JP2018161003A - Driving device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device having both an excellent acceleration performance of a driving shaft and a reduced power consumption.SOLUTION: A driving device 200 has a first power transmission portion 230 transmitting power of a stepping motor 210 to a driving shaft a71, the first power transmission portion 230 capable of switching between a connection state and a release state, a second power transmission portion 240 transmitting power of a brushless motor 220 to the driving shaft a71, and a control portion. At a first operation phase accelerating a rotation of the driving shaft up to a predetermined speed, the control portion transmits power of both the stepping motor 210 and the brushless motor 220 to drive the driving shaft a71, and at a second operation phase rotating the driving shaft a71 at a constant and predetermined speed after the first operation phase, releases transmission of the power of the stepping motor 210 by the first power transmission portion 230 to drive the driving shaft a71 only by the brushless motor 220.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a drive device and an image forming apparatus.

  In an image forming apparatus such as an electrophotographic printer, a transport roller for transporting paper is driven by a stepping motor. According to the stepping motor, accurate speed / position control can be performed with a simple control configuration.

  By the way, in recent years, with an increase in the speed of the image forming apparatus, it is required to shorten the acceleration time of the transport roller and to increase the target speed. However, the general-purpose stepping motor used in the image forming apparatus lacks output torque, so that step-out occurs and the conveying roller cannot be accelerated in a short time. Further, when an expensive stepping motor with high torque is used, it is necessary to constantly pass an excessive current in order to secure a torque margin, and there is a problem that power consumption increases.

  In relation to this, the following Patent Document 1 discloses that the output of a brushless motor is coupled to the output of a stepping motor at the time of startup, and torque is generated in the drive train on the stepping motor side by the brushless motor. At times, a technique of driving by a stepping motor is disclosed.

JP 2006-017988 A

  However, although the output torque is improved in the above technique, there is a problem in that the controllability is not sufficient because the output of the brushless motor can be simply coupled to the output of the stepping motor via the one-way mechanism. In addition, no consideration is given to reducing power consumption.

  The present invention has been made in view of the above-described problems. Accordingly, an object of the present invention is to provide a drive device and an image forming apparatus that have both good acceleration at start-up when driving a drive shaft such as a conveyance roller and reduction of power consumption.

  The above object of the present invention is achieved by the following means.

(1) Stepping motor,
A brushless motor,
A first power transmission unit for transmitting the power of the stepping motor to the drive shaft, the first power transmission unit being switchable between a connected state for transmitting power to the drive shaft and a release state for releasing the transmission;
A second power transmission unit for transmitting the power of the brushless motor to the drive shaft;
A control unit that controls the stepping motor, the brushless motor, and the first power transmission unit, and controls transmission of power to the drive shaft,
In the first operation phase of accelerating the rotation of the drive shaft to a predetermined speed, the control unit transmits the power of both the stepping motor and the brushless motor to drive the drive shaft,
After the first operation phase, in the second operation phase in which the drive shaft is rotated at a constant speed at the predetermined speed, the transmission of the power of the stepping motor by the first power transmission unit is released, and the brushless motor alone A drive device that drives a drive shaft.

  (2) In the third operation phase for decelerating the rotation of the drive shaft, the control unit maintains a released state of power transmission of the stepping motor, and decelerates and stops by controlling the brushless motor. The drive device according to (1) above.

(3) The second power transmission unit can be switched between a connected state in which the power of the brushless motor is transmitted to the drive shaft and a released state in which the transmission is released.
In the third operation phase in which the rotation of the drive shaft is decelerated, the control unit switches the transmission of the power of the stepping motor to a connected state and starts the transmission of the power of the brushless motor to a released state before starting deceleration. Then, the driving device according to (1), wherein the stepping motor is decelerated and stopped by controlling the stepping motor.

  (4) The first power transmission unit includes a gear movement mechanism that moves at least one of a plurality of gears constituting a gear train that transmits the power of the stepping motor to the clutch or the stepping motor. Then, the transmission of the power of the stepping motor to the drive shaft is switched to the connected state or the released state by the clutch or the gear moving mechanism from any one of (1) to (3). The drive device described.

