JPH11332087A - Abnormality detector for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of an overall equipment and lower the cost and a current loss. SOLUTION: A drive circuit 2 for a motor 3 is constituted of an H-bridge circuit 1, constituted of four power devices Q1-Q4 and diodes D1-D4 connected to the power devices Q1-Q4 respectively. The drive circuit 2 supplies driving current to the motor 3 by turning on a pair of power devices Q1, Q4 or Q2, Q3, while turning off the remaining pair of power devices Q2, Q3 or Q1, Q4. An abnormality detector is provided with two voltage detecting circuits 7, 8 and a microcomputer 6. When the pair of power devices Q1, Q4 or Q2, Q3 which have been turned on for cutting off the supply of power to the motor 3 are turned off, each of the voltage detecting circuits 7, 8 detects the forward voltage appearing in the diode D2 or D1 connected to the power devices Q2, Q3 or Q1, Q4, based on the counter electromotive force appearing in the motor 3. The microcomputer 6 determines that there is an abnormality in the motor 3, when no voltage is detected by the voltage detecting circuits 7, 8 at the time of appearance of counter electromotive force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor used for, for example, electronic control of a throttle valve in an automobile engine, and to a motor abnormality detecting device suitable for detecting an abnormality of the motor.

[0002]

2. Description of the Related Art Conventionally, as this kind of motor, there is a motor driven by a drive circuit including an H-bridge circuit composed of four power elements. In this type of motor,
When the motor wire is grounded or the power element is short-circuited, a short-circuit current flows through the motor or the power element, which may cause abnormal operation of the motor or breakage of the power element. Therefore, an abnormality detection device that monitors a current flowing in a motor drive circuit and detects an overcurrent that is equal to or more than a certain value as an abnormality has been proposed.

Japanese Patent Laying-Open No. 4-46867 discloses an example of this type of abnormality detection device. As shown in FIG. 7, the abnormality detection device of this publication targets a drive circuit 22 including an H-bridge circuit 21 composed of first to fourth four power elements Q1, Q2, Q3, Q4. The H-bridge circuit 21 includes first to fourth diodes D1, D2, D3 connected in parallel to the respective power elements Q1 to Q4.
D4. The control device 23 includes the power devices Q1 to Q
By controlling on / off of the control signal 4, the current supply to the motor 24 is controlled. This abnormality detection device includes a first current detection circuit 25 and a second current detection circuit 26. The first current detecting circuit 25 includes a first current detecting resistor (shunt resistor) 27 connected in series to the motor 24, and the second current detecting circuit 26 includes a second shunt resistor also connected in series to the motor 24. A resistor 28 is provided. The first current detection circuit 25 detects a current flowing through the drive circuit 22 and thus a current flowing through the motor 24 by detecting a voltage between terminals of the first shunt resistor 27. The second current detection circuit 26 detects a current flowing through the motor 24 by detecting a voltage between terminals of the second shunt resistor 28.

When the motor 24 is normal, the control device 23 turns on the first and fourth power elements Q1 and Q4 and turns off the second and third power elements Q2 and Q3.
A current flows through the motor 24 in the positive direction A. Thereafter, the control device 23 turns off the first and fourth power elements Q1 and Q4 and turns off the second and third power elements Q2 and Q3, so that a back electromotive force is generated in the coil of the motor 24, A current flows in the positive direction A in the order of the third diode D3, the motor 24, and the second diode D2, and the coil energy is consumed. On the other hand, when the control device 23 turns on the second and third power elements Q2 and Q3 and turns off the first and fourth power elements Q1 and Q4, a current flows in the motor 24 in the reverse direction B. After that, the control device 23 turns off the second and third power elements Q2 and Q3 and turns off the first and fourth power elements Q1 and Q4, so that the motor 2
A back electromotive force is generated in the coil No. 4 and the fourth diode D
4. A current flows in the reverse direction B in the order of the motor 24 and the first diode D1, and the coil energy is consumed.

Here, the current detection circuits 25 and 26 detect the current flowing through the drive circuit 22 and the motor 24 by their shunt resistors 27 and 28. That is, when a current flows through the shunt resistors 27 and 28, a potential difference proportional to the current is generated between the terminals of the shunt resistors 27 and 28. When an abnormality occurs due to disconnection of the motor 24, no current flows through the shunt resistors 27 and 28. When an abnormality occurs due to a short circuit in the motor 24, an excessive current flows through the shunt resistors 27 and 28. Each of the current detection circuits 25 and 26 detects the above-mentioned current change in the shunt resistors 27 and 28 and outputs it to the control device 23. The control device 23 controls each current detection circuit 2
An abnormality of the motor 24 is determined based on the current values from the motors 5 and 26, and the power supply to the motor 24 is cut off by turning off the power elements Q1 to Q4 as necessary.

