JP2002238291A - Motor disconnection detection system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor disconnection detection system that can securely detect whether a motor or the like is disconnected or not even if the motor is at rest. SOLUTION: This motor disconnection detection system has motor control means (12 and 16) for alternately applying negative and positive voltages to the motor M in specific time ratio, a motor current detection means 14 for detecting current that flows in the motor M, signal conversion means (20 and 22) for differentiating detection output in the motor current detection means 14 for converting to a pulse signal, a count means 24 for counting the number of pulses of the pulse signal within unit time that is converted by the signal conversion means (20 and 22), and a judgment means 26 for judging that the motor M or the wiring system is disconnected when a count value that is counted by the count means 24 is smaller than a preset threshold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor disconnection detection system and a motor disconnection detection method for detecting the presence or absence of a disconnection in a motor and a wiring system thereof (hereinafter, simply referred to as a motor or the like).

[0002]

2. Description of the Related Art There is a conventional motor driving device having a structure as shown in FIG. The motor driving device 2 receives a power supply from a DC power supply E and drives a DC permanent magnet type motor M. The motor driving device 2 is a switching circuit formed by bridge-connecting four switching elements (here, FETs) Q1 to Q4. 10 and this switching circuit 10
A drive circuit 12 for controlling ON / OFF of each of the switching elements Q1 to Q4, a current detector 14 for detecting a current flowing through the motor M, and a controller 16 for controlling the drive circuit 12. C is a capacitor for absorbing a surge voltage generated by the switching operation of the switching circuit 10.

In the motor drive device 2 having this configuration, the drive circuit 12 outputs, for example, a pulse width-modulated control pulse to each of the switching elements Q1 to Q4 of the switching circuit 10, so that each of the switching elements Q1 to Q4 is output.
By turning on / off Q4, the motor M
Is adjusted to control the rotation speed of the motor M. Further, the controller 16 performs feedback control of the drive circuit 12 based on the detection output V1 from the current detector 14 so that the motor M rotates at a predetermined speed.

[0004] The motor drive control here will be described more specifically. As shown in FIG. 4, the time during which the two switching elements Q1 and Q4 are both on is represented by T
n and the time when both of the other two switching elements Q2 and Q3 are on is Tr, the on / off switching cycle T (= Tn + Tr) is always constant,
Forward and reverse rotation of the motor M is determined by the length of Tn and Tr. That is, in the case of Tn> Tr, the direction of the current of the motor M is in the direction shown in FIG. 3, and the motor M rotates forward, for example. Conversely, when Tn <Tr,
The direction of the electric current of the motor M is the direction shown by in FIG. As described above, the rotation speed of the motor M is determined by the difference (Tn-T) between the conduction time of one switching element Q1, Q4 and the other switching element Q2, Q3.
r).

Accordingly, the controller 16 gives a speed setting command to the drive circuit 12, and in response to this, the drive circuit 12 turns on one of the switching elements Q1 and Q4 and turns on the other switching elements Q2 and Q3. By adjusting the magnitude of the time Tr, the motor M is rotated forward or backward at a predetermined rotation speed.

When Tn = Tr, a current flows through the motor M for each energizing time Tn and Tr, so that the motor current has a pulsating flow as shown in FIG. Since the potentials at both ends of the motor M as viewed from the negative electrode terminal become equal, this is equivalent to a case where no voltage is applied to the motor M equivalently, and the motor M is forcibly stopped.

When the motor drive device 2 having such a configuration is used for an application in which unintended stopping of the motor M is not desirable for safety, the motor M and the like must be checked in order to investigate the cause of the failure of the motor M. It is necessary to detect the presence or absence of disconnection.

In order to detect the presence or absence of a disconnection of a motor or the like,
Conventionally, for example, the drive circuit 12 is controlled by a command from the controller 16 so that a relatively large current such that the motor M actually rotates flows through the motor M. Then, the motor current at this time is detected by the current detector 14, and if the motor current is not detected, it is determined that the motor or the like is in a disconnected state.

Alternatively, a rotation detector (not shown) such as a rotary encoder is provided on the motor M, and the controller 1
The drive circuit 12 is controlled by a command from the controller 6 so that a relatively large current, such as the actual rotation of the motor M, flows through the motor M. Then, the presence or absence of rotation of the motor M at this time is detected by a rotation detector, and if the detection output is not obtained, it is determined that the motor or the like is in a disconnected state.

[0010]

As described above, in the prior art, when checking for disconnection of a motor or the like, the motor M
Supplies a relatively large current to the motor M such that the motor M actually rotates, causing the following inconvenience.

For example, when the motor M is for driving a vehicle, when a relatively large current is passed through the motor M to check for disconnection of the motor or the like, when the motor or the like is disconnected, the vehicle There is no particular problem because the vehicle does not travel on its own, but when the motor or the like is not broken and is normal, the vehicle may travel unexpectedly and be dangerous.