  (5) The second power transmission unit has a gear moving mechanism that moves at least one of a plurality of gears constituting a gear train that transmits the power of the stepping motor to the clutch or the stepping motor. The drive device according to (3), wherein the transmission of the power of the brushless motor to the drive shaft is switched to the connected state or the released state by the clutch or the gear moving mechanism.

(6) In the first operation phase, the control unit
After setting the current value of the stepping motor in the stopped state to the holding current value and generating the holding torque to the stepping motor, the control value of the brushless motor is set to a predetermined value and the holding value to the brushless motor is set. Generate torque smaller than torque,
Thereafter, the stepping motor is accelerated according to a predetermined acceleration curve, and the control value of the brushless motor is maintained constant, or the control value is increased according to the rotational speed of the stepping motor. The drive device according to any one of (5) above.

  (7) An image forming apparatus having the driving device according to any one of (1) to (6).

  (8) The image forming apparatus according to (7), wherein the drive shaft is a drive shaft of a transport roller for transporting a sheet or a drive shaft for driving a pressure-separation / separation mechanism of the transport roller.

  According to the present invention, since the drive shaft is driven using the power of the stepping motor and the brushless motor at the time of start-up, the output torque is improved and the drive shaft can be accelerated in a short time. In addition, during constant speed rotation after acceleration, the drive transmission of the stepping motor is canceled and the drive shaft is rotated only by the brushless motor. As a result, it is possible to reduce power consumption during constant speed rotation.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a schematic diagram which shows schematic structure of the drive device which concerns on 1st Embodiment. It is a block diagram which shows the control system of a drive device. It is a flowchart which shows the procedure of the drive control performed by a control part. It is a figure which shows the subroutine of step S101 of FIG. It is a timing chart for demonstrating operation | movement of a stepping motor and a brushless motor. It is a timing chart for demonstrating operation | movement of the stepping motor and brushless motor in a 1st operation | movement phase. It is a schematic diagram which shows schematic structure of the drive device which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the drive control in 2nd Embodiment. It is a timing chart for demonstrating operation | movement of a stepping motor and a brushless motor. It is a schematic diagram which shows schematic structure of the drive device which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention. As illustrated in FIG. 1, the image forming apparatus 100 includes a control unit 110, a storage unit 120, an image reading unit 130, an image forming unit 140, a fixing unit 150, a paper feeding unit 160, and a paper transporting unit 170.

  The control unit 110 is a CPU (Central Processing Unit), and controls the above-described units and performs various arithmetic processes according to a program.

  The storage unit 120 stores a ROM (Read Only Memory) that stores various programs and various data in advance, a RAM (Random Access Memory) that temporarily stores programs and data as a work area, and stores various programs and various data. It consists of a hard disk.

  The image reading unit 130 includes a light source such as a fluorescent lamp and an image sensor such as a CCD (Charge Coupled Device) image sensor. The image reading unit 130 applies light from a light source to a document set at a predetermined reading position, photoelectrically converts the reflected light with an image sensor, and generates image data from the electric signal.

  The image forming unit 140 includes developing units 141Y to 141K corresponding to toners of respective colors of Y (yellow), M (magenta), C (cyan), and K (black). The toner images formed through the charging, exposure, and development processes by the developing units 141 </ b> Y to 141 </ b> K are sequentially superimposed on the intermediate transfer belt 142 and transferred onto the paper S by the secondary transfer roller 143.

  The fixing unit 150 includes a heating roller and a pressure roller. The fixing unit 150 heats and presses the sheet S conveyed to the fixing nip of both rollers, and melts and fixes the toner image on the sheet S on the surface thereof.

  The paper feed unit 160 includes a plurality of paper feed trays 161 and 162, and sends out the sheets S stored in the paper feed trays 161 and 162 one by one to the downstream conveyance path.