[0006]

However, in the above-described conventional abnormality detecting device, since the external shapes of the shunt resistors 27 and 28 used for current detection are relatively large, they are provided on a printed circuit board. Special space is required. The shunt resistors 27 and 28 are connected to the motor 24.
Are connected in series to the resistors 27, 28
, The current loss tends to increase. Moreover, when the motor 24 is short-circuited, the shunt resistors 27, 28
Overheating may occur due to excessive current
It is necessary to increase the allowable current of the shunt resistors 27 and 28 themselves. Furthermore, a shunt resistor 2 having a large allowable current is used.
7 and 28 are generally expensive, so that there is also a problem that the cost of the entire apparatus increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor abnormality detecting device which can reduce the size of the entire device, reduce cost, and reduce current loss. To provide.

[0008]

In order to achieve the above object, an invention according to claim 1 comprises an H bridge circuit comprising four power elements and a diode connected in parallel to each of the power elements. An abnormality detection device for detecting an abnormality of a motor driven by a drive circuit comprising: a drive circuit that turns on a pair of power elements that correspond to each other among the four power elements, and that corresponds to the remaining ones. The drive current is supplied to the motor by turning off the pair of power elements, and when the pair of power elements turned on to cut off the current supplied to the motor is turned off. Voltage detecting means for detecting a voltage generated by a diode connected to the remaining pair of power elements based on a back electromotive force generated by the motor; When no voltage is detected by means, the purpose that a determination means for determining that the abnormality of the motor.

According to the above configuration, the voltage generated by the diode is connected to each power element of the H-bridge circuit based on the back electromotive force generated by the motor when the supply current is cut off. The voltage is detected by the voltage detecting means. Therefore, unlike the case where a current detection resistor (shunt resistor) is provided, there is no need to provide a special space on the printed circuit board. Further, since the voltage of the diode is detected using the back electromotive force generated by the motor, useless current is not consumed for detecting the voltage. Further, since the diode incorporated in the H-bridge circuit is used, the diode itself is not expensive.

According to a second aspect of the present invention, in order to achieve the above object, in the configuration of the first aspect, the voltage detecting means is two voltage detecting circuits separately provided for two different diodes. Each voltage detection circuit detects a voltage generated by a corresponding diode based on a counter electromotive force generated in the motor in both forward and reverse directions.

According to the configuration of the present invention, in addition to the function of the first aspect of the present invention, the voltage generated by the corresponding diode in accordance with the counter electromotive force generated by the motor in both the forward and reverse directions is detected by the two voltage detection circuits. I try to detect. Therefore,
Regardless of the difference in the direction of the current supplied to the motor, it is possible to detect the voltage based on the back electromotive force in both the forward and reverse directions.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Hereinafter, a first embodiment of a motor abnormality detecting device according to the present invention will be described in detail with reference to FIGS. In this embodiment, it is assumed that the present invention is embodied in a motor abnormality detecting device used for electronic control of a throttle valve in an automobile engine.

FIG. 1 is an electric circuit diagram of a motor abnormality detecting apparatus according to the present embodiment. This abnormality detection device includes a drive circuit 2 including an H-bridge circuit 1 including four power elements Q1, Q2, Q3, and Q4. This drive circuit 2 is for driving the motor 3. The H-bridge circuit 1 includes first to fourth diodes D connected in parallel to the respective power elements Q1 to Q4.
1, D2, D3, and D4. This H-bridge circuit 1
Is composed of an electric field transistor (FET), and each of the diodes D1 to D4 is
A parasitic (built-in) diode between the drain and source of Q4. The protection circuit 4 and the battery 5 are connected in series to the H-bridge circuit 1, respectively. In the H-bridge circuit 1, the motor 3 includes first and third power elements Q1,
Q3, and the second and fourth power elements Q2, Q3
Are connected respectively. The protection circuit 4 is for interrupting the supply of current to the drive circuit 2 (H bridge circuit 1) when the motor 3 or the like is abnormal. Drive circuit 2
(H bridge circuit 1) includes four power elements Q1 to Q4.
Of the pair of first and fourth power elements Q1 and Q4 corresponding to each other, and turns on the pair of second
By turning off the third power elements Q2 and Q3, a current in the positive direction A for driving is supplied to the motor 3. On the other hand, the drive circuit 2 (H bridge circuit 1) turns on the corresponding pair of second and third power elements Q2 and Q3, and turns off the remaining pair of first and fourth power elements Q1 and Q4. This supplies a reverse current B for driving to the motor 3.

