JP3973363B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus such as a copying machine or a printer having a feature in sheet feeding control.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus generally stops a sheet by a registration roller and then restarts it in order to align an image with a fed sheet. In this way, adjustment is performed.
[0003]
That is, it is necessary that the registration roller stops immediately before the leading edge of the sheet reaches the registration roller, and rotates after the restart until the trailing edge of the sheet passes. Therefore, it is necessary to drive the registration roller at a predetermined timing for each size of paper to be conveyed.
[0004]
Normally, there is a case in which the size is specified by means of a size setting dial for each tray, or the paper size is input from an external host computer or the like, which may differ from the actually set paper size. In particular, in the manual feed section and the like, a user can set an arbitrary sheet, so that a sheet setting error is likely to occur.
[0005]
In this case, since the registration roller driving timing is taken based on the designated paper size, if the actually set paper is long, the driving is stopped before passing the registration roller. There is a problem that the image is blurred or jammed due to the paper being pulled.
[0006]
In order to avoid such a situation, for example, in Japanese Patent Application Laid-Open No. 10-194529 as a prior invention example 1 similar to the present invention in the technical field, the length of a sheet being conveyed is detected and a resist is detected. The roller driving timing is determined, and when a size difference is detected, the subsequent sheet feeding operation is stopped before registration. As a result, the image forming apparatus and system disclosed in Japanese Patent Laid-Open No. 10-194529 discloses an apparatus that does not jam the paper even when the user incorrectly specifies the paper size.
[0007]
[Problems to be solved by the invention]
However, in the above prior art, when the set paper is long, the paper feeding operation is performed before the trailing edge of the preceding paper exits the paper feeding unit, so that the paper is not jammed in a state where the paper is not actually fed. turn into. In addition, when the succeeding paper is stopped, the paper is stopped in the transport path, or after that, paper cannot be fed from another paper feeding unit, so control for discharging the paper is necessary. And there is a problem that jam detection of residual paper becomes complicated.
[0008]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that more efficiently prevents jamming.
[0010]
According to the first aspect of the present invention, when the first sheet is fed, the second sheet jam is not detected until the trailing edge of the sheet is detected after the first sheet is fed. If a size error is detected when the trailing edge is detected, the second sheet is not made to be a paper jam, and an object is to improve operability by eliminating an operation for releasing the jam.
[0011]
According to the second aspect of the present invention, when the first sheet is fed, the second sheet jam is not detected until the trailing edge of the first sheet is detected. If the size measured when the trailing edge is detected is longer than the specified size, the second sheet is not jammed, and the purpose is to improve operability by eliminating an operation for clearing the jam.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, the invention described in claim 1 is directed to feeding a sheet one by one from a sheet feeding unit storing sheets, means for designating the size of the stored sheet, and a sheet feeding unit. The paper feeding roller and the registration roller for aligning the image writing position temporarily stop the paper being transported and then start the operation again, and the paper has reached or passed the registration position. And a means for detecting the length of the paper simultaneously with the detection of the trailing edge of the paper being conveyed by this sensor. Until the trailing edge of the sheet is detected, the second sheet feeding jam is not detected. When the size measurement result by the trailing edge detection is different from the set size, the detection of the second sheet feeding jam is canceled. thing It is characterized.
[0014]
According to a second aspect of the invention, in the image forming apparatus according to claim 1, wherein the measured sheet size is longer than the specified size, and cancels the second sheet feed jam.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIGS. 1 to 5, an embodiment of the image forming apparatus of the present invention is shown.
[0016]
The outline of the image forming apparatus according to the present invention will be described. FIG. 1 is a longitudinal sectional view illustrating a configuration example of an embodiment of an image forming apparatus. 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. In this image forming unit 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 according to image data by the optical 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.
[0017]
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.
[0018]
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. 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.
[0019]
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.
[0020]
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.
[0021]
FIG. 2 is a block diagram illustrating a configuration example of the control system. Next, the electrical connection configuration will be described with reference to FIG. A main control unit 23 having a microcomputer configuration is provided, and the writing unit 5, the fixing unit 10, the duplex unit 15, the high-voltage driving unit 24, the driver 26 for driving the motor 25, and the driver 28 for driving the paper feeding clutch 27 are provided. The controller 29 and various sensors 30 are connected.
[0022]
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.
[0023]
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.
[0024]
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 transport path 12 and outputs a signal depending on the paper transport state, and a paper feed tray 19 includes a tray sensor that outputs a signal according to the insertion / removal state of 19, a paper end sensor that outputs a signal according to 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.
[0025]
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.
