JPH0698597A - Driving apparatus for stepping motor - Google Patents

Abstract

PURPOSE:To enable controlling torque pulsation when changing an excited phase coil from one to another, uncoupled magnetically with each other, using a level switching means and ratio switching signal generating means, by varying current control reference signals to comparators, respectively. CONSTITUTION:A level switching means 30 and ratio switching signal generating means 15 are provided. To change excitation from one phase coil (phase A) to another (phase B), uncoupled magnetically with each other, current control reference signals Vref. ac and Vref. bd to comparators 12 and 14 are stepwise varied. For the purpose, the current (Ima) to the one phase coil is stepwise reduced, and further, the current (Imb) to the other phase coil is stepwise and synchronously increased, and the ratio of currents fed to the phase coils is thereby varied. This reduces the pulsation of torque generated and enables low-vibration, low-noise operation without need for changing the switching timing of phase switching signals, in other words, without need for changing the step angle, in a one or two phase excitation system, for example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor drive device having a plurality of magnetically coupled phase coils.

[0002]

2. Description of the Related Art FIG. 4 shows a driving device for a four-phase stepping motor. In the figure, the stepping motor 10 has a plurality of (pair) magnetically coupled phase coils A phase and C phase and phase coils B phase and D phase, and the step angle by the two-phase excitation method drive is 7. It is 5 degrees.

The driver 11 (13) turns on the drive power source.
A switching element for N-OFF control, a phase switching element serially connected to each phase coil, and the like are included, and a phase switching signal generated from the control circuit 15 causes phase coils A phase and C phase (B phase).
Phase and D phase) are switched and excited by a predetermined procedure. Further, the comparator 12 connected to the driver 11 has the phase coil A
Phase coil current equivalent signal Vac detected from current Imac flowing in phase (C phase) via current limiting resistor R3 and current control reference signal Vref. And the constant current control signal Viac
Is output to the driver 11. This current control reference signal V
ref. Is the dividing resistance R from the control signal CNT.
1 and R2. The comparator 14 connected to the driver 13 is similarly formed.

In such a driving device, the stepping motor 1
When 0 is driven by the 1-2 phase excitation method drive, the control circuit 15 generates a phase switching signal (A phase signal to D phase signal) in the procedure shown in FIG.
T may be continuously output at a predetermined level as shown in FIG. Then, each phase coil current (A phase current to D phase current)
Is a constant current as shown in FIG. Timing a is one-phase excitation in which only the A-phase coil is excited, timing b is 1-2 phase excitation in which the A-phase coil and B-phase coil are simultaneously excited, and timing c is one-phase excitation in which only the B-phase coil is excited. Excitation.

FIG. 6 shows the relationship between the step angle and the generated torque at the timings a to c. When the timing is changed from the timing a to the timing b, the rotor has a half angle (3.75 degrees) of the step angle (7.5 degrees) ...
It is labeled as 5 degrees. ) Only rotate. Similarly, when switching from the timing b to the timing c, it is rotated by 3.75 degrees.

However, the generated torque diagram Ra has a rectangular shape, whereas the ideal torque diagram Rt has a circular shape.
Therefore, the 4-phase stepping motor 10 is
Compared with the case of driving by the phase excitation method, the step angle can be made smaller, but the driving principle of the stepping motor 10 cannot further reduce the torque fluctuation. Further, such torque fluctuations cause vibration and noise. The lower the speed, the greater the impact. Thus, in consideration of the purpose of use and the like, the conventional drive device is driven by the 1-2 phase excitation method, which is convenient for low-speed operation with a smaller torque fluctuation or a step angle of 1/2, and the step angle (7). ．
Although it is large (5 degrees), it can be switched between the two-phase excitation type drive which can be driven at high speed.

[0007]

However, when it is used for sheet feeding of a thermal printer, for example, further small torque fluctuation, low vibration / low noise, and improvement of feeding accuracy are required. On the other hand, it is difficult to use a multi-phase stepping motor such as a 3-4 phase excitation type motor and its driving device because of the cost.

An object of the present invention is to provide a driving device for a stepping motor which can carry out smooth driving with a small torque fluctuation while keeping the step angle unchanged.