A microcomputer 6 corresponding to the judgment means of the present invention
Controls the drive circuit 2 (H-bridge circuit 1) by selectively turning on / off each of the power elements Q1 to Q4, and controls the supply of current to the motor 3;
The direction of the current is switched between forward direction A and reverse direction B. For this purpose, the sources of the power elements Q1 to Q4 are connected to the output terminals of the microcomputer 6, respectively. Protection circuit 4
Is connected to the output terminal of the microcomputer 6.

The abnormality detecting device includes a first voltage detecting circuit 7 and a second voltage detecting circuit 8. The first voltage detection circuit 7 is for detecting a forward voltage in the second diode D2 connected to the second power element Q2.
The second voltage detection circuit 8 is for detecting a forward voltage in the first diode D1 connected to the first power element Q1. First and second voltage detection circuits 7, 8
Constitutes voltage detecting means of the present invention. First
The voltage detection circuit 7 of the first embodiment detects the back electromotive force generated in the motor 3 when the first and fourth power elements Q1 and Q4 turned on to cut off the current in the positive direction A supplied to the motor 3 are turned off. This is for detecting a forward voltage generated in the second diode D2 connected to the second power element Q2 based on the power. When the second voltage detection circuit 8 turns off the second and third power elements Q2 and Q3 that are turned on to cut off the reverse current B supplied to the motor 3,
This is for detecting a forward voltage generated by the first diode D1 connected to the first power element Q1 based on the back electromotive force generated by the motor 3. Each voltage detection circuit 7,
8 has a comparator, an amplifier, an AD converter, etc., compares the forward voltage generated by the corresponding diodes D2, D1 with a predetermined threshold value, and when the forward voltage exceeds the threshold value, The forward voltage is amplified and output as a detection signal. The output terminals of the voltage detection circuits 7 and 8 are:
Each is connected to the input terminal of the microcomputer 6. The microcomputer 6 inputs the presence or absence of a voltage detection signal from each of the voltage detection circuits 7 and 8 via a built-in AD converter when a back electromotive force occurs in the motor 3. When the forward voltage is not detected in the corresponding diodes D2 and D1 by the voltage detection circuits 7 and 8, the microcomputer 6 determines that the motor 3 is abnormal and executes a predetermined process for fail-safe. I do. On the other hand, microcomputer 6
Determines that the motor 3 is normal when the forward voltage is detected by each of the voltage detection circuits 7 and 8.

When the motor 3 is normal, the microcomputer 6 turns on the first and fourth power elements Q1 and Q4 and turns off the second and third power elements Q2 and Q3. Current flows in the forward direction A, and the motor 3 rotates forward. Thereafter, the microcomputer 6 sets the first and fourth power elements Q
1, Q4 are turned off, and the second and third power elements Q2, Q2 are turned off.
By turning off 3, a back electromotive force is generated in the coil of the motor 3, and a current flows in the positive direction A in the order of the third diode D 3, the coil of the motor 3, and the second diode D 2,
The coil energy is digested. On the other hand, the microcomputer 6 turns on the second and third power elements Q2 and Q3 and turns off the first and fourth power elements Q1 and Q4. 3 is reversed. Thereafter, the microcomputer 6 sets the second and third power elements Q
2, Q3 are turned off, and the first and fourth power elements Q1, Q
By turning off 4, a back electromotive force is generated in the coil of the motor 3, and a current flows in the reverse direction B in the order of the fourth diode D4, the coil of the motor 3, and the first diode D1,
The coil energy is digested. Thus, the motor 3
Is normal, based on the back electromotive force generated in the motor 3,
A forward voltage is generated in the first or second diode D1, D2. If an abnormality such as a disconnection occurs in the motor 3, the first or second diode D1, D2
Then, no forward voltage is generated.

Next, the contents of processing executed by the microcomputer 6 to detect an abnormality of the motor 3 will be described with reference to the flowchart of FIG.

In step 100, the microcomputer 6 turns on the protection circuit 4 and turns off all the power elements Q1 to Q4 for initialization.

