JPH0656302A - Paper feed control method - Google Patents

Abstract

PURPOSE:To provide a paper feed control method capable of preventing skew of a paper sheet during feeding for correctly determining an image forming position by surely making the head of a paper sheet abut on a register roller with the paper sheet deflected even if there is any cause of fluctuation. CONSTITUTION:The deflection quantity of a paper sheet is corrected based on various factors, which sometimes vary, by carrying a paper sheet by means of a paper sheet carrying section 19, continuing paper sheet sending by the length corresponding to the number of reference pulses based on the time when the head of the paper sheet is detected by a first sensor 18 to deflect the paper sheet, making the head edge of the paper sheet abut on a register roller 17 to synchronize it with image forming operation to a photosensitive body 4 and drive the register roller 17, and correcting the reference number of pulsed based on the number of the pulses output from a pulse generating means corresponding to the period from the time point when the resist roller 17 starts to the time when a second sensor 20 detects the rear end of the paper sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feed control method used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, in the process of rotating a photoconductor, an electrostatic latent image is formed on the outer periphery of the photoconductor,
Since the electrostatic latent image is developed by the developing device and the developed image is transferred to the paper by the transfer device, it is necessary to supply the paper in accordance with the image forming operation on the photoconductor. For this purpose, a registration roller is provided in front of the photoconductor, and the leading edge of the paper supplied by the transport roller is brought into contact with the registration roller to make it stand by, and the registration roller is driven in synchronization with the image forming operation on the photoconductor. Is supplied to the outer periphery of the photoconductor, the image forming position on the photoconductor and the printing position on the paper must be matched.

On the other hand, the sheet is skewed in the process of being conveyed to the registration rollers, and the above-described object cannot be achieved unless the leading edge of the sheet reaches the nip portion of the paired registration rollers without fail. The sheet is fed by the conveying roller for a certain period of time after the leading edge of the sheet comes into contact with the registration roller to bend the sheet, and the sheet is kept waiting for the next operation of the registration roller with the conveying roller stopped. As described above, there are the following conventional examples for bending the paper.

First, in the invention filed under the name of a method for controlling the sheet conveyance of a copying machine (Japanese Patent Laid-Open No. 62-211233), the time when the sheet is in contact with the registration roller exceeds a certain value. The contents of bending the paper by stopping the feeding operation of the paper on the upstream side are described.

Secondly, the invention filed under the name of paper edge resist control system in electrophotographic apparatus (Japanese Patent Laid-Open No. 63-
No. 106249) describes that the transfer position is made uniform by changing the time for temporarily stopping the fed paper by the registration rollers depending on the paper feed path.

Thirdly, in the invention filed under the name of image forming apparatus (Japanese Patent Laid-Open No. 1-176746), the amount of loop generated between the pair of registration rollers and the image forming section of the conveyed sheet is detected. However, the contents for controlling the drive of the sheet conveying means are described. Fourthly, in the invention filed under the name of a sheet feeding device (Japanese Patent Laid-Open No. 4-90565), a loop is formed on a sheet between a registration roller and an intermediate roller located in front of the registration roller, and the amount of the loop is formed. Is detected to correct the driving time of the intermediate roller.

Fifth, the invention filed under the name of deflection amount adjusting method in image forming apparatus (Japanese Patent Laid-Open No. 4-5397).
No. 3) is a device that stops the paper feeding operation so as to cause a predetermined amount of bending of the recording paper from the time when the leading edge of the recording paper is detected by the registration sensor, and when the recording paper is an envelope, The contents to reduce the amount are described.

[0008]

The timing at which the sheets come into contact with the registration rollers can be detected by a sensor provided in the sheet conveying path. Further, the sheet is conveyed by driving a motor or setting a clutch between the motor and the conveying roller in a power transmission state. However, the sensitivity of the sensor, the response speed of the operation of the motor and the clutch, the rotation driving system, and the like. Factors such as the inertial force of the
Since the temperature and humidity of the environment of use also change, it is difficult to keep the amount of paper feed, that is, the amount of paper flexure constant. In the above, the condition for setting the bending amount of the papers is a fixed value, so it is difficult to always set the bending amount of the papers to an optimum value. Even in the case of envelopes, it is difficult to set the amount of deflection to an optimum value because there is a variation factor as described above even for those that reduce the amount of deflection. Therefore, when the amount of flexure is small, it is not possible to correct skewing of the sheets. In addition, it is not possible to make the leading ends of the sheets of paper bite into the nip portion of the pair of registration rollers, which deteriorates the followability of the sheets of paper when the registration rollers are driven, which causes a problem in that the printing position is disturbed. Further, when the amount of bending of the paper is large, there is a problem that the paper is broken.

