JP2015177674A - Control device for stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a stepping motor capable of reducing radiation/conduction noise of the stepping motor that is driven by a constant current control system.SOLUTION: A control device includes a driving part 9 and a control part 8. After a voltage is applied to a coil of a stepping motor 1 and a current value flowing in the coil is made achieve a reference value, ON/OFF of the voltage is repeated by the driving part 9, a constant current within a fixed range is made flow to the coil for excitation and the stepping motor 1 is driven. In accordance with an estimated time that estimates a time of achievement for the current value to achieve the reference time after the application of the voltage to the coil on the basis of a measured temperature that is measured by a temperature measuring circuit 6a and a measured voltage that is measured by a voltage measuring circuit 7a, the control part 8 sets an excitation time for excitation by constant current flow. The driving part 9 drives the stepping motor 1 by making the constant current flow for the excitation time.

Description

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

  A control device for controlling the driving of the stepping motor is disclosed in Patent Document 1. The stepping motor is driven by applying a voltage to the coil of the stepping motor, causing the current to flow to the target value, and then switching the applied voltage on and off to allow a constant excitation current to flow to the coil. There is known a constant current drive system that excites.

JP 2000-236696 A

  The above constant current driving method can suppress heat generation in the coil of the stepping motor and the driving circuit. However, radiation / conduction noise is generated in the coil and drive circuit of the stepping motor by repeatedly turning on and off the voltage.

  In addition, although the time for the current flowing through the coil to reach the target value varies depending on the voltage value applied to the coil, in the conventional constant current driving method, excitation is completed by applying voltage to the coil (excitation for one step). The time until (end) is defined (fixed) in advance. Therefore, when a high voltage is applied to the coil, the current rise time is shortened compared to when a lower voltage is applied, and the excitation time (the time to repeat ON / OFF of the voltage) becomes unnecessarily long. Conducted noise may be noticeable.

  An object of the present invention is to provide a constant current drive type stepping motor control device capable of reducing discharge and radiation noise.

Means for Solving the Problems and Effects of the Invention

The control device of the stepping motor of the present invention is
After applying a voltage to the coil of the stepping motor and causing the current value flowing through the coil to reach the reference value, the voltage is turned ON and OFF repeatedly, and a constant current within a certain range is passed through the coil to excite it, thereby driving the stepping motor. In a control device for a stepping motor having a drive unit,
A temperature measurement unit for measuring the temperature of the stepping motor;
A voltage measuring unit for measuring the voltage;
A time estimation unit for estimating the arrival time at which the current value reaches the reference value after applying a voltage to the coil based on the measurement temperature measured by the temperature measurement unit and the measurement voltage measured by the voltage measurement unit;
In accordance with the estimated time estimated by the time estimation unit, a time setting unit for setting an excitation time for exciting by flowing a constant current, and
The driving unit drives the stepping motor by passing an excitation time and a constant current.

  In the stepping motor control device of the present invention, the arrival time from when the voltage is applied to the coil until the current value flowing through the coil reaches the reference value is estimated, and the excitation time for exciting with a constant current is set based on the arrival time. . That is, since the excitation time is set based on the arrival time that varies according to the voltage applied to the coil, an appropriate excitation time can be set according to the voltage. Therefore, when a relatively high voltage is applied to the coil, it is possible to shorten an unnecessarily long excitation time and reduce radiation / conduction noise.

  In the embodiment of the present invention, the time setting unit sets a calculation time obtained by multiplying the estimated time by a predetermined first constant as the excitation time. According to this, it is possible to set an appropriate excitation time corresponding to the estimated time.

  In addition, the time setting unit has a comparison unit that compares the calculated time with a predetermined minimum excitation time so that the stepping motor does not step out. If the calculation time is greater than the minimum excitation time according to the comparison result of the comparison unit, the time setting unit calculates Set the time to the excitation time. On the other hand, when the calculation time is shorter than the minimum excitation time based on the comparison result of the comparison unit, the minimum excitation time is set as the excitation time. According to this, the stepping motor can be prevented from stepping out when the excitation time becomes the minimum excitation time.

  Furthermore, the temperature measurement unit includes a temperature correction unit that multiplies the measured temperature by a predetermined second constant, and uses the correction temperature corrected by the temperature correction unit as the measurement temperature. According to this, the arrival time can be estimated in consideration of the rising temperature of the stepping motor that rises by driving, and an appropriate excitation time can be set.

