JPH10136692A - Drive interrupt method of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable driving and interrupt with necessary and minimum consumption power by detecting a sensing signal for switching an excitation phase from induced power generated in a driving coil, and turning the excitation phase to off, when the sensing signal due to the induced power cannot be obtained for a period longer than or equal to a specific value. SOLUTION: A sensing signal corresponding to an operating state is outputted to a detection circuit 4 through a stepping motor drive circuit 2. The detection circuit 4 detects the change-over timing of the drive phase of a stepping motor 3 and outputs the timing to a CPU 1. When a load to the stepping motor 3 rapidly increases, the rotational speed of a rotor decreases, and the drive phase change-over timing of the stepping motor 4 becomes slow. When induced power is not generated for a period longer than or equal to a specific value, the CPU 1 turns the excitation phase to off and makes the rotor automatically stop. As a result, sure operation is enabled with the minimum power corresponding to a load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving stop method for driving and stopping a stepping motor with low power, and is suitable as a driving stop method for a stepping motor for operating a shutoff valve such as a gas meter.

[0002]

2. Description of the Related Art In a conventional stepping motor, the frequency of the stepping motor is changed in response to a change in voltage, the power supply limiting resistance is changed, or the frequency is changed by predicting a load in advance according to the method of use. The power was reduced by changing the power.

However, the characteristics of the stepping motor must take into account unexpected load fluctuation due to dust or foreign matter, load fluctuation due to vibration, load fluctuation due to aging, and the like. For this purpose, in the conventional method, it is necessary to provide a margin for the torque so as to operate even when these situations occur, but this leads to an increase in power consumption.

Also, in order to reliably operate even with respect to variations in the characteristics of individual stepping motors and variations in the load side of a gas meter or the like due to variations in the manufacturing of the stepping motors, etc., the torque must be given a margin. However, this also leads to an increase in power consumption.

On the other hand, as a method of operating the shut-off valve with the minimum required power consumption, a DC motor which can change the speed of the rotor depending on the load or voltage and consequently can operate with the minimum required power consumption can be considered. Since sparks come out of the brush, it is not suitable as a gas shutoff valve.

Conventionally, as a method of stopping the stepping motor, there has been a method of stopping at a predetermined number of pulses or a method of stopping the stepping motor after confirming the position with an external sensor.
However, the former method cannot be used in the shut-off valve because the distance between the valve seat and the valve element varies in manufacturing and assembly. Further, the latter method has a problem that the cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention provides not only voltage fluctuations but also unexpected load fluctuations due to dust and foreign matter.
It is an object of the present invention to enable a stepping motor to be driven and stopped with minimum necessary power consumption even if there are fluctuation factors such as load fluctuation due to vibration and load fluctuation due to aging.

In addition, the stepping motor is driven and stopped with the minimum necessary power consumption even with respect to variations in characteristics of individual stepping motors and variations in the load side of a gas meter or the like due to variations in manufacturing of the stepping motors. It is an object of the present invention to be able to stop automatically without using a sensor or the like.

Further, the stepping motor operates in a manner similar to that of the DC motor, but can be safely driven and stopped without generating a spark.
An object of the present invention is to provide a low-cost shut-off valve operation function.

Another object of the present invention is to make it possible to easily and accurately stop the rotor of a stepping motor after the shut-off valve is securely closed, particularly when applied to a shut-off valve.

[0011]

According to the method of stopping driving of a stepping motor according to the present invention, a sensing signal for switching an excitation phase is detected from an induced power generated in a drive coil, and a sensing signal based on the induced power is obtained for a predetermined time or more. When it runs out, turn off the excitation phase. The sensing signal can be detected, for example, from the induced power generated in the drive coil that is not supplying power.

In order to make the stop operation more reliable, for example,
Immediately before the rotor is stopped, a braking force is applied to the rotor by a spring material interposed between the rotor shaft and the bearing.
When used for a shutoff valve, a braking force is applied after the shutoff valve is closed. In this case, after the valve element of the shut-off valve comes into contact with the valve seat by the thrust due to the rotation of the rotor shaft, the thrust in the opposite direction acts on the rotor shaft and the spring material is compressed by the rotor, so that the braking force is applied to the rotor. Should be added.

