JP2021064995A - Driving device and ripple current detection circuit for stepping motor, and driving method and ripple current detection method for stepping motor - Google Patents

Abstract

To provide a driving device for a stepping motor capable of preventing the stepping motor from being vibrated in a saturation state of a drive voltage.SOLUTION: A driving device comprises: an output step section (11) and an element drive section (12); an excitation pattern output section (20) which outputs an excitation pattern signal to the element drive section (12); and a constant current control section (30) which performs constant current control. The constant current control section (30) includes: a control current detection circuit (51) which detects a current for constant current control; and a ripple current detection circuit (52) which detects a ripple current included in a current caused by vibration of a stepping motor. The excitation pattern output section (20) includes a time control part (26) which controls a ratio of an excitation time (61) and an OFF time (62) in a unit excitation term (T). The time control part (26) decreases the ratio of the excitation time (61) when the ripple current detected by the ripple current detection circuit (52) is increased, and increases the ratio of the excitation time (61) when the ripple current is decreased.SELECTED DRAWING: Figure 1

Description

The present invention relates to a stepping motor drive device and a ripple current detection circuit, and a stepping motor drive method and a ripple current detection method.

Generally, when driving a motor rotor of a 5-phase stepping motor having five motor coils (hereinafter abbreviated as coils), a command pulse is input from the outside to a driving device (driver) of the stepping motor. The drive device counts the input command pulses and switches the excitation of the 5-phase stepping motor coil according to the counted value to control the rotation of the motor rotor by an angle proportional to the total number of command pulses. Do.

As a stepping motor drive device, for example, Japanese Patent Application Laid-Open No. 2016-131471 (Patent Document 1) describes two types of stepping motor drive devices having different constant current control methods. For example, as shown in FIG. 13, one drive device 100 described in Patent Document 1 is connected to a 5-phase stepping motor 101 of a pendagon connection type, and steps are performed by performing constant current control of an output stage chopper type. The motor 101 is step-driven.

The output stage chopper type drive device 100 shown in FIG. 13 includes an excitation pattern output unit 110 that outputs an excitation pattern for exciting the coil by inputting a command pulse CWP or CCWP, and a plurality of switching elements 121 (power elements). It has an output stage unit 120 that controls ON / OFF according to an excitation pattern output from the excitation pattern output unit 110, and a motor current control unit 130 that performs constant current control of the output stage chopper type of the stepping motor 101.

The excitation pattern output unit 110 includes an electric angle position management unit 111 that counts input command pulses and manages the address, and a motor rotation speed management unit 112 that manages the motor rotation speed by counting the command pulses CWP and CCWP. An excitation cycle counter unit 113 that manages a fixed unit excitation cycle, an excitation pattern storage unit 114 that stores a plurality of excitation sequences, and an excitation pattern selection unit 115 that selects and outputs an excitation sequence from the excitation pattern storage unit 114. Excitation / non-excitation processing unit 116 that outputs an excitation / non-excitation signal according to the signal from the PWM constant current control circuit 134 of the motor current control unit 130, and current saturation determination unit 117 that determines that the current flowing through the coil is saturated. Has.

The excitation cycle counter unit 113 manages a fixed unit excitation cycle irrelevant to the command pulses CWP and CCWP, and outputs an excitation switching command for each unit excitation cycle. The excitation pattern storage unit 114 stores a low-speed excitation sequence, a medium-speed excitation sequence, a high-speed excitation sequence, and the like for step-driving the stepping motor 101 in each speed region. The excitation pattern selection unit 115 has a rotation speed managed by the motor rotation speed management unit 112 and an address managed by the electric angle position management unit 111 from among a plurality of excitation sequences stored in the excitation pattern storage unit 114. An appropriate excitation sequence is selected based on (electrical angle position), and an excitation pattern is output to the output stage 120 for each unit excitation cycle according to the selected excitation sequence.

The exciting / non-exciting processing unit 116 controls the current flowing through the coil to a constant magnitude by switching between the excited state and the non-excited state according to the signal from the PWM constant current control circuit 134 of the motor current control unit 130. Output stage chopper type current control is performed.

The output stage 120 has a plurality of switching elements 121, a power element drive circuit 122 for switching ON / OFF of the switching element 121, and an output terminal 123 connected to the coil of the stepping motor 101. Two switching elements 121 are arranged for each output terminal 123. The power element drive circuit 122 switches each switching element 121 according to the excitation pattern output from the excitation pattern output unit 110. The motor current control unit 130 includes a power supply 131, a capacitor 132 that smoothes the voltage of the power supply 131, a current detection resistor 133 that detects the current flowing through the coil, and a PWM that adjusts the excitation output time according to the impedance of the coil. It has a constant current control circuit 134.

Here, a method of output stage chopper type constant current control by the motor current control unit 130 and the excitation / non-excitation processing unit 116 will be briefly described.

The PWM constant current control circuit 134 of the motor current control unit 130 receives the signal of the unit excitation cycle output from the excitation cycle counter unit 113 and generates a sawtooth wave having a plurality of substantially triangular vibrations for each unit excitation cycle. To do. At the same time, the PWM constant current control circuit 134 generates an error signal between the reference current value and the detection current generated at both ends of the current detection resistor 133 in order to obtain a constant exciting current, and the level of the error signal and the above-mentioned description. Compare with the level of sawtooth waves.

Then, when the relationship of error signal ≥ sawtooth wave is established, the exciting / non-exciting processing unit 116 of the exciting pattern output unit 110 puts the exciting output in an excited state, and a predetermined current is passed through the coil (exciting the coil). ). On the other hand, when the error signal <sawtooth wave relationship is established, a signal is output from the PWM constant current control circuit 134, and the excitation / non-excitation processing unit 116 of the excitation pattern output unit 110 sets the excitation output to the non-excitation state. All terminals are negative or positive. This keeps the coil in a non-excited state.

A method in which the current flowing through the coil is controlled to be constant by chopping the output stage portion 120 in this way is known as an output stage chopper type constant current control. The drive device 100 that performs constant current control of the output stage chopper type can reduce the number of circuits as compared with the drive device 140 of the motor drive voltage conversion type (hereinafter abbreviated as DV type) described later, so that the cost is increased. It is advantageous for compactness.

Further, in another drive device 140 described in Patent Document 1 as shown in FIG. 14, DV type constant current control is performed.
The DV type drive device 140 has an excitation pattern output unit 150 that outputs an excitation pattern for exciting the coil by inputting a command pulse CWP or CCWP, and an excitation pattern that turns ON / OFF of a plurality of switching elements 121 (power elements). It has an output stage unit 120 that controls according to an excitation pattern output from the output unit 150, and a motor current control unit 160 that performs DV type constant current control. The excitation pattern output unit 150 in the DV type drive device 140 is formed without the excitation / non-excitation processing unit 116 provided in the output stage chopper type drive device 100.

The DV type motor current control unit 160 is detected by the power supply 161 and the first capacitor 162 that smoothes the voltage of the power supply 161 and the first and second current detection resistors 163a and 163b that detect the current flowing through the coil. A PWM constant current control circuit 164 that performs constant current control based on the current, a control switching element 165 that can be switched ON / OFF, and a control switching element based on the output signal from the PWM constant current control circuit 164. A power element drive circuit 166 that switches 165 ON / OFF, a diode 167 that bypasses the electromotive force generated by the coil, a choke coil 168 that smoothes the intermittent voltage generated by PWM control to generate a motor drive voltage, and a third choke coil. It has two capacitors 169 and an A / D converter 170.

