JPH0569989A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To sense the paper jamming by further feeding a paper through operation of a control means and stopping the operation of the image forming apparatus in a condition thereof permitting sensing the paper by a sensing means when some abnormality occurs and the operation is stopped. CONSTITUTION:The image forming apparatus is provided with a paper feed means 1 for feeding a paper along a paper passageway, a sensing means 2 for sensing the paper jamming in the paper passageway, and a control means for controlling the drive of the paper feed means 1 in response to an output signal from the sensing means 2. If the necessity arises of stopping all the operation of the image forming apparatus after feeding of a paper by the paper feed means 1 and before sensing of the paper by the sensing means, the control means operates to further drive the paper feed means 1 so as to feed until the paper is sensed by the sensing means 2. Thus, the operation of the image forming apparatus is stopped in a condition permitting the paper to be sensed by the sensing means 2. Resultantly, the jam sensing becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding means for feeding a sheet along a sheet passage, and a detecting means which is present near the sheet passage and detects a jam of the sheet in the sheet passage. The present invention relates to an image forming apparatus including a control unit that receives an output signal of a detection unit and controls driving of a sheet feeding unit.

[0002]

2. Description of the Related Art A case where some abnormality occurs during a paper feeding operation will be described with reference to FIG. For example, when a jam occurs during the continuous paper feeding operation, the paper feeding roller (1), which is a paper feeding means formed at the upper part of a paper feeding cassette (not shown), causes Even when the first sensor (2) which is the detection means is not detecting the sheet while the sheet is being fed, the conventional method immediately stops all the sheet feeding operations of the image forming apparatus. ..

As described above, conventionally, some abnormality occurs,
When it is necessary to stop all the operations of the image forming apparatus, the operation of the image forming apparatus is immediately stopped regardless of the state of the paper.

[0004]

However, when some abnormality occurs and the operation of the image forming apparatus is stopped, the paper may stop in the paper feed passage between the paper feed means and the detection means. is there. At that time, if the sheet is not detected and stopped by the detecting means, the jam cannot be detected. Therefore, when an abnormality occurs, some abnormality is notified by the warning means of the apparatus main body that is displayed or sounded, but the stopped paper remains in the paper feed passage between the paper feed means and the detection means. No information is given.

Here, the operator solves the cause of any abnormality that was notified, but when the image formation is started again after that, the paper stopped in the paper feed passage between the paper feed means and the detection means causes Jam occurs. Alternatively, image formation is originally performed in which the vertical position is shifted downward in the paper feeding direction with respect to the position of the sheet on which image formation is desired. This is a phenomenon that occurs because the paper is fed too much.

Further, in the case of a paper feeding device having a front loading function for pulling out the paper feeding cassette in a direction orthogonal to the paper feeding direction, paper is jammed when the paper feeding device including the paper feeding cassette is opened and closed. There are drawbacks such that the device cannot be opened and closed easily and paper cannot be pulled out.

The above problem can be solved by providing a large number of detecting means, but the use of a large number of detecting means has a drawback that the cost of the image forming apparatus main body increases.

According to the present invention, when an abnormality occurs and the operation of the image forming apparatus is stopped, the paper is further fed and stopped in a state where it is detected by the detecting means, so that the jam can be detected. It is an object of the present invention to provide an image forming apparatus having the following.

[0009]

According to the present invention, there is provided a sheet feeding means (1) for feeding a sheet along a sheet passage and a sheet feeding means (1) existing in the vicinity of the sheet feeding means (1). Detecting means (2) for detecting paper jam and the detecting means (2)
In the image forming apparatus having a control means for controlling the drive of the paper feeding means (1), the paper is fed by the paper feeding means (1), and the paper is detected by the detecting means ( If it is necessary to stop all the operations of the image forming apparatus before the detection by 2), the sheet feeding means (1) is further driven to detect the sheet as the detection means (2).
The image forming apparatus is provided with a control unit that feeds the sheet until the sheet is detected by the control unit and stops the operation of the image forming apparatus when the sheet is detected by the detecting unit (2). Is.

