JP7352967B2 - drive device - Google Patents

Description

The present invention relates to a driving device for driving a stepping motor.

Generally, a drive device (driver) is used to drive a stepping motor. When driving a stepping motor, command pulses (external command pulses) are input to the drive device from the outside, and the input command pulses are counted in the drive device. In addition, the drive device applies a rectangular wave voltage to the stepping motor to excite the motor coil (hereinafter sometimes abbreviated as a coil) of the stepping motor, and also sequentially switches the excited coils to generate command pulses. Rotate the stepping motor at a speed corresponding to the count value.

As stepping motor drive devices, two types of drive devices with different constant current control methods are known.
One drive device performs output stage chopper type constant current control. This output stage chopper type drive device generates an error signal between the detected current detected as the current flowing through the coil and a reference current value, and drives by comparing the level of the error signal with the level of a predetermined sawtooth wave. By chopping the output stage section (switching element) of the device, the current flowing through the coil is controlled to a constant magnitude. Therefore, in the output stage chopper type drive device, both step drive pattern control and constant current control are performed in the output stage section.

Note that in the output stage chopper type drive device, the voltage of the power source input to the drive device is directly applied to the stepping motor (motor coil). For this reason, for example, if the voltage input to the drive device is 24V DC, even when the stepping motor is stopped and held at a predetermined angle, a voltage of 24V is applied to the motor coil.

The other drive device performs constant current control in which the current flowing through the coil is controlled to a constant magnitude by adjusting the motor drive voltage DV input to the motor coil. Constant current control performed by adjusting the motor drive voltage DV in this way is called DV-type constant current control, and a drive device that performs DV-type constant current control is called a DV-type drive device. . An example of this DV type drive device is described in Japanese Patent Laid-Open No. 2008-61439 (Patent Document 1).

For example, as shown in FIG. 18, the drive device 100 of Patent Document 1 is connected to a five-phase stepping motor 101. This drive device 100 includes an excitation pattern output circuit 102 that receives an external command pulse CWP or CCWP and outputs an excitation pattern for exciting a coil, a plurality of power elements (switching elements) 106, and an excitation pattern output circuit 102. It has a power element drive circuit 103 that controls ON/OFF of the power element 106 according to excitation pattern data output from the power element drive circuit 103, and a constant current control section that performs DV type constant current control.

The excitation pattern output circuit 102 includes an address counter (electrical angle position management) 102a, an excitation period counter (driving time management, excitation pattern switching command) 102b, and a memory 102c. The memory 102c stores excitation pattern data and output time data.

The address counter 102a receives external command pulses CWP and CCWP and manages information on the electrical angle position (excitation address) of the motor rotor of the five-phase stepping motor 101. The excitation period counter 102b reads an address (electrical angle position information) from the address counter 102a every unit excitation period, and also reads excitation pattern data corresponding to the address and its output time data from the memory 102c. Further, in accordance with the read excitation pattern data and output time data, the designation of each excitation pattern and data on the excitation time (time ratio) of the excitation pattern are output to the power element drive circuit 103.

The power element drive circuit 103 receives excitation pattern data as described above from the excitation pattern output circuit 102, and controls the voltage applied to each power element 106. As a result, a current is applied to the coils of the stepping motor 101 to excite them, and the excitation coils are sequentially switched. Thereby, the stepping motor 101 is driven in steps.

The constant current control section of the drive device 100 includes a first capacitor C1 that smoothes the voltage of the input power supply, a control switching element 107 that increases or decreases the motor drive voltage by switching ON/OFF, and a control switching element 107. A PWM constant current control circuit 104 that drives ON/OFF of the motor, a current detection resistor 105 that detects the current flowing through the motor coil, and a choke coil L1 that smoothes the intermittent voltage generated by switching the control switching element 107. It has a second capacitor C2 and a diode D1 that bypasses the electromotive force generated by the choke coil L1.

This constant current control section generates the difference between the current flowing through the motor coil and a reference current as an error signal, and turns ON/OFF the control switching element 107 based on the error signal, thereby inputting the current to the coil. Adjust the motor drive voltage. This keeps the current flowing through the motor coil constant.

Although such a DV type drive device 100 requires more circuits than the output stage chopper type drive device described above, the power element drive circuit 103 only performs pattern control for step drive. be able to. Therefore, the DV type drive device 100 can smoothly perform microstep drive with higher resolution than an output stage chopper type drive device that performs both step drive pattern control and constant current control in the output stage section. becomes possible.

Further, in the drive device 100 of Patent Document 1, in order to drive the stepping motor 101 in microsteps with high resolution, a required torque vector is generated by combining a plurality of excitation patterns. That is, in each excitation cycle, the average current value of the motor coil is manipulated by controlling the switching (ON/OFF switching) of the power element 106 and outputting a plurality of excitation patterns at respective output time ratios. In this way, the required torque vector is generated. In this case, in manipulating the average current value of the motor coil, the inductance of the motor coil is used to smooth the current flowing through the motor coil.

Therefore, in the microstep drive of the stepping motor 101 by the drive device 100 of Patent Document 1, a plurality of excitation patterns are synthesized in order to obtain the required torque vector, but such technology does not utilize the inductance of the motor coil. It is carried out on the premise of (work).

Further, in the case of the DV type drive device 100 as disclosed in Patent Document 1, constant current control is performed by adjusting the motor drive voltage DV, as described above. Normally, in a stepping motor, as the motor rotation speed increases, the impedance of the motor increases, so the voltage applied to the motor coil (motor drive voltage DV) increases accordingly, but if the motor rotation speed is slowed down or the motor When the motor is stopped, the voltage applied to the motor coil can be reduced in the DV type drive device. For this reason, for example, even if the voltage input to the drive device is 24V DC, when holding the stepping motor at a predetermined angle, the voltage applied to the motor coil should not be 24V as in an output stage chopper type drive device. , can be as small as about 3V.

Japanese Patent Application Publication No. 2008-61439

Typically, the characteristics of a stepping motor vary greatly depending on the performance of the driving device that drives the stepping motor. Further, since a stepping motor is a motor that can not only rotate at a required speed but also perform positioning, both dynamic characteristics and static characteristics are often required as characteristics of the stepping motor.

Here, for example, the dynamic characteristics of a stepping motor that differ depending on the drive device include torque characteristics, self-start characteristics, acceleration tracking characteristics, vibration characteristics (smoothness of rotation), quietness, and motor heat generation during rotation (drive). etc. are included. In addition, the static characteristics of stepping motors that differ depending on the drive device include resolution, relative angular accuracy for each step (excluding absolute errors inherent in the motor), static stability, motor heat generation when stopped (hold), etc. . Furthermore, other characteristics include phase changes when stopping from rotation, vibrations that occur during phase changes, stability when stopping, etc. Further, when expanding the performance to the performance of the drive device, the noise generated by the drive device, noise resistance, etc. are also factors that affect the characteristics in practical use.

The performance of drive devices is improving year by year, and as a result, various characteristics of stepping motors are also improving. Furthermore, as the characteristics of stepping motors become higher, the fields in which stepping motors are used also become more sophisticated, and the demands placed on stepping motors become more sophisticated.

