JP2002053233A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of achieving the maximum throughput without increasing the jam generation probability and the production cost even when the feed carrying passage L is longer than the sum of the sheet length and the distance between paper sheets. SOLUTION: This image forming device comprises a control means for performing the control of starting the feed of the sheet before a predetermined time elapses after the preceding sheet is fed out by a sheet feeding means. The control means performs the control that the feed of the next sheet is the re-feed of the preceding sheet if the preceding sheet is not detected by a sheet detecting means within a predetermined time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam printer, a facsimile machine, and a copying machine in which a feeding operation is performed a plurality of times to improve a feeding performance in order to remedy a jam caused by a feeding defect. And the like.

[0002]

2. Description of the Related Art A conventional image forming apparatus will be described using a laser beam printer as an example with reference to FIG. FIG.
In the image forming apparatus shown in FIG.
The sheet feeding operation is performed by rotating the pickup roller 102 once, separating the sheet S stacked on the cassette 101 serving as the sheet stacking unit into one sheet by the separation claw 103, and then feeding the sheet S to the feed roller 104 and the retard roller 105. Feed roller
104 rotates in the transport direction, and the retard roller 105 rotates in the reverse direction to the transport direction, thereby separating the sheet S that cannot be completely separated by the separation claw 103, and reliably transporting one sheet to the transport roller 10
Transfer to 6.

When the pre-feed sensor 108 detects the leading end, the driving of the transport roller 106, the feed roller 104, and the retard roller 105 is stopped, and the feeding operation ends. Then, conveyance of the sheet is restarted in synchronization with the image forming process by the image forming unit 100, and the sheet S is sent to the pre-transfer roller 107. When the top sensor 109 detects the leading edge of the sheet, it outputs a TOP signal to perform image formation. In the case where image formation is performed continuously, by driving the pickup roller 102 after a lapse of a predetermined time from the TOP signal of the preceding sheet, the sheet interval can be reduced, and the number of images formed per unit time can be increased.

In such an apparatus, the pickup roller 102
When the pre-feed sensor 108 does not detect the leading edge of the sheet within a predetermined time from the start of the driving of the
Is determined to be a feeding failure due to a nail pull-out failure that cannot go over, and a re-feeding operation is performed. This re-feeding operation rotates the pickup roller 102 by one rotation as in the normal feeding operation, thereby reducing the probability of occurrence of jam and improving the reliability of feeding.

[0005]

Incidentally, in many of the conventional apparatuses, a separation sensor 110 is provided immediately after the retard roller 105, but in recent years, in order to reduce production costs,
In many cases, no sensor is provided up to the position of the pre-feed sensor 108.

However, in such a configuration, the feed start timing of the succeeding sheet in the case of continuously forming images is after a predetermined time has elapsed from the start of recording of the preceding sheet (TOP signal output). I have. Therefore, the cassette 101
From the standby position of the stacked sheets, that is, the leading end of the sheets stacked on the cassette 101,
If the feeding conveyance path is longer than the sheet length + predetermined sheet distance, there arises a problem that the sheet interval becomes unnecessarily large and the number of sheets that can form an image per unit time decreases.

Therefore, according to the present invention, the feeding / conveying path has a sheet length +
It is an object of the present invention to provide an image forming apparatus that can increase the number of image formations per unit time even when the distance is longer than the sheet distance.

[0008]

In order to solve the above-mentioned problems, a typical configuration of an image forming apparatus according to the present invention includes a sheet stacking unit for stacking sheets, and one sheet from the sheet stacking unit. Sheet feeding means for feeding, and sheet detecting means for detecting a sheet fed from the sheet feeding means, between a sheet stacking front end of the sheet stacking means and the sheet detecting means. If the feeding conveyance path is longer than the length of the sheet to be fed in the feeding direction, and the sheet is not detected by the sheet detecting means within a predetermined time after the sheet is fed by the sheet feeding means, it is determined that the feeding is defective. In the image forming apparatus to determine, at the time of continuous image formation, after sending out the preceding sheet by the sheet feeding means,
A control unit for performing a control to start feeding of a next sheet before the predetermined time has elapsed, wherein the control unit determines that the preceding sheet is not detected by the sheet detection unit within the predetermined time. The control is performed such that the feeding operation of the next sheet is set as the re-feeding operation of the preceding sheet.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a control block diagram of the image forming apparatus, and FIG. 3 is a flowchart illustrating a feeding operation.

