JP6314716B2 - Image forming apparatus and method for driving paper conveying motor - Google Patents

Description

  According to the present invention, two motors for paper conveyance are connected to a common rotational load via a one-way clutch, and load torque applied to the motor is distributed to compensate for a shortage of torque in a single motor. The present invention relates to an image forming apparatus and a method for driving a sheet conveying motor in the apparatus.

  As an image forming apparatus in which two motors for paper conveyance are connected to a common rotational load, Patent Document 1 discloses that a first motor and a second motor are respectively connected to a common rotational load via a one-way clutch. When the rotational load is started, a driving method that prevents the overload of the first motor by first driving the rotary load shaft at a low speed and then driving the first motor at a high speed. It is disclosed.

Further, Patent Document 2 discloses a driving method in which a rotational fluctuation generated in one of two rotational loads is always synchronized with the rotational load.
Are known.

JP-A-63-214554 JP-A-9-47086

  By the way, when developing a product that covers a low-cost image forming apparatus used in an office or the like up to the production print area, it is necessary to increase the system speed to cope with the increase in speed. For that purpose, the drive motor for the transport roller must be driven at high speed and the required torque must be secured, but it is necessary to perform high speed rotation under driving conditions that the required torque cannot be produced with a single motor. Has occurred.

  However, the technique described in Patent Document 1 described above prevents inability to drive or breakage due to insufficient torque at startup, and does not compensate for insufficient load torque during constant speed rotation.

  Further, the technique described in Patent Document 2 drives the rotational load with only the first motor during a steady load, and compensates for a shortage of torque due to a sudden load such as when a sheet is passing. It does not compensate for the lack of torque in the event of overload.

  In this invention, two motors for paper conveyance are connected to a common rotational load via a one-way clutch, and the load torque applied to the motor is distributed to compensate for a shortage of torque in a single motor. It is an object of the present invention to provide an image forming apparatus capable of rotating a conveyance roller at a high speed while ensuring a sufficient torque, and a method of driving a sheet conveyance motor in the apparatus.

The above problem is solved by the following means.
(1) a first motor that drives a first transport roller that transports a sheet via a first one-way clutch, and a second motor that drives a second transport roller different from the first transport roller. A second motor capable of driving the first transport roller via a second one-way clutch, and simultaneously driving the first transport roller by the second motor when the first transport roller is driven by the first motor. Speed control means for controlling the first motor at a constant speed to rotate the first transport roller at a target speed when driving, and torque detection means for detecting load torque of the first motor and the second motor And, based on the detection results of the load torque of the first motor and the second motor by the torque detection means, the load torque ratio of the first motor and the second motor is set to a target value. An image forming apparatus comprising: the torque control means for controlling the load torque, the.
(2) A third one-way clutch disposed between the second motor and the second transport roller, and speed control means for controlling the second motor at a constant speed, wherein the second motor During the forward rotation, a constant speed control is performed to drive the second transport roller via the third one-way clutch, and during the reverse rotation, the second transport roller is coupled to the first transport roller and the first motor together with the first motor. 2. The image forming apparatus according to item 1, wherein the conveying roller is driven.
(3) The image forming apparatus according to (1) or (2), wherein the detection of the load torque by the torque detection unit is performed by detecting currents of the first motor and the second motor.
(4) The first transport roller is provided in a first transport path for transporting paper fed from the first paper feed cassette, and the second transport roller transports paper fed from the second paper feed cassette. The preceding items 1 to 5 are provided in a second transport path different from the first transport path, and the first transport roller is simultaneously driven by the second motor when the first transport roller is driven by the first motor. The image forming apparatus according to claim 3.
(5) A paper feed motor that feeds the paper fed from the first paper feed cassette is provided, and the second transport roller is driven by the paper feed motor when the second transport roller is driven by the second motor. The speed control means controls the second motor at a constant speed to rotate the second transport roller at a target speed, and the torque control means controls the second motor and the paper feed motor. 5. The image forming apparatus according to any one of items 1 to 4, wherein the load torque of the sheet feeding motor is controlled so that the load torque ratio becomes a target value.
(6) The target value of the load torque ratio between the first motor and the second motor is set in any one of the preceding items 1 to 5, which is set so that the load torque of the two motors is smaller than the torque generated by each motor. Image forming apparatus.
(7) The image forming apparatus according to any one of the preceding items 1 to 6, wherein when the sheet conveyance speed is decreased according to the sheet type, the first conveyance roller is driven only by the first motor.
(8) If the first longitudinal conveying roller can be driven only by the first motor as a result of the detection of the load torque by the torque detecting means, the first item 1 in which the first conveying roller is driven only by the first motor. 8. The image forming apparatus according to any one of.
(9) The image according to any one of the preceding items 1 to 8, wherein the first transport roller is driven by the first motor and the second motor only when the first motor is started or when the sheet enters the first transport roller. Forming equipment.
(10) A step of driving a first transport roller for transporting a sheet by a first motor via a first one-way clutch, and at the time of driving the first transport roller by the first motor, A second motor for driving different second transport rollers, wherein the first transport roller is driven simultaneously by a second motor capable of driving the first transport roller via a second one-way clutch. A step of controlling the first motor at a constant speed to rotate the first transport roller at a target speed, a step of detecting load torques of the first motor and the second motor, the first motor and the second Controlling the load torque of the second motor so that the load torque ratio between the first motor and the second motor becomes a target value based on the detection result of the load torque of the motor. The driving method of the paper feeding motor in the image forming apparatus according to claim.

