Image forming apparatus and drive control method

Abstract

To provide an image forming apparatus and a drive control method capable of shortening the interval between paper feeding operations performed by a paper feed unit.SOLUTION: An image forming apparatus 100 includes a second paper feed unit 42, including rollers 42A, 42B, for feeding sheets from a second paper feed position P22 at a predetermined feed cycle, a sheet sensor 42C for detecting sheets conveyed by the roller 42A, and a drive control unit for driving a stepping motor used to drive rollers 42A, 42B, such that on the basis of the timing of sheet detection by the sheet sensor 42C, the sheet reaches the second paper feed position P22 when the next feed timing by the second paper feed unit 42 arrives.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a drive control method. [Background technology]

[0002] The electrophotographic image forming apparatus includes a transfer unit and a paper feed unit. The transfer unit transfers a toner image onto a sheet. The paper feed unit includes a transport member that transports the sheet upstream of a transfer position in a sheet transport direction along a transport path of the sheet that passes through a transfer position of the toner image by the transfer unit, and feeds the sheet from a paper feed position downstream of the transport member in the transport path in the transport direction at a predetermined paper feed cycle.

[0003] Also, an image forming apparatus including a stepping motor that drives the conveying member is known as related art (see Patent Document 1). In the image forming apparatus according to this related art, the driving of the stepping motor is stopped from the timing when the sheet reaches the paper feed position until the next paper feed timing by the paper feed unit arrives. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-215869 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the stepping motor may vibrate for a while after it has stopped. If the stepping motor is started again while it is vibrating, the behavior of the stepping motor becomes unstable.

[0006] In the image forming apparatus according to the related art described above, in order to prevent the behavior of the stepping motor from becoming unstable, it is necessary to set the paper feed cycle so that the next paper feed timing occurs after the vibrations caused by the stepping motor have subsided after stopping. In other words, in the image forming apparatus according to the related art described above, the shortening of the interval between paper feed operations by the paper feed unit is limited.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a drive control method that can shorten the interval between paper feeding operations by a paper feeding unit. [Means for solving the problem]

[0008] According to one aspect of the present invention, an image forming apparatus includes a transfer unit, a paper feed unit, a stepping motor, a detection processing unit, and a drive control unit. The transfer unit transfers a toner image onto a sheet. The paper feed unit includes a transport member that transports the sheet upstream of a transfer position on a transport path of the sheet that passes through a transfer position of the toner image by the transfer unit, in a sheet transport direction, and feeds the sheet from a paper feed position on the transport path that is downstream of the transport member in the transport direction, at a predetermined paper feed cycle. The stepping motor drives the transport member. The detection processing unit detects the sheet transported by the transport member upstream of the paper feed position on the transport path in the transport direction. The drive control unit drives the stepping motor based on the detection timing of the sheet by the detection processing unit so that the sheet reaches the paper feed position when the next paper feed timing by the paper feed unit arrives.

[0009] According to another aspect of the present invention, there is provided a drive control method for an image forming apparatus including a transfer unit that transfers a toner image onto a sheet, a transport member that transports the sheet upstream of the transfer position in a sheet transport path that passes through a transfer position of the toner image by the transfer unit, and a paper feed unit that feeds the sheet at a predetermined paper feed period from a paper feed position downstream of the transport member in the transport path, and a stepping motor that drives the transport member. The drive control method includes a detection step and a drive control step. In the detection step, the sheet transported by the transport member upstream of the paper feed position in the transport path in the transport direction is detected. In the drive control step, the stepping motor is driven based on the detection timing of the sheet in the detection step so that the sheet reaches the paper feed position when the next paper feed timing by the paper feed unit arrives. [Effects of the Invention]

[0010] According to the present invention, it is possible to shorten the interval between paper feeding operations by the paper feeding unit. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing an example of a first paper feed control process executed by the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing an example of the second paper feed control process executed in the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0013] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view showing the configuration of the image forming apparatus 100.

