JP2011109866A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller that is achieved at low cost, capable of speedily stopping a rotor at a prescribed stop position when stopped, and capable of speedily starting the rotor when started. <P>SOLUTION: The motor controller 1 includes a brushless motor 22 that is arranged as a driving source for conveying paper and has a rotor 24 and a stator 23, an encoder 31 detecting a rotation position of the rotor 24 and a control unit 10 controlling the brushless motor 22 based on the rotation position of the rotor 24, which is detected by the encoder 31 in a starting section, a regular section and a stop section of the brushless motor 22. The control unit 10 performs servo locking and stops the brushless motor 22 when the rotor 24 comes to a prescribed stop position with respect to the stator 23 based on the rotation position of the rotor 24, which is detected by the encoder 31, after rotational speed becomes stop possible speed in the stop section of the brushless motor 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor control device that controls a brushless motor provided as a drive source for conveying paper in an image processing apparatus such as a printer apparatus, an MFP (Multi Function Peripheral), or a scanner apparatus that automatically conveys a document. .

  Conventionally, as a method for controlling a rotor position by driving a brushless motor without a sensor, the rotor position is regulated by energizing two of the three stator coils to generate a static magnetic field. The technique which performs is proposed (for example, patent document 1, 2). However, in this technique, since it is sensorless drive, it cannot be stopped while monitoring the position of the rotor, so it takes time to stop the rotor at a predetermined position.

JP 7-163180 A JP 2008-271698 A

  Conventionally, a brushless motor is used as a drive source for transporting paper also in an image processing apparatus having a paper transport mechanism. In this case, vector control is generally employed as a control method for driving the brushless motor. Vector control is to control the position of the rotor with high accuracy by changing the current of each phase while comparing the current position of the rotor and the target position while detecting the current flowing through the stator coil of each phase. is there. According to such vector control, an ideal rotation speed and torque output can be obtained, and the efficiency as a drive source is improved. In the case of vector control, a reduction in noise during driving can be expected.

  However, if vector control is adopted as a control method of a brushless motor for conveying paper in the image processing apparatus, the position of the rotor can be controlled with high precision, but the drive circuit and its control circuit are complicated. There is a problem that the motor control mechanism becomes expensive.

  In an image processing apparatus, a sheet to be transported is often not at a fixed position, and even if the position of a brushless motor is controlled with high accuracy, it is difficult to eliminate the misalignment of the sheet. For this reason, when the paper is transported in the image processing apparatus, if the positional deviation of the paper is within a certain range, it is processed as normal transport. Such an image processing apparatus does not require a highly accurate and expensive control mechanism such as vector control in order to control the brushless motor. On the contrary, for an image processing apparatus, it is possible to configure an inexpensive control mechanism by adopting a control method that is simpler than vector control, so that the conveyance of a sheet can be started promptly when the activation of the brushless motor is started. preferable.

  On the other hand, when the control method as described in Patent Document 1 or 2 described above is employed in the image processing apparatus, it takes time until the rotor is stopped. For example, when a plurality of sheets are continuously conveyed, the sheet conveyance is performed. There arises a problem that the interval becomes longer and the conveyance efficiency is lowered.

  Accordingly, the present invention has been made to solve the above-described conventional problems, and can be realized at a low cost. The rotor can be quickly stopped at a predetermined stop position when stopped, and at the time of startup. An object of the present invention is to provide a motor control device capable of quickly starting a rotor.

  In order to achieve the above object, the invention according to claim 1 is a motor control device, which is provided as a drive source for transporting paper, and includes a brushless motor having a rotor and a stator, and the rotor in the brushless motor. Position detecting means for detecting the rotational position of the brushless motor, and control means for controlling the brushless motor based on the rotational position of the rotor detected by the position detecting means in each of the start, steady and stop sections of the brushless motor. The control means is configured such that, after the rotation speed of the brushless motor reaches a stoppable rotation speed in the stop section, the rotor is moved based on the rotation position of the rotor detected by the position detection means. Servo lock is executed when the stator is at a predetermined stop position, and the brushless motor is A structure for causing locked.

  According to such a configuration, it is possible to suppress variation in the stop position of the rotor when stopping the brushless motor with relatively simple control without performing vector control, and to quickly move the rotor at a predetermined stop position. It can be stopped.

