JP2006248676A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of conveying sheets without troubles even in the case wherein a rear end of a sheet is pinched by a separating roller when conveying the sheets for transfer processing after aligning them. <P>SOLUTION: This image forming device has a drive control unit 101 for controlling drive of a conveying roller arranged in the conveying direction upstream of an intermediate conveying roller for conveying the sheets to a resist roller for correcting bias feeding of the conveyed sheets, and provided with a timing determination unit 102 for determining timing to start conveyance of the sheets, of which bias feeding is corrected by the resist roller, after correcting bias feeding of the sheets with the resist roller. The drive control unit 101 drives the conveying roller for the predetermined time in the predetermined timing when the timing determination unit 102 determines that the resist roller is in the predetermined timing to start conveyance of the sheet, of which bias feeding is corrected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a digital copying machine or a printer.

  In a conventional image forming apparatus, one-sided control that prints only on the front side of the printing paper and does not print on the back side but discharges it as it is, and prints only on the front side of the printing paper and does not print on the back side, but the front and back are reversed Another one-sided printing control that discharges pages in order, and after the printing on the front side is completed, the paper is not discharged and passed through the automatic duplex unit (ADU), then re-feeded, printed on the back side, and discharged. Double-sided printing control is performed.

In order to satisfy the various conditions associated with the control as described above, the following three speeds related to the conveyance of the printing paper are set according to the necessity of each process. That is,
(1) Paper feed speed = speed for transporting printing paper from the paper feed cassette to the registration roller during paper feed;
(2) Process speed = speed for performing printing (printing by transfer) using, for example, a photosensitive drum,
(3) ADU speed = refeed speed from ADU.

  In a conventional image forming apparatus, in order to ideally set the above-mentioned speed so as to match the conditions of each printing process, for example, all the rollers that carry the printing paper together are driven at a multistage speed. If it is possible to use a plurality of clutches or a pulse motor so that the speed can be freely changed, it is not impossible, but there is a problem that a great cost is required. Therefore, as shown in FIG. 6, a pulse motor-driven intermediate conveyance roller 112 (basically, a sheet conveyance port 150 and an ADU 170 of the image forming apparatus, and a registration roller 111 and a sheet discharge port. The printing paper is conveyed by the three-speed control in accordance with the above three speeds.

  In the conventional example shown in FIG. 6, the printing paper stored in the paper feed cassettes 161, 162,... Is picked up by the pick-up rollers 141c, 142c, and the paper feed rollers 141a, 142a,. The separation rollers 141b, 142b,... Are sent one by one to the paper conveyance path 150. The printing paper sent out to the paper conveyance path 150 is conveyed at a paper feed speed (in this example, 420 mm / sec) by the first, second, and second conveyance rollers 151, 152,. , And reaches the registration roller 111 (420 mm / sec).

  When the printing paper reaches the registration roller 111, it is subjected to aligning control, and then is processed into a transfer nip between the photosensitive drum 110 and the transfer belt 120 by the registration roller 111 and the intermediate conveyance roller 112. The toner image is fed at a speed (340 mm / sec), the toner image is transferred to the surface, and sent to the fixing device to fix the toner image. In the case of double-sided printing, the printing paper whose surface printing and fixing has been completed is reversed by the ADU 170, and is reprinted at the ADU refeed speed (385 mm / sec) toward the registration roller 111 via the intermediate conveyance roller 112. The paper is fed, and a toner image is printed and fixed on the back surface and discharged. The three-speed control is shown in the speed diagram of FIG.

  However, in the image forming apparatus described above, when the size of the printing paper conveyed from the paper feeding cassette toward the transfer nip is large (A3, LD), for example, as shown in FIG. 6, the printing paper aligning control is completed. At this time, a state occurs in which the trailing edge of the printing paper is not completely removed from the paper feed / separation roller (in FIG. 6, the length DS is not completely removed by the paper feed roller 142a / separation roller 142b). In such a case, even if the clutches 151c and 152c (see FIG. 7) of the first and second transport rollers 151 and 152 are in the “off” state, they are sandwiched between the paper feed roller 142a and the separation roller 142b. The load (torque load is 0.45 to 0.5 mNm) is large, and there is a risk of causing step-out of a pulse motor or the like that drives the intermediate conveyance roller.