  According to the invention described in item (1), the first motor and the second motor are connected to the first conveying roller as the rotational load via the first and second one-way clutches, respectively. By controlling the speed and controlling the load torque of the second motor, the first motor and the second motor can drive the first conveying roller while distributing the load torque. Therefore, even when the necessary torque cannot be produced by the first motor alone, the second motor compensates for the torque shortage caused by the first motor, ensures sufficient torque, and rotates the first transport roller at high speed. Can do.

  In addition, since the existing second motor for driving the second conveying roller is used as a motor for controlling the load torque, it is not necessary to add a new motor, and the image forming apparatus is provided with a space-saving and low-cost drive coupling mechanism. It becomes.

  According to the invention described in item (2) above, the second motor links and drives the second conveying roller via the third one-way clutch by performing constant speed control during forward rotation, and the first motor during reverse rotation. The first conveying roller can be driven together with the first motor by being connected to the conveying roller.

  According to the invention described in item (3) above, the load torque can be reliably detected by detecting the currents of the first motor and the second motor.

  According to the invention described in (4) above, the motor that drives the second transport roller for transporting the paper fed from the second paper feed cassette is used as the second motor, and the first transport roller is the first transport roller. The first motor and the second motor can be driven simultaneously.

  According to the invention described in item (5), the second motor is controlled by controlling the speed of the second motor and controlling the load torque of the paper feed motor that feeds the paper fed from the first paper feed cassette. It becomes possible to drive by distributing the load torque. Accordingly, even when the necessary torque cannot be produced by the second motor alone, the shortage of torque by the second motor is compensated by the paper feed motor, and the second transport roller is driven to rotate at a high speed while ensuring sufficient torque. Can do.

  According to the invention described in the preceding item (6), the target value of the load torque ratio of the first motor and the second motor is set so that the load torque of the two motors is smaller than the torque generated by each motor. Torque shortage due to the first motor can be reliably compensated with the second motor.

  According to the invention described in the preceding item (7), when the sheet conveying speed is decreased according to the sheet type, the first conveying roller is driven only by the first motor, and therefore the second motor is wasted. Can be avoided.

  According to the invention described in item (8) above, when the first conveying roller can be driven only by the first motor as a result of the detection of the load torque, the first conveying roller is driven only by the first motor. Therefore, useless driving of the second motor can be avoided.

  According to the invention described in item (9), the first transport roller is driven by the first motor and the second motor only when the first motor is started or when the sheet enters the first transport roller.

  According to the invention described in the above item (10), even when the first motor alone cannot provide the necessary torque, the second motor compensates for the torque shortage caused by the first motor, and secures sufficient torque. One transport roller can be driven to rotate at high speed.

1 is a configuration diagram of a main part of a paper transport mechanism of an image forming apparatus according to an embodiment of the present invention. It is a graph which shows the torque and rotation speed of a brushless motor, and the relationship between a torque and an electric current. It is a block diagram which shows the structure of the control part in the case of speed-controlling a 1st motor and carrying out torque control of a 2nd motor. It is a figure for demonstrating the control which keeps the load torque of a 1st motor and a 2nd motor constant. 5 is a flowchart illustrating a motor drive control operation by the image forming apparatus. 6 is a flowchart illustrating a paper feed operation end process. It is a block diagram of the principal part of the paper conveyance mechanism of the image forming apparatus which concerns on other embodiment of this invention. It is explanatory drawing regarding the ratio of the load torque of a 1st motor and a 2nd motor. It is a flowchart which shows the process which determines whether a 1st conveyance roller drives only with a 1st motor, or drives with a 1st motor and a 2nd motor. 6 is a flowchart illustrating an operation of the image forming apparatus when the first conveyance roller is driven by the first motor and the second motor only when the sheet enters the first conveyance roller. 6 is a flowchart illustrating an operation of the image forming apparatus when the first conveyance roller is driven by the first motor and the second motor only when the first motor is activated.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a main part of a paper transport mechanism of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes two upper and lower paper feed cassettes (not shown), and transports paper fed from the upper one paper feed cassette by the pair of first paper feed rollers 101a and 101b in the horizontal direction. In addition, the paper fed by the pair of second paper feed rollers 112a and 112b from the first transport path 150 for transporting further vertically upward and the pair of second paper feed rollers 112a and 112b from the lower two-stage paper feed cassette is transported in the horizontal direction. And a second transport path 160 for transporting to the center.