[0010]

According to the present invention, the paper fed by the paper feeding means is present in the vicinity of the paper feeding means, and some abnormality occurs before reaching the detection means for detecting the jam of the paper.
When it is necessary to stop all the operations of the main body of the device, the paper is fed until the detection means detects it, then
The operation of the apparatus main body is stopped.

By including the above-mentioned control means, it is possible to detect that the paper is jammed without stopping between the paper feeding means and the detection means. Therefore, a halfway sheet stopped between the sheet feeding unit and the detection unit does not perform the sheet feeding operation along the sheet path for image formation again. Therefore, it is possible to form an image in which the vertical position of the sheet in the sheet feeding direction is not displaced with respect to the position of the sheet on which the image is to be formed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a sheet feeding portion in an image forming apparatus. The outline of the present invention will be described below with reference to FIG.

(1) is a paper feed roller for feeding paper. (2) is a first sensor formed near the paper feed roller. (3) is a paper feed clutch for feeding the paper fed by the paper feed roller (2). Reference numeral (4) is a registration roller for keeping the paper fed from the paper feed clutch (3) on standby for a certain time and aligning the leading ends of the paper.
(5) is a second sensor formed upstream of the registration roller (4) in the feeding direction. (6) is a photosensitive drum. (7) is a third sensor formed on the downstream side of the photosensitive drum (6) in the feeding direction. The broken line indicates the paper feed path.

A case will be described in which some abnormality occurs during the paper feeding operation. Abnormalities when all operations of the image forming apparatus must be stopped include A and abnormalities when a jam occurs. B, Abnormality when the transfer material runs out. C, Abnormality when maintenance is required due to wear of parts of the device body. Etc.

The feeding operation of continuous paper will be described.

The time to start the paper feeding operation for the second and subsequent sheets is
When the trailing edge of the downstream side paper passes the second sensor (4), it is time to start the feeding operation of the upstream side paper. The paper on the downstream side is fed from the left side to the right side in the figure along the conveying path by the sheet feeding roller (1), and when the leading edge of the sheet reaches the corner, the sheet is fed from the lower side to the upper side in the figure. It Next, the leading edge of the sheet is detected by the first sensor (2), then the sheet is fed by the paper feed clutch (3), and when it reaches a corner, the sheet is fed from the right side to the left side in the drawing. The leading edge of the sheet is detected by the second sensor (4), stopped by the registration roller (5) for a certain period of time in order to align the leading edge, and after a certain period of time, fed toward the photosensitive drum (6). .. When the trailing edge of the sheet passes the second sensor (4), the feeding operation of the upstream sheet is started as described above. The paper on the upstream side is fed in the same manner as the paper on the downstream side. The sheet on the downstream side has the latent image transferred below the photosensitive drum (6) and passes through the third sensor (7).

Here, it is assumed that some sort of abnormality occurs when a jam occurs due to the detection of the third sensor (7). The paper feed roller (1), which is a paper feed means formed above the paper feed cassette (not shown), is in the process of feeding the paper on the upstream side, and is still the detection means. In the state where the sensor (2) does not detect the upstream paper, the paper feed roller (1) is kept until the first sensor (2) detects the paper before stopping the paper feeding operation of the image forming apparatus. To drive. After that, all the paper feeding operations of the image forming apparatus are stopped.

In the present invention, when some abnormality occurs and all the operations of the image forming apparatus must be stopped, if the paper feed roller (1) is driven, the first sensor (2) is activated. The paper feed roller (1) is driven until the paper is detected. After that, the operation of the image forming apparatus is stopped.

FIG. 2 is a block diagram of a control device of the image forming apparatus. It will be described below with reference to FIG.