  The present invention has been made to solve the above-described problems. Even when the printing paper used for printing is large in size and the printing paper aligning control is finished, the trailing edge of the printing paper is When resuming the conveyance of printing paper by the intermediate conveyance roller and registration roller in a state where the paper is not completely caught between the paper feeding / separation rollers, the load on the trailing edge of the printing paper is reduced. An object of the present invention is to provide an economical image forming apparatus capable of transporting printing paper satisfactorily.

  In order to solve the above-described problem, the image forming apparatus according to the present invention is a conveyance device disposed upstream of the intermediate conveyance roller that conveys the sheet with respect to the registration roller that performs skew correction of the conveyed sheet. A drive control unit that performs drive control of the roller; and a timing determination unit that determines a timing at which the registration roller starts conveyance of the skew-corrected sheet after the skew correction in the registration roller. The control unit drives the conveyance roller for a predetermined time from the predetermined timing when the timing determination unit determines that the registration roller is at a predetermined timing to start conveying the skew-corrected sheet. It is the composition which makes it.

  As described in detail above, according to the present invention, even if the trailing edge of the printing paper is sandwiched between the paper feeding roller and the separation roller when the printing paper conveyance by the registration roller is resumed, The roller removes this load, and the sheet conveyance of the intermediate conveyance roller or the like can be improved. Therefore, the intermediate transport roller can be driven with a small pulse motor, which is economical.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall configuration of the image forming apparatus according to the present embodiment.
An image forming apparatus 100 in FIG. 1 includes a toner image forming unit including a photosensitive drum 10, a transfer belt 20 that transfers a toner image formed on the photosensitive drum 10 onto a printing paper (sheet), and a toner image. A fixing device 30 that fixes the toner image on the printing paper that is transferred and carried by the transfer belt 20 to the printing paper, a control unit (composed of a CPU or the like) 104 that performs various processes in the image forming device 100, a ROM And a memory 105 that stores various data and programs used in the apparatus.

  Furthermore, the image forming apparatus 100 includes a plurality of paper feed cassettes that hold print paper of each size, a paper feed mechanism that pulls out the print paper from the paper feed cassettes and sequentially feeds the paper to the paper transport path 50 one by one. The printing paper delivered from the paper feeding mechanism is conveyed to the aligning position via the paper conveying path 50 at the paper feeding speed (420 mm / sec in this example), and after the aligning control, the photosensitive drum 10 is further fed. And a transfer mechanism that feeds printing paper at a process speed (340 mm / sec in this example) toward the transfer nip between the printing belt 20 and the transfer belt 20, and reverses the printed paper that has already been printed on one side, Automatic double-sided device that cooperates and refeeds at the ADU speed (refeed speed; in this example, 385 mm / sec) toward the aligning position 0 (for example, ADU70 of stack-less) and a.

  The above-described sheet feeding mechanism includes sheet feeding cassettes 61, 62, 63, 64, pickup rollers 41c, 42c, 43c, 44c, sheet feeding rollers 41a, 42a, 43a, 44a, and separation rollers 41b, 42b, 43b, 44b, and the sheet transport mechanism includes first, second, third, and fourth transport rollers 51, 52, 53, and 54, an intermediate transport roller 12, and a registration roller 11. In this case, the intermediate transport roller 12 uses a pulse motor as a drive source, and the CPU (control unit) 104 can control the drive of the intermediate transport roller 12 at at least three speeds.

  The first, second, third, and fourth transport rollers 51, 52, 53, and 54 are driven by a low-cost ordinary motor (for example, a servo motor) through a clutch to reduce the cost. . In the case of duplex printing control or the like, the automatic duplexer 70 cooperates with the intermediate conveyance roller 12 for printing paper with the front and back reversed, which is sent via the routes 32, 33 and 71, at the ADU speed. Re-feed toward 11. Accordingly, the intermediate transport roller 12 is controlled so as to be able to operate at three speeds of the paper feed speed, the process speed, and the ADU speed corresponding to each process.

  FIG. 2 is a functional block diagram of the image forming apparatus according to the present embodiment. The image forming apparatus according to the present embodiment includes a drive control unit 101, a timing determination unit 102, and a sheet size determination unit 103.

  The drive control unit 101 has a role of performing drive control of a conveyance roller disposed upstream of the intermediate conveyance roller 12 that conveys the sheet with respect to the registration roller 11 that performs skew correction of the conveyed sheet. is doing. Here, the conveyance rollers disposed on the upstream side in the conveyance direction with respect to the intermediate conveyance roller 12 include, for example, conveyance rollers 51 to 54, paper feed rollers 41a to 44a, separation rollers 41b to 44b, pickup rollers 41c to 44c, and the like. Then, drive control of at least one of these rollers is performed.