  According to a second aspect of the present invention, in the motor control device according to the first aspect, the predetermined stop position is a position where the magnetic resistance between the rotor and the stator is substantially minimum. .

  According to such a configuration, it is possible to suppress variations in the rotational speed when the brushless motor is activated.

  According to a third aspect of the present invention, in the motor control device according to the second aspect, the control means starts deceleration control so as to stop the brushless motor in a predetermined stop time in the stop section, and the rotor and the The brushless motor is stopped by executing servo lock at a position where the magnetic resistance with the stator is substantially minimum.

  According to a fourth aspect of the present invention, in the motor control device according to the third aspect of the invention, the control means is configured so that the rotor is at the predetermined stop position with respect to the stator before and after the predetermined stop time. The brushless motor is stopped by executing servo lock.

  According to a fifth aspect of the present invention, in the motor control device according to any one of the first to fourth aspects, the position detecting means is an encoder.

  According to a sixth aspect of the present invention, in the motor control device according to the fifth aspect of the present invention, the control means outputs from the encoder after the rotation speed of the brushless motor reaches a stoptable rotation speed in the stop section. Based on a predetermined position detection signal, a timing at which the rotor is at the predetermined stop position with respect to the stator is predicted, and servo lock is executed at the predicted timing.

  A seventh aspect of the present invention is the motor control device according to any one of the first to fourth aspects, wherein the position detecting means is a Hall element.

  According to an eighth aspect of the present invention, in the motor control device according to the seventh aspect, the control means outputs from the hall element after the rotation speed of the brushless motor reaches a stopable rotation speed in the stop section. The timing at which the rotor reaches the predetermined stop position with respect to the stator is predicted based on the position detection signal, and the servo lock is executed at the predicted timing.

  According to a ninth aspect of the present invention, in the motor control device according to any one of the first to eighth aspects, a time from a minimum duty at which the rotor can be stopped when the control means executes a servo lock. A servo lock signal whose duty decreases with the passage of time is applied to the brushless motor.

  According to a tenth aspect of the present invention, in the motor control device according to any one of the first to ninth aspects, the servo lock signal given to the brushless motor when the control means executes a servo lock is the first of the brushless motors. This is a configuration characterized in that it is a signal for exciting the motor in the reverse direction.

  According to the motor control device of the present invention, after reaching the number of rotations that can be stopped in the stop section of the brushless motor, the servo is detected when the rotor is at a predetermined stop position with respect to the stator while detecting the rotation position of the rotor. Since the brushless motor is stopped by performing locking, it is possible to suppress variations in the stop position of the rotor and to stop the rotor quickly at a predetermined stop position. Further, by stopping the rotor at a predetermined stop position, it is possible to quickly start the rotor when the brushless motor is started. The motor control apparatus according to the present invention does not require a highly accurate and expensive vector control mechanism, and can be realized at low cost.

It is a figure which shows one structural example of a motor control apparatus. It is a figure which shows the example which has the positional relationship from which the rotor and stator of a brushless motor each differ. It is a figure which shows the relationship between the stop position of a rotor, and the dispersion | variation in the starting time of a brushless motor. It is a figure which shows an example of the driving map information of a brushless motor. It is a figure which shows the one aspect | mode of the stop control of the brushless motor in a stop area. It is a figure which shows an example of a servo lock signal. FIG. 5 is a diagram illustrating an example of an actual operation state of a brushless motor when continuous conveyance of paper is performed in the image processing apparatus. It is a figure which shows the comparative example of the actual driving | running state of a brushless motor at the time of stopping without performing a servo lock at the time of a stop of a brushless motor. It is a flowchart which shows an example of the processing sequence by CPU. It is a flowchart which shows an example of the detailed process sequence of motor drive control. It is a flowchart which shows an example of the detailed process sequence of motor drive control. It is a figure which shows the example of a different structure of a motor control apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments described below, members that are common to each other are denoted by the same reference numerals, and redundant descriptions thereof are omitted.

  FIG. 1 is a diagram illustrating a configuration example of a motor control device 1 according to the present embodiment. The motor control device 1 is provided as a drive mechanism for transporting paper in an image processing apparatus such as a printer device, an MFP, or a scanner device that automatically transports a document. As shown in FIG. 1, the motor control device 1 includes a control unit 10, a motor unit 20, and an encoder 31. The motor unit 20 includes a brushless motor 22 and a drive circuit 21 that drives the brushless motor 22, which are configured as a unit for one substrate, for example. The brushless motor 22 transmits power to a paper transport mechanism (not shown). Therefore, when the brushless motor 22 is activated, the conveyance of the paper is started in the image processing apparatus.