The DV type PWM constant current control circuit 164 generates an error signal between the current flowing through the coil and the reference current to control ON / OFF of the control switching element 165. As a result, the motor drive voltage input to the coil is adjusted, and a constant current flows through the coil. For example, when the currents flowing through the first and second current detection resistors 163a and 163b decrease, the level of the error signal rises, so that the PWM constant current control circuit 164 lengthens the ON time of the control switching element 165. .. As a result, control is performed to increase the motor drive voltage. On the other hand, when the currents flowing through the first and second current detection resistors 163a and 163b increase, the ON time of the control switching element 165 is shortened to reduce the motor drive voltage. By appropriately controlling the motor drive voltage by the motor current control unit 160 in this way, the current can be maintained constant regardless of the unit excitation cycle managed by the excitation cycle counter unit 113.

Since the drive device 140 that performs such DV type constant current control converts the voltage input from the power supply 161 into the motor drive voltage, it requires more circuits than the output stage chopper type drive device 100 described above. However, the output stage unit 120 can only perform pattern control for performing step drive (particularly, micro step drive). Therefore, the DV type drive device 140 performs microstep drive with higher resolution than the output stage chopper type drive device 100 that performs both step drive pattern control and constant current control in the output stage unit 120. It becomes possible.

Japanese Unexamined Patent Publication No. 2016-131471

As described above, in the DV type drive device 140, the total amount of current flowing through the coil of the stepping motor 101 is controlled by manipulating the motor drive voltage in the motor current control unit 160.

On the other hand, in a stepping motor, the impedance of the motor coil increases as the rotation speed of the motor increases. Therefore, when the impedance of the coil becomes high, the constant current control can be continued by increasing the ON duty (ON width) of the control switching element in the PWM constant current control circuit of the motor current control unit to raise the motor drive voltage. .. However, when the rotation speed of the motor is increased to increase the impedance of the coil, the ON duty of the control switching element becomes maximum, and the motor drive voltage becomes saturated. As a result, in the rotation speed region where the motor drive voltage is saturated, the constant current control by the DV type motor current control unit becomes ineffective.

Therefore, for example, in a rotation speed region slower than the rotation speed at which the motor drive voltage is saturated, the ON duty of the control switching element is always controlled by the PWM constant current control circuit, so that a constant current can flow through the coil. it can. As a result, vibration is less likely to occur in the stepping motor, and even if vibration occurs and the current is disturbed, the motor current control unit controls the current to return to the normal state, so vibration is suppressed. Can be done.

However, in the rotation speed region where the rotation speed is higher than the rotation speed at which the motor drive voltage is saturated, the ON width of the control switching element remains maximum even if the stepping motor vibrates, and the motor drive voltage cannot be controlled. As a result, since it is not possible to control the current to return to a normal state, there is a problem that vibration cannot be suppressed and the rotation speed of the motor becomes uneven.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to suppress the occurrence of vibration in the stepping motor in the rotation speed region where the motor drive voltage is saturated, and to reduce the speed unevenness of the rotation speed. It is an object of the present invention to provide a possible stepping motor drive device and drive method, and a ripple current detection circuit and ripple current detection method used for them.

In order to achieve the above object, the stepping motor drive device provided by the present invention is a drive device that switches the excitation of the stepping motor coil by inputting a command pulse to drive the stepping motor and outputs the output. An output stage unit having two switching elements for each terminal, an element drive unit that drives the switching element, and an excitation pattern output unit that outputs an excitation pattern signal to the element drive unit in a unit excitation cycle according to the command pulse. It has a constant current control unit that controls a constant current by adjusting the drive voltage applied to the stepping motor, and the constant current control unit includes a control current detection circuit that detects a current for the constant current control. , A control switching element that increases or decreases the drive voltage by switching ON / OFF, and a PWM control unit that switches ON / OFF of the control switching element based on the detection current detected by the control current detection circuit. The excitation pattern output unit includes an excitation current detection circuit that detects a ripple current included in the current flowing through the coil due to the vibration of the stepping motor, and the excitation pattern output unit excites the coil by applying the drive voltage. It has a time control unit that controls the ratio of time to the OFF time that does not excite the coil in the unit excitation cycle, and the time control unit is used when the ripple current detected by the ripple current detection circuit increases. The main feature is to decrease the ratio of the excitation time and increase the ratio of the excitation time when the ripple current decreases.

In the drive device according to the present invention described above, the ripple current detection circuit is a first amplifier circuit that detects and amplifies the voltage drop of the sensing resistance through which the exciting current that excites the coil and the regenerative current from the coil flow. The ripple is amplified by amplifying the difference between the second amplifier circuit that further amplifies the voltage output from the first amplifier circuit and the voltage output from the first amplifier circuit and the voltage output from the second amplifier circuit. It is preferable to have a third amplifier circuit that outputs as an electric current.

Further, in the drive device of the present invention, the excitation pattern output unit has a saturation determination unit that determines between an unsaturated state in which the drive voltage is not saturated and a saturated state in which the drive voltage is saturated, and the time control unit. Controls the ratio of the excitation time when the determination by the saturation determination unit is in the saturated state, and stops the control of the ratio of the excitation time when the determination by the saturation determination unit is in the non-saturation state. Is preferable.

Further, in the drive device of the present invention, the time control unit reduces the rate of change that increases or decreases the ratio of the excitation time when the current detected by the control current detection circuit increases, and the detection is detected. It is preferable to increase the rate of change when the current decreases.

The ripple current detection circuit provided by the present invention is a ripple current detection circuit provided in a drive device for driving a stepping motor, and is a voltage of a sensing resistor through which an exciting current for exciting the coil and a regenerative current from the coil flow. From the first amplification circuit that detects and amplifies the drop, the second amplification circuit that further amplifies the voltage output from the first amplification circuit, the voltage output from the first amplification circuit, and the second amplification circuit. Its main feature is that it has a third amplification circuit that amplifies the difference in the output voltage and outputs it as a ripple current included in the current due to the vibration of the stepping motor.

Next, the stepping motor driving method provided by the present invention is a driving method for driving the stepping motor by switching the excitation of the stepping motor to the coil by inputting a command pulse, and an excitation pattern is performed according to the command pulse. The stepping motor is step-driven by step-driving the stepping motor by outputting an excitation pattern signal from the output unit in a unit excitation cycle and switching ON / OFF of the switching element of the output stage unit by the element drive unit according to the excitation pattern signal. In the control unit, the control current detection circuit detects the constant current control current, switches ON / OFF of the control switching element based on the detected current, and adjusts the drive voltage applied to the stepping motor. By doing so, constant current control is performed, and the ripple current detection circuit provided in the constant current control unit detects the ripple current contained in the current flowing through the coil due to the vibration of the stepping motor that is step-driven. The detected ripple current is increased by the time control unit that controls the ratio of the excitation time for applying the drive voltage to excite the coil and the OFF time for not exciting the coil in the unit excitation cycle. The main feature is that sometimes, the ratio of the excitation time of the drive voltage in the unit excitation cycle is decreased, and when the ripple current is decreased, the ratio of the excitation time in the unit excitation cycle is increased. It is a thing.

In the driving method of the present invention described above, the first amplification circuit of the ripple current detection circuit detects and amplifies the voltage drop of the sensing resistance through which the exciting current that excites the coil and the regenerative current from the coil flow. The voltage output from the first amplification circuit is further amplified by the second amplification circuit of the ripple current detection circuit, and the voltage output from the first amplification circuit is output by the third amplification circuit of the ripple current detection circuit. It is preferable to include amplifying the difference between the voltage obtained and the voltage output from the second amplification circuit and outputting it as the ripple current.

Further, in the driving method of the present invention, the saturation determination unit provided in the excitation pattern output unit determines a non-saturated state in which the driving voltage is not saturated and a saturated state in which the driving voltage is saturated. The time control unit controls the ratio of the excitation time when the determination by the saturation determination unit is in the saturated state, and controls the ratio of the excitation time when the determination by the saturation determination unit is in the non-saturation state. It is preferable to include stopping.