  The paper transport unit 170 includes a plurality of transport rollers 171 for transporting the paper S, and transports the paper S between the image forming unit 140, the fixing unit 150, and the paper feed unit 160. All or some of the plurality of transport rollers 171 are driven by the driving device 200 (see FIG. 2).

  Note that the image forming apparatus 100 may include components other than the above-described components, or some of the above-described components may not be included.

  Next, with reference to FIG. 2 and FIG. 3, the drive device 200 which drives the conveyance roller 171 will be described.

  FIG. 2 is a schematic diagram illustrating a schematic configuration of the driving device 200, and FIG. 3 is a block diagram illustrating a control system of the driving device 200.

  FIGS. 2A and 2B are diagrams showing the driving device 200 in a connected state and a released state, respectively. As shown in FIG. 2, the drive device 200 transmits power to the drive shaft a <b> 71 to which the transport roller 171 to be operated is fixed, and rotates the drive shaft a <b> 71. The driving device 200 includes a stepping motor 210, a brushless motor 220, a first power transmission unit 230, and a second power transmission unit 240. The stepping motor 210 and the brushless motor 220 are provided with rotation axes a1 and a2, respectively.

  The first power transmission unit 230 transmits the power of the stepping motor 210 to the drive shaft a71, and the second power transmission unit 240 transmits the power of the brushless motor 220 to the same drive shaft a71.

  The first power transmission unit 230 includes gears 231, 232, 233, 234, a rotation shaft a 3, and a gear movement mechanism 235. The most upstream gear 231 of the gear train is provided on the rotation shaft a1 of the stepping motor 210, and the most downstream gear 234 is fixedly provided on one end side of the drive shaft a71. In the coupled state shown in FIG. 2A, the first power transmission unit 230 transmits the power of the stepping motor 210 to the drive shaft a71 in the order of the gear 231, the gear 232, the rotation shaft a3, the gear 233, and the gear 234. .

  The gear moving mechanism 235 includes a cam, a drive source for moving the cam, and the like (both not shown), functions as a connection release mechanism, and includes a rotation shaft a3 and gears 232 and 233 fixed thereto. Move in the direction away from the other gear or in the opposite direction. FIG. 2B shows the release state. In this released state, the gear train of the first power transmission unit 230 is released by the gear moving mechanism 235.

  The second power transmission unit 240 includes a gear 241 fixed to the other end of the drive shaft a71. The rotation shaft a <b> 2 of the brushless motor 220 is provided with teeth, and the rotation shaft a <b> 2 of the brushless motor 220 is engaged with the gear 241. The power of the brushless motor 220 is transmitted to the drive shaft a71 via the gear 241 as the second power transmission unit 240.

  As illustrated in FIG. 3, the control unit 110 of the image forming apparatus 100 controls operations of the stepping motor 210, the brushless motor 220, and the gear moving mechanism 235 (and a gear moving mechanism 245 described later).

  The controller 110 drives the stepping motor 210 by open loop control. The control unit 110 controls the rotational speed of the stepping motor 210 by sending a clock signal (CLK) to the driver 211 for the stepping motor 210 and setting the operating frequency of the stepping motor 210. Further, the control unit 110 controls the torque generated in the stepping motor 210 by transmitting a setting current signal to the driver 211 for the stepping motor 210 and setting the current value of the stepping motor 210.

  Further, the control unit 110 drives the brushless motor 220 by PWM (Pulse Width Modulation) control. The control unit 110 controls the rotational speed and torque of the brushless motor 220 by sending a PWM signal to the built-in driver 221 of the brushless motor 220 and setting a control value (duty command value) of the brushless motor 220. Further, the control unit 110 receives the rotation speed signal from the built-in encoder 222 of the brushless motor 220, thereby executing speed feedback control of the brushless motor 220.

(Drive control)
Next, with reference to FIG. 4 and FIG. 5, the drive control of the drive device 200 that drives the transport roller 171 according to the first embodiment will be described.