In step 110, the microcomputer 6
After the first and fourth power elements Q1 and Q4 are turned on for a predetermined time to supply a current in the positive direction A to the motor 3, the first and fourth power elements Q1 and Q4 are turned off to cut off the current supply to the motor 3. Power elements Q1 and Q4 are turned off.

In step 120, the microcomputer 6
It is determined whether or not the first voltage detection circuit 7 detects the forward voltage. Here, if no forward voltage is detected, the microcomputer 6 determines that an abnormality has occurred in the motor 3 or the drive circuit 2, and shifts the processing to step 170. Abnormalities here include disconnection of the motor 3, short-circuit of the terminals of the motor 3,
Alternatively, a malfunction of the drive circuit 2 or the like may be considered.

In step 170, the microcomputer 6
In order to cut off the supply of the current to the drive circuit 2, the protection circuit 4 is turned off, and the subsequent processing is temporarily terminated.

On the other hand, if the forward voltage is detected in step 120, the microcomputer 6 determines that the motor 3 or the drive circuit 2 is normal, and determines in step 130 whether there is a request for reversal of the motor 3. Judge. Here, when there is no inversion request, the microcomputer 6 repeats the processing from step 110.

If there is an inversion request in step 130, the microcomputer 6 turns on the second and third power elements Q2 and Q3 for a predetermined time in step 140 in order to supply a current in the reverse direction B to the motor 3. After that, the motor 3
The second and third power elements Q2 and Q3 are turned off in order to cut off the supply of current to the power supply.

In step 150, the microcomputer 6
It is determined whether or not the forward voltage is detected by the second voltage detection circuit 8. Here, when the forward voltage is not detected, the microcomputer 6 determines that an abnormality has occurred in the motor 3 or the drive circuit 2, executes the process of step 170, and temporarily ends the subsequent processes.

On the other hand, if the forward voltage is detected in step 150, the microcomputer 6 determines that the motor 3 or the drive circuit 2 is normal, and determines in step 160 whether there is a request for reversal of the motor 3. Judge. Here, when there is no inversion request, the microcomputer 6 repeats the processing from step 110. When there is an inversion request, the microcomputer 6 temporarily ends the subsequent processing.

FIGS. 3 (a) to 3 (h) are time charts showing the behavior of various parameters relating to the processing contents of steps 120 and 150. Now, as shown in FIGS. 3A and 3B, the pair of power elements Q1, Q4 and Q2, Q3 are repeatedly turned on and off, and the motor 3 also has a current in the positive direction A,
It is assumed that the current in the reverse direction B flows alternately.

When the motor 3 and the drive circuit 2 are normal, at time t1 and t3, one of the power elements Q1 and Q4 is turned off, and as shown in FIG. A forward voltage is generated in the diode D2. First
The voltage detection circuit 7 amplifies this forward voltage, and when the value exceeds a predetermined threshold value, outputs a detection signal shaped as shown in FIG. 3 (e). The microcomputer 6 determines that the motor 3 and the drive circuit 2 are normal based on the input of the detection signal.

Similarly, when the motor 3 and the drive circuit 2 are normal, the other pair of power elements Q2 and Q3 are turned off at times t2 and t4, as shown in FIG. A forward voltage is generated in the first diode D1. The second voltage detection circuit 8 amplifies the forward voltage and, when the value exceeds a predetermined threshold value, outputs a detection signal shaped as shown in FIG. The microcomputer 6 determines that the motor 3 and the drive circuit 2 are normal based on the input of the detection signal.

On the other hand, when there is an abnormality in the motor 3 or the drive circuit 2, one of the power elements Q1 and Q4 is turned off at the time t1 and t3, whereby
As shown in (g), no forward voltage is generated in the second diode D2. Therefore, in the first voltage detection circuit 7, the value of the forward voltage does not exceed the predetermined threshold value,
No detection signal is output from the circuit 7. Microcomputer 6
Determines that the motor 3 or the drive circuit 2 is abnormal based on the fact that this detection signal is not input.

Similarly, when there is an abnormality in the motor 3 or the drive circuit 2, at time t2 and t4, the other pair of power elements Q2 and Q3 are turned off, as shown in FIG. No forward voltage is generated in the first diode D1. Therefore, in the second voltage detection circuit 8, the value of the forward voltage does not exceed the predetermined threshold value,
Does not output a detection signal. The microcomputer 6 determines an abnormality of the motor 3 or the drive circuit 2 based on the fact that the detection signal is not input.