[0014] The image forming apparatus 100 is a printer that forms an image on a sheet by electrophotography. The present invention can be applied to fax machines, copy machines, multifunction machines, and the like that form images on a sheet by electrophotography.

[0015] As shown in Figures 1 and 2, the image forming apparatus 100 includes an image forming unit 1, a sheet conveying unit 2, an operation display unit 3, a communication unit 4, a memory unit 5, a control unit 6, a first paper feed control unit 7, and a second paper feed control unit 8.

[0016] The image forming unit 1 forms an image on a sheet by electrophotography based on image data input from an external information processing device such as a personal computer.

[0017] The sheet conveying section 2 conveys a sheet on which an image is to be formed by the image forming section 1.

[0018] The operation display unit 3 is a user interface of the image forming apparatus 100. The operation display unit 3 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 6. For example, the display unit is a flat panel display such as a liquid crystal display. The operation unit inputs various information to the control unit 6 in response to user operations. For example, the operation unit includes operation keys and a touch panel.

[0019] The communication unit 4 is a communication interface that executes wired or wireless data communication with an external information processing device.

[0020] The storage unit 5 is a non-volatile storage device, such as a flash memory.

[0021] The control unit 6 performs overall control of the image forming apparatus 100. As shown in FIG. 2, the control unit 6 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 11 to execute various types of processing. The RAM 13 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11. In the control unit 6, the CPU 11 executes the various control programs that are pre-stored in the ROM 12. In this way, the control unit 6 performs overall control of the image forming apparatus 100.

[0022] The first sheet feed control unit 7 controls the sheet feeding operation by the first sheet feed unit 41 (see FIG. 1) of the sheet transport unit 2. The first sheet feed control unit 7 is configured by an electronic circuit such as an integrated circuit (ASIC, DSP).

[0023] The second sheet feed control unit 8 controls the sheet feeding operation by the second sheet feed unit 42 (see FIG. 1) of the sheet transport unit 2. The second sheet feed control unit 8 is configured by an electronic circuit such as an integrated circuit (ASIC, DSP).

[0024] [Configuration of image forming unit 1 and sheet conveying unit 2] Next, the configurations of the image forming unit 1 and the sheet conveying unit 2 will be described with reference to FIGS.

[0025] As shown in FIG. 1, the image forming unit 1 includes a photosensitive drum 21, a charging device 22, an optical scanning device 23, a developing device 24, a toner container 25, a transfer roller 26, a cleaning device 27, a fixing device 28, and a paper discharge tray 29.

[0026] The photosensitive drum 21 is rotatable in the direction of the arrow shown in Fig. 1. The charging device 22 charges the circumferential surface of the photosensitive drum 21. The optical scanning device 23 irradiates the circumferential surface of the photosensitive drum 21 charged by the charging device 22 with light based on image data. An electrostatic latent image is formed on the circumferential surface of the photosensitive drum 21 by the optical scanning device 23.

[0027] The developing device 24 uses toner to develop the electrostatic latent image formed on the circumferential surface of the photosensitive drum 21. The developing device 24 forms a toner image on the circumferential surface of the photosensitive drum 21. The toner container 25 supplies toner to the developing device 24. The transfer roller 26 transfers the toner image formed by the developing device 24 onto a sheet transported by the sheet transport unit 2. The cleaning device 27 cleans the circumferential surface of the photosensitive drum 21 after the toner image has been transferred by the transfer roller 26. The transfer roller 26 is an example of a transfer unit of the present invention.

[0028] The fixing device 28 fixes the toner image transferred onto the sheet by the transfer roller 26. The sheet onto which the toner image has been fixed by the fixing device 28 is discharged to a paper discharge tray 29.

[0029] 1, the sheet conveying unit 2 includes a paper feed cassette 30, a first conveying path 31, a second conveying path 32, a third conveying path 33, a fourth conveying path 34, and a fifth conveying path 35. In FIG. 1, the first conveying path 31, the second conveying path 32, the third conveying path 33, the fourth conveying path 34, and the fifth conveying path 35 are indicated by thick solid lines.