  FIG. 4 is a flowchart illustrating a drive control procedure executed by the control unit 110. This drive control is started, for example, when the image forming apparatus 100 receives a print job. In the drive control, the drive shaft a71 of the transport roller 171 that is stopped is accelerated to a predetermined speed (target speed) according to a predetermined acceleration curve, rotated at a constant speed at the target speed, and then decelerated according to a predetermined deceleration curve. Note that the algorithm shown in the flowcharts of FIGS. 4 and 5 is stored as a program in the storage unit 120 and executed by the control unit 110.

  First, the control unit 110 starts driving the same drive shaft a71 by both the stepping motor 210 and the brushless motor 220 (S101 (first operation phase)). In step S101, the control unit 110 gradually increases the operating frequency of the stepping motor 210 so that the rotation speed increases according to a predetermined acceleration curve by the following control.

(Subroutine of step S101)
FIG. 5 is a diagram showing a subroutine of step S101. As an initial process, the control unit 110 sets the current value of the stepping motor 210 to the holding current value (S201). More specifically, the control unit 110 sets the current value of the stepping motor 210 to the holding current value, and causes the stepping motor 210 in the stopped state to generate a holding torque.

  Next, the control unit 110 sets the control value of the brushless motor 220 to a predetermined value (S202). More specifically, the control unit 110 sets the duty command value of the brushless motor 220 to a predetermined value, and causes the brushless motor 220 to generate a torque smaller than the holding torque of the stepping motor 210.

  Next, the controller 110 accelerates the stepping motor 210 (S203). More specifically, the controller 110 gradually increases the operating frequency of the stepping motor 210 so that the rotation speed increases according to a predetermined acceleration curve.

  The controller 110 increases the control value of the brushless motor 220 (S204). More specifically, the control unit 110 increases the duty command value set in the process shown in step S102 in accordance with an increase in the rotation speed of the stepping motor 210. Then, the processing returns to the processing of FIG. 4 while continuing the processing of steps S203 and S204 (return).

  Returning to the description of FIG. The controller 110 determines whether or not the rotational speed of the drive shaft a71 has reached the target speed (S102). This determination is made, for example, by comparing the command operating frequency for the stepping motor 210 with a target value. When determining that the stepping motor 210 has not reached the target speed (S102: NO), the control unit 110 waits until the stepping motor 210 reaches the target speed.

  When it is determined that the stepping motor 210 has reached the target speed (S102: YES), the control unit 110 executes speed feedback control of the brushless motor 220 (S103 (second operation phase)). More specifically, the control unit 110 performs speed feedback control that maintains the rotational speed of the brushless motor 220 at the target speed.

  Next, the control unit 110 operates the gear moving mechanism 235 to switch the first power transmission unit 230 to the released state (see FIG. 2B), and releases the connection between the stepping motor 210 and the drive shaft a71 (S104). .

  Thereafter, the control unit 110 turns off and stops the power of the stepping motor 210 that has been disconnected (S105).

  Next, the control unit 110 determines whether or not the conveyance of all the sheets S of the print job has been completed (S106). When it is determined that the conveyance has not ended (S106: NO), the control unit 110 waits until the conveyance is completed. That is, the steady state in which the drive shaft a71 is rotated at the target speed only by the brushless motor 220 is maintained.

  On the other hand, when it is determined that the conveyance is finished (S106: YES), the control unit 110 decelerates and stops the brushless motor 220 (S107). More specifically, the control unit 110 gradually changes the control value of the brushless motor 220.

  As described above, in the drive control described with reference to FIG. 4 and the like, in the first operation phase (S101) in which the drive shaft a71 in the stopped state is accelerated to the constant speed rotation, the power of both the stepping motor 210 and the brushless motor 220 is used. Then, the rotation of the drive shaft a71 is accelerated, and in the subsequent second operation phase (S103 to S105), the transmission of the power of the stepping motor 210 by the first power transmission unit 230 is released, and the drive shaft a71 is moved only by the brushless motor 220. To drive. Hereinafter, drive control will be described in more detail with reference to FIGS.