The image forming apparatus shown in FIG. 1 is a laser beam printer, and has a photosensitive drum 2 as an electrostatic image carrier inside a process cartridge 1 as an image forming unit. The photosensitive drum 2 is uniformly charged by the charging roller 3, an electrostatic latent image is formed by the laser beam 8 emitted from the semiconductor laser 5, and the electrostatic latent image is visualized by the developing device 4 to form a toner image. It is formed. The laser beam 8 emitted from the semiconductor laser 5 is reflected by the rotating polygon mirror 7 rotated by the scanner motor 6 and scans the photosensitive drum 2.

The toner image formed on the photosensitive drum 2 is transferred onto the sheet S conveyed by the transfer roller 9, and is fixed by being heated and pressed by a fixing device 10. The sheet S on which the image is fixed is discharged out of the apparatus by the discharge roller 11.

A cassette 12, which is a sheet stacking means for stacking the sheets S to be fed to the image forming section, is disposed at a lower portion of the apparatus, and the cassette 12 has a function of identifying a sheet size. The stacked sheets S are sent out by one rotation of the pickup roller 13 as sheet feeding means. A manual feed port 14 having no function of identifying the size of the sheet is provided on the side of the apparatus. The sheets S stacked here are fed by a manual feed roller 15.

The sheet S sent by one rotation of the pickup roller 13 is separated by a separation claw 16 and fed to a feed roller 17 rotating in the transport direction and a retard roller 18 rotating in the opposite direction to the transport direction. The feed roller 17 rotates in the transport direction, and the retard roller 18 can rotate in the reverse direction to the transport direction, thereby separating the sheet S that could not be separated by the separation claw 16 and reliably transporting one sheet to the transport roller 19. Transport to

A pre-feed sensor 20 as a sheet detecting means is disposed upstream of the pre-transfer roller 21 for feeding the conveyed sheet to the photosensitive drum 2 in the conveying direction, and detects a leading end and a trailing end of the sheet S. . On the downstream side of the pre-transfer roller 21 in the transport direction, a top sensor 22 for synchronizing the image formation by the photosensitive drum 2 and the sheet transport and measuring the length of the fed sheet S in the transport direction is disposed. Have been.

In FIG. 1, a standby position of the stacked sheets of the cassette 12, that is,
The feeding conveyance path L1 up to the length of one sheet to be conveyed is +
It is longer than the sheet distance to achieve the maximum throughput. Therefore, when image formation is performed continuously, the feeding operation is performed so that the feeding of the succeeding sheet is started after a lapse of a predetermined time from the start of feeding of the preceding sheet.

FIG. 2 is a block diagram showing a circuit configuration of a control means for controlling the above-mentioned mechanism. As shown in FIG. 2, the printer controller 23 develops image code data sent from an external device such as a host computer (not shown) into bit data necessary for recording in the printer, reads internal information of the printer, and displays the information.

A printer engine control section 24 connected to the printer controller 23 controls the operation of each section of the printer engine in accordance with an instruction from the printer controller 23 and notifies the printer controller 23 of printer internal information. The sheet transport controller 25 is a printer engine controller 24
In accordance with the instruction, the motors and rollers of each section are driven and stopped for sheet conveyance. The high voltage control unit 26 is charged, developed,
Each high-voltage output control in each step such as transfer is performed in accordance with an instruction from the printer engine control unit 24. The optical system control unit 27 controls driving and stopping of the scanner motor 6 and lighting of the laser beam 8 in accordance with an instruction from the printer engine control unit 24. The fixing unit control unit 28 drives and stops energization of the heater of the fixing unit 10 in accordance with an instruction from the printer engine control unit 24.

The feeding operation according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, first, the pickup roller 13 is rotated once (S1), and the sheets stacked on the cassette 12 are sent out. Then, while waiting for a predetermined time from the start of feeding, that is, the time for determining that the feeding is defective, the leading edge of the sheet is detected by the pre-feed sensor 20 (S2).

If the pre-feed sensor 20 detects the leading edge of the sheet before the predetermined time has elapsed, it is determined that normal feeding has been performed, and the feeding operation is terminated (S3). On the other hand, if the pre-feed sensor 20 cannot detect the leading edge of the sheet before the predetermined time has elapsed, it is determined that the feeding is defective.

When it is determined that the feeding is defective, it is first determined whether or not the feeding operation of the succeeding sheet is started (S).
5). When the feeding operation of the succeeding sheet has not been started, it is determined that the preceding sheet which cannot be detected within the predetermined time exists in the cassette 12, and the refeeding operation is started (S6). The re-feeding operation (S6) is performed by the pickup roller 13
Is rotated once, and it is confirmed whether or not the pre-feed sensor 20 detects the leading edge of the sheet (S7) before a predetermined time elapses (S9), similarly to S2, S3, and S4 described above.