[0030] The paper feed cassette 30 accommodates sheets on which images are formed by the image forming unit 1. For example, the paper feed cassette 30 accommodates sheets such as paper, coated paper, postcards, envelopes, and transparencies.

[0031] The first conveying path 31 is a path along which a sheet moves from the sheet feed cassette 30 to a junction position P11 (see FIG. 1) inside the housing of the image forming apparatus 100. The first conveying path 31 is connected to the second conveying path 32 at the junction position P11. In the first conveying path 31, the sheet is conveyed in a first conveying direction D1 shown in FIG.

[0032] The second conveying path 32 is a path along which the sheet travels from the junction position P11 to a branching position P12 (see FIG. 1) inside the housing of the image forming apparatus 100, via a transfer position of the toner image by the transfer roller 26 and the fixing device 28. The second conveying path 32 is connected to the third conveying path 33 and the fourth conveying path 34 at the branching position P12. In the second conveying path 32, the sheet is conveyed in a second conveying direction D2 shown in FIG. 1.

[0033] The first transport path 31 is provided with a first paper feed section 41 shown in FIG.

[0034] The first paper feed section 41 includes a first upstream roller 41A, a first downstream roller 41B, and a first sheet sensor 41C shown in Fig. 1. The first paper feed section 41 also includes a first stepping motor 41D shown in Fig. 2.

[0035] 1, the first upstream roller 41A and the first downstream roller 41B are arranged side by side along the first transport path 31. The first upstream roller 41A is arranged upstream of the first downstream roller 41B in the first transport direction D1. The first upstream roller 41A and the first downstream roller 41B transport a sheet taken out of the paper feed cassette 30 in the first transport direction D1.

[0036] 1, the first sheet sensor 41C is provided between the first upstream roller 41A and the first downstream roller 41B in the first conveying path 31. The first sheet sensor 41C detects the sheet being conveyed by the first upstream roller 41A. For example, the first sheet sensor 41C is a reflective or transmissive optical sensor.

[0037] The first stepping motor 41D drives the first upstream roller 41A and the first downstream roller 41B.

[0038] The first upstream roller 41A and the first downstream roller 41B are arranged upstream of the transfer position in the sheet transport direction in a first paper feed path (an example of a transport path according to the present invention) that passes through a transfer position of a toner image by transfer roller 26. The first paper feed path is a sheet feed path for forming an image on the surface of the sheet, and is made up of a first transport path 31 and a second transport path 32. The first upstream roller 41A and the first downstream roller 41B are an example of a transport member according to the present invention.

[0039] The first sheet feeding unit 41 feeds sheets from a first sheet feeding position P21 shown in Fig. 1. As shown in Fig. 1, the first sheet feeding position P21 is a position downstream of the first upstream roller 41A and the first downstream roller 41B in the first sheet feeding path in the sheet conveying direction.

[0040] Specifically, when a single-sided image forming process is performed using the image forming unit 1 to form an image on one side of a sheet, the first paper feed unit 41 feeds a sheet from the first paper feed position P21 at a predetermined first paper feed period.

[0041] In addition, when a double-sided image forming process is performed using the image forming unit 1 to form images on both sides of a sheet, the first paper feed unit 41 feeds the sheet from the first paper feed position P21 at the first paper feed cycle before the sheet is sent to the second paper feed unit 42 (see Figure 1).

[0042] In addition, when the double-sided image forming process is performed, after the sheet is sent to the second paper feed section 42 (see Figure 1), the first paper feed section 41 feeds the sheet from the first paper feed position P21 at a second paper feed cycle that is twice the first paper feed cycle.

[0043] The third conveying path 33 is a path along which the sheet moves from the branching position P12 to the discharge tray 29. In the third conveying path 33, a sheet having an image formed on one or both sides thereof is conveyed in a third conveying direction D3 shown in FIG.