  A pair of first transport rollers 102a and 102b for transporting the paper transported in the horizontal direction upward is provided downstream of the first paper feed rollers 101a and 101b in the first transport path 150. Third transport rollers 121a and 121b are provided downstream of the transport rollers 102a and 102b.

  Similarly, a pair of second transport rollers 113a and 113b for transporting the paper transported in the horizontal direction upward is provided downstream of the second paper feed rollers 112a and 112b in the second transport path 160. Yes. The second transport path 160 joins the first transport path 150 at a position downstream of the second transport rollers 113a and 113b and upstream of the first transport rollers 102a and 102b. The sheet transported upward in the second transport path 160 by the two transport rollers 113a and 113b is transported to the upper image forming unit by the first transport rollers 102a and 102b.

  One roller 101a of the pair of first paper feed rollers 101a and 101b is connected to a one-stage paper feed motor 109 made up of a brushless motor via two gears 111 and 110. With the rotation of 109, the first paper feed rollers 101a and 101b are driven to rotate via gears 111 and 110, so that the paper is drawn out from the first-stage paper feed cassette and supplied to the first transport path 150.

  A first gear 106 is engaged with one roller 102a of the pair of first conveying rollers 102a and 102b, and a second gear 105 is engaged with the first gear 106. A first one-way clutch 104 is connected to the second gear 105, and the first one-way clutch 104 is rotated by a first motor 103 that is a brushless motor. With such a configuration, when the first motor 103 rotates in the forward direction, the first transport rollers 102a and 102b are rotationally driven via the first one-way clutch 104, the second gear 105, and the first gear 106, and the paper feed roller The sheet supplied to the first transport path 150 by the 101a and 101b is transported from the horizontal direction to the vertically upward direction by the first transport rollers 102a and 102b.

  On the other hand, a two-stage paper feed motor 119 composed of a brushless motor is connected to one roller 112a of the pair of second paper feed rollers 112a and 112b in the second transport path 160 via a gear 120. With the rotation of the paper motor 119, the paper feed rollers 112a and 112b are rotationally driven via the gear 120, so that the paper is drawn from the two-stage paper feed cassette and supplied to the second transport path 160.

  A third one-way clutch 116 is connected to one roller 113a of the pair of second transport rollers 113a and 113b via a fourth gear 118 and a fifth gear 117, and this third one-way. The clutch 116 is rotated by a second motor 114 composed of a brushless motor. With such a configuration, when the second motor 114 rotates forward, the second transport rollers 113a and 112b are driven to rotate via the third one-way clutch 116, the fifth gear 117, and the fourth gear 118, and the paper feed roller The sheet supplied to the second conveyance path 160 by 112a and 112b is configured to be conveyed from the horizontal direction to the vertically upward direction by the second conveyance rollers 113a and 113b.

  Further, in this embodiment, a second one-way clutch 115 is connected to the second motor 114, and the second one-way clutch 115 is connected to a gear 108 that meshes with the third gear 107. Has been. When the second motor 114 rotates in the reverse direction, the driving force is not transmitted to the second transport rollers 113a and 113b by the action of the third one-way clutch 116, but the second one-way clutch 115, the gear 108, and the third The driving force of the second motor 114 is transmitted to the first transport rollers 102a and 102b via the gear 107 and the first gear 106. On the other hand, when the second motor 114 rotates forward, the driving force is transmitted to the second conveying rollers 113a and 113b. On the other hand, the driving force is applied to the first conveying rollers 102a and 102b by the action of the second one-way clutch 115. It is not transmitted.

  Accordingly, by rotating the first motor 103 forward and the second motor 114 reversely, the rotational force in the same direction can be simultaneously applied to the first gear 106, and the first transport rollers 102a and 102b are simultaneously driven by the two motors. It can be configured.

  When paper is fed from the first-stage paper cassette, it is necessary to transport the paper by the first transport rollers 102a and 102b in order to stop driving the first paper feed rollers 102a and 102b after the end of the paper feed operation. Further, the first transport rollers 102a and 102b are located immediately after the portion where the paper is bent and transported from the horizontal direction to the vertical direction, and a large torque generated by the motor is required. Similarly, when paper is fed from a two-stage paper cassette, a large motor-generated torque is required for the second transport rollers 113a and 113b.

