JP2015018058A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to prevent a driving unit from being enlarged.SOLUTION: An image forming apparatus includes: housing means; transfer means; a first conveyance path; a second conveyance path; first conveyance means for conveying a recording material to the transfer means at a predetermined speed; and second conveyance means. The image forming apparatus includes: driving means for rotating the first and second conveyance means; switching means for selecting a first state where the driving means transmits driving force to the first conveyance means or a second state where the driving means transmits the driving force to the first and second conveyance means; and control means for controlling the driving means and the switching means. The control means rotates the driving means at a first rotation speed when the first conveyance means conveys the recording material at a predetermined speed, rotates the driving means at a second rotation speed lower than the first rotation speed when conveying the recording material at a speed lower than the predetermined speed; and rotates the driving means at the second rotation speed before the switching means switches the driving means from the first state to the second state.

Description

  The present invention relates to a printing apparatus, and more particularly to an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser beam printer, a configuration is known in which a plurality of rollers that transport paper are rotated by the same drive source.

  Patent Document 1 describes a configuration in which a plurality of conveyance rollers that convey paper and a motor are connected by a clutch or the like, and each roller is rotated by the same motor.

JP 2002-59601 A

  Here, the torque required for the motor is larger when the driving of the roller is started with the clutch turned on than in the steady state where the driving of the roller is completed and the speed is stable. For this reason, in the configuration of Patent Document 1, when a drive of another roller is newly started while a certain roller is rotated, a particularly required torque is increased. The larger the required torque, the larger the motor that needs to be used, and the configuration of the drive unit (motor holding member, drive gear, etc.) including the motor may increase in size and increase costs. It was.

  An object of the present invention is to provide an image forming apparatus in which an increase in size of a drive unit is suppressed.

  The image forming apparatus of the present invention includes a storage unit that stores a recording material, a transfer unit that transfers an image to the recording material, and a first transport path for transporting the recording material from the storage unit to the transfer unit. And a second transport path different from the first transport path for transporting the recording material, and a first transport means for transporting the recording material on the first transport path, wherein the recording material In the image forming apparatus, the image forming apparatus includes: a first conveying unit that conveys the material to the transfer unit at a predetermined speed; and a second conveying unit that conveys the recording material in the second conveying path. A first driving means for rotationally driving the second conveying means, a first state in which the first driving means transmits a driving force to the first conveying means, and the first driving means A second state in which driving force is transmitted to the first conveying means and the second conveying means A switching means for switching, a control means for controlling the first driving means and the switching means, the control means when the recording material is conveyed at the predetermined speed by the first conveying means. The first driving means is rotated at the first rotation speed, and the first driving means is moved to the first rotation when the recording material is conveyed at a speed slower than the predetermined speed by the first conveying means. The first drive unit is rotated at a second rotational speed that is slower than the speed, and the first drive unit is moved to the second state before the switching unit switches the first drive unit from the first state to the second state. It is controlled to rotate at a rotation speed of 2.

  According to the present invention, it is possible to provide an image forming apparatus in which an increase in size of a drive unit is suppressed.

Sectional view showing an example of an image forming apparatus Relationship diagram between each roller and each motor in Examples 1 and 2 Block diagram of control system Relationship between rotation speed of stepping motor and outputable torque Relationship between outputtable torque of stepping motor and required torque Flowchart in the first embodiment Relationship between the outputtable torque of the stepping motor and the required torque in the first embodiment Flowchart in the second embodiment Relationship between output possible torque and required torque of stepping motor in embodiment 2 Flowchart in the third embodiment

Example 1
(Configuration of image forming apparatus)
FIG. 1 shows a configuration diagram of the image forming apparatus 100 in this embodiment. In this embodiment, an example of a laser beam printer is shown as the image forming apparatus.