The conceptual diagram which shows an example of the stepping motor used for this invention. The block diagram which shows an example of the outline of the electric constitution of the control apparatus of this invention. The time chart which shows the relationship between the applied voltage and the applied current which were applied to the A-phase and B-phase coils of the stepping motor by the control device of the present invention. The flowchart which shows an example of a process of the program of FIG. The graph which shows the relationship between the correction coefficient which correct | amends measurement temperature, and the time after an excitation start. The time chart which shows a series of fluctuation | variation of the electric current value when applying a voltage to the coil of a stepping motor and sending a constant current through a coil. The time chart corresponding to FIG. 6A at the time of applying a voltage higher than FIG. 6A. Two time charts showing the relationship between applied voltage and applied current applied to the A-phase and B-phase coils of a stepping motor controlled by a conventional control device (same conditions except for applied voltage). The time chart which shows the relationship between the applied voltage and the applied current which were applied to the A phase and B phase coil of the stepping motor controlled by the control device of the present invention and the conventional control device. Explanatory drawing explaining an example of arrangement | sequence data of the estimated time set by motor temperature and battery voltage.

  An example of the stepping motor 1 used in the present invention shown in FIG. 1 includes a rotor 2 (for example, a predetermined magnet) and a two-phase coil 3 (A-phase coil 3a) that rotates the rotor 2 by magnetizing an electromagnet with an exciting current. And a B-phase coil 3b), and a bipolar motor that rotates the rotor 2 by switching the directions of the excitation currents flowing through the coils 3a and 3b and the coils 3a and 3b in a predetermined order. As shown in FIG. 2, the stepping motor 1 includes a thermistor 4 that detects the motor temperature of the motor body (for example, detects the temperature of the coil 3).

  The stepping motor 1 is controlled by the control device 5 according to an example of the present invention. The control device 5 includes a temperature measurement unit 6 that measures the temperature of the stepping motor 1, a voltage measurement unit 7 that measures the battery voltage that drives the stepping motor 1, a control unit 8 that controls the stepping motor 1, and a control unit 8. The drive part 9 which drives the stepping motor 1 according to the control signal from is provided.

  The temperature measurement unit 6 is connected to the thermistor 4 and is configured as a temperature measurement circuit 6 a that measures the motor temperature of the stepping motor 1 (the temperature of the coil 3) based on an electrical signal from the thermistor 4.

  The voltage measurement unit 7 is connected to a battery 10 that drives the stepping motor 1 and is configured as a voltage measurement circuit 7 a that detects the battery voltage of the battery 10.

  The control unit 8 is configured as a microcomputer including a CPU 8a, a memory 8b, a ROM 8c, a RAM 8d, and a bus 8f that connects these to an I / O port 8e (input / output interface) as main components. The I / O port 8e includes: The temperature measurement circuit 6a, the voltage measurement circuit 7a, and the drive unit 9 are connected.

  For example, the CPU 8a constantly monitors the motor temperature and the battery voltage measured through the temperature measurement circuit 6a and the voltage measurement circuit 7a and stores them in the memory 8b. The memory 8b stores the temperature data of the motor temperature, the voltage data of the battery voltage, and the like. Is memorized. In the ROM 8c, a time estimation program P1 for estimating the arrival time for the current flowing through the coil 3 to reach the reference value from the temperature data and voltage data stored in the memory 8b, and a current through the coil 3 according to the arrival time. A time setting program P2 for setting the excitation time for excitation and a drive program P3 for exciting the excitation time and driving the stepping motor 1 are stored. Various data such as minimum excitation time data D1 prepared in advance as the shortest excitation time (excitation time for one step) necessary for the stepping motor 1 not to step out is also stored.

  The time estimation program P1 reads and calculates temperature data (motor temperature) stored in the memory 8b and corrects it to a predetermined temperature, and performs a predetermined calculation based on the estimated arrival time (estimated time). A calculation program for deriving the calculation time; The time setting program P2 has a comparison program that compares the calculated time with the minimum excitation time.