  6 and 7 are timing charts for explaining operations of the stepping motor 210 and the brushless motor 220. FIG. FIG. 6 corresponds to the flowchart of FIG. 4, and FIG. 7 corresponds to the subroutine of FIG. 5 relating to the first operation phase. First, the overall drive control will be described with reference to FIG. FIG. 6A shows a temporal change in the rotational speed of the drive shaft a71. FIGS. 6B and 6C show temporal changes in the rotational speeds of the stepping motor 210 and the brushless motor 220, respectively. In FIG. 6B, the period during which the stepping motor 210 is connected to the drive shaft a71 is indicated by a solid line, and the period during which the gear moving mechanism 235 is released to release the connection is indicated by a broken line (hereinafter referred to as a broken line). The same applies to FIG.

(First operation phase)
In the first operation phase from time t10 to t20, the rotation of the drive shaft a71 is accelerated. During this period, both the stepping motor 210 and the brushless motor 220 drive the drive shaft a71, and both are accelerating at the same inclination so as to have substantially the same rotational speed on the drive shaft a71.

(Second operation phase)
Time t20 is timing when the target speed is reached. As shown in FIG. 6B, in response to reaching the target speed, the connection of the first power transmission unit 230 starts to be switched to the released state. Thereafter, after the release of the connection is completed (time t30), the rotation speed of the stepping motor 210 starts to be reduced and stopped (time t40). Here, the time required for starting from the stop to the target speed (time t10 to t20) is, for example, 50 msec, and the time required from completion of connection release to completion (time t20 to t30) is, for example, 10 msec.

  On the other hand, as shown in FIG. 6C, the brushless motor 220 maintains a constant rotational speed after time t20.

(Third operation phase)
When the conveyance of the sheet is completed (time t50), the control unit 110 starts decelerating the brushless motor 220 and stops the rotation (time t60).

  Next, the first operation phase will be described in more detail with reference to FIG. FIG. 7A is a partially enlarged view up to time t20 in FIG. 6B, and shows a change over time in the rotation speed of the stepping motor 210. FIG. FIG. 7B shows a change over time of the current value of the stepping motor 210. FIG. 7C shows a change over time in the control value of the brushless motor 220. FIG. 7D shows the time change of the torque generated in the stepping motor 210. FIG. 7E shows a change over time in the torque generated in the brushless motor 220.

  At the start of acceleration of the stepping motor 210, the current value of the stepping motor 210 in the stopped state is first set to the holding current value (time t1 in FIG. 7B), and the holding torque is generated in the stepping motor 210 (FIG. 7 ( d) time t1). In the first operation phase in which the holding torque is generated in the stepping motor 210, the control value (duty command value) of the brushless motor 220 is set to a predetermined value (time t2 in FIG. 7C). As a result, a torque smaller than the holding torque is generated in the brushless motor 220 (time t2 in FIG. 7E). This holding torque is maintained for a very short time (time t2 to t20).

  Thereafter, the stepping motor 210 is accelerated according to a predetermined acceleration curve (time t10 to t20 in FIG. 7A). During the period in which the stepping motor 210 is accelerated, the control value of the brushless motor 220 is also increased according to the rotation speed of the stepping motor 210 (time t10 to t20 in FIG. 7C).

  As described above, in the present embodiment, in the first operation phase in which the rotation of the drive shaft a71 is accelerated, the drive shaft a71 is driven using the power of both the stepping motor and the brushless motor, so that the output torque is improved. The drive shaft a71 can be accelerated in a short time stably.