[0044] The fourth conveying path 34 is a path along which the sheet moves from the branching position P12 to a sheet discharge port 34A (see FIG. 1) formed in the upper part of the housing of the image forming apparatus 100. In the fourth conveying path 34, the sheet having an image formed on its front surface is conveyed in a fourth conveying direction D4 shown in FIG.

[0045] The sheet discharge outlet 34A is provided with a reversing conveyance roller 34B shown in FIG. 1. The reversing conveyance roller 34B switches back the sheet and supplies the sheet to the fifth conveyance path 35. Specifically, the reversing conveyance roller 34B causes the sheet to protrude from the sheet discharge outlet 34A to the outside of the housing of the image forming apparatus 100 until it clamps the upstream end (rear end) of the sheet in the fourth conveyance direction D4. The reversing conveyance roller 34B then rotates in the reverse direction at the timing when it clamps the rear end of the sheet, thereby switching back the sheet. A sheet support tray 34C (see FIG. 1) that supports the sheet protruding from the sheet discharge outlet 34A is formed on the top surface of the housing of the image forming apparatus 100.

[0046] The fifth conveying path 35 is a path along which the sheet travels from the reverse conveying roller 34B to the joining position P11 (see FIG. 1). In the fifth conveying path 35, the sheet having an image formed on its front side is conveyed in a fifth conveying direction D5 shown in FIG.

[0047] The fifth conveying path 35 is provided with a second paper feed section 42 shown in FIG.

[0048] The second paper feed section 42 includes a second upstream roller 42A, a second downstream roller 42B, and a second sheet sensor 42C shown in Fig. 1. The second paper feed section 42 also includes a second stepping motor 42D shown in Fig. 2.

[0049] 1, the second upstream roller 42A and the second downstream roller 42B are arranged side by side along the fifth conveying path 35. The second upstream roller 42A is arranged upstream of the second downstream roller 42B in the fifth conveying direction D5. The second upstream roller 42A and the second downstream roller 42B convey the sheet conveyed from the reversing conveying roller 34B in the fifth conveying direction D5.

[0050] 1, the second sheet sensor 42C is provided between the second upstream roller 42A and the second downstream roller 42B in the fifth conveying path 35. The second sheet sensor 42C detects the sheet being conveyed by the second upstream roller 42A. For example, the second sheet sensor 42C is a reflective or transmissive optical sensor.

[0051] The second stepping motor 42D drives the second upstream roller 42A and the second downstream roller 42B.

[0052] The second upstream roller 42A and the second downstream roller 42B are arranged upstream of the transfer position in the sheet transport direction in a second paper feed path (an example of a transport path of the present invention) that passes through the transfer position of the toner image by the transfer roller 26. The second paper feed path is a sheet feed path for forming an image on the back surface of the sheet, and is made up of the fifth transport path 35 and the second transport path 32. The second upstream roller 42A and the second downstream roller 42B are an example of a transport member of the present invention.

[0053] The second paper feed unit 42 feeds sheets from a second paper feed position P22 shown in Fig. 1. As shown in Fig. 1, the second paper feed position P22 is a position downstream of the second upstream roller 42A and the second downstream roller 42B in the second paper feed path in the fifth conveying direction D5. In the image forming apparatus 100, the second paper feed position P22 is determined so that the distance from the first paper feed position P21 in the first paper feed path to the transfer position is equal to the distance from the second paper feed position P22 in the second paper feed path to the transfer position.

[0054] Specifically, when the double-sided image forming process is performed, the second sheet feeding section 42 feeds sheets from the second sheet feeding position P22 at the second sheet feeding cycle.

[0055] In image forming apparatus 100, when the double-sided image formation process is performed, the sheet feeding timings of first sheet feeding unit 41 and second sheet feeding unit 42 are set so that the sheet feeding timings by first sheet feeding unit 41 and second sheet feeding unit 42 occur alternately. That is, in second conveying path 32, sheets with images formed on the front side and sheets with images formed on the back side are conveyed alternately. Sheets with images formed on the front side by image forming unit 1 are sent to second sheet feeding unit 42 via fourth conveying path 34. Sheets with images formed on the back side by image forming unit 1 are sent to sheet output tray 29 via third conveying path 33.