  Each of the programs stored in the ROM 8c is executed by the CPU 8a using the RAM 8d as a work area, and the CPU 8a reads temperature data, voltage data, and the like from the memory 8b as necessary. The control unit 8 corresponds to a time estimation unit and a time setting unit of the present invention.

  A control signal is transmitted from the control unit 8 to the drive unit 9 in accordance with the execution of the various programs. The drive unit 9 drives the stepping motor 1 according to the control signal. For example, in the control unit 8, when an excitation time for exciting the coil 3 by flowing an excitation current is set by executing a program, an excitation switching signal is sent from the control unit 8 to the drive unit 9 in accordance with the set excitation time. Sent.

The drive unit 9 drives the stepping motor 1 by controlling the excitation current (current flow direction) flowing through the coils 3a and 3b and the coils 3a and 3b that flow excitation current according to the excitation switching signal transmitted from the control unit 8. The circuit 9a is configured. As shown in FIG. 3, the driver circuit 9a applies a battery voltage (V ₀ or −V _{0 in the} drawing) to the coils 3a and 3b and sets a current value flowing through the coils 3a and 3b as a reference value (I ₀ or −I _{0 in the} drawing). And a known constant current circuit that excites the coil 3 by passing a constant current within a certain range by repeating ON and OFF of the voltage.

The manner in which the constant current flows through the driver circuit 9a will be specifically described. A positive applied voltage (V _O ) is continuously applied to the B-phase coil 3b for a predetermined period corresponding to the beginning of the “excitation state 1” section shown in the figure, whereby a current flowing through the B-phase coil 3b rises. . When the current value of the rising current becomes the reference value (I _O ), ON / OFF of the applied voltage (V _O ) applied to the B-phase coil 3b is repeated (PWM control) within a certain range by repeating ON-OFF. A constant current (a constant current equal to or greater than the target current value) is passed through the coil 3b, and excitation is performed for the excitation time (T _O ) (“excitation state 1 → 2” in the figure).

At the end of the excitation time, the negative applied voltage (−V _O ) is continuously applied to the B-phase coil 3b for a predetermined period in response to the beginning of the “excited state 3” section shown in the figure. Current flowing in the coil 3b rises in the negative direction. When the current value of the rising current reaches the reference value (-I _O ), the ON / OFF of the applied voltage (-V _O ) applied to the B-phase coil 3b is repeated (PWM control) to be constant. A constant current within the range is supplied to the coil 3b, and excitation is performed for the excitation time (T _O ) ("excitation state 3 → 4" in the figure).

Upon completion of the excitation time, the operation returns to the beginning of the “excitation state 1” section shown in the figure. On the other hand, the coil 3a of the phase A, for example, after the positive applied voltage (V _O) is applied continuously for a predetermined time period to the coil 3a shown "excited state 4" in response to the beginning of the section of the A phase, a predetermined By performing the PWM control, excitation time (T _O ) and a constant current are passed through the coil 3a for excitation (illustration “excitation state 4 → 1”). At the end of the excitation time, a negative applied voltage (−V _O ) is applied for a predetermined period this time corresponding to the beginning of the section of “excitation state 2” in the figure, and the excitation time ( T _O ), a constant current is passed through the coil 3a to excite it ("excitation state 2 → 3" shown in the figure), and upon completion of the excitation time, return to the beginning of the section "excitation state 4" shown.

  Therefore, in the example shown in FIG. 3, a constant current (positive current) is passed through the B-phase coil 3b for excitation (excitation state 1), and a constant current (negative current) is passed through the A-phase coil 3a for excitation. (Excitation state 2) → Excitation (excitation state 3) by passing a constant current (negative current) through the B phase coil 3b → Excitation (excitation state 4) by passing a constant current (positive current) through the A phase coil 3a ) → Excitation (excitation state 1) by passing a constant current (positive current) through the B-phase coil 3b, and alternate (partially overlapping periods) for the A-phase and B-phase coils 3a and 3b. The stepping motor 1 is driven by energizing alternately by flowing current.

  Next, an example of the contents of the various programs will be described with reference to the flowchart of FIG. FIG. 4 shows a series of processes for setting the excitation time for exciting the A-phase and B-phase coils 3a and 3b by applying current. The time setting program P2 in the ROM 8c of FIG. 2 is a series of processes that are read and executed by the CPU 8a using the work memory of the RAM 8d as a work area. This process is repeatedly executed until the stepping motor 1 stops after the CPU 8a receives a driving signal for driving the stepping motor 1, for example.