  In particular, in the present embodiment shown in FIG. 7, the stepping motor 210 generates a holding torque, and the torque is applied from the brushless motor 220 to the stepping motor 210 stopped in a state where the holding torque is generated (time t2 to t10). More specifically, the torque from the brushless motor 220 is applied to the drive shaft a71 fixed by the holding torque of the stepping motor 210. If the acceleration of the stepping motor 210 is started in this state, the operation of the stepping motor 210 is assisted by the torque of the brushless motor 220, so that the drive shaft a71 can be accurately accelerated in a short time according to a predetermined acceleration curve. Unlike the present embodiment described with reference to FIG. 7, when the brushless motor 220 is driven to generate torque after the acceleration of the stepping motor 210 or at the same time as the acceleration starts, the load on the stepping motor 210 fluctuates greatly and is removed. In this embodiment, such a problem is prevented in advance.

  Further, in the present embodiment, in the second operation phase rotating at a constant speed, the transmission of the power of the stepping motor 210 by the first power transmission unit 230 to the drive shaft a71 is released, and the drive shaft a71 is moved only by the brushless motor 220. Driven. Thereby, the power consumption at the time of constant speed rotation can be suppressed. This is because when the constant speed rotation is simply maintained, it is more efficient to use the brushless motor 220 than the stepping motor 210 because power consumption can be reduced. Unlike this embodiment, if the power of the stepping motor is turned off while the stepping motor is connected, the load may increase, which may cause an increase in power consumption or a step-out. In the embodiment, such a problem is prevented in advance.

(Driver according to Second Embodiment)
In 1st Embodiment, the example which provided the connection cancellation | release mechanism in the 1st power transmission part 230 was shown. In the second embodiment, in addition to the first power transmission unit 230, the second power transmission unit 240 is also provided with a connection release mechanism. In the following, portions different from the first embodiment will be mainly described, and description of the same configuration will be omitted.

  FIG. 8 is a schematic diagram illustrating a schematic configuration of the driving apparatus according to the second embodiment. The second power transmission unit 240 of the drive device 200 according to the second embodiment includes gears 241, 242, 243, a rotation shaft a4, and a gear moving mechanism 245. The most upstream gear 242 in the gear train meshes with the teeth of the rotation shaft a <b> 2 of the brushless motor 220. The most downstream gear 241 is fixed to the drive shaft a71. In the coupled state shown in FIG. 8A (or FIG. 8B), the second power transmission unit 240 drives the power of the brushless motor 220 in the order of the gear 242, the rotation shaft a4, the gear 243, and the gear 241. It is transmitted to the axis a71.

  The gear moving mechanism 245 has the same configuration as the gear moving mechanism 235 of the first power transmission unit 230. That is, the gear moving mechanism 245 includes a cam, a drive source for moving the cam, and the like (both not shown), functions as a connection release mechanism, and has a rotating shaft a4 and gears 232, 233 fixed thereto. Is moved away from other gears or in the opposite direction. FIG. 8C shows the release state. In this released state, the gear train of the second power transmission unit 240 is released by the gear movement mechanism 245.

(Drive control in the second embodiment)
Next, with reference to FIGS. 9 and 10, drive control of the drive device that drives the transport roller 171 according to the second embodiment will be described.

  FIG. 9 is a flowchart showing a drive control procedure in the second embodiment executed by the control unit 110. FIG. 10 is a timing chart for explaining the operation of the stepping motor and the brushless motor in the second embodiment.

  In the second embodiment, processing in the first operation phase in which the rotation of the drive shaft a71 is accelerated and the second operation phase in the subsequent constant speed rotation are the same as those in the first embodiment shown in FIGS. Only the third operating phase that follows the second operating phase is different. Therefore, FIG. 9 shows only the process of the third operation phase performed after step S106. The timing chart of FIG. 10 is the same as that of FIG. 6 until the second operation phase (time t0 to t40), and here, the processing after the third operation phase (time t42 to t60) will be described. The algorithm shown in the flowchart of FIG. 9 is stored as a program in the storage unit 120 and executed by the control unit 110.