Further, in the driving method of the present invention, when the current detected by the control current detection circuit increases, the time control unit reduces the rate of change that increases or decreases the ratio of the excitation time, and the detection is detected. It is preferable to include increasing the rate of change when the current decreases.

In the ripple current detection method provided by the present invention, the exciting current that excites the coil of the stepping motor and the regenerated current from the coil are combined by the first amplification circuit of the ripple current detection circuit provided in the drive device of the stepping motor. Detecting and amplifying the voltage drop of the flowing sensing resistance, further amplifying the voltage output from the first amplification circuit by the second amplification circuit of the ripple current detection circuit, and The third amplification circuit amplifies the difference between the voltage output from the first amplification circuit and the voltage output from the second amplification circuit, and uses it as the ripple current included in the current due to the vibration of the stepping motor. Its main feature is to include output.

The drive device for a stepping motor according to the present invention has an excitation pattern output unit provided with a time control unit for controlling the ratio of the excitation time for exciting the coil to the OFF time for non-excitation in the unit excitation cycle, and a DV type constant current control. The constant current control unit is provided with a ripple current detection circuit that detects the ripple current included in the current flowing through the coil due to the vibration of the stepping motor.

As described above, when the stepping motor vibrates in the rotation speed region where the motor drive voltage is saturated, constant current control by the DV type motor current control unit cannot be performed, and the rotation speed of the motor becomes uneven. Give rise. In this case, since the stepping motor is also a generator, the current flowing through the stepping motor includes the ripple current generated due to the speed unevenness, and the larger the vibration of the stepping motor, the larger the ripple current. .. Such a ripple current is much smaller than the current flowing through the stepping motor, and the current flowing through the stepping motor itself becomes higher or lower. Therefore, conventionally, the ripple current is included in the current flowing through the stepping motor. Was difficult to detect.

In the drive device of the present invention described above, the ripple current detection circuit provided in the constant current control unit makes it possible to detect a small ripple current due to speed unevenness in the current flowing through the stepping motor. That is, in the present invention, we have succeeded in detecting the vibration of the stepping motor generated when the motor drive voltage is saturated by the current.

Therefore, in the present invention, the ripple current is detected by the ripple current detection circuit, and the detected ripple current is output to the excitation pattern output unit. Therefore, in the time control unit of the excitation pattern output unit, the ripple current detection circuit is used. When the detected ripple current increases, the excitation time ratio decreases (the OFF time ratio increases), and when the ripple current decreases, the excitation time ratio increases (the OFF time ratio decreases). , Control the ratio of excitation time per unit excitation cycle. This makes it possible to fine-tune the voltage application time to the motor based on the ripple current caused by the speed unevenness of the stepping motor, and as a result, the vibration of the stepping motor that occurs in the rotational speed region where the motor drive voltage is saturated. It can be suppressed to reduce the unevenness of the rotation speed. That is, according to the present invention, the fluctuation of the motor rotation speed caused by the speed unevenness can be stabilized at the required motor rotation speed by eliminating the vibration (that is, the speed unevenness) by controlling the excitation time based on the ripple current. it can.

In the drive device according to the present invention described above, the ripple current detection circuit includes a first amplifier circuit that detects and amplifies the voltage drop of the sensing resistance through which the exciting current that excites the coil and the regenerative current from the coil flow. The second amplifier circuit that further amplifies the voltage output from the amplifier circuit, and the third amplifier that amplifies the difference between the voltage output from the first amplifier circuit and the voltage output from the second amplifier circuit and outputs it as a ripple current. Has a circuit. With such a ripple current detection circuit, the ripple current caused by the speed unevenness in the current flowing through the stepping motor can be easily detected.

Further, in the drive device of the present invention, the excitation pattern output unit has a saturation determination unit that determines a non-saturated state in which the drive voltage is not saturated and a saturated state in which the drive voltage is saturated. Further, the time control unit of the excitation pattern output unit controls the ratio of the excitation time when the determination by the saturation determination unit is in the saturated state, and controls the ratio of the excitation time when the determination by the saturation determination unit is in the non-saturation state. To stop. As a result, the stepping motor can be efficiently driven in a non-saturated state in which vibration is unlikely to occur, and the vibration of the stepping motor can be effectively suppressed in a saturated state in which vibration occurs.

Further, in the drive device of the present invention, the time control unit reduces the rate of change that increases or decreases the ratio of the excitation time when the current detected by the control current detection circuit increases, and decreases the detected current. In addition, increase the rate of change. As a result, for example, the current flowing through the stepping motor becomes smaller during acceleration of the stepping motor, so that the change in the ratio of the excitation time is moderated, while the current flowing through the stepping motor becomes larger during deceleration of the stepping motor. The change in the ratio of the excitation time can be abrupt. As a result, the vibration suppression effect of the stepping motor based on the detection of the ripple current can be further enhanced.

The ripple current detection circuit according to the present invention is provided in the driving device of the stepping motor. This ripple current detection circuit further amplifies the first amplification circuit that detects and amplifies the voltage drop of the sensing resistance through which the exciting current that excites the coil and the regenerative current from the coil flows, and the voltage output from the first amplification circuit. Amplifies the difference between the voltage output from the second amplification circuit and the voltage output from the first amplification circuit and the voltage output from the second amplification circuit, and outputs it as a ripple current included in the current due to the vibration of the stepping motor. It has a third amplification circuit. As a result, the ripple current caused by the speed unevenness in the current flowing through the stepping motor can be easily detected.

Next, in the stepping motor driving method according to the present invention, the stepping motor is step-driven and the constant current control unit performs constant current control. Further, the ripple current detection circuit provided in the constant current control unit detects the ripple current included in the current flowing through the coil due to the vibration of the stepping motor driven in steps. Then, when the detected ripple current increases by the time control unit that controls the ratio of the excitation time for applying the drive voltage to excite the coil and the OFF time for not exciting the coil in the unit excitation cycle, the unit excitation cycle Decrease the ratio of the excitation time of the drive voltage in. That is, for each unit excitation cycle, the ratio of the excitation time (time for applying the drive voltage) in the excitation cycle is reduced. On the other hand, when the ripple current decreases, the ratio of the excitation time per unit excitation cycle is controlled so as to increase the ratio of the excitation time in the unit excitation cycle (to increase the ratio of the excitation time per unit excitation cycle). To do. As a result, vibration of the stepping motor generated in the rotation speed region where the motor drive voltage is saturated can be suppressed, and speed unevenness of the rotation speed can be reduced.

In such a driving method of the present invention, the first amplification circuit of the ripple current detection circuit detects and amplifies the voltage drop of the sensing resistance through which the exciting current that excites the coil and the regenerative current from the coil flow, and then amplifies the voltage. The voltage output from the first amplification circuit is further amplified by the second amplification circuit of the ripple current detection circuit, and the voltage output from the first amplification circuit and the third amplification circuit by the third amplification circuit of the ripple current detection circuit. 2 The difference in voltage output from the amplification circuit is amplified and output as a ripple current. As a result, the ripple current caused by the speed unevenness in the current flowing through the stepping motor can be easily detected.

Further, in the driving method of the present invention, the saturation determination unit provided in the excitation pattern output unit determines the non-saturated state in which the driving voltage is not saturated and the saturated state in which the driving voltage is saturated, and further, the time control unit determines the saturated state. The excitation time ratio is controlled when the determination by the saturation determination unit is in the saturated state, and the excitation time ratio control is stopped when the determination by the saturation determination unit is in the non-saturation state. As a result, the stepping motor can be efficiently driven in a non-saturated state in which vibration is unlikely to occur, and the vibration of the stepping motor can be effectively suppressed in a saturated state in which vibration occurs.

