JP3858722B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly to a paper feed control technique thereof.
[0002]
[Prior art]
In the conventional image forming apparatus, the fed paper is temporarily stopped by the registration roller, and then restarted and conveyed to the transfer unit, thereby adjusting the position of the leading edge of the paper and the leading edge of the image on the photosensitive member. Like to do. At this time, the middle to rear end portions of the sheet applied to the sheet feeding roller of the sheet feeding unit are fed by the rotation of the sheet feeding roller, and the sheet feeding unit is not driven.
[0003]
In this case, the paper transportability is not necessarily stable, and tends to be worse particularly in a system in which the cost of parts is reduced or a system in which the size is reduced. There are also variations depending on the type of paper to be transported and the layout of the transport path. For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 09-226985, the paper transportability is stabilized by driving the paper feed roller simultaneously with the registration restart according to the paper feed unit and the paper type.
[0004]
[Problems to be solved by the invention]
Here, there is no problem if the size of the paper to be transported is correct, but there is usually a size designation means such as a size setting dial for each tray so that the size of the paper set in the paper feed unit can be determined. Therefore, the set size and the size of the actually set paper may be different.
[0005]
In such a case, there is a problem in the timing of stopping the paper feed roller that is driven simultaneously with the registration restart. If the paper that is actually set is large, the drive of the paper feed roller is cut before reaching the trailing edge of the paper, so that the transportability is deteriorated from the middle, and the image is also affected. In the case of a small sheet, the paper feed roller continues to be driven even after the trailing edge of the sheet has passed, so that the next sheet is also fed, causing a jam or the like.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to stop the paper feed roller drive at the time of re-registration and perform a follow-up operation when a size error is detected. Thus, the invalid paper due to the size error is surely discharged out of the apparatus, and jamming for feeding the next paper is prevented, thereby improving the operability.
[0007]
The object of the present invention is to replace the size information of the paper feeding unit in which a size error has occurred with the actually detected size information so as to determine the subsequent paper feed roller control timing, thereby causing the size error. It is to improve the operability as well as to obtain a stable conveying property that does not cause jamming.
[0008]
The object of the invention described in claim 3 is to replace the size information of the paper feed unit in which the size error has occurred with the actually detected size information, determine the subsequent feed roller control timing, and the size information is the paper feed It is intended to hold the unit until it is reset, to obtain a stable conveyance property that does not cause a jam due to a size error, and to improve the operability.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, the paper feeding roller is operated simultaneously when the sheet being conveyed is temporarily stopped by the registration roller and then restarted from the registration position. In an image forming apparatus having a function of stopping the paper feed roller when a predetermined time calculated based on the paper size information that has been detected has passed, the actually detected paper size is different from the pre-specified paper size The most important feature is an image forming apparatus provided with a main control means for performing control for prohibiting driving of the paper feed roller when the paper is restarted from the registration position.
[0010]
According to the second aspect of the present invention, after the paper being transported is temporarily stopped by the registration roller and then restarted from the registration position, the paper feeding roller is operated simultaneously, and calculation is performed based on the specified paper size information. In the image forming apparatus having the function of stopping the paper feed roller when the predetermined time has elapsed, the paper size is actually detected when the actually detected paper size is different from the predesignated paper size. The timing of stopping the paper feed roller that is operated in synchronization with the restart of the paper from the registration position is the most suitable for the image forming apparatus provided with the main control means that controls based on the replaced size information. Main features.
[0011]
The main feature of the image forming apparatus according to claim 2 is that the replaced size information is initialized when the paper feed unit is reset.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, an image forming unit 2 is provided at the center of a housing 1 of the image forming apparatus. The image forming unit 2 is formed by arranging a charging roller 4, a writing unit 5, a developing unit 6, a transfer roller 7, and a cleaning unit 8 around the photoreceptor 3.
[0013]
In the image forming section 2, the photosensitive member 3 is uniformly charged by the charging roller 4, and an electrostatic latent image is formed by scanning the charged portion with a laser beam modulated in accordance with image data by the writing unit 5. Then, the electrostatic latent image is developed by the developing unit 6, the developed image on the photoconductor 3 is transferred to a sheet by the transfer roller 7, and the residual toner on the photoconductor 3 is cleaned by the cleaning unit 8.
