JP7539062B2 - Stepping motor abnormality detection device - Google Patents

Description

The present invention relates to a device that detects abnormalities in the drive of a stepping motor. In particular, the present invention relates to a device that detects abnormalities in a stepping motor used in a two-way valve that opens and closes the flow of gas used in a gas meter.

Patent document 1 discloses a shutoff valve device that determines whether a stepping motor is in a stalled state or out of step state.

This shutoff valve device is equipped with a drive control circuit section that controls the drive of the stepping motor, and a valve movement abnormality circuit section that determines whether the stepping motor is in a stalled state or out of step. This makes it possible to determine whether the stepping motor is in a stalled state or out of step by comparing the maximum value or the wave height of the maximum value in the drive voltage waveform detected from the stepping motor with a predetermined threshold value.

Patent document 2 discloses a method for detecting out-of-step of a stepping motor. This method converts the motor current waveform in a stepping motor driver that drives the stepping motor into a square wave, converts the square wave into a voltage signal, and determines whether or not an out-of-step state exists by comparing the obtained voltage value with a reference voltage.

JP 2006-118642 A JP 1999-187697 A

Both Patent Document 1 and Patent Document 2 focus on the difference in current and voltage waveforms during normal operation and during out-of-step operation. This makes it possible to detect the difference in the waveforms in a stable out-of-step state, but in reality, the stepping motor often repeats unstable operation, rotating slightly and then returning. In such cases, the difference in the waveforms becomes unclear, making it difficult to distinguish between normal operation and out-of-step operation.

The present invention provides a stepping motor anomaly detection device that corrects waveforms detected in an unstable state and is effective in stably detecting anomalies in a stepping motor.

The stepping motor abnormality detection device of the present invention is configured to include a stepping motor drive unit that outputs a drive pulse for driving a stepping motor, a power supply unit that supplies power to the stepping motor drive unit, a current level detection unit that detects the level of a current flowing through the stepping motor drive unit, a first memory unit that stores a first current level detected by the current level detection unit at a first timing, a second memory unit that stores a second current level detected by the current level detection unit at a second timing that is separated from the first timing by a predetermined time width or more, and a determination unit that determines that an operational abnormality of the stepping motor exists when the difference between the first current level and the second current level is equal to or greater than a predetermined value.

The anomaly detection device of the present invention is effective in detecting anomalies in a stepping motor caused by disconnection or tampering in an unstable operating environment.

FIG. 1 is a block diagram showing a configuration of a stepping motor abnormality detection device according to a first embodiment. 1 is a signal diagram of an output value of an analog-to-digital converter according to the first embodiment. FIG. 1 is a diagram showing the waveforms of driving pulses and signals at various parts in the first embodiment.

The first invention is a stepping motor abnormality detection device comprising: a stepping motor drive unit that outputs a drive pulse for driving a stepping motor; a power supply unit that supplies power to the stepping motor drive unit; a current level detection unit that detects the level of a current flowing through the stepping motor drive unit; a first memory unit that stores a first current level detected by the current level detection unit at a first timing; a second memory unit that stores a second current level detected by the current level detection unit at a second timing that is separated from the first timing by a predetermined time width or more; and a determination unit that determines that an operation abnormality occurs in the stepping motor when the difference between the first current level and the second current level is a predetermined value or more.

The second invention is particularly characterized in that in the first invention, the current level detection unit includes an integration circuit that integrates the instantaneous current flowing through the stepping motor drive unit and detects the output of the integration circuit.

The third invention is particularly the second invention, in which a resistor is inserted between the power supply unit and the stepping motor drive unit, and the integrating circuit is configured to integrate the voltage at the connection point between the resistor and the stepping motor drive unit using a capacitor via the resistor.

The fourth invention is particularly characterized in that in any one of the first to third inventions, the first timing and the second timing are delayed by a predetermined time from the rising edge of the drive pulse.

The fifth invention is particularly characterized in that, in any one of the first to fourth inventions, there is a two-way valve operated by the stepping motor, and the first timing is set immediately after the two-way valve starts to operate, and the second timing is set immediately before the two-way valve stops operating.

The sixth invention is particularly characterized in that in any one of the first to fifth inventions, the determination unit determines that an operational abnormality of the stepping motor exists when the second current level is outside a predetermined range.

Below, an embodiment of the present invention will be described with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicate explanations of substantially identical configurations may be omitted. This is to avoid making the following explanation unnecessarily redundant and to make it easier for those skilled in the art to understand.

The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
FIG. 1 is a block diagram showing an example of the configuration of a stepping motor abnormality detection device in an embodiment of the present invention, and FIGS. 2 and 3 are signal diagrams for explaining the operation of detecting an abnormality in a stepping motor in embodiment 1.

[1. Configuration]
The configuration of the first embodiment will be described with reference to Fig. 1. The output voltage (voltage a) of a power supply unit 1 is applied to a stepping motor driving unit 3 via a current level detection unit 2. The output of the stepping motor driving unit 3 is connected to a stepping motor 4, and a two-way valve 5 is opened and closed by the rotation of the stepping motor 4.