When the motor M is for steering a vehicle and the motor M is driven in accordance with the amount of operation of the steering wheel, current flows through the motor M only when the steering wheel is operated. Therefore, the presence or absence of disconnection of the motor or the like cannot be detected unless the driver actually operates the steering wheel.

Therefore, in order to check for disconnection of the motor or the like, each time the driver must actually operate the steering wheel, it is troublesome. It is known that the motor or the like is disconnected only when it becomes, which is a problem in maintenance.

As described above, in the prior art, particularly in the case of a motor used for driving a vehicle or for steering a vehicle, it is necessary to detect in advance a disconnection of the motor or the like in a stopped state without running the vehicle or operating the steering wheel. Therefore, it is troublesome to check for a disconnection of the motor or the like, and there is a problem that it involves danger.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a motor disconnection detection system and a motor capable of reliably detecting the presence or absence of disconnection of a motor or the like even when the motor is stopped. It is an object to provide a disconnection detection method.

[0016]

The present invention employs the following structure to achieve the above object.

That is, a motor disconnection detection system according to the present invention comprises: a motor control means for applying positive and negative voltages to a motor; a motor current detection means for detecting a current flowing through the motor; Signal conversion means for differentiating the detection output of the current detection means to convert it into a pulse signal, counting means for counting the number of pulses per unit time of the pulse signal converted by this signal conversion means, and count value by this counting means Is smaller than a preset threshold value, the motor or its wiring system is determined to be in a disconnected state.

According to a second aspect of the present invention, in the motor disconnection detecting system according to the first aspect, the motor is a DC motor for steering or running the vehicle.

According to a third aspect of the present invention, there is provided a motor disconnection detecting method for applying positive and negative voltages to a motor, detecting currents flowing through the motor in response to the applied voltages, and differentiating the detection output to obtain a pulse. After conversion into a signal, the number of pulses of the pulse signal in a unit time is counted, and when the count value is smaller than a preset threshold value, it is determined that the motor or its wiring system is in a disconnected state. It is characterized by doing.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an entire motor disconnection detection system according to an embodiment of the present invention. Components corresponding to the prior art shown in FIG. 3 are denoted by the same reference numerals.

In the motor disconnection detecting system 1 of this embodiment, a disconnection detecting unit 3 is further provided for the motor driving device 2.

The motor driving device 2 has the same basic configuration as the conventional case shown in FIG. 3, and is a DC permanent magnet type motor M which is rotated by receiving power supply from a DC power source E.
On the other hand, four semiconductor switching elements (here, F
ET) Switching circuit 10 formed by bridge-connecting Q1 to Q4, and drive circuit 1 for controlling ON / OFF of switching elements Q1 to Q4 of switching circuit 10
2 and a current detector 14 for detecting a current flowing through the motor M
And a capacitor C for absorbing a surge voltage generated by the switching operation of the switching circuit 10, and a controller 16 for controlling the drive circuit 12. The current detector 14 corresponds to the motor current detecting means in the claims.

On the other hand, the disconnection detecting unit 3 includes a differential calculator 20 for differentiating the detection output of the current detector 14, a waveform shaping circuit 22 for shaping the output of the differentiator 20 and converting the output into a pulse signal. A counter 24 as a counting means for counting the number of pulses per unit time of a pulse signal obtained by shaping the waveform by the waveform shaping circuit 22. When the count value of the counter 24 is smaller than a preset threshold value, Is a judgment circuit 2 as judgment means for judging that the motor M or its wiring system is in a disconnected state.
6 and a notifying means 28 for notifying the judgment result of the judgment circuit 26 to the outside.

In this case, an alarm device such as a lamp or a buzzer, or an output device such as a monitor is used as the notification means 28 in this case. The differential calculator 20 and the waveform shaping circuit 22 serve as signal converting means in the claims, and the drive circuit 12 and the controller 16
Correspond to the motor control means in the claims, respectively.

Next, a method for detecting the presence / absence of disconnection of a motor or the like in the motor disconnection detection system 1 having the above configuration will be described with reference to a timing chart shown in FIG.

When detecting whether or not the motor or the like is disconnected, first, the drive circuit 12 is controlled by a command from the controller 16 to alternately apply positive and negative voltages to the motor M at a predetermined time ratio. Apply. For example, Tn =
It is controlled to be Tr. In this case, the current flowing through the motor M becomes a pulsating current having a small current value as shown in FIG. 5, but at this time, the potentials at both ends of the motor M as viewed from the negative terminal of the DC power supply E become equal. This is equivalent to a case where no voltage is applied to the motor, and the motor M is forcibly stopped.