The image forming apparatus is controlled by a microcomputer system including the MPU (100). This microcomputer system includes an MPU (100), a ROM (102) connected to the MPU (100) for storing a control program, and an MPU.
RAM (10) for temporarily storing data and the like during control by (100) and having a plurality of flag areas necessary for control
4) and an I / O interface (106) for the MPU (100) to perform input / output control of an internal device formed inside the main body of the device.

The normal power source of the RAM (104) is the constant voltage power source Vcc. A backup battery (116) such as a lithium battery is connected by a branched wiring between the power supply pin of the RAM (104) and the constant voltage power supply Vcc. When the constant voltage power supply Vcc is no longer supplied, the voltage of the backup battery (116) is changed to the RAM (10
Given to 4). Therefore, even if the main switch of the power supply of the apparatus main body is turned off, the data in the RAM (104) is retained.

A sensor circuit (112) is connected to the input port of the I / O interface (106), and the output of the jam sensor or the like is input. Also, I /
A plurality of drive devices (114) are connected to the output port of the O interface (106).

Next, the MPU (10
The control procedure (0) will be described with reference to the flowcharts shown in FIGS. 3, 4, and 5.

FIG. 3 is a flow chart showing the main routine. First, the operation of the main routine is started, and the interrupt of the interrupt routine described later is enabled (S10).
1). After that, an image forming operation for carrying a sheet, performing a series of image forming processes, and the like is performed (S103). Next, it is determined whether or not to perform a continuous image forming operation (S10).
5).

Here, if a continuous image forming operation is to be performed, YES is determined, and in order to repeat the image forming, the process returns to the image forming operation (S103) and the image forming operation is repeated. If the continuous image forming operation is not performed, NO
Then, the main routine is ended.

FIG. 4 is a flowchart showing the interrupt routine. In the main routine, when the interruption of the interruption routine is permitted (S101), the interruption routine is started, and all the interruption routines necessary for the image forming operation are performed (S201). A part of all the interrupt routines includes a routine group that detects that some abnormality has occurred. When it is detected that some kind of abnormality has occurred, the value of the abnormality flag, which is normally 0 at a predetermined address of the RAM (104) and which is the judgment that the abnormality has occurred, is set to 1. A jam flag is also included in the abnormality flags.

In the routine group for detecting the occurrence of any abnormality, it is of course necessary to determine whether or not a jam has occurred between the sheet feeding operation for feeding the sheet along the sheet path and the sheet discharging operation for discharging the sheet. It also includes a group of routines that detect whether or not it is occurring. When a jam is detected, the value of the jam flag, which is normally 0 at a predetermined address of the RAM (104) and which is a determination that a jam has occurred, is set to 1.

When the processing group of all interrupt routines is completed, it is determined whether or not the value of the abnormality flag for abnormality determination is 0 (S203). Here, if the value of the abnormality flag is 0, it is determined to be YES, and the interrupt routine is exited without doing anything. If the value of the abnormality flag is not 0, it is determined to be NO, and the process proceeds to a subroutine (S205) for stopping all the image forming apparatuses.

FIG. 5 is a flow chart showing a subroutine for stopping all the image forming apparatuses. When the subroutine is started, it is determined whether or not the drive of the paper feed roller (1) is in the ON state (S3).
01). Here, if it is not in the ON state where the paper feed roller (1) is being driven, it is determined to be NO, and immediately all of the main motor, the clutch and the like are stopped (S305).
Then, this subroutine is finished and the process returns to the interrupt routine. When the continuous image forming operation is being performed, the state in which the paper feed roller (1) is not driven is
There are two types of states: The first state is a state where there is no paper between the paper feed roller (1) and a first sensor (2) that is present near the paper feed roller (1) and detects the presence or absence of paper. The second state is a state in which the paper is conveyed by driving the paper feed clutch (3) formed on the downstream side of the paper path without driving the paper feed roller (1). Therefore, all the main motors and clutches are immediately stopped (S305). Then, this subroutine is finished and the process returns to the interrupt routine.