[0009]

According to another aspect of the present invention, there is provided a paper feed path between an image forming section having a photoconductor and a paper feed section,
A pair of registration rollers driven by the sheet re-feed driving means, a first sensor located upstream of these registration rollers to detect a sheet, and a sheet feeding drive means located upstream of the first sensor. And a second sensor for detecting the sheet, and the sheet feeding drive unit drives the sheet conveying section to convey the sheet to the registration roller side. When the first sensor detects that the first pulse counter is started, the number of pulses output from the pulse generating means is made to correspond to the operation of the paper feeding drive means, and the value of the first pulse counter is set as a reference. When the pulse value is reached, the paper feed drive means is stopped, the paper is flexed and the leading edge of the paper is brought into contact with the registration rollers, and the paper is waited for. In the paper feed control method which is adapted to drive the registration rollers by the sheet re-feed driving means,
The number of pulses output from the pulse generating means corresponding to the operation of the refeed driving means during the period from the time when the refeed driving means is started until the second sensor detects the trailing edge of the paper. The second pulse counter is used to make a coefficient, and the reference pulse number is corrected based on the coefficient value of the second pulse counter.

According to a second aspect of the present invention, in the first aspect, the reference pulse number is set as an initial value, and the reference pulse number is updated based on the coefficient value of the second pulse counter according to the progress of the image forming operation. It was done like this.

According to a third aspect of the present invention, in the first aspect, the reference pulse number is set as an initial value, the average value of the coefficient values of the second pulse counter is calculated according to the progress of the image forming operation, and the average value is calculated. The reference pulse number is updated based on the above.

[0012]

According to the first aspect of the present invention, the sheet feeding drive unit drives the sheet conveying unit to feed the sheet to the registration rollers from the time when the leading edge of the sheet is detected by the first sensor until the reference pulse number is reached. Causes the sheet to bend and bring its leading end into contact with the registration roller, and the re-feed drive unit drives the registration roller to convey the sheet to the image forming unit. The reference pulse number can be corrected based on the number of pulses counted until the trailing edge of the sheet is detected by the second sensor, which allows the sheet to be corrected based on various factors that change from time to time. The amount of deflection can be set, and therefore, even if there are fluctuation factors, skewing and bending of the paper can be always prevented, and the printing position can be accurately determined.

According to the second aspect of the present invention, it is possible to set the amount of deflection of the sheet to an appropriate value, including factors that fluctuate in a short period of time.

According to the third aspect of the present invention, even if the reference pulse number rarely shows an abnormal value, it is possible to set the optimum reference pulse number based on the average value including the data before and after the reference pulse number.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a vertical sectional front view showing the internal structure of a copying machine. In the figure, reference numeral 1 is a main body, and an image forming section 2 is provided in the main body 1, and a scanner for reading a document image is provided on the image forming section 2. 3 is provided. In the process of rotating the photoconductor 4, the image forming unit 2 applies a charge from the charger 5 to the outer periphery of the photoconductor 4 to charge the photoconductor 4, and the charged portion receives a corresponding optical signal read by the scanner 3. Irradiation forms an electrostatic latent image, and the electrostatic latent image is developed by the developing device 6. The developed image is transferred onto a sheet by the transfer device 7. The sheet on which the image is transferred is separated from the photoconductor 4 by the separation roller 8, and the fixing roller 9
Thus, the transferred image is fixed. After the image transfer, the cleaning roller 10 wipes off the residual toner on the photoconductor 4, and then the charge eliminator 11 uniformly removes the charge.

Next, paper feed cassettes 12 and 13 as paper feed units are detachably attached to one side of the main body 1, and a paper feed passage 14 from these paper feed cassettes 12 and 13 toward the photoconductor 4 is provided. And a paper discharge path 16 extending from the photoconductor 4 to the paper discharge tray 15. In the paper feed path 14, a pair of registration rollers 17 and a first sensor 18 for detecting a sheet located upstream of the registration rollers 17 are provided.
And a pair of conveying rollers 19 as a sheet conveying section located upstream of the first sensor 18, a second sensor 20 for detecting the sheet, and a separation roller 21 located at the leading ends of the sheet cassettes 12 and 13. And the paper feed roller 22 are arranged. The registration roller 17 is connected to a motor by a registration clutch (not shown) as a sheet re-feed driving means, and the conveying roller 19 is connected to a motor by a conveyance clutch (not shown) as a sheet feeding driving means. . Further, in the paper discharge path 16, a third sensor 23 located near the downstream side of the separation roller 8 and the fixing roller 9 are provided.
And a fourth sensor 24 located near the downstream side of the.

