JP2007039203A - Image forming device and re-transporting speed setting program for image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by setting transporting speeds in a circulation path optimum for various sheet sizes. <P>SOLUTION: This image forming device is equipped with an image forming part, the circulation path for circulating a sheet on which an image is formed to the image forming part again, a re-transporting means provided in the circulation path and transporting the sheet on which the image is formed to the image forming part again, a standby part provided in the circulation path in which the image-formed-sheet is made to standby, a sheet size input part for inputting the sheet size, and a control part for controlling the transporting speed of the re-transporting means so that circulation time of the sheet in the inputted sheet size for one round is included in a range from non-stop circulation time when the sheet is not made to standby in the standby part to maximum standby circulation time when the sheet is made to standby in the standby part for the maximum standby possible time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that circulates a sheet on which image formation has been performed again toward an image forming unit, and a re-conveying speed setting program for the image forming apparatus.

  Conventionally, in an image forming apparatus that forms images on both sides of a sheet, the sheet is conveyed to an image forming unit to form an image on one side of the sheet, and then the sheet is returned to the image forming unit via a circulation path. It is configured to carry out image formation on the opposite surface of the sheet.

  In such an image forming apparatus, a so-called alternating circulation method is known in which after the image forming operation on the surface of the sheet, the image forming operation on the back surface of another sheet is alternately performed continuously. In this case, if the sheet conveyance distance of the circulation path is long, an image is formed on the leading edge of the first sheet that is re-conveyed to the image forming unit via the circulation path after the image formation on the surface is completed, and on the surface preceding this sheet. This increases the distance from the trailing edge of the second sheet on which is formed. For this reason, by controlling the sheet conveyance speed in the circulation path to be higher than the sheet conveyance speed in the image forming unit, the distance between sheets in the single-sided image formation and the double-sided image formation is equalized, It is known to prevent a decrease in productivity during image formation (see, for example, Patent Document 1).

It is also known to perform image formation while incorporating a plurality of sheets that can be incorporated in the circulation path in order to improve productivity during double-sided image formation. In this case, the leading edge of the sheet that is re-conveyed to the image forming unit via the circulation path is behind the sheet on which the image is formed on the surface preceding the sheet due to machine difference variation or conveyance speed variation in the circulation path. When a sheet that is re-conveyed to the image forming unit via the circulation path is made to wait to collide with the edge or when the standby time becomes long, the image forming unit passes through the circulation path. Or a subsequent sheet that is re-conveyed. For this reason, it is known to avoid the above-described collision by providing a plurality of standby units in the circulation path and appropriately setting the standby time of the sheets in each standby unit (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 2004-302182 JP 2000-281269 A

  However, the image forming apparatus disclosed in Patent Document 1 is configured assuming that the number of sheets incorporated in the circulation path is one, and does not consider a configuration incorporating a plurality of sheets. Also, application of various sheet sizes is not taken into consideration. Therefore, even if a configuration including a plurality of sheets and various sheet sizes are applied, problems such as sheet collision may occur, and by simply increasing the speed of the circulation path, it may be difficult to form double-sided images. Productivity cannot be improved.

  Further, the image forming apparatus of Patent Document 2 has a configuration in which a plurality of sheets are built in, and various sheet sizes are considered from the viewpoint of sheet collision in the circulation path. In consideration of the improvement viewpoint, the optimum circulation path conveyance speed is not set for each sheet size.

  Therefore, the present invention has been made in view of the above problems, and by setting the optimum circulation path conveyance speed for each sheet size, the production of each sheet size at the time of double-sided image formation, etc. An object of the present invention is to provide an image forming apparatus capable of improving the performance.

  (1) An image forming unit that forms an image on a sheet, a circulation path that circulates the sheet on which image formation has been performed in the image forming unit, toward the image forming unit, and the circulation path. Re-conveying means that conveys the formed sheet again toward the image forming unit, a standby unit that is provided in the circulation path and waits for the sheet on which the image has been formed, and a sheet for inputting a sheet size The maximum waiting time of the sheet in the standby unit from the non-stop circulation time when the circulation time of one round of the sheet of the sheet size input by the size input unit and the sheet size input unit does not wait for the sheet in the standby unit A control unit that controls a re-conveying speed of the re-conveying means so as to be included in a range up to a maximum standby circulation time in the case of waiting. Forming apparatus.

