JPS6031199B2 - Stepping motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in drive circuits for various stepping motors.

For example, considering a certain kind of stepping motor, the stator has a pair of excitation coils that are orthogonal to each other and are connected in series to each other so as to face each other through the center of the rotor and simultaneously generate magnetic fields in the same direction. The intensity is constant due to these two sets of excitation circuits, but
The direction is the angle formed by the central axis of the excitation circuit, that is, 90 degrees.
There is a type of stepping motor in which a rotating magnetic field that changes in steps by an integer of 1 is formed, and a rotor is rotated in steps following this rotating magnetic field.

There are various types of drive circuits that drive this type of stepping motor, but for example, each excitation circuit is followed by a switch circuit network that can switch the direction of the excitation current in both forward and reverse directions. A selection circuit or control circuit is provided to match the current flowing through the excitation circuit to one of several reference values, and these control the direction and magnitude of the current flowing through each excitation circuit in a stepwise manner. However, a magnetic field that rotates in a stepwise manner with the above-mentioned constant strength is generated to control the rotation angle of the rotor.

However, in conventionally known drive devices, the control of the excited chordal flow is not perfect, the error that occurs for each phase angle is large, and temperature drift, etc. cannot be ignored, so errors in the motor's pull-in torque, escape torque, rotation angle, etc. was big.

The reason will be explained below.

The conventional drive circuit includes a switch circuit network that is connected between each excitation circuit and a drive DC power source and can switch the direction of current flowing through the excitation circuit in both forward and reverse directions, and A current control switch inserted in series in each excitation circuit to control the current flowing through the excitation coil, and control for sequentially and rotationally switching each switch of the switch circuit network in response to a pulse signal output from an appropriate drive control circuit. circuit, a reference voltage generation circuit capable of outputting voltage signals of multiple stages, and a reference voltage generation circuit provided for each excitation circuit, which generates the reference voltage in response to a pulse signal having a higher repetition frequency than the pulse signal output from the drive control device. A selection circuit that sequentially selects and outputs the output of the output circuit, a resistor inserted in series for each of the excitation circuits, and a smoothing circuit provided for each resistor to smooth the terminal voltage of each of the resistors. , an excitation device that compares the output of each of the smoothing circuits with the output of the selection circuit given in response, and oscillates a command signal to open the current control switch of the corresponding excitation circuit only when the former is less than or equal to the latter; It consisted of a current control circuit.

In the above circuit, each excitation circuit is connected to a DC power supply via a current control switch and a current direction changeover switch, and the current direction changeover switch The reference voltage applied to each excitation coil is switched by a command pulse having a repetition frequency of about 2, and the reference voltage applied to each excitation coil is switched by a command pulse having a repetition frequency N times the above-mentioned command pulse (where N is the number of electrical divisions).

On the other hand, the on/off repetition frequency of the current control switch is usually limited to about several tens to 100 KH2 due to circuit characteristics.

Therefore, even at this level of repetition frequency, if the number of divisions N of the stepping motor is not very large and the stepping motor is driven at that rotation speed, the current control switch will change during the period when the reference voltage is maintained at one reference value. is turned on and off over several liters of time, so there is little problem.

However, since this circuit is essentially a low frequency circuit, it has poor frequency response characteristics and has the problems described above.
In particular, when the rotation speed or torque fluctuates, malfunctions sometimes occur.

The present invention has been made with the above-mentioned in mind, and its object is to provide a drive circuit for this type of stepping motor that can reliably control the excitation box current with a simple circuit, and in particular, to An object of the present invention is to provide an improved circuit so that step driving can be reliably performed.

Therefore, the gist of the present invention is to make the excitation current into pulses with a repetition frequency much higher than the step period, thereby increasing the frequency response of the entire circuit, thereby improving the characteristics of the stepping motor. .

The details of the present invention will be explained below with reference to the drawings.

The drawing is a circuit diagram showing an embodiment of a stepping motor drive circuit according to the present invention.

Therefore, in the figure, 1 is the above-mentioned stepping motor,
Reference numeral 2 designates the rotor, and reference numerals 3, 3' and 4, 4' designate two pairs of excitation coils constituting an excitation circuit.