Next, FIG. 2 shows an electronic circuit. CPU2
5, a RAM 26 in which variable data is written, a ROM 27 in which program data is written, and I / O & buffers 28 and 29 are connected on a bus line. The RAM 26 holds data by a backup power supply. Of course, a non-volatile memory may be used. The C
Various key switches of the operation board 30 are connected to the PU 25 via buffers 31 and 32, and
Various sensors including the first to fourth sensors 18, 20, 23 and 24 are connected to a pulse oscillator 33 which is a pulse generating means. This pulse oscillator 33 is
A pulse is output corresponding to the rotational movement of the drive system of the transport roller 19 and the registration roller 17.

A plurality of drivers 34, 35, 36 and 37 are connected to the I / O & buffer 28, and the I / O & buffer 28 is connected to the I / O & buffer 28.
/ O & buffer 29 has a plurality of drivers 38, 39, 4
0 and 41 are connected. The drivers 35, 36,
37 drives each of various display elements of the operation board 30, the driver 37 drives various mechanical drive systems, and the driver 38 exposes the scanner 3 to the photoconductor 4 and the charger. 5, the driver 39 drives the registration roller 17, the transport roller 19,
A sheet feeding / discharging system motor connected to the separating roller 21, the sheet feeding roller 22 and the like is driven, the driver 40 drives a motor and the like connected to the fixing roller 9, and the driver 41 is a peripheral machine and the like. Is to drive.

Next, an actual paper feed control method will be described. First, FIG. 3 shows a model for setting the deflection amount of the paper. In the figure, 42 is a sheet, 43 is a sheet guide, FIG. 3A shows the state in which the sheet 42 reaches the registration roller 17, and FIG. 3B shows the sheet 42 abutted against the registration roller 17. It is in a state of being. Here, when the length of the paper 42 is Lsize, the center distance between the registration roller 17 and the second sensor 20 is L1, and the distance between the second sensor 20 and the rear end of the paper 42 is L2, the deflection of the paper 42 is assumed. The quantity Lt is defined by: Lt = Lsize- (L1 + L2) ...

Here, from when the registration roller 17 is rotated and the sheet 42 is started to be fed in the direction of the image forming unit 2 (leftward) until the trailing edge (right edge) of the sheet 42 passes the second sensor 20. , L2 = P2-Lp, where P2 is the number of pulses output from the pulse generator 33 and Lp is the transport distance of the paper 42 per pulse.

Therefore, the deflection amount Lt of the paper 42 is given by Lt = Lsize- (L1 + P2 * Lp).

Further, the calculated deflection amount L1 of the sheet 42
The difference between the reference deflection amount Lts and the reference deflection amount Lts changes in accordance with the inertial force of the transport drive system, the sensitivities of the first and second sensors 18 and 20, the rise time of the plats in the transport drive system, and changes in ambient temperature and humidity. The variation Ltx of the frictional force etc.
Is represented by Ltx = Lts-Lt ... However, it differs depending on each copying machine.

On the other hand, the registration roller 17 and the first sensor 1
Assuming that the center distance from the sheet 8 is Ls, the number of pulses P1 output from the pulse generator 33 from the time when the leading edge of the sheet 42 reaches the first sensor 18 to the time when the conveying clutch is disengaged and the conveying roller 19 is stopped, P1 = (Ls + Lts + Ltx) / Lp = (Ls + 2Lts-Lt) / Lp ... Is given as an appropriate reference pulse number.

The actual operation will be described below. First, FIG. 4 is a flowchart showing the basic operation of the copying machine. That is, the power is turned on and initialization is performed. Following this, a print preparation process, a pre-copy process, a copy process, and a copy end process are executed.