  (2) In the image forming apparatus according to (1), the control unit is configured to calculate a high productivity circulation time for calculating the high productivity circulation time for each sheet size, a first re-conveying speed, and a second Non-stop circulation time calculating means for calculating the non-stop circulation time at each of the re-conveying speeds, and the re-conveying speed at each of the first re-conveying speed and the second re-conveying speed. Maximum standby circulation time calculating means for calculating a maximum standby circulation time, and the high-productivity circulation time is determined by the non-stop circulation time at each of the first re-transfer speed and the second re-transfer speed. To the maximum standby circulation time is determined, and the first re-conveying speed or the first re-transfer speed determined to be included in the range by the determination unit. Having a re-conveying speed setting means for setting a re-conveying speed of said re-conveying means re-conveying speed of, is characterized in that.

  (3) In the image forming apparatus according to (1), the image forming apparatus includes a re-conveying speed storage unit that stores the sheet size and the re-conveying speed of the re-conveying unit in association with each other, and the control unit includes the sheet size. It has a re-conveying speed setting unit that reads out the re-conveying speed corresponding to the sheet size input by the input unit from the re-conveying speed storage unit and sets it as the re-conveying speed of the re-conveying unit.

  (4) In the image forming apparatus according to (2), the re-conveying speed setting unit may determine whether the re-conveying speed setting unit has a plurality of re-conveying speeds determined to be included in the range by the determining unit. The conveyance speed is set as the re-conveying speed of the re-conveying means.

  (5) An image forming unit that forms an image on a sheet, a circulation path that circulates the sheet on which image formation has been performed in the image forming unit, toward the image forming unit, and the circulation path. Re-conveying means that conveys the formed sheet again toward the image forming unit, a standby unit that is provided in the circulation path and waits for the sheet on which the image has been formed, and a sheet for inputting a sheet size A re-feeding speed setting program for an image forming apparatus having a size input unit, wherein the computer is configured to calculate a high-productivity circulation time for calculating a high-productivity circulation time for each sheet size; Non-stop circulation time calculation for calculating a non-stop circulation time when the standby unit does not wait for the sheet at the re-conveying speed of each of the speed and the second re-conveying speed Maximum standby circulation time for calculating a maximum standby circulation time when the standby unit waits for a maximum waiting time at the standby portion at each of the first reconveying speed and the second reconveying speed. The high-productivity circulation time stored in the calculation step and the high-productivity circulation time storage step is the non-stop circulation time at each of the first re-transfer speed and the second re-transfer speed. A determination step for determining whether or not it is included in the range from the maximum standby circulation time to the maximum standby circulation time, and the first re-transfer speed or the second re-transfer speed determined to be included in the range by the determination step And a re-conveying speed setting step of setting as a re-conveying speed of the re-conveying means.

  According to the means of (1) and (5) above, the circulation time of one round of the sheet according to the sheet size, the maximum waiting time of the sheet in the standby unit from the non-stop circulation time when the standby unit does not wait for the sheet Since it can be set so that it is included in the range up to the maximum standby circulation time when making it wait, high productivity at the time of double-sided image formation etc. for each sheet size affects the conveyance of the subsequent sheet or the subsequent sheet Can be ensured without any collision.

  According to the means (2), since the re-conveying speed for ensuring high productivity is calculated in the image forming apparatus, it is possible to cope with a sheet having an arbitrary length such as an irregular size. Is possible.

  According to the above means (3), the optimum re-conveying speed calculated for each sheet size that can be assumed externally is stored in the image forming apparatus in association with the sheet size. There is no need to calculate the re-conveying speed each time in the image forming apparatus.

  According to the above means (4), when satisfying that a high productivity circulation time is included in several transport speeds, a condition with a slow transport speed is selected, so that the collision with the succeeding sheet is further reduced. Can be lowered.

(1) Configuration of Image Forming Apparatus and Flow of Sheet FIG. 1 is a configuration diagram illustrating a main part according to the image forming apparatus of the present embodiment. A toner image is formed on the surface of the photoreceptor 1 by a charging, exposure, and development process (not shown), and the toner image on the surface is transferred to the sheet S by the transfer device 2 (image forming unit). The sheet S is fed from a sheet feeding unit (not shown), and is supplied to the photoreceptor 1 via the loop roller 3, the registration roller 4, and the pre-transfer roller 5.