  The brushless motor 22 includes a stator 23 having three-phase (U-phase, V-phase, W-phase) stator coils arranged at intervals of 120 °, and a four-pole rotor 24 composed of permanent magnets. In the rotor 24, the direction indicated by the arrow R in the figure is the forward rotation direction, and the direction opposite to the arrow R is the reverse rotation direction. The brushless motor 22 is provided with a plurality of Hall elements 25a, 25b, and 25c for detecting the position of the rotor 24.

  The drive circuit 21 rotates the rotor 24 by supplying current to each of the U-phase, V-phase, and W-phase stator coils. That is, the drive circuit 21 includes switching elements (not shown) for causing currents to flow in the U phase, the V phase, and the W phase, and the rotor 24 is based on output voltages from the plurality of Hall elements 25a, 25b, and 25c. Is detected and the switching element is switched on and off in accordance with the detected position, so that a drive current flows in each phase. Such a drive circuit 21 drives the brushless motor 22 based on a command from the control unit 10.

  The control unit 10 includes a CPU 11, a RAM 12, and a ROM 13. The CPU 11 receives a position detection signal from an encoder 31 that detects the position of the rotor 24, and outputs various control signals such as a PWM signal, a servo lock signal, and a brake signal to the drive circuit 21 based on the position detection signal. The control means controls the brushless motor 22. The RAM 12 is a storage unit that stores temporary data when the CPU 11 performs arithmetic processing. The ROM 13 is a nonvolatile storage unit that stores operation map information 14 in which a target value for controlling the brushless motor 22 is defined.

  For example, when the CPU 11 receives a sheet conveyance command from the main controller of the image processing apparatus, the CPU 11 appropriately outputs a PWM signal, a servo lock signal, and a brake signal according to the operation map information 14 stored in the ROM 13.

  The PWM signal is a signal that is mainly output in a start-up section in which the brushless motor 22 is started up to a steady state and a steady section in which the steady state is continued, and adjusts the power applied when the drive circuit 21 drives the brushless motor 22. It is a signal to do. That is, the PWM signal is output, for example, when accelerating the brushless motor 22 or maintaining a constant rotational speed. The CPU 11 determines the pulse width (duty) of the PWM signal so that the target value defined in the operation map information 14 is obtained based on the position detection signal output from the encoder 31 in the startup period and the steady period of the brushless motor 22. ) And output to the drive circuit 21. As a result, the drive circuit 21 drives the brushless motor 22 based on the PWM signal input from the CPU 11.

  The brake signal is a signal that is mainly output in a stop section in which the brushless motor 22 is stopped, and is a signal that is output when the rotor 24 is decelerated. The CPU 11 intermittently outputs the brake signal so that the target value defined in the operation map information 14 is obtained based on the position detection signal output from the encoder 31 during the stop period of the brushless motor 22. When receiving a brake signal from the CPU 11, the drive circuit 21 decelerates the rotor 24 by exciting the rotor 24 in the reverse direction.

  The servo lock signal is output at a timing when the rotor 24 reaches a predetermined stop position with respect to the stator 23 after the rotation speed of the brushless motor 22 reaches a stoptable rotation speed in a stop section where the brushless motor 22 is stopped. Signal. By outputting this servo lock signal, the CPU 11 executes the servo lock and stops the rotor 24 at a predetermined stop position.

  Here, the stop position where the rotor 24 is stopped by executing the servo lock will be described. FIG. 2 is a diagram illustrating an example in which the rotor 24 and the stator 23 are in different positional relationships in the brushless motor 22. FIG. 2A shows a state where the rotor 24 stops at the point A, and FIG. 2B shows a state where the rotor 24 stops at the point B. FIG. 2C shows a state where the rotor 24 is stopped at the point C.

  First, as shown in FIG. 2A, when the rotor 24 is stopped at the point A, the U-phase stator is at a position facing the S pole of the rotor 24. That is, the entire U-phase stator faces the south pole of the rotor 24.

  Next, as shown in FIG. 2B, in a state where the rotor 24 is stopped at the point B, most of the U-phase stator is opposed to the S pole of the rotor 24, but a part of the stator is the rotor 24. Opposite the N pole.