The initial setting is performed based on the flowchart shown in FIG. That is, the first sensor 18 is
In order to stop the transport roller 19 after detecting the leading edge of 2, the transport roller stop reference pulse number (P1M) is set to an initial value. Next, when the number of pulses from when the transport roller 19 is driven to when the leading edge of the sheet 42 is detected by the second sensor 20 exceeds a certain value, it means that the sheet feeding is defective.
In order to detect the paper feed failure, an initial value is set to the reference pulse number for paper feed failure detection (Pj1M). Further, when the number of pulses from the driving of the registration roller 17 to the detection of the leading edge of the paper 42 by the third sensor 23 exceeds a certain value, the separation of the paper 42 from the photoconductor 4 is defective. To detect a defect, an initial value is set to the reference pulse number for separation defect detection (Pj2M). Further, if the number of pulses from when the third sensor 23 detects the leading edge of the sheet 42 until when the leading edge of the sheet 42 is detected by the fourth sensor 24 exceeds a certain value, a jam occurs near the fixing roller 9. However, in order to detect the jam, an initial value is set to the fixing failure detection reference pulse number (Pj3M). The initial values are set in the RAM 26.

Next, the driving operation of the conveying roller 19 will be described with reference to the flowchart shown in FIG. When the paper feed signal is turned on, it is determined that the repaper feed signal is not output, and then the transport clutch is turned on.
At this time, the paper feed roller 22 and the separation roller 2
No. 1 is also driven by a predetermined rotation angle, but the description thereof is omitted because it is not directly related to the control of the present invention. By the ON operation of the transport clutch at this time, the transport roller 19 is rotated by the driving force of the motor being transmitted, and the sheet 42 is sent to the registration roller 17 side. First sensor 18 for detecting the leading edge of the paper 42
When the ON signal is output, the operation of the first pulse counter (not shown) starts and the pulse output from the pulse generator 33 begins to be coefficientd, and when the coefficient value reaches the number of pulses stored in the memory P1M, the conveyance is performed. The clutch is switched to the OFF state, and the transport roller 19 is stopped. In this state, the leading edge of the sheet 42 is brought into contact with the nip portion of the pair of registration rollers 17 and is still in a state of being appropriately bent. This state is a standby state for re-feeding the paper 42 that starts the registration rollers 17 in synchronization with the image forming operation on the photoconductor 4.

Next, the re-feeding operation will be described with reference to FIG. When the refeed signal is turned on, the registration clutch is turned on.
When N, the registration roller 17 rotates by receiving the rotational force of the motor, and the sheet 42 is conveyed to the image forming unit 2. At the same time as this operation, the operation of the second pulse counter (not shown) starts and the pulse output from the pulse generator 33 begins to be counted. Then, when the second sensor 20 detects the passage of the trailing edge of the sheet 42 and is turned off, the coefficient value of the second pulse counter is stored in the memory P2M and the second pulse counter is reset. . When the trailing edge of the paper 42 passes the first sensor 18, the registration clutch is switched off, the registration roller 17 is stopped, and the next re-feed signal is waited for.

As described above, the reference pulse number P1 from when the leading edge of the paper 42 is detected by the first sensor 18 to when the conveying roller 19 is stopped is corrected by the above-mentioned formula, and therefore changes from time to time. The deflection amount of the sheet 42 can be set based on various factors. Figure 9
The state shown in (a) shows a state in which the sheet 42 is bent with an appropriate amount of deflection and held by the transport roller 19, and in this state, the sheet 42 returns to its original shape due to the strength of its own waist. The leading edge is brought into contact with the nip portion of the pair of registration rollers 17 by the action of returning. Therefore, skewing is always prevented, and the relative position with respect to the image forming position on the photoconductor 4 is also accurately determined. Furthermore, FIG.
As shown in (b), the paper 42 is not flexed more than necessary. This prevents the paper 42 from being broken. Then, for each print, the reference pulse number P1
Is corrected, it is possible to set the deflection amount of the paper 42 to an appropriate value including a factor that changes in a short period of time.

FIG. 8 shows a flowchart for calculating the reference pulse number P1. That is, the distance L2 between the second sensor 20 and the rear end of the paper 42 is calculated by the above formula, and the deflection amount Lt of the paper 42 is calculated by the above formula,
The reference pulse number P1 from the time when the leading edge of the paper 42 reaches the first sensor 18 to the time when the conveying roller 19 is stopped is calculated by the above formula, and the reference pulse number P1 is stored in the memory of P1M.

Next, a second embodiment of the present invention will be described based on the flowchart shown in FIG. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof will be omitted. The operation of the first, second and third steps of this flowchart is the same as the operation of the first, second and third steps in FIG. For each printing of one sheet, the plurality of reference pulse numbers P1 calculated in the third step is the average value P11 in the fourth step.
Is calculated, and the average value P11 of the reference pulse number P1 is P
Stored in 1M memory. Therefore, even if the reference pulse number P1 rarely shows an abnormal value, it is possible to properly set the reference pulse number P1 with the average value P11 including the data before and after the reference pulse number P1.