  In FIG. 1, reference numeral 122 denotes a photosensitive drum made of an organic photosensitive member or an amorphous silicon photosensitive member, which rotates clockwise at a predetermined peripheral speed (hereinafter referred to as a steady speed). The peripheral surface of the photosensitive drum 122 is uniformly charged to a predetermined polarity and potential by a charging roller 123. Then, the laser beam output from the laser optical unit 108 is reflected and irradiated on the charged surface by the laser beam reflecting mirror 107, thereby performing exposure. The laser beam is modulated (ON / OFF conversion) in accordance with a time-series electric digital pixel signal of target image information input from an image signal generation device such as an image reading device or a computer (not shown). As a result of the exposure, an electrostatic latent image corresponding to the image information is formed on the photosensitive drum 122. The electrostatic latent image thus formed corresponding to the target image is developed by the developing roller 121. Here, in the image forming apparatus 100 according to the present exemplary embodiment, the photosensitive drum 122, the charging roller 123, the developing roller 121, and a toner storage unit (not illustrated) that stores toner are integrated as a cartridge. It becomes removable with respect to. When the user runs out of toner, the cartridge can be replaced. Further, the present invention is not limited to such a cartridge type image forming apparatus 100, and may be applied to a configuration in which members such as the photosensitive drum 122, the charging roller 123, and the developing roller 121 are installed in the image forming apparatus 100. Can do.

  Further, the paper P as a recording material is pulled out by a pickup roller 102 from a paper feed cassette 101 as a storage unit, and one sheet is fed by a paper feed roller 103. Here, the recording material also includes an OHP sheet and cloth. The paper P is transported on the transport path 150 by the transport roller 104 and the registration roller 105 and then sent to the photosensitive drum 122. The mirror image toner image formed on the photoconductive drum 122 is transferred from the photoconductive drum 122 to the paper P when the transfer roller 112 supplies a charge having a polarity opposite to that of the toner from the back surface of the paper P. The sheet P that has received the transfer of the toner image is separated from the photosensitive drum 122 and sent to the fixing device 130, and the toner image is fixed to the sheet P. In FIG. 1, 131 is a thermistor, 132 is a heater, 133 is a fixing film, and 134 is a pressure roller. The paper P on which the toner image is fixed is guided to the FD roller 111 by a double-side reverse path switching flapper (not shown) when single-sided printing or double-sided printing has been completed. The paper is ejected. When printing on the front side is not completed in double-sided printing, the paper P is guided to the reverse roller 110 by a double-side reverse path switching flapper (not shown). Then, after the rear end of the paper P (the end on the upstream side with respect to the transport direction of the paper P) passes through the double-side reversing path switching flapper (not shown), the transport direction of the paper P is reversed by the reverse roller 110. As a result, the paper P is sent to the duplex conveying roller 142. The duplex conveying roller 142 conveys the sheet to the registration roller 105 again.

(Drive configuration)
FIG. 2 is a diagram illustrating a relationship between each roller of the image forming apparatus 100 according to the present exemplary embodiment and a motor that supplies a driving force (torque) to the roller. In the image forming apparatus 100 according to the present exemplary embodiment, a conveyance motor 301 and an image forming motor 302 are used. The transport motor 301 drives a double-sided transport roller 142 via a pickup roller 102, a paper feed roller 103, a transport roller 104, a registration roller 105, and a double-sided paper refeed clutch 304. The image forming motor 302 drives the reverse roller 110 via the photosensitive drum 122, the transfer roller 112, the fixing film 133, the pressure roller 134, the FD roller 111, and the double-side reverse clutch 303. In this embodiment, a stepping motor is used as the transport motor 301.

  The double-side reversing clutch 303 plays a role of reversing the rotation direction of the reversing roller 110. The timing at which the reverse roller 110 is reversed is determined based on the timing at which the paper discharge sensor 109 detects the trailing edge of the paper P. Further, the double-sided refeed clutch 304 transmits the driving force of the carry motor 301 to the double-sided carry roller 142. The double-sided conveyance roller 142 stops when the double-sided paper re-feeding clutch 304 is OFF, and the double-sided conveyance roller 142 is driven when the double-sided refeed clutch 304 is ON. In the present embodiment, before the leading edge of the paper P reaches the double-sided conveyance roller 142 with reference to the timing when the double-sided sensor 141 detects the leading edge of the paper P (the end on the downstream side with respect to the conveyance direction of the paper P). The driving of the duplex conveying roller 142 is started. Thereby, it is possible to prevent the paper P that has been transported to the double-sided transport path 151 by the reversing roller 110 from being sent to the stopped double-sided transport roller 142 and becoming jammed. Then, the drive of the double-sided conveyance roller 142 is temporarily stopped at the timing when the trailing edge of the paper P passes through the reverse roller 110, and the double-sided conveyance is again performed at the timing when the space between the paper P fed from the paper feeding cassette 101 is secured. The roller 142 is driven to convey the paper P to the registration roller 105.