[0056] Incidentally, an image forming apparatus that stops driving the second stepping motor 42D from the time when the sheet reaches the second sheet feeding position P22 until the next sheet feeding timing by the second sheet feeding unit 42 arrives is known as related art.

[0057] Here, the stepping motor may vibrate for a while after it has stopped. If the stepping motor is started again while it is vibrating, the behavior of the stepping motor will become unstable.

[0058] In the image forming apparatus according to the related art described above, in order to prevent the behavior of the second stepping motor 42D from becoming unstable, it is necessary to set the second paper feed cycle so that the next paper feed timing arrives after the vibrations caused by the second stepping motor 42D have subsided after the motor 42D has stopped. In other words, in the image forming apparatus according to the related art described above, the shortening of the interval between paper feed operations by the second paper feed unit 42 is limited. The same applies to the first paper feed unit 41.

[0059] In contrast to this, in the image forming apparatus 100 according to the embodiment of the present invention, it is possible to shorten the interval between the paper feeding operations by the first paper feeding section 41 and the second paper feeding section 42, as will be described below.

[0060] [Configuration of the first paper feed control unit 7 and the second paper feed control unit 8] Next, the configurations of the first paper feed control unit 7 and the second paper feed control unit 8 will be described with reference to FIG.

[0061] 2, the first paper feed control unit 7 includes a first detection processing unit 51 and a first drive control unit 52. The CPU 11 of the control unit 6 may execute the control program stored in the ROM 12 to function as each of the above-mentioned functional units.

[0062] The first detection processing unit 51 detects the sheet being transported by the first upstream roller 41A and the first downstream roller 41B on the upstream side in the sheet transport direction of the first sheet feeding position P21 on the first sheet feeding path.

[0063] Specifically, the first detection processing unit 51 uses the first sheet sensor 41C to detect the sheet being conveyed by the first upstream roller 41A.

[0064] Based on the timing of sheet detection by the first detection processing unit 51, the first drive control unit 52 drives the first stepping motor 41D without stopping it so that the sheet reaches the first paper feed position P21 when the next paper feed timing by the first paper feed unit 41 arrives.

[0065] For example, the first drive control unit 52 drives the first stepping motor 41D at a predetermined first rotation speed until the first detection processing unit 51 detects a sheet. When the first detection processing unit 51 detects a sheet, the first drive control unit 52 determines the deceleration timing for decelerating the first stepping motor 41D based on the timing of the sheet detection by the first detection processing unit 51. When the determined deceleration timing arrives, the first drive control unit 52 reduces the rotation speed of the first stepping motor 41D from the first rotation speed to a second rotation speed that is lower than the first rotation speed. When the next timing for the first paper feed unit 41 to feed paper arrives, the first drive control unit 52 increases the rotation speed of the first stepping motor 41D from the second rotation speed to the first rotation speed. The deceleration timing of the first stepping motor 41D is determined so that the sheet will reach the first paper feed position P21 when the next timing for the first paper feed unit 41 to feed paper arrives.

[0066] 2, the second paper feed control unit 8 includes a second detection processing unit 61 and a second drive control unit 62. The CPU 11 of the control unit 6 may execute the control program stored in the ROM 12 to function as each of the above-mentioned functional units.

[0067] The second detection processing unit 61 detects the sheet being transported by the second upstream roller 42A and the second downstream roller 42B on the upstream side of the second sheet feeding position P22 in the sheet transport direction on the second sheet feeding path.

[0068] Specifically, the second detection processing unit 61 uses the second sheet sensor 42C to detect the sheet being conveyed by the second upstream roller 42A.

[0069] Based on the timing of sheet detection by the second detection processing unit 61, the second drive control unit 62 drives the second stepping motor 42D without stopping it so that the sheet reaches the second paper feed position P22 when the next paper feed timing by the second paper feed unit 42 arrives.