  Next, as shown in FIG. 2C, when the rotor 24 is stopped at the point C, the portion where the U-phase stator faces the S pole of the rotor 24 is smaller than that in FIG. The portion of the rotor 24 facing the north pole is increasing.

  Of the three stop positions, the stop position at which the magnetic resistance between the rotor 24 and the stator 23 is substantially minimum is the point A shown in FIG. Therefore, as shown in FIG. 2A, if the brushless motor 22 is started by performing U-phase excitation while the rotor 24 is stopped at the point A, the brushless motor 22 can be started at a substantially maximum torque. As a result, the rotational speed of the brushless motor 22 can be quickly reached the target rotational speed.

  FIG. 3 is a diagram showing the variation in start-up time when the brushless motor 22 is started in a state where the rotor 24 is in the three stop positions (point A, point B, point C). As described above, when the activation of the brushless motor 22 is started while the rotor 24 is stopped at the point A (see FIG. 2A), the rotation speed of the brushless motor 22 increases immediately after the activation, The time required to reach the number of revolutions is minimal. On the other hand, when the stop position of the rotor 24 deviates from the point A, a time lag occurs between the start of the start of the brushless motor 22 and the rotation speed increases until the target rotation speed is reached. The time will be longer. As described above, when the rise of the rotation speed of the brushless motor 22 is delayed, a delay occurs in the sheet conveyance start timing in the image processing apparatus.

  Therefore, in this embodiment, when the CPU 11 of the control unit 10 stops the brushless motor 22, the positional relationship between the rotor 24 and the stator 23 is sequentially detected based on the position detection signal from the encoder 31, and the rotor 24 becomes the point A. Servo lock is executed by outputting a servo lock signal at timing, and the rotor 24 is controlled to stop at point A. Thus, the next time the brushless motor 22 is started, the brushless motor 22 can be started in a state where the magnetic resistance between the rotor 24 and the stator 23 is substantially minimum, and the brushless motor 22 starts to start. Accordingly, the rotational speed can be quickly increased.

  In FIG. 2, the point A that is the stop position of the rotor 24 is illustrated in relation to the U-phase stator and the S pole of the rotor 24, but in addition to this, the U-phase stator and the N pole of the rotor 24 In this relationship, there is a stop position at which the magnetic resistance is substantially minimum. In addition, there is a stop position at which the magnetic resistance is substantially minimum in the relationship between the V-phase stator and each of the S pole and N pole of the rotor 24. Further, there is a stop position at which the magnetic resistance is substantially minimum in the relationship between the W-phase stator and each of the S pole and N pole of the rotor 24. Therefore, there are a plurality of stop positions (points A) at which the magnetic resistance of the stator 23 and the rotor 24 is substantially minimized during one rotation of the rotor 24. Therefore, when the CPU 11 stops the brushless motor 22, the closest stop position at which the rotor 24 can be stopped by sequentially detecting the positional relationship between the rotor 24 and the stator 23 based on the position detection signal from the encoder 31. Servo lock is executed at the timing when the rotor 24 passes, and the rotor 24 is controlled to stop at the stop position. Hereinafter, such a motor control device 1 will be described in more detail.

  FIG. 4 is a diagram illustrating an example of the operation map information 14 of the brushless motor 22. Such operation map information 14 is defined in advance corresponding to the sheet transport operation in the image processing apparatus. The driving map information 14 may be different information depending on the paper size and type. As shown in FIG. 4, the operation map information 14 includes an activation period in which the rotational speed is accelerated to the target rotational speed N between timing T1 and timing T2 when the brushless motor 22 starts to be activated, and timing T2 to timing T3. Between the timing T3 and the timing T4, a stationary section in which the target rotational speed N is maintained and a stop section in which the rotational speed is decelerated and finally stopped are determined. That is, the operation map information 14 defines the target rotational speed N of the brushless motor 22 and the times of the start section, the steady section, and the stop section.

  The CPU 11 controls the brushless motor 22 based on such operation map information 14. That is, the CPU 11 monitors the position of the rotor 24 based on the position detection signal from the encoder 31 in each of the start section, the steady section, and the stop section, and the operation state of the brushless motor 22 matches the operation map information 14. To control.

  For example, if the rotational speed of the rotor 24 is deviated from the target value of the operation map information 14 in the startup section or the steady section, the CPU 11 changes the duty of the PWM signal so that the actual rotational speed approaches the target value. To control.