  First, when the control unit 110 determines that the conveyance of the sheet S has been completed (S106: YES), the control unit 110 immediately starts to rotate the stepping motor 210 that has stopped (time t42), and accelerates to the target speed (S301). . At this time, the first power transmission unit 230 is in a released state (see FIG. 8B), and the stepping motor 210 is not connected to the drive shaft a71 and is not loaded. The acceleration curve at this time may be set to be the same as the acceleration during the period t10 to t20, but since no load is applied, the acceleration curve is compared with the acceleration at the time t10 to t20 so as to reach the target speed earlier. It may be steep.

  When the rotational speed of the stepping motor 210 reaches the target speed, the control unit 110 operates the gear moving mechanism 235 to switch the first power transmission unit 230 to the connected state (see FIG. 8A), and the stepping motor. 210 and the drive shaft a71 are connected (S302, time t50).

  Next, the control unit 110 operates the gear moving mechanism 245 to switch the second power transmission unit 240 to the released state (see FIG. 8C), and releases the connection between the brushless motor 220 and the drive shaft a71 ( S303, time t50).

  Thereafter, the control unit 110 turns off and stops the power of the brushless motor 220 (S304, after time t50).

  Further, the control unit 110 decelerates and stops the stepping motor 210 (S305, time t50 to t60). More specifically, the controller 110 gradually decreases the operating frequency of the stepping motor 210 so that the rotational speed decreases according to a predetermined deceleration curve.

  In the driving device 200 according to the second embodiment, in the third operation phase, the power transmission of the stepping motor 210 is switched from the released state to the connected state, and the power transmission of the brushless motor 220 is switched from the connected state to the released state. ing. Thereafter, the stepping motor is controlled to decelerate and stop. In this way, in the second embodiment, the same effect as in the first embodiment can be obtained, and furthermore, the stop amount is controlled by the stepping motor 210 at the time of stop, so that the braking amount (up to stop) ( The amount of rotation) can be controlled with high accuracy. The transport roller 171 that transports the sheet is particularly useful because it requires high-precision control of the stop position.

(Modification)
In the embodiment described above, the example using the gear moving mechanisms 235 and 245 has been described as the connection release mechanism for connecting and releasing the power transmission to the drive shaft a71 of each motor, but is not limited thereto. FIG. 11 shows another example in which a clutch is used as a connection release mechanism. In the drive device 200 according to the modification shown in FIG. 11A, the first power transmission unit 230 includes a clutch 239. The clutch 239 is constituted by, for example, an electromagnetic clutch, is provided with a gear 234, and is attached to one end side of the drive shaft a71. The clutch 239 cuts off or connects the power transmission to the drive shaft a71 of the stepping motor 210. Thereby, the 1st power transmission part 230 is switched to a connection state or a cancellation | release state.

  FIG. 11B is an example in which the second power transmission unit 240 is further provided with a clutch 249. Similarly, the clutch 249 provided with the gear 241 is attached to the other end portion side of the drive shaft a71, and cuts off or connects power transmission to the drive shaft a71 of the brushless motor 220. Thereby, the 2nd power transmission part 240 is switched to a connection state or a cancellation | release state.

  Even if a clutch is used as the connection release mechanism as in this modification, the same effects as those of the first and second embodiments described above can be obtained.

(Other variations)
In the flowcharts described with reference to FIGS. 4, 5, and 8, they may be executed in an order different from the order shown in these figures. Accordingly, this embodiment is not to be considered as limited to the specific steps shown in these figures. For example, steps S103 to S105, or S302 and S303 may be executed in parallel at the same time. Further, the present invention is not limited to the subroutine of step S101 in FIG. 5, and the acceleration may be simply started at a predetermined acceleration at the same time by a brushless motor and a stepping motor at another operation timing.

  Further, in the above-described embodiment, the case where the driving device 200 of the present invention is applied to the image forming apparatus 100 and the conveyance roller 171 inside the image forming apparatus 100 is driven has been described as an example. However, the driving device 200 of the present invention may be applied to a post-processing device connected to the image forming apparatus, and may drive a conveyance roller inside the post-processing device.

