JPH04265681A - Brake failure detecting method - Google Patents

Abstract

PURPOSE:To detect brake failure without requiring hardware by detecting the difference of currents to be fed to a motor, respectively, at the time of brake operation and nonbrake operation. CONSTITUTION:Under a state where a motor 21 is stopping and a working coil 25 of a brake shoe 24 is conducting or nonconducting, current to be fed to the motor 21 is increased gradually and a current at the time of starting rotation of the motor 21 is detected through a current detector 31. Difference of rotation starting currents at the time of conducting and nonconducting of the working coil 25 is then calculated and if thus calculated difference is lower than a set value, a decision is made than the brake is faulty.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake failure detection method, and more particularly to a brake failure detection method for braking a drive body driven by a motor.

0002

[Prior Art] As a conventional brake, a friction brake is known in which, for example, a disc is connected to a driving body and a brake shoe is pressed against the disc to brake the driving body by friction. Widely used in industrial machinery, etc. In such a friction brake, for example, the brake shoes are driven by an actuating coil, and the drive of the brake shoes is controlled by switching between energization and de-energization of the actuating coil, that is, by a control circuit including the actuating coil. What has been done is known.

[0003] On the other hand, in brakes, there are brake systems that enable brake failure detection in order to prevent accidents, etc., and these systems incorporate, for example, a failure detection circuit composed of hardware into the above-mentioned control circuit. Brake failure is detected by this failure detection circuit, and such a failure detection circuit is shown in FIGS. 3 and 4. Note that FIG. 3 shows a circuit for detecting a failure when the brake is applied, and FIG. 4 shows a circuit for detecting a failure when the brake is not applied.

In FIG. 3, an actuating coil 1 drives a brake shoe (not shown), and energization/de-energization of the actuating coil 1 is controlled by turning a transistor 2 on or off. A resistor 3 is provided between the operating coil 1 and the collector electrode of the transistor 2, both ends of the resistor 3 are connected to the input terminal of a differential amplifier 4, and the output terminal of the differential amplifier 4 is connected to a determination circuit 5. It is connected. The determination circuit 5 detects whether or not the operating coil 1 is open based on the output of the differential amplifier 4, that is, whether or not the operating coil 1 is disconnected.

Specifically, if the operating coil 1 is not disconnected, when the transistor 2 is turned on, the voltage V across the resistor 3 becomes V1, and the differential amplifier 4 outputs a predetermined value corresponding to V1. . On the other hand, if the operating coil 1 is disconnected, when the transistor 2 is turned on, the voltage V across the resistor 3 becomes zero, and the output of the differential amplifier 4 becomes almost zero. Therefore, the determination circuit 5 can determine whether or not the actuating coil 1 is disconnected by comparing the output value of the differential amplifier 4 with a preset reference value.

In FIG. 4, an actuating coil 6 and a transistor 7 have the same functions as the above-mentioned actuating coil 1 and transistor 2. Resistor 8 in parallel with actuating coil 6
is connected, and a resistor 9 is connected in series with the actuating coil 6 and the resistor 8.
is connected. The resistance value of the actuating coil 6 is R, and the resistance value is 8.
When the resistance value of the resistor 9 is R2 and the resistance value of the resistor 9 is R3, R≫R2, R3. The potential Vo between the resistor 8 and the resistor 9 is input to a determination circuit 10, and the determination circuit 10 detects whether or not the operating coil 6 is disconnected based on the potential Vo.

Specifically, if the operating coil 6 is not disconnected, when the transistor 7 is turned off, the determination circuit 10
The potential Vo input to is Vo =VSS. On the other hand, if the operating coil 6 is disconnected, the potential Vo input to the determination circuit 10 becomes Vo = VSS (R3 / (R2 + R3)) when the transistor 7 is turned off. Therefore, the determination circuit 10 can determine whether or not the actuating coil 6 is disconnected by comparing the potential Vo with a preset reference value.

[0008] Note that the determination in the above-mentioned determination circuits 5 and 10 may be performed by software instead of hardware.