[0070] For example, the second drive control unit 62 drives the second stepping motor 42D at the first rotational speed until a sheet is detected by the second detection processing unit 61. When a sheet is detected by the second detection processing unit 61, the second drive control unit 62 determines the deceleration timing for decelerating the second stepping motor 42D based on the timing of sheet detection by the second detection processing unit 61. When the determined deceleration timing arrives, the second drive control unit 62 reduces the rotational speed of the second stepping motor 42D from the first rotational speed to the second rotational speed. When the next sheet feeding timing by the second paper feed unit 42 arrives, the second drive control unit 62 increases the rotational speed of the second stepping motor 42D from the second rotational speed to the first rotational speed. The deceleration timing of the second stepping motor 42D is determined so that the sheet will reach the second paper feed position P22 when the next sheet feeding timing by the second paper feed unit 42 arrives.

[0071] [First paper feed control process] 3, the drive control method of the present invention will be described below along with an example of the procedure of the first paper feed control process executed by the first paper feed control unit 7 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the process procedures (steps) executed by the first paper feed control unit 7.

[0072] The first sheet feed control unit 7 executes the first sheet feed control process when the double-sided image forming process is executed. Note that the first sheet feed control unit 7 may execute the first sheet feed control process when the single-sided image forming process is executed.

[0073] <Step S11> First, in step S11, the first sheet feed control unit 7 determines whether or not the first sheet sensor 41C detects a sheet being conveyed by the first upstream roller 41A. The process of step S11 is an example of a detection step of the present invention, and is executed by the first detection processing unit 51 of the first sheet feed control unit 7.

[0074] Here, if the first paper feed control unit 7 determines that a sheet has been detected (Yes in S11), it shifts the process to step S12. If a sheet has not been detected (No in S11), the first paper feed control unit 7 waits for the detection of a sheet in step S11.

[0075] <Step S12> In step S12, the first paper feed control unit 7 determines the deceleration timing for reducing the rotation speed of the first stepping motor 41D from the first rotation speed to the second rotation speed based on the timing of sheet detection in the process of step S11. This deceleration timing is determined so that the sheet will reach the first paper feed position P21 when the next paper feed timing by the first paper feed unit 41 arrives.

[0076] <Step S13> In step S13, the first sheet-feed control unit 7 determines whether the deceleration timing determined in the process of step S12 has arrived.

[0077] Here, if the first sheet feed control unit 7 determines that the deceleration timing has arrived (Yes in S13), it shifts the process to step S14. If the deceleration timing has not arrived (No in S13), the first sheet feed control unit 7 waits for the deceleration timing to arrive in step S13.

[0078] <Step S14> In step S14, the first paper-feed control unit 7 reduces the rotation speed of the first stepping motor 41D from the first rotation speed to the second rotation speed.

[0079] <Step S15> In step S15, the first sheet feeding control unit 7 determines whether the next timing for the first sheet feeding unit 41 to feed has arrived.

[0080] Here, if the first paper feed control unit 7 determines that the next paper feed timing has arrived (Yes in S15), it shifts the process to step S16. On the other hand, if the next paper feed timing has not arrived (No in S15), the first paper feed control unit 7 waits for the next paper feed timing to arrive in step S15.

[0081] <Step S16> In step S16, the first sheet-feed control unit 7 increases the rotation speed of the first stepping motor 41D from the second rotation speed to the first rotation speed. The processes from step S12 to step S16 are an example of a drive control step of the present invention, and are executed by the first drive control unit 52 of the first sheet-feed control unit 7.

[0082] <Step S17> In step S17, the first sheet feeding control unit 7 determines whether or not all of the sheets on which images are to be formed in the double-sided image forming process have been fed by the first sheet feeding unit 41.

[0083] Here, when the first sheet feed control unit 7 determines that all of the sheets on which images are to be formed in the double-sided image forming process have been fed by the first sheet feed unit 41 (Yes in S17), it ends the first sheet feed control process. On the other hand, when all of the sheets on which images are to be formed in the double-sided image forming process have not been fed by the first sheet feed unit 41 (No in S17), the first sheet feed control unit 7 shifts the process to step S11.