[0026]
FIG. 3 is a flowchart showing an operation example related to the present invention . In FIG. 3, after printing is started in STEP 1, the paper feeding clutch is turned on in STEP 2 to start the paper feeding operation. After that, in STEP 3, the registration sensor checks the trailing edge missing of the preceding paper. Of course, since there is no preceding paper in the first printing operation, the result is YES and the process proceeds to the next step. For the second and subsequent sheets of continuous printing, the preceding paper is present in the apparatus, so that in STEP3, the trailing edge of the preceding paper is awaited. At this time, the time-out is checked in STEP4, and when the time-out is reached, in step 5, the preceding paper is not dropped and jam processing is performed as a jam. By the way, the time-out time is set to a time corresponding to a length obtained by adding an appropriate margin to the maximum paper size that can be passed in consideration of erroneously setting the paper.
[0027]
When the registration sensor is turned on in STEP 6, it is detected that the leading edge of the fed paper has reached the registration portion. At this time, the registration sensor arrival time is checked in STEP 7, and if a time-out occurs, the jam is dealt with in STEP 8 as a non-feed jam. The timeout time is a time corresponding to a distance obtained by adding a slight margin to the transport layout from the paper feeding position to the registration position.
[0028]
After the registration sensor is turned on in STEP 6, a paper feed clutch is turned off in STEP 10 after a delay for creating a deflection is provided in STEP 9. At this time, writing of an image on the photosensitive member is prepared in STEP 11 under the control of the controller. When the preparation is completed, writing of the electrostatic latent image on the photosensitive member by the writing unit and development by the developing unit are started. . This state is recognized as the start of image formation by monitoring the CPU of the main control unit. In synchronization with this, the registration clutch is turned on in STEP 12, and the sheet is sent out toward the photosensitive member. Thereafter, although not shown, the sheet is conveyed to the fixing unit and is discharged outside the apparatus after the image is fixed.
[0029]
FIG. 4 is a flowchart showing an operation example related to claim 1 . In FIG. 4, after starting printing in STEP 1, the paper feeding clutch is turned on in STEP 2 to start the paper feeding operation. After that, in STEP 3, the registration sensor checks the trailing edge missing of the preceding paper. Of course, since there is no preceding paper in the first printing operation, the result is YES and the process proceeds to the next step. For the second and subsequent sheets of continuous printing, the preceding paper is present in the apparatus, so in STEP3, the trailing edge of the preceding paper is awaited. At this time, the time-out is checked in STEP4, and when the time-out is reached, in step 5, the preceding paper is not dropped and jam processing is performed as a jam. By the way, the time-out time is set to a time corresponding to a length obtained by adding an appropriate margin to the maximum paper size that can be passed in consideration of erroneously setting the paper.
[0030]
Next, a size error is checked in STEP6. That is, it is checked whether or not the size of the actually passed paper is different from the designated paper size, and if it is different, the paper feeding operation is interrupted. That is, jam detection is not performed after the next step.
[0031]
If it is not a size error, it is detected that the leading edge of the fed paper has reached the registration portion when the registration sensor is turned on in STEP7. At this time, the registration sensor arrival time is checked in STEP 8, and if a time-out occurs, the jam is processed in STEP 9 as a non-feed jam. The timeout time is a time corresponding to a distance obtained by adding a slight margin to the transport layout from the paper feeding position to the registration position.
[0032]
After the registration sensor is turned on in STEP 7, a paper feed clutch is turned off in STEP 11 after a delay for creating a deflection is provided in STEP 10. At this time, writing of an image on the photosensitive member is prepared under the control of the controller in STEP 12, and when the preparation is completed, writing of the electrostatic latent image on the photosensitive member by the writing unit and development by the developing unit are started. . This state is recognized as the start of image formation by monitoring the CPU of the main control unit. In synchronization with this, the registration clutch is turned on in STEP 13 to feed the sheet toward the photosensitive member. Thereafter, although not shown, the sheet is conveyed to the fixing unit and is discharged outside the apparatus after the image is fixed.
[0033]
FIG. 5 is a flowchart showing an operation example related to claim 2 . In FIG. 5, after starting printing in STEP 1, the paper feeding clutch is turned on in STEP 2 to start the paper feeding operation. After that, in STEP 3, the registration sensor checks the trailing edge missing of the preceding paper. Of course, since there is no preceding paper in the first printing operation, the result is YES and the process proceeds to the next step. In the second and subsequent sheets of continuous printing, the preceding paper is present in the apparatus, and therefore, in STEP3, the trailing edge of the preceding paper is awaited. At this time, the time-out is checked in STEP4, and when the time-out is reached, in step 5, the preceding paper is not dropped and jam processing is performed as a jam. By the way, the time-out time is set to a time corresponding to a length obtained by adding an appropriate margin to the maximum paper size that can be passed in consideration of erroneously setting the paper.
