JPS6194590A - Control circuit for stepping motor - Google Patents

Abstract

PURPOSE:To improve the damping characteristic and to perform high speed response by increasing or decreasing an exciting current in response to a clock pulse before the final clock pulse. CONSTITUTION:A damping controller 7 has an SR flip-flop 8, and suppresses the coil currents Ia, Ib flowing to exciting coils 2a, 2b to alpha% of a rated current by reducing a reference voltage VR for setting the current of a constant current circuit 5 by a clock pulse Pn-1. This suppression is performed until the final clock pulse Pn is input. Further, the value to be suppressed is set to become the stable position of a rotor corresponding to the final clock pulse at the maximum value of the overshoot of the rotor. Thus, when the pulse Pn is applied, no vibration occurs due to the stop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a control circuit for a stepping motor having high-speed response.

[Background Art 1] Generally, in order to realize high-speed responsiveness of a stepping motor, it is necessary to make the rise characteristic of the coil current steep, and conventionally, a constant current source has been used as a control circuit for a stepping motor.

However, in a control circuit using a constant current source,
There has been a problem in that the back electromotive voltage accompanying the rotational movement of the stepping motor cannot be absorbed, and vibrational movement occurs when the rotor of the stepping motor is stopped. Therefore, as seen in "printing devices that use a stepping motor," it is necessary to stop printing (stop the stepping motor) and then reprint (
A certain margin of re-driving time was set before re-driving the stepping motor. Therefore, even if the stepping motor has high-speed response, there is a problem in that the original function cannot be fully utilized. On the other hand, it is conceivable to use a mechanical damper such as a magnetic damper to prevent vibration when the rotor is stopped, but this poses the problem of sacrificing high-speed response.

[Objective of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a material that has good damping characteristics, can take full advantage of high-speed response, and is inexpensive. An object of the present invention is to provide a versatile stepping motor control circuit.

[Disclosure of the Invention] (Embodiment) FIG. 1 shows an embodiment of the present invention, in which a general control circuit 6 of a stepping motor 1 is formed using a microcomputer and controls rotation to form a clock pulse P. The multi-phase excitation coil 2a of the stepping motor 1 is activated in response to the clock pulse P input from the control circuit 10.
, , 2b, a distribution circuit 3 that generates excitation signals Va and Vb to sequentially excite the coils 2a and 2b, and a switching circuit 4 that receives the excitation signals Va and Vb and switches the direction of the coil currents Ia and Ib flowing through the excitation coils 2a and 2b. , and a constant current control four-way 5 for controlling the coil currents Ia and Ib to a constant value. Damping control circuit 7c according to the present invention, clock pulse P'n immediately before final clock pulse Pn
-, the SR7 lip 7 is set with the set pulse Ps synchronized with the rising edge of the clock pulse Ps, and re-cented with the reset pulse PR synchronized with the rising edge of the final clock pulse Pn.
0 tube 8 and a transistor 9 controlled by the SR7 lip 70 tube 8 output Q, and when the output Q of the SR7 lip 70 tube 8 becomes "H" level and the transistor 9 is turned on, The current setting reference voltage R of the constant current circuit 5 is lowered to suppress the coil currents Ia and Ib flowing through the excitation coils 2a and 2b to 0% of the rated current. Here, a certain period of time from the input of the previous clock pulse Pn-, to the input of the final clock pulse Pn, that is, the time T1 during which the suppressed coil currents @Ia and Ib flow, and the degree of suppression α of the coil currents 1a and Il+. % is the stable body a of the rotor 11 whose maximum value of overshoot of the rotor 1a due to the driving torque corresponding to the previous clock pulse Pn-1 corresponds to the final clock pulse Pn.
S z is set. In the figure, the power supply Vc is for the logic circuit, the power supply Vm is for the drive circuit, and the resistors Ra~
Rc is a voltage dividing resistor for setting the reference voltage.6 In the embodiment, the coil currents Ia and rb at time T are suppressed, but if the load connected to the rotor 1a1 is large or Needless to say, when shortening the time T1, the coil currents Ia, Ib may be increased more than the rated coil current.

Examples will be specifically described below with reference to FIGS. 2 to 4. Now, when current is applied to the excitation coils 2a and 2b of the stepping motor 1 to excite them, the rotor 1a rotates to a predetermined position and is held. This position is designated as So in FIG. 2(a), and when the excitation is then switched, the rotor 1a rotates to the next stop position S and stops. This switching of the excitation state is performed by the distribution circuit 3 to which the clock pulse P shown in tIS2 (b) is input.

By the way, when the excitation state is switched, the a-ri 1a moves from the position S to the position S.
Since the excitation in the stepping motor 1 is switched stepwise, if the drive time is set to the rated time and the coil currents Ia and rb are set to a constant 41F as in the conventional example, the rotor 1a will move as shown in FIG. 2(a). It slowly settles down to position 81 while making damped oscillations centered at position 81. Furthermore, when the clock pulse P is inputted at time t, the exciting coils 2a, 2
b is excited again, the rotor 1a begins to move, and slowly settles on the stable body ra S 2 while making damped oscillations centered on the next stable position S2. Therefore, when such a stepping motor is used to feed a printer's nozzle or move a printing wheel, there is the inconvenience that printing cannot be performed until the vibrations are sufficiently attenuated, and the inconvenience that the vibrations cause @ noise. That's why it happens.