  The toner image is fixed on the sheet S on which the toner image is transferred by the fixing device 6. The sheet S on which the toner image is fixed is discharged through the fixing discharge roller 7 and the discharge roller 8 and is discharged with the toner image surface down if the sheet S is set to be discharged as it is. If it is set to discharge or form an image on the opposite side, it goes to the circulation path 9 after passing through the fixing discharge roller 7. When the toner image surface is discharged to the outside of the apparatus, the sheet S is conveyed to the reverse discharge roller 11 via the decurler roller 10, and then the reverse discharge roller 11 is reversed to discharge the sheet. The paper is discharged via the roller 12 and the paper discharge roller 8.

  When forming an image on the opposite side of the sheet S, the sheet S is conveyed to the switchback path 14 via the decurler roller 10, the reverse discharge roller 11, and the ADU reverse roller 13, and then the ADU reverse roller 13. Reversely, the first ADU transport roller 15, the second ADU transport roller 16, the third ADU transport roller 17, the fourth ADU transport roller 18, and the ADU registration roller 19 join to the upstream of the registration roller 4, and the transfer unit again It is conveyed toward.

(2) Sheet conveyance control of circulation path FIG. 2 is a control block diagram related to sheet conveyance of the circulation path. Connected to the control unit 20 are a ROM 21 in which various programs and data for executing various arithmetic processes are stored in advance, and a RAM 22 in which various programs and data necessary for executing the various arithmetic processes are temporarily stored. Has been. The control unit 20 reads a program stored in the ROM 21 to the RAM 22 and controls sheet conveyance in accordance with the read program.

  The controller 20 includes a decurler roller 10, a reverse discharge roller 11, an ADU reverse roller 13, a first ADU transport roller 15, a second ADU transport roller 16, a third ADU transport roller 17, and a fourth ADU transport roller provided in the circulation path 9. 18, the transport rollers of the ADU registration roller 19, and the fixing exit sensor 23, the reverse discharge sensor 24, the ADU transport sensor 25, and the ADU exit sensor 26 are connected.

  The control unit 20 is connected to a user interface 27 for performing input such as single-sided / double-sided setting and sheet size setting. The user interface is not limited to the operation panel provided in the image forming apparatus, but may be a personal computer connected to the image forming apparatus.

  The control unit 20 is actually connected with a control target other than the circulation path, but is omitted because it is not directly related to the present invention.

  FIG. 3 is a control flowchart relating to sheet conveyance in the circulation path. Although not shown, as the initial setting, the user interface 27 sets both sides and a desired sheet size, and the sheet S having the sheet size on which image formation on one side is performed is performed at a process speed (for example, 440 mm / mm). It is assumed that it is carried into the circulation path in (sec). The decurler roller 10, the reverse discharge roller 11, and the ADU reverse roller 13 are driven at a process speed, and the first ADU transport roller 15, the second ADU transport roller 16, the third ADU transport roller 17, and the fourth ADU transport roller 18 are Suppose that it is driven at a predetermined conveyance speed (for example, 525 mm / sec). Further, it is assumed that the ADU registration roller 19 is stopped.

  First, when the control unit 20 detects that the trailing edge of the sheet S has passed through the fixing exit sensor 23, the control unit 20 determines the conveyance speed of the decurler roller 10, the reverse discharge roller 11 and the ADU reverse roller 13 from the process speed to the sheet. The conveyance speed determined for each size (for example, 700 mm / sec for A4 and 440 mm / sec for A4R) is set. Accordingly, the sheet S is guided to the switchback path 14 at the set conveyance speed (step S1).

Next, when the reverse discharge sensor 24 detects that the trailing edge of the sheet S has passed through the sensor 20, the control unit 20 reverses the ADU reverse roller 13 and at the same transport speed (525 mm) as the first ADU transport roller 15. / Sec). Accordingly, the sheet S is conveyed toward the first ADU conveyance roller 15 with the trailing edge of the sheet S having passed through the reverse sheet discharge sensor 24 as the head. Further, the conveyance speed of the decurler roller 10 and the reverse discharge roller 11 is returned to the process speed (440 mm / sec) and prepared for conveyance of the subsequent sheet. (Step S2)
Next, when the control unit 20 detects the leading edge of the sheet S by the ADU exit sensor 26, the control unit 20 starts counting of the timer 1. During this time, the stop of the ADU registration roller 19 is maintained. As a result, the sheet S hits the nip of the ADU registration roller 19 whose leading end is stopped, and the skew is corrected (step S3).