Further, in the driving method of the present invention, when the time control unit reduces the rate of change that increases or decreases the ratio of the excitation time when the current detected by the control current detection circuit increases, the detected current decreases. In addition, increase the rate of change. As a result, the vibration suppression effect of the stepping motor based on the detection of the ripple current can be further enhanced.

In the ripple current detection method according to the present invention, first, sensing in which the exciting current that excites the coil of the stepping motor and the regenerated current from the coil flow by the first amplification circuit of the ripple current detection circuit provided in the drive device of the stepping motor. Detects and amplifies the voltage drop of the resistor. Subsequently, the voltage output from the first amplifier circuit is further amplified by the second amplifier circuit of the ripple current detection circuit. After that, the difference between the voltage output from the first amplifier circuit and the voltage output from the second amplifier circuit is amplified by the third amplifier circuit of the ripple current detection circuit, and is included in the current due to the vibration of the stepping motor. It is output as a ripple current. As a result, the ripple current caused by the speed unevenness in the current flowing through the stepping motor can be easily detected.

It is a block diagram which shows the internal structure of the drive device which concerns on embodiment of this invention. It is a circuit diagram which shows the control current detection circuit and the ripple current detection circuit of a drive device. It is explanatory drawing explaining the current flow in the constant current control part of a drive device. It is a graph which shows the relationship between the motor rotation speed and torque in a stepping motor. It is explanatory drawing explaining the electrode connection state of the coil in the OFF time when the coil is not excited. It is explanatory drawing explaining the excitation time and OFF time in a unit excitation cycle. It is a graph which shows the waveform output from the 1st amplifier circuit to the 3rd amplifier circuit of the ripple current detection circuit at the time of vibration of a stepping motor. It is a graph which shows the waveform output from the 1st amplifier circuit to the 3rd amplifier circuit of the ripple current detection circuit when the vibration of a stepping motor is suppressed. It is a graph which shows the relationship between the rotation speed (output frequency) of a stepping motor, and time when a stepping motor is step-driven by the drive device of an embodiment (Example 1). It is a graph which shows the relationship between the rotation speed (output frequency) of a stepping motor, and time when the same stepping motor as in FIG. 9 is step-driven without controlling the ratio of excitation time by the time control unit (comparative example). 1). It is a graph which shows the relationship between the rotation speed (output frequency) of a stepping motor, and time when another stepping motor is step-driven by the drive device of an embodiment (Example 2). It is a graph which shows the relationship between the rotation speed (output frequency) of a stepping motor, and time when the same stepping motor as in FIG. 11 is step-driven without controlling the ratio of excitation time by the time control unit (comparative example). 2). It is a block diagram which shows the internal structure of the conventional drive device of an output stage chopper type. It is a block diagram which shows the internal structure of the conventional drive device of a motor drive voltage conversion type.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an internal configuration of a drive device according to the present embodiment, and FIG. 2 is a circuit diagram showing a control current detection circuit and a ripple current detection circuit of the drive device.

The drive device 1 shown in FIG. 1 is a driver connected to a 5-phase stepping motor of a pendagon connection system (see FIG. 5) to step drive the stepping motor. The drive device 1 is provided with five output terminals 2 connected to a stepping motor, and each output terminal 2 is connected to a connection point connecting two coils 5 of the stepping motor. Further, a command pulse in the CWP (ClockWise Pulse) direction or the CCWP (Counter LockWise Pulse) direction is input to the drive device 1 from an external device such as a controller.

The drive device 1 of FIG. 1 drives an output stage portion 11 having two switching elements (not shown) on the positive side and a negative side for each output terminal 2, and turns the switching element ON / OFF by driving the output stage portion 11. The element drive unit 12 to be switched, the excitation pattern output unit 20 that outputs an excitation pattern signal to the element drive unit 12, and a coupler circuit that electrically insulates from the outside and receives a command pulse from the outside and inputs it to the excitation pattern output unit 20. 13, the constant current control unit 30 that adjusts the drive voltage applied to the stepping motor to perform constant current control, and the first A / D converters 16 to 3 A / D that digitally convert the signal input to the excitation pattern output unit 20. It has a converter 18. In this case, the excitation pattern output unit 20 is composed of an FPGA (Field Programmable Gate Array).

The element drive unit 12 of this embodiment is formed by a gate driver (dedicated IC). In order to drive the switching element on the positive electrode side in the element driving unit 12, it is necessary to charge a capacitor (not shown) corresponding to the switching element. Charging of this capacitor is performed by turning on the switching element on the negative electrode side (turning off the switching element on the positive electrode side).

Therefore, in the case of the present embodiment, in order to charge the capacitor, for example, as shown in FIG. 6A, the switching elements on the positive electrode side of all the output terminals 2 are turned off for each unit excitation cycle T ( It is necessary to provide an OFF time 62 in which the coil 5 is not excited by turning on the switching element on the negative electrode side.

In the present invention, as described above, the state in which the switching element on the positive electrode side is turned off and the switching element on the negative electrode side is turned on in all the output terminals 2 is defined as “negative OFF”. In this case, as shown in FIG. 5, the stepping motor is in a non-excited state in which all five coils 5 are not excited because all the connection points of the coils 5 are held at the same negative potential.

The excitation pattern output unit 20 counts the input command pulses and manages the address corresponding to the electric angle position (step position), and the electric angle position management unit (address counter) 21 and the stepping motor by counting the command pulses. A rotation speed management unit (speed measurement counter) 22 that manages the rotation speed, an excitation cycle counter unit 23 that manages the unit excitation cycle T, and an excitation pattern storage unit 24 that stores a plurality of excitation pattern data and excitation duty data. Has.

Further, the excitation pattern output unit 20 of the present embodiment selects excitation pattern data from the excitation pattern storage unit 24 and outputs an excitation pattern according to the excitation pattern data for each unit excitation cycle T (output selection unit). ) 25, the time control unit 26 that controls the temporal ratio in the unit excitation cycle T of the excitation time (ON time) 61 that excites the coil 5 and the OFF time 62 that does not excite the coil 5, and the voltage unsaturated state. It has a saturation determination unit 27 for determining the saturation state. The motor drive voltage digitized by the third A / D converter 18 is input to the excitation pattern output unit 20. In the present invention, each portion of the excitation pattern output unit 20 that performs the above-described processing may be formed by a plurality of processing units, and a plurality of portions that perform each processing are formed by one processing unit. You may.

In the excitation pattern output unit 20 of the present embodiment, the electric angle position management unit 21 manages the numerical value of the address by counting up or down by inputting a command pulse, and also manages the numerical value of the managed address. It is output to the rotation speed management unit 22 and the excitation pattern output selector 25. The rotation speed management unit 22 manages the calculated rotation speed of the stepping motor from the number of input of command pulses per unit time, and outputs the value of the managed rotation speed to the excitation pattern output selector 25. The excitation cycle counter unit 23 manages a constant unit excitation cycle T irrelevant to the command pulse, and outputs an excitation switching command to the excitation pattern output selector 25 for each unit excitation cycle T.

The excitation pattern output selector 25 of the excitation pattern output unit 20 is managed by the rotation speed management unit 22 from a plurality of excitation pattern data (or an excitation sequence including a plurality of excitation pattern data) stored in the excitation pattern storage unit 24. The corresponding excitation pattern data (or excitation sequence) is selected based on the rotation speed and the address managed by the electric angle position management unit 21, and the signal of the excitation pattern (or the excitation pattern in the excitation sequence) is transmitted. Output to the element drive unit 12 for each unit excitation period T. As a result, the element drive unit 12 controls ON / OFF of each switching element of the output stage unit 11 according to the excitation pattern signal input from the excitation pattern output selector 25, thereby setting the coil 5 of the stepping motor to a predetermined value. It is excited at the timing and the stepping motor is step-driven.

