JPS60102894A - Drive system for pulse motor - Google Patents

Abstract

PURPOSE:To suppress the production of a vibration due to the power source voltage or the variation in a load by feeding back the speed amount of a pulse motor to a phase exciting current. CONSTITUTION:A coil 1A is driven by a constant current in a switching type when a constant current drive switching transistor 14A is turned ON. When the transistor 14A is turned OFF, the current is fed back to a circuit which includes a commutation transistor 23A while attenuating by the energy in the coil 1A in a flywheel action. The peak values of the waveforms of the exciting currents are held at the prescribed value on the basis of the reference voltage Vr. However, the bottom value is different depending upon the energy amount stored in the coil 1A or counterelectromotive force, and generally relates to the rotating speed of a pulse motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pulse motor drive method suitable for controlling a printer, and in particular to a method in which one operation of a pulse motor is performed using a plurality of consecutive pulses. The present invention relates to a phase excitation current drive method that is less affected by power supply voltage fluctuations and is capable of stable stop control.

[Technology background]

When performing one operation of a pulse motor in several steps.

To stop smoothly without causing vibration.

Conventionally, various damper circuits such as a negative phase control circuit and a DLSED circuit have been used. Furthermore, in order to perform high-speed and highly accurate positioning in one operation, a linear acceleration/deceleration control method in which an acceleration period and a deceleration period are continued as shown in Fig. A.1 is widely used.

In general serial printers, the pulse motor drive circuit that selectively controls the rotational position of the type wheel uses the technology described above to operate at high speed and with high stability.However, during operation, power supply voltage fluctuations and Easily affected by load fluctuations1
As shown in Figure 2.

A vibration component appeared in the linear acceleration/deceleration characteristics, making it difficult to stop the vehicle stably.

[Conventional technology and problems]

In conventional pulse motor drive circuits, starting characteristics and

In order to improve the high frequency region of continuous operation characteristics, switching type constant current drive control is performed for each phase excitation current.

In other words, a pulse motor has a reverse effect on the coils of each phase due to the influence of the time constant of the coils of each phase, and because the rotor is composed of magnets and the stator is composed of coils, it functions as a power generator when the motor rotates. Electromotive force is generated. This is because the direction of this back electromotive force acts in the opposite direction to the applied voltage.

Unless a voltage is supplied to overcome this back electromotive force, high frequency characteristics will not improve. As one means of solving this problem, a constant current drive circuit is used in which a high voltage is applied to the pulse motor to overcome this back electromotive force, thereby adjusting the operating characteristics up to a high frequency range.

Diagram N13 shows a conventional example of such a constant current drive circuit. In the figure, IA, IB, and IC.

ID is the stator excitation coil of each phase A, B, C, and D of the four-phase pulse motor. Also, 2 is a power supply, and 3 and 4I are main switching transistors.

Current is supplied to coils IA, IC and IB, ID, respectively. 5A, 5B, 5C, and 5D are coil drive transistors, 6 and 7 are current detection resistors, 8 and 9 are comparators with hysteresis, IO and 11 are control transistors, and 12 and 13 are commutating diodes.

To briefly explain the operation, for example, when the coil drive transistor 5A is driven ON by the A-phase polarity pulse applied to the base, the coil IA generates an excitation current in a self-excited switching manner via the main switching transistor 3. is supplied. The magnitude of the excitation current is detected by the voltage generated in the current detection resistor, and compared with the reference voltage Vr by the comparator 8.

When the detection voltage is greater than vr, the comparator 8
The main switching transistor 3 is controlled to be OFF via the control transistor 10. When the transistor 3 is turned off, the current continues to flow through the commutation diode 12 while being attenuated due to the flywheel effect of the energy stored in the coil IA.

Here, the comparison operation level of the comparator 8 has shifted due to its hysteresis characteristic, and for this reason, the coil LA
When the current flowing through the resistor 6 falls to a certain level, it responds again to the detected voltage from the resistor 6.

The main switching transistor 3 is controlled to be ON.

Flow current through coil IA. Thereafter, similar operations are repeated in a self-exciting manner.

Figure gF4 shows the state of the excitation current flowing through the coil IA in this manner. In the figure, eVr1 and (jV
r2 represents two reference levels at which the comparator 8 operates in hysteresis, and rI6 represents a constant average current.

The circuit in Figure 3 consists of coils IA and I for each phase of the pulse motor.
The constant current drive described above is performed for B, IC, and ID, but
This circuit has the disadvantage that its high frequency characteristics are susceptible to fluctuations in the power supply's direct voltage and load.

Even if the design is designed to achieve a stable stop by linear acceleration/deceleration for a given power supply voltage, for example, the high frequency characteristics may change due to fluctuations in the power supply voltage, and the constant current characteristics may cause back electromotive force generated depending on the speed of the pulse motor. Since this acts to cancel out the influence of the speed, there is no feedback on the speed, and as shown in FIG. 2, there is a problem that a stable stop cannot be achieved.

[Object and structure of the invention]

The purpose of the present invention is to solve the above-mentioned problems of the conventional method, and to provide a means for controlling the speed change meter of the pulse motor by feedback, based on constant current drive, and at the same time, to prevent fluctuations in power supply voltage or load. This absorbs the impact and enables stable stopping.