  In the stop section, by intermittently outputting a brake signal, the brake operation and the free-run operation of the brushless motor 22 are alternately performed to decelerate the brushless motor 22 so as to match the operation map information 14. .

  FIG. 5 is a diagram illustrating one mode of stop control of the brushless motor 22 by the CPU 11. As shown in FIG. 5, when the actual rotation speed of the rotor 24 exceeds the target value defined in the operation map information 14, the CPU 11 brakes the rotor 24 by outputting a brake signal. When the actual rotational speed of the rotor 24 falls below the target value defined in the operation map information 14, the brake signal is turned off and the rotor 24 is set in a free-run state. By repeating such an operation, the rotor 24 is decelerated so as to substantially coincide with the target value.

  Then, the CPU 11 monitors the positional relationship between the rotor 24 and the stator 23 based on the position detection signal from the encoder 31 after the rotation speed of the brushless motor 22 becomes equal to or less than the rotation speed N1 that can be stopped. By outputting a servo lock signal at the timing when the rotational position becomes the above-described stop position (point A), the servo lock is executed and the brushless motor 22 is stopped.

  FIG. 6 is a diagram illustrating an example of a servo lock signal output from the CPU 11. The servo lock signal is a signal in which a pulse signal for exciting the brushless motor 22 in the reverse direction and a pulse signal for exciting in the forward direction are output alternately. By adjusting the duty of the servo lock signal, the power when the drive circuit 21 stops the brushless motor 22 can be adjusted. When the CPU 11 starts executing the servo lock, it first outputs a pulse signal that excites the brushless motor 22 in the reverse direction. Thereafter, a pulse signal for exciting in the forward direction is output. As described above, the CPU 11 alternately outputs the excitation pulse in the reverse rotation direction and the excitation pulse in the normal rotation direction at every fixed period T. By outputting a pulse signal for exciting the brushless motor 22 in the reverse direction at the start of servo lock, the brushless motor 22 can be quickly stopped at a predetermined stop position. Then, the state where the brushless motor 22 is stopped at the stop position is maintained by alternately outputting the excitation pulse in the forward direction and the excitation pulse in the reverse direction.

  Here, the excitation pulse in the reverse direction output first by the CPU 11 is set as the minimum duty capable of stopping the rotor 24. In other words, the rotor 24 is stopped instantaneously while preventing reverse rotation of the brushless motor 22 by outputting the excitation pulse with the minimum duty. However, when the rotor 24 is suddenly stopped, inertia acts on the rotor 24. In order to cancel this inertia, the CPU 11 alternately outputs an excitation pulse in the reverse direction and an excitation pulse in the forward direction. In the second and subsequent cycles, the duty of the servo lock signal is attenuated with the passage of time to hold the rotor 24 at the position where the rotor 24 is stopped, and when a predetermined time has elapsed from the start of the servo lock, the servo lock signal is output. finish.

  As described above, in this embodiment, when the control unit 10 stops the brushless motor 22, the rotor 24 is stopped by executing the servo lock at the position where the magnetic resistance is substantially minimum. It is possible to increase the rotational speed according to the operation map information 14.

  FIG. 7 is a diagram illustrating an example of an actual operation state of the brushless motor 22 when the sheet is continuously conveyed in the image processing apparatus. When the controller 10 stops the brushless motor 22, the servo lock described above is executed every time, and the rotor 24 is stopped at a position where the magnetic resistance is substantially minimum. It is possible to control the rotation speed of the brushless motor 22 so as to substantially match the map information 14. That is, when starting up the brushless motor 22, the rotational speed can be quickly increased according to the operation map information 14, so that it is possible to suppress the positional deviation of the paper conveyed in the image processing apparatus. Become.

  On the other hand, in the control method as in the present embodiment, when the brushless motor 22 is stopped, the rotor 24 is forcibly stopped at a position where the magnetic resistance is substantially minimum. There is a possibility that the timing specified in the information 14 is slightly deviated. That is, the CPU 11 predicts the timing at which the rotor 24 becomes the stop position described above based on the position detection signal from the encoder 31 after the rotation speed of the brushless motor 22 becomes equal to or less than the rotation speed N1 that can be stopped. Since the servo lock is executed at the timing, the servo lock may be executed before and after the stop timing defined in the operation map information 14. Therefore, as indicated by the hatched region R1 in FIG. 7, when the brushless motor 22 is stopped, the actual stop timing may be different from the operation map information 14, and a slight deviation may occur.

