JP2018057163A - Device for controlling stepping motor and method for controlling stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for controlling a stepping motor that can reduce the occurrence of failure in start-up of a stepping motor.SOLUTION: A device 10 for controlling a stepping motor comprises a drive circuit 1, a control part, and a reference voltage variable part 3. The drive circuit 1 sets a current value of an excitation current with reference to a reference voltage Vref and supplies the excitation current to excitation phases of a stepping motor 4 in synchronization with a rectangular wave. The control part 2 gradually increases the frequency of the rectangular wave from a first frequency to a secondary frequency in a first period from when the stepping motor 4 is started up until the motor enters a steady drive state. The reference voltage variable part 3 changes the reference voltage Vref on the basis of the rectangular wave to change the current value of the excitation current. The control part 2 changes the duty ratio of the rectangular wave so that the excitation current supplied in the first period has a larger current value than that of the excitation current supplied in a second period during which the stepping motor 4 is driven in the steady drive state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a stepping motor control device and a stepping motor control method.

  Stepping motors are used for various drive sources of OA (office automation) equipment such as multifunction peripherals. For example, a stepping motor is used as a drive source for a carriage provided in a scanner or a drive source for a feed roller provided in an original conveying device (ADF) in a multi-function peripheral. Further, the stepping motor is used as a drive source of a paper feed roller that feeds paper to a paper transport path in a multifunction machine.

  By the way, there is a possibility that the stepping motor will step out if it is rotated at the target rotational speed from the time of activation. Therefore, generally, after starting the rotation of the stepping motor at a rotation speed lower than the target rotation speed, the rotation speed of the stepping motor is gradually increased to the target rotation speed (see, for example, Patent Document 1).

JP-A-8-308293

  However, if the stator excitation phase excited when the stepping motor starts up and the rotor magnetized phase are misaligned, the rotational speed is gradually increased to the target rotational speed depending on the degree of the deviation. Even if the control is executed, the rotor may vibrate and step out, and the stepping motor may not be started.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a stepping motor control device and a stepping motor control method capable of suppressing the occurrence of a starting failure of the stepping motor.

  The stepping motor control device of the present invention includes a drive circuit, a control unit, and a reference voltage variable unit. The drive circuit sets the current value of the excitation current with reference to a reference voltage, and supplies the excitation current to each excitation phase of the stepping motor according to a predetermined excitation mode in synchronization with the rectangular wave. The control unit gradually increases the frequency of the rectangular wave from the first frequency to the second frequency in a first period from when the stepping motor is activated until the steady driving state is achieved. The reference voltage variable unit changes the reference voltage based on the rectangular wave to change the current value of the excitation current. Further, the control is performed so that the excitation current supplied in the first period has a larger current value than the excitation current supplied in the second period in which the stepping motor is driven in the steady drive state. The section changes the duty ratio of the rectangular wave.

  The stepping motor control method of the present invention includes the following steps. A step of supplying an excitation current to each excitation phase of the stepping motor in accordance with a predetermined excitation mode in synchronization with a rectangular wave in a first period from when the stepping motor is activated until it enters a steady drive state. Supplying the excitation current to the respective excitation phases according to the predetermined excitation mode in synchronization with the rectangular wave during a second period in which the stepping motor is driven in the steady drive state. The exciting current supplied in the first period has a current value larger than the exciting current supplied in the second period.

  According to the present invention, it is possible to suppress the start-up failure of the stepping motor.

It is a figure which shows the structure of the control apparatus of the stepping motor which concerns on Embodiment 1 of this invention. (A) is a wave form diagram which shows the waveform of the clock signal which concerns on Embodiment 1 of this invention. (B) is a figure which shows the frequency of the clock signal which concerns on Embodiment 1 of this invention. (C) is a wave form diagram which shows the waveform of the reference voltage which concerns on Embodiment 1 of this invention. (D) is a wave form diagram which shows the waveform of the exciting current which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the control apparatus of the stepping motor which concerns on Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a diagram illustrating a configuration of a stepping motor control apparatus according to the first embodiment. As shown in FIG. 1, the stepping motor control device 10 according to the present embodiment includes a motor driver 1 (an example of a drive circuit), a control unit 2, and a reference voltage variable unit 3.