Further, 5 to 8 and 9 to 12 are excitation coils 3, respectively.
, 3' and 4, 4', switching elements 113 and 14 constituting a switch network for switching the directions of the excitation currents open and close the excitation circuits of the excitation coils 3, 3' and 4, 4', respectively. 15 and 16 are resistors inserted to detect each excitation current, and 17 is a control element for reading command information signals from a recording tape of a numerical control device, including a step command pulse oscillator, etc. an output device; 18 is a signal conversion device that converts and outputs the command information signal into, for example, a parallel binary code signal; 19 and 20 are isolators; 21 is a reference voltage generation circuit that generates a plurality of reference voltages; 22 and 23 are IC switches; 24 and 25 are excitation direction control circuits that control the opening and closing states of switching elements 5 to 8 and 9 to 12, respectively, which switch and control the excitation direction; 26 and 27 are resistors 15;
, a smoothing circuit for smoothing the terminal voltage of 16, 28 and 29
is a comparison circuit, 30 is a high frequency pulse oscillator, 31 and 32
is an operational amplifier that performs signal amplification along with gate circuit operation,
33 is an excitation power source. Since the excitation circuits for the excitation coils 3 and 3' and the excitation circuits for the excitation coils 4 and 4' are completely the same, only the former will be explained.

The excitation coils 3 and 3' are connected in series to form one excitation circuit, to which a circuit consisting of switching elements 5 and 8 and a circuit consisting of switching elements 7 and 6 are connected in series and antiparallel to each other. , a known bridge circuit is formed. The pulse oscillator 30 has two excitation coils 3, 3
' and 4.4' is an excitation signal source common to the operational amplifier 3 whose output is controlled by comparator circuits 28 and 29.
The signal is input as a control signal to each switching element 13 and 14 having a power supply 33 via terminals 1 and 32.

The output side terminal of the switching element 13 is connected to the connection point between the switching elements 5 and 7, and thereby the output current of the power supply 33 is supplied. In addition, switching elements 6 and 8
The connection point is grounded via an inserted resistor 16 for exciting current detection.

On the other hand, when the Q output of the excitation direction control circuit 24 is in state 1, switching elements 5 and 8 are conductive, and switching elements 6 and 7 are non-conductive, but conversely, when the Q output is in state 1, switching Elements 6 and 7 are conductive, and elements 5 and 8 are non-conductive.

Therefore, if the signal from the comparator circuit 28 is currently being output, the switching element 13 is turned on and off according to the output pulse from the pulse oscillator 30, and when the Q output is in state 1, the switching element 5 → excitation It passes through the ionization circuit of coil 3→switching element 3'→switching element 8→insertion resistor 16, and when the Q output is in state 1, switching element 7→excitation coil 3'→switching element 3→switching element 6→insertion resistor 1
The pulse excitation current passes through the turtle path 6 to the coils 3 and 3'.
flows from the power supply 33.

Therefore, when the output of the excitation direction control circuit 24 is reversed,
The excitation directions of the excitation coils 3, 3' are reversed. The magnitude of the average excitation current is determined by the comparison control circuit 28 as described later.
is controlled or set by the output signal of Similarly, the excitation coils 4 and 4' are also excited by the output pulse from the switching element 14, which is turned on and off by the output of the pulse oscillator 30.

The switching elements 9, 10, 11, and 12 are controlled by the output of the excitation direction control circuit 25, and the magnitude of the average excitation current is controlled or set by the output signal of the comparison control circuit 29. In the above case, the oscillation frequency of the pulse oscillator 30 is set to, for example, a high frequency of IMHZ, and therefore the excitation current supplied to each excitation circuit is like a pulsating flow of high frequency pulses of IMHz.
The magnitude of the average excitation current will be controlled in the same way as in the conventional three-way system. That is, the switching elements 13 and 14
The magnitude of the output excitation current is controlled by the duty factor of the output signal of the operational amplifiers 31 and 32 into which the oscillation signal pulse of the pulse oscillator 30 and the signals of the comparison circuits 28 and 29 are input. .29, one of, for example, five levels of voltage signals provided in the reference voltage generation circuit 21 is passed through the signal conversion device 18, and the output voltage of the IC switches 22 and 23 selected by the drive control device 17 is converted to the voltage signal for the comparison. It is input to the circuits 28 and 29 and controlled so that the average current of the corresponding excitation circuit becomes a value corresponding to one of the reference values in the above five stages.

In this case, setting signals of the same level are not normally input to the comparison circuits 28 and 29. As described above, comparison circuits 28 and 2
9, switching is performed by the outputs of the circuits 28 and 29 and the output of the oscillator 30 while the signal voltages of a certain level are input as set voltages from the reference voltage generation circuit 21 via the respective IC switches 22 and 23. Elements 13, 14
When the current is suitable, an exciting current starts to flow through the exciting coils 3, 3' and 4, 4'.
, 16 and appearing at their terminals are smoothed by smoothing circuits 26 and 27, respectively, and fed back into the comparison circuits 28 and 29, and as the feedback input signal increases from 0, the circuit The switching element 13 is configured to reduce the output signals of the circuits 28 and 29 or to make the outputs of the circuits 28 and 29 zero when the feedback input signal increases and becomes the same as the set signal voltage input from the IC switches 22 and 23. . 13 and 14 are turned off, the excitation currents of the excitation coils 3, 3' and 4, 4' are cut off, the detection signals of the resistors 15 and 16 disappear, and the smoothing circuit 2
Since the signals inputted to the circuits 28 and 29 from the circuits 6 and 27 also disappear, the switching elements 13 and 14 are turned on again.