The time control unit 26 excites the coil 5 in the unit excitation cycle T managed by the excitation cycle counter unit 23 based on the ripple current detected by the ripple current detection circuit 52 described later in the constant current control unit 30. The ratio (length) of the excitation time 61 and the OFF time 62 in the negative OFF state shown in FIG. 5 is changed.

For example, when the saturation determination unit 27 determines the voltage saturation state and the ripple current detected by the ripple current detection circuit 52 increases, the time control unit 26 starts from the state shown in FIG. 6A. As shown in FIG. 6B, the ratio of the excitation time 61 and the OFF time 62 is controlled so as to decrease the ratio of the excitation time 61 in the unit excitation cycle T (increase the ratio of the OFF time 62). On the other hand, when the ripple current decreases in the voltage saturation state, the time ratio is controlled so as to increase the ratio of the excitation time 61 in the unit excitation cycle T (decrease the ratio of the OFF time 62). When the magnitude of the detected ripple current is equal to or less than a predetermined threshold value, the OFF time 62 in the unit excitation cycle T is controlled to the minimum length (charging time) required for charging the switching element. The minimum length (charging time) of the OFF time 62 is set in advance in the excitation pattern output unit 20.

Further, the time control unit 26 stops (masks) the function of controlling the ratio of the excitation time 61 and the OFF time 62 described above when the determination described later by the saturation determination unit 27 is in the non-saturation state of the drive voltage. On the other hand, when the saturation determination unit 27 determines that the drive voltage is saturated, the stop of the function is released (the mask is removed), and the ratio of the excitation time 61 and the OFF time 62 as described above is controlled. In the case of the embodiment, in the non-saturated state where the voltage is not saturated, as shown in FIG. 6A, the OFF time of the minimum length required for charging the switching element in each unit excitation cycle T. It is set to 62 (charging time).

The saturation determination unit 27 is the output of the motor drive voltage (DV) with respect to the DC power input from the third A / D converter 18, the output from the current reference circuit 37 of the constant current control unit 30, and the constant current control unit 30. Saturation determination is performed based on the three signals of the output from the 1A / D converter 16.

Generally, as the rotation speed of the stepping motor increases, the impedance of the coil 5 of the stepping motor increases. Therefore, if the stepping motor rotates faster than a certain rotation speed, the current cannot rise to a predetermined magnitude within the unit excitation period T, and as a result, sufficient torque cannot be obtained in the stepping motor. In this way, the state in which one unit excitation cycle T ends before the current rises to a predetermined magnitude is the state in which the drive voltage (current) is saturated. The rotation speed at which the drive voltage is saturated differs depending on the motor characteristics of the stepping motor.

In the saturation determination unit 27 of the present embodiment, the motor drive voltage (DV) is a voltage equal to or higher than a certain value, and the relationship of "current reference value of constant current control> current detection value", that is, the PWM control unit 38 described later. A state in which 100% ON continues is determined to be a saturated state. In the present invention, the method of determining the non-saturated state and the saturated state by the saturation determination unit 27 is not particularly limited and can be arbitrarily changed. For example, the saturation determination unit 27 can determine a state in which the motor drive voltage (DV) is constant or higher and the motor rotation speed is constant or higher as a saturation state.

The constant current control unit 30 of the present embodiment performs DV type constant current control for the stepping motor. The constant current control unit 30 includes a first capacitor 31 that smoothes the voltage of the input DC power supply, a control switching element 32 that increases or decreases the motor drive voltage by switching ON / OFF, and a control switching element 32. A motor drive voltage smoothed by inputting an intermittent voltage generated by switching between a control element drive unit 33 that drives ON / OFF, a diode 34 that bypasses the electromotive force generated by the coil 5, and a control switching element 32. It has a choke coil 35 and a second capacitor 36 that generate a second capacitor.

Further, the constant current control unit 30 includes a first sensing resistor 41 connected in series between the negative side of the second capacitor 36 and the ground, and the output side of the circuit forming the output stage portion 11 and the second capacitor 36. It was digitized by the second sensing resistor 42 connected in series between the negative sides, the current detection circuit 50 that detects the current flowing through the first sensing resistor 41 and the second sensing resistor 42, and the third A / D converter 18. A current reference circuit 37 that monitors the motor drive voltage and outputs a reference current signal from the motor drive voltage, and a PWM control unit that performs constant current control based on the signals output from the current detection circuit 50 and the current reference circuit 37. It has 38 and.

In the constant current control unit 30, the first sensing resistor 41 and the second sensing resistor 42 are excited with a supply current I1 for charging the second capacitor 36 and a coil 5 of the stepping motor, as shown in FIG. The current of (I1 + I2-I3) flows with respect to the exciting current I2 and the regenerative current I3 generated by the electromotive force of the coil 5 and regenerated from the coil 5. In the present invention, this (I1 + I2-I3) current is used as the current for constant current control.

In this case, the supply current I1 flows so as to circulate in this order through the first capacitor 31, the control switching element 32, the choke coil 35, and the second capacitor 36. The exciting current I2 flows through the second capacitor 36, the output stage portion 11 (coil 5), and the second sensing resistor 42 in this order. The regenerative current I3 flows through the output stage portion 11 (coil 5), the second capacitor 36, and the second sensing resistor 42 in this order.

As shown in FIG. 2, the current detection circuit 50 is a control current detection circuit that detects a constant current control current flowing through the first sensing resistor 41 and the second sensing resistor 42, that is, a current of (I1 + I2-I3). (First current detection circuit) 51 and the current flowing through the second sensing resistor 42, that is, the ripple current detection circuit (second current detection circuit) that detects the ripple current included in the current from the current of (I2-I3). It has 52 and.

The control current detection circuit 51 of FIG. 2 includes a control amplifier circuit (control operational amplifier) 51a that amplifies the difference between the sum of the voltages of the first sensing resistor 41 and the second sensing resistor 42 and the reference voltage. The signal amplified by the control amplifier circuit 51a is digitized by the first A / D converter 16 and output to the PWM control unit 38 and the excitation pattern output unit 20.

When the constant current control unit 30 of the present embodiment performs DV type constant current control, the difference between the voltage and the reference voltage in the first sensing resistor 41 and the second sensing resistor 42 is generated as an error signal, and the error signal is generated. Is digitized and sent to the PWM control unit 38, and the PWM control unit 38 switches ON / OFF of the control switching element 32 based on the error signal. Thereby, the drive voltage (supply current I1) applied to the stepping motor can be adjusted to control the current flowing through the coil 5 (that is, the current of (I2-I3)) to be constant.

Specifically, when the current flowing through the first sensing resistor 41 and the second sensing resistor 42 decreases, the level of the error signal rises, so that the PWM control unit 38 prolongs the ON time of the control switching element 32. To do. As a result, the supply current I1 is increased and the current flowing through the coil 5 is increased. On the other hand, when the current flowing through the first sensing resistor 41 and the second sensing resistor 42 increases, the level of the error signal decreases, so that the PWM control unit 38 shortens the ON time of the control switching element 32. The current flowing through the coil 5 is reduced. In this way, the PWM control unit 38 controls the ON time of the control switching element 32 based on the error signal to stabilize the current flowing through the coil 5 with a constant magnitude and drive the stepping motor with a constant current. be able to.