  When paper is fed from the first-stage paper cassette, the first-stage paper feed motor 109 drives the first paper feed rollers 101a and 101b, the first motor 103 drives the first transport rollers 102a and 102b, Transport the paper to. Since the second transport rollers 113a and 113b do not need to be driven in this case, the second transport rollers 113a and 113b are not driven and connected by the third one-way clutch 116 by driving the second motor 114 in the reverse direction. The second one-way clutch 115 connects the second motor 114 and the first transport rollers 102 a and 102 b to each other. The second motor 114 drives the first transport rollers 102 a and 102 b together with the first motor 103.

  However, when a speed difference is generated between the second gear 105 and the third gear 107, the load torque is not distributed, and a large load is applied to the motor having a higher speed, resulting in an overload. Specifically, when the rotation speed of the second gear 105 is higher than the rotation speed of the third gear 107, the second gear 105 is driven by the first one-way clutch 104 with the first conveying rollers 102a and 102b. The third gear 107 is not drivingly connected. Conversely, when the rotational speed of the second gear 105 is lower than the rotational speed of the third gear 107, the third gear 107 is drivingly connected to the second one-way clutch 115, and the second gear 105 is drivingly connected. Not.

  As understood from the graph of FIG. 2 showing the relationship between the torque and the rotational speed of the brushless motor and the torque and the current, the brushless motors constituting the first motor 103 and the second motor 114 rotate at the target rotational speed when overloaded. Therefore, the rotation speed is lower than the target rotation speed. For this reason, productivity reduction and paper jam (JAM) occur. To prevent this, the rotation speeds of the second gear 105 and the third gear 107 connected to the first gear 106 need to be the same, but the rotation speeds of the first motor 104 and the second motor 114 are kept constant. Even if the control is performed, there is a possibility that a speed difference may occur between the second gear 105 and the third gear 107 depending on the gear connection configuration.

  Therefore, in this embodiment, as motor control, the first motor 103 performs speed control, and the second motor 114 performs torque control. FIG. 3 is a block diagram showing a configuration of a control unit when such motor control is performed.

  The speed control of the first motor 103 is performed as follows. That is, the rotational speed is detected (calculated) based on the rotational information (FG signal) of the first motor 103 by the speed detector 203. The speed error amplifier 201 compares the rotation speed of the first motor 103 detected by the speed detection unit 203 with the rotation speed command of the first motor from the main body control unit of the image forming apparatus, and calculates the speed error. Based on the amplified and calculated speed error, the speed controller 202 causes the first motor 103 to converge to the target rotational speed.

  On the other hand, torque control of the second motor 114 is performed as follows. That is, the first motor current detection unit 213 detects the current of the first motor 103, and the second motor current detection unit 214 detects the current of the second motor 114. Then, the detected current of the first motor 103 and the current of the second motor 114 are compared by the current error amplifier 211, the current error is calculated and amplified, and the current controller 212 based on the calculated current error. The current control unit 212 controls the current value of the second motor so that the load torque ratio between the first motor 103 and the second motor 114 becomes a preset target value. That is, as shown in FIG. 4, assuming that the load torque applied to the first motor 103 is T1, and the load torque applied to the second motor 114 is T2, the load torque ratios T1 / (T1 + T2) and T2 / (T1 + T2) are the target. Current control is performed so that the values R1 and R2 are obtained.

  The target value of the load torque ratio between the first motor 103 and the second motor is set to be smaller than the torque generated by each motor after distributing the load torque of the two motors. The target value of the load torque ratio can be set by the gear connection configuration of the first motor 103, the second motor 114, and the first transport rollers 102a and 102b. That is, the speed of the first motor 103 is controlled at a constant speed regardless of the rotation information and the load torque of the second motor 114, and the second motor 114 uses the load torque ratio of the first motor 103 and the second motor 114 as a target value. Keep current control.

  By performing the above control, it is possible to distribute the load torque to the first motor 103 and the second motor 114, and to rotate the first transport rollers 102a and 102b at a target rotational speed.

  FIG. 5 is a flowchart showing a motor drive control operation executed by the image forming apparatus when copying is performed.

  In step S01, print information is acquired. In step S02, the first-stage paper feed motor 109 is activated to feed paper from the first-stage paper feed cassette. The one-stage paper feed motor 109 is driven until the paper feed operation is completed.

  Next, in step S03, a rotational speed command for the first motor 103 and a speed control command for convergence to the target rotational speed are given. Next, in step S04, target values R1 and R2 of the load torque ratio of the first motor 103 and the second motor 114 are acquired.