On/off of such switching elements 13 and 14,
That is, the excitation current is turned on and off at a repetition frequency that is much lower than the oscillation frequency IMHZ of the oscillator 30 but much higher than the number of steppings of the rotor, for example, around 10 KH2.
14, the rotor does not rotate, and such control continues even after the input setting voltage input from the reference voltage generation circuit 21 to the comparison circuits 29, 29 is changed by switching the IC switches 22, 23. Since the excitation current is changed in the same manner, the excitation current can be controlled simply by switching the IC switches 22 and 23 without taking any additional measures.

That is, for example, the higher the input set voltage from the generation circuit 21 to the comparator circuits 28 and 29, the higher the switching elements 13 and 14.
The nozzle on/off frequency usually becomes lower, and conversely, the lower the input setting voltage, the lower the nozzle on/off frequency of the switching elements 13 and 14 becomes.
The off frequency is usually high.

Setting control of the average excitation current for the excitation coils 3, 3' and 4, 4' is based on the magnitude of the voltage signal selected by the IC switches 22, 23 and input from the reference voltage generation circuit 21 to the comparison circuits 28, 29, and the above-mentioned It is determined by the on/off frequencies of the switching elements 13 and 14 such as.

The IC switches 22 and 23 are switched via the signal conversion device 18 in response to a command signal from the output 18 of the numerical control device 17, and the same command signal is also input to the excitation direction control circuits 24 and 25. The switching elements 5 to 8 and 9 to 12 are switched and controlled.

Therefore, when the switching elements 13 and 14 are repeatedly turned on and off as described above, the excitation coils 3,
A predetermined excitation current corresponding to the selected set voltage of the generating circuit 21 selected by the IC switches 22, 23 flows through the excitation coils 3' and/or 4, 4'. A composite magnetic field determined by the direction and magnitude of these currents is generated in the center, and the magnetic poles of the rotor 2 are directed in the direction of this composite magnetic field.

The direction and magnitude of this composite magnetic field are determined by the output device 1.
This corresponds to a count value of 8, that is, a binary code signal i.

That is, when the NC device outputs a control signal in response to the step command pulse and the count of the output device 18 is advanced from i to (i+1), the composite magnetic field changes from Hi to day (i+1), and the rotor 2 It is forced to rotate according to the . In such a case, exciting currents flow in both forward and reverse directions in the exciting coils 3, 3' and 4, 4', but regardless of the direction of these exciting currents, the direction of the current passing through the resistors 15 and 16 is always constant. This is the result.

The terminal voltages of the resistors 15 and 16 are passed through smoothing circuits 27 and 26, respectively, to comparison circuits 28 and 29, respectively.
is fed back to the other one of the input terminals. The operations of the comparison circuits 28 and 29 are as described above.

Therefore, the switching elements 13 and 14 are now connected to the oscillator 3.
If it is turned on and off by a high frequency signal of 0, the excitation current from the power supply 33 is inputted to the excitation coils 3, 3' and 4, 4' as a current that turns on and off at the high frequency, and is input to the comparison circuits 28 and 29. Selected generator circuit 2
It is supplied as a high frequency pulse or pulsating current having an amplitude corresponding to a reference voltage level of 1.

The excitation currents of the excitation coils 3, 3' and 4, 4' increase at a slew rate determined by the amplitude and frequency of each coil and various constants of the excitation circuit due to the above-mentioned high frequency pulse or pulsating current exposure. The voltage at terminals 16 and 16 also increases.

The voltages between the respective terminals of the insertion resistors 15 and 16 are smoothed by smoothing circuits 26 and 27, respectively, and the respective smoothed voltages are inputted from the IC switch selection circuits 22 and 23 to the other input terminals of the comparison circuits 28 and 29. is compared with the reference voltage that is
When the smoothed voltage becomes the same as the reference voltage, when the switching elements 13 and 14 are turned off, the insertion resistors 15 and 16
Since the terminal voltage of becomes zero, the switching elements 13 and 14 are turned on by the high frequency pulse of the oscillator 30 as described above.
The stepping motor 1 is turned off and the above-described operation is repeated until the next command signal is output from the numerical control 17, and the rotation of the stepping motor 1 is stopped.