Further, in the constant current control unit 30 of the present embodiment, when the drive voltage is saturated and saturated, the current reaches a predetermined magnitude within the time excluding the OFF time 62 required for charging the switching element in the unit excitation period T. Since it does not start up, the control switching element 32 is always held in the ON state in the PWM control unit 38. As a result, the DV type constant current control as described above cannot be performed, so that when the stepping motor vibrates, the vibration of the motor cannot be suppressed by the constant current control. As a result, when the stepping motor vibrates in the saturated state of the drive voltage, the vibration of the motor causes unevenness in the rotation speed of the stepping motor, and a small amount of current flows in the circuit due to the unevenness of the rotation speed.

Therefore, in the drive device 1 of the present embodiment, the ripple current detection circuit 52 shown in FIG. 2 for detecting the current generated due to the unevenness of the rotation speed when the drive voltage is saturated is used for control. It is newly provided separately from the current detection circuit 51. Then, in the excitation pattern output unit 20, in the saturated state of the drive voltage, each unit excitation cycle T is performed by the time control unit 26 based on the ripple current (current caused by the speed unevenness) detected by the ripple current detection circuit 52. The ratio of the excitation time 61 and the OFF time (time to turn negative OFF) 62 of the coil 5 in the coil 5 is manipulated as described above. That is, when the ripple current increases, the ratio of the excitation time 61 in the unit excitation cycle T is decreased, and when the ripple current decreases, the ratio of the excitation time 61 in the unit excitation cycle T is increased.

As shown in FIG. 2, the ripple current detection circuit 52 of the present embodiment detects the voltage of the second sensing resistor 42 (voltage drop in the second sensing resistor 42) and amplifies the difference between the detected voltage and the reference voltage. First amplifier circuit (first amplifier for ripple) 53, second amplifier circuit (second amplifier for ripple) 54 that further amplifies the voltage output from the first amplifier circuit 53, and output from the first amplifier circuit 53. It has a third amplifier circuit (third amplifier for ripple) 55 that amplifies the difference between the applied voltage and the voltage output from the second amplifier circuit 54 and outputs it as a ripple current. Further, the ripple current detection circuit 52 digitizes the signal amplified by the third amplifier circuit 55 by the second A / D converter 17 and outputs the signal to the excitation pattern output unit 20.

Next, the drive device 1 of the present embodiment increases the rotation speed of the stepping motor from the state in which the stepping motor is rotated in the non-saturated state in which the drive voltage is not saturated to the saturated state in which the drive voltage is saturated. A driving method when rotating in the rotation speed region will be described.

When driving the stepping motor, the excitation pattern output unit 20 of the drive device 1 outputs a required excitation pattern signal from the excitation pattern output selector 25 to the element drive unit 12 according to a command pulse input from the outside, and also drives the element. The unit 12 controls ON / OFF of each switching element of the output stage unit 11 according to the excitation pattern signal input from the excitation pattern output selector 25.

At the same time, the constant current control unit 30 performs DV-type constant current control by switching ON / OFF of the control switching element 32 as described above. Thereby, in the unsaturated state of the drive voltage, the stepping motor can be smoothly step-driven, and as shown in FIG. 4, a required constant torque can be obtained. The graph shown in FIG. 4 is a semi-logarithmic graph showing the X-axis (motor rotation speed) on a logarithmic scale.

In this case, the excitation pattern output unit 20 stops the function of the time control unit 26, and the time control unit 26 does not control the excitation time 61 and the OFF time 62 within the unit excitation cycle T. Therefore, as shown in FIG. 6A, the minimum OFF time 62 (that is, the charging time held in the negative OFF) set for charging the capacitor is secured for each unit excitation cycle T, and the charging time is maintained. The excitation pattern signal is output at a time other than the OFF time 62 (that is, the excitation time 61).

For example, in the case of the present embodiment, the length of the unit excitation cycle T is set to 48.6 μs, and the length of the minimum OFF time 62 (charging time) is set to 600 ns (excitation time 61 at this time). The length will be 48 μs). Further, in the present embodiment, the maximum length of the OFF time 62 per unit excitation cycle T is set to 1500 ns (that is, the minimum length of the excitation time 61 is 47.1 μs). Therefore, the length of the OFF time 62 of the present embodiment can be increased or decreased in the region of 600 ns to 1500 ns by the time control unit 26.

Further, in the saturation determination unit 27 of the excitation pattern output unit 20, the PWM control unit 38 monitors whether or not there is a non-excitation state within one unit excitation cycle T, and the drive voltage applied to the stepping motor is in the non-saturation state. It is determined whether the state is the saturated state or the saturated state.

When the rotation speed of the stepping motor is gradually increased while performing the DV type constant current control as described above, the stepping motor rotates faster than the rotation speed at which the drive voltage is saturated (saturation rotation speed). As shown in, the magnitude of the torque obtained by the stepping motor decreases as the rotation speed increases.

In the drive device 1 of the present embodiment, the time control of the excitation pattern output unit 20 is performed in the rotation speed region (that is, the rotation speed region in which the drive voltage is saturated) in which the magnitude of the torque decreases as the rotation speed increases. By opening the function of the unit 26, the vibration of the stepping motor, which cannot be suppressed by the DV type constant current control, is suppressed. Hereinafter, the control of the drive device 1 when the stepping motor is rotated faster than the saturated rotation speed will be specifically described.

When the rotation of the stepping motor becomes faster than the saturation rotation speed, the saturation determination unit 27 of the excitation pattern output unit 20 determines that the drive voltage is in a saturated state, and directs the signal in the saturated state to the time control unit 26. Output. The time control unit 26 to which the saturated signal is input releases the function stop of the time control unit 26 and controls the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T.

For example, when the stepping motor rotates faster than the saturated rotation speed, the stepping motor begins to vibrate as described above. In this case, in the ripple current detection circuit 52, the first amplifier circuit 53 outputs the voltage of the first detection waveform 66 shown in FIG. 7, and further amplifies the voltage output from the first amplifier circuit 53. The second amplifier circuit 54 outputs the voltage of the second detection waveform 67 shown in FIG. 7. Further, the third amplifier circuit 55 that amplifies the difference between the output voltage of the first amplifier circuit 53 and the output voltage of the second amplifier circuit 54 outputs the third detection waveform 68 shown in FIG. 7 as a ripple current. The ripple current output from the third amplifier circuit 55 is digitized by the second A / D converter 17 and input to the time control unit 26 of the excitation pattern output unit 20. In the case of this embodiment, since the period of the ripple current is about 10 ms, it can be seen that the detected vibration frequency of the stepping motor is about 100 kHz.

The time control unit 26 in which the ripple current is input from the ripple current detection circuit 52 reduces the ratio of the excitation time 61 in the unit excitation cycle T when the input ripple current increases as indicated by the arrow 63 (the ratio of the excitation time 61 in the unit excitation cycle T). Increase the percentage of OFF time 62).

For example, when the drive voltage is in the unsaturated state, the excitation time 61 and the OFF time 62 of the unit excitation cycle T are held at the ratios shown in FIG. 6A as described above, but the ripple current increases. In the process, the time control unit 26 gradually reduces the ratio of the excitation time 61, thereby controlling the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T as shown in FIG. 6 (b). .. As a result, the voltage application time for the motor, which cannot be controlled by the constant current control unit 30, can be reduced based on the vibration (ripple current) of the motor.

On the other hand, when the ripple current input to the time control unit 26 is decreasing as indicated by the arrow 64, the ratio of the excitation time 61 in the unit excitation cycle T is gradually increased (the ratio of the OFF time 62 is gradually increased). Reduce). Thereby, the voltage application time to the motor can be increased based on the vibration (ripple current) of the motor.

In the saturated state of the drive voltage, the time control unit 26 controls the voltage application time to the motor, which cannot be controlled by the constant current control unit 30, based on the ripple current detected as described above. , Vibration generated in the voltage saturation state of the stepping motor can be effectively suppressed. As a result, the ripple current generated by the vibration of the stepping motor can be suppressed to a small extent.

