are connected to the main body of the copying apparatus.

21, 22, 23 and 24 are the first paper feeding systems, respectively.

These are cassettes provided in the second paper feeding system, the third paper feeding system, and the fourth paper feeding system, and 25 is a tray of the fifth paper feeding system.

A contact glass 1 on which a document is placed is provided at the top of the main body of the copying apparatus.

An optical scanning system (scanner) is located below the contact glass 1.
It is equipped with 30. The optical scanning system 3o includes an exposure lamp 31. First mirror 32. Second mirror 33. 3rd mirror 3
4. Lens 35. Fourth mirror 36. It is provided with slits 37, etc. When performing document reading scanning, a first carriage carrying an exposure lamp 31 and a first mirror 32, a second mirror 33, and a third mirror 3 are used so that the optical path length does not change.
4 is mechanically scan-driven at a relative speed of 2:1.

This scanning direction, that is, the sub-scanning direction is the left-right direction in FIG. 1, and the sub-scanning start position of the scanning system is at the left end. At the sub-scanning start position, a home position sensor (not shown) detects the second carriage and is turned on. A reference density pattern (hereinafter referred to as P sensor pattern) 13 is arranged at the image reading position of the sub-scanning start position of the scanning system. The image reading position at the sub-scanning start position is a little to the left of the tip of the original DOC on the contact glass 1, and at this time, an image is placed on a surface continuous to the bottom surface of the contact glass 1 so as to read the P sensor pattern 13.
A sheet formed with a black pattern having a predetermined light reflectance, that is, a P sensor pattern 13 is arranged.

The lens 35 is a zoom lens, and its magnification can be changed by driving a motor.

The light emitted from the exposure lamp 31 is reflected by the image reading surface (P sensor pattern 13 or original DOC), and is reflected by the first mirror 32.
．． Second mirror 33. Third mirror 34, lens 35. Fourth
Through the mirror 36 and the slit 37, the photosensitive drum 2
imaged on top.

Around the photosensitive drum 2, there are a main charger 3, an eraser 4. Developing cartridge 5. Toner image sensor (hereinafter referred to as P
(referred to as a sensor) 6. Transfer charger 7, separation charger 8. A cleaning unit 9 and the like are arranged.

Briefly explain the copy process.

The surface of the photosensitive drum 2 is uniformly charged to a predetermined high potential by the discharge of the main charger 3, but the charge on the portion not used for copying is erased by the eraser 4 (described later). When the charged surface of the photosensitive drum 2 is irradiated with reflected light from the original, the potential of that portion changes (exposure neutralization) depending on the intensity of the irradiated light. The photosensitive drum 2 rotates in the direction shown by the arrow in the figure, and in synchronization with this, the optical scanning system 30 sequentially scans the document surface, so that the density (light reflectance) of the document image is reflected on the surface of the photosensitive drum 2 A potential distribution corresponding to the distribution, that is, an electrostatic latent image is formed.

When the portion on which the electrostatic latent image is formed passes near the developer cartridge 5, the toner in the developer cartridge 5 is electrostatically attracted to the surface of the photoconductor 2 according to the potential distribution, and the toner is attracted to the surface of the photoreceptor 2 according to the electrostatic latent image. A visible image is formed on the photoreceptor drum 2 (development).

On the other hand, in synchronization with the progress of the copying process, recording sheets are fed from one of the five paper feeding systems selected.

This recording sheet is fed through the registration roller 27 at a predetermined timing so as to overlap the surface of the photoreceptor drum 2, and the visible image (toner image) on the photoreceptor drum 2 is transferred by the transfer charger 7. Furthermore, the recording sheet onto which the visible image has been transferred is separated from the photosensitive drum 2 by the separation charger 8 . The separated recording sheets are transported to a fixing device 12 by a transport belt 11. After passing through the fixing device 12, the toner image on the recording sheet passes through the fixing device 12.
It is fixed onto the recording sheet by the internal heat. After fixing, the recording sheet i passes through a predetermined paper ejection path and is delivered to the sorter 7.
0 or discharged to the automatic double-sided processing unit 80.

FIG. 2 is a block diagram that does not show the control system of this embodiment, and includes a central processing unit (CPU) 100. Memory element ROM10I, RAM102.110 port 10
A main printer 17-ra 104 consisting of three components is operated by various operation keys 105 of an operation unit (not shown) and connected via an AC controller 107, and is connected to a document feed mechanism (DF) 108, The sorter 1091 is connected to the double-sided copy mechanism 110 via the optional controller 111.