  The motor driver 1 supplies an excitation current to each excitation phase of the stepping motor 4 according to a predetermined excitation mode in synchronization with a clock signal (an example of a rectangular wave) supplied from the control unit 2. The stepping motor 4 rotates (drives) in synchronization with the clock signal in accordance with the supply of the excitation current by the motor driver 1. The motor driver 1 sets the current value of the excitation current with reference to the reference voltage Vref.

  The control unit 2 can include, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Further, the control unit 2 may include a storage device such as a RAM (Random Access Memory), a ROM (Read Only Memory), and an HDD (Hard Disk Drive). The control unit 2 performs various processes such as numerical calculation, information processing, and device control based on the control program and setting information stored in the storage device, and controls the operation of the control device 10 for the stepping motor.

  In the present embodiment, the control unit 2 generates a clock signal, a rotation direction command signal, and an excitation mode setting signal. The clock signal, the rotation direction command signal, and the excitation mode setting signal are input to the motor driver 1.

  The rotation direction command signal is a signal that commands the rotation direction of the stepping motor 4. The motor driver 1 rotates the stepping motor 4 forward or backward based on the rotation direction command signal. Specifically, when the rotation direction command signal indicates normal rotation, the motor driver 1 supplies an excitation current to each excitation phase of the stepping motor 4 so that the stepping motor 4 rotates forward. On the other hand, when the rotation direction command signal indicates reverse rotation, the motor driver 1 supplies an excitation current to each excitation phase of the stepping motor 4 so that the stepping motor 4 rotates reversely.

  The excitation mode setting signal is a signal for setting the excitation mode of the stepping motor 4. For example, one of the 1-phase excitation mode, 2-phase excitation mode, 1-2-phase excitation mode, W1-2-phase excitation mode, 2W1-2-phase excitation mode, and 4W1-2-phase excitation mode according to the excitation mode setting signal Two excitation modes are set for the motor driver 1. The motor driver 1 supplies an excitation current to each excitation phase of the stepping motor 4 according to the set excitation mode.

  In the present embodiment, the control unit 2 supplies a clock signal to the motor driver 1 during a period in which the stepping motor 4 is operated. In other words, the clock signal is not supplied to the motor driver 1 during the period in which the stepping motor 4 is stopped (hereinafter referred to as the stop period), and the clock signal is supplied to the motor driver 1 by the stepping motor 4. It starts at startup.

  Further, in the present embodiment, the control unit 2 gradually increases the frequency of the clock signal from the first frequency to the second frequency in the first period from when the stepping motor 4 is activated until it enters the steady drive state. Then, the control unit 2 maintains the frequency of the clock signal at the second frequency in the second period in which the stepping motor 4 is driven (rotated) in the steady driving state. In addition, the control unit 2 gradually decreases the frequency of the clock signal from the second frequency to the third frequency in the third period until the stepping motor 4 is stopped from the steady driving state. Note that the first frequency, the second frequency, and the third frequency are stored in the storage device in advance.

  The second frequency is a frequency for rotating the stepping motor 4 at a target rotation speed. Therefore, when the stepping motor 4 is activated, the stepping motor 4 first starts rotating at a rotation speed corresponding to the first frequency (rotation speed lower than the target rotation speed). Thereafter, the rotation speed of the stepping motor 4 gradually increases to the target rotation speed. When the rotational speed of the stepping motor 4 reaches the target rotational speed, the frequency of the clock signal is maintained at the second frequency. Therefore, the stepping motor 4 rotates at the target rotation speed during steady driving. By this control, step-out is less likely to occur when the stepping motor 4 is started. Therefore, it is possible to suppress the occurrence of starting failure of the stepping motor.

  On the other hand, when the stepping motor 4 stops, the rotation speed of the stepping motor 4 gradually decreases from the target rotation speed to the rotation speed corresponding to the third frequency (rotation speed lower than the target rotation speed). This control makes it easy to stop the rotor at a predetermined stop position when the stepping motor 4 is stopped. In other words, the positions of the excitation phase of the stator excited when the stepping motor 4 is activated and the magnetized phase of the rotor are difficult to shift. Alternatively, at least the degree of deviation between the excitation phase of the stator excited when the stepping motor 4 is started and the magnetization phase of the rotor can be reduced.

  Hereinafter, the first period may be referred to as a slow-up period, the second period may be referred to as a steady drive period, and the third period may be referred to as a slow-down period.