  Next, when the timer 1 counts up, the control unit 20 stops the third ADU conveyance roller 17 and the fourth ADU conveyance roller 18. During this time, the sheet S waits in a state where the leading end abuts on the ADU registration roller 19 and the skew is corrected. Thus, the sheet S is prevented from colliding with the trailing edge of the sheet fed from a sheet feeding unit (not shown) and leading to the transfer unit for image formation on the front surface (step S4).

  Next, when 430 mmsec has elapsed since the start of driving of the preceding sheet by the registration roller 4, the control unit 20 moves the third ADU conveyance roller 17, the fourth ADU conveyance roller 18, and the ADU registration roller 19 at a process speed (440 mm / sec). Drive. As a result, the sheet S is conveyed toward the transfer portion for image formation on the back surface (step S5).

  Next, when the control unit 20 detects the trailing edge of the sheet S by the ADU exit sensor 26, the control unit 20 changes the transport speed of the third ADU transport roller 17 and the fourth ADU transport roller 18 from the process speed (440 mm / sec) to the first and second ADUs. While setting to the same conveyance speed (525 mm / sec) as the conveyance rollers 15 and 16, the timer 2 starts counting. As a result, the third ADU conveyance roller 17 and the fourth ADU conveyance roller 18 make preparations for subsequent sheet conveyance (step S6).

  Next, when the timer 2 counts up, the control unit 20 stops the ADU registration roller 19. As a result, the trailing edge of the sheet S passes through the nip portion of the ADU registration roller 19, and then stops to prepare for registration of the subsequent sheet (step S7).

(3) Setting of the conveyance speed of the circulation path for each sheet size Hereinafter, as an example, a case where the sheet size is A4R (length in the conveyance direction of 297 mm) will be described. As a premise, the image forming apparatus of this embodiment has a print speed of 90.6 sheets / minute when the process speed is 440 mm / sec and the sheet size is 8.5 × 11 (the length in the transport direction is 216 mm). (662 msec per sheet, and the distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet is approximately 75.4 mm).

  For A4R sheets, if the distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet is about 75.4 mm, which is an interval of 8.5 × 11 sheets, the number of A4R sheets printed on the single-sided continuous print is 70.9 sheets. / Minute (846 msec per sheet, the distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet is approximately 75.4 mm).

  As for the order of the sheets passing through the transfer portion in the double-sided image formation, if the image formation is performed by the alternating circulation method, the Nth surface and the (N-1) th back surface in the case of the two-sheet circulation. , (N + 1) -th surface, N-th back surface, and so on, until the N-th surface passes and the same N-th back surface circulates and returns again. Another sheet of passes. Then, in order to perform high-productivity image formation in the case where two sheets are circulated, the time from when the front end of the front surface passes through the transfer portion until the front end of the same sheet back circulates and returns is 846 msec × It is necessary to set 3 = 2538 msec.

  In the case of circulation of three sheets, the Nth surface, the (N-2) th back surface, the (N + 1) th surface, the (N-1) th back surface, the (N + 2) th surface, N The other sheet passes through the N-th surface until the same N-th back surface circulates and returns again. Then, in order to perform high-productivity image formation in the case where three sheets are circulated, the time from when the front end of the front surface passes through the transfer portion until the front end of the same sheet back circulates and returns is 846 msec × It is necessary to set 5 = 4230 msec.

  FIG. 4 is a flowchart for determining the conveyance speed of the circulation path for setting the high productivity circulation time. In the present embodiment, the high-productivity circulation time is set by controlling the conveyance speed of the sheet S from when the trailing edge of the sheet S passes through the fixing exit sensor 23 to when it passes through the reverse discharge sensor 24.

  First, when the trailing edge of the sheet S passes through the fixing exit sensor 23 and then passes through the reverse discharge sensor 24, the sheet S is changed in several transport speeds, and the respective circulations when the ADU registration roller 19 does not wait. Calculate time (non-stop circulation time). Here, the non-stop circulation time is calculated when the transport speed is set to 700 mm / sec and 440 mm / sec, for example (step S10).