  Subsequently, in step S05, the first motor 103 is activated and the second motor 114 is activated in reverse rotation. Then, in step S06, current values I1 and I2 of the first motor 103 and the second motor 114 are measured. In step S07, load torques T1 and T2 applied to the first motor 103 and the second motor 114 are calculated from the measured current values.

  In step S08, it is determined whether or not R1> T1 / (T1 + T2) based on the calculated load torques T1 and T2 and the target value R1 of the load torque ratio. If R1> T1 / (T1 + T2) (YES in step S08), the rotation speed of the third gear 107 is slower than that of the second gear 105. Therefore, after the second motor 114 is increased in step S09, the process proceeds to step S11. . If R1> T1 / (T1 + T2) is not satisfied (NO in step S08), the rotation speed of the third gear 107 is higher than that of the second gear 105. Therefore, in step S10, the second motor 114 is decelerated to reduce the second gear 105. And the third gear 107 are eliminated so that the load torque ratio becomes R1, and the process proceeds to step S11.

  In step S11, it is determined whether or not the sheet conveyance has been completed. If the sheet conveyance has not been completed (NO in step S11), the process returns to step S08 and the above control is continued until the sheet conveyance is completed. When the paper conveyance is completed (YES in step S11), the first motor 103 is stopped in step S12, and the second motor 114 is stopped in step S13.

  Thus, in this embodiment, the first motor 103 and the second motor 114 and the first conveying rollers 102a and 102b, which are rotational loads, are connected via the first and second one-way clutches 104 and 105, respectively. By controlling the speed of the first motor 103 and controlling the load torque of the second motor 114, the first conveying rollers 102a and 102b can be driven while distributing the load torque. Accordingly, even when the first motor 103 alone cannot provide the necessary torque, the second motor 114 compensates for the torque shortage due to the first motor 103, and sufficient torque is secured to secure the first transport rollers 102a and 102b. Can be driven stably at high speed.

  In addition, since the existing second motor 114 that drives the second transport rollers 113a and 113b is used as a motor for performing load torque control, there is no need to add a new motor, and a space-saving and low-cost drive coupling mechanism is provided. Image forming apparatus.

  FIG. 6 is a flowchart of the paper feed operation end process. By stopping the first stage paper feed motor 109 in step S21, the paper feed ends.

  FIG. 7 is a view corresponding to FIG. 1 showing a configuration of a main part of a sheet transport mechanism of an image forming apparatus according to another embodiment of the present invention.

  In this embodiment, not only the fifth gear 117 but also the sixth gear 133 meshes with the fourth gear 118 connected to one of the second transport rollers 113a and 113b, and the sixth gear 133 engages with the sixth gear 133. A first-stage sheet feeding roller 109 is connected via a fourth one-way gear 134.

  The first-stage paper feed motor 109 is connected to the gear 111 and further to the first paper feed rollers 101a and 101b via a fifth one-way clutch 135.

  Since the other configuration is the same as that of the summary transport mechanism shown in FIG. 1, the same components are denoted by the same reference numerals, and description thereof is omitted.

  In the embodiment shown in FIG. 7, in addition to driving the first transport rollers 102 a and 102 b, the second transport rollers 113 a and 113 b are also driven by two motors, the second motor 114 and the one-stage paper feed motor 109. Is called.

  That is, when the one-stage paper feed motor 109 is rotated forward, the first paper feed rollers 101a and 101b are rotationally driven via the fifth one-way clutch 135 and the gear 111, while the fourth one-way clutch 134 is rotated. As a result, the first-stage paper feed motor 109 and the sixth gear 133 are not connected, and the second transport path rollers 113 a and 113 b are not driven by the first-stage paper feed motor 109.

  Conversely, when the first-stage paper feed motor 109 is rotated in the reverse direction, the gear 111 is not connected to the first-stage paper feed motor 109 due to the action of the fifth one-way clutch 135, but via the fourth one-way clutch 134. The first-stage paper feed motor 109 is connected to the sixth gear 133 and the fourth gear 118, and the second transport path rollers 113 a and 113 b can be driven by the first-stage paper feed motor 109.

  In this embodiment, when the paper is fed from the two-stage paper cassette, the second paper feeding rollers 112a and 112b are driven by the two-stage paper feeding motor 119, and the second motor 114 is rotated forward to rotate the second conveying roller. The sheets 113 a and 113 b are driven to convey the sheet upward along the second conveyance path 160. Since the first paper feed rollers 101a and 101b do not need to be driven in this case, the first paper feed motor 109 and the second paper feed motor 109 and the second paper feed motor 109 are driven in reverse by the fourth one-way clutch 134. The conveyance rollers 113a and 113b are drivingly connected, and the first-stage sheet feeding motor 109 drives the second conveyance rollers 113a and 113b together with the second motor 114.