[0013]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration for driving a stepping motor according to the present invention. The CPU 1 outputs a drive command to the stepping motor drive circuit 2. The stepping motor drive circuit 2 outputs a drive pulse to the stepping motor 3 according to a command from the CPU 1. Stepping motor 3
Operates according to the drive pulse, and outputs a sensing signal corresponding to the operation state to the detection circuit 4 via the stepping motor drive circuit 2. The detection circuit 4 detects the switching timing of the driving phase of the stepping motor 3 based on the sensing signal, and outputs a switching timing signal to the CPU 1. The CPU 1 outputs a command to the stepping motor drive circuit 2 to switch the driving phase based on the switching timing signal.

As described above, when the operation of the stepping motor 3 is started by a command from the CPU 1, the operation state is sensed, and the driving phase is switched at a timing corresponding to the operation state. Then, this closed loop control is repeated.

Next, sensing of the operating condition will be described. FIG. 2 shows an operation concept of the stepping motor 3.
In the figure, R is a rotor (magnet), S1, S2, S3
S4 is a stator pole, and the stator pole S1 has A phase and A '
A and A 'phases in the stator pole S2 and the stator pole S3
Are wound with B-phase and B'-phase coils, and the stator pole S4 is wound with B-phase and B'-phase coils, and the rotor R rotates stepwise in response to switching of these drive phases. FIG. 3 shows the relationship between the driving phase and the polarity of the stator pole.

Generally, a stepping motor operates at a predetermined drive phase switching timing. According to the present invention, the operation is not performed at a predetermined drive phase timing, but the operation state is sensed to generate the drive phase switching timing.

For sensing, a phase not used for driving in driving phase switching is used as a sensing coil. Therefore, the sensing coil is also sequentially switched. An induced voltage is generated in the sensing coil by the movement of the rotor R.

FIG. 4 illustrates the principle of generating an induced voltage by the movement of the rotor R. For simplicity, the induced voltage when the rotor R rotates at a substantially constant speed is shown for each phase.

2, 3, and 4, as a method of driving the stepping motor, the timing at which the phase is switched from the A phase to the B phase is such that the N pole of the rotor R in FIG.
It is good to take around That is, as shown in FIG. 4, it is sufficient that the timing is substantially the same as the timing at which the induced voltage of the phase B in which the drive current does not flow changes from positive to negative. And
Similarly, the timing of switching from the B phase to the A phase may be substantially the same as the timing at which the induced voltage changes from positive to negative. By repeating this, the rotor R can continue to rotate.

As another method of driving the stepping motor, the timing of switching from the A-phase to the B-phase may be made substantially coincident with the timing at which the induced voltage of the B'-phase where no drive current flows changes from negative to positive.

Although the level of the induced voltage is expressed as positive or negative, the positive induced voltage functions to cause a current to flow in a direction opposite to the current at the time of driving. In an actual circuit, the reference potential may be a power supply voltage, GND, or another set value.

Further, the point in time when the set value is reached can be used as the phase switching timing itself, or the point in time delayed from the point in time when the set value is reached can be used as the phase switching timing. This selection may be determined by experiments or the like depending on the characteristics of the motor.

FIG. 5 shows a specific circuit example of the stepping motor, and FIG. 6 shows a timing chart of its operation. FIG.
1, 2, 3, and 4 indicate detection points of the induced voltage.
6 are timing charts at the detection points.

The time up to t0 in FIG. 6 indicates a state where the motor is stopped with no electric input. Power is supplied to the A phase from t0 to t1. When power is supplied to the phase A from t0, the potential at the point 2 decreases due to the movement of the rotor R,
Vth is reached. When Vth is reached, a signal is sent from the detection circuit 4 to the CPU 1 in FIG. 1, and a signal for switching from the A phase to the B phase is sent from the CPU 1 to the stepping motor drive circuit 2 in FIG. Then, when power is supplied to the B phase, the potential at the point 3 decreases due to the movement of the rotor R,
Vth is reached. When the voltage reaches Vth, the detection circuit 4 outputs C
A signal is sent to PU1, a signal for switching from B phase to A 'phase is sent from CPU 1 to stepping motor drive circuit 2, and power is supplied to A' phase. Such an operation is sequentially repeated, and the rotor R keeps rotating stepwise.