[0031]

As described above, according to the first aspect of the invention, as described above, the sheet feeding section is driven by the sheet feeding driving means to feed the sheet to the registration roller side, and the first sensor detects the leading edge of the sheet. The first pulse counter is started with to make the number of pulses output from the pulse generating means correspond to the operation of the paper feed driving means, and the feeding is performed when the value of the first pulse counter reaches the reference pulse value. The sheet driving means is stopped, the sheet is bent and the leading edge of the sheet is awaited in contact with the registration roller, and the sheet feeding drive means drives the registration roller in synchronization with the image forming operation on the photoconductor. Then, the number of pulses output from the pulse generating means corresponding to the operation of the re-feed driving means during the period from the time when the re-feed driving means is started to the time when the second sensor detects the trailing edge of the sheet. The second pa By adjusting the coefficient with a counter and correcting the reference pulse number based on the coefficient value of the second pulse counter, the amount of deflection of the paper can be set based on various factors that change from time to time. Even if there are fluctuation factors, it is possible to always prevent skewing and bending of the paper, and it is possible to accurately determine the printing position, and such an effect can be obtained without adding special parts or devices. Therefore, there is an effect that the cost can be reduced.

According to a second aspect of the present invention, in the first aspect, the reference pulse number is set as an initial value, and the reference pulse number is updated based on the coefficient value of the second pulse counter according to the progress of the image forming operation. Since this is done, there is an effect that the amount of deflection of the paper can be set to an appropriate value, including factors that fluctuate in a short time.

According to a third aspect of the present invention, in the first aspect, the reference pulse number is set as an initial value, the average value of the coefficient values of the second pulse counter is calculated according to the progress of the image forming operation, and the average value is calculated. Since the reference pulse number is updated based on the above, even if the reference pulse number rarely shows an abnormal value, it is possible to set the optimum reference pulse number with the average value including the data before and after the reference pulse number. Have.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a copying machine according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an electronic circuit.

FIG. 3 is an explanatory diagram for setting a deflection amount of a sheet.

FIG. 4 is a flowchart showing a basic operation of the copying machine.

FIG. 5 is a flowchart showing an initial setting operation.

FIG. 6 is a flowchart for driving a transport roller.

FIG. 7 is a flowchart showing a re-feeding operation of registration rollers. Is.

FIG. 8 is a flowchart for calculating a reference pulse number.

FIG. 9 is a front view showing how the sheet is bent.

FIG. 10 is a flowchart for calculating a reference pulse number according to the second embodiment of the present invention.

[Explanation of Codes] 2 Image Forming Section 4 Photosensitive Member 12, 13 Paper Feeding Section 14 Paper Feeding Path 17 Registration Roller 18 First Sensor 19 Paper Conveying Section 20 Second Sensor 33 Pulse Generating Means 42 Paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 15/00 110 7369-2H

Claims (3)

[Claims] 1. A pair of registration rollers driven by a sheet re-feed driving means in a sheet feeding path between an image forming section having a photoconductor and a sheet feeding section, and a position upstream of these registration rollers. A first sensor for detecting a sheet, a sheet conveying section located upstream of the first sensor and driven by a sheet feeding drive means, and a second sensor for detecting the sheet are provided. The sheet driving unit drives the sheet conveying unit to convey the sheet to the registration roller side, and when the first sensor detects the leading edge of the sheet, the first pulse counter is started to operate the sheet feeding driving unit. The number of pulses output from the pulse generating means is made to correspond to, and when the value of the first pulse counter reaches the reference pulse value, the paper feeding driving means is stopped and the paper is bent to make its leading end. The edge is the registration roller In the sheet feeding control method, the sheet re-feeding driving means starts the sheet re-feeding driving means in such a manner that the sheet re-feeding driving means drives the registration roller in synchronism with the image forming operation on the photoconductor. In the period from the time when the second sensor detects the trailing edge of the sheet, the second pulse counter causes the number of pulses output from the pulse generating means to correspond to the operation of the re-feed driving means, A paper feed control method, wherein the reference pulse number is corrected based on the coefficient value of the second pulse counter. 2. The reference pulse number is set as an initial value, and the reference pulse number is updated based on the coefficient value of the second pulse counter according to the progress of the image forming operation. 1. The paper feed control method described in 1. 3. A reference pulse number is set as an initial value, an average value of coefficient values of the second pulse counter is calculated according to the progress of the image forming operation, and the reference pulse number is updated based on the average value. The paper feed control method according to claim 1, wherein the method is as described above.