(Control system block diagram)
FIG. 3 is a block diagram of the control system in the present embodiment. The control unit 200 is a microprocessor that controls the image forming apparatus 100 and includes memories such as a ROM 203 and a RAM 204 therein. The control means 200 is roughly divided into the following two functions.
Image forming control means 201 for controlling image forming conditions when forming an image on paper P
A conveyance control unit 202 that controls conveyance of the paper P based on information from the image formation control unit 201.
A high voltage generation circuit 126, a heater 132, a thermistor 131, and a scanner / laser control circuit 400 are connected to the image formation control unit 201. The high voltage generation circuit 126 is a circuit that generates a voltage to be applied to the transfer roller 112. The heater 132 supplies a necessary amount of heat to the fixing film 133 in order to fix the toner image on the paper P. The thermistor 131 is provided to detect the temperature of the heater 132. The scanner / laser control circuit 400 controls on / off of the laser beam output from the laser optical unit 108.

  A registration sensor 106, a paper discharge sensor 109, and a double-sided sensor 141, which are detection means for detecting the paper P, are connected to the transport control means 202. Further, the conveyance control unit 202 includes a conveyance motor 301 that is a driving unit that rotationally drives each roller, an image forming motor 302, a double-sided reversing clutch 303 that is a switching unit that switches between transmission and non-transmission of torque supplied from the motor, A paper feed clutch 304 is connected.

(Charge motor characteristics)
Next, characteristics of the transport motor 301 used in this embodiment will be described. In this embodiment, a stepping motor is used as the transport motor 301. As shown in FIG. 4, the stepping motor has a property that the torque that can be output decreases as the speed increases. Therefore, when the speed of the motor is accelerated from V1 to V2, the torque that can be output to drive the double-sided conveyance roller 142 decreases from T1 to T2. On the other hand, when the double-sided refeed clutch 304 is driven to start driving the double-sided conveyance roller 142, a larger torque is required than in a steady state where the driving of the double-sided conveyance roller 142 is completed and the speed is stable. . Therefore, when the process of accelerating the speed of the motor and the process of starting driving the double-sided conveyance roller 142 are overlapped, the torque required for the motor is maximized. This is shown in FIG. In FIG. 5, the torque margin (remaining torque that can be output by the motor) when two processes overlap is ΔT. If this torque margin ΔT becomes a negative value, the motor will step out. Therefore, the motor installed in the apparatus needs to be able to secure this torque margin ΔT or more so as to operate stably, resulting in an increase in the size of the motor.

(Conveyance motor speed control)
Next, speed control of the conveyance motor 301 will be described with reference to the flowchart of FIG. Note that the control based on the flowchart of FIG. 6 is executed by the control unit 200 described with reference to FIG. 3 based on a program stored in the ROM 203.