To this end, the configuration of the present invention includes a switching type constant current control circuit connected in series to the phase excitation coil of the pulse motor, and a commutation circuit connected in parallel to the phase excitation coil, and the switching type constant current control circuit connected in parallel to the phase excitation coil. The control circuit is characterized in that it has timing means for setting the non-application period of the switching drive according to voltage conditions.

[Embodiments of the invention]

The details of the present invention will be explained below based on examples.

FIG. 5 is a circuit diagram of one embodiment of the present invention. In the figure, IA
, IB, Ic, and LD are pulse motors A, B, and
These are C and D phase stator excitation coils. Further, 14A to 14D are switching transistors for constant current drive, 15
and 16 are current detection resistors, 17 and 18 are comparators without hysteresis, 19 and 20 are monostable multivibrators, and 21A to 21D are AND gates.

22A to 221) are control transistors, 23A to 2
3D represents a commutation transistor, and 24 represents a power input line.

For convenience of explanation, the A-phase drive portion of the nine circuits will be explained as an example. The other parts perform exactly the same circuit operation.

Note that FIG. 316 is a circuit waveform diagram, and ■, ■, ■, ■ represent signal waveforms of the same display portions in FIG.

The coil IA is driven with a constant current by a switching method by turning on the constant current driving switching transistor 14A. When transistor 14A is OFF, the flywheel effect of the energy in coil LA causes the current to be attenuated and returned to the circuit including commutating transistor 23A. Commutation transistor 23A remains ON while the A-phase clock is applied to control transistor 22A, and enables commutation whenever transistor 14A turns OFF.

First, at point 1 in Figure 6. When the A-phase clock shown in ■ is applied and the transistor 14A is turned on,
As shown in the figure (l), a current flows through the coil IA, and at the time t1 when the detected voltage taken out from the voltage detection resistor 15 becomes equal to the reference voltage Vr, the comparator 17
The coincidence signal shown in FIG.

The monostable multivambrator 19 outputs a signal that remains OFF for a certain period τ shown in FIG. 6(c).

Turn off transistor 14A via AND gate 21A
Make it F. As a result, a commutation occurs from the fill IA through the transistor 23A described in 111i, and as a result, an exciting current as shown in Fig. 6 (■) flows through the coil IA. At time t2 after a certain period τ has passed, the transistor 14A is turned on again and the process returns to the beginning. These operations are repeated while the A-phase clock is not applied.

The peak value of each waveform of the excitation current (2) is maintained at a constant value based on the reference voltage Vr. However, the bottom value varies depending on the amount of energy stored in the coil IA or the back electromotive force, and is generally related to the rotational speed of the pulse motor.

The OFF diagram is an explanatory diagram of this, and as shown in (j, z) of the figure, the faster the speed, the lower the bottom value, and the slower the speed, the higher the bottom value. Also, depending on the distance between the rotor and stator in the pulse motor, the effect of speed will be large (as shown in (b)) when they are close together, and small (as shown in (1) when they are far away).

FIG. 318 shows an example in which such a change in the speed of the pulse motor causes a variation in the average current io of the excitation current.

Therefore, according to this embodiment, as the speed increases, the excitation current decreases, and as the speed decreases, the excitation current increases. As a result, fluctuations in the power supply voltage and load can be fed back to the magnitude of the excitation current so as to suppress speed changes, so that the linear acceleration/deceleration characteristics are stabilized as shown in FIG. 9. By detecting the voltage drop level during the OFF period between constant ItJJ and varying the OFF period according to the level (amplifying this feedback amount), the linear acceleration/deceleration characteristics can be further stabilized.

〔Effect of the invention〕

As described above, according to the present invention, the speed oscillation of the pulse motor can be fed back to the phase excitation current based on constant current drive, so it is possible to suppress the occurrence of vibration due to fluctuations in the power supply voltage or load. , can enable stable stopping.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of control characteristics for linear acceleration/deceleration, Figure A.2 is an explanatory diagram of characteristic changes due to fluctuations in power supply voltage, Figure A.3 is a circuit diagram of an example of a conventional constant current drive circuit, and Figure 4. is its operating characteristic diagram, FIG. 5 is a circuit diagram of one embodiment of the present invention, FIG. 6 is its operating waveform diagram, and FIG. A waveform diagram showing the relationship between the Jul current and Figure 8 is a diagram showing an example of excitation current change.
FIG. 19 is an explanatory diagram of linear acceleration/deceleration control characteristics according to this embodiment. In the figure, IA to ID are stator excitation coils. 14A to 14D are switching transistors for constant current driving, and 15 and 16 are current detection resistors. 17 and 18 are comparators, 19 and 20 are monostable multivibrators, 21A to 21D are AND games), and 23A to 23D are commutating transistors +Vr represents a reference voltage. Patent applicant Fujitsu Limited

Claims (1)

[Claims] A switching type constant current control circuit connected in series to a phase excitation coil of a pulse motor, and a commutation circuit connected in parallel to the phase excitation coil. A pulse motor drive system, characterized in that the switching type constant current control circuit has timing means for setting a non-applying period of switching drive according to voltage conditions.