  The timing determination unit 102 has a role of determining a timing at which the registration roller 11 starts conveying a sheet whose skew has been corrected after the skew correction in the registration roller 11.

  The sheet size determination unit 103 has a role of determining the size in the sheet conveyance direction of a sheet to be subjected to skew correction in the registration roller 11. Information relating to the size of the sheet in the sheet conveyance direction can be acquired from the paper feed cassette that supplied the sheet, the paper setting information in the information of the image formed on the sheet, and the like.

  In addition, when the sheet size determination unit determines that the sheet that is the target of skew correction in the registration roller 11 is larger than a predetermined size, the drive control unit 101 corrects the skew of the registration roller 11 by the timing determination unit. When it is determined that it is a predetermined timing for starting the conveyance of the conveyed sheet, the conveyance roller is driven for a predetermined time from the predetermined timing. Here, the conveying rollers correspond to the conveying rollers 51 to 54, the paper feeding rollers 41a to 44a, the separation rollers 41b to 44b, the pickup rollers 41c to 44c, and the like, as described above, and at least one of these rollers. Means.

  Next, an overall processing flow in the sheet conveying method according to the present embodiment will be described. FIG. 3 is a flowchart for explaining processing in the sheet conveying method according to the present embodiment.

  The drive control unit 101 performs drive control of a conveyance roller disposed upstream of the intermediate conveyance roller 12 that conveys the sheet with respect to the registration roller 11 that performs skew correction of the conveyed sheet (drive control). Step) (S801).

  The sheet size determination unit 103 determines the size in the sheet conveyance direction of the sheet to be skew-corrected in the registration roller 11 (sheet size determination step) (S802).

  The timing determination unit 102 determines the timing at which the registration roller 11 starts to convey the skew-corrected sheet after the skew correction in the registration roller 11 (timing determination step) (S803). Here, data regarding a timing chart that defines the timing of sheet conveyance as described above is stored in the MEMORY 105.

  When it is determined in the sheet size determination step that the sheet that is the target of skew correction in the registration roller 11 is larger than the predetermined size, the drive control unit 101 corrects the skew in the registration roller 11 in the timing determination step. When it is determined that the predetermined timing for starting the conveyance of the sheet is reached, the conveyance roller is driven for a predetermined time from the predetermined timing (drive control step) (S804).

  The sheet larger than the predetermined size here means, for example, an A3 size sheet. In addition, the predetermined time here is a state where the trailing edge of the sheet that has been skew-corrected at a predetermined timing is sandwiched by a separation roller that supplies the sheet to the sheet conveyance path. It means the time required for the end to come out from the state of being pinched by the separation roller from a predetermined timing.

  Here, the timing determination step (S803) is performed after the sheet size determination step (S802). However, the present invention is not limited to this. The sheet size determination step is performed after the timing determination step, or both steps are performed simultaneously. You can also do it.

  Note that the processing of each step (S801 to S804) in the above-described sheet conveying method is realized by causing the CPU 104 to execute a sheet conveying program stored in the MEMORY 105.

4 is a cross-sectional view illustrating a state during alignment control of a large print sheet in the image forming apparatus of FIG. 1, and FIG. 5 is a timing chart for explaining the operation of the image forming apparatus of FIG.
In the image forming apparatus 100 configured as described above, when the problem as shown in FIG. 6 occurs, how this problem is solved by the control of the control unit of the image forming apparatus 100. Will be described with reference to FIGS. 1, 4 and 5. FIG. At time t1 shown in FIG. 5, the paper feed motor that drives the transport rollers 51 to 54 starts operating, and the clutches 51c and 52c (see FIG. 5) of the first and second transport rollers 51 and 52 are “on”. Thus, the first and second transport rollers 51 and 52 transport the paper at the paper feed speed. At time t6, the intermediate conveyance SW is also turned on, and the first and second conveyance rollers 51 and 52 cooperate with the intermediate conveyance roller 12 to print paper (large size) from time t6 to time t9. Transport to the aligning position (pre-registration SW “ON”; time t8). The intermediate conveyance SW is a sensor for determining whether or not the leading edge of the sheet has passed through the intermediate conveyance roller 12. The pre-registration SW is a sensor for detecting that the sheet has reached just before the registration roller 11. It is.