  The reference voltage variable unit 3 changes the reference voltage Vref based on the clock signal to change the current value of the excitation current. In the present embodiment, the reference voltage variable unit 3 includes a first resistor 31 to a fifth resistor 35, a PNP bipolar transistor 36 (an example of a switch element), and a capacitor 37.

  Specifically, the emitter of the PNP bipolar transistor 36 is connected to the power supply line, and a clock signal is input to the base of the PNP bipolar transistor 36 via the first resistor 31. Therefore, the PNP-type bipolar transistor 36 repeats turn-on and turn-off according to the clock signal. For this reason, the waveform of the collector current of the PNP bipolar transistor 36 becomes a pulsating current.

  The collector of the PNP bipolar transistor 36 is connected to one end of the second resistor 32, and the collector current of the PNP bipolar transistor 36 is converted into a voltage by the second resistor 32.

  The other end of the second resistor 32 is connected to one end of the fifth resistor 35 through a connection point a between the third resistor 33 and the fourth resistor 34. The third resistor 33 and the fourth resistor 34 constitute a voltage dividing circuit. That is, one end of the third resistor 33 is connected to the power supply line, the other end of the third resistor 33 is connected to one end of the fourth resistor 34, and the other end of the fourth resistor 34 is grounded. Therefore, a voltage obtained by superimposing a pulse voltage corresponding to the collector current of the PNP bipolar transistor 36 on the DC voltage generated at the connection point a by the voltage dividing circuit is applied to one end of the fifth resistor 35.

  The fifth resistor 35 constitutes a smoothing circuit 38 together with the capacitor 37. The smoothing circuit 38 smoothes the output of the PNP bipolar transistor 36. In the present embodiment, a voltage obtained by superimposing a voltage corresponding to the collector current of the PNP bipolar transistor 36 on the DC voltage generated at the connection point a is smoothed by the smoothing circuit 38. The output of the smoothing circuit 38 is input to the motor driver 1 as a reference voltage Vref.

  With the configuration of the reference voltage variable unit 3 described above, the reference voltage Vref changes based on the clock signal. Specifically, the reference voltage Vref changes according to changes in the frequency and duty ratio of the clock signal. Then, when the reference voltage Vref changes, the current value of the exciting current changes.

  The control unit 2 of the present embodiment changes the duty ratio of the clock signal in addition to the frequency of the clock signal. Specifically, the control unit 2 changes the duty ratio of the clock signal so that the excitation current supplied during the slow-up period has a larger current value than the excitation current supplied during the steady drive period. Further, the control unit 2 changes the duty ratio of the clock signal so that the excitation current supplied during the slow-down period has a larger current value than the excitation current supplied during the steady drive period.

  Hereinafter, the excitation current supplied during the slow-up period is referred to as a first excitation current, the excitation current supplied during the steady drive period is referred to as a second excitation current, and the excitation current supplied during the slow-down period is referred to as a third excitation current. Sometimes referred to as excitation current.

  Subsequently, the operation of the stepping motor control device 10 (stepping motor control method) will be described with reference to FIGS. FIG. 2A is a waveform diagram showing the waveform of the clock signal. Specifically, FIG. 2A shows a waveform of a clock signal input to the motor driver 1 from when the stepping motor 4 is started to when it is stopped. FIG. 2B is a diagram showing the frequency of the clock signal. Specifically, FIG. 2B shows the frequency of the clock signal input to the motor driver 1 from when the stepping motor 4 is activated until when it is stopped. FIG. 2C is a waveform diagram showing a waveform of the reference voltage Vref. Specifically, FIG. 2C shows a waveform of the reference voltage Vref that is generated from when the stepping motor 4 is started to when it is stopped. FIG. 2D is a waveform diagram showing the waveform of the excitation current. Specifically, FIG. 2D shows a waveform of the excitation current supplied from when the stepping motor 4 is activated until when it is stopped. The activation of the stepping motor 4 includes activation when the stepping motor 4 starts reverse rotation.

  The vertical axis in FIG. 2 (b) indicates the frequency of the clock signal, the vertical axis in FIG. 2 (c) indicates the voltage value of the reference voltage Vref, and the vertical axis in FIG. 2 (d) indicates the current value of the excitation current. . Each horizontal axis in FIG. 2B to FIG. 2D indicates time. FIG. 2C shows a waveform of the reference voltage Vref based on the voltage value of the DC voltage generated at the connection point a by the voltage dividing circuit.