In this state, the current flowing through the motor M is detected by the current detector 14. Therefore, the current detector 14 outputs a voltage signal V1 having a magnitude proportional to the detected motor current value, as shown in FIG.
Then, the voltage signal V1 is given to the disconnection detecting unit 3.

The differential calculator 20 of the disconnection detecting unit 3 is
Since the voltage signal V1 is differentiated, as shown in FIG. 2B, the DC signal component is removed and the voltage signal V1 having a differentiated waveform in which the pulsating component of the voltage signal V1 is amplified.
It becomes 2. Then, this voltage signal V2 is
2 is input. By removing the DC signal component, disconnection can be detected even when current is flowing through the motor.

The waveform shaping circuit 22 compares the input voltage signal V2 with the reference voltage Vth as shown in FIG. 2C, and when the voltage signal V2 is smaller than the reference voltage Vth (V2 <Vth). Is converted to a pulse signal V3 having a predetermined voltage Vcc when the voltage is higher than 0 V and higher than the reference voltage Vth (V2 ≧ Vth). Then, this pulse signal V3
Is input to the counter 24.

The counter 4 counts the number of pulses of the pulse signal V3 within a unit time. Then, after the elapse of the unit time, the count value K is given to the determination circuit 26 in the next stage.

The determination circuit 26 compares the count value K given from the counter 4 with a preset threshold value Kth, and when the count value K is smaller than the threshold value Kth (K ≦ Kth), , The motor or the like is in a disconnected state, and sends the result of the determination to the notifying means 28. In response to this, the notification means 28 notifies the determination result from the determination circuit 26 to the outside, so that it is possible to recognize that the motor or the like is disconnected.

In the above-described embodiment, positive and negative voltages are alternately applied to the motor M at the same time ratio of Tn = Tr in response to a command from the controller 16; Need not be, T
Even if the motor M is slightly rotating in the state of n <Tr or Tn> Tr, a pulse output can be obtained in the disconnection detection unit 3, so that the presence or absence of disconnection of the motor M can be detected.

In the above embodiment, each of the circuits 20 to 26 of the disconnection detecting unit 3 is constituted by hardware. However, instead of providing these circuits 20 to 26, the same microcomputer is used for the same circuit. It is also possible to achieve the function of

In this embodiment, the DC motor M
Has been described in the case of detecting the presence / absence of disconnection of a motor or the like in the motor drive device 2 including the switching circuit 10 in which the four semiconductor switching elements Q1 to Q4 for driving the motor are bridge-connected. The present invention is not limited to the configuration, and is also applicable to a case where a motor drive having a switching element, such as a motor drive using a three-phase inverter and an induction motor, detects the disconnection of a motor or the like. It is possible to do.

[0035]

According to the present invention, it is only necessary to supply a much smaller current to the motor than before, and even if the motor is substantially stopped, the presence or absence of disconnection of the motor or the like is reliably detected. be able to.

Therefore, particularly when the motor is used for running the vehicle or for steering the vehicle, it is possible to detect in advance whether or not the motor is disconnected in a stopped state where the vehicle is not running or the steering wheel is not operated. This eliminates the need for checking the presence or absence of disconnection of the motor or the like, and ensures sufficient safety.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an entire motor disconnection detection system according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining an operation for detecting the presence / absence of disconnection of a motor and its wiring system in the configuration of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a conventional motor driving device.

FIG. 4 is a timing chart for explaining a motor drive control operation in the motor drive device shown in FIG. 3;

5 is a time chart showing a temporal change of a motor current when the motor is forcibly stopped in the motor driving device shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor disconnection detection system 2 Motor drive device 3 Disconnection detection unit 10 Switching circuit 12 Drive circuit 14 Current detector 16 Controller 20 Differential arithmetic unit 22 Waveform shaping circuit 24 Counter 26 Judgment circuit 28 Notification means M Motor Q1-Q4 Semiconductor switching element

Claims (3)

[Claims] A motor control means for alternately applying positive and negative voltages to the motor at a predetermined time rate; a motor current detection means for detecting a current flowing through the motor; and a differential output of the motor current detection means. Signal converting means for converting the pulse signal converted by the signal converting means into a pulse signal; counting means for counting the number of pulses per unit time of the pulse signal converted by the signal converting means; And a determination means for determining that the motor or its wiring system is in a disconnected state when the motor is also small. 2. The motor disconnection detection system according to claim 1, wherein the motor is a DC motor for steering or running the vehicle. 3. A method in which positive and negative voltages are alternately applied to the motor at a predetermined time ratio, currents flowing through the motor are detected in response thereto, and the detected outputs are differentiated and converted into pulse signals. The number of pulses of the pulse signal per unit time is counted, and when the count value is smaller than a preset threshold value, it is determined that the motor or its wiring system is in a disconnected state. Motor disconnection detection method.