  In the above-described embodiment, the case where the drive shaft 200 of the transport roller 171 is driven by the drive device 200 of the present invention has been described as an example. However, the drive shaft driven by the drive device 200 of the present invention is not limited to the drive shaft a71 of the transport roller 171. The drive device 200 of the present invention can also be used to drive a drive shaft for driving the pressure-bonding / separating mechanism of the transport roller 171. In this case, for example, a cam is attached to the drive shaft, and the rotation operation of the drive shaft is converted into a translation operation by the cam.

  The means and method for performing various processes in the image forming apparatus according to the above-described embodiments can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. The program may be provided as a single application software, or may be incorporated in the software of the apparatus as a function of the image forming apparatus.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 110 Control part 120 Memory | storage part 130 Image reading part 140 Image forming part 150 Fixing part 160 Paper feeding part 170 Paper conveyance part 171 Conveyance roller a71 Drive shaft 200 Driving device 210 Stepping motor 220 Brushless motor 230 1st power transmission part 231, 232, 233, 234 Gear 235 Gear moving mechanism 239 Clutch 240 Second power transmission unit 241, 242, 243 Gear a2, a2, a3 Rotating shaft 245 Gear moving mechanism 249 Clutch

Claims (8)

Stepper motor,
A brushless motor,
A first power transmission unit for transmitting the power of the stepping motor to the drive shaft, the first power transmission unit being switchable between a connected state for transmitting power to the drive shaft and a release state for releasing the transmission;
A second power transmission unit for transmitting the power of the brushless motor to the drive shaft;
A control unit that controls the stepping motor, the brushless motor, and the first power transmission unit, and controls transmission of power to the drive shaft,
In the first operation phase of accelerating the rotation of the drive shaft to a predetermined speed, the control unit transmits the power of both the stepping motor and the brushless motor to drive the drive shaft,
After the first operation phase, in the second operation phase in which the drive shaft is rotated at a constant speed at the predetermined speed, the transmission of the power of the stepping motor by the first power transmission unit is released, and the brushless motor alone A drive device that drives a drive shaft.   The control unit maintains a released state of power transmission of the stepping motor in a third operation phase in which the rotation of the drive shaft is decelerated, and decelerates and stops by controlling the brushless motor. The drive device described in 1. The second power transmission unit can be switched between a connected state in which the power of the brushless motor is transmitted to the drive shaft and a released state in which the transmission is released.
In the third operation phase in which the rotation of the drive shaft is decelerated, the control unit switches the transmission of the power of the stepping motor to a connected state and starts the transmission of the power of the brushless motor to a released state before starting deceleration. Then, the drive device according to claim 1, wherein the drive device is decelerated and stopped by controlling the stepping motor.   The first power transmission unit has a gear moving mechanism that moves at least one of a plurality of gears constituting a gear train that transmits power of the stepping motor to the clutch or the stepping motor, The drive device according to any one of claims 1 to 3, wherein transmission of power of the stepping motor to the drive shaft is switched to the connected state or the released state by a clutch or the gear moving mechanism.   The second power transmission unit has a gear moving mechanism that moves at least one of a plurality of gears constituting a gear train that transmits the power of the stepping motor to the clutch or the stepping motor, The drive device according to claim 3, wherein transmission of power of the brushless motor to the drive shaft is switched to the connected state or the released state by a clutch or the gear moving mechanism. The control unit, in the first operation phase,
After setting the current value of the stepping motor in the stopped state to the holding current value and generating the holding torque to the stepping motor, the control value of the brushless motor is set to a predetermined value and the holding value to the brushless motor is set. A torque smaller than the torque is generated, and then the stepping motor is accelerated according to a predetermined acceleration curve, and the control value of the brushless motor is maintained constant, or the control value depends on the rotation speed of the stepping motor The drive device according to any one of claims 1 to 5, wherein the drive device increases.   An image forming apparatus comprising the driving device according to claim 1.   The image forming apparatus according to claim 7, wherein the drive shaft is a drive shaft of a transport roller for transporting a sheet or a drive shaft for driving a press-separation / separation mechanism of the transport roller.