Furthermore, as drivers with improved performance have come to be used in advanced ultra-precision equipment, new problems have arisen that have not been identified in the past. For example, when a stepping motor is stopped and held at a required angle, ultra-fine vibrations (ultra-fine vibrations with a small vibration level on the order of nanometers) that could not be detected in the past occur in the stepping motor in the held state. It was also found that the magnetic field of the stepping motor changed slightly. Such a phenomenon of a stepping motor affects the static characteristics (in particular, static stability) of the stepping motor, and may pose a problem for use in some ultra-precision devices.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a drive device that can suppress the generation of ultra-fine vibrations with a small vibration level when the stepping motor is held.

In order to achieve the above object, the present invention provides a driving device that drives the stepping motor by inputting a command pulse and switching the excitation of a motor coil of the stepping motor. an output stage section including a plurality of output terminals connected to a motor, a switching element provided for each of the output terminals, and an element drive circuit for driving the switching element; and an excitation pattern signal is sent to the output stage section according to the command pulse. The excitation pattern output section includes an excitation pattern output section that outputs an excitation pattern, and a constant current control section that performs constant current control by adjusting a drive voltage applied to the stepping motor, and the excitation pattern output section controls an excitation period that manages a unit excitation cycle. It has a counter and an excitation pattern output selector that outputs a signal of the excitation pattern to the element drive circuit for each unit excitation cycle, and ON/OFF of the switching element is controlled by the element drive circuit to output the excitation pattern. The constant current control unit is controlled according to the excitation pattern output from the selector, and includes a current detection resistor that detects current, a control switching element that increases or decreases the drive voltage by switching ON/OFF, and the current detection resistor. and a PWM control unit that controls ON/OFF of the control switching element based on the detected current detected by the controller, and smoothes a voltage applied to the stepping motor between the output terminal and the switching element. A filter circuit is provided, and the filter circuit is characterized in that it smoothes a rectangular wave voltage formed by ON/OFF of the switching element within the unit excitation cycle and converts it into a DC voltage.

In the drive device of the present invention, it is preferable that the filter circuit includes a filter choke coil and a filter capacitor.
In this case, a filter switching element for switching connection/cutoff is disposed between the filter capacitor and the ground , and the filter switching element is switched to a cutoff state when the stepping motor is in a rotating state. is preferred.
Further, in the drive device of the present invention, it is preferable that the ground of the filter circuit is connected to the ground of the constant current control section.

The drive device according to the present invention is a stepping motor drive device that performs DV type constant current control to adjust the drive voltage, and also has an output terminal to which the stepping motor is connected, and a switching element (power element) in the output stage section. ) A filter circuit for smoothing the voltage applied to the stepping motor is provided for each output terminal.

As a result of careful examination and investigation into the factors that cause ultra-fine vibrations when the stepping motor is in a stopped state (hold state), the inventors of the present invention found that the output current output from the drive device to the stepping motor contains a ripple component. It was found that the ripple component affected the static stability of the motor.

Generally, in a DV type drive device, the voltage at the output terminal becomes a rectangular wave (rectangular wave voltage) by controlling ON/OFF of a switching element in an output stage section. In this case, although the excitation current output to the stepping motor is smoothed by the inductance of the motor coil, a ripple component remains in the current.

In addition, in a DV type drive device, the motor drive voltage (DV voltage) is controlled in the constant current control section so that the detected current detected by the current detection resistor becomes the current value of the reference current, so the DV voltage is repeating minute changes even in the hold state. Such minute changes in the DV voltage affect the form of the ripple component included in the excitation current, and if the change in the form of the ripple component in the excitation current appears at a frequency of 1kHz or less, the static stability of the stepping motor may be affected. It was found that it decreased.

Therefore, in order to obtain excellent static stability without affecting the resolution and vibration characteristics (smoothness of rotation) of the stepping motor caused by the drive device, it is necessary to apply a rectangular wave voltage to the motor coil as in the past. Rather than smoothing the applied excitation current with the inductance component of the motor coil, a filter circuit (low-pass filter circuit) is provided between the output terminal of the drive device and the switching element, and the rectangular wave voltage generated by the switching element is converted to DC. They discovered that it is sufficient to convert it into voltage, and have completed the present invention.

By providing a filter circuit as in the present invention and converting the voltage applied to the stepping motor from a rectangular wave voltage to a DC voltage, an excitation current free of ripple components can be passed through the motor coil. As a result, when the stepping motor is in the hold state, it is possible to suppress the occurrence of ultra-fine vibrations observed in advanced ultra-precision equipment, and it is possible to improve the static stability of the stepping motor compared to the conventional method. Furthermore, by converting the voltage applied to the stepping motor into a DC voltage using a filter circuit, it can be expected that small changes in the magnetic field that occur when the stepping motor is held can be suppressed. Furthermore, in the present invention, since the excitation current of the motor coil no longer contains ripple components, it is also possible to obtain the effect of lowering the heat generated by the motor during hold.

In particular, the present invention is applied to a drive device that performs DV type constant current control. When holding a stepping motor at a required angle, for example with an output stage chopper type drive device, the input voltage to the drive device is directly applied to the motor coil as described above, so a large voltage is applied to the motor coil even when held. However, in the DV type drive device, the voltage applied to the motor coil during hold can be made smaller than when the motor is rotating. That is, the present invention utilizes the characteristic (unique property) of the DV type drive device itself that the rectangular wave voltage formed by chopping of the switching element is reduced when the stepping motor is held. By smoothing a rectangular wave voltage with a small voltage value during hold using a filter circuit, it is possible to obtain an effect that cannot be expected with an output stage chopper type drive device, such as improving the static stability of the stepping motor.

In the drive device of the present invention as described above, the filter circuit includes a filter choke coil and a filter capacitor. Thereby, the rectangular wave voltage caused by the switching element can be stably converted into a DC voltage.

In this case, a filter switching element for switching connection/cutoff may be disposed between the filter capacitor and the ground. For example, when a stepping motor is held, the filter switching element connects the filter capacitor to the ground, and the filter capacitor acts to convert the voltage to DC voltage.On the other hand, when the stepping motor is rotated (driven), the filter capacitor The filter capacitor can be disconnected from the ground using a switching element to prevent the filter capacitor from acting.

When a stepping motor is rotated at high speed, for example, when converting a rectangular wave voltage into a DC voltage using the above-mentioned filter circuit, the excitation coil of the stepping motor is turned on and off according to the excitation pattern. It is conceivable that the switching may be delayed, resulting in a decrease in the torque of the stepping motor during high-speed rotation. On the other hand, by providing a filter switching element as described above and making the filter capacitor ineffective when the stepping motor is driven, it is possible to suppress a decrease in torque of the stepping motor during high-speed rotation.

Further, in the drive device of the present invention, the ground of the filter circuit is connected to the ground of the DV type constant current control section. This eliminates the influence of the installation of the filter circuit on current detection in the constant current control unit, and allows stable DV type constant current control.