  FIG. 6A will be described. In the flowchart of FIG. 6A, it is assumed that the image forming operation is started and the conveyance motor 301 is rotating at a speed equivalent to that of the image forming motor 302. First, it is assumed that the sheet P is fed by the pickup roller 102 and the sheet feeding roller 103 and then conveyed by the conveying roller 104 at a constant speed. Thereafter, when the registration sensor 106 detects the leading edge of the paper P, the control unit 200 first determines whether there is a preceding paper (S601). When there is no preceding sheet, there is no need to adjust the gap between the sheets, so the conveyance motor 301 maintains the rotation speed equivalent to that of the image forming motor 302, and the speed adjustment process ends as it is. When there is a preceding sheet, the control unit 200 determines a distance to be corrected (hereinafter referred to as a target correction amount) from the target sheet interval and the actual sheet interval measured by the registration sensor 106 (S602). For example, the target correction amount is obtained by storing the time when the registration sensor 106 detects the trailing edge of the preceding sheet and the time when the leading edge of the succeeding sheet is detected, and comparing the difference time with a preset time. Can do. The control means 200 calculates the target speed and the time for rotation at that speed according to the target correction amount (S603), and starts acceleration / deceleration control of the transport motor 301 (S604). The acceleration / deceleration control of the conveyance motor 301 is a period from when the leading edge of the paper P passes the position facing the registration sensor 106 until reaching the transfer nip portion (transfer position) formed by the photosensitive drum 122 and the transfer roller 112. Done in When performing speed control, the control means 200 starts acceleration / deceleration end determination described later (S605). This acceleration / deceleration end determination is executed in parallel with the processing of FIG. 6A until an acceleration / deceleration end request is made (until the flag memory provided in the RAM 204 of the control means 200 becomes 1). Here, the flag memory is initialized at the same time as the start of acceleration / deceleration control (it is 0), and is set to 1 when there is a request to end acceleration / deceleration.

  Next, it is determined whether or not there is an ON request for the double-sided sheet re-feeding clutch 304 (S606). Here, the ON request for the double-sided paper re-feeding clutch 304 is requested when the double-sided sensor 141 detects the leading edge of the paper P. When there is a request to turn on the double-sided paper re-feeding clutch 304, the double-sided paper re-feeding clutch 304 is actually switched to the ON state by the control means 200 after a predetermined time, and the ON request is cleared. When there is no ON request for the double-sided refeed clutch 304 and an acceleration / deceleration end request is made based on the acceleration / deceleration end determination, the control means 200 returns the rotation speed of the carry motor 301 to the rotation speed corresponding to the steady speed and adjusts the speed. The process ends (S613, S614). When there is no acceleration / deceleration end request in S613, the control unit 200 repeatedly performs S606 and S613, and monitors the ON request of the double-sided refeed clutch 304 and the acceleration / deceleration end request. When there is a request to turn on the double-sided sheet re-feeding clutch 304 in S603, the control unit 200 determines which of the current rotation speed Vnow and rotation speed Vclon of the transport motor 301 is higher (S607). Here, the rotation speed Vclon is a speed at which the carry motor 301 does not step out even when the double-sided paper refeed clutch 304 is turned on. Therefore, when the current rotation speed Vnow of the conveyance motor 301 is equal to or lower than Vclon, a sufficient torque margin is ensured even if the double-sided paper refeed clutch 304 is turned on. Therefore, it is not necessary to decelerate the transport motor 301, and the control means 200 performs the acceleration / deceleration end request monitoring process in S614. If the current rotation speed Vnow of the conveyance motor 301 is higher than Vclon, it is necessary to reduce the upper limit value of the conveyance motor 301 to Vclone before the double-sided refeed clutch 304 is turned on. For this purpose, the control unit 200 compares the time until the double-sided paper re-feeding clutch 304 is turned on with the time required to decelerate the rotation speed of the transport motor 301 from Vnow to Vclon + a predetermined margin amount ( S608). When the control unit 200 determines that deceleration is necessary, the control unit 200 reduces the rotation speed of the transport motor 301 to Vclon (S609). When the control unit 200 determines that deceleration is not necessary, the control unit 200 performs acceleration / deceleration end determination (S613), and repeats the processing of S606 to S608 to monitor the current rotational speed and the timing at which deceleration is necessary. To do. Next, when the rotation speed of the transport motor 301 is decelerated to Vclone by the control unit 200, the time when the torque is sufficiently stabilized has elapsed after turning on the double-sided refeed clutch 304 while performing the acceleration / deceleration end determination. (S610, S611). When the torque is stabilized, the control unit 200 accelerates the rotation speed of the transport motor 301 again, and returns to the acceleration / deceleration end determination and the monitoring process for the ON request of the double-sided paper refeed clutch 304.