Here, it is determined to be YES when the sheet feeding roller (1) is being driven and is in the ON state, and it is determined whether or not the first sensor (2) is in the ON state ( S303). Here, if the first sensor (2) is not in the ON state, it is determined as NO, and the sheet is detected by the first sensor (2).
Until the first sensor (2) is detected, the process of determining whether or not the first sensor (2) is in the ON state (S303) is repeated.
When the sheet is detected by the first sensor (2), that is, when the first sensor (2) is in the ON state, YES is determined and the process proceeds to the next process. All of the main motor and clutch are stopped (S305). Then, this subroutine is finished and the process returns to the interrupt routine.

[0031]

According to the present invention, the sheet fed by the sheet feeding means exists near the sheet feeding means and reaches the detecting means for detecting the jam of the sheet in the sheet path.
When some abnormality occurs and it is necessary to stop all the operations of the apparatus main body, it is provided with control means for stopping the operation of the apparatus main body after the sheet is detected by the detection section.

By including the above-mentioned control means, it is possible to detect that the paper is jammed without stopping between the paper feeding means and the detection means. Therefore, a halfway sheet stopped between the sheet feeding unit and the detection unit does not perform the sheet feeding operation along the sheet path for image formation again. Therefore, it is possible to form an image in which the vertical position of the sheet in the sheet feeding direction is not displaced with respect to the position of the sheet on which the image is to be formed.

It is possible to notify the operator of the occurrence of some abnormality and the presence of jammed paper near the detection means through a warning means for giving a warning by display or voice.

Further, in the case of the paper feeding device having the front loading function, when the abnormality is solved and the jammed paper is removed according to the warning means, the paper feeding device including the paper feeding cassette is opened and closed. Can be opened and closed easily.

Further, it is not necessary to increase the number of detecting means,
Since the conventional detecting means is used, the cost of the image forming apparatus main body can be maintained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sheet feeding portion in an image forming apparatus of the present invention.

FIG. 2 is a block diagram of a control device of the image forming apparatus of the present invention.

FIG. 3 is a flowchart showing a main routine of the present invention.

FIG. 4 is a flowchart showing an interrupt routine of the present invention.

FIG. 5 is a flowchart showing a subroutine of the present invention.

[Explanation of symbols]

 1 Paper Feed Roller 2 Sensor 100 MPU 102 ROM 104 RAM 106 I / O Interface 112 Sensor Circuit 114 Plural Drive Devices

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[Procedure amendment]

[Submission date] September 25, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Added

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding means for feeding a sheet along a sheet passage, and a detecting means which is present near the sheet passage and detects a jam of the sheet in the sheet passage. The present invention relates to an image forming apparatus including a control unit that receives an output signal of a detection unit and controls driving of a sheet feeding unit.

[0002]

2. Description of the Related Art A case where some abnormality occurs during a paper feeding operation will be described with reference to FIG. For example, when a jam occurs during the continuous paper feeding operation, the paper feeding roller (1), which is a paper feeding means formed at the upper part of a paper feeding cassette (not shown), causes Even when the first sensor (2) which is the detection means is not detecting the sheet while the sheet is being fed, the conventional method immediately stops all the sheet feeding operations of the image forming apparatus. ..

As described above, conventionally, some abnormality occurs,
When it is necessary to stop all the operations of the image forming apparatus, the operation of the image forming apparatus is immediately stopped regardless of the state of the paper.

[0004]

However, when some abnormality occurs and the operation of the image forming apparatus is stopped, the paper may stop in the paper feed passage between the paper feed means and the detection means. is there. At that time, if the sheet is not detected and stopped by the detecting means, the jam cannot be detected. Therefore, when an abnormality occurs, some abnormality is notified by the warning means of the apparatus main body that is displayed or sounded, but the stopped paper remains in the paper feed passage between the paper feed means and the detection means. No information is given.

Here, the operator solves the cause of any abnormality that was notified, but when the image formation is started again after that, the paper stopped in the paper feed passage between the paper feed means and the detection means causes Jam occurs. Alternatively, image formation is originally performed in which the vertical position is shifted downward in the paper feeding direction with respect to the position of the sheet on which image formation is desired. This is a phenomenon that occurs because the paper is fed too much.

