JPS582559B2 - Pulse motor drive method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive system for a pulse motor, and more particularly to a drive system for a step motor that has been improved to equalize torque characteristics during startup and during continuous rotation.

Conventionally, in order to make the rotation of the step motor smooth, the step motor is driven by sequentially exciting three sets of coils of the step motor while alternately excitation of only one set of coils and simultaneous excitation of two sets of coils. The method has been widely adopted.

For example, this drive system is explained in detail in Japanese Patent Publication No. 37-7016.

It is also known to make the generated torque even more smooth by making the current when exciting one set of coils substantially equal to the sum of currents when simultaneously exciting two sets of coils.

1 to 4 are diagrams for explaining such a conventional drive system. FIG. 1 shows an example of the configuration of a circuit for exciting one set of coils, and FIG. The input signal applied to the drive circuit shown in the figure and the energizing current (excitation current) of the coil are shown in Figure 3. When four sets of coils are used,
Figure 4 shows the excitation current near the time of startup when switching from 1-phase excitation to 2-phase excitation, and Figure 4 shows the same excitation current as in Figure 3, but when switching from 2-phase excitation to 1-phase excitation. This shows what happens when you start up.

In Figure 1, EH and EL are high and low output voltages (2
4V, 5V), QH and QL are switching transistors, tH and tL are each transistor Q
H, QL base input terminals, D1 is a backflow prevention transistor, D2 is a flyback diode, D3 is an oscillation prevention diode, and C is a coil to be excited.

Two transistors QH in series with the coil C,
QL is connected to the series circuit to a high voltage source;
Further, a low voltage source EL is connected to the series circuit of the coil C and one transistor QL via a backflow prevention diode D1.

Therefore, when a positive signal is applied only to the base input terminal tL of the transistor QL, current is supplied from the low voltage source to the coil C, and a positive signal and a negative signal are simultaneously applied to both the transistor QL and the transistor QH. is applied, a current is supplied from the high voltage source to the coil C.

That is, as shown in FIG. 2, a positive signal L is applied to the base input terminal tL of the transistor QL, and a negative signal H is applied to the base input terminal tH of the transistor QL. The voltage line EL applies voltage to the coil C, and the current 2 gradually increases at a relatively large rate of increase.

Further, in TII and TIII, voltage is applied to the coil C only from the low power source EL, so the current I gradually decreases and reaches a nearly steady value determined by the internal resistance of the coil, speed back electromotive force, etc.

Note that the above excitation periods TI, TII, and TIII are a first period in which two-phase excitation is performed together with other coils in the preceding excitation order, a second period in which one-phase excitation is performed, and a second period in which the excitation order is delayed. This corresponds to the third period in which two-phase excitation is performed together with other sets of coils.

In the case of a four-phase step motor that excites four sets of coils, the excitation currents φ1, φ2, φ3, φ4 of each set are exactly equal to one period by 4, as shown in Figures 3 and 4. It will be in a state where the time is shifted evenly, and then the above 1.
Periods during which phase excitation and two-phase excitation are performed alternately appear every period obtained by dividing one period into eight equal parts.

For example, if the period in which 1-phase excitation and 2-phase excitation are performed is taken as a unit, and the excitation start period of current φ1 flowing through a suitable set of coils is used as the base point, one cycle is the period T1 to T1 as shown in the figure.
8, the first phase exciting current φ1 flows during the period T1 to T3, and similarly the second phase exciting current door 2 flows during the period T3 to T5.
During this period, the third phase excitation current z4 flows during the period T7 to T1.

Now, it is considered that the torque generated by each of the excitation currents φ1 to φ4 is roughly proportional to the sum of the excitation currents of each period T1 to T8.

Then, in the case shown in FIG. 3, one phase excitation period T2,
At T4, T6, and T8, a large excitation current flows through one set of coils, and during two-phase excitation periods T1, T3, T5, and T7, a relatively small excitation current flows through two sets of coils, so the generated torque is approximately equal for both. It can be said that there is little variation.

However, as shown in FIG. 4, when the step motor is stopped in a two-phase excitation state and then started from that state, the two sets of coils at the time of stop shown in period T1 have an equal magnitude of current. Both are connected to a low voltage source because of the need to flow, and one current φ4 is cut off at T2 at startup, leaving the other current φ1, but this current φ1 is connected to a high voltage source in the period before that. Since the current is not supplied, the current is significantly smaller than the current during one-phase excitation or two-phase excitation during continuous rotation.