FIG. 1 is a block diagram showing the internal configuration of a drive device according to a first embodiment of the present invention. FIG. 2 is an enlarged view showing an output stage section and a filter circuit of the drive device shown in FIG. 1; FIG. 3 is a schematic diagram showing the connection relationship between the output terminal of the drive device and the motor coil of the stepping motor, and the direction of current flowing through the motor coil. FIG. 3 is an explanatory diagram illustrating a state during an OFF time in which all motor coils are not excited. FIG. 2 is an explanatory diagram illustrating the relationship between a motor coil and a torque vector of a stepping motor. It is an explanatory view explaining an excitation pattern of a basic angle step, and a ratio of an excitation pattern between basic angle steps. FIG. 2 is an enlarged circuit diagram showing a filter circuit according to a second embodiment of the present invention. (a) is a graph showing the results of measuring the output voltage and output current at the first output terminal when forming the excitation phase ABCD in the drive device of the example (the drive device of the first embodiment); b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the first output terminal. (a) is a graph showing the results of measuring the output voltage and output current at the second output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the second output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the third output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the third output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the fourth output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the fourth output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the fifth output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the fifth output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the first output terminal when forming excitation phase ABCD in the drive device of the comparative example, and (b) is a graph showing the output voltage at the first output terminal. It is a graph showing the results of measuring ripple components of voltage and output current. (a) is a graph showing the results of measuring the output voltage and output current at the second output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the second output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the third output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the third output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the fourth output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the fourth output terminal. It is a graph showing the results. (a) is a graph showing the results of measuring the output voltage and output current at the fifth output terminal of the drive device, and (b) is a graph showing the results of measuring the ripple components of the output voltage and output current at the fifth output terminal. It is a graph showing the results. FIG. 2 is a block diagram showing the internal configuration of a conventional drive device.

Below, preferred embodiments of the present invention will be described in detail.
First, a driving device 10 according to a first embodiment of the present invention will be specifically described with reference to FIGS. 1 to 6. Here, FIG. 1 is a block diagram showing the internal configuration of the drive device according to the first embodiment, and FIG. 2 is an enlarged view showing the output stage section and filter circuit of the drive device shown in FIG. It is an enlarged view.

A drive device (driver) 10 shown in FIG. 1 is a DV-type drive device 10 that performs DV-type constant current control, and is connected to a five-phase stepping motor 1 of a pendagon connection type. An external command pulse in a CWP (Clock Wise Pulse) direction or a CCWP (Counter Clock Wise Pulse) direction is input to this drive device 10 from an external device such as a controller. The drive device 10 receives the command pulse and switches the motor coil 2 to be excited by the stepping motor 1, thereby driving the stepping motor 1 in steps. Note that the external command pulse in the CWP direction is an external command pulse for rotating the motor rotating shaft (rotor) of the stepping motor 1 clockwise in the forward direction, and the external command pulse in the CCWP direction is for rotating the motor rotating shaft (rotor) in the counterclockwise direction. This is an external command pulse. Further, the external command pulse is sometimes abbreviated as a command pulse.

Here, as shown in FIGS. 3 and 4, the five motor coils 2 in the five-phase stepping motor 1 of the pentagon connection type are connected to a first coil 2a, a second coil 2b, a third coil 2c, and a fourth coil 2d, respectively. , the fifth coil 2e. In addition, the motor currents flowing through the first coil 2a to the fifth coil 2e are respectively defined as motor currents A, a; motor currents B, b; motor currents C, c; motor currents D, d; motor currents E, e. Define.

In this case, motor currents A, B, C, D, E and motor currents a, b, c, d, e are opposite in each of the first coil 2a to fifth coil 2e with respect to the alphabets corresponding to each other. Indicates the current flowing in the direction. For example, regarding the first coil 2a, the state in which it is excited by flowing a motor current A is referred to as an excitation coil (excitation phase) A, and the state in which it is excited by flowing a motor current a in the opposite direction is referred to as an excitation coil (excitation phase) a. represent. The same applies to the second coil 2b to the fifth coil 2e as in the case of the first coil 2a.

Furthermore, as shown in FIG. 5, motor currents A, a; B, b; C, c; D, d; E, e flow through the first coil 2a to fifth coil 2e of the five-phase stepping motor 1, respectively. The torque vectors generated when the motor current is applied are defined as torque vectors VA, Va; VB, Vb; VC, Vc; VD, Vd; VE, Ve, respectively, in correspondence with the letters of the motor current. That is, the torque vector VA generated by the excitation coil A and the torque vector Va generated by the excitation coil a are vectors in opposite directions.

The drive device 10 according to the first embodiment includes five output terminals 11, a first output terminal 11a to a fifth output terminal 11e, an output stage section 20, and an excitation device that outputs an excitation pattern signal to the output stage section 20. It has a pattern output circuit (excitation pattern output section) 30, a constant current control section 40 that performs DV type constant current control, and five filter circuits 50 arranged between the output stage section 20 and each output terminal 11. .

The first output terminal 11a to the fifth output terminal 11e are respectively connected to five connection points to which adjacent motor coils 2 of the stepping motor 1 are connected. In the case of the first embodiment, the first output terminal 11a to the fifth output terminal 11e are connected to each connection point of the stepping motor 1 in the relationship shown in FIGS. 3 and 4, respectively.

The output stage section 20 includes a plurality of switching elements (power MOS FETs) TR1 to TR10 and an element drive circuit (power element drive circuit) 21 that drives the switching elements TR1 to TR10. The switching elements TR1 to TR10 are connected to the positive side (high side) switching elements TR1, TR3, TR5, TR7, and TR9 connected to the power supply side and the ground side for each of the first output terminal 11a to the fifth output terminal 11e. It has negative electrode side (low side) switching elements TR2, TR4, TR6, TR8, and TR10 connected to.

The element drive circuit 21 is formed by a gate driver (dedicated IC). In the element drive circuit 21, in order to drive the positive side switching elements TR1, TR3, TR5, TR7, and TR9, it is necessary to charge capacitors (not shown) corresponding to the switching elements TR1, TR3, TR5, TR7, and TR9. There is. This capacitor is charged by turning on the switching elements TR2, TR4, TR6, TR8, and TR10 on the negative side (turning off the switching elements TR1, TR3, TR5, TR7, and TR9 on the positive side).

Therefore, in this drive device 10, in order to charge the above-mentioned capacitor, for example, as shown in FIGS. 4 and 6, every unit excitation cycle T, all the positive switching elements corresponding to each output terminal 11 are It is necessary to provide an OFF time in which the motor coil 2 is not excited by turning off TR1, TR3, TR5, TR7, and TR9 (turning on switching elements TR2, TR4, TR6, TR8, and TR10 on the negative side). . In the present invention, as described above, at all output terminals 11, the positive side switching elements TR1, TR3, TR5, TR7, and TR9 are turned OFF, and the negative side switching elements TR2, TR4, TR6, TR8, and TR10 are turned ON. For convenience, this state is defined as "negative OFF". In this "negative OFF" state, all the connection points of the motor coils 2 are held at the same negative potential, so the stepping motor 1 is in a non-excited state in which all the motor coils 2 are not excited.