As described above, according to the motor abnormality detecting apparatus of this embodiment, the motor 3 and the drive circuit 2
Is determined, and if an abnormality is detected, the protection circuit 4 is de-energized to cut off the supply of current to the drive circuit 2. Therefore, when an abnormality occurs, the motor 3 can be stopped as a fail-safe, and malfunction of the motor 3 can be prevented.

In this embodiment, each diode D1 connected to each power element Q1 to Q4 of the H-bridge circuit 1
To D4, when the supply current to the motor 3 is cut off, the forward voltage generated in each of the corresponding diodes D1, D2 based on the back electromotive force generated in the motor 3, and the corresponding voltage detection circuits 7, 8 To detect. Therefore, unlike the conventional abnormality detection device provided with a current detection resistor (shunt resistor), there is no need to provide a special space on the printed circuit board. Further, since the forward voltages of the corresponding diodes D1 and D2 are detected using the back electromotive force generated in the motor 3, no unnecessary current is consumed for voltage detection. Further, the FET H
Since the parasitic (built-in) diodes D1 and D2 incorporated in the bridge circuit 1 are used, the diode itself does not become expensive. Therefore, it is possible to reduce the size of the entire device, reduce the manufacturing cost of the device, and further reduce the current loss in the device.

According to the configuration of this embodiment, the motor 3
The voltage generated in each of the diodes D1 and D2 corresponding to the forward and reverse back electromotive force generated in the step S1 is detected by the two voltage detection circuits 7 and 8. Therefore, regardless of the difference in the direction of the current supplied to the motor 3, it is possible to detect the voltage based on the back electromotive force in both the forward and reverse directions. For this reason, it is possible to increase opportunities for abnormality detection in accordance with the reversible motor 3, and in that sense, it is possible to increase the reliability of abnormality detection.

[Second Embodiment] Next, a second embodiment of the motor abnormality detecting apparatus according to the present invention will be described with reference to FIG.
The description will be made in accordance with the following. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different points will be mainly described.

FIG. 4 is an electric circuit diagram of the motor abnormality detecting device according to the present embodiment. This circuit configuration differs from the circuit configuration of the first embodiment in that the second voltage detection circuit 8 is omitted. In this configuration, the motor 3
, Ie, when the motor 3 is rotated forward, the second diode D2
Is detected by the first voltage detection circuit 7.

FIG. 5 is a flowchart showing the processing executed by the microcomputer 6 to detect an abnormality of the motor 3. This flowchart is different from the first embodiment in that the forward voltage in the first diode D1 is not detected when the current in the reverse direction B is supplied to the motor 3, that is, when the motor 3 is rotated in the reverse direction. 2 is different from the flowchart of FIG.

FIGS. 6A to 6E are time charts showing the behavior of various parameters relating to the processing contents of step 120 described above. Now, as shown in FIGS. 6 (a) and 6 (b), the pair of power elements Q1 and Q4 are repeatedly turned on and off, and the current in the forward direction A and the current in the reverse direction B alternately flow through the motor 3. I do.

When the motor 3 and the drive circuit 2 are normal, only when one of the power elements Q1 and Q4 is turned off at times t1 and t2, as shown in FIG. A forward voltage is generated in the diode D2. First
The voltage detection circuit 7 amplifies this forward voltage, and when the value exceeds a predetermined threshold value, outputs a detection signal shaped as shown in FIG. 3 (d). The microcomputer 6 determines that the motor 3 and the drive circuit 2 are normal based on the input of the detection signal.

On the other hand, if there is an abnormality in the motor 3 or the drive circuit 2, one of the power elements Q1 and Q4 is turned off at the time t1 and t2, whereby
As shown in (e), no forward voltage is generated in the second diode D2. Therefore, in the first voltage detection circuit 7, the value of the forward voltage does not exceed the predetermined threshold value,
No detection signal is output from the circuit 7. Microcomputer 6
Determines that the motor 3 or the drive circuit 2 is abnormal based on the fact that this detection signal is not input.

In this embodiment, the timing of the abnormality detection may be performed when the motor 3 is rotated in the reverse direction. When the abnormality detection is performed periodically, when the first and fourth power elements Q1 and Q4 are turned on, the current flowing through the motor 3 is short enough not to substantially switch from the forward direction A to the reverse direction B. What is necessary is just to turn off both power elements Q1 and Q4 once within time, generate back electromotive force in the motor 3, and detect abnormality. When switching the current flowing through the motor 3 from the forward direction A to the reverse direction B, it is desirable to detect the abnormality once and then switch the current direction.