Further, the main controller I/roller 104 receives data from a document width sensor 113 and a document length sensor 114 via a scanner controller 112, and sends data to the scanner motor 115. Outputs on/off data of the lens motor 116, and also outputs sensors such as paper end sensor, cassette size sensor, etc.
It exchanges data with clutches, solenoids, relays, etc. of various drive parts.

Next, the centering mode will be explained.

When document G is set in the correct position on contact glass 1, the document size (for example, A4 portrait).

Depending on the combination of the magnification (for example, 100%) and the transfer size (for example, A3), a normal copy as shown in FIG. 3 fa) is made on the transfer paper P. Centering copying is copying this original G at the center of the transfer paper P as shown in FIG. 3 fbl.

To achieve this, if we consider image exposure as a standard,
The start of paper feeding and the start of the registration 27 may be shifted from the normal timing by the amount of image movement.

However, the registration start timing is such that the scanner controller 12 calculates the position of the scanner 30 before scanning and instructs the main controller 104, so even if the scan start is at a fixed timing, the run-up/acceleration period is Therefore, the timing between scan start and registration start may vary to some extent due to machine differences.

In normal copying, the transfer paper is fed to the registration rollers 27, stopped once, and then conveyed to the transfer position in response to a registration start command, so that variations are absorbed by the stop time and do not have any effect.

However, when moving the image, the registration start timing for pass 1;t; is predicted and the registration is started at a timing earlier by the amount of movement from there, so the variation between the scan start and normal registration start timing is directly related to the image transfer position. It becomes an error.

In an actual machine, the scan start timing is corrected by the magnification so that the timing from the start of paper feeding to the start of registration is constant, so the timing of registration star 1- should always be constant.
It is inevitable that there will be some degree of error. As mentioned above, in normal copying, this error is absorbed and has no effect at all, but it is an error that we would like to prevent at the time of centering.

This timing chart is shown in FIG. 4 (al, (bl).

As shown in Figure 4 (al), if the paper feed timing is 1823 pulses and the scan start at the same magnification is 1937 pulses, the registration start is designed to be about 2000 pulses. Image movement amount 00 pulses per month Then, the timing for this centering copy is the fourth one.
As shown in the figure (bl), the paper feeding timing may be performed at 1723 pulses, the scan start at the same magnification at 1937 pulses, and the registration start at 1900 pulses.

However, the value of 1900 pulses for the registration start includes an error. Because the standard is 200
This is because the value of 0 pulse is not absolute. In order to reduce this error, when a registration start command is received from the scanner controller 112 during normal copying, the main controller 104 adjusts the timing to the RA.
Store it in MIO2. During centering copy,
The average value is calculated from the data stored in the RAM 102, and 2
Instead of 000 pulses, this average value is used as a reference value, and the resist scoot timing is set to the reference value - 100 pulses.

By doing this, the machine is controlled at the appropriate timing and errors are reduced.

The amount of centering movement is determined from the document size, magnification, and transfer paper size.

Figure 3 (As shown in C1, the original length is ffd, and the transfer paper length is A.
p (both lengths in the scanning direction) 1 If M is the magnification, then
The amount of movement l is 7! When p-Mpd<0, the movement is in the direction of delaying the resist, but this will not be discussed here.

The transfer paper size is checked by a cassette size sensor, and the document size is checked by DF or prescan.

The operation will be explained using flowcharts shown in FIGS. 5 to 7.

FIG. 5 is a general flow of copy control.

After turning on the power, first in flow (5-1), CPU1
00, operation mode settings for peripherals, etc., RAM102
Perform initialization, etc.

In the next flow (5-2), the copy OK conditions are checked, the operation keys are accepted, the operation mode is checked, and the process waits for the print SW to be pressed and copy to start.

Next, in flow (5-3), the drum rotates from when the print switch is pressed until paper is fed.

This includes processing such as document feeding from the DF, prescanning, and checking the document size by the DF.

When these processes are completed, a flow (5-4) is executed in which paper feeding is started and image formation is performed. Here, sequence control is mainly used to count the drum clock generated by the rotation of the photosensitive drum and control the load according to the counted value.