  As shown in FIGS. 2A to 2D, in this embodiment, a clock signal is input to the motor driver 1 from the start of the start-up period to the end of the slow-down period. The stepping motor 4 rotates in response to (in synchronization with) the rising edge of the clock signal.

  The frequency of the clock signal gradually increases from the start of the start-up period to the start of the steady drive period. As a result, the rotation speed of the stepping motor 4 gradually increases to the target rotation speed. By this control, step-out is less likely to occur when the stepping motor 4 is started.

  On the other hand, the duty ratio of the clock signal is set to a value larger than 50% at the start of the startup period. In this embodiment, the duty ratio of the clock signal is set to 80% at the start of the startup period. Further, during the period when the duty ratio of the clock signal is set to 80%, the voltage value of the reference voltage Vref increases to a value larger than the voltage value of the reference voltage Vref generated during the steady driving period. As a result, the current value of the first excitation current is set to a value larger than the current value of the second excitation current. Hereinafter, the reference voltage Vref generated during the steady drive period may be referred to as a steady-state reference voltage Vref.

  After the current value of the first excitation current is set to a value larger than the current value of the second excitation current, the duty ratio of the clock signal changes from 80% to 50%. As a result, the voltage value of the reference voltage Vref is maintained as a value larger than the voltage value of the steady-state reference voltage Vref, and the current value of the first excitation current is larger than the current value of the second excitation current. Maintained.

  Therefore, an excitation current having a current value larger than the excitation current supplied in the steady drive period flows during the slow-up period. In other words, a torque larger than that in the steady driving period is generated in the slow-up period.

  In the present embodiment, the duty ratio of the clock signal is set to a value smaller than 50% before the steady driving period starts. And it is returned to 50% at the start of the steady drive period. As a result, before the steady drive period starts, the voltage value of the reference voltage Vref decreases and the current value of the first excitation current decreases. In the steady drive period, the voltage value of the reference voltage Vref is maintained as the voltage value after the decrease, and the current value of the excitation current is also maintained as the current value after the decrease. In the present embodiment, the duty ratio of the clock signal is set to 20% before the steady driving period starts.

  When stopping the stepping motor 4, the frequency of the clock signal is gradually decreased. By this control, the rotation speed of the stepping motor 4 gradually decreases from the target rotation speed. Then, the control unit 2 stops supplying the clock signal to the motor driver 1 in a state where the rotation speed of the stepping motor 4 has decreased to a rotation speed lower than the target rotation speed. Thus, by reducing the rotation speed of the stepping motor 4 and then stopping the supply of the clock signal, the rotor can be easily stopped at a predetermined stop position when the stepping motor 4 is stopped.

  On the other hand, the duty ratio of the clock signal is set to a value larger than 50% at the start of the slowdown period. As a result, the voltage value of the reference voltage Vref increases, and the current value of the third excitation current is set to a larger current value than the current value of the second excitation current. In the present embodiment, the duty ratio of the clock signal is set to 80% at the start of the slowdown period.

  Thereafter, the duty ratio of the clock signal changes from 80% to 50%. As a result, the voltage value of the reference voltage Vref is maintained larger than the voltage value of the steady-state reference voltage Vref, and the current value of the third excitation current remains larger than the current value of the second excitation current. Maintained.

  Therefore, an excitation current having a current value larger than the excitation current supplied in the steady drive period flows during the slow-down period. In other words, a torque larger than that in the steady driving period is generated in the slowdown period.

  In this embodiment, before the supply of the clock signal to the motor driver 1 is stopped, the duty ratio of the clock signal is set to a value smaller than 50%. In this embodiment, the duty ratio of the clock signal changes to 20%. Thus, by setting the duty ratio of the clock signal to a value lower than 50%, the voltage value of the reference voltage Vref is lowered before the supply of the clock signal to the motor driver 1 is stopped. The current value of the current decreases. Therefore, the stepping motor 4 can be stopped while the current value of the excitation current is reduced. In other words, the stepping motor 4 can be stopped with the torque reduced. This control facilitates stopping the rotor at a predetermined stop position. That is, when the rotation of the stepping motor 4 is stopped while the torque is large, a step-out due to the vibration of the rotor is likely to occur. That is, there is a possibility that the rotor cannot be stopped at a predetermined stop position. On the other hand, according to the present embodiment, since the rotation of the stepping motor 4 is stopped in a state where the torque is reduced, the rotor can be easily stopped at a predetermined stop position.