  When the drive signal is input to the CPU 8a, the CPU 8a reads the latest motor temperature temperature data monitored through the temperature measurement circuit 6a from the memory 8b to acquire the motor temperature (step S1). Next, it is determined whether or not a predetermined time has elapsed since the start of excitation of the stepping motor 1 (rotation of the stepping motor 1) (step S2).

In general, the motor temperature rises to near a certain temperature as the rotation (drive) of the motor continues. Therefore, for example, as shown in FIG. 5, if the excitation (rotation) of the stepping motor 1 is started and less than a predetermined time (T ₁ ), a positive constant (a ) To correct the motor temperature (measured temperature) (step S2 ′) and proceed to step S3. As a result, it is possible to control the temperature increase. On the other hand, when a predetermined time (T ₁ ) has elapsed since the excitation (rotation) of the tapping motor 1 was started, the process proceeds to step S3.

  In step S3, the resistance values of the coils 3a and 3b are calculated from the motor temperature (uncorrected measured temperature) or the corrected motor temperature (corrected temperature). For example, the resistance value of the coils 3a and 3b based on the motor temperature is calculated from the resistivity of the copper wire at 25 ° C. and the resistance temperature coefficient of the copper wire per 1 ° C.

  When the resistance value is calculated, the voltage data of the latest battery voltage monitored by the CPU 8a through the voltage measurement circuit 7a is read from the memory 8d to acquire the battery voltage (step S4).

Next, the arrival time until the current flowing through the coils 3a and 3b reaches the reference value (I _O ) is estimated from the acquired battery voltage and the calculated resistance values of the coils 3a and 3b. For example, assuming that the coils 3a and 3b are circuits in which a resistor and a coil are connected in series, the applied voltage (V _O ) of the coils 3a and 3b, the inductance of the coils 3a and 3b, and the measured resistance values of the coils 3a and 3b The arrival time is calculated from the current value in the steady state. The calculated calculation result is set as the estimated arrival time (step S5). The arrival time may be acquired for each coil 3, or may be acquired from one of the coils 3 and the arrival time common to both.

When the arrival time is acquired, a calculation time obtained by multiplying the arrival time by a predetermined constant is calculated. For example, as shown in FIG. 6A, an arrival time (t ₁ ) until the current reaches the reference value (I _O ), and an excitation time (t ₁ ) for exciting by passing a constant current after reaching the arrival time (t ₁ ) ₀ ) current model is prepared in advance. The calculation time (t ₀ ′) is calculated based on the ratio between the arrival time (t ₁ ) of the current model and the estimated arrival time (t _{2 in} FIG. 6B) (step S 6). Therefore, an appropriate calculation time can be set corresponding to the arrival time.

  When the calculation time is calculated, the corresponding minimum excitation time data D1 is read from the ROM 8c, and the lengths of the calculated time and the minimum excitation time are compared. If the calculation time is equal to or greater than the minimum excitation time (calculation time ≥ minimum excitation time), set the calculation time to the excitation time. If the calculation time is less than the minimum excitation time (calculation time <minimum excitation time), set the minimum excitation time to the excitation time. Set. Therefore, at least the minimum excitation time is excited, and the stepping motor 1 can be prevented from stepping out.

  When the excitation time is set, an excitation switching signal corresponding to the excitation time is transmitted from the control unit 8 to the drive unit 9 (driver circuit 9a), and the drive of the stepping motor 1 is controlled. The series of processes described above are repeatedly executed, for example, while the stepping motor 1 is rotating.

Focusing on the B-phase coil in the conventional control device as shown in FIG. 7, when the applied voltage is V ₁ (V ₂ > V ₁ ), it is synchronized with the start of the “excitation state 1” section shown The applied voltage (V ₁ ) is applied, and then the PWM control is performed to apply the applied voltage (V ₁ ) until the end of the “excited state 2” section shown in the figure. On the other hand, when the applied voltage is _{V 2 (V 2> V 1} ) is for applying an applied voltage _{(V 1)} by the same period as the applied voltage _{(V 2),} reaching to reach the reference value _{(I 1)} Excess PWM control is executed by the time difference (ΔT), and radiation and conduction noise are generated in the coil and driver circuit.