The excitation pattern output circuit 30 is composed of a logic circuit, and in particular, in the first embodiment, is composed of an FPGA (Field Programmable Gate Array).
This excitation pattern output circuit 30 includes an address counter 31 that counts input external command pulses and manages electrical angle positions (step positions) and addresses corresponding to the electrical angle positions, and a counter that counts command pulses from the address counter 31. It has a speed measurement counter 32 that manages the rotational speed of the stepping motor 1 by inputting it, and an excitation period counter 33 that manages a unit excitation cycle T (unit excitation period).

The excitation pattern output circuit 30 also includes a memory 34 that stores a plurality of excitation pattern data, excitation duty data, etc., and selects excitation pattern data and excitation duty data from the memory 34 and generates a signal of the excitation pattern in unit excitation according to the data. It has an excitation pattern output selector 35 that outputs an output every cycle T. Furthermore, the motor drive voltage DV digitized by the A/D converter is input to the excitation pattern output circuit 30. Note that in the present invention, each part of the excitation pattern output circuit 30 that performs the above-described processing may be formed by a plurality of processing sections, or a plurality of sections that perform each processing may be formed by one processing section. may have been done.

The address counter 31 forming the excitation pattern output circuit 30 manages the electrical angle position and the address value by counting up or down the address value in response to input of an external command pulse. Further, the address counter 31 outputs the numerical value of the managed address to the speed measurement counter 32, the excitation period counter 33, and the excitation pattern output selector 35, respectively.

The speed measurement counter 32 manages the calculated rotational speed of the stepping motor 1 based on the number of input external command pulses per unit time, and outputs the value of the managed rotational speed to the excitation pattern output selector 35. The excitation period counter 33 manages a fixed unit excitation cycle T independent of external command pulses, and outputs an excitation switching command to the excitation pattern output selector 35 for each unit excitation cycle T.

The excitation pattern output selector 35 performs a process of switching the excitation pattern to be output to the element drive circuit 21. That is, the excitation pattern output selector 35 selects a plurality of excitation pattern data and a plurality of duties stored in the memory 34 based on the rotation speed managed by the speed measurement counter 32 and the address managed by the address counter 31. Corresponding excitation pattern data and duty data are selected from the data, and a signal of the selected excitation pattern is output to the element drive circuit 21 every unit excitation cycle T.

As a result, the element drive circuit 21 controls ON/OFF of each switching element TR1 to TR10 of the output stage section 20 according to the excitation pattern input from the excitation pattern output selector 35, thereby controlling the motor coil of the stepping motor 1. 2 is excited at a predetermined timing.

Further, the excitation pattern output circuit 30 may be provided with a determination counter (not shown) that determines the drive state and hold state of the stepping motor based on the input of the external command pulse CWP or CCWP. This determination counter has a drive state maintenance timer that starts counting at the falling edge or rising edge of an external command pulse for the drive device, and also has a determination time for determining the drive state. As this determination time, for example, a time of 150 ms is set.

In the determination counter, for example, when an external command pulse is input, the drive state maintenance timer is counted from the initial value, and if the next external command pulse is input before the set determination time (150 ms) has elapsed, The drive state is determined (the determination of the drive state is maintained), and the drive state maintenance timer is cleared and starts counting again from the initial value. On the other hand, if the next external command pulse is not input by the set determination time, the hold state is determined. Further, the determination counter outputs a signal indicating the determination result between the drive state and the hold state, and the output signal is used as a signal for switching the reference value (reference current) in the constant current control section 40. As a result, the constant current control section 40 can lower the excitation current that excites the motor coil when the stepping motor is held, for example, and as a result, it becomes possible to reduce heat generation of the stepping motor in the held state.

The constant current control section 40 shown in FIG. 1 performs DV type constant current control on the stepping motor 1. The constant current control unit 40 includes a first capacitor C1 that smoothes the voltage input to the drive device 10, a control switching element TR11 that increases or decreases the motor drive voltage DV by switching ON/OFF, and a control switching element TR11 that increases or decreases the motor drive voltage DV by switching ON/OFF. A control element drive circuit 41 that drives ON/OFF of TR11, a choke coil L1 and a second capacitor C2 that smooth intermittent voltages generated by switching the control switching element TR11 to generate motor drive voltage DV, It has a diode D1 that bypasses the electromotive force generated by the choke coil L1.

Further, the constant current control section 40 includes a first sensing resistor (first current detection resistor) R1 connected in series between the negative side of the second capacitor C2 and the ground, and the output side of the circuit forming the output stage section 20. and a second sensing resistor (second current detection resistor) R2 connected in series between the negative side of the second capacitor C2, and the detected current detected by the first sensing resistor R1 and the second sensing resistor R2. It has a PWM constant current control circuit (PWM control section) 42 that controls an element drive circuit 41 for use.

The PWM constant current control circuit 42 generates the difference between the detected current and the reference current in the first sensing resistor R1 and the second sensing resistor R2 as an error signal, and based on the error signal, outputs the current through the control element drive circuit 41. to switch ON/OFF of the control switching element TR11. Thereby, the drive voltage applied to the stepping motor 1 is adjusted to control the current flowing through the motor coil 2 to be constant.

Specifically, when the current flowing through the first sensing resistor R1 and the second sensing resistor R2 decreases, the level of the error signal increases, so the PWM constant current control circuit 42 changes the ON time of the control switching element TR11. lengthen. Thereby, the drive voltage is increased and the current flowing through the motor coil 2 is increased. On the other hand, when the current flowing through the first sensing resistor R1 and the second sensing resistor R2 increases, the level of the error signal decreases, so the PWM constant current control circuit 42 shortens the ON time of the control switching element TR11. As a result, the current flowing through the motor coil 2 is reduced. Thereby, the current flowing through the motor coil 2 can be stabilized at a constant level, and the stepping motor 1 can be driven at a constant current.

The drive device 10 is provided with five filter circuits 50, a first filter circuit 50a to a fifth filter circuit 50e, corresponding to the first output terminal 11a to the fifth output terminal 11e. The first filter circuit 50a to the fifth filter circuit 50e are formed with the same circuit configuration.

Each filter circuit 50 is formed by a low-pass filter circuit 50 having one filter choke coil Lf and one filter capacitor Cf. The filter choke coil Lf is located between the positive side switching elements TR1, TR3, TR5, TR7, TR9 and the negative side switching elements TR2, TR4, TR6, TR8, TR10, and the positive side of the filter capacitor Cf. placed in between.

The negative electrode side of the filter capacitor Cf is connected to the ground of the filter circuit 50. In this case, the ground of the filter circuit 50 is connected to the ground of the constant current control section 40. This eliminates the influence of voltage smoothing in the filter circuit 50 on current detection by the constant current control section 40, making it possible to stably perform DV type constant current control.

By providing such a filter circuit 50 between each output terminal 11 and the corresponding switching elements TR1 to TR10, a rectangular wave voltage formed by ON/OFF of the switching elements TR1 to TR10 can be converted into a DC voltage. This allows direct current without ripple components to flow from the output terminal 11 to the motor coil 2.