  Next, FIG. 8 is a diagram illustrating an example of an actual operation state of the brushless motor 22 when the brushless motor 22 is stopped without performing servo lock as a comparative example with the present embodiment. When the servo lock described above is not performed when the brushless motor 22 is stopped and the motor is stopped at the stop timing defined in the operation map information 14, the positional relationship between the rotor 24 and the stator 23 is as shown in FIG. There is a possibility of stopping in the positional relationship as shown in. In this case, when the brushless motor 22 is activated in order to continuously convey the paper in the image processing apparatus, the rotation speed of the brushless motor 22 does not rise immediately after the activation starts, and a certain time lag ΔT until the rotation speed starts increasing. Will occur. Due to this time lag ΔT, the operation state of the brushless motor 22 is different from the operation map information 14 as indicated by the hatched region R2 in FIG. In other words, this time lag ΔT causes a delay in the paper transport position, and it becomes impossible to accurately form an image at a predetermined position on the paper and read an accurate image from the predetermined position on the paper. there is a possibility.

  Here, comparing the area of the hatched area R1 in FIG. 7 with the area of the hatched area R2 in FIG. 8, the area of the hatched area R2 in FIG. 8 is large and the positional deviation of the sheet increases, whereas in FIG. The area of the hatched area R1 is small, and the positional deviation of the sheet is not so large. In particular, the shift indicated by the hatched area R1 in FIG. 7 is a shift that occurs when the brushless motor 22 is stopped, and it is considered that the sheet conveyance is completed when the brushless motor 22 is stopped. The amount of deviation shown is not a big problem.

  As described above, the motor control device 1 according to the present embodiment can control the position of the rotor 24 by a simple control method as compared with the conventional vector control, and can be realized at low cost. When the brushless motor 22 is stopped, the rotor 24 can be quickly stopped at a predetermined stop position, and when the brushless motor 22 is started, the rotor 24 can be quickly started. Therefore, such a motor control device 1 is particularly suitable as a drive source for the paper transport mechanism in the image processing apparatus.

  When the motor control device 1 as described above is incorporated in the paper transport mechanism of the image processing device, the position of the rotor 24 may not be at the stop position (for example, point A) when the image processing device is turned on. In addition, there is a possibility that the position of the rotor 24 is not at the stop position (for example, point A) described above even after a paper jam occurs in the image processing apparatus and the operation of removing the jammed paper is performed. Therefore, when the image processing apparatus is turned on, or when a paper jam occurs and the paper jam is resolved, the CPU 11 performs a preliminary drive for independently driving the brushless motor 22 without carrying the paper, and the rotor 24. Is in a state of being stopped at the aforementioned stop position (for example, point A). Thereafter, when the CPU 11 receives a paper conveyance command from the main controller of the image processing apparatus, the CPU 11 starts the paper conveyance drive of the brushless motor 22 accompanied by the paper conveyance according to the operation map information 14. Hereinafter, the operation of the CPU 11 will be described.

  9 to 11 are flowcharts illustrating an example of a processing sequence performed by the CPU 11. This processing sequence is started when the image processing apparatus is turned on.

  When this process is started, the CPU 11 performs motor drive control as preliminary drive as shown in FIG. 9 (step S1). By this preliminary drive, the rotor 24 is stopped at the position where the magnetic resistance is substantially minimum as described above. Next, the CPU 11 stands by until a paper conveyance command is issued from the main controller (step S2). When a paper transport command is received (YES in step S2), motor drive control is performed as a paper transport drive (step S3). By this paper conveyance drive, the paper conveyance mechanism of the image processing apparatus is operated, and the paper is conveyed.

  When paper conveyance is started in the image processing apparatus, the CPU 11 sequentially monitors whether or not there is a paper jam (step S4). If there is no paper jam (NO in step S4), the CPU 11 continues the paper transport drive and returns to a state of waiting for the next paper transport command (step S2). On the other hand, if there is a paper jam (YES in step S4), the CPU 11 interrupts the paper conveyance drive and waits until the paper jam is cleared (step S5). When the paper jam is eliminated (YES in step S5), the process returns to step S1, and motor drive control as a preliminary drive is executed in order to stop the rotor 24 at a position where the magnetic resistance is substantially minimum.