[0034]
Next, the size detected in STEP 6 is checked, and it is determined whether or not the size of the actually passed paper is longer than the specified paper size. If the result is YES, the paper feeding operation is interrupted. That is, jam detection is not performed after the next step. Here, the fact that the size detection result is longer than the designated size indicates that the second and subsequent sheet feeding operations are not actually performed. In other words, since the continuous paper feed operation is performed at the specified paper size timing, if the paper that has been actually set is long, the next paper feed operation is entered with the trailing edge of the preceding paper not exiting the paper feed unit. As a result, jam detection will occur.
[0035]
If it is not a size error, it is detected that the leading edge of the sheet fed by the registration sensor ON in STEP 7 has reached the registration portion. At this time, the registration sensor arrival time is checked in STEP 8, and if a time-out occurs, the jam is processed in STEP 9 as a non-feed jam. The timeout time is a time corresponding to a distance obtained by adding a slight margin to the transport layout from the paper feeding position to the registration position.
[0036]
After the registration sensor is turned on in STEP 7, a delay for creating a deflection is provided in STEP 10, and then the paper feeding clutch is turned off in STEP 11. At this time, writing of an image on the photosensitive member is prepared under the control of the controller in STEP 12, and when the preparation is completed, writing of the electrostatic latent image on the photosensitive member by the writing unit and development by the developing unit are started. . This state is recognized as the start of image formation by monitoring the CPU of the main control unit. In synchronization with this, the registration clutch is turned on in STEP 13 to feed the sheet toward the photosensitive member. Thereafter, although not shown, the sheet is conveyed to the fixing unit and is discharged outside the apparatus after the image is fixed.
[0038]
【The invention's effect】
As apparent from the above description, in the first aspect of the present invention, in the case of continuously feeding paper, after feeding the first sheet, the second sheet is fed until the trailing edge of the sheet is detected. Avoid jam detection. As a result, when a size error is detected when the trailing edge of the sheet is detected, the second sheet is not jammed and the operability is improved by eliminating the operation for releasing the jam.
[0039]
According to a second aspect of the invention, in the image forming apparatus according to claim 1, wherein, in the case of continuously printed, after feeding the first sheet is to detect the trailing end of the sheet 2 sheet of paper feed jam If the size measured at the time of detecting the trailing edge of the paper is longer than the specified size, the second sheet is not jammed, and the operation for removing the jam is eliminated. improves.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a configuration example of an embodiment of an image forming apparatus of the present invention.
FIG. 2 is a block diagram illustrating a configuration example of a control system according to the embodiment.
FIG. 3 is a flowchart showing an operation example related to the present invention .
FIG. 4 is a flowchart showing an operation example related to claim 1 ;
FIG. 5 is a flowchart showing an operation example related to claim 2 ;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus housing 2 Image forming section 3 Photoconductor 4 Charging roller 5 Writing unit 6 Developing unit 7 Transfer roller 8 Cleaning unit 9 Paper transport path 10 Fixing unit 11 Paper discharge tray 12 Paper discharge path 13 Reverse path 14 Switching claw DESCRIPTION OF SYMBOLS 15 Duplex unit 16 Manual feed tray 17 Paper feed roller 19 Paper feed tray 20 Paper feed path 21 Paper feed roller 22 Registration roller 23 Main control part 24 High voltage drive part 25 Motor 26 Driver 27 Paper feed clutch 28 Driver 29 Controller 30 Sensor

Claims (2)

A paper source that stores paper,
Means for designating the size of the stored paper;
A paper feed roller for feeding paper one by one from the paper feed unit;
A function unit for temporarily stopping the transported paper by a registration roller for aligning the image writing position, and then starting the operation again;
A sensor for detecting that the paper has reached or passed a registration position;
Means for detecting the length of the paper simultaneously with the detection of the trailing edge of the paper being conveyed by the sensor,
In the case of continuous paper feeding, after the first sheet is fed, the second sheet jam detection is not performed until the trailing edge of the sheet is detected, and the size measurement result based on the trailing edge detection is set. An image forming apparatus that cancels the detection of a paper jam at the second sheet when the size is different from the selected size. If the measured sheet size is longer than the specified size, the image forming apparatus according to claim 1, wherein the releasing the second sheet feed jam.

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