On the other hand, the control device 5 of the present invention sets the calculation time (t ₀ ′) (excitation time) according to the arrival time (t ₂ ) as shown in FIG. 6B. Therefore, when a relatively high applied voltage (V ₀ ) is applied to the coil as shown in FIG. 8, the excitation time is set shorter than that of the conventional control device, and the excessively long excitation time is shortened. Conductive noise can be reduced.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the specific description, and the illustrated configuration, processing, and the like may be appropriately combined and implemented within a technically consistent range. It is possible, and certain elements and processes can be replaced with known forms.

In the above embodiment, the calculation time is calculated, but as shown in FIG. 9, the measured battery voltage and the motor temperature fall within the applicable range (battery voltage (V0 to V1, V1 to V2...), Motor temperature (T0 to T1). , T1 to T2 · · ·)) in association with the identified calculated time _{(t 00,} t 01 ···) stored such in the ROM8c sequence data, from the voltage data and temperature data CPU8a is read from the memory 8b The calculation time may be acquired to reduce the processing load on the CPU 8a.

  In the above embodiment, the temperature of the coil 3 is the motor temperature of the stepping motor 1, but the motor temperature may be measured from other parts other than the coil 3 such as the surface temperature of the motor. In addition, when the stepping motor 1 is used as an opening / closing means for an adjustment valve that adjusts the refrigerant flow rate of the car air conditioner, the temperature of the refrigerant may be measured as the motor temperature.

  When the control device 6 is used for a vehicle, it is configured as a battery 10 that can be charged by a charging means such as an alternator, so that the applied voltage (voltage of the battery 10) is different each time the stepping motor 1 is driven. Even in the case, it is possible to excite an appropriate excitation time.

  In the above description, the control unit 8 is configured as a microcomputer, but the control unit 8 and the drive unit 9 may be configured by an IC. Further, although two phases are exemplified as the winding of the coil 3, one phase, three phases, four phases, etc. may be used. The excitation method of the stepping motor 1 may be any method of 1-phase excitation, 1-2-phase excitation, 2-phase excitation. Furthermore, although the bipolar system was illustrated above, a unipolar system may be used.

1 Stepping motor 2 Rotor 3 Coil (A phase coil 3a, B phase coil 3b)
4 Thermistor 5 Control Device 6 Temperature Measurement Unit (Temperature Measurement Circuit 6a)
7 Voltage measurement part (Voltage measurement circuit 7a)
8 Control unit 9 Drive unit 10 Battery

Claims (5)

After applying a voltage to the coil of the stepping motor and causing the current value flowing through the coil to reach a reference value, the voltage is turned on and off repeatedly, and a constant current within a predetermined range is passed through the coil to excite the stepping motor. In a control device for a stepping motor having a drive unit for driving a motor,
A temperature measuring unit for measuring the temperature of the stepping motor;
A voltage measuring unit for measuring the voltage;
A time estimation unit for estimating an arrival time at which the current value reaches the reference value after applying the voltage to the coil based on the measurement temperature measured by the temperature measurement unit and the measurement voltage measured by the voltage measurement unit; ,
In accordance with the estimated time estimated by the time estimation unit, a time setting unit that sets an excitation time for exciting by flowing the constant current, and
The stepping motor control apparatus, wherein the driving unit drives the stepping motor by passing the excitation time and the constant current.   The stepping motor control device according to claim 1, wherein the time setting unit sets a calculation time obtained by multiplying the estimated time by a predetermined first constant as the excitation time.   The time setting unit includes a comparison unit that compares the calculated time with a predetermined minimum excitation time so that the stepping motor does not step out, and the calculated time is calculated based on a comparison result of the comparison unit. In the above case, the stepping motor control device according to claim 2, wherein the calculation time is set to the excitation time.   4. The stepping motor control device according to claim 3, wherein when the calculated time is shorter than the minimum excitation time based on a comparison result of the comparison unit, the minimum excitation time is set to the excitation time.   The temperature measuring unit includes a temperature correcting unit that multiplies the measured temperature by a predetermined second constant, and uses the corrected temperature corrected by the temperature correcting unit as the measured temperature. The stepping motor control device according to any one of the preceding claims.

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