  Next, acceleration / deceleration end determination will be described with reference to FIG. The control means 200 always performs acceleration / deceleration end determination after performing acceleration / deceleration control. First, the control means 200 constantly updates how much the gap between the preceding paper and the preceding paper can be corrected by changing the conveyance speed of the paper P (S603). This corrected distance is defined as the current correction amount. Then, the correction amount during the return from the current rotation speed Vnow to the rotation speed corresponding to the steady speed is predicted, and when the sum of the correction amount and the current correction amount is equal to or greater than the target correction amount, an acceleration / deceleration end request is issued (S632). The control unit 200 ends the acceleration / deceleration end request monitoring process. When the paper P reaches the photosensitive drum 122 at a speed higher than the steady speed, the transferred toner image extends in the transport direction due to the speed difference from the photosensitive drum 122. Therefore, it is necessary to finish the acceleration / deceleration process before the leading edge of the paper P enters the transfer roller 112 and return the rotation speed of the transport motor 301 to the rotation speed corresponding to the steady speed. That is, the control unit 200 may end the acceleration / deceleration control even when the correction of the target correction amount is not completed in S631. This is defined as a forced termination condition in S633. In step S633, the control unit 200 determines whether the leading end position of the paper P when the current rotational speed Vnow is returned to the rotational speed corresponding to the steady speed reaches the position before the predetermined margin from the transfer roller 112. . If it is determined that it does not reach, it is determined that the acceleration / deceleration control can be continued, and the process returns to S631 to monitor the target correction amount and the current correction amount. When it is determined that the acceleration / deceleration control is reached, it is determined that there is no room for continuing the acceleration / deceleration control, the acceleration / deceleration end request is determined to be requested (S632), and the monitoring process is terminated.

  FIG. 7 shows a state where the above control is executed to control the rotation speed of the transport motor 301. In FIG. 7, the rotational speed of the transport motor 301 is decelerated in accordance with the timing when the double-sided paper re-feeding clutch 304 is turned on, so that a larger torque margin ΔT can be secured as compared with FIG. 2.

  As described above, according to the present embodiment, the rotational speed of the transport motor 301 is reduced in accordance with the timing when the double-sided sheet re-feeding clutch is turned on, so that the increase in the size of the motor and the decrease in throughput are minimized. It is possible to adjust the gap between the paper.

  Further, in the present exemplary embodiment, the image forming apparatus 100 that secures a large torque margin when the process of accelerating the rotation speed of the motor and the process of starting the driving of the roller overlap has been described. However, the present embodiment is not limited to the case where the process of accelerating the rotation speed of the motor is performed for paper spacing adjustment. That is, the present invention can be applied to a case where the motor is rotating at a normal rotation speed. In that case, when starting the driving of the roller with the clutch turned ON, a large torque margin can be secured by temporarily decelerating to a speed slower than the normal rotation speed. As a result, an increase in the size of the motor can be suppressed.

(Example 2)
In the first embodiment, the torque margin is secured by adjusting the rotation speed of the carry motor 301 in accordance with the ON timing of the double-sided sheet re-feeding clutch 304. Further, the double-sided paper re-feeding clutch 304 described in the first embodiment is turned on before the leading edge of the paper P reaches the double-sided conveyance roller 142 to control the paper jam. Here, the timing at which the double-sided refeed clutch 304 is actually turned on is determined based on the timing at which the double-sided sensor 141 detects the leading edge of the paper P. This is because the double-sided sensor 141 is provided in the vicinity of the double-sided conveyance roller 142 and the time for the paper P to reach immediately before the double-sided conveyance roller 142 can be accurately measured. As a result, the time during which the double-sided paper re-feeding clutch 304 is turned on can be shortened as much as possible, and the temperature rise of the double-sided paper re-feeding clutch 304 due to energization can be suppressed. However, if there is some allowance for the temperature rise, the double-sided refeed clutch 304 may be turned on earlier than the timing at which the double-sided sensor 141 detects the paper P.

  Therefore, in the second embodiment, the torque peak is suppressed and the torque margin is secured by controlling the timing at which the double-sided sheet re-feeding clutch 304 is turned on so as to avoid the period during which acceleration / deceleration control is performed. The description of the main part is the same as that of the first embodiment, and only the parts different from the first embodiment will be described here.