By the way, in the present invention, as shown in FIG. 3 and FIG.
When the previous clock pulse Pn-, is input, the excitation state is switched and the clock pulse Pn-,
SR7 Rinobu 70 is set in synchronization with the rise of
When the output Q of knob 8 becomes "H" level, transistor 9
is turned on, a resistor Re is connected in parallel to the voltage dividing resistor Rh, the reference voltage VR is lowered, and the coil currents Ia and Ib controlled by the constant current control circuit 5 based on the reference voltage 2 become 0.
%. Therefore, the rotor 1a begins to move toward S with the driving torque generated by the coil currents 1a and Ib, and in the process of overshooting beyond the stable position s1, the rotor 1a starts to move toward S, due to the coil currents Ia and Ib smaller than the rated current. It moves toward the stable position S2 corresponding to the final clock pulse Pn while being decelerated by the driving torque.

In this case, in the embodiment, the degree of suppression (0%) of the coil currents 1a and Ib is set so that the maximum point of overshoot of the rotor 1a is at the stable position S2, so the rotor 1a is at the stable position. At time L2 when S2 is reached, the energy is almost 0'' and the speed is 0''.

Therefore, when the final clock pulse Pn is output from the rotation control circuit 10 and the excitation state is switched at time t2 when the rotor 1a reaches the maximum point of overshoot, the SR7 limp 7 nlop 8 is synchronized with this final clock pulse Pn. is reset, its output Q goes to L'' level, the transistor 9 is turned off, and the excitation coils 2a, 2b are turned off.
Rated coil currents Ia and Ib flow through the rotor 1a to hold the rotor 1a and stop it at a stable position ra s z without vibration.

Note that the time t2 at which the final clock pulse Pn is generated is set in the rotation control circuit 10 in consideration of the increase/decrease in the coil currents I&, Ib, and the inertia of the rotor 1a and the load M in contact with the shaft of the rotor 1a.

According to the present invention, the vibration of the rotor 1a is almost eliminated, the time required for damping is shortened, the damping characteristics are improved, and the rotor 1a is moved to a predetermined position in an extremely short time! Since the printer can be stopped after IJ, the access time can be shortened when used with a 70-tip disk, and the printing speed can be increased when used with a Deino wheel printer. Furthermore, even if the loads driven by the stepping motor 1 are different, the coil currents Ia and Ib corresponding to the final clock pulse Pn
This can be easily handled by appropriately setting the increase/decrease of V and the i main time T of the final clock pulse Pn, so a versatile control circuit for the stepping motor 1 can be provided. Furthermore, since the energy applied to the rotor 1a is appropriately controlled and its inertia is used to apply the force, no unreasonable force is applied to the rotor 1a, so vibration and resonance phenomena can be extremely reduced. In addition, compared to a system that detects the position of the rotor 1a and feedback-controls the coil currents 1a and Ib, the number of parts can be significantly reduced, making it possible to reduce costs. .

[Effects of the Invention] As described above, the present invention provides input from the rotation control circuit.As described above, the present invention operates the excitation coils of multiple phases of the stepping motor in response to one clock pulse input from the rotation control circuit. A stepping system consisting of a distribution circuit that sequentially generates excitation (li), a switching circuit that receives the excitation signal and switches the direction of the coil current flowing through the excitation coil, and a constant current control circuit that controls the coil current to a constant value. In the motor control circuit, the coil current flowing through the excitation coil is increased or decreased from the rated current in response to the clock pulse one before the final clock pulse, so that the maximum value of the rotor overshoot corresponds to the final clock pulse. A damping control circuit is provided to maintain the stable position of the rotor, and a final clock pulse is input at the time when the maximum value of the rotor overshoot reaches the stable position of the rotor corresponding to the final clock pulse, and the excitation coil is set to the holding position. It is designed to allow current to flow through the coil, and with a simple configuration, it can achieve good damping characteristics and high-speed response, and has the effect of reducing costs. Even if the load to be driven by the motor differs, it can be easily handled by appropriately setting the increase/decrease of the coil current and the generation timing of the final clock/clock pulse.This has the advantage of providing a versatile stepping motor control circuit. In addition, since the energy applied to the rotor is appropriately controlled and damping is performed taking into account its inertia, no excessive force is applied to the rotor, and vibration and resonance phenomena are extremely reduced. It has the effect of being able to

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, and FIGS. 2 to 4 are explanatory diagrams of the same operation. 1 is a stepping motor, 1a is a-! , 2a. 2b is an excitation coil, 3 is a distribution circuit, 4 is a switching circuit, 5 is a constant current control circuit, 7 is a damping control circuit, 1
0 is a rotation control circuit. Agent Patent Attorney Ishi 1) Ai Shichiji 1 Kamo
I self-On ~, I
\, IC/)Q: Q:
the law of nature . Q-cLcLO〉-1-

Claims (1)

[Claims] (1) A distribution circuit that generates excitation signals that sequentially excite the excitation coils of multiple phases of the stepping motor in response to an appropriate number of clock pulses output from the rotation control circuit, and a distribution circuit that generates excitation signals that sequentially excite the excitation coils of multiple phases of the stepping motor in response to the excitation signals. In a stepping motor control circuit consisting of a switching circuit that switches the direction of the flowing coil current and a constant current control circuit that controls the coil current to a constant value, the excitation coil is activated in response to a clock pulse immediately before the final clock pulse. A damping control circuit is provided that increases or decreases the coil current flowing from the rated current so that the maximum value of the rotor overshoot becomes the stable position of the rotor corresponding to the final clock pulse. A control circuit for a stepping motor, characterized in that a final clock pulse is input at a time when a rotor reaches a stable position corresponding to a clock pulse to cause a holding coil current to flow through an excitation coil.