Further, in the first embodiment, the filter choke coil Lf has the same inductance as the choke coil L1 provided in the constant current control section 40. Further, a hybrid type capacitor having a lower impedance than the first capacitor C1 and the second capacitor C2 of the constant current control section 40 is used as the filter capacitor Cf. By using such a filter choke coil Lf and a filter capacitor Cf, the voltage applied to the motor coil 2 (motor drive voltage DV) can be stably smoothed by the filter circuit 50.

Next, a method for driving the stepping motor 1 using the driving device 10 of this embodiment will be explained.
When driving the stepping motor 1, the excitation pattern output circuit 30 of the drive device 10 outputs a signal of a desired excitation pattern from the excitation pattern output selector 35 to the element drive circuit of the output stage section 20 in accordance with an external command pulse input from the outside. Output to 21. The element drive circuit 21 controls ON/OFF of each of the switching elements TR1 to TR10 according to the excitation pattern signal input from the excitation pattern output selector 35. At the same time, the constant current control section 40 performs DV type constant current control by switching ON/OFF of the control switching element TR11.

Here, the rotation and excitation pattern of the stepping motor 1 will be explained.
One electrical angle (360°) of the stepping motor 1 corresponds to 7.2° of mechanical angle (rotation angle of the motor rotation shaft). By repeating this electrical angle revolution (7.2 degrees of mechanical angle) 50 times, it is possible to complete one mechanical angle revolution (one rotation of the motor rotation shaft).

For example, when an external command pulse in the CWP direction is input and the stepping motor 1 is driven step by step around one electrical angle (7.2 degrees of mechanical angle) at a basic angle step (full step) position, the output stage section 20 By switching ON/OFF of the switching elements TR1 to TR10, the four-phase excitation that excites the four phases of the motor coil 2 in the stepping motor 1 is sequentially switched. Specifically, the four-phase excitation of the motor coil 2 is as follows: excitation phase ABCD (0° electrical angular position) → BCDE (36° electrical angular position) → CDEa (72° electrical angular position) → DEab (108° electrical angular position) electrical angle position) → Eabc (electrical angle position of 144°) → abcd (electrical angle position of 180°) → bcde (electrical angle position of 216°) → cdeA (electrical angle position of 252°) → deAB (288° It is changed by switching 10 times in the order of (electrical angle position) → eABC (electrical angle position of 324°) → excitation phase ABCD (electrical angle position of 0°).

As a result, the motor rotating shaft of the stepping motor 1 is stepped (stepped) 10 times by 0.72 degrees in mechanical angle (36 degrees in electrical angle), and a mechanical angle of 7.2 degrees, which is one revolution in electrical angle, is achieved. Rotate (forward rotation). By repeating these 10 basic angle steps 50 times (10 basic angle steps x 50), the motor rotor can be rotated 360 degrees in mechanical angle, that is, one rotation in mechanical angle. can. Note that when an external command pulse in the CCWP direction is input, the excitation of the motor coil 2 is changed in the reverse order to that described above, thereby making it possible to reversely rotate the motor rotor.

In addition, in the first embodiment, when the motor coil 2 is excited in four phases at each basic angle step position, each excitation phase is is formed. For example, at the electrical angle position of 0°, as shown in FIG. 6, the excitation phase AD by the excitation pattern AD and the excitation phase BC by the excitation pattern BC are combined and output within a unit excitation cycle T (48.6 μs). As a result, a synthesized excitation phase ABCD is formed in a unit excitation cycle T.

At this time, in the excitation pattern AD and the excitation pattern BC, each voltage of the first output terminal 11a to the fifth output terminal 11e is controlled to + (plus) or - (minus) as shown in FIG. Ru. For example, among a pair of positive side switching elements TR1, TR3, TR5, TR7, TR9 and negative side switching elements TR2, TR4, TR6, TR8, TR10 arranged at each output terminal 11, the positive side switching element TR1, By turning on TR3, TR5, TR7, and TR9 (turning off switching elements TR2, TR4, TR6, TR8, and TR10 on the negative side), the voltage at the output terminal 11 becomes + (plus: approximately motor drive voltage DV). can do. In addition, by turning on the switching elements TR2, TR4, TR6, TR8, and TR10 on the negative side (turning off the switching elements TR1, TR3, TR5, TR7, and TR9 on the positive side), the voltage at the output terminal 11 is -( (minus: approximately 0V).

That is, in the case of the excitation pattern AD, the output stage section is arranged so that the voltage at the first output terminal 11a to the fourth output terminal 11d becomes - (minus), and the voltage at the fifth output terminal 11e becomes + (plus). 20 switching elements TR1 to TR10 are controlled, and as a result, a current that excites the A phase (first coil 2a) and D phase (fourth coil 2d) of the stepping motor 1 is passed through the motor coil 2, so that the excitation phase AD is formed.

Furthermore, in the case of excitation pattern BC, the voltages at the second output terminal 11b and the third output terminal 11c are - (minus), and the voltages at the first output terminal 11a, the fourth output terminal 11d, and the fifth output terminal 11e are The switching elements TR1 to TR10 of the output stage section 20 are controlled so that the value becomes + (plus), thereby exciting the B phase (second coil 2b) and C phase (third coil 2c) of the stepping motor 1. Since the current flows through the motor coil 2, an excitation phase BC is formed. In each unit excitation cycle T, a negative OFF state in which the negative side switching elements TR2, TR4, TR6, TR8, and TR10 are turned ON at all output terminals 11 is ensured for a time of 0.6 μs.

When the motor coil 2 is excited by the excitation pattern BC and the excitation pattern AD as described above, the direction of the torque vector obtained by the excitation pattern BC (i.e., VB+VC) and the torque vector obtained by the excitation pattern AD (i.e., VA+VD) The direction is the same as that of (see Figure 5). Further, the magnitude of the torque vector synthesized by the excitation pattern BC is stronger than the torque vector synthesized by the excitation pattern AD. Therefore, in the first embodiment, by making the total excitation time of the excitation pattern BC longer than the total excitation time of the excitation pattern AD within the unit excitation cycle T, the torque at the 0° electrical angle position is further increased. It can be generated stably.

Furthermore, in the case of step driving in basic angle steps, an external command pulse in the CWP direction is input from the state of the above-mentioned excitation phase ABCD (0° electrical angle position), and the address of the address counter 31 is counted up. The excitation of the motor coil 2 is switched to the excitation phase BCDE (36° electrical angle position). The excitation phase BCDE is formed by combining the excitation pattern BE and the excitation pattern CD, similarly to the excitation phase ABCD. Further, in this case, the excitation pattern CD is excited for a longer time than the excitation pattern BE.

On the other hand, when the resolution of the stepping motor 1 is set high by an external resolution command (STEP SEL) and the stepping motor 1 is driven in steps at microstep positions set between full step positions, at each microstep position, A first combination excitation pattern that combines two two-phase excitation patterns at one full step position, and a second combination excitation pattern that combines two two-phase excitation patterns at the next full step position, They are formed in combination at a ratio depending on the step position.