[0014]
A fixing unit 10 that applies heat and pressure to fix the toner on the sheet in the process of conveying the sheet that has passed through the transfer roller 7 is provided in the sheet conveyance path 9 that passes between the photoreceptor 3 and the transfer roller 7. Is provided. Further, the downstream side of the paper transport path 9 is branched into a paper discharge path 12 connected to a paper discharge tray 11 formed on the housing 1 and a reverse path 13. A switching claw 14 for switching between the two is rotatably provided.
[0015]
Further, a double-sided unit 15 is provided below the photosensitive member 3 to re-feed the sheet that has been reversed and returned from the reversing path 13 toward the image forming unit 2 again. Further, a manual feed tray 16 and a paper feed roller 17 that feeds the paper inserted in the manual feed tray 16 to the image forming unit 2 are provided on one side of the housing 1.
[0016]
A paper feed tray 19 serving as a paper feed unit for storing a large number of sheets in a stacked state is detachably mounted below the housing 1. A paper feed roller 21 that feeds the paper in the paper feed tray 19 to the paper transport path 9 via the paper feed path 20 is rotatably provided above the paper feed tray 19. In addition, a pair of registration rollers 22 disposed between the paper feed roller 21 and the photoreceptor 3 are provided in the paper transport path 9. A registration sensor 30a is disposed in the vicinity of the registration roller 22 on the paper feed side.
[0017]
FIG. 2 is a block diagram of the image forming apparatus according to the embodiment of the present invention. A main control unit 23 having a microcomputer configuration is provided, to which the writing unit 5, the fixing unit 10, and the duplex unit 15 are connected. Further, a high voltage driving unit 24, a driver 26 for driving a motor 25, and a paper feeding clutch 27 are provided. A driver 28 for driving, a controller 29, and various sensors 30 are connected.
[0018]
Here, the high-voltage driving unit 24 is a unit that drives a portion that requires a high-voltage power source, such as the charging roller 4, the developing unit 6, and the transfer roller 7 arranged around the photoreceptor 3. A motor (main motor) 25 is a rotational drive source such as the photosensitive member 3 and the fixing unit 10, and the rotational force is transmitted to the paper feed roller 21 through the paper feed clutch 27.
[0019]
The controller 29 has a function of an interface connected to a host computer (not shown), and further has a function of giving image data editing, image data transfer, and image formation instructions to the main control unit 23.
[0020]
Although not shown, the various sensors 30 are a temperature sensor that outputs a signal corresponding to the temperature of the fixing unit 10 and the like, a paper discharge sensor that is arranged in the paper discharge passage 12 and outputs a signal according to the paper conveyance state, and a paper feed tray 19 includes a tray sensor that outputs a signal in accordance with the insertion / removal state of 19, a paper end sensor that outputs a signal depending on the presence or absence of paper in the manual feed tray 16 or the paper feed tray 19, and the registration sensor 30 a shown in FIG. 1.
[0021]
The main control unit 23 uses mechanical load control in the image forming apparatus, image writing by the writing unit 5, monitoring of the paper conveyance state and other parts based on the outputs of the various sensors 30, and a preset program. Control the operation of each part.
[0022]
FIG. 3 is a flowchart showing a first control example. In the figure, after printing is started at STEP1, the paper feeding clutch 27 is turned on at STEP2 to start the paper feeding operation. Thereafter, in STEP3, it is checked whether the registration sensor is on. After the registration sensor is turned on, a delay for creating a deflection is provided in STEP4, and then the feed clutch 27 is turned off in STEP5.
[0023]
At this time, in STEP 6, image writing to the photosensitive member 3 is prepared under the control of the controller 29. When the preparation is completed, the writing unit 5 writes the electrostatic latent image on the photosensitive member 3, and the developing unit 6 performs the writing. Start development. This state is recognized as the start of image formation by monitoring the CPU of the main control unit 23. In synchronization with this, the registration clutch is turned on in STEP 7, and a flag indicating whether a size error has occurred is checked in STEP 8. The setting condition of this flag will be described later.
[0024]
If no size error has occurred, the paper feeding roller 21 is driven by turning on the paper feeding clutch 27 in STEP 9 to stabilize the paper feeding operation. Thereafter, although not shown, the sheet is conveyed to the fixing unit 10 and discharged outside the apparatus after the image is fixed. When the registration is restarted, the length measurement of the paper size being conveyed is started in STEP 10.