When copying for the set number of sheets is completed or when copying is interrupted, the process advances to flow (5-5). Here, processing is performed until all transfer paper in the machine is ejected and the main motor is stopped. After the main motor stops, the flow (5-2
) returns to the waiting process.

FIG. 6 shows a timing calculation flow during centering.

This flow is executed as part of flow (5-3) copy preprocessing in FIG. Since the original size is required during centering copying, the original size is detected by prescanning the original during pressure plate copying (6'-2>), and during DF copying (6-1), the original size is detected at the time of original feed-in. (6-3).

Next, the centering amount is calculated (6-4).

As mentioned above, the centering amount 1=1/2(lp-MX
j! d) and convert it into the number N of drum clocks.

Next, the paper feeding timing is calculated (6-5).

In order to start the registration N pulses earlier than in normal copying, the paper feeding timing also needs to be N pulses earlier than in normal copying.

Paper feed timing TFC - Normal feed timing TF
N N . Here, the normal feed timing TFN is a constant determined depending on the paper feed stage. In this embodiment, the reference for the sequence of copy processing is paper feeding, so the TFC determined here is set in the drum clock counter at the time of paper feeding.

Next, a registration timing calculation is performed (6-6).

In normal copying, a registration start is commanded by the scanner controller 112, but at the time of centering, it must be started before this command. For this reason, it is necessary to find the normal registration start timing, but this includes parts that are not synchronized with the rotation of the drum, such as the scanner run-up/acceleration period and the stop position, so although it can be said that the timing is approximately constant, Differences in the load of the scanner 30, etc. have an influence, resulting in errors.

During normal copying, even if the registration start timing changes slightly, the transfer paper and image are synchronized at this point, so the time the transfer paper stops in front of the registration simply changes, but the difference is absorbed and the copy There is no effect on the top.

However, during centering copying, the scanner is often scanned after the registration has started and transfer has started, and in this case, even if the timing difference is small, the image position on the transfer paper is directly This will result in an error.

Therefore, by a method to be described later, the average value of the registration timing during normal copying is determined, the dirt is used as reference data for the centering operation, and the registration timing T+tc during centering is determined.

Registration timing TRc-average value TRAv-N As a result, the optimum registration timing for centering can be obtained.

FIG. 7 shows a flow of creating reference data for registration timing.

This flow is executed when the scanner controller 112 receives a registration start command during the data reception interrupt routine. During a copy operation that is not in centering mode (7-1), when a registration start command is received from the scanner controller, the drum clock counter value at that time is sampled (7-2), and after sampling a predetermined number of times (7-3), the average value is calculated. (7-4) and use this as reference data for the centering operation.

This data is stored in non-volatile RAM. This sampling may be performed by providing a mode such as a sampling mode as a check mode, instead of always sampling during normal copying as in this embodiment. In this way, since the registration timing during centering is determined based on the 5f4% data as the average value in the sampling mode, accurate registration timing can be obtained.

〔effect〕

As described above, the present invention can provide an image forming apparatus that can create an image in the centering mode without being affected by machine-to-machine differences due to machine accuracy, and can improve image position accuracy.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic front view of a copying machine, FIG. 2 is a block diagram of the control system of the entire copying machine, and FIG. 3 (al, [bl, (C1 is the manuscript and □
Diagrams for explaining the relationship between transfer paper; Figure 4 (l) is a timing chart during normal copying; Figure 4 [bl is a timing chart during centering copying]; Figures 5 and 6;
7 are flowcharts relating to the operation of each part of this embodiment. 27... Registration roller, 104.112... Sampling means, calculation means, G... Original, P... Transfer paper. Figure 2 Figure 3 (a) Figure 3 (b) Figure 3 (c) Figure 4 (a) ↑ Leopard λχυ Nofrus Figure 4 (b) Figure 6 Figure 5 Figure 7

Claims (1)

[Claims] In an image forming apparatus having a centering mode in which an image forming position on a transfer paper is varied and an image of an original is transferred to the center of the transfer paper, a sampling means for sampling a registration start timing in a transfer mode in which no centering operation is performed; An image forming apparatus comprising: a calculation means for calculating reference data for a centering operation from the timing data obtained by the image forming process, and a calculation means for calculating a registration start timing during centering according to the reference data and the amount of image movement. Device.