In the above case, the times and periods at which the outputs of the comparison circuits 28 and 29 become zero are not particularly synchronized with each other, but the switching elements 13 and 14 are turned on and off by the detection signals of the insertion resistors 15 and 16. The on/off frequency of
As described above, by setting the self-starting frequency higher than the self-starting frequency of the stepping motor 1, even if an asynchronous state occurs, the next operation command signal will not be output from the numerical control device 17, and the signal conversion circuit 18 will not output the next operation command signal. The stepping motor will not rotate as long as the binary code does not change such as stepping.

Thus, when the numerical control device 17 generates at least one pulse and the binary code of the signal conversion circuit 18 is changed or stepped, the excitation coils 3, 3' and 4, 4'
The excitation current is switched to suit the new step, and the stepping motor 1 is driven in the same manner thereafter.

The control circuits mentioned above are all high-frequency circuits, and therefore have extremely good frequency response characteristics.
According to this, the excitation currents of the excitation coils 3, 3' and 4, 4' can be controlled extremely accurately and reliably. Therefore, according to the present invention, the advance angle of the rotor, the escape torque at a constant speed, the retracting torque, and other characteristics are improved, and there is no malfunction even when the torque or speed fluctuates. This can improve the stability and reliability of the system. Note that the configuration of the present invention is not limited to the above-mentioned embodiments.

Here are some examples:

First, instead of the output circuit 18 that outputs a binary code signal, any encoder that can convert the phase angle of the rotor into a binary code can be used, examples of which include a ring counter, a shift counter, etc. The counters, selection circuits, etc. will be blown away. Further, other decoders and other selection circuits can be used for the IC switch, and selection circuits, bi-stabil elements, arithmetic circuits, shift registers, etc. can be used as the components of the excitation direction control circuit. As a control circuit for the switching elements 13 and 14,
In order to perform higher-order control, various combinations of more advanced arithmetic circuits, logic circuits, etc. may be used.

These control circuits are used to more rationally open and close the switching elements 13 and 14 when the output states of the two comparison circuits 28 and 29 match and do not match. In addition, an insertion resistor 15 or 16,
The smoothing circuit 27 or 26 may be formed integrally with the smoothing circuit 27 or 26, or a known voltage detector or the like may be used instead.

The present invention also applies to various types of stepping motors such as permanent magnet type, variable reluctance type with different polarity or angular displacement, and hybrid type, as well as one-phase, two-phase, and three-phase stepping motors in various types of stepping motors. phase, 2~3 phase, or double 1~
It can also be applied to various excitation methods such as two-phase. Since the present invention is constructed as described above, it is possible to provide a drive circuit that is extremely compact and can drive a stepping motor accurately and reliably.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of a stepping motor drive circuit according to the present invention. 1... Stepping motor, 2... Rotor, 3, 3',
4, 4'... Excitation coil, 5 to 12...
... Switching elements constituting a switch circuit network for switching the excitation direction, 13, 14 ... Switching elements for controlling excitation current, 15, 16 ... Resistor, 1
7... Numerical control device, 18... Signal conversion circuit, 19, 20... Isolator, 21.
...Reference voltage generation circuit, 22, 23...IC
Switch, 24, 25... Excitation direction control circuit, 26
, 27... Smoothing circuit, 28, 29...
Comparison circuit, 30...High frequency pulse oscillator, 31,3
2... operational amplifier (gate circuit), 33...
···power supply.

Claims (1)

[Claims] 1 A driving circuit for a stepping motor having a rotor and a plurality of excitation circuits in which coils arranged in a dispersion-like manner around the rotor and connected in series, each of the excitation circuits and a DC power source for driving. A switch circuit network is connected between each of the excitation circuits and can switch the direction of the current flowing through the excitation circuit in both forward and reverse directions, and a switch circuit network is inserted in series in each excitation circuit to control the current flowing to each excitation coil via the switch circuit network. a current control switch, a control circuit that sequentially and sequentially switches each switch of the switch network in response to a pulse signal output from an appropriate drive control circuit, and a reference voltage generation circuit that can output voltage signals of multiple stages. , a selection circuit provided for each excitation circuit and sequentially selecting and outputting the output of the reference voltage output circuit in response to the pulse signal output from the drive control device; and a selection circuit inserted in series for each excitation circuit. a smoothing circuit provided for each resistor to smooth the terminal voltage of each resistor,
Excitation current that oscillates a command signal to open the current control switch of the corresponding excitation circuit only when the output of each of the smoothing circuits and the output of the selection circuit given in response are compared, and the former is less than or equal to the latter. In the control circuit, the excitation current control circuit includes an oscillator that oscillates a high-frequency pulse used as an opening/closing control signal for the current control switch, and an output of each of the smoothing circuits and the selection circuit provided in response thereto. a comparator circuit that compares the output of the oscillator with the output of the high-frequency pulse oscillator and generates a specific signal when the former is less than or equal to the latter; The above-mentioned stepping motor drive circuit comprises a gate circuit that supplies a control signal to a switch.