(Control of double-sided refeed clutch)
The characteristic control of this embodiment will be described with reference to the flowchart of FIG. Note that the control based on the flowchart of FIG. 8 is executed by the control unit 200 described in FIG. 3 based on a program stored in the ROM 203.

  FIG. 8A will be described. The processing from S700 to S702 is the same as S601 to S603 in FIG. After S702, the control means 200 does not immediately execute the acceleration / deceleration control, and determines in S703 whether there is an ON request for the double-sided refeed clutch 304 (S701). In the present embodiment, when there is no ON request, it is assumed that the preceding paper does not reach the duplex conveying roller 142 during acceleration / deceleration control. In the first embodiment, there is an ON request at the timing when the leading edge of the paper P is detected by the double-sided sensor 141. However, a sensor that detects the paper P on the upstream side in the transport direction may be provided in order to satisfy the above-described condition (for example, discharge) Paper sensor 109). Therefore, if there is no ON request, the control means 200 immediately performs acceleration / deceleration control described later in S704 (S704). On the other hand, when there is a request for turning on the double-sided paper re-feeding clutch 304, the control unit 200 compares the time until the double-sided paper re-feeding clutch 304 is turned on with the time until the acceleration / deceleration control is completed (S705). In S705, when the ON timing of the double-sided paper refeed clutch 304 is later than the acceleration / deceleration control completion timing, or when the acceleration / deceleration target speed is equal to or lower than Vclone (S709), the double-sided paper refeed clutch 304 is turned on as scheduled. However, a sufficient torque margin is secured. Therefore, acceleration / deceleration control is started by the control means 200 (S706), and the ON processing of the double-sided paper refeeding clutch 304 is executed after waiting for the scheduled ON timing of the double-sided refeeding clutch 304 (S707, S708). In S705 and S706, when the ON timing of the double-sided refeed clutch 304 is predicted to be under acceleration / deceleration control, and the target speed is larger than Vclon, the control means 200 first moves forward from the plan and double-sided refeed clutch. An ON process 304 is performed (S710). Then, the control unit 200 performs acceleration / deceleration control after waiting for a time that the torque fluctuation due to the ON of the double-sided sheet re-feeding clutch 304 is stabilized (S711, S712).

  Regarding the acceleration / deceleration control execution processing, the control unit 200 changes the rotation speed of the transport motor 301 to the acceleration / deceleration target speed (S731), and then waits until the acceleration / deceleration control end request shown in FIG. (S732, S733). Then, the rotation speed of the conveyance motor 301 is returned to the rotation speed corresponding to the steady speed (S733).

  FIG. 9 shows a state in which the above control is executed and the timing for turning on the double-sided sheet re-feeding clutch 304 is controlled. This corresponds to the processing of S710 in the flowchart of FIG. In FIG. 9, since the timing for turning on the double-sided paper refeed clutch 304 is controlled so as to avoid the period for executing the acceleration / deceleration control, a larger torque margin ΔT can be secured as compared with FIG.

  As described above, according to the present embodiment, by controlling the timing when the double-sided sheet re-feed clutch 304 is turned on so as to avoid the period for executing the acceleration / deceleration control, the increase in the size of the motor and the decrease in the throughput are minimized. Meanwhile, it is possible to adjust the gap between the preceding sheet and the preceding sheet.

Example 3
In the second embodiment, the torque margin is ensured so that the acceleration control execution timing and the ON timing of the double-side refeed clutch do not overlap each other by moving the ON timing of the double-side refeed clutch 304 forward. In the present embodiment, an example will be described in which a torque margin is ensured by controlling the conveyance speed of the paper P in the double-sided conveyance path 151 so that the execution period of acceleration control and the ON timing of the double-sided refeed clutch do not overlap. .

  In the present embodiment, the configuration of the first embodiment is basically used, and the reverse roller 110 is driven by a reverse motor (not shown). The reversing motor is connected to the conveyance control unit 202 in the same manner as the conveyance motor 301 and the image forming motor 302. Unless otherwise specified, it is assumed that the reversing motor is driven at the same speed as the image forming motor 302. The other main parts are the same as in the first embodiment, and only the parts different from the first embodiment will be described here.