[0009]

A drive device for a stepping motor according to the present invention comprises a plurality of drivers having a plurality of magnetically coupled phase coils for sequentially switching the phase coils for excitation and driving, and a current control reference signal. And a plurality of comparators that output a constant current control signal to each driver by comparing each phase coil current equivalent signal, and a stepping motor drive device that includes a control circuit that generates a phase switching signal to be added to each driver, In the case of providing a level switching means capable of switching the level of each current control reference signal input to each of the comparators in a plurality of stages, and performing excitation switching from one phase coil not magnetically coupled to the other phase coil The phase coil current of the one-phase coil is gradually reduced and the phase coil current of the other-phase coil is synchronously increased. Characterized in that a ratio switching signal generating means for generating a ratio switching signal to the level switching operation at a predetermined procedure on the level switching means to change the current value ratio of both phases coil current while.

[0010]

In the present invention having the above-described structure, for example, when a four-phase stepping motor having a two-phase excitation method and a step angle of 7.5 degrees is operated by the one-two-phase excitation method, a one-phase coil (for example, A When the excitation is switched from the phase coil) to the other phase coil (B phase coil), the step angle is 3.75. According to the present invention, the level switching signal from the ratio switching signal generating means causes the level switching means to perform a level switching operation in a predetermined procedure, for example, the level of each current control reference signal input to the comparator is switched to four levels. Then, the phase coil current of the one-phase coil is decreased in four steps and the phase coil current of the other-phase coil is increased in the same four steps and synchronously. Therefore, it is possible to change the ratio of the values of the currents flowing through the two-phase coils, and it is possible to greatly reduce the torque fluctuation while keeping the step angle unchanged.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the present drive device has the same basic structure as that of the conventional example (FIG. 4) and is provided with a level switching means 30 and a ratio switching signal generating means (15) so that the torque fluctuation can be performed without changing the step angle. It is configured so that it can be made smaller.

Therefore, the same or common parts as those of the conventional example are designated by the same reference numerals, and the description thereof will be simplified or omitted. However, only the current limiting resistor has the sign R
Changed from 3, R4 to R7, R8.

First, the level switching means 30 outputs the current limiting reference signal Vref.Vref to the comparator 12 connected as shown in FIG. ac for switching the signal level of a plurality of (4) stages, and the current control reference signal Vref. It is formed of a resistor circuit including resistors R4 to R6 for switching the signal level of bd into a plurality of (4) steps.

The ratio switching signal generating means (15) is a means for generating ratio switching signals CNT1, CNT2 and CNT3 for causing the level switching means 30 to perform a level switching operation in a predetermined procedure. In this embodiment, the phase switching signal [Fig. (A) Phase A ~ D
The control circuit 15 is also used in order to synchronize the phase.

The ratio switching signals CNT1 to CNT3 are
When the excitation switching is performed from the one-phase coil (for example, A-phase) which is not magnetically coupled to the stepping motor 10 to the other-phase coil (B-phase), the coil current Imac of the one-phase coil
And the phase coil current I of the other phase coil
The resistance circuit (30) is output at such a timing that the resistance circuit (30) is changed so as to change the current value ratio of the two-phase coil currents (Ima, Imb) while increasing the mbd synchronously in stages.

More specifically, when each phase switching signal is turned on and off at 7: 9 from the control circuit 15 as shown in FIG. 2 (A), each ratio switching signal CNT1 to CNT3 is shown in (B). Outputs ON-OFF at the timing. CN
T3 is set to L level when both CNT1 and CNT2 are at H level. Then, the comparators 12 and 14
To each current control reference signal Vref. ac, Vref. b
Since d is changed in a stepwise manner, as shown in (C) and the timings shown in FIG.
a decreases from 1A to 0A in four steps, and the B-phase coil current Imb is synchronized with 0A to 1A in the same four steps and increased.