  As described above, according to the present embodiment, the duty ratio of the clock signal is controlled so that the reference voltage Vref having a voltage value larger than the steady-state reference voltage Vref is generated when the stepping motor 4 is started. Specifically, the duty ratio of the clock signal in the slow-up period is set to a value higher than the duty ratio of the clock signal in the steady driving period. As a result, the current value of the first excitation current becomes larger than the current value of the second excitation current, and a large torque can be generated when the stepping motor 4 is started.

  Therefore, according to this embodiment, even when the positions of the excitation phase of the stator excited when the stepping motor 4 is started and the magnetized phase of the rotor are greatly deviated, the stepping motor 4 is started. Defects are unlikely to occur. That is, if the excitation phase of the stator that is excited when the stepping motor is started and the magnetized phase of the rotor are greatly deviated, if the torque is insufficient, the stepping motor may start up poorly. That is, there is a possibility that the stepping motor 4 cannot be started. On the other hand, according to the present embodiment, since a large torque can be generated when the stepping motor 4 is started, a starting failure of the stepping motor 4 due to insufficient torque is unlikely to occur.

  According to the present embodiment, when the stepping motor 4 is stopped, the duty ratio of the clock signal is controlled so that the reference voltage Vref having a voltage value larger than the steady-state reference voltage Vref is generated. Specifically, the duty ratio of the clock signal in the slow-down period is set to a value higher than the duty ratio of the clock signal in the steady driving period. As a result, the current value of the third excitation current becomes larger than the current value of the second excitation current, and a large torque can be generated when the stepping motor 4 is stopped.

  Therefore, according to this embodiment, the stop position of the rotor of the stepping motor 4 is not easily deviated from the target stop position. As a result, the positions of the excitation phase of the stator that is excited when the stepping motor 4 is activated and the magnetization phase of the rotor are difficult to shift. Alternatively, at least the degree of deviation between the excitation phase of the stator excited when the stepping motor 4 is started and the magnetization phase of the rotor can be reduced.

  Further, according to the present embodiment, the current value of the second excitation current can be made smaller than the current value of the first excitation current, and the heat generation of the stepping motor 4 during the steady drive period can be suppressed. When the stepping motor 4 is driven, an inertial force is applied to the rotor of the stepping motor 4. Therefore, in the steady drive period, the stepping motor 4 can be rotated at the target rotational speed without generating a large torque.

  In addition, according to the present embodiment, the excitation current (torque) can be increased or decreased by making the reference voltage Vref variable with a simple configuration.

  In the present embodiment, the motor driver 1 supplies the excitation current to the stepping motor 4 even during the stop period. Therefore, it is possible to suppress changes in the position of the excitation phase of the stator and the position of the magnetization phase of the rotor during the stop period.

  In addition, if the current value of the excitation current cannot be changed and the current value of the excitation current is set to a large value so that the stepping motor starts reliably, the current value of the excitation current supplied during the steady drive period also increases. Become. Therefore, in this case, it is necessary to use a stepping motor having a large heat capacity. In addition, it is necessary to provide a fan for cooling the stepping motor. On the other hand, according to the present embodiment, the current value of the excitation current supplied during the steady drive period can be reduced. Therefore, it is not necessary to use a stepping motor having a large heat capacity. Moreover, it is not necessary to provide a fan.

  In general, when switching the excitation mode, phase switching is performed to match the phases of the stator excitation phase and the rotor magnetization phase excited when the stepping motor is started. As a result, when switching the excitation mode, a waiting time for phase switching occurs. On the other hand, according to this embodiment, since the torque can be increased by increasing the current value of the exciting current when the stepping motor 4 is started, the stepping motor 4 can be started without performing phase switching. . Therefore, the waiting time for phase switching can be reduced.