  From time t8 to t9, aligning control is performed. This aligning control ends, and the clutches 51c and 52c are turned off at time t9. At time t <b> 10, the printing paper whose alignment has been controlled by the registration roller 11 and the intermediate conveyance roller 12 is sent to the transfer nip between the photosensitive drum 10 and the transfer belt 20 at a process speed. The clutches 51c and 52c of the first and second transport rollers 51 and 52 are turned on during the time t10 to t11 when the feeding starts, and the feed roller 42a and the separation roller 42b are turned on as shown in FIG. A force is applied in the direction of pulling out the trailing edge of the printing paper sandwiched between them, and the paper feeding by the registration roller 11 and the intermediate transportation roller 12 is controlled to be pushed.

In the above case, as shown in FIG. 4, the length DS that is sandwiched between the paper feed roller 42a and the separation roller 42b and does not come out is about 15 mm for A3 size printing paper and about 27 mm for LD size printing paper. is there. The minimum time (corresponding to a predetermined time) necessary for this distance to come out between the paper feed roller 42a and the separation roller 42b is as follows:
In the case of A3 paper, 15 mm / 420 (mm / sec) = 35.7 msec, which is about 55 mmsec considering the delay of clutch engagement.
In the case of LD paper, 27 mm / 420 (mm / sec) = 64.2 msec, which is about 85 mmsec in consideration of a delay in clutch connection.
Therefore, the time for the back-up control must be determined according to the position of the paper feed cassette in which the printing paper is stored and the size of the printing paper. The determined content may be stored in the MEMORY 105 and used by the control unit for boost control.

  As is apparent from the above description, during the time t10 to t11, the first and second transport rollers 51 and 52 feed the process speed printing paper transported by the registration roller 11 and the intermediate transport roller 12. By performing the back-up control at the speed, the load caused by the sandwiching between the paper feed roller 42a and the separation roller 42b is removed from the registration roller 11 and the intermediate conveyance roller 12, thereby preventing the motor from stepping out. Accordingly, the pulse motor that is the drive source of the intermediate conveyance roller 12 may be small, and as a result, the cost of the image forming apparatus 100 can be reduced. Even after the trailing edge of the printing paper comes out between the paper feed roller 42a and the separation roller 42b, the conveyance of the printing paper at the process speed by the registration roller 11 and the intermediate conveyance roller 12 continues until time t14. The printing on the printing paper is finished.

  At time t15, the conveyance of the next printing paper sent out from the paper feed cassette 62 is started. The press-up control of the printing paper is performed from time t20 to t21. In addition, from time t23 to t29, re-feeding from the ADU 70 is performed, and aligning control is performed from time t28 to t29. In this example, the refeeding from the ADU 70 is not carried out, but is conveyed and printed at the process speed from time t31 to t35. From time t36 to t39, the sheet is conveyed from the third sheet cassette 62 at the sheet feeding speed, and the back-up control is performed from time t40 to t41. Here, the times t10, t20, and t40 correspond to predetermined timings when the registration roller 11 starts to convey the skew-corrected sheet.

  As described above, in this image forming apparatus 100, a pulse motor drive is provided between the discharge port of the paper conveyance path 50 from the paper feed cassette, the discharge port of the ADU 70 that joins the discharge port, and the registration roller 11. By arranging the intermediate conveyance roller 12, three-speed control that can correspond to three speeds of paper feeding speed, process speed, and ADU speed is enabled. In the embodiment of the present invention, the printing paper conveyed from the paper feed cassette is used for transfer, as clearly shown in FIG. 5 and FIG. In the case where the sheet is conveyed at the process speed, the boost control is executed in a short period of time when the sheet conveyance is started.

  In the image forming apparatus 100 as described above, the load on the paper feeding roller and the separation roller, which is generated when a large size printing paper is supplied from the paper feeding cassette, can be removed by a short drive of the transport roller. The need to increase the pulse motor that drives the transport roller 12 is eliminated. For the same reason, a motor other than the pulse motor that drives the intermediate conveyance roller 12 may be an ordinary motor. Therefore, the image forming apparatus 100 can be manufactured economically at a reduced cost.