That is, the resistance values R1 to R3 and R4 to R6 of the level switching means 30 are set to the phase coil currents Ima and Im.
If b is set in advance so that the current value has the ratio shown in FIG. 3, the generated torque diagram Rc can be brought closer to the ideal generated torque diagram Rt and the torque fluctuation can be reduced. If it is larger than four steps, the torque fluctuation can be further suppressed. Timing →, →, →,
When switching to →, the rotor apparently has a step angle of the 1-2 phase excitation method of 3.75 [= (1/2) × (7.5)].
1/2 angle [= (1/4) × (7.5) ... In FIG. 3, 22.5 degrees is shown for the sake of convenience].
In relation to the phase switching signal (A phase, B phase) in FIG. 2A, the step is substantially stepped by 3.75 degrees.

It should be noted that each ratio switching signal CNT1, CNT
If both 2 and CNT3 are continuously set to the H level similarly to the conventional control signal CNT shown in FIG. 5B, the normal 1-2 phase excitation system drive shown in FIG. 6 is switched.

According to this embodiment, however, the level switching means 30 and the ratio switching signal generating means (15) are provided,
When switching the excitation from the one-phase coil (A phase) not magnetically coupled to the other-phase coil (B phase), each current control reference signal Vref. ac,
Vref. By gradually changing bd, the one-phase coil current (Ima) is gradually reduced and the other-phase coil current (Imb) is similarly increased in stepwise synchronization while the current value flowing in the phase coil is increased. Since the ratio is changed, for example, the switching timing of the phase switching signal of the 1-2 phase excitation method is not changed, that is, the step angle can be left as it is and the fluctuation of the generated torque can be made extremely small, and the low vibration and low vibration can be achieved. Can perform noise driving.

Further, since the level switching means 30 is formed of resistance circuits (R1 to R6), the current control reference signal Vref. ac, V
ref. The ratio of bd, that is, the phase coil current (Ima, I
The current value ratio of mb) can be easily adjusted and can be realized at low cost.

Further, the ratio switching signal generating means is the control circuit 1.
5 is also used and each ratio switching signal CNT1 to CNT
Since NT3 is generated in perfect synchronization with each phase switching signal, the stepping motor 10 can be driven to rotate more smoothly, and torque fluctuations can be further reduced by increasing the number of ratio switching signals (CNT) and the number of resistors. it can.

[0022]

According to the present invention, level switching means and ratio switching signal generating means are provided to control each current to each comparator when switching the excitation from one phase coil which is not magnetically coupled to the other phase coil. By changing the reference signal stepwise, the one-phase coil current is gradually decreased and the other-phase coil current is similarly increased stepwise and synchronously, while changing the current value ratio flowing in the phase coil. Because of the configuration, for example, the fluctuation of the generated torque can be made extremely small without changing the switching timing of the phase switching signal of the 1-2 phase excitation method, that is, the step angle can be left as it is, and the operation with low vibration and low noise can be performed. Can be done.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is also a timing chart for explaining the operation.

FIG. 3 is also a diagram for explaining the relationship between a change in current value ratio and a generated torque diagram.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is also a timing chart for explaining the operation.

FIG. 6 is also a diagram for explaining a generated torque diagram by the 1-2 phase excitation system drive.

[Explanation of symbols]

 10 stepping motor 11, 13 driver 12, 14 comparator 15 control circuit (ratio switching signal generating means) 30 level switching means CNT1 to CNT3 ratio switching signal Vref. ac, Vref. bd current control reference signal Viac, Vibd constant current control signal Imac, Imbd phase coil current

Claims (1)

[Claims] 1. A plurality of drivers having a plurality of magnetically coupled phase coils and sequentially switching the phase coils to drive the excitation, and a current control reference signal and each phase coil current equivalent signal are compared to each driver. In a stepping motor drive device having a plurality of comparators that output constant current control signals and a control circuit that generates a phase switching signal to be applied to each driver, the levels of the respective current control reference signals input to the respective comparators are respectively set. Is provided with a level switching means that is switchable in a plurality of stages, and reduces the phase coil current of the one-phase coil stepwise when switching the excitation from the one-phase coil that is not magnetically coupled to the other-phase coil, and While increasing the phase coil current of the other phase coil stepwise in synchronization, the level value of the two phase coil currents is changed so as to be changed. Drive of the stepping motor, characterized in that a ratio switching signal generating means for generating a ratio switching signal to the level switching operation at a predetermined procedure switching means.