In the present invention, the stepping motor is driven as described above. If the load on the rotor R increases, the rotation speed decreases, so that the generation timing of the induced voltage is delayed, and as a result, the drive phase switching timing of the stepping motor is delayed. When the load is removed, the rotation speed of the rotor R increases, so that the generation timing of the induced voltage becomes earlier, and as a result, the drive phase switching timing of the stepping motor becomes earlier. In other words, the rotation speed decreases when the load increases, and increases when the load is removed. This means that the operation is reliably performed with the minimum power according to the load.

Further, even when the voltage fluctuates, if the voltage drops, the torque of the stepping motor decreases, so that the rotation speed is slowed and the generation timing of the induced voltage is delayed. As a result, the drive phase switching timing of the stepping motor is reduced. Become slow. When the voltage increases, the torque of the stepping motor increases, so that the rotation speed increases and the generation timing of the induced voltage becomes earlier, and as a result, the drive phase switching timing of the stepping motor becomes earlier.
That is, as the voltage decreases, the rotation speed decreases, and as the voltage increases, the rotation speed increases. This means that the operation is reliably performed with the minimum power according to the voltage.

When the stepping motor is driven by the above-described driving method to open and close the shut-off valve, the load on the stepping motor increases rapidly when the valve body contacts the valve seat. When the load increases, the rotation speed of the rotor R decreases, so that the generation timing of the induced voltage is delayed, and as a result, the drive phase switching timing of the stepping motor is delayed. Therefore, when the valve element firmly contacts the valve seat, the induced power is eliminated.

Therefore, in the present invention, when the induced power is not generated for a certain period of time or longer, it is determined that the valve body is firmly in contact with the valve seat, the excitation phase is turned off, and the rotor R is automatically turned off. Stop. In this case, by changing the setting of the certain time, the degree of contact of the valve body with the valve seat (closed state) can be adjusted.

FIG. 7 shows an example of the structure of the stepping motor and the shut-off valve devised to make the above-mentioned stopping operation more reliable. Although the internal structure of the stepping motor 10 is shown in a simplified manner, the motor case 11 is attached to the lower surface of the valve body 13 of the shut-off valve 12 so that the valve body 13
Is fixed outside the valve chamber 14. The rotor shaft 15 of the rotor R is supported by upper and lower bearings 16 and 17 in the motor case 11, and a propulsion shaft 16 a integrally or directly connected to the rotor shaft 15 protrudes into the center of the valve chamber 14. A male screw 18 is engraved on the propulsion shaft 16a, and the male screw 18 is screwed with a female screw 20 provided on a valve body 19 in the valve chamber 14. A seal member 21 such as rubber is provided on the upper surface of the valve body 19.

On the upper surface of the valve chamber 14, a valve seat 23 forming a valve port 22 is provided so as to protrude, and a gas passage 24 is opened on a side surface of the valve chamber 14.

On the lower side of the valve element 19, a rotation stopping projection 26 having a through hole 25 is integrally provided.
In addition, a guide rod 27 fixed vertically in the valve chamber 14 penetrates. For this reason, the valve element 19 can move up and down, but cannot rotate.

On the other hand, the rotor shaft 15 is also provided with the upper and lower bearings 1.
6 and 17 can be slid up and down. Then, between the rotor R and the lower bearing 17,
A coil spring 28 is wound around the rotor shaft 15 as a spring material.

In such a structure, when the rotor R rotates forward with the rotor shaft 15, the valve body 19 screwed with the rotor shaft 15 does not rotate and is propelled upward, so that the sealing material 21 abuts on the valve seat 23. Upon contact, the valve port 22 is closed.
When the valve body 19 is further raised and the sealing material 21 is strongly pressed against the valve seat 23, the rotor shaft 15 moves the stopped valve body 1
9, the rotor R rotates while compressing the coil spring 28. As a result, a braking force is applied to the rotor R, and the rotor R is stopped by detecting the disappearance of the induced voltage as described above while receiving the braking force.

Accordingly, by setting the spring force of the coil spring 28, the sealing member 21 of the valve body 19 is
3 can be roughly set, and by adjusting the above-mentioned fixed time at the time of stop, the valve body 19 with respect to the valve seat 23 can be set.
The rotor R can be stopped with the pressing force of the rotor R substantially constant.