  Next, FIG. 10 and FIG. 11 are flowcharts showing a detailed processing sequence of motor drive control (steps S1 and S3). This processing sequence is executed by the CPU 11 in parallel with the main sequence of FIG. When starting the motor drive control, the CPU 11 first reads the operation map information 14 from the ROM 13 as shown in FIG. 10 (step S11). In the case of preliminary driving, operation map information dedicated to preliminary driving may be read out.

  Then, the CPU 11 performs initial setting for setting the target rotation speed of the brushless motor 22 and the times of the start section, the steady section, and the stop section based on the operation map information 14 (step S12). As the brushless motor 22 starts to start, output of the PWM signal is started (step S13). As a result, the drive circuit 21 causes a current to flow through the stator coil of each phase of the brushless motor 22 based on the PWM signal, thereby starting the brushless motor 22.

  After starting, the CPU 11 calculates the difference between the actual rotational speed and the target value based on the position detection signal from the encoder 31 (step S14). If there is a difference (YES in step S15), the actual value is detected. It is determined whether or not the rotational position of the rotor 24 is delayed with respect to the target value (step S16). If it is delayed (YES in step S16), the CPU 11 increases the duty of the PWM signal to correct the delay with respect to the target (step S17). If the rotor 24 has advanced with respect to the target value (NO in step S16), the CPU 11 decreases the duty of the PWM signal and corrects the advance with respect to the target (step S18). Note that when the advance with respect to the target is corrected, the output of the PWM signal may be temporarily interrupted.

  Then, after starting the brushless motor 22, the CPU 11 determines whether or not the stop section specified by the operation map information 14 has been reached (step S19). If it has not yet shifted to the stop section (NO in step S19), the process returns to step S14 and the above-described processing is repeated. That is, the processes of steps S14 to S19 are repeatedly executed in the startup section and the steady section of the operation map information 14.

  On the other hand, when it shifts to a stop section (it is YES at Step S19), it progresses to the flowchart of FIG. Then, the CPU 11 calculates the difference between the actual rotational speed and the target value based on the position detection signal from the encoder 31 (step S20), and determines whether or not the rotor 24 has advanced with respect to the target value (step S20). S21). When the rotor 24 has advanced with respect to the target value (YES in step S21), the CPU 11 brakes the brushless motor 22 by outputting a brake signal (step S22). On the other hand, when the rotor 24 is behind the target value (NO in step S21), the CPU 11 turns off the brake signal and puts the brushless motor 22 into a free-run state (step S23).

  Then, it is determined whether or not the rotor 24 can be stopped (step S24). If the rotational speed has not reached the rotational speed at which it can be stopped (NO in step S24), the process returns to step S20. Further, when the rotation speed is a rotation speed that can be stopped (YES in step S24), the CPU 11 determines whether or not the current position of the rotor 24 is a stop position that substantially minimizes the magnetic resistance (step). S25). If the current position of the rotor 24 is not yet the stop position (NO in step S25), the process returns to step S20. On the other hand, when the current position of the rotor 24 is the stop position (YES in step S25), output of the servo lock signal is started (step S26). As a result, the servo lock of the brushless motor 22 is executed, and the rotor 24 stops at a stop position where the magnetic resistance is substantially minimum.

  The CPU 11 continues to output a servo lock signal whose duty gradually decreases until a predetermined time elapses thereafter (step S27). When the predetermined time elapses (YES in step S27), the CPU 11 finishes outputting the servo lock signal. . As a result, the brushless motor 22 is stopped at a position where the magnetic resistance is substantially minimum until the next startup.

  As described above, in the motor control device 1 according to the present embodiment, the rotor 24 is moved to the stator 23 based on the rotation position of the rotor 24 detected by the encoder 31 after the rotation speed of the brushless motor 22 reaches a rotation speed that can be stopped. When the predetermined stop position is reached, the servo lock is executed to stop the brushless motor 22. Such a motor control device 1 can be realized at low cost.