[0025]
In STEP 11, the OFF time of the paper feed clutch 27 is checked. Here, the off timing is determined by the length of the sheet being fed and conveyed, the conveyance layout, and the conveyance speed. Since the paper size is determined in advance, it can be calculated by (paper length-conveying layout) / conveying speed. After waiting for the time, the paper feeding clutch 27 is turned off in STEP 12 and the operation of the paper feeding roller 21 is stopped.
[0026]
In STEP 13, the next paper feed is checked, and in STEP 14, the next paper feed timing is measured. The next paper feed timing is calculated based on the paper size and the paper feed interval, and is generally set to be shorter than the print interval by registration start. When the predetermined timing is reached, the paper feed clutch 27 is turned on for the next paper feed in STEP15. Thereafter, it waits for the trailing edge of the preceding paper to turn off the registration sensor in STEP16. If OFF is detected, the paper size is determined in STEP17.
[0027]
In STEP 18, the preset paper size is compared with the actually measured size information. If they are different, a size error occurs, and a flag indicating that a size error has occurred in STEP 19 is set. Thereafter, if there is a next paper feed in STEP 20, STEP3 and subsequent steps are repeated. In other words, if a size error occurs, the result of STEP 8 is YES, so the process of STEP 9 is not executed.
[0028]
FIG. 4 is a flowchart showing a second control example. In the figure, after printing is started at STEP1, the paper feeding clutch 27 is turned on at STEP2 to start the paper feeding operation. Thereafter, in STEP3, it is checked whether the registration sensor is on. After the registration sensor is turned on, a delay for creating a deflection is provided in STEP4, and then the feed clutch 27 is turned off in STEP5.
[0029]
At this time, in STEP 6, image writing to the photosensitive member 3 is prepared under the control of the controller 29. When the preparation is completed, the writing unit 5 writes the electrostatic latent image on the photosensitive member 3, and the developing unit 6 performs the writing. Start development. This state is recognized as the start of image formation by monitoring the CPU of the main control unit 23.
[0030]
In synchronization with this, the registration clutch is turned on in STEP 7 and the paper feeding clutch 27 is turned on in STEP 8, thereby driving the paper feeding roller 21 and stabilizing the paper feeding operation. Thereafter, although not shown, the sheet is conveyed to the fixing unit 10 and discharged outside the apparatus after the image is fixed. Next, when the registration is restarted, the length measurement of the paper size being conveyed is started in STEP9.
[0031]
In STEP 10, the off time of the paper feed clutch 27 is checked. Here, the off timing is determined by the length of the sheet being fed and conveyed, the conveyance layout, and the conveyance speed. Since the paper size is determined in advance, it can be calculated by (paper length-conveying layout) / conveying speed. After waiting for the time, the paper feeding clutch 27 is turned off in STEP 11 and the operation of the paper feeding roller 21 is stopped.
[0032]
In step 12, the next sheet feeding is checked, and in step 13, the next sheet feeding timing is measured. The next paper feed timing is calculated based on the paper size and the paper feed interval, and is generally set to be shorter than the print interval by registration start. When the predetermined timing comes, STEP 14 turns on the paper feed clutch 27 for the next paper feed. Thereafter, the process waits for the trailing edge of the preceding paper in STEP 15 to turn off the registration sensor. If OFF is detected, the paper size is determined in STEP16.
[0033]
In STEP 17, the paper size set in advance is compared with the actually measured size information. If they are different, a size error occurs, and the size detected earlier in STEP 18 is updated as paper size information. That is, the updated size information becomes size information used for timing calculation next in STEP 10 and STEP 13. Thereafter, if there is a next paper feed in STEP 19, STEP3 and subsequent steps are repeated.
[0034]
FIG. 5 is a flowchart showing a third control example. In the figure, the print start is waited at STEP1. During standby, the state of the paper feed unit is monitored in STEP 20, and when it is reset, the size information of the paper feed unit is initialized in STEP 21. The paper feed unit is provided with a size setting dial (not shown), and the size according to the dial is held on the RAM as paper size information.
[0035]
Now, after printing is started, the paper feeding clutch 27 is turned on in STEP 2 to start the paper feeding operation. Thereafter, in STEP3, it is checked whether the registration sensor is on. After the registration sensor is turned on, a delay for creating a deflection is provided in STEP4, and then the feed clutch 27 is turned off in STEP5.