[0036]

According to the present invention, the sensing signal for switching the excitation phase is detected from the induced power generated in the drive coil.
This can be done by sensing the induced voltage generated in the coil not used for driving, and when the sensing signal due to the induced power cannot be obtained for a certain period of time, the excitation phase is turned off. Even if the load fluctuates, the drive phase switching and the stop operation will be performed according to the rotational position of the rotor under the situation,
It can be driven and stopped reliably with low power. In particular, since the stop operation is performed using the drive coil itself as the detection coil, the automatic stop can be performed at low cost without using an external sensor or the like.

In the application to a shut-off valve for a gas meter,
Since a lithium battery is generally used as a power source, it is important to reduce current consumption, and it is necessary to reliably open and close even if voltage fluctuations and the distance between a valve seat and a valve element vary. According to the present invention, a sufficient effect can be obtained.

For example, when a braking force is applied to the rotor immediately before its stop by the spring material interposed between the rotor shaft and the bearing, the stop operation can be performed more reliably.
When used for a shut-off valve, after the valve element of the shut-off valve abuts the valve seat with the thrust due to the rotation of the rotor shaft, the thrust in the opposite direction acts on the rotor shaft, and the spring material is compressed by the rotor.
If a braking force is applied to the rotor, the rotor can be stopped after the shutoff valve is securely closed.

Accordingly, the present invention provides a shut-off valve for a gas meter which is not required to have a constant speed, low power and no spark, and to be able to open and close reliably even if there is a variation in products. In particular, the present invention can exert a particularly excellent effect.

[Brief description of the drawings]

FIG. 1 is a block diagram of a configuration for driving a stepping motor according to the present invention.

FIG. 2 is a conceptual diagram of an operation of a stepping motor.

FIG. 3 is a diagram illustrating a relationship between a driving phase of a stepping motor and a polarity of a stator pole.

FIG. 4 is a diagram illustrating the principle of generation of an induced voltage by movement of a rotor.

FIG. 5 is an electric circuit diagram showing a specific circuit example of a stepping motor.

FIG. 6 is a timing chart of the operation of the stepping motor.

FIG. 7 is a cross-sectional view of a stepping motor and a shutoff valve that is opened and closed by the stepping motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 Stepping motor drive circuit 3 Stepping motor 4 Detection circuit R Rotor S1 ・ S2 ・ S3 ・ S4 Stator pole 10 Stepping motor 12 Shutoff valve 15 Rotor shaft 16.17 Bearing 19 Valve body 23 Valve seat 28 Coil spring (spring material)

Claims (9)

[Claims] 1. A sensing signal for switching an excitation phase,
A method for stopping driving of a stepping motor, comprising detecting an induced power generated in a drive coil, and turning off an excitation phase when a sensing signal based on the induced power cannot be obtained for a predetermined time or more. 2. A sensing signal for switching an excitation phase,
A method for stopping driving of a stepping motor, comprising detecting an induced power generated in a drive coil to which power is not supplied, and turning off an excitation phase when a sensing signal based on the induced power is not obtained for a predetermined time or more. 3. The method according to claim 1, wherein:
3. The method according to claim 1, wherein a braking force is applied immediately before the stop. 4. A braking force is applied by a spring material interposed between a rotor shaft and a bearing.
The method for stopping driving of a stepping motor according to claim 3. 5. A method for stopping driving of a stepping motor for opening and closing a shutoff valve, wherein a sensing signal for switching an excitation phase is detected from an induced power generated in a drive coil, and a sensing signal based on the induced power is obtained for a predetermined time or more. A driving stop method for a stepping motor, wherein the excitation phase is turned off when the stepping motor runs out. 6. A method for stopping the driving of a stepping motor for opening and closing a shutoff valve, wherein a sensing signal for switching an excitation phase is detected from an induced power generated in a drive coil that is not supplied with power, and a sensing signal based on the induced power is constant. A method for stopping the driving of a stepping motor, characterized in that the excitation phase is turned off when no more time can be obtained. 7. The stepping motor according to claim 1, wherein:
Applying a braking force after the shut-off valve is closed,
The method for stopping driving of a stepping motor according to claim 5. 8. The method for stopping driving of a stepping motor according to claim 7, wherein the braking force is applied by a spring material interposed between the rotor and a bearing of the rotor shaft. 9. After the valve element of the shut-off valve comes into contact with the valve seat by the thrust due to the rotation of the rotor shaft, the thrust in the opposite direction acts on the rotor shaft, and the spring material is compressed by the rotor. The method for stopping driving of a stepping motor according to claim 8, wherein a braking force is applied.