  Also in this case, as in the embodiment shown in FIG. 1, as motor control, the second motor 114 performs speed control at a constant speed, and the first-stage paper feed motor 109 performs torque control. The operation of the image forming apparatus in this case is the same as that in the flowchart of FIG. 5 in which the first motor 103 is replaced with the second motor 114 and the second motor 114 is replaced with the one-stage sheet feeding motor 109.

  As described above, in the embodiment shown in FIG. 7 as well, the second motor 114 and the one-stage sheet feeding motor 109 and the second transport rollers 113a and 113b as rotational loads are respectively connected to the third and fourth one-way clutches. 116 and 134, and the second motor 114 is driven at a constant speed while distributing the load torque by controlling the speed of the second motor 114 and controlling the load torque of the first-stage paper feed motor 109. It becomes possible. Therefore, even when the necessary torque cannot be produced by the single second motor 114, the shortage of torque by the second motor 114 is compensated by the first-stage paper feed motor 109, and sufficient torque is secured to ensure that the second transport roller 113a. 113b can be stably rotated at a high speed.

  In addition, since the existing one-stage paper feed motor 109 that drives the first paper feed rollers 101a and 101b is used as a motor for load torque control, there is no need to add a new motor, and the drive connection is space-saving and low-cost. An image forming apparatus including the mechanism is obtained.

  FIG. 8 shows an example of the target value of the load torque ratio between the first motor 103 and the second motor 114 in the image forming apparatus according to the embodiment shown in FIG. 1, and the loads on the first motor 103 and the second motor 114 are shown. A case where the torque is set to target values R1 = 0.5 and R2 = 0.5 will be described. FIG. 4A shows a case where the first conveying rollers 102a and 102b are driven by the first motor 103 and the second motor 114, and FIG. 4B shows the first conveying rollers 102a and 102b only by the first motor 103. The case of driving is shown. The same applies to the relationship between the second motor 114 and the first-stage paper feed motor 109 in the embodiment shown in FIG.

  The motor generated torques when the first motor 103 and the second motor 114 are rotated at a rotation speed of 2000 rpm are 80 mN · m and 80 mN · m, respectively. In order to distribute the load torque to 1: 1, the reduction ratio between the first motor 103 and the first transport rollers 102a and 102b is 0.45, and the reduction ratio between the second motor 114 and the transport rollers 102a and 102b is 0. Do 45. However, the gear meshing is 3 stages and the transmission efficiency per stage is 0.92. When the assumed maximum load torque of the first conveying rollers 102a and 102b is 180 mN · m, the load torques at the output shafts of the first motor 103 and the second motor 114 are 52.0 mN · m, respectively. In this case, the load torques of the first motor 103 and the second motor 114 are set as target values R1 = 0.5 and R2 = 0.5. As described above, the gear connection configuration and the target value of the load torque ratio are set so that the load torque of the motor output shaft is smaller than the motor generated torque of each of the first motor 103 and the second motor 114.

  Even if the first motor 103 is driven alone, if the reduction ratio between the first motor 103 and the first conveying rollers 102a and 102b is 0.45, the generated torque of the first motor 103 is 80 mN · m, and the motor output Since the load torque at the shaft is 104 mN · m, the first motor 103 alone cannot be driven at the target rotational speed (2000 rpm).

  In the above example, the case where the target values of the load torque ratio are R1 = 0.5 and R2 = 0.5 has been described. However, between the first motor 103 and the second motor 114 and the first transport rollers 102a and 102b, Other target values can be set depending on the gear coupling configuration.

  By the way, when the first transport rollers 102a and 102b are driven by two motors as in this embodiment, the torque is advantageous, but when the motors are driven, aged deterioration occurs, so that the first transport rollers 102a and 102b can be driven by only one motor. In some cases, it is desirable to drive with only one motor. However, constant speed control is performed when driving only by the first motor 103.

  Specifically, when the transport speed changes according to the paper type, for example, when transporting paper at 500 mm / s for plain paper and 250 mm / s for thick paper, the motor for thick paper is rotated at half the rotational speed with respect to plain paper. Rotate. When the rotational speed is low, the motor-generated torque increases, so that it can be driven only by the first motor 103.

  Further, since the motor-generated torque varies depending on the ambient temperature and humidity, when it can be determined that the drive can be performed only by the first motor 103 based on the ambient temperature and humidity, the drive is performed only by the first motor 103. In addition, when the load torques T1 and T2 are calculated from the measured values of the current values I1 and I2 of the first motor 103 and the second motor 104, and T1 + T2 is smaller than the motor generation torque of the first motor 103, the first motor 103 Only the first conveying rollers 102a and 102b are driven. When it is determined that the first motor 103 alone cannot be used for driving, the first motor 103 and the second motor 114 drive the first transport rollers 102a and 102b.