Therefore, in this embodiment, the abnormality is detected only when the current in the forward direction A is supplied to the motor 3 and the current is once interrupted. Other operations and effects are basically the same as those of the first embodiment.

The present invention is not limited to the above embodiments, but can be implemented as follows without departing from the spirit of the invention.

(1) In the above embodiments, when an abnormality of the motor 3 or the like is detected, the current supplied to the drive circuit 2 is forcibly cut off by the protection circuit 4 as fail-safe. I have. On the other hand, when an abnormality of the motor 3 or the like is detected, all the power elements Q1 to Q4 of the H-bridge circuit 1 may be turned off as fail-safe.

(2) In the first embodiment, the first and second diodes D1 and D2 correspond to the first and second diodes D1 and D2.
Although the voltage detection circuits 7 and 8 are provided, the first and second voltage detection circuits 7 and 8 may be provided corresponding to the third and fourth diodes D1 and D2.

(3) In the second embodiment, the first voltage detection circuit 7 is provided corresponding to the second diode D2, but the first voltage detection circuit 7 is provided corresponding to the other diodes D1, D3, and D4. May be provided.

[0046]

According to the first aspect of the present invention,
Utilizing diodes connected to each power element of the H-bridge circuit, a voltage detecting means detects a voltage generated in the diode based on a back electromotive force generated in the motor when a supply current to the motor is cut off, and detects the voltage. An abnormality of the motor is determined based on the result. Therefore, there is no need to provide a special space on the printed circuit board, no unnecessary current is consumed for voltage detection, and the diode does not become expensive. For this reason, it is possible to reduce the size, cost and current loss of the entire device.

According to the configuration of the second aspect of the present invention, in the configuration of the first aspect of the present invention, the voltage detecting means is two voltage detecting circuits provided in two different diodes, and each voltage detecting circuit The voltage generated in the corresponding diode is detected based on the counter electromotive force generated in the motor in both the forward and reverse directions. Accordingly, it is possible to detect the voltage based on the counter electromotive force in both the forward and reverse directions regardless of the difference in the direction of the current supplied to the motor. For this reason, in addition to the effect of the first aspect of the present invention, it is possible to increase the opportunities for abnormality detection in accordance with the reversible motor, and in that sense, it is possible to increase the reliability of abnormality detection. .

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a motor abnormality detection device according to a first embodiment.

FIG. 2 is a flowchart showing a process for detecting a motor abnormality.

FIGS. 3A to 3H are time charts showing behaviors of various parameters relating to abnormality detection.

FIG. 4 is an electric circuit diagram showing a motor abnormality detection device according to a second embodiment.

FIG. 5 is a flowchart showing a process for detecting a motor abnormality.

6A to 6E are time charts showing behaviors of various parameters related to abnormality detection.

FIG. 7 is an electric circuit diagram showing a conventional abnormality detection device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 H bridge circuit 2 drive circuit 3 motor 6 microcomputer (constituting determination means) 7 first voltage detection circuit (constituting voltage detection means) 8 second voltage detection circuit (constituting voltage detection means) Q1 to Q4 First to fourth power elements D1 to D4 First to fourth diodes

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G01R 31/34 G01R 31/34 A

Claims (2)

[Claims] An abnormality detection device for detecting an abnormality of a motor driven by a drive circuit including an H-bridge circuit including four power elements and a diode connected in parallel to each of the power elements. The driving circuit supplies a driving current to the motor by turning on a pair of power elements corresponding to each other among the four power elements and turning off a pair of power elements corresponding to each other. When turning off the pair of power elements that are turned on to cut off the current supplied to the motor, the remaining electromotive force generated in the motor is used as the remaining power. Voltage detecting means for detecting a voltage generated by a diode connected to the pair of power elements; and a voltage detected by the voltage detecting means when the back electromotive force is generated. A determination unit for determining that the motor is abnormal when the motor is not detected. 2. The motor abnormality detecting device according to claim 1, wherein said voltage detecting means is two voltage detecting circuits separately provided for two different diodes, and each of said voltage detecting circuits is a motor. A motor abnormality detecting device for detecting a voltage generated in a corresponding diode based on a back electromotive force in both forward and reverse directions generated in the motor.