  In calculating the non-stop circulation time, the following values are stored in the ROM 21 in advance. The path length La (407 mm) from the registration roller 4 to the fixing exit sensor 23, the sheet S conveyance speed Va (= process speed 440 mm / sec) during this period, and the path length Lb (from the fixing exit sensor 23 to the reverse sheet discharge sensor 24) 221 mm) and the sheet S conveyance speed Vb (700 mm / sec or 440 mm / sec), the path length Lc (516 mm) from the reverse discharge sensor 24 to the ADU registration roller 19, and the sheet S conveyance speed Vc (525 mm) / Sec), the path length Ld (138 mm) from the ADU registration roller 19 to the registration roller 4, the sheet conveyance speed Vd (= process speed 440 mm / sec), and the conveyance direction length Ls of the sheet S (297 mm for A4R) , Is stored. Further, the reversing time Tr (90 msec) of the ADU reversing roller 13 and the waiting time Ts (100 msec) of the registration roller 4 are stored.

  The control unit 20 reads each value from the ROM 21 and calculates (La + Ls) / Va + Lb / Vb + Lc / Vc + Ld / Vd + Tr + Ts, so that the non-stop circulation time in each case of Vb = 700 mm / sec and Vb = 440 mm / sec. Is calculated.

  The non-stop circulation time is 3403 msec when Vb = 700 mm / sec, and 3589 msec when Vb = 440 mm / sec.

  Next, in each of the cases of Vb = 700 mm / sec and Vb = 440 mm / sec, the maximum standby circulation time when the sheet S waits for the maximum standby time at the 19 ADU registration rollers is calculated (step S11).

  In calculating the maximum standby circulation time, the maximum standby time is calculated and stored in the RAM 22. Alternatively, a previously calculated value may be stored in the ROM 21 in association with the sheet size. The maximum waiting time is a time determined in consideration of the influence on the conveyance of the succeeding sheet, the collision with the succeeding sheet, and the like, and is set in consideration of a certain margin. In the present embodiment, the maximum waiting time is set so that the leading edge of the subsequent sheet S does not enter the third ADU conveyance roller 17 until the trailing edge of the preceding sheet S passes through the fourth ADU conveyance roller 18.

  In the configuration in which the third ADU conveyance roller 17 and the fourth ADU conveyance roller 18 are drivingly connected, the third ADU conveyance roller 17 is also the fourth ADU until the trailing edge of the preceding sheet S passes through the fourth ADU conveyance roller 18. It is driven at a process speed of 440 mm / sec together with the conveying roller 18, and if the leading edge of the succeeding sheet S enters the third ADU conveying roller 17 during this time, the rear of the succeeding sheet S is 525 mm / sec by the second ADU conveying roller 16. This is because the sheet is conveyed in sec, and the sheet is bent between the second ADU conveyance roller 16 and the third ADU conveyance roller 17, and troubles such as jamming occur.

  The control unit 20 reads the maximum waiting time from the RAM 22 and adds the maximum waiting time to the non-stop circulation time to calculate the maximum waiting circulation time for the sheet S.

  For example, if the maximum standby time is set to 792 msec, the maximum standby circulation time is 4195 msec (3403 msec + 792 msec) when Vb = 700 mm / sec, and 4381 msec (3589 msec + 792 msec) when Vb = 440 mm / sec. Become.

  Next, in each case of Vb = 700 mm / sec and Vb = 440 mm / sec, within the range from the calculated non-stop circulation time to the maximum standby circulation time, the high productivity circulation time (2538 msec: two-sheet circulation, It is determined whether or not 4230 msec: three-sheet circulation is included (step S12).

  In determining whether the high productivity circulation time is included in the range from the non-stop circulation time to the maximum standby circulation time, the high productivity circulation time (846 msec × 3 = 2538 msec: 2 sheets circulation, 846 msec × 5 = 4230 msec: 3 circulations) is calculated and stored in the RAM 22. Alternatively, a previously calculated value may be stored in the ROM 21 in association with the sheet size.