[0084] [Second paper feed control process] Next, with reference to FIG. 4, an example of the procedure of the second paper feed control process executed by the second paper feed control unit 8 in the image forming apparatus 100 and the drive control method of the present invention will be described.

[0085] The second paper feed control unit 8 executes the second paper feed control process when the double-sided image forming process is executed.

[0086] <Step S21> First, in step S21, the second sheet feed control unit 8 determines whether or not the second sheet sensor 42C detects a sheet being conveyed by the second upstream roller 42A. The process of step S21 is an example of a detection step of the present invention, and is executed by the second detection processing unit 61 of the second sheet feed control unit 8.

[0087] Here, if the second paper feed control unit 8 determines that a sheet has been detected (Yes in S21), it shifts the process to step S22. On the other hand, if a sheet has not been detected (No in S21), the second paper feed control unit 8 waits for the detection of a sheet in step S21.

[0088] <Step S22> In step S22, the second paper feed control unit 8 determines the deceleration timing for reducing the rotation speed of the second stepping motor 42D from the first rotation speed to the second rotation speed based on the timing of sheet detection in the process of step S21. This deceleration timing is determined so that the sheet will reach the second paper feed position P22 when the next paper feed timing by the second paper feed unit 42 arrives.

[0089] <Step S23> In step S23, the second sheet-feed control unit 8 determines whether the deceleration timing determined in the process of step S22 has arrived.

[0090] Here, if the second paper feed control unit 8 determines that the deceleration timing has arrived (Yes in S23), it shifts the process to step S24. If the deceleration timing has not arrived (No in S23), the second paper feed control unit 8 waits for the deceleration timing to arrive in step S23.

[0091] <Step S24> In step S24, the second paper feed control unit 8 reduces the rotation speed of the second stepping motor 42D from the first rotation speed to the second rotation speed.

[0092] <Step S25> In step S25, the second paper feed control unit 8 determines whether the next timing for the second paper feed unit 42 to feed paper has arrived.

[0093] Here, if the second paper feed control unit 8 determines that the next paper feed timing has arrived (Yes in S25), it shifts the process to step S26. If the next paper feed timing has not arrived (No in S25), the second paper feed control unit 8 waits for the next paper feed timing to arrive in step S25.

[0094] <Step S26> In step S26, the second paper feed control unit 8 increases the rotation speed of the second stepping motor 42D from the second rotation speed to the first rotation speed. The processes from step S22 to step S26 are an example of a drive control step of the present invention, and are executed by the second drive control unit 62 of the second paper feed control unit 8.

[0095] <Step S27> In step S27, the second sheet feed control unit 8 determines whether or not all of the sheets on which images are to be formed in the double-sided image forming process have been fed by the second sheet feed unit 42.

[0096] Here, when the second sheet feed control unit 8 determines that all of the sheets on which images are to be formed in the double-sided image forming process have been fed by the second sheet feed unit 42 (Yes in S27), it ends the second sheet feed control process. On the other hand, when all of the sheets on which images are to be formed in the double-sided image forming process have not been fed by the second sheet feed unit 42 (No in S27), the second sheet feed control unit 8 shifts the process to step S21.

[0097] In this manner, in the image forming apparatus 100, the second drive control unit 62 drives the second stepping motor 42D based on the sheet detection timing by the second detection processing unit 61 so that the sheet reaches the second sheet feed position P22 when the next sheet feed timing by the second sheet feed unit 42 arrives. That is, in the image forming apparatus 100, instead of stopping the drive of the second stepping motor 42D when the sheet reaches the second sheet feed position P22, the rotational speed of the second stepping motor 42D is decelerated before the sheet reaches the second sheet feed position P22. This makes it possible to feed the sheet from the second sheet feed position P22 at the second sheet feed cycle without stopping the second stepping motor 42D. Therefore, compared to a configuration in which the second stepping motor 42D is stopped, it is possible to shorten the interval between sheet feed operations by the second sheet feed unit 42.

