JPS63154098A - Driver circuit for pulse motor - Google Patents

Abstract

PURPOSE:To use only one unit for keeping currents constant, and to reduce the cost of a part by arranging an exciting coil in series between power supplies. CONSTITUTION:A switch S1 and a switch S3 are closed and an A phase winding and a B phase winding are connected in series to cause currents to flow for AB phase excitation in the two-phase excitation of a pulse motor. Switches S1 and S4 are closed and the A phase winding and a B' phase winding are connected in series to cause currents to flow for AB' phase excitation. Switches S2 and S4 are closed and an A' phase winding and the B' phase winding are connected in series to cause currents to flow for A'B' phase excitation. Switches S2 and S3 are closed and the A' phase winding and B phase winding are connected in series to cause currents to flow for A'B phase excitation.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a pulse motor drive circuit.

(Prior Art) The conventional technology will be explained by taking four-phase bifilar winding as an example.

In the unipolar excitation of the four-phase bifilar winding, as shown in FIG. 2, one switching element 31 to S4 is provided for each phase AI and BLfi, and these are connected in parallel between the power supplies to change the combination of excitation.

This conventional example includes the following problems.

(Problems to be Solved by the Invention) The problems to be solved by the present invention are as follows: - Improvement of angular error.

・Higher efficiency and smaller size of motor drive power supply.

- Easier and more accurate excitation current constant current.

・Easy to add protection circuit.

・High frequency through area.

etc.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and as shown in Fig. 1, two exciting coils A and B are arranged in series between the power sources. It is characterized by

(Example) Hereinafter, in the case of using the present invention, how each item which was a problem in the conventional example was improved or improved will be explained by comparing each item.

First, to explain the problem of angular errors, there are two types of angular errors in a stepping motor: those caused by the motor itself and those caused by the drive circuit.

The main causes of the amount caused by the motor itself are the mechanical precision of the motor parts and assembly, and the non-uniformity of the windings. Further, specific examples of the non-uniformity of the winding include the number of turns, resistance value, winding tool base, etc.

In general pulse motors that do not have closed-loop angle control, it is impossible to eliminate the cause internal to the motor from the outside, so in order to get the maximum potential from the motor,
It is best to match the currents of the four excitation phases.

However, variations in the on-resistance of the switching elements used in the final stage of the drive circuit (for example, the collector saturation voltage of bipolar transistors) are also one of the factors that determine the current value of each winding, and it is important to match the currents of each phase. was almost impossible.

It is thought that the variation in the on-resistance of the switching element used in the final stage of the drive circuit described above is caused by the drive circuit described above.

Therefore, although the actual value of the angle angle of the motor exists, it has not been possible to obtain it.

However, the purpose of matching the phase currents must have been to bring the phase angles B1 to B2 of the two-phase excitation vectors shown in FIG. 3 closer to 90 degrees.

In the driving method of the present invention, even if the combination of excitation phases changes and the phase current changes, the mutual electrical phase angle (1-frV) is always maintained at 90 degrees, as shown in FIG. , it is possible to eliminate angular errors caused by phase-to-phase variations in the drive circuit and motor winding resistance.

Next, we will explain how to make the motor drive power source more efficient and smaller.

Traditionally, single? 1! When driving a motor with a power source, the voltage and current magnitudes that determine the capacity of the power source are rated at the following values.

The voltage is the motor rated voltage E per equivalent, and the current is twice the motor rated current ■ per equivalent.

This can be expressed as follows: Ex21.

In the drive circuit of the present invention, the 'W1 source required to drive the same motor has a voltage of 2E and a current of I.

This can be expressed as 2EXI.

Therefore, the motor drive power source can be made more efficient and smaller.

Third, we will explain how to make constant current easier and more accurate.

One method for improving the dynamic characteristics of a pulse motor is to make the excitation current a constant current. This is done by injecting an excitation current from a W source voltage several times or higher than the motor's rated voltage, which speeds up the start-up and widens the motor's response frequency range.
The purpose is to obtain high torque.

If the motor continues to be excited with a high voltage, the temperature of the coil will rise unnecessarily, so once the current has risen to a certain value, it is necessary to maintain the current around that current value.

Specific methods for this include external excitation and automatic chi! -) There is a bar.

Conventional drive circuits use two constant current units, and it is necessary to adjust the balance between them to prevent torque imbalance between phases and to ensure angular accuracy. The methods of balancing IUA are to adjust the adjustment part or to suppress the occurrence of unbalance by using high-precision parts, but it needs to be explained that no matter which method is chosen, perfect matching is impossible. do not.

In the drive circuit of the present invention, the current flowing through the two windings connected in series is the same, so the constant current unit is one
Therefore, component costs can be reduced, unbalance adjustment is naturally unnecessary, and two excitation currents can be matched.

Fourth, we will explain how to easily add a protection circuit.In the drive circuit of the present invention, as explained in the previous section, only one constant current unit is required, so the protection of the drive element can also be done with one unit.
You can achieve your goals easily and reliably in just a few places.

Finally, the formation of the motor into a through area will be explained below.

Considering the switching of two-phase excitation, in the conventional two-phase excitation method, excitation current is continuously supplied to one phase whose excitation is not switched, and the other phase is switched. was.

The energized phase at this time forms a closed ITU path through the power supply and the switching gate. When the magnetic flux of the rotor magnet rotates and interlinks with the coil of the excited phase, a voltage is induced, but since the circuit is closed, a superimposed alternating current flows. Since the current generated here is generated based on the rotation of the rotor, a torque is generated in a direction that hinders the rotation of the rotor. That is, if one phase is excited when switching phase excitation, a braking effect will occur.

This phenomenon does not pose a problem in medium-speed fabrication where the excitation current rises. However, the induced voltage increases in proportion to the frequency,
Since the braking force generated there also increases, the rise of the current becomes insufficient and the torque decreases, which results in keeping the response frequency low.

This is why, although driving with 1-2 phase excitation is effective in smoothing rotation, the response frequency remains at the two phases of 2-phase excitation, and the shaft rotational speeds are the same.

However, in the drive circuit of the present invention, a closed circuit including the winding and the power source is not formed during excitation switching, and no current due to voltage induced in the winding is caused to flow. As a result, the rise of the excitation current is suppressed by an electric time constant unique to the motor other than that caused by the excitation method, and the response frequency can be expanded until the torque decreases and response becomes impossible.

(Effects of the Invention) By using the pulse motor drive circuit according to the present invention, (1) the phase currents of two-phase excitation can be matched, and the angle error of the motor can be used at the motor performance limit.

■Since the motor drive power supply can be set to a voltage twice the motor rated voltage and the rated current to the current equivalent to one phase, the Ti source can be made more efficient and smaller.

(2) In making the excitation current a constant current, only one unit is required, so costs can be reduced, and there is no need to adjust the unbalance between phases or use high-precision parts.

■It is easy to add a driver protection circuit.

■The through area of the motor can be made higher frequency.

This invention has the following effects and can be said to be a useful invention in the field of work to which the present invention pertains.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining the driving method of the present invention, FIG. 2 is a circuit diagram for explaining unipolar excitation of a conventional four-phase bifilar winding, and FIGS. 3 and 4 are diagrams for improving angle errors.
FIG. 3 is a diagram for explaining the phase of a two-phase excitation vector. In the figure, A, λ, B, n are the coils of each phase, 31 to s
4 is a switching element.

Claims (1)

[Claims] A method for driving a pulse motor, characterized in that in a two-phase excitation drive circuit that drives a two-phase or four-phase pulse motor, two exciting coils are always arranged in series.