  The determination as to whether the second transport rollers 113a and 113b are driven by the second motor 114 and the first-stage paper feed motor 109 or only by the second motor 114 is the same as described above.

  FIG. 9 is a flowchart illustrating a process in which the image forming apparatus determines whether the first transport rollers 102 a and 102 b are driven only by the first motor 103 or the second motor 114 together with the first motor 103. The same applies to the process of determining whether the second transport rollers 113a and 113b are driven by the second motor 114 and the first-stage paper feed motor 109 or only by the second motor 114.

  After the print information is acquired in step S31, it is determined in step S32 whether the paper is a thick paper. If it is thick paper (YES in step S32), the process proceeds to step S38.

  If the sheet is not a thick sheet (NO in step S32), it is determined in step S33 whether the temperature and humidity can be driven only by the first motor 103. If the temperature and humidity can be driven only by the first motor 103 (YES in step S33), the process proceeds to step S38. If the temperature and humidity cannot be driven only by the first motor 103 (NO in step S33), the current values I1 and I2 of the first motor 103 and the second motor 114 are measured in step S34, respectively.

  Next, after calculating the load torques T1 and T2 from the measured current values I1 and I2 in step S35, it is determined whether or not the load torque can be driven only by the first motor 103 in step S36. If the load torque can be driven only by the first motor 103 (YES in step S36), the process proceeds to step S38. If the load torque is not drivable only by the first motor 103 (NO in step S36), the process proceeds to step S37.

  In step S <b> 37, the first transport rollers 102 a and 102 b are driven by the first motor 103 and the second motor 114. In this case, the first motor 103 is controlled at a constant speed, and the second motor 114 is subjected to load torque control.

  On the other hand, in step S38, the first transport rollers 102a and 102b are driven only by the first motor 1. In this case, the first motor 103 is controlled at a constant speed.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

  For example, the case where the conveyance rollers are driven by two motors while the sheet is conveyed by the first conveyance rollers 102a and 102b or the second conveyance rollers 113a and 113b has been exemplified. However, the first motor 103 and the second motor are exemplified. Only when the first motor is used, such as when a large load torque is applied or when a sudden load is applied, such as when the sheet 114 enters the first conveyance rollers 102a and 102b or the second conveyance rollers 113a and 113b. When the driving cannot be performed, the first motor 103 and the second motor 114 drive the first conveying rollers 102a and 102b, or the second motor 114 and the one-stage paper feeding motor 109 drive the second conveying rollers 113a and 113b. Other than the timing, the conveying roller may be driven by only one motor.

  FIG. 10 is a flowchart showing the operation of the image forming apparatus when the first transport rollers 102a and 102b are driven by the first motor 103 and the second motor 114 only when the paper enters the first transport rollers 102a and 102b. It is. The same applies to the case where the second transport rollers 113a and 113b are driven by the second motor 114 and the first-stage paper feed motor 109 only when the sheet enters the second transport rollers 113a and 113b.

  After starting the first motor 103 in step S41, it is determined in step S42 whether it is 100 ms before entering the first conveying rollers 102a and 102b. If it is not 100 ms before paper entry (NO in step S42), it waits until it reaches 100 ms. If it is 100 ms before paper entry (YES in step S42), the second motor 114 is activated in step S43. As in the embodiment described with reference to FIGS. 1 and 7, the first motor 103 is controlled at a constant speed, and the second motor 114 is torque-controlled.

  Next, it waits for 200 ms to elapse in step S44 (NO in step S44), and when elapses (YES in step S44), the second motor 114 is stopped in step S45.

  FIG. 11 is a flowchart illustrating the operation of the image forming apparatus when the first transport rollers 102a and 102b are driven by the first motor 103 and the second motor 114 only when the first motor 103 is activated. The same applies to the case where the second transport rollers 113a and 113b are driven by the second motor 114 and the first-stage paper feed motor 109 only when the second motor 114 is activated.

  In step S51, print information is acquired. In step S52, the first-stage paper feed motor 109 is activated to feed paper from the first-stage paper feed cassette. The one-stage paper feed motor 109 is driven until the paper feed operation is completed.

  Next, in step S53, a rotational speed command for the first motor 103 and a speed control command for convergence to the target rotational speed are given. Next, in step S54, target values R1 and R2 of the load torque ratio of the first motor 103 and the second motor 114 are acquired.