Then, within a predetermined time, the pre-feed sensor 20
If the sheet has detected the leading edge of the sheet, it is determined that the sheet has been normally fed by the re-feeding operation, and the feeding operation is terminated (S8). On the other hand, if the pre-feed sensor 20 cannot detect the leading edge of the sheet within the predetermined time, it is determined that the feeding is defective (S10).

If the feeding operation of the succeeding sheet has already started in S5, control is performed to replace the feeding operation with the refeeding operation of the preceding sheet. When the leading edge of the preceding sheet is detected by the pre-feed sensor 20 (S11) before the lapse of a predetermined time (S12) from the timing when the replaced feeding operation is started, the trailing edge of the sheet is sufficient for the separation claw. Wait for the time to pass (S14)
Further, the feeding operation of the next succeeding sheet is started (S15).
If the pre-feed sensor 20 does not detect the leading edge of the sheet before the predetermined time elapses (S12) (S11), it is determined that the feeding is defective (S13).

As described above, even in an apparatus in which the feeding / conveying path is long and only the pre-feed sensor is provided, the apparatus which starts the feeding operation of the next sheet with reference to the timing of the feeding operation of the sheet may be used. Is not detected within the predetermined time by the pre-feed sensor 20, the feeding operation for the next sheet is treated as the re-feeding operation of the preceding sheet, so that it is not necessary to provide an unnecessarily long sheet interval, and the The number of formed images can be increased.

The above-described control is also performed by an apparatus that starts the feeding operation of the next sheet based on the timing of the feeding operation of the sheet, with a configuration in which the feeding conveyance path is long and only the pre-feed sensor is provided. Thus, it is possible to detect a feeding failure or a jam, and it is not necessary to increase the cost of the apparatus due to the probability of occurrence of a jam due to the feeding failure and further addition of a sensor. Thus, an image forming apparatus having high sheet feeding performance and high reliability can be provided.

[Second Embodiment] A second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG.
FIG. 5 is a schematic configuration diagram of the image forming apparatus according to the present embodiment, FIG. 5 is a control block diagram of the image forming apparatus, and FIG. 6 is a flowchart illustrating a feeding operation. Are denoted by the same reference numerals and description thereof will be omitted.

Although the image forming apparatus according to the first embodiment has only one cassette 12, the image forming apparatus according to the present embodiment has a detachable optional cassette 29 as shown in FIG. . A control method in the case of continuously forming an image in the present apparatus will be described.

In FIG. 4, the sheet S stacked on the optional cassette 29 is sent out by one rotation of the pickup roller 30, and is separated by the separation claw 31 and then rotated in the conveying direction. The sheets are separated and fed one by one by the retard roller 33 rotatable in the opposite direction.

FIG. 5 is a block diagram showing a circuit configuration of a control means for controlling the above-mentioned mechanism. In FIG. 5, an optional cassette control unit 34 detects the size of sheets stored in the optional cassette 29 and performs feeding control in accordance with an instruction from the printer engine control unit 24. Upon receiving a request for sheet feeding from the optional cassette 29 from the printer controller 23, the printer engine control unit 24 designates the number of sheets to be fed to the optional cassette control unit 34.

The optional cassette 29 in which the number of sheets to be fed is specified is longer than the length of one sheet conveyed by the feed conveyance path L2 + the sheet distance for achieving the maximum throughput. After the elapse of a predetermined time from the start of feeding, control is performed to start feeding the succeeding sheet.

The feeding operation according to the present embodiment will be described with reference to FIG. In FIG. 6, a printer engine control unit is shown.
24 is an optional cassette control unit via serial communication
The sheet feeding number is instructed to 34 (S20). Upon receiving the instruction, the optional cassette 29 drives the pickup roller 30, the feed roller 32, and the retard roller 33 to feed one sheet loaded on the optional cassette 29. The printer engine control unit 24 detects the leading edge of the sheet by the pre-feed sensor 20 while waiting for a predetermined time (S22) (S22).
twenty one).

[0031] Pre-feed sensor even after a predetermined time has passed
If the sheet 20 cannot detect the leading edge of the sheet (S22), it is determined that the feeding is defective, and an instruction to add the number of fed sheets to the optional cassette control unit 34 is issued (S23). That is, in the instruction to feed n sheets, if the re-feeding operation of the preceding sheet is replaced by the feeding operation of the succeeding sheet, even if the actual number of sheets fed is n, the number of feeding operations is n + This is because it is necessary to perform one sheet.