  When stopping the brushless motor 22, the brushless motor 22 can be stopped at a predetermined stop time while monitoring the rotational position of the rotor 24 detected by the encoder 31 based on the operation map information 14. In order to stop the brushless motor 22 by executing servo lock at a position where the magnetic resistance between the rotor 24 and the stator 23 is substantially minimum and stopping the brushless motor 22, it is necessary to stop the rotor 24 at a predetermined stop position. The time will not be long. Therefore, even when a plurality of sheets are continuously conveyed, the sheet conveyance interval can be shortened, and the conveyance efficiency can be improved. Further, every time the rotor 24 is stopped, it can be stopped at a position where the magnetic resistance between the rotor 24 and the stator 23 is substantially minimized, so that the number of rotations of the brushless motor 22 is efficiently increased at the next start-up. The next sheet can be transported promptly. As a result, it is possible to provide a drive source that can prevent misalignment of the sheet conveyed in the image processing apparatus and can accurately convey the sheet at a low cost.

(Modification)
As mentioned above, although typical embodiment regarding this invention was described, this invention is not limited to embodiment mentioned above. That is, various modifications other than the above-described embodiment can be applied to the present invention.

  FIG. 12 is a diagram showing a motor control device 1a having a configuration different from that of the motor control device 1 described above. In the motor control device 1 a of FIG. 12, the output voltage of each Hall element 25 a, 25 b, 25 c provided in the brushless motor 22 is input to the CPU 11 as a position detection signal of the rotor 24. The CPU 11 detects the position of the rotor 24 based on the output voltage of each hall element 25a, 25b, 25c, and controls the brushless motor 22 in the same manner as described above. According to such a motor control device 1a, since it is not necessary to provide the encoder 31 as in the motor control device 1 described above, it can be realized at a lower cost. The operational effects of the motor control device 1a are the same as those of the motor control device 1 described above.

  In addition, a plurality of the motor control devices 1 and 1a described above may be provided in the image processing apparatus. For example, when a paper feed motor, a conveyance motor, and a paper discharge motor are provided separately in the image processing apparatus, they may be provided as motor control devices for these motors.

1, 1a Motor control device 10 Control unit (control means)
11 CPU
12 RAM
13 ROM
14 Operation map information 20 Motor unit 21 Drive circuit 22 Brushless motor 23 Stator 24 Rotor 25a, 25b, 25c Hall element (position detection means)
31 Encoder (position detection means)

Claims (10)

A brushless motor provided as a drive source for conveying paper, and having a rotor and a stator;
Position detecting means for detecting the rotational position of the rotor in the brushless motor;
Control means for controlling the brushless motor based on the rotational position of the rotor detected by the position detecting means in each of the start section, the steady section and the stop section of the brushless motor;
With
The control means is configured such that, after the rotation speed of the brushless motor reaches a stoppable rotation speed in the stop section, the rotor is moved relative to the stator based on the rotation position of the rotor detected by the position detection means. A motor control device, wherein a servo lock is executed to stop the brushless motor when a predetermined stop position is reached.   2. The motor control device according to claim 1, wherein the predetermined stop position is a position at which a magnetic resistance between the rotor and the stator is substantially minimum.   The control means starts deceleration control so as to stop the brushless motor at a predetermined stop time in the stop section, and executes servo lock at a position where the magnetic resistance between the rotor and the stator is substantially minimum. The motor control device according to claim 2, wherein the brushless motor is stopped.   The control means executes servo lock at a timing when the rotor is at the predetermined stop position with respect to the stator before and after the predetermined stop time, and stops the brushless motor. Item 4. The motor control device according to Item 3.   The motor control apparatus according to claim 1, wherein the position detection unit is an encoder.   The control means is configured such that, after the rotation speed of the brushless motor becomes a stoppable rotation speed in the stop section, the rotor is moved to the stator with respect to the stator based on a predetermined position detection signal output from the encoder. The motor control device according to claim 5, wherein the timing of the stop position is predicted and servo lock is executed at the predicted timing.   The motor control apparatus according to claim 1, wherein the position detection unit is a Hall element.   The control means is configured such that, after the rotation speed of the brushless motor reaches a stoppable rotation speed in the stop section, the rotor is moved to the predetermined position with respect to the stator based on a position detection signal output from the Hall element. The motor control device according to claim 7, wherein the timing of the stop position is predicted, and servo lock is executed at the predicted timing.   When the control means executes servo lock, a servo lock signal in which the duty decreases with the passage of time from the minimum duty at which the rotor can be stopped is given to the brushless motor. The motor control device according to claim 1.   10. The servo lock signal given to the brushless motor when the control means executes servo lock is a signal for exciting the brushless motor in the reverse rotation direction first. The motor control apparatus described.

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