For example, at a microstep position set between excitation phase ABCD (0° electrical angle position) and excitation phase BCDE (36° electrical angle position), four-phase excitation ABCD is realized as shown in FIG. Two two-phase excitation patterns (first combination excitation pattern including excitation pattern BC and excitation pattern AD) and two two-phase excitation patterns (excitation pattern CD and excitation pattern) that realize four-phase excitation BCDE at the next full step position. (a second combination excitation pattern including pattern BE) are combined at a ratio according to the step position to excite the motor coil 2.

In this case, as the address of the address counter 31 increases (as it approaches the excitation phase BCDE from the excitation phase ABCD), the proportion of the excitation pattern BC and the excitation pattern AD forming the four-phase excitation ABCD in the unit excitation cycle T is gradually decreased. , the ratio of the excitation pattern CD and the excitation pattern BE forming the four-phase excitation BCDE is gradually increased.

That is, in microstep driving, a plurality of excitation patterns are combined in a unit excitation cycle T, and the average current value flowing through the motor coil 2 is manipulated by controlling the output time ratio of each excitation pattern to obtain the required value. Forms a torque vector. Thereby, the stepping motor 1 can be sequentially driven in steps at each microstep position, and can be rotated from a position where the electrical angle is 0° to a position where the electrical angle is 36°.

Next, a case will be described in which the stepping motor 1 is stopped and held at a required angle (for example, an electrical angle position of 0°) in the drive device 1 of the first embodiment that performs the above-described control.
When holding the stepping motor 1 at the electrical angle position of 0°, as described above, by combining the excitation pattern BC and the excitation pattern AD every unit excitation cycle T, the four-phase excitation ABCD is synthesized, and the four-phase excitation ABCD is By repeating this in a plurality of unit excitation cycles T, the stepping motor 1 is held at the electrical angle position of 0°.

Within each unit excitation cycle T (48.6 μs), the excitation pattern BC and the excitation pattern AD are switched, so that each voltage of the first output terminal 11a to the fifth output terminal 11e is applied to the switching element of the output stage section 20. Controlled by ON/OFF of TR1 to TR10. For example, at the first output terminal 11a and the fourth output terminal 11d, within one unit excitation cycle T (excluding negative OFF), the voltage is - (minus) for 8 μs, + (plus) for 32 μs, - (minus) ON/OFF of the switching elements TR1, TR2, TR7, and TR8 is controlled (switched) so that the time is 8 μs. Further, at the second output terminal 11b and the third output terminal 11c, ON/OFF of the switching elements TR3 to TR6 is controlled so that the voltage becomes - (minus) within the unit excitation cycle T, and at the fifth output terminal 11e, , ON/OFF of switching elements TR9 and TR10 is controlled so that the voltage becomes + (plus) within a unit excitation cycle T (excluding negative OFF).

Here, in order to explain the features of the present invention, first, processing performed in a conventional drive device will be explained. When driving the stepping motor 1 using a conventional drive device, as described above, a plurality of excitation patterns are combined in a unit excitation cycle T, and the motor coil is controlled by controlling the output time ratio of each excitation pattern. The required torque vector is formed by manipulating the average current value flowing through the motor.

In conventional drive devices, when controlling the average current value of the motor coil 2 by combining excitation patterns, the switching element in the output stage section is turned ON/OFF in order to flow the current according to the excitation pattern to the motor coil 2. A rectangular wave of voltage is applied to the motor coil 2 from the output terminal under control. In this case, since the current in the motor coil 2 is smoothed by the inductance of the motor coil 2, it is possible to form a required torque vector using the smoothed current. That is, in the conventional drive device, the use of the inductance of the motor coil 2 is the premise (basic) of the technique of manipulating the average current value of the motor coil 2 by combining excitation patterns.

However, when a rectangular wave of voltage is applied from the output terminal to the motor coil 2 as described above, the current flowing through the stepping motor 1 becomes DC due to the inductance of the motor coil 2. The current includes a ripple component due to ON/OFF of the switching element in the output stage section. This time, it has been newly discovered that the ripple component of this current affects the static stability of the motor.

Therefore, in the first embodiment, instead of applying a voltage rectangular wave to the motor coil 2 (rather than smoothing the current with the inductance of the motor coil 2), the switching elements TR1 to TR10 in the drive device 10 and the output By providing the above-mentioned filter circuit 50 between the terminal 11 and the terminal 11, the voltage (output voltage) applied to the motor coil 2 is converted into a DC voltage instead of a conventional rectangular wave voltage, thereby eliminating ripple components. The current that is not included is output to the stepping motor 1.

That is, in the case of the drive device 10 of the first embodiment, for example, when holding the stepping motor 1 at the electrical angle position of 0° as described above, in order to flow a current in the motor coil 2 according to the excitation pattern, Although the ON/OFF of the switching elements TR1 to TR10 of the output stage section 20 is controlled according to the excitation pattern BC and the excitation pattern AD as shown in 6, the rectangular wave voltage formed by the ON/OFF of the switching elements TR1 to TR10 is controlled. is smoothed by the filter circuit 50 before being output from the output terminal 11.

As a result, each output terminal 11 of the drive device 10 can apply the DC voltage smoothed by the filter circuit 50 to the motor coil 2, so that a current that does not include ripple components is output to the motor coil 2, and the motor coil 2 can be excited. In this case, the average current value of the current flowing through the motor coil 2 controls the output time ratio of the excitation pattern (i.e., the ratio of the time when the positive side switching elements TR1, TR3, TR5, TR7, and TR9 are turned ON). It can be operated by

Specifically, when holding the stepping motor 1 at an electrical angle position of 0°, as described above, the voltage at the first output terminal 11a and the fourth output terminal 11d increases within one unit excitation cycle T. Although the ON/OFF of the switching elements TR2, TR4, TR6, TR8, and TR10 on the positive and negative sides can be switched so that the time is 8 μs for - (minus), 32 μs for + (plus), and 8 μs for - (minus), The rectangular wave voltage formed by this switching is smoothed by the first filter circuit 50a and the fourth filter circuit 50d, and a DC voltage is applied to the motor coil 2 from the first output terminal 11a and the fourth output terminal 11d. (See FIGS. 8 and 11 described later).

In this case, the voltage output from the first output terminal 11a and the fourth output terminal 11d is the fifth output whose voltage is always controlled to be + (plus) within the unit excitation cycle T, for example, in the combined excitation source ABCD. Compared to the terminal 11e, the ratio of the output time (time controlled to be positive) within the unit excitation cycle T is 2/3 (66%). Therefore, the average current value flowing from the first output terminal 11a and the fourth output terminal 11d to the motor coil 2 is set to about 2/3 (66%) of the average current value flowing from the fifth output terminal 11e to the motor coil 2. be able to.

In particular, in the DV type driving device 10, when the stepping motor 1 is in the hold state, the magnitude of the rectangular wave voltage formed by chopping of the switching element is smaller than in the drive state, so the rectangular wave voltage is changed to the DC voltage. The filter circuit 50 can perform the conversion stably.