  In general, when switching the rotation direction of the stepping motor, the excitation phase of the stator that is excited when the reverse rotation of the stepping motor is started, and the magnetization phase of the rotor There is a waiting time for matching the phases. On the other hand, according to the present embodiment, the torque value can be increased by increasing the current value of the exciting current at the start of reverse rotation of the stepping motor 4 (at the time of starting). Therefore, the stepping motor 4 can be started without matching the phases of the stator excitation phase excited at the start of reverse rotation of the stepping motor and the magnetized phase of the rotor. Therefore, the waiting time for switching the rotation direction of the stepping motor can be reduced.

[Embodiment 2]
Subsequently, Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, unlike the first embodiment, the motor driver 1 does not supply the exciting current to the stepping motor 4 during the stop period. Hereinafter, regarding the second embodiment, matters different from the first embodiment will be described, and description of the same matters as the first embodiment will be appropriately omitted.

  FIG. 3 is a diagram illustrating a configuration of the stepping motor control device 10 according to the second embodiment. As shown in FIG. 3, the stepping motor control device 10 according to the present embodiment does not include the third resistor 33 unlike the stepping motor control device 10 according to the first embodiment (see FIG. 1). Therefore, in this embodiment, the DC voltage from the power supply line is not supplied to the connection point a. In other words, it corresponds to the collector current of the PNP bipolar transistor 36 at the connection point a only during the period in which the control unit 2 supplies the clock signal to the motor driver 1 (hereinafter referred to as the clock signal supply period). A pulse voltage is supplied. Therefore, the reference voltage Vref is input to the motor driver 1 only during the clock signal supply period. As a result, the excitation current is supplied to the stepping motor 4 only during the clock signal supply period.

  The second embodiment has been described above with reference to FIG. According to the present embodiment, the excitation current is supplied to the stepping motor 4 only during the clock signal supply period. In other words, the supply of the excitation current to the stepping motor 4 is stopped during the stop period. Therefore, according to this embodiment, the heat generation of the stepping motor 4 can be suppressed.

  Also in the present embodiment, as described with reference to FIG. 2, when the stepping motor 4 is stopped, the frequency of the clock signal is gradually decreased. Therefore, the supply of the excitation current to the stepping motor 4 can be stopped in a state where the rotation speed of the stepping motor 4 has decreased to a rotation speed lower than the target rotation speed. Thus, by reducing the rotation speed of the stepping motor 4 and then stopping the supply of excitation current, the rotor can be easily stopped at a predetermined stop position when the stepping motor 4 is stopped.

  In addition, as one of the control methods for the stepping motor, there is a control method in which the excitation current is not supplied during the stop period of the stepping motor and the preliminary excitation current is supplied before starting the stepping motor. Specifically, the preliminary excitation current matches the excitation phase of the stator that is excited when the stepping motor is started and the magnetized phase of the rotor. That is, when a general motor driver that does not execute control to stop the supply of excitation current after reducing the rotation speed of the stepping motor is used, the stepping motor is not allowed to flow during the stepping motor stop period. May stop at a position deviating from a predetermined stop position. Therefore, there is a possibility that the position of the excitation phase of the stator that is excited when the stepping motor is activated and the magnetization phase of the rotor are greatly shifted, and step-out occurs. For this reason, for the purpose of preventing step-out, phase matching is performed before starting the stepping motor. However, this control method requires time for phase matching before starting the stepping motor, and it takes time to start the stepping motor. On the other hand, according to this embodiment, since the torque can be increased by increasing the current value of the exciting current when the stepping motor 4 is started, the stepping motor 4 can be started without performing phase matching. . Therefore, the time required for phase matching can be reduced. In other words, the time required for the rotation speed of the stepping motor 4 to reach the target rotation speed can be shortened.

  In the present embodiment, the configuration not including only the third resistor 33 has been described. However, in addition to the third resistor 33, a configuration not including the fourth resistor 34 may be used.

  The stepping motor control device 10 and the stepping motor control method according to the embodiment of the present invention have been described above with reference to the drawings. The stepping motor control device 10 and the stepping motor control method described in the embodiment of the present invention can be used for controlling stepping motors used for various drive sources of OA equipment such as multifunction peripherals. For example, in the multifunction device, the stepping motor control device 10 described in the embodiment of the present invention is used to control a stepping motor used as a driving source of a carriage included in the scanner and a driving source of a paper feed roller included in the document conveying device. In addition, a stepping motor control method can be applied. Further, in the multifunction machine, the stepping motor control device 10 described in the embodiment of the present invention and the control of the stepping motor are used to control the stepping motor used as a drive source of the paper feed roller that feeds the paper to the paper transport path. The method can be applied.