Further, in the case of a paper feeding device having a front loading function for pulling out the paper feeding cassette in a direction orthogonal to the paper feeding direction, paper is jammed when the paper feeding device including the paper feeding cassette is opened and closed. There are drawbacks such that the device cannot be opened and closed easily and paper cannot be pulled out.

The above problem can be solved by providing a large number of detecting means, but the use of a large number of detecting means has a drawback that the cost of the image forming apparatus main body increases.

According to the present invention, when an abnormality occurs and the operation of the image forming apparatus is stopped, the paper is further fed and stopped in a state where it is detected by the detecting means, so that the jam can be detected. It is an object of the present invention to provide an image forming apparatus having the following.

[0009]

According to the present invention, there is provided a sheet feeding means (1) for feeding a sheet along a sheet passage and a sheet feeding means (1) existing in the vicinity of the sheet feeding means (1). Detecting means (2) for detecting paper jam and the detecting means (2)
In the image forming apparatus having a control means for controlling the drive of the paper feeding means (1), the paper is fed by the paper feeding means (1), and the paper is detected by the detecting means ( If it is necessary to stop all the operations of the image forming apparatus before the detection by 2), the sheet feeding means (1) is further driven to detect the sheet as the detection means (2).
The image forming apparatus is provided with a control unit that feeds the sheet until the sheet is detected by the control unit and stops the operation of the image forming apparatus when the sheet is detected by the detecting unit (2). Is.

[0010]

According to the present invention, the paper fed by the paper feeding means is present in the vicinity of the paper feeding means, and some abnormality occurs before reaching the detection means for detecting the jam of the paper.
When it is necessary to stop all the operations of the main body of the device, the paper is fed until the detection means detects it, then
The operation of the apparatus main body is stopped.

By including the above-mentioned control means, it is possible to detect that the paper is jammed without stopping between the paper feeding means and the detection means. Therefore, a halfway sheet stopped between the sheet feeding unit and the detection unit does not perform the sheet feeding operation along the sheet path for image formation again. Therefore, it is possible to form an image in which the vertical position of the sheet in the sheet feeding direction is not displaced with respect to the position of the sheet on which the image is to be formed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a sheet feeding portion in an image forming apparatus. The outline of the present invention will be described below with reference to FIG.

(1) is a paper feed roller for feeding paper. (2) is a first sensor formed near the paper feed roller. (3) is a paper feed clutch for feeding the paper fed by the paper feed roller (2). Reference numeral (4) is a registration roller for keeping the paper fed from the paper feed clutch (3) on standby for a certain time and aligning the leading ends of the paper.
(5) is a second sensor formed upstream of the registration roller (4) in the feeding direction. (6) is a photosensitive drum. (7) is a third sensor formed on the downstream side of the photosensitive drum (6) in the feeding direction. The broken line indicates the paper feed path.

A case will be described in which some abnormality occurs during the paper feeding operation. Abnormalities when all operations of the image forming apparatus must be stopped include A and abnormalities when a jam occurs. B, Abnormality when the transfer material runs out. C, Abnormality when maintenance is required due to wear of parts of the device body. Etc.

The feeding operation of continuous paper will be described.

The time to start the paper feeding operation for the second and subsequent sheets is
When the trailing edge of the downstream side paper passes the second sensor (4), it is time to start the feeding operation of the upstream side paper. The paper on the downstream side is fed from the left side to the right side in the figure along the conveying path by the sheet feeding roller (1), and when the leading edge of the sheet reaches the corner, the sheet is fed from the lower side to the upper side in the figure. It Next, the leading edge of the sheet is detected by the first sensor (2), then the sheet is fed by the paper feed clutch (3), and when it reaches a corner, the sheet is fed from the right side to the left side in the drawing. The leading edge of the sheet is detected by the second sensor (4), stopped by the registration roller (5) for a certain period of time in order to align the leading edge, and after a certain period of time, fed toward the photosensitive drum (6). .. When the trailing edge of the sheet passes the second sensor (4), the feeding operation of the upstream sheet is started as described above. The paper on the upstream side is fed in the same manner as the paper on the downstream side. The sheet on the downstream side has the latent image transferred below the photosensitive drum (6) and passes through the third sensor (7).