As described above, in the drive device 10 of the first embodiment, the filter circuit 50 is provided between the switching elements TR1 to TR10 and the output terminal 11, so that the stepping motor 1 can be A DC voltage can be applied to the motor coil 2, thereby allowing a current with no ripple component to flow through the motor coil 2 to excite the motor coil 2. Furthermore, in this case, the form of the excitation current does not include a ripple component, so it is not affected by minute changes in the DV voltage.

As a result, when the stepping motor 1 is held at the required angle, it is possible to suppress the occurrence of ultra-fine vibrations that would be observed when a conventional drive device is applied to advanced ultra-precision equipment. Static characteristics (especially static stability) can be greatly improved compared to conventional drive devices. In this case, the effect of reducing the heat generated by the motor during hold can also be obtained. Furthermore, since the drive device 10 of the first embodiment can apply a DC voltage to the motor coil 2, it is also expected to have the effect of suppressing the occurrence of small changes in the magnetic field that occur when applying a conventional rectangular wave voltage, for example. can.

Next, a drive device 10a according to a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 7 is a circuit diagram showing an enlarged filter circuit in the drive device according to the second embodiment.

The driving device 10a according to the second embodiment is different from the driving device 10 according to the first embodiment described above in that each filter circuit 60 (in FIG. 7, the first In the filter circuit 60a), a filter switching element TR12 for switching connection/cutoff is additionally provided between the filter capacitor Cf and the ground.

Note that the drive device 10a according to the second embodiment is formed substantially the same as the drive device 10 according to the first embodiment described above, except that a filter switching element TR12 is additionally installed. There is. Therefore, in the second embodiment, parts or members having substantially the same configuration as those in the first embodiment described above will be represented by the same reference numerals, and a description thereof will be omitted.

In the second embodiment, when the stepping motor 1 is in the stopped state (hold state), the filter switching element TR12 is switched to the connected state (ON state), so that the negative electrode side of the filter capacitor Cf is connected to the ground (constant state). (ground) of the current control section 40. This allows the filter capacitor Cf to smooth the voltage. On the other hand, when the stepping motor 1 is in the rotating state (drive state), the filter switching element TR12 is switched to the cut-off state (OFF state), and the smoothing by the filter capacitor Cf is controlled so as not to be effective.

In this case, a signal from a determination counter (not shown) provided in the excitation pattern output circuit 30 described in the first embodiment is used to switch ON/OFF of the filter switching element TR12. Thus, for example, when the determination counter outputs an L level signal indicating the hold state of the stepping motor 1, the filter switching element TR12 is turned on and the filter capacitor Cf can function effectively. On the other hand, when the determination counter outputs an H level signal indicating the driving state of the stepping motor 1, the filter switching element TR12 is turned off, and the filter capacitor Cf is cut off from the ground.

For example, in the case of the drive device 10 according to the first embodiment, as described above, when the stepping motor 1 is in the hold state, the filter circuit 50 smoothes the rectangular wave voltage, thereby suppressing the occurrence of ultra-fine vibrations. are doing. However, on the other hand, when the stepping motor 1 is rotated at high speed, it is necessary to switch the voltage at the output terminal 11 quickly, but the voltage smoothing performed by the filter circuit 50 hinders the switching speed. This may cause a delay in the timing of switching the excitation phase of the stepping motor 1. As a result, there is a possibility that the torque generated by the stepping motor 1 may be reduced in the high speed rotation region.

On the other hand, the drive device 10a according to the second embodiment provides the above-described filter switching element TR12 in each filter circuit 60, and controls the ON/OFF state of the filter switching element TR12 to the hold state of the stepping motor 1. / It is formed so that it can be switched depending on the drive state. As a result, when the stepping motor 1 is in the hold state, the negative electrode side of the filter capacitor Cf can be connected to the ground, and when the stepping motor 1 is in the drive state, the negative electrode side of the filter capacitor Cf can be disconnected from the ground. It becomes possible to smooth the voltage using the capacitor Cf only when the stepping motor 1 is in the hold state.

As a result, according to the drive device 10a according to the second embodiment, when the stepping motor 1 is in the hold state, the motor drive voltage DV is low and stable, and a constant excitation pattern is repeatedly output. Even if the filter circuit 60 is made to function effectively, the filter circuit 60 will not interfere with the hold control of the stepping motor 1. Therefore, like the drive device 10 according to the first embodiment, the drive device 10a according to the second embodiment can effectively suppress generation of ultra-fine vibrations when the stepping motor 1 is held.

On the other hand, in the driving state of the stepping motor 1, the drive device 10a according to the second embodiment suppresses the torque drop in the high speed rotation region by switching the filter switching element TR12 to suppress the influence of the filter circuit 60. For example, it is possible to provide substantially the same dynamic characteristics as a drive device that does not include the filter circuit 60.

In the first and second embodiments described above, each of the filter circuits 50 and 60 includes one filter choke coil Lf and one filter capacitor Cf. However, in the present invention, the number of filter choke coils and the number of filter capacitors provided in each filter circuit are not particularly limited.

For example, the filter circuit of the present invention is formed by connecting an additional filter capacitor (second filter capacitor) in parallel with the first filter capacitor Cf to the filter circuit 50 of the first embodiment. may have been done. Moreover, the filter circuit of the present invention may be formed only by one or more filter capacitors Cf without providing the filter choke coil Lf.

Furthermore, in the first and second embodiments described above, the element drive circuit 21 provided in the output stage section 20 is formed by a gate driver (dedicated IC), but in the present invention, the element drive circuit is not a gate driver. Instead, it may be formed by a transistor circuit.

(Example and Comparative Example 1)
As an example, using the drive device 10 of the first embodiment described above, the 5-phase stepping motor 1 is held at an electrical angle position of 0° (the position of the basic angle step when the power is turned on), and the The voltages (output voltages) applied from the first output terminal 11a to the fifth output terminal 11e, the current flowing through the motor coil 2, and the ripple component contained in the current were measured. The measurement results are shown in FIGS. 8 to 12.

Note that when the stepping motor 1 is held at the electrical angle position of 0°, as described with reference to FIG. 6, the excitation pattern AD and the excitation pattern BC are combined and output within the unit excitation cycle T, and By controlling the output time ratio of excitation pattern AD and the output time ratio of excitation pattern BC, excitation phase ABCD corresponding to the electrical angle position of 0° is formed.

Further, as Comparative Example 1, a drive device (that is, a conventional drive device) having a structure in which the first filter circuit 50a to the fifth filter circuit 50e are removed from the drive device 10 of the first embodiment described above was used. As in the example, the five-phase stepping motor 1 was held at the electrical angle position of 0°. At that time, the voltage applied from the first output terminal to the fifth output terminal, the current flowing through the motor coil 2, and the ripple component contained in the current were measured in the same manner as in the example. The measurement results are shown in FIGS. 13 to 17.

In each of the figures in FIGS. 8 to 17, the graph (a) shows a voltage waveform 71 measured by selecting DC coupling and a waveform 72 of the current flowing through the motor coil 2. The graph in (b) shows a voltage waveform 71 and a ripple component waveform 73 included in the current measured by selecting AC coupling. Note that the ripple component waveform 73 is obtained by observing the ripple component of the current observed with direct current (500 mA/Div) at a magnification of 10 times (50 mA/Div).