(Reverse motor speed control)
The characteristic control of this embodiment will be described with reference to the flowchart of FIG. Note that the control based on the flowchart of FIG. 10 is executed by the control unit 200 described with reference to FIG.

  The processing from S800 to S802 is the same as S601 to S603 in FIG. In the present embodiment, after S802, the control unit 200 performs acceleration / deceleration control in parallel with this sequence (S803). Here, the acceleration / deceleration control process is the same as that of the second embodiment. When the acceleration / deceleration control is started, the control unit 200 determines whether there is a request to turn on the double-sided paper re-feeding clutch for the preceding paper (S804). If there is no request to turn on the double-sided sheet re-feeding clutch, the control unit 200 performs only the acceleration / deceleration control process as it is and ends. Also in the present embodiment, as in the second embodiment, when there is no ON request, it is assumed that the preceding sheet does not reach the duplex conveying roller 142 during acceleration / deceleration control. When there is an ON request for the double-sided paper re-feeding clutch, the control unit 200 compares the ON timing of the double-sided paper re-feeding clutch 304 and the acceleration / deceleration control completion timing when it is assumed that the reverse roller is driven at a steady speed (S805). . When the ON timing of the double-sided paper refeed clutch 304 is later than the acceleration / deceleration control completion timing in S805, or when the acceleration / deceleration target speed is equal to or lower than Vclone (S806), the double-sided paper refeed clutch 304 is turned on as scheduled. However, a sufficient torque margin is secured. Therefore, the reversing motor conveys the paper P while maintaining the steady speed. Then, the control unit 200 waits until the double-sided paper feed clutch 304 reaches the double-sided conveyance roller 142, and the control unit 200 turns on the double-sided paper feed clutch 304 (S808, S809). If the ON timing of the double-sided refeed clutch 304 is under acceleration / deceleration control and the target speed is greater than Vclon, the control means 200 temporarily reduces or stops the rotation speed of the reversing motor (S807). . Thereby, the time for the leading edge of the paper to reach the double-sided conveyance roller 142 can be delayed, and after the acceleration / deceleration control is completed, the leading edge of the paper P reaches the double-sided conveyance roller 142. Finally, after the speed adjustment of the reversing motor is completed, the control unit 200 waits until the paper P reaches the double-sided conveyance roller 142, and the control unit 200 turns on the double-sided refeed clutch 304 (S808, S809).

  As described above, according to the present embodiment, by adjusting the rotation speed of the reversing motor and shifting the timing when the double-sided sheet re-feeding clutch 304 is turned on, the size of the motor and the decrease in throughput are minimized, and the preceding It is possible to adjust the gap between the paper.

  Further, in this embodiment, the ON timing of the double-sided refeed clutch 304 is delayed by decelerating the rotation speed of the reverse motor, but the present invention is not limited to this. By accelerating the rotation speed of the reversing motor, the ON timing of the double-sided paper re-feeding clutch 304 may be advanced by shifting the ON timing of the double-sided paper re-feeding clutch 304.

  In the above embodiment, a stepping motor is used as the transport motor 301. However, any driving means having the properties shown in FIG.

  In the above-described embodiment, the configuration in which the conveyance motor 301 and the double-sided conveyance roller 142 provided in the double-sided conveyance path 151 are connected by a clutch has been described. However, the present invention is not limited to this configuration, and can also be applied to a configuration in which the conveyance motor 301 and a roller provided in another conveyance path are connected by a clutch. For example, the present invention can be applied to a configuration in which a roller provided on a conveyance path for conveying the paper P from a manual feed tray (not shown) to a transfer position is connected by a clutch.

  In the above embodiment, an example of a laser beam printer is shown. However, the image forming apparatus to which the present invention is applied is not limited to this, and a printer of another printing system such as an ink jet printer or a copying machine. But it is good.