In other words, when starting while switching from 1-phase excitation to 2-phase excitation as shown in Fig. 3, and when starting while switching from 2-phase excitation to 1-phase excitation as shown in Fig. 4, the starting torque is large. have different drawbacks.

Therefore, it is an object of the present invention to eliminate these drawbacks and provide a step motor drive method that does not have variations in torque characteristics at startup. A pulse motor that can switch the number of phases and reduce the voltage that has started to be supplied at the start of excitation of each phase when switching the next number of phases, but can make the average current of the phase larger than at the start of excitation due to the induction action of the excitation coil. In the drive method, if there is no phase in which excitation starts at the same time as the supply of the drive pulse starts, at least
The time difference between the first drive pulse and the second drive pulse is 2
This is achieved by making the time difference sufficiently short compared to the time difference between the third drive pulse and the third drive pulse, and one embodiment thereof will be described in detail below with reference to the drawings.

FIG. 5 is a diagram for explaining the operating principle of one drive method of the pulse motor according to the present invention.

In FIG. 5, (PLS) is a drive pulse, (L1) is a signal that controls the first phase low voltage side power supply, (L1) is a signal that also controls the second phase low voltage side power supply, and (H2)
is a signal for controlling the second phase high voltage side power supply, (φ1) is the first phase excitation current, and (φ2) is the second phase excitation current.

The characteristic operation based on the present invention is that when starting by switching from two-phase excitation to one-phase excitation, the drive pulse groups PLS1, PLS2, PLS3, etc. shown in the same figure (PLS)
Among them, the time t2 from the first drive pulse PLS1 to the second drive pulse PLS2 is shortened, and the time t3 to t2 from the second drive pulse PLS2 to the third 1 drive pulse is lengthened.

That is, while the conventional second single drive pulse PLS2' occurs at the timing shown by the broken line, the present invention generates the second drive pulse PLS2 earlier.

Therefore, the operation of the first phase remains unchanged from the conventional one, but the operation of the second phase
The phase behavior will be different.

That is, as shown by the solid lines (L2) and (H2) in the figure, the excitation start timing of the second phase is advanced compared to the case of the broken line, and at the same time, the entire excitation period is extended.

As a result, the second phase excitation current (φ2) is equal to the drive pulse PL
It becomes a large value immediately near S1, and a large torque is generated.

In other words, conventionally, during the period from t2 to t2', only the first phase exciting current (φ1) was responsible for generating torque, but according to the present invention, during the same period, the first phase and Since both the second phase excitation currents (φ1) and (φ2) generate torque, the initial torque is large and the speed can be increased in a short time.

Furthermore, when the pulse motor is started by switching from one-phase excitation to two-phase excitation, conventionally the second-phase excitation is started at the same time as the start-up, and the high-voltage side power is supplied for a predetermined period of time. The present invention can also be configured in the same way, but if necessary, the second drive pulse PLS2 may be generated earlier, and in that case, the supply of the high-voltage side power is also interrupted midway. Unless you do something like this, there will be no reduction in torque.

Further, in order to sequentially increase the speed of the pulse motor immediately after startup, the intervals between the third and subsequent drive pulses are sequentially shortened.

The following circuit is suitable for generating such drive pulses.

That is, FIG. 6 is a diagram showing an example of the configuration of a circuit that obtains a drive pulse based on the present invention from a conventional drive pulse and drives a pulse motor, and FIG. 7 is an explanatory diagram of its operation.

In Fig. 6, F/F is a startup detection flip-flop, AND is an AND gate, MMI, MMII, MMII
I are the first, second and third timer circuits, OR is the OR gate, ■NH is the inhibit circuit, 6 is the excitation phase switching circuit, DET is the two-phase excitation detection circuit, 41, 42, 43, 44
is the excitation coil drive circuit for each phase.

First, the drive detection flip-flop F/F is shown in FIG.
As shown in (NIT), it is set by the rise of the activation signal INIT before the arrival of the first drive pulse PLS1.

Therefore, when a drive pulse comes thereafter, the AND gate AND is opened or closed depending on the output of the two-phase excitation detection circuit DET.

For example, when 2-phase excitation is in progress, the output of the 2-phase excitation detection circuit DET becomes "1", and therefore, as shown in FIG.
As shown in
1 can pass.

As soon as the drive pulse PLS1 passes through the AND gate AND, the activation detection flip-flop F/F is reset as shown in the figure (F/F), and from now on, the activation signal I
It is not set until NIT rises again.