Here, it is assumed that some sort of abnormality occurs when a jam occurs due to the detection of the third sensor (7). The paper feed roller (1), which is a paper feed means formed above the paper feed cassette (not shown), is in the process of feeding the paper on the upstream side, and is still the detection means. In the state where the sensor (2) does not detect the upstream paper, the paper feed roller (1) is kept until the first sensor (2) detects the paper before stopping the paper feeding operation of the image forming apparatus. To drive. After that, all the paper feeding operations of the image forming apparatus are stopped.

In the present invention, when some abnormality occurs and all the operations of the image forming apparatus must be stopped, if the paper feed roller (1) is driven, the first sensor (2) is activated. The paper feed roller (1) is driven until the paper is detected. After that, the operation of the image forming apparatus is stopped.

FIG. 2 is a block diagram of a control device of the image forming apparatus. It will be described below with reference to FIG.

The image forming apparatus is controlled by a microcomputer system including the MPU (100). This microcomputer system includes an MPU (100), a ROM (102) connected to the MPU (100) for storing a control program, and an MPU.
RAM (10) for temporarily storing data and the like during control by (100) and having a plurality of flag areas necessary for control
4) and an I / O interface (106) for the MPU (100) to perform input / output control of an internal device formed inside the main body of the device.

The normal power source of the RAM (104) is the constant voltage power source Vcc. A backup battery (116) such as a lithium battery is connected by a branched wiring between the power supply pin of the RAM (104) and the constant voltage power supply Vcc. When the constant voltage power supply Vcc is no longer supplied, the voltage of the backup battery (116) is changed to the RAM (10
Given to 4). Therefore, even if the main switch of the power supply of the apparatus main body is turned off, the data in the RAM (104) is retained.

A sensor circuit (112) is connected to the input port of the I / O interface (106), and the output of the jam sensor or the like is input. Also, I /
A plurality of drive devices (114) are connected to the output port of the O interface (106).

Next, the MPU (10
The control procedure (0) will be described with reference to the flowcharts shown in FIGS. 3, 4, and 5.

FIG. 3 is a flow chart showing the main routine. First, the operation of the main routine is started, and the interrupt of the interrupt routine described later is enabled (S10).
1). After that, an image forming operation for carrying a sheet, performing a series of image forming processes, and the like is performed (S103). Next, it is determined whether or not to perform a continuous image forming operation (S10).
5).

Here, if a continuous image forming operation is to be performed, YES is determined, and in order to repeat the image forming, the process returns to the image forming operation (S103) and the image forming operation is repeated. If the continuous image forming operation is not performed, NO
Then, the main routine is ended.

FIG. 4 is a flowchart showing the interrupt routine. In the main routine, when the interruption of the interruption routine is permitted (S101), the interruption routine is started, and all the interruption routines necessary for the image forming operation are performed (S201). A part of all the interrupt routines includes a routine group that detects that some abnormality has occurred. When it is detected that some kind of abnormality has occurred, the value of the abnormality flag, which is normally 0 at a predetermined address of the RAM (104) and which is the judgment that the abnormality has occurred, is set to 1. A jam flag is also included in the abnormality flags.

In the routine group for detecting the occurrence of any abnormality, it is of course necessary to determine whether or not a jam has occurred between the sheet feeding operation for feeding the sheet along the sheet path and the sheet discharging operation for discharging the sheet. It also includes a group of routines that detect whether or not it is occurring. When a jam is detected, the value of the jam flag, which is normally 0 at a predetermined address of the RAM (104) and which is a determination that a jam has occurred, is set to 1.