DESCRIPTION OF SYMBOLS 101 Paper feed cassette 105 Registration roller 112 Transfer roller 142 Double-sided conveyance roller 150 Conveyance path 151 Double-sided conveyance path 200 Control means 301 Conveyance motor 304 Double-sided refeed clutch

Claims (9)

Storage means for storing the recording material;
Transfer means for transferring an image to the recording material;
A first transport path for transporting the recording material from the storage means to the transfer means;
A second transport path different from the first transport path for transporting the recording material;
First conveying means for conveying the recording material in the first conveying path, wherein the recording material is conveyed to the transfer means at a predetermined speed;
In the image forming apparatus having a second transport unit that transports the recording material in the second transport path,
First driving means for rotationally driving the first conveying means and the second conveying means;
The first state in which the first driving means transmits a driving force to the first conveying means, and the first driving means transmits the driving force to the first conveying means and the second conveying means. Switching means for switching the second state to be
Control means for controlling the first drive means and the switching means;
The control unit rotates the first driving unit at a first rotation speed when the recording material is conveyed at the predetermined speed by the first conveying unit, and the predetermined conveying unit rotates the first driving unit. When the recording material is conveyed at a speed slower than the first speed, the first driving means is rotated at a second rotational speed that is slower than the first rotational speed, and the first driving means is moved by the switching means. An image forming apparatus, wherein the first driving unit is controlled to rotate at the second rotation speed before the timing of switching from the first state to the second state. Storage means for storing the recording material;
Transfer means for transferring an image to the recording material;
A first transport path for transporting the recording material from the storage means to the transfer means;
A second transport path different from the first transport path for transporting the recording material;
First conveying means for conveying the recording material in the first conveying path, wherein the recording material is conveyed to the transfer means at a predetermined speed;
In the image forming apparatus having a second transport unit that transports the recording material in the second transport path,
First driving means for rotationally driving the first conveying means and the second conveying means;
The first state in which the first driving means transmits a driving force to the first conveying means, and the first driving means transmits the driving force to the first conveying means and the second conveying means. Switching means for switching the second state to be
Control means for controlling the first drive means and the switching means;
The control unit rotates the first driving unit at a first rotation speed when the recording material is conveyed at the predetermined speed by the first conveying unit, and the predetermined conveying unit rotates the first driving unit. When the recording material is transported at a speed higher than the first speed, the first driving means is rotated at a third rotational speed that is faster than the first rotational speed, and the first driving means is rotated at the third rotational speed. An image forming apparatus, wherein a period of rotation at a speed and a timing at which the first driving unit is switched from the first state to the second state by the switching unit are controlled so as not to overlap. Third conveying means for conveying the recording material from the first conveying path to the second conveying path;
Having second driving means for rotationally driving the third transport means;
The control means has a period during which the first driving means is rotated at the third rotational speed and a timing at which the switching means switches the first driving means from the first state to the second state. The image forming apparatus according to claim 2, wherein the second driving unit is controlled so as not to overlap.   4. The image according to claim 3, wherein the control unit controls a rotation speed of the second driving unit, and decelerates or stops a speed at which the third conveyance unit conveys the recording material. 5. Forming equipment.   The image forming apparatus according to claim 3, wherein the control unit controls a rotation speed of the second driving unit and accelerates a speed at which the recording material is conveyed by the third conveying unit. Having first detection means for detecting the recording material at a predetermined position in the first transport path;
After the rear end of the first recording material conveyed by the first conveying means reaches the predetermined position, the second recording material is conveyed by the first conveying means next to the first recording material. When the time until the leading edge of the recording material reaches the predetermined position is measured, and the measured time is longer than a preset time, the control means in the section from the predetermined position to the transfer position The image forming apparatus according to claim 1, wherein the second recording material is transported at a speed faster than the predetermined speed.   7. The control unit according to claim 6, wherein the control unit returns the conveyance speed of the second recording material to the predetermined speed before the leading edge of the second recording material reaches the transfer position. Image forming apparatus. Having a second detection means for detecting the recording material conveyed to the second conveyance path;
The timing at which the switching means switches the first driving means from the first state to the second state is determined based on the timing at which the second detection means detects the recording material. The image forming apparatus according to any one of claims 1 to 7.   9. The transport path according to claim 1, wherein the second transport path is a transport path that reverses the recording material on which an image has been transferred by the transfer unit and transports the recording material to the transfer unit again. The image forming apparatus described in 1.