  Subsequently, in step S55, the first motor 103 is activated and the second motor 114 is activated in reverse rotation, and then in step S56, the current values I1 and I2 of the first motor 103 and the second motor 114 are measured. In step S57, load torques T1 and T2 applied to the first motor 103 and the second motor 114 are calculated from the measured current values.

  In step S58, it is determined whether R1> T1 / (T1 + T2) based on the calculated load torques T1, T2 and the target value R1 of the load torque ratio. If R1> T1 / (T1 + T2) (YES in step S58), the second motor 114 is accelerated in step S59, and then the process proceeds to step S61. If R1> T1 / (T1 + T2) is not satisfied (NO in step S58), the second motor 114 is decelerated in step S60, finely adjusted so that the load torque ratio becomes R1, and then the process proceeds to step S61.

  In step S61, it is determined whether or not the first motor 103 has rotated at a constant speed. If the first motor 103 has not rotated at a constant speed (NO in step S61), the process returns to step S58 and continues until the first motor 103 rotates at a constant speed. Continue control. When the first motor 103 rotates at a constant speed (YES in step S61), the second motor 114 is stopped in step S62.

102a, 102b First transport roller 103 First motor 104 First one-way clutch 109 One-stage paper feed motor 113a, 113b Second transport roller 114 Second motor 115 Second one-way clutch 116 Third one-way clutch 134 Fourth one-way clutch 135 Fifth one-way clutch 119 Two-stage paper feed motor

Claims (10)

A first motor that drives a first conveying roller that conveys a sheet via a first one-way clutch;
A second motor for driving a second transport roller different from the first transport roller, the second motor capable of driving the first transport roller via a second one-way clutch;
When the first transport roller is driven by the first motor, the first motor is fixed to rotate the first transport roller at a target speed when the first motor is simultaneously driven by the second motor. Speed control means for speed control,
Torque detecting means for detecting load torque of the first motor and the second motor;
Based on the detection results of the load torques of the first motor and the second motor by the torque detection means, the load torque of the second motor is controlled so that the load torque ratio of the first motor and the second motor becomes a target value. Torque control means for
An image forming apparatus comprising: A third one-way clutch disposed between the second motor and the second transport roller;
Speed control means for controlling the speed of the second motor at a constant rate,
The second motor performs a constant speed control during forward rotation to drive the second transport roller via the third one-way clutch, and is connected to the first transport roller during reverse rotation to connect the first transport roller. The image forming apparatus according to claim 1, wherein the first conveying roller is driven together with one motor.   The image forming apparatus according to claim 1, wherein the load torque is detected by the torque detection unit by detecting currents of the first motor and the second motor.   The first transport roller is provided in a first transport path for transporting paper fed from a first paper feed cassette, and the second transport roller transports paper fed from a second paper feed cassette, The first transport roller is provided on a second transport path different from the first transport path, and the first transport roller is simultaneously driven by the second motor when the first transport roller is driven by the first motor. The image forming apparatus according to any one of the above. A paper feed motor for feeding paper fed from the first paper cassette;
When the second transport roller is driven by the second motor, the second transport roller is simultaneously driven by the paper feed motor,
The speed control means controls the second motor at a constant speed in order to rotate the second transport roller at a target speed, and the torque control means determines a load torque ratio between the second motor and the paper feed motor. The image forming apparatus according to claim 1, wherein the load torque of the paper feed motor is controlled so as to be a target value.   The image according to any one of claims 1 to 5, wherein a target value of a load torque ratio between the first motor and the second motor is set so that a load torque of the two motors is smaller than a torque generated by each motor. Forming equipment.   The image forming apparatus according to claim 1, wherein when the sheet conveyance speed is decreased according to the sheet type, the first conveyance roller is driven only by the first motor.   The first conveying roller is driven only by the first motor when the first longitudinal conveying roller can be driven only by the first motor as a result of detecting the load torque by the torque detecting means. The image forming apparatus according to any one of the above.   9. The image forming apparatus according to claim 1, wherein the first transport roller is driven by the first motor and the second motor only when the first motor is started or when the sheet enters the first transport roller. . Driving a first transport roller for transporting paper with a first motor via a first one-way clutch;
A second motor for driving a second conveyance roller different from the first conveyance roller when the first conveyance roller is driven by the first motor, wherein the first conveyance roller has a second one-way clutch; A step of controlling the speed of the first motor at a constant speed to rotate the first transport roller at a target speed when simultaneously driving the first transport roller by a second motor that can be driven via
Detecting load torques of the first motor and the second motor;
Controlling the load torque of the second motor so that the load torque ratio of the first motor and the second motor becomes a target value based on the detection result of the load torque of the first motor and the second motor;
A method for driving a sheet conveying motor in an image forming apparatus.

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