[0098] [Notes on the Invention] The following will provide an outline of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0099] <Appendix 1> an image forming apparatus including: a transfer unit that transfers a toner image onto a sheet; a paper feed unit that includes a transport member that transports the sheet upstream of a transfer position on a transport path of the sheet that passes through a transfer position of the toner image by the transfer unit, and that feeds the sheet at a predetermined paper feed period from a paper feed position downstream of the transport member on the transport path in the transport direction; a stepping motor that drives the transport member; a detection processing unit that detects the sheet transported by the transport member upstream of the paper feed position on the transport path in the transport direction; and a drive control unit that drives the stepping motor based on the detection timing of the sheet by the detection processing unit so that the sheet reaches the paper feed position when the next paper feed timing by the paper feed unit arrives.

[0100] <Appendix 2> A drive control method executed in an image forming apparatus including a transfer unit that transfers a toner image onto a sheet, a transport member that transports the sheet upstream in the sheet transport direction of the sheet from a transport position downstream in the transport direction of the sheet from the transport path that passes through the transfer position of the toner image by the transfer unit, and a stepping motor that drives the transport member, the drive control method including: a detection step that detects the sheet transported by the transport member upstream in the transport direction of the sheet from the transport path from the transport position; and a drive control step that drives the stepping motor based on the detection timing of the sheet by the detection step so that the sheet reaches the transport position when the next paper feed timing by the paper feed unit arrives. [Explanation of symbols]

[0101] 1 Image forming unit 2 Sheet transport section 3 Operation display section 4. Communications Department 5 Storage section 6 Control Unit 7 First paper feed control section 8 Second paper feed control section 21 Photosensitive drum 22 Charging device 23 Optical scanning device 24 Developing device 25 Toner Container 26 Transfer roller 27 Cleaning Device 28 Fixing device 29 Paper output tray 30 Paper cassette 31 First conveying route 32 Second conveying path 33 Third transport route 34 4th Transport Route 35 5th Transport Route 41 1st paper feed section 41A First upstream roller 41B First downstream roller 41C 1st seat sensor 41D 1st stepping motor 42 2nd paper feed section 42A Second upstream roller 42B Second downstream roller 42C Second seat sensor 42D 2nd stepping motor 51 First detection processing section 52 First drive control section 61 Second detection processing section 62 second drive control section 100 Image forming device

Claims

1. a transfer unit that transfers the toner image onto a sheet; a paper feed unit including a conveying member that conveys the sheet upstream of a transfer position in a conveying path of the sheet that passes through a transfer position of the toner image by the transfer unit, in a conveying direction of the sheet, and that feeds the sheet from a paper feed position downstream of the conveying member in the conveying path in the conveying direction at a predetermined paper feed cycle; a stepping motor that drives the conveying member; a detection processing unit that detects the sheet being conveyed by the conveying member on the upstream side of the sheet feeding position on the conveying path in the conveying direction; a drive control unit that drives the stepping motor based on the timing of detection of the sheet by the detection processing unit so that the sheet reaches the sheet feeding position when the next sheet feeding timing by the sheet feeding unit arrives; An image forming apparatus comprising:

2. a sheet feeding unit including a transfer unit that transfers a toner image onto a sheet, a transport member that transports the sheet upstream of a transfer position in a transport path of the sheet that passes through a transfer position of the toner image by the transfer unit in a transport direction of the sheet, and that feeds the sheet from a paper feeding position downstream of the transport member in the transport path in the transport direction at a predetermined paper feeding cycle; and a stepping motor that drives the transport member, a detecting step of detecting the sheet conveyed by the conveying member on the upstream side of the sheet feeding position in the conveying path in the conveying direction; a drive control step of driving the stepping motor based on the timing of detection of the sheet in the detection step so that the sheet reaches the sheet feeding position when the next sheet feeding timing by the sheet feeding unit arrives; A drive control method including:

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