When the processing group of all interrupt routines is completed, it is determined whether or not the value of the abnormality flag for abnormality determination is 0 (S203). Here, if the value of the abnormality flag is 0, it is determined to be YES, and the interrupt routine is exited without doing anything. If the value of the abnormality flag is not 0, it is determined to be NO, and the process proceeds to a subroutine (S205) for stopping all the image forming apparatuses.

FIG. 5 is a flow chart showing a subroutine for stopping all the image forming apparatuses. When the subroutine is started, it is determined whether or not the drive of the paper feed roller (1) is in the ON state (S3).
01). Here, if it is not in the ON state where the paper feed roller (1) is being driven, it is determined to be NO, and immediately all of the main motor, the clutch and the like are stopped (S305).
Then, this subroutine is finished and the process returns to the interrupt routine. When the continuous image forming operation is being performed, the state in which the paper feed roller (1) is not driven is
There are two types of states: The first state is a state where there is no paper between the paper feed roller (1) and a first sensor (2) that is present near the paper feed roller (1) and detects the presence or absence of paper. The second state is a state in which the paper is conveyed by driving the paper feed clutch (3) formed on the downstream side of the paper path without driving the paper feed roller (1). Therefore, all the main motors and clutches are immediately stopped (S305). Then, this subroutine is finished and the process returns to the interrupt routine.

Here, it is determined to be YES when the sheet feeding roller (1) is being driven and is in the ON state, and it is determined whether or not the first sensor (2) is in the ON state ( S303). Here, if the first sensor (2) is not in the ON state, it is determined as NO, and the sheet is detected by the first sensor (2).
Until the first sensor (2) is detected, the process of determining whether or not the first sensor (2) is in the ON state (S303) is repeated.
When the sheet is detected by the first sensor (2), that is, when the first sensor (2) is in the ON state, YES is determined and the process proceeds to the next process. All of the main motor and clutch are stopped (S305). Then, this subroutine is finished and the process returns to the interrupt routine.

[0031]

According to the present invention, the sheet fed by the sheet feeding means exists near the sheet feeding means and reaches the detecting means for detecting the jam of the sheet in the sheet path.
When some abnormality occurs and it is necessary to stop all the operations of the apparatus main body, it is provided with control means for stopping the operation of the apparatus main body after the sheet is detected by the detection section.

By including the above-mentioned control means, it is possible to detect that the paper is jammed without stopping between the paper feeding means and the detection means. Therefore, a halfway sheet stopped between the sheet feeding unit and the detection unit does not perform the sheet feeding operation along the sheet path for image formation again. Therefore, it is possible to form an image in which the vertical position of the sheet in the sheet feeding direction is not displaced with respect to the position of the sheet on which the image is to be formed.

It is possible to notify the operator of the occurrence of some abnormality and the presence of jammed paper near the detection means through a warning means for giving a warning by display or voice.

Further, in the case of the paper feeding device having the front loading function, when the abnormality is solved and the jammed paper is removed according to the warning means, the paper feeding device including the paper feeding cassette is opened and closed. Can be opened and closed easily.

Further, it is not necessary to increase the number of detecting means,
Since the conventional detecting means is used, the cost of the image forming apparatus main body can be maintained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 15/00 102 8004-2H 112 7369-2H

Claims (1)

[Claims] 1. A paper feed means (1) for feeding a paper along a paper path, and a detection means which is present in the vicinity of the paper feed means (1) and detects a paper jam in the paper path. An image forming apparatus comprising: (2) and a control unit that receives the output signal of the detection unit (2) and controls the drive of the sheet feeding unit (1), If it is necessary to stop all the operations of the image forming apparatus after the paper is fed and before the paper is detected by the detection means (2), the paper feed means (1) is further driven. And a control unit that feeds the sheet until the detection unit (2) detects the sheet and stops the operation of the image forming apparatus when the sheet is detected by the detection unit (2). An image forming apparatus characterized in that