Therefore, the AND gate AND is the first drive pulse PLS
Only 1 will be allowed to pass.

Next, when the drive pulse that has passed through the AND gate AND is input to the first timer circuit MMI, the timer circuit outputs the second drive pulse based on the present invention after time t2 as shown in FIG. 7 (PLS2). Generates drive pulses.

The first drive pulse PLS1 generated in this way and the second drive pulse PLS1
The driving pulse PLS2 is applied to the excitation phase switching circuit 6 via the OR gate OR and the inhibit circuit INH.

On the other hand, the second drive pulse PLS2 is applied to the second timer circuit MM.
As shown in FIG. 7 (GATE), the gate signal from the second timer circuit MMII is triggered at time t0.
It becomes “0” only during the period, so the inhibit circuit INH
does not pass the output of the OR gate during this period.

That is, even if the conventional second one drive pulse PLS' is applied from the OR gate OR, it is not applied to the excitation phase switching circuit.

, and after this period of prohibition has passed, the first
, the second time circuit MMI, MMII no longer operates,
Therefore, the third and subsequent drive pulses PLS3, PLS4...
. . . are applied to the excitation phase switching circuit 6 in the same way as in the conventional case.

That is, the output of the inhibit circuit INH is as shown in FIG.
As shown in NH), the conventional drive pulse train PLS1, P
This corresponds to the result obtained by removing the second drive pulse from LS2, PLS3, PLS4, . . . and adding another drive pulse PLS2 whose timing has been advanced.

Now, the removal and addition of this drive pulse is performed when the AND gate AND passes the first drive pulse as described above, and when starting from one-phase excitation, there is no difference between the drive pulse and the conventional drive pulse. It becomes unchanging.

However, there is no problem even if the two-phase excitation detection circuit DET is not provided and the second drive pulse is always removed and added.

That is, as shown in FIG.
1, 42, 43, and 44, a third timer circuit M is configured to keep the voltage supply duration from the high voltage side power source 4 constant.
This is because if MIII is provided and the voltage supply from the power source EH is continued even after the two-phase excitation period (0 to t2) ends, there will be no reduction in the driving torque that would cause a problem.

As described above, according to the present invention, by controlling the timing of one drive pulse at startup, it is possible to generate a sufficiently large torque even if the phase excitation states of the startup temples are different, and the speed of the startup temple is It is possible to increase the rise of the

In the above embodiment, the number of excitation phases is switched between 1 phase and 2 phases, but the present invention is not limited to this, and the number of excitation phases is switched between 2 phases and 3 phases. The present invention can be similarly applied to cases in which the present invention is carried out, and is of course applicable not only to 4-phase pulse motors but also to 3-phase pulse motors and 5-phase or more pulse motors.

Furthermore, in addition to the circuit configuration shown in FIG. 6, if the circuit can temporally soften one predetermined drive pulse,
Can be used similarly.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams for explaining the conventional drive system, Figures 5 to 7 are diagrams for explaining the embodiment of the present invention, and Figure 5 shows the excitation operation of each coil. FIG. 6 is a diagram showing a configuration example of a coil drive circuit, and FIG. 7 is a diagram illustrating signals of each part of the circuit shown in FIG. 6. EH...High voltage side power supply, EL...Low voltage side power supply, QH,
QL...Switching transistor, D1, D2,
D3...Diode, C...Coil, MMI, MM
IT, MMIII...timer circuit, OR...or gate, AND...and gate, ■NH...in bit circuit, DET...two-phase excitation detection circuit, 6...excitation phase switching circuit, F/F...Start detection flip-flop.

Claims (1)

[Claims] 1. A continuous driving pulse that alternately includes a starting pulse and an ending pulse, and the starting pulse sequentially starts excitation of adjacent phases of the pulse motor, and the ending pulse starts excitation of a plurality of simultaneously excited phases. At the same time as finishing the excitation of the earliest phase among the two, the average current of the excitation coil per predetermined time is set to the excitation coil in response to a decrease in the applied voltage of the excitation coil that occurs after a predetermined time from the start of excitation during the excitation period of each phase. In a pulse motor drive method in which excitation is maintained larger than at the start of excitation due to the induction effect of A pulse motor drive method characterized by making the interval shorter than the immediately following end pulse. 2. The pulse motor drive method according to claim 1, wherein the supply interval of the third and subsequent drive pulses is sequentially shortened.