[0036]
At this time, in STEP 6, image writing to the photosensitive member 3 is prepared under the control of the controller 29. When the preparation is completed, the writing unit 5 writes the electrostatic latent image on the photosensitive member 3, and the developing unit 6 performs the writing. Start development. This state is recognized as the start of image formation by monitoring the CPU of the main control unit 23.
[0037]
In synchronization with this, the registration clutch is turned on in STEP 7 and the paper feeding clutch 27 is turned on in STEP 8, thereby driving the paper feeding roller 21 and stabilizing the paper feeding operation. Thereafter, although not shown, the sheet is conveyed to the fixing unit 10 and discharged outside the apparatus after the image is fixed. Next, when the registration is restarted, the length measurement of the paper size being conveyed is started in STEP9.
[0038]
In STEP 10, the off time of the paper feed clutch 27 is checked. Here, the off timing is determined by the length of the sheet being fed and conveyed, the conveyance layout, and the conveyance speed. Since the paper size is determined in advance, it can be calculated by (paper length-conveying layout) / conveying speed. After waiting for the time, the paper feeding clutch 27 is turned off in STEP 11 and the operation of the paper feeding roller 21 is stopped.
[0039]
In step 12, the next sheet feeding is checked, and in step 13, the next sheet feeding timing is measured. The next paper feed timing is calculated based on the paper size and the paper feed interval, and is generally set to be shorter than the print interval by registration start. When the predetermined timing comes, STEP 14 turns on the paper feed clutch 27 for the next paper feed. Thereafter, the process waits for the trailing edge of the preceding paper in STEP 15 to turn off the registration sensor. If OFF is detected, the paper size is determined in STEP16.
[0040]
In STEP 17, the paper size set in advance is compared with the actually measured size information. If they are different, a size error occurs, and the size detected earlier in STEP 18 is updated as paper size information. That is, the updated size information becomes size information used for timing calculation next in STEP 10 and STEP 13. Thereafter, if there is a next paper feed in STEP 19, STEP3 and the subsequent steps are repeated. If not, the process returns and returns to standby.
[0041]
【The invention's effect】
As described above, according to the first aspect of the present invention, when the size error is detected, the paper feed roller driving at the time of re-registration is stopped and the accompanying operation is performed. Invalid paper can be reliably discharged out of the apparatus, jamming for feeding the next paper can be prevented, and operability can be improved.
[0042]
According to the second aspect of the present invention, the size information of the paper feed unit that has caused the size error is replaced with the actually detected size information, and the subsequent paper feed roller control timing is determined. Therefore, it is possible to obtain a stable transport property that does not cause a jam and to improve the operability.
[0043]
According to the third aspect of the present invention, the size information of the paper feed unit in which the size error has occurred is replaced with the actually detected size information, and the subsequent paper feed roller control timing is determined. Since the sheet is held until it is reset, it is possible to obtain a stable conveyance property that does not cause a jam due to a size error, and to improve the operability.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a first control example.
FIG. 4 is a flowchart illustrating a second control example.
FIG. 5 is a flowchart illustrating a third control example.
[Explanation of symbols]
19 Paper Tray (Paper Feeder)
21 Feed roller 22 Registration roller 23 Main control unit (main control means)

Claims (3)

When the paper being transported is temporarily stopped by the registration roller and then restarted from the registration position, the paper feeding roller is operated simultaneously, and a predetermined time calculated based on the specified paper size information has elapsed. In an image forming apparatus that sometimes has a function of stopping the paper feed roller, when the actually detected paper size is different from the pre-specified paper size, the paper feed roller is driven when the paper is restarted from the registration position. An image forming apparatus comprising main control means for performing prohibition control. When the paper being transported is temporarily stopped by the registration roller and then restarted from the registration position, the paper feeding roller is operated simultaneously, and a predetermined time calculated based on the specified paper size information has elapsed. In an image forming apparatus that sometimes has a function of stopping a paper feed roller, when the actually detected paper size is different from a pre-specified paper size, the paper size is replaced with the actually detected paper size, and the registration position An image forming apparatus comprising: main control means for controlling the timing of stopping the paper feed roller operated in synchronization with the restart of the paper from the printer based on the replaced size information. 3. The image forming apparatus according to claim 2, wherein the replaced size information is initialized when the paper feeding unit is reset.

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