When the stepping motor 1 is held at the electrical angle position of 0°, as shown in FIG. It can be switched in order between + (plus) and - (minus). Therefore, in the case of the drive device of the comparative example that does not include the first filter circuit 50a to the fifth filter circuit 50e, as shown in FIGS. 13 and 16, the output voltage of the first output terminal 11a and the fourth output terminal 11d is A square wave appears.

Furthermore, although the currents flowing from the first output terminal 11a and the fourth output terminal 11d to the motor coil 2 are smoothed by the inductance of the motor coil 2, the currents shown in FIG. 13(b) and As shown in FIG. 16(b), it can be confirmed that ripple components caused by ON/OFF switching of the switching elements TR1 to TR10 are included. The shape of the ripple component included in this current changes under the influence of minute changes in the DV voltage, and when the shape change of the ripple component appears at a frequency of 1 kHz or less, the vibration level of the stepping motor 1 in the hold state changes. generates extremely small ultra-fine vibrations on the order of nanometers.

On the other hand, in the case of the drive device 10 of the example (drive device 10 of the first embodiment), since the filter circuit 50 is provided in each output terminal 11, the first output terminal 11a and the fourth output terminal Even if ON/OFF of the switching elements TR1, TR2, TR7, TR8 corresponding to 11d is switched within the unit excitation cycle T, as shown in FIGS. 8 and 11, the first output terminal 11a and the fourth output terminal It can be confirmed that no rectangular wave appears in the output voltage of 11d, and that each is a smoothed DC voltage. Furthermore, since a DC voltage is applied from the first output terminal 11a and the fourth output terminal 11d, a DC current that does not include ripple components flows into the motor coil 2 from the first output terminal 11a and the fourth output terminal 11d. (See the waveform 73 of the ripple component in FIG. 8(b) and FIG. 11(b)).

Therefore, in the drive device 10 of the embodiment, as shown in FIGS. 8 to 12, when the stepping motor 1 is in the hold state, a direct current without ripple components is supplied from each of the first output terminal 11a to the fifth output terminal 11e. It was confirmed that since current could be stably passed through the motor coil 2, the effect of preventing the occurrence of ultra-fine vibrations caused by ripple components could be obtained. Furthermore, when the step angle accuracy when driving the stepping motor 1 in microsteps with the drive device 10 of the example was also confirmed, no deterioration in the characteristics of the step angle accuracy was observed.

(Comparative example 2)
As Comparative Example 2, in a driving device that performs output stage chopper type constant current control, a filter circuit 50 similar to that of the driving device of the embodiment is provided between each output terminal and a switching element, so that a stepping motor can be controlled. 1 hold, I tried smoothing the voltage output from each output terminal using an output stage chopper type drive device.

As a result, in the output stage chopper type drive device provided with the filter circuit 50, the detection current (current flowing through the coil) is detected by the sensing resistor in order to perform constant current control, but the form of the detected current is It was found that the filter circuit 50 changes the constant current control, making it impossible to stably perform constant current control. Therefore, a filter circuit that smoothes the voltage output from the output terminal cannot be applied to a drive device that performs output stage chopper type constant current control, and is only effective for a drive device that performs DV type constant current control. I was also able to confirm that.

1 Stepping motor 2 Motor coil 2a 1st coil 2b 2nd coil 2c 3rd coil 2d 4th coil 2e 5th coil 10, 10a Drive device (driver)
11 Output terminal 11a First output terminal 11b Second output terminal 11c Third output terminal 11d Fourth output terminal 11e Fifth output terminal 20 Output stage section 21 Element drive circuit (power element drive circuit)
30 Excitation pattern output circuit (excitation pattern output section)
31 Address counter 32 Speed measurement counter 33 Excitation period counter 34 Memory 35 Excitation pattern output selector 40 Constant current control section 41 Control element drive circuit 42 PWM current constant current control circuit (PWM control section)
50 Filter circuit (low-pass filter circuit)
50a First filter circuit 50b Second filter circuit 50c Third filter circuit 50d Fourth filter circuit 50e Fifth filter circuit 60 Filter circuit 60a First filter circuit 71 Voltage waveform 72 Current waveform 73 Ripple component waveform A, a Coil B,b Motor current flowing in the coil C,c Motor current flowing in the coil D,d Motor current flowing in the coil E,e Motor current flowing in the coil DV Motor drive voltage C1 First capacitor C2 Second capacitor Cf Filter Capacitor D1 Diode L1 Choke coil Lf Filter choke coil R1 First sensing resistor (first current detection resistor)
R2 Second sensing resistor (second current detection resistor)
T Unit excitation cycle TR1 to TR10 Switching element TR11 Control switching element TR12 Filter switching element VA, Va Torque vector VB, Vb Torque vector VC, Vc Torque vector VD, Vd Torque vector VE, Ve Torque vector

Claims (4)

A drive device (10, 10a) that drives the stepping motor (1) by inputting a command pulse and switching excitation of a motor coil (2) of the stepping motor (1),
a plurality of output terminals (11) connected to the stepping motor (1);
an output stage section (20) comprising switching elements (TR1 to TR10) provided for each of the output terminals (11) and an element drive circuit (21) for driving the switching elements (TR1 to TR10);
an excitation pattern output section (30) that outputs an excitation pattern signal to the output stage section (20) according to the command pulse;
a constant current control section (40) that performs constant current control by adjusting the drive voltage applied to the stepping motor (1);
The excitation pattern output section (30) includes an excitation period counter (33) that manages unit excitation cycles (T), and a signal of the excitation pattern to the element drive circuit (21) for each unit excitation cycle (T). It has an excitation pattern output selector (35) to output,
ON/OFF of the switching elements (TR1 to TR10) is controlled by the element drive circuit (21) according to the excitation pattern output from the excitation pattern output selector (35),
The constant current control section (40) includes a current detection resistor (R1, R2) that detects the current, a control switching element (TR11) that increases or decreases the drive voltage by switching ON/OFF, and the current detection resistor ( a PWM control unit (42) that controls ON/OFF of the control switching element (TR11) based on the detected current detected by R1, R2),
A filter circuit (50, 60) for smoothing the voltage applied to the stepping motor (1) is provided between the output terminal (11) and the switching elements (TR1 to TR10) ,
The filter circuit (50, 60) smoothes the rectangular wave voltage formed by ON/OFF of the switching elements (TR1 to TR10) within the unit excitation cycle (T) and converts it into a DC voltage.
A drive device characterized by: The drive device according to claim 1, wherein the filter circuit (50, 60) includes a filter choke coil (Lf) and a filter capacitor (Cf). A filter switching element (TR12) for switching connection/cutoff is arranged between the filter capacitor (Cf) and the ground ,
The filter switching element (TR12) is switched to a cutoff state when the stepping motor (1) is in a rotating state.
The drive device according to claim 2. The drive device according to claim 1, wherein the ground of the filter circuit (50, 60) is connected to the ground of the constant current control section (40).

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