The control unit 20 reads the high productivity circulation time from the RAM 22 and, in each case of Vb = 700 mm / sec and Vb = 440 mm / sec, within the range from the calculated non-stop circulation time to the maximum standby circulation time, It is determined whether high productivity circulation time (2538 msec: 2 sheets circulation, 4230 msec: 3 sheets circulation) is included or not. When Vb = 700 mm / sec, 3403 msec (non-stop circulation time) to 4195 msec (maximum standby circulation time) It is determined whether 2538 msec or 4230 msec is included in the range up to. In this case, it is determined that both values are not included in the above range. This means the following. Since the high productivity circulation time (4230 msec) during the circulation of three sheets is longer than the maximum standby circulation time (4195 msec), the three sheets cannot be circulated because of the possibility of collision of subsequent sheets. For this reason, although the two sheets are circulated, the high productivity circulation time (2538 msec) when the two sheets are circulated is also greatly deviated from the above range. Can not.

  On the other hand, when Vb = 440 mm / sec, it is determined whether 2538 msec or 4230 msec is included in the range from 3589 msec (non-stop circulation time) to 4381 msec (maximum standby circulation time). In this case, it is determined that the value of 4230 msec of circulation of 3 sheets is included in the above range. This means the following. Assuming that the waiting time at the 19th ADU registration roller is 641 msec, it is possible to circulate at 4230 msec, which is a high productivity circulation time when three sheets are circulated, and it may affect the conveyance of subsequent sheets. There is no collision with subsequent sheets.

  Next, Vb = 440 mm / sec including the high productivity circulation time is set as the conveyance speed (step S13).

  The control unit 20 sets the conveyance speed of the decurler roller 10, the reverse discharge roller 11, and the ADU reverse roller 13 after the trailing edge of the sheet S passes through the sensor by the fixing exit sensor 23 to 440 mm / sec. Further, the control unit 20 starts driving the ADU registration roller 19 430 msec after starting the driving of the registration roller 4 with respect to a sheet on which an image is formed on the preceding front surface fed from the paper feeding unit. As a result, the waiting time at the 19th ADU registration roller is 641 msec, and the high productivity circulation time of 4230 msec is achieved.

  As described above, the circulation time of one round of the sheet according to the sheet size is from the non-stop circulation time when the standby unit does not wait for the sheet to the maximum standby circulation time when the standby unit waits for the maximum standby time. Because it can be set to be included in the range, it ensures high productivity when forming double-sided images for each sheet size without affecting the conveyance of subsequent sheets or causing collisions with subsequent sheets. can do.

  In the present embodiment, the conveyance speed Vb is changed in two stages, but it may be changed in more stages. In this embodiment, the high productivity circulation time is included only at the conveyance speed Vb of 440 mm / sec. However, the high productivity circulation time is included at several conveyance speeds Vb. In this case, it is preferable to select a condition with a low conveyance speed from the viewpoint of lowering the collision with the subsequent sheet.

  In the present embodiment, the conveyance speed of the sheet S from when the trailing edge of the sheet S passes through the fixing outlet sensor 23 to when it passes through the reverse sheet discharge sensor 24 is controlled so as to adjust to a high productivity circulation time. However, the conveyance speed at other points in the circulation path 9 may be controlled so as to be adjusted so as to reach a high productivity circulation time.

  In this embodiment, the sheet conveyance control by the alternating circulation method is applied. However, after the front image formation is continuously performed for a plurality of sheets, the continuous image formation of the back surface is continuously performed for the plurality of sheets. It is also applicable to sheet conveyance control.

  In the present embodiment, a sheet having a sheet size of A4R is taken up. However, the optimum conveying speed of the circulation path can be set in the same manner for sheets having other sheet sizes.

  In this embodiment, the conveyance direction length Ls of the sheet S is stored in the ROM 21 in advance. However, when an irregular-size sheet is used, the user interface 27 causes the conveyance direction length Ls of the sheet S to be used. May be input, and the input value may be used. In this case, it is possible to cope with a sheet having an arbitrary length.

  In this embodiment, the control unit 20 of the image forming apparatus calculates the optimal circulation path conveyance speed. However, in the case of a standard size, the sheet size calculated externally in advance and the optimum circulation path for the sheet size are calculated. You may make it memorize | store the table which showed the relationship with a conveyance speed in ROM21. In this case, it is not necessary to calculate the conveyance speed each time in the image forming apparatus.

  In the present embodiment, the present invention is applied to the case where the front and back of the sheet S are reversed in the circulation path 9 and images are formed on both sides of the sheet S. The present invention can also be applied when a composite image is formed on one side of S.