In this embodiment, an instruction to add the number of fed sheets is given, but an instruction to add the number of feeding operations for operating the pickup roller 30 may be given.

Subsequently, the leading end of the sheet is detected by the pre-feed sensor 20 (S24). If the leading end of the sheet cannot be detected by the pre-feed sensor 20 by the elapse of a predetermined time (S25), it is determined that the feeding is defective (S26). . In the present embodiment, the control in steps S23 to S25 is described as being performed once, but may be performed a plurality of times.

If the pre-feed sensor 20 detects the leading edge of the sheet in steps S21 and S24, it is determined that the feeding operation has been performed normally. Then, it is determined whether or not there is a subsequent sheet (S27). If there is a subsequent sheet, the control is repeated from step S21 again. If there is no succeeding sheet, the feeding operation ends.

As described above, the feeding operation can be performed at a predetermined interval by instructing the number of sheets to be fed to the optional cassette control unit 34, and the same feeding operation can be performed regardless of the presence of the succeeding sheet. A feeding failure can be avoided, and an image forming apparatus having a highly reliable sheet feeding device can be provided.

[0036]

As described above, by performing the control according to the present invention, it is possible to increase the number of images formed per unit time, and further to increase the probability of occurrence of jam due to defective feeding and the cost. Therefore, an image forming apparatus having high feeding performance and high reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

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

FIG. 3 is a flowchart illustrating a feeding operation.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 5 is a control block diagram of the image forming apparatus.

FIG. 6 is a flowchart illustrating a feeding operation.

FIG. 7 is a diagram illustrating a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

 S ... Sheet 1 ... Process cartridge 2 ... Photoconductor drum 3 ... Charge roller 4 ... Developer 5 ... Semiconductor laser 6 ... Scanner motor 7 ... Rotating polygon mirror 8 ... Laser beam 9 ... Transfer roller 10 ... Fixer 11 ... Ejection roller 12 … Cassette (sheet loading means) 13… Pickup roller (sheet feeding means) 14… Supply port 15… Sending roller 16… Separation claw 17… Feed roller 18… Retard roller 19… Transport roller 20… Pre-feed sensor (sheet Detecting means 21 Roller before transfer 22 Top sensor 23 Printer controller (control means) 24 Printer engine control section (control means) 25 Sheet transport control section (control means) 26 High-voltage control section 27 Optical system control Unit 28: Fixing unit control unit 29: Optional cassette (sheet loading means) 30: Pickup roller (sheet feeding means) 31: Hanaretsume 32 ... feed roller 33 ... retard roller 34 ... optional cassette control section (control means)

Claims (4)

[Claims] 1. A sheet stacking means for stacking sheets, a sheet feeding means for feeding sheets one by one from the sheet stacking means, and a sheet detecting means for detecting a sheet fed from the sheet feeding means. A sheet feeding path between a sheet stacking front end portion of the sheet stacking unit and the sheet detecting unit is longer than a sheet feeding direction, and the sheet is fed by the sheet feeding unit. In the image forming apparatus which determines that the feeding is defective if the sheet is not detected by the sheet detecting means within a predetermined time after being fed by the means, during continuous image formation, after feeding out the preceding sheet by the sheet feeding means, Control means for performing control to start feeding of the next sheet before the predetermined time has elapsed, wherein the control means controls the sheet detection operation of the preceding sheet within the predetermined time. If in not detected, the image forming apparatus and performing control to re-feeding operation of the sheet the preceding feeding operation of the next sheet. 2. The control means according to claim 1, wherein, if said preceding sheet is not detected by said sheet detection means within said predetermined time, said control means determines whether said next sheet feeding operation has already been performed. 2. The method according to claim 1, wherein
The image forming apparatus as described in the above. 3. The control unit according to claim 1, wherein the preceding sheet is not detected by the sheet detection unit within the predetermined time, and a feeding operation for the next sheet is started. It is determined whether or not the preceding sheet arrives at the sheet detecting means within the predetermined time within the predetermined time from the feeding operation.If the preceding sheet has not arrived, control for setting the preceding sheet to jam is performed. The image forming apparatus according to claim 1, wherein the image forming is performed. 4. The sheet feeding operation of the next sheet when the preceding sheet is not detected by the sheet detecting means within the predetermined time, and the control means includes a re-feeding operation of the preceding sheet. 3. The image forming apparatus according to claim 1, wherein, when the control is performed, control is performed to add the number of fed sheets or the number of times of feeding operation.