The current level detection unit 2 utilizes the fact that the potential difference between voltage a and voltage b at both ends of resistor 21 is proportional to the current flowing through resistor 21, and the potential difference is converted to a digital signal by analog-digital conversion unit 24 and output as an AD value. The integration circuit 25 is composed of resistor 22 and capacitor 23, and smooths out changes in the output signal b of resistor 21. The output of integration circuit 25 is then input to analog-digital conversion unit 24 as voltage c.

The output (AD value) of the analog-to-digital conversion unit 24 is input to the first storage unit 6 and the second storage unit 7, and the AD value at a certain timing is stored. The determination unit 8 then compares the stored value of the first storage unit 6 with the stored value of the second storage unit 7 to determine whether or not there is an abnormality in the stepping motor 4.

The stepping motor anomaly detection device in this embodiment is incorporated into a gas meter, and the two-way valve 5 is used as a shutoff valve that cuts off and opens the flow of gas. When incorporated into a gas meter, a lithium battery, which is the power source for the gas meter, is used as the power supply unit 1.

The stepping motor 4 also has multiple coils, and the direction of rotation of the motor is determined by the state of the pulses applied to each coil. The direction of rotation of the motor determines whether the two-way valve opens or closes. Although not shown in Figure 1, it has a control unit that controls the overall operation, which will be described below.

2. Operation
The operation of the embodiment of the present invention configured as above will be described with reference to FIG.

Figure 2 is a graph showing the AD value, which is the output of the analog-to-digital converter 24 during the closing operation when the two-way valve 5 of the stepping motor anomaly detection device of this embodiment is used as a shutoff valve of a gas meter.

The analog-to-digital converter 24 converts the output (voltage c) of the integrator circuit 25 into a digital signal using the output (voltage a) of the power supply unit 1 as a reference voltage. In concrete terms, the integer value obtained by dividing voltage c by voltage a and multiplying the result by 1024 is output as the AD value. In FIG. 2, the vertical axis represents the AD value, and the horizontal axis represents time.

The first timing (a) is the timing immediately after the stepping motor driver 3 outputs a drive pulse and the stepping motor 4 starts to operate, and the second timing (b) is the timing immediately before the two-way valve 5 completes closing of the gas flow path. The drive pulse frequency is maintained at a constant frequency while the stepping motor 4 is being driven.

Graph b, indicated by a solid line, shows the case where the two-way valve 5 operates normally, and while the two-way valve 5 is operating, i.e., while the stepping motor 4 is rotating normally, there is no change in the current flowing through the resistor 21, and there is almost no difference between the AD value at the first timing (A) and the AD value at the second timing (B). In graph b, the AD value drops immediately after the second timing (B), indicating that the gas flow path is closed by the two-way valve 5, the operation of the two-way valve 5 is stopped, and the load on the stepping motor 4 increases, causing an increase in the current flowing through the resistor 21.

Next, graph a, indicated by a dashed line, shows the case where the stepping motor 4 has two coils and one of them is broken. In this case, the current flowing through resistor 21 is half that during normal operation, and the AD value becomes larger accordingly. Furthermore, when one coil is broken, the operation of the stepping motor 4 becomes unstable and the load on the stepping motor 4 fluctuates. Therefore, when a coil is broken, the current flowing through resistor 21 changes, and a difference occurs between the AD value at the first timing (a) and the AD value at the second timing (b), as shown in graph a.

Next, graph c, shown by a dotted line, shows a case where an object is caught in the gas flow path of the gas meter due to tampering or other reasons, causing the two-way valve 5 to malfunction and stop operating partway through the closing operation of the two-way valve 5. When the operation of the two-way valve 5 stops, the load on the stepping motor 4 increases, and the current flowing through the resistor 21 increases, causing the AD value to decrease. In other words, if the operation of the two-way valve 5 stops due to tampering or other reasons between the first timing (a) and the second timing (b), a difference occurs between the AD value at the first timing (a) and the AD value at the second timing (b).

As explained above, during normal operation, there is no significant difference between the AD value at the first timing (a) and the AD value at the second timing (b). However, if the operation of the two-way valve 5 becomes unstable or stops due to a broken wire or tampering, a significant difference will occur between the AD value at the first timing (a) and the AD value at the second timing (b).

The first memory unit 6 stores the AD value at the first timing (a), and the second memory unit 7 stores the AD value at the second timing (b). If the absolute value of the difference between the AD value stored in the first memory unit 6 and the AD value stored in the second memory unit 7 is greater than or equal to a predetermined value, the determination unit 8 determines that the stepping motor 4 is malfunctioning.

The first timing (a) is immediately after the operation of the stepping motor 4, and the second timing (b) is immediately before the end of the closing operation of the two-way valve 5. Although this timing is not essential, the longer the time between the first timing (a) and the second timing (b), the lower the probability of missing an abnormality due to tampering or the like.

In addition, the positions of the first timing (a) and the second timing (b) have been described as fixed, but for example, the maximum value of the AD value in the section from immediately after the operation of the stepping motor 4 to immediately before the end of the opening and closing operation of the two-way valve 5 can be stored in the first memory unit 6 as the first timing (a), and the minimum value of the AD value can be stored in the second memory unit 7 as the second timing (b).