For example, in the state before the vibration suppression effect by the time control unit 26 is exerted, the ripple current is detected by the third detection waveform 68 in FIG. 7, but the time control unit 26 is based on the detected ripple current. By controlling the ratio of the excitation time 61 and the OFF time 62, the amplitude of each detected waveform detected by the first amplifier circuit 53 to the third amplifier circuit 55 of the ripple current detection circuit 52 can be seen from the state shown in FIG. , As shown in FIG. 8, it is possible to make a state in which the ripple current is hardly detected (a state in which the ripple current is not generated).

Further, as described above, the time control unit 26 of the present embodiment controls the ratio of the excitation time 61 and the OFF time 62 based on the increase / decrease of the ripple current, and the time control unit 26 controls the length of the OFF time 62. The rate of change is controlled according to whether the stepping motor is accelerating or decelerating.

As a result of detailed experiments and analyzes by the present inventors, it has been clarified for the first time that the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T as described above affects the suppression of the vibration of the stepping motor. However, at the same time, it was also found that the degree of increase or decrease in the length of the OFF time 62 (rate of increase or rate of decrease) affects the suppression of vibration of the stepping motor.

For example, when the stepping motor is accelerating in a saturated state of the drive voltage, the impedance of the motor increases, so that the current flowing through the coil 5 becomes small. In this case, the time control unit 26 gently changes the ratio of the excitation time 61 and the OFF time 62 (in other words, the rate of change is reduced). On the other hand, when the stepping motor is decelerating in a saturated state of the drive voltage, the ratio of the excitation time 61 and the OFF time 62 is rapidly changed by the time control unit 26 (the rate of change is increased).

In this case, the determination of acceleration and deceleration of the stepping motor is determined by the current flowing through the first sensing resistor 41 and the second sensing resistor 42 detected in the control current detection circuit 51 (here, the detected current value). From a predetermined reference current value set in advance, as shown by the following formula (A), the shortage of the detected current value with respect to the reference current value is calculated, and the ratio of the calculated shortage to the reference current value is calculated. Calculate. In the present embodiment, the arithmetic processing related to such a shortage is performed by the excitation pattern output unit 20, but the place and means for performing the arithmetic processing in the present invention are not particularly limited.

When the numerical value calculated by the above formula (A) increases in the saturated state of the drive voltage, it is determined that the stepping motor is in the accelerating state, and the rate of change of the OFF time 62 or the excitation time 61 (that is, the amount of change / time). ) Is reduced to change the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T. On the other hand, when the numerical value of the above formula (A) decreases, it is determined that the stepping motor is in the deceleration state, the rate of change of the OFF time 62 or the excitation time 61 is increased, and the excitation time 61 and OFF in the unit excitation cycle T are increased. Change the rate of time 62. By changing the rate of change (rate of change) of the OFF time 62 or the excitation time 61 based on the change of the numerical value of the above formula (A) in this way, the vibration suppression effect of the stepping motor in the saturated state of the drive voltage is further enhanced. be able to.

As described above, in the drive device 1 of the present embodiment, the ripple caused by the vibration of the stepping motor in the rotational speed region in the saturated state of the drive voltage, where it is difficult to effectively exert the constant current control by the constant current control unit 30. By detecting the current and controlling the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T based on the detected ripple current, the current is further turned off according to the increase or decrease of the numerical value calculated by the above equation (A). By controlling the rate of change of the time 62 or the excitation time 61, the vibration generated in the stepping motor can be effectively suppressed. As a result, the stepping motor can be smoothly step-driven even in a saturated state of the drive voltage, and noise due to vibration of the stepping motor can be reduced.

In the above-described embodiment, the element drive unit 12 that drives the output stage is formed by a gate driver (dedicated IC), but in the present invention, the element drive unit 12 is formed by a transistor circuit instead of a gate driver. It may have been done. When the element driving unit 12 is a transistor circuit, it is not necessary to provide the OFF time 62 for charging as described above. In this case, for example, the length of the unit excitation cycle T is set to 48 μs, and the length of the minimum OFF time (charging time) is set to 0 ns. Further, the maximum length of the OFF time 62 per unit excitation cycle T is set to 900 ns.

Further, in the present embodiment, the PWM control unit 38 of the constant current control unit 30 digitally controls the control switching element 32, but the control by the PWM control unit 38 may be performed in analog.

(Example 1 and Comparative Example 1)
As the first embodiment, a case where the step drive of the 5-phase stepping motor is performed by using the drive device 1 of the above-described embodiment will be described. In the first embodiment, after starting the step drive of the stepping motor, the rotation speed is increased to a predetermined speed (approximately 19 rps) at which the drive voltage is saturated, and then the predetermined speed is increased. The change in the rotation speed (output frequency) of the stepping motor was measured.

In the first embodiment, the function of the time control unit 26 of the excitation pattern output unit 20 is stopped from the start of the step drive until the saturation determination unit 27 of the excitation pattern output unit 20 determines the saturation state of the drive voltage. .. Further, after the saturation determination unit 27 determines the saturation state of the drive voltage, the time control unit 26 performs a process of controlling the ratio of the excitation time 61 and the OFF time 62 in the unit excitation cycle T. The results of the rotation speed and output frequency of the stepping motor measured in Example 1 are shown in FIG.

Further, as Comparative Example 1, in the same 5-phase stepping motor as in Example 1, the function of the time control unit 26 of the excitation pattern output unit 20 was stopped even after the saturation determination unit 27 determined the saturation state of the drive voltage. FIG. 10 shows the measurement results of the rotation speed and the output frequency of the stepping motor when the state was maintained and the time control unit 26 of the present invention did not control the stepping motor even when the drive voltage was saturated. In FIGS. 9 and 10, the horizontal axis indicates “measurement time (ms)”, and the vertical axis on the left side and the vertical axis on the right side indicate “rotation speed (rps)” and “output frequency (kHz)”, respectively. Shown.

As shown in FIG. 9, in the case of the first embodiment, even if the stepping motor is step-driven at a predetermined rotation speed (approximately 19 rps) in which the drive voltage is saturated, the vibration (speed unevenness) of the motor is generated. It can be seen that it has hardly occurred. On the other hand, in the case of Comparative Example 1, it was confirmed that the vibration of the motor (speed unevenness) occurred after the drive voltage was saturated, and the vibration of the motor gradually increased.

(Example 2 and Comparative Example 2)
As the second embodiment, the rotation speed when the drive device 1 of the above-described embodiment is step-driven in a state where the drive voltage is saturated with respect to a 5-phase stepping motor having a performance different from that of the first embodiment and the first comparative example. And the output frequency was measured.

FIG. 11 shows the measurement results when the time control unit 26 controls the ratios of the excitation time 61 and the OFF time 62 after the saturation determination unit 27 determines the saturation state of the drive voltage. The measurement result when only the general DV type constant current control is performed without the control by the time control unit 26 of the present invention even in the saturated state of the drive voltage is shown.

As shown in FIGS. 11 and 12, in the case of Comparative Example 2 (FIG. 12) in which the time control unit 26 did not control the ratio of the excitation time 61 and the OFF time 62, the drive voltage became saturated. It was later observed that the motor was vibrating significantly. On the other hand, in the case of Example 2 (FIG. 11) in which the control process is performed by the time control unit 26, it can be seen that the vibration of the motor can be effectively suppressed as compared with Comparative Example 2.

As shown in Examples 1 and 2 and Comparative Examples 1 and 2 (FIGS. 9 to 12), according to the drive device 1 of the above-described embodiment, it has been difficult to suppress the vibration of the stepping motor in the past. It was confirmed that the vibration of the motor can be effectively suppressed in the rotation speed region where the drive voltage is saturated.