  In this embodiment, an electrophotographic image forming apparatus has been described. However, the present invention can also be applied to an image forming apparatus such as an inkjet recording system.

1 is a configuration diagram illustrating a main part of an image forming apparatus according to an exemplary embodiment. FIG. 6 is a control block diagram related to sheet conveyance in a circulation path. FIG. 6 is a control flow diagram related to sheet conveyance in a circulation path. It is a flowchart for determining the conveyance speed of the circulation path | route for setting to high productivity circulation time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Transfer device 9 Circulation path | route 10 Decurler roller 11 Reverse discharge roller 13 ADU reverse roller 15 1st ADU conveyance roller 16 2nd ADU conveyance roller 17 3rd ADU conveyance roller 18 4th ADU conveyance roller 19 ADU registration roller 20 Control part 21 ROM
22 RAM
23 Fixing Exit Sensor 24 Reverse Paper Discharge Sensor 25 ADU Conveyance Sensor 26 ADU Exit Sensor 27 User Interface

Claims (5)

An image forming unit for forming an image on a sheet;
A circulation path for circulating the sheet on which image formation has been performed in the image forming unit again toward the image forming unit;
A re-conveying means that is provided in the circulation path and conveys the sheet on which the image has been formed toward the image forming unit again;
A standby unit that is provided in the circulation path and waits for the sheet on which the image has been formed;
A sheet size input section for inputting the sheet size;
The maximum circulation time of the sheet of the sheet size input by the sheet size input unit when the standby unit waits for the maximum waiting time from the non-stop circulation time when the standby unit does not wait for the sheet. A control unit for controlling the re-conveying speed of the re-conveying means so as to be included in the range up to the standby circulation time;
An image forming apparatus comprising: The controller is
High productivity circulation time calculating means for calculating high productivity circulation time for each sheet size;
Non-stop circulation time calculating means for calculating the non-stop circulation time at each of the first and second re-transfer speeds;
Maximum standby circulation time calculating means for calculating the maximum standby circulation time at each of the first re-transport speed and the second re-transport speed;
Whether or not the high productivity circulation time is included in a range from the non-stop circulation time to the maximum standby circulation time at each of the first and second re-conveying speeds. A judging means for judging
Re-conveying speed setting means for setting the first re-conveying speed or the second re-conveying speed determined to be included in the range by the determining means as the re-conveying speed of the re-conveying means;
Having
The image forming apparatus according to claim 1. A re-conveying speed storage means for storing the sheet size and the re-conveying speed of the re-conveying means in association with each other;
The controller is
A re-conveying speed setting unit that reads out a re-conveying speed corresponding to the sheet size input by the sheet size input unit from the re-conveying speed storage unit and sets the re-conveying speed of the re-conveying unit;
The image forming apparatus according to claim 1. The re-conveying speed setting means sets the slower re-conveying speed as the re-conveying speed of the re-conveying means when there are a plurality of re-conveying speeds determined to be included in the range by the determining means. The image forming apparatus according to claim 2. An image forming unit for forming an image on a sheet;
A circulation path for circulating the sheet on which image formation has been performed in the image forming unit again toward the image forming unit;
A re-conveying means that is provided in the circulation path and conveys the sheet on which the image has been formed toward the image forming unit again;
A standby unit that is provided in the circulation path and waits for the sheet on which the image has been formed;
A sheet size input section for inputting the sheet size;
A re-conveying speed setting program for an image forming apparatus having
On the computer,
A high productivity circulation time calculating step for calculating a high productivity circulation time for each sheet size;
A non-stop circulation time calculating step for calculating a non-stop circulation time when the standby unit does not wait for the sheet at the respective re-conveying speeds of the first re-conveying speed and the second re-conveying speed;
A maximum standby circulation time calculating step for calculating a maximum standby circulation time when the standby unit waits for a maximum waiting time at the standby unit at each of the first reconveying speed and the second reconveying speed; ,
The high productivity circulation time stored in the high productivity circulation time storage step is the maximum waiting time from the non-stop circulation time at each of the first reconveying speed and the second reconveying speed. A determination step for determining whether or not it is included in the range up to the circulation time;
A re-conveying speed setting step for setting the first re-conveying speed or the second re-conveying speed determined to be included in the range by the determining step as a re-conveying speed of the re-conveying means;
And a re-conveying speed setting program for the image forming apparatus.

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