Next, the relationship between the drive pulse that drives the stepping motor 4 and the voltages b and c will be explained with reference to FIG. 3. In FIG. 3, the vertical axis indicates the voltage level, and the horizontal axis indicates the time.

The stepping motor 4 has two coils (a first coil and a second coil), and the waveforms shown in Figures 3(1) and (2) show the waveforms of the drive pulse A and the drive pulse B applied to the two coils of the stepping motor 4. The solid line in Figure 3(3) shows the waveforms of the voltage b
The dashed dotted line indicates the waveform of voltage c.

Drive pulse A drives the first coil of stepping motor 4, and drive pulse B drives the second coil of stepping motor 4. Drive pulse B is delayed in phase from drive pulse A by 90 degrees. The direction of rotation of stepping motor 4 is determined by whether drive pulse B is delayed or advanced in phase from drive pulse A by 90 degrees.

The voltage b shown in FIG. 3 (3) corresponds to the waveform of the current flowing through the stepping motor 4. The stepping motor 4 is a coil load, and the waveform of the current flowing through the coil is a differential waveform as shown by voltage b. Therefore, it is possible to directly input voltage b to the analog-digital conversion unit 24 and convert voltage b to an AD value without using the integrating circuit 25 consisting of resistor 22 and capacitor 23. In this case, however, the AD value will vary greatly depending on where in the drive pulse the sampling timing is set in the analog-digital conversion unit 24.

Therefore, when the integrating circuit 25 is not used, it is important to set the sampling timing to a constant timing with respect to the drive pulse, and the timing delayed by a time τ from the rising edge of the drive pulse A is set as the AD conversion timing of the analog-to-digital converter 24. Note that by AD converting the voltage c via the integrating circuit 25, there is an advantage in that the effect of the AD conversion timing on the AD value can be reduced.

The graph shown in Figure 2 is a graph of the AD values obtained at the AD conversion timing described in Figure 3 arranged in chronological order.

In addition, by adding a judgment in the judgment by the judgment unit 8 that if the AD value at the second timing (b) exceeds a predetermined range, for example, if it is equal to or greater than the first AD value (AD1 shown in FIG. 2), it is determined that there is a disconnection, and if it is equal to or less than the second AD value (AD2 shown in FIG. 2), it is determined that the two-way valve has stopped operating due to tampering, etc., it is possible to more accurately detect an abnormality in the stepping motor. Note that AD1 and AD2 can be preset to appropriate values for the AD value during normal operation.

[3. Effects, etc.]
As described above, in this embodiment, even if the operation of the stepping motor 4 becomes unstable due to a broken wire, tampering, or the like, an abnormality in the stepping motor can be accurately detected.

In this embodiment, a method for detecting an abnormality in the stepping motor 4 during the closing operation of the two-way valve 5 has been described, but it goes without saying that the method can also be applied to the opening operation.

The above-described embodiments are intended to illustrate the technology disclosed herein, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

The present invention is particularly applicable to stepping motors that drive two-way valves built into gas meters, etc.

REFERENCE SIGNS LIST 1 Power supply unit 2 Current level detection unit 3 Stepping motor drive unit 4 Stepping motor 5 Two-way valve 6 First storage unit 7 Second storage unit 8 Determination unit 21 Resistor 22 Resistor 23 Capacitor 24 Analog-to-digital conversion unit

Claims (4)

A stepping motor having a plurality of coils;
a stepping motor driver that outputs a plurality of drive pulses corresponding to each of the plurality of coils;
a power supply unit that supplies power to the stepping motor drive unit;
a current level detection unit that detects a level of a current flowing through the stepping motor drive unit;
a first storage unit configured to store a first current level detected by the current level detection unit at a first timing when the drive pulse is output;
a second storage unit configured to store a second current level detected by the current level detection unit at a second timing that is separated from the first timing by a predetermined time width or more and at which the drive pulse is being output;
a determination unit that determines that an operation abnormality occurs in the stepping motor when a difference between the first current level and the second current level is outside a predetermined value range;
Equipped with
The plurality of driving pulses are out of phase with each other,
The stepping motor abnormality detection device according to claim 1, wherein the first timing and the second timing are delayed by a predetermined time from a rising edge of the drive pulse. The stepping motor abnormality detection device according to claim 1, characterized in that the current level detection unit includes an integrating circuit that integrates the instantaneous current flowing through the stepping motor drive unit, and the output of the integrating circuit is converted into a digital signal by an analog-to-digital conversion unit. The stepping motor abnormality detection device according to claim 2, wherein a resistor is inserted between the power supply unit and the stepping motor drive unit, and the integrating circuit is configured to integrate the voltage at the connection point between the resistor and the stepping motor drive unit using a capacitor via the resistor. The stepping motor abnormality detection device according to any one of claims 1 to 3, characterized in that it has a two-way valve operated by the stepping motor, the first timing is set immediately after the two-way valve starts to operate, and the second timing is set immediately before the two-way valve stops to operate.