1 Drive device 2 Output terminal 5 Coil 11 Output stage 12 Element drive 13 Coupler circuit 16 1st A / D converter 17 2nd A / D converter 18 3rd A / D converter 20 Excitation pattern output section 21 Electric angle position management section (address) counter)
22 Rotation speed management unit (speed measurement counter)
23 Excitation cycle counter unit 24 Excitation pattern storage unit 25 Excitation pattern output selector (output selection unit)
26 Time control unit 27 Saturation judgment unit 30 Constant current control unit 31 First capacitor 32 Control switching element 33 Control element drive unit 34 Diode 35 Choke coil 36 Second capacitor 37 Current reference circuit 38 PWM control unit 41 First sensing resistor 42 2nd sensing resistor 50 Current detection circuit 51 Control current detection circuit (1st current detection circuit)
51a Amplifier circuit for control (op amp for control)
52 Ripple current detection circuit (second current detection circuit)
53 First amplifier circuit (first operational amplifier for ripple)
54 Second amplifier circuit (second operational amplifier for ripple)
55 Third amplifier circuit (third operational amplifier for ripple)
61 Excitation time (ON time)
62 OFF time 63, 64 Arrow 66 First detection waveform 67 Second detection waveform 68 Third detection waveform I1 Supply current I2 Excitation current I3 Regeneration current T unit Excitation cycle

Claims (10)

A drive device (1) that drives the stepping motor by switching the excitation of the stepping motor coil (5) by inputting a command pulse.
An output stage unit (11) having two switching elements for each output terminal (2),
The element drive unit (12) that drives the switching element and
An excitation pattern output unit (20) that outputs an excitation pattern signal to the element drive unit (12) in a unit excitation period (T) according to the command pulse,
It has a constant current control unit (30) that controls constant current by adjusting the drive voltage applied to the stepping motor.
The constant current control unit (30) includes a control current detection circuit (51) that detects the current for constant current control, and a control switching element (32) that increases or decreases the drive voltage by switching ON / OFF. Due to the vibration of the PWM control unit (38) that switches ON / OFF of the control switching element (32) based on the detection current detected by the control current detection circuit (51), and the vibration of the stepping motor. It is provided with a ripple current detection circuit (52) that detects the ripple current included in the current flowing through the coil (5).
The excitation pattern output unit (20) has the unit excitation of an excitation time (61) for applying the drive voltage to excite the coil (5) and an OFF time (62) for not exciting the coil (5). It has a time control unit (26) that controls the ratio in the period (T),
The time control unit (26) reduces the ratio of the excitation time (61) when the ripple current detected by the ripple current detection circuit (52) increases, and the excitation time when the ripple current decreases. A drive device characterized by increasing the proportion of (61). The ripple current detection circuit (52) detects a voltage drop of a sensing resistor (42) through which an exciting current (I2) that excites the coil (5) and a regenerative current (I3) from the coil (5) flow. The first amplifier circuit (53) that amplifies the voltage, the second amplifier circuit (54) that further amplifies the voltage output from the first amplifier circuit (53), and the first amplifier circuit (53). The driving device according to claim 1, further comprising a third amplifier circuit (55) that amplifies the difference between the voltage and the voltage output from the second amplifier circuit (54) and outputs the difference as the ripple current. The excitation pattern output unit (20) has a saturation determination unit (27) that determines a non-saturated state in which the drive voltage is not saturated and a saturated state in which the drive voltage is saturated.
The time control unit (26) controls the ratio of the excitation time (61) when the determination by the saturation determination unit (27) is in the saturated state, and the determination by the saturation determination unit (27) is not. The driving device according to claim 1 or 2, wherein the control of the ratio of the excitation time (61) is stopped in the saturated state. The time control unit (26) reduces the rate of change that increases or decreases the ratio of the excitation time (61) when the current detected by the control current detection circuit (51) increases, and detects the current. The drive device according to any one of claims 1 to 3, which increases the rate of change when the current decreases. A ripple current detection circuit (52) provided in a drive device that drives a stepping motor.
The first amplifier circuit (53) that detects and amplifies the voltage drop of the sensing resistor (42) through which the exciting current (I2) that excites the coil (5) and the regenerative current (I3) from the coil (5) flows.
A second amplifier circuit (54) that further amplifies the voltage output from the first amplifier circuit (53), and
The difference between the voltage output from the first amplifier circuit (53) and the voltage output from the second amplifier circuit (54) is amplified to form a ripple current included in the current due to the vibration of the stepping motor. A ripple current detection circuit having a third amplifier circuit (55) for output. It is a drive method for driving the stepping motor by switching the excitation to the coil (5) of the stepping motor by inputting a command pulse.
An excitation pattern signal is output from the excitation pattern output unit (20) in a unit excitation cycle (T) according to the command pulse, and the switching element of the output stage unit (11) is turned on by the element drive unit (12) according to the excitation pattern signal. Step driving the stepping motor by switching / OFF,
In the constant current control unit (30), the control current detection circuit (51) detects the constant current control current, and the control switching element (32) is switched ON / OFF based on the detected current. Performing constant current control by adjusting the drive voltage applied to the stepping motor,
The ripple current detection circuit (52) provided in the constant current control unit (30) detects the ripple current included in the current flowing through the coil (5) due to the vibration of the stepping motor driven in steps. as well as,
Time to control the ratio of the excitation time (61) for applying the drive voltage to excite the coil (5) and the OFF time (62) for not exciting the coil (5) in the unit excitation cycle (T). When the ripple current detected by the control unit (26) increases, the ratio of the excitation time (61) of the drive voltage to the unit excitation cycle (T) is reduced, and when the ripple current decreases, the ratio is reduced. A driving method comprising increasing the proportion of the excitation time (61) in the unit excitation period (T). A sensing resistor (I3) through which an exciting current (I2) that excites the coil (5) and a regenerative current (I3) from the coil (5) flow by the first amplifier circuit (53) of the ripple current detection circuit (52). 42) Detecting and amplifying the voltage drop,
The voltage output from the first amplifier circuit (53) is further amplified by the second amplifier circuit (54) of the ripple current detection circuit (52), and
The third amplifier circuit (55) of the ripple current detection circuit (52) amplifies the difference between the voltage output from the first amplifier circuit (53) and the voltage output from the second amplifier circuit (54). The driving method according to claim 6, further comprising outputting as the ripple current. The saturation determination unit (27) provided in the excitation pattern output unit (20) determines between an unsaturated state in which the drive voltage is not saturated and a saturated state in which the drive voltage is saturated, and
The time control unit (26) controls the ratio of the excitation time (61) when the determination by the saturation determination unit (27) is in the saturated state, and the determination by the saturation determination unit (27) is not. The driving method according to claim 6 or 7, wherein the control of the ratio of the excitation time (61) is stopped in the saturated state. When the current detected by the control current detection circuit (51) is increased by the time control unit (26), the rate of change for increasing or decreasing the ratio of the excitation time (61) is reduced and detected. The driving method according to any one of claims 6 to 8, which comprises increasing the rate of change when the current decreases. The exciting current (I2) that excites the coil (5) of the stepping motor and the regeneration from the coil (5) by the first amplification circuit (53) of the ripple current detection circuit (52) provided in the drive device of the stepping motor. Detecting and amplifying the voltage drop of the sensing resistor (42) through which the current (I3) flows,
The voltage output from the first amplifier circuit (53) is further amplified by the second amplifier circuit (54) of the ripple current detection circuit (52), and
The third amplifier circuit (55) of the ripple current detection circuit (52) amplifies the difference between the voltage output from the first amplifier circuit (53) and the voltage output from the second amplifier circuit (54). A method for detecting a ripple current, which comprises outputting the current as a ripple current included in the current due to the vibration of the stepping motor.

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