  In addition, this invention is not restricted to said embodiment, It is possible to implement in a various aspect in the range which does not deviate from the summary.

  For example, in the embodiment according to the present invention, the reference voltage variable unit 3 includes the PNP bipolar transistor 36 as a switching element, but the switching element is not limited to the PNP bipolar transistor 36. For example, the reference voltage variable unit 3 may include an NPN bipolar transistor instead of the PNP bipolar transistor 36. Alternatively, the reference voltage variable unit 3 may include a MOSFET as a switch element.

  In the embodiment according to the present invention, the duty ratio of the clock signal is set to 50% during the steady driving of the stepping motor 4, but the present invention is not limited to this. When the stepping motor 4 is driven, an inertial force is applied to the rotor of the stepping motor 4, so that the stepping motor 4 can be rotated at the target rotational speed without generating a large torque during the steady driving period. Therefore, the duty ratio of the clock signal during steady driving of the stepping motor 4 may be set to a value lower than 50%, and may be set to 30% or 20%, for example.

  In the embodiment according to the present invention, the current value of the excitation current is increased during the slow-down period, but the present invention is not limited to this. In the slow-down period, control for increasing the excitation current may not be performed.

  The present invention is useful for a control device and a control method for a stepping motor used for a drive source of an electronic device such as a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Motor driver 2 Control part 3 Reference voltage variable part 4 Stepping motor 10 Stepping motor control device

Claims (10)

A drive circuit that sets a current value of an excitation current with reference to a reference voltage, and supplies the excitation current according to a predetermined excitation mode to each excitation phase of the stepping motor in synchronization with a rectangular wave;
A control unit that gradually increases the frequency of the rectangular wave from the first frequency to the second frequency in a first period from when the stepping motor is activated until it enters a steady drive state;
A reference voltage variable unit that changes the reference voltage based on the rectangular wave and changes a current value of the excitation current;
The control unit is configured so that the excitation current supplied in the first period has a current value larger than the excitation current supplied in the second period in which the stepping motor is driven in the steady drive state. A stepping motor control device for changing a duty ratio of the rectangular wave. The reference voltage variable unit includes:
A switching element that repeats turn-on and turn-off according to the rectangular wave;
A smoothing circuit for smoothing the output of the switch element,
The stepping motor control device according to claim 1, wherein an output of the smoothing circuit is referred to the drive circuit as the reference voltage.   The stepping motor control device according to claim 2, wherein the switch element is a bipolar transistor.   4. The stepping according to claim 1, wherein a duty ratio of the rectangular wave at the start of the first period is larger than a duty ratio of the rectangular wave at the end of the first period. Motor control device.   5. The stepping motor according to claim 4, wherein a duty ratio of the rectangular wave at the start of the first period is greater than 50% and a duty ratio of the rectangular wave at the end of the first period is less than 50%. Control device.   The stepping motor control device according to any one of claims 1 to 5, wherein a duty ratio of the rectangular wave in the second period is 50% or less. The controller is
In the third period until the stepping motor is stopped from the steady driving state, the frequency of the rectangular wave is gradually decreased from the second frequency to the third frequency,
The duty ratio of the rectangular wave is changed so that the excitation current supplied in the third period has a larger current value than the excitation current supplied in the second period. The stepping motor control device according to any one of claims 6 to 6.   The stepping motor control device according to claim 7, wherein a duty ratio of the rectangular wave at the start of the third period is greater than a duty ratio of the rectangular wave at the end of the third period.   The stepping motor according to claim 8, wherein a duty ratio of the rectangular wave at the start of the third period is greater than 50% and a duty ratio of the rectangular wave at the end of the third period is less than 50%. Control device. Supplying an excitation current to each excitation phase of the stepping motor in accordance with a predetermined excitation mode in synchronization with a rectangular wave during a first period from when the stepping motor is activated until it enters a steady drive state;
Supplying the excitation current to each of the excitation phases according to the predetermined excitation mode in synchronization with the rectangular wave during a second period in which the stepping motor is driven in the steady drive state.
The stepping motor control method, wherein the excitation current supplied in the first period has a larger current value than the excitation current supplied in the second period.

Images