  In this embodiment, the function for implementing the invention is recorded in advance in the apparatus. However, the present invention is not limited to this, and the same function may be downloaded from the network to the apparatus, and the same function is recorded. What is stored in the medium may be installed in the apparatus. The recording medium may be any form as long as the recording medium can store the program and can be read by the apparatus, such as a CD-ROM. Further, the function obtained by installing or downloading in advance may be realized in cooperation with an OS (operating system) or the like inside the apparatus.

  Although the present invention has been described in detail according to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

1 is a cross-sectional view showing an embodiment of an image forming apparatus of the present invention. 2 is a functional block diagram of the image forming apparatus according to the present embodiment. FIG. 6 is a flowchart for explaining processing in a sheet conveying method according to the present embodiment. FIG. 2 is a cross-sectional view illustrating a state during alignment control of a large print sheet in the image forming apparatus of FIG. 1. 3 is a timing chart for explaining the operation of the image forming apparatus in FIG. 1. FIG. 10 is a cross-sectional view for explaining a problem that occurs in a conventional image forming apparatus. 7 is a timing chart showing the operation of the image forming apparatus in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum, 11 Registration roller, 12 Intermediate conveyance roller, 20 Transfer belt, 30 Fixing device, 31 Printed paper discharge port, 32, 33, 71 Refeed paper conveyance path, 41a, 42a, 43a, 44a Roller, 41b, 42b, 43b, 44b Separation roller, 41c, 42c, 43c, 44c Pickup roller, 50 Paper transport path, 51 First transport roller, 52 Second transport roller, 53 Third transport roller, 54 4 transport rollers, 61, 62, 63, 64 paper feed cassette, 70 automatic duplexer (ADU), 100 image forming apparatus.

Claims (5)

A drive control unit that performs drive control of a conveyance roller disposed upstream of the intermediate conveyance roller that conveys the sheet with respect to the registration roller that performs skew correction of the conveyed sheet;
A timing determination unit that determines the timing at which the registration roller starts conveying the skew-corrected sheet after the skew correction in the registration roller;
The drive control unit moves the conveyance roller from the predetermined timing to a predetermined time when the timing determination unit determines that the registration roller is at a predetermined timing to start conveying the skew-corrected sheet. An image forming apparatus that only drives. A drive control unit that performs drive control of a conveyance roller disposed upstream of the intermediate conveyance roller that conveys the sheet with respect to the registration roller that performs skew correction of the conveyed sheet;
A sheet size determination unit that determines a size in a sheet conveyance direction of a sheet to be subjected to skew correction in the registration roller;
A timing determination unit that determines the timing at which the registration roller starts conveying the skew-corrected sheet after the skew correction in the registration roller;
When the sheet size determination unit determines that the sheet that is the target of skew correction in the registration roller is larger than a predetermined size, the drive control unit causes the timing determination unit to move the registration roller to the skew. An image forming apparatus that drives the conveying roller for a predetermined time from the predetermined timing when it is determined that the predetermined timing for starting the conveyance of the corrected sheet is reached. The image forming apparatus according to claim 1, wherein:
The predetermined time is a state in which the trailing end of the sheet whose skew has been corrected at the predetermined timing is sandwiched by a separation roller that supplies the sheet to the sheet conveyance path. An image forming apparatus, which is a time required from a predetermined timing to exit from a state of being sandwiched between the separation rollers. A drive control step for performing drive control of a transport roller disposed upstream of the intermediate transport roller for transporting the sheet to a registration roller that performs skew correction of the transported sheet;
A timing determination step of determining a timing at which the registration roller starts conveying the skew-corrected sheet after the skew correction in the registration roller;
In the driving control step, when the timing determination step determines that the registration roller is at a predetermined timing to start conveying the skew-corrected sheet, the driving roller is moved from the predetermined timing to a predetermined time. Only the sheet conveying method to drive. A drive control step for performing drive control of a transport roller disposed upstream of the intermediate transport roller for transporting the sheet to a registration roller that performs skew correction of the transported sheet;
A sheet size determination step for determining a size in a sheet conveyance direction of a sheet to be skew-corrected in the registration roller;
A timing determination step of determining a timing at which the registration roller starts conveying the skew-corrected sheet after the skew correction in the registration roller;
In the drive control step, when it is determined in the sheet size determination step that the sheet that is the target of skew correction in the registration roller is larger than a predetermined size, the timing determination step causes the registration roller to move the skew. A sheet conveying method of driving the conveying roller for a predetermined time from the predetermined timing when it is determined that the predetermined timing for starting conveyance of the corrected sheet is reached.

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