[0009]

[Problems to be Solved by the Invention] However, in such conventional brake failure detection, brake failure is detected by a failure detection circuit as shown in FIGS. 3 and 4 incorporated in the brake control circuit. Therefore, when a plurality of motors are driven by one control circuit, there is a problem in that the hardware increases and the cost increases.

[0010] Accordingly, the present invention provides, in a case where a driving body that is braked by a brake, is driven by a motor, the electric current supplied to the motor is gradually increased when the brake is applied and when the brake is not applied, and when the motor starts rotating. By detecting the current value of and comparing the difference between these detected current values with the set value corresponding to the brake torque, it is possible to detect brake failure without using hardware such as a dedicated circuit for detecting brake failure. The challenge is to reduce costs.

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a failure detection method for a brake that brakes a driving body driven by a motor by energizing or de-energizing an operating coil. The first step is to detect the current value when the motor starts rotating while gradually increasing the current supplied to the motor while the motor is stopped and the working coil is de-energized or de-energized; a second step of detecting a current value at the start of rotation of the motor while gradually increasing the current supplied to the motor in an energized state;
The detected current value at the start of motor rotation in the process and the second
The present invention is characterized in that it includes a third step of comparing the difference in the detected current value at the start of rotation of the motor in the step with a set value corresponding to the brake torque.

0012

[Operation] In the present invention, in the first step, the current value at the start of rotation of the motor is detected when the motor is stopped and the operating coil is in a de-energized or energized state, and in the second step, the motor is stopped and the operating coil is detected. The current value at the start of rotation of the motor in the energized or de-energized state is detected, and in the third step, the difference between the detected current value in the first step and the detected current value in the second step corresponds to the brake torque. Compare with set value. Therefore, in the third step, the first
When the difference between the detected current values in the second step and the second step becomes larger than the set value, a brake failure is detected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings. 1 and 2 are diagrams showing an embodiment of a brake device to which a brake failure detection method according to the present invention is applied. First, the configuration will be explained.

In FIG. 1, reference numeral 21 denotes a motor that drives a drive body 22, and the drive body 22 is braked by pressing a pair of brake shoes 24 against a brake disc 23 connected to the drive shaft of the motor 21. The brake shoe 24 is pressed against the brake disc 23 by energizing the actuating coil 25. Conversely, if the operating coil is de-energized, the brake shoe 2
4 may be pressed against the brake disc 23.

A voltage can be applied to the actuating coil 25 from a power source 26, and the application of this voltage is turned on and off by a brake switch 27. The motor 21 has a DC power supply 2
The current supplied to the motor 21 can be slightly increased or decreased by the controller 29, and can be turned on/off by the motor switch 30. Also, motor 2
1 is detected by a current detector 31,
The rotational position and torque of the motor 21 are detected by a rotational position detector 32 and a torque detector 33, respectively. The brake switch 27, controller 29, motor switch 30, current detector 31, rotational position detector 32, and torque detector 33 are connected to a control section 34 consisting of a microcomputer, etc., and the control section 3 is controlled by sending and receiving signals.
4 operates these and controls the driving of the driving body 22 and the braking. The control unit 34 also includes an RO (not shown)
A brake failure is detected by executing a program stored in an M (Read Only Memory) or the like and following the procedure shown in FIG. 2 and described later.

Next, the brake failure detection procedure of this embodiment will be explained with reference to the flowchart shown in FIG. In addition,
S1 to S21 in FIG. 2 indicate each step of the flowchart. In S1, the brake switch 27 is turned off to release the brake while the motor is stopped, and in S2, the controller 29 is operated to slightly increase the current supplied to the motor 21. In S3, the current value supplied to the motor 21 is read from the current detector 31, and in S4, the rotational position of the motor 21 is read from the rotational position detector 32. In S5,
Determine whether |detected current value| > IL1 (where IL1 is a preset overcurrent reference value), and then
>IL1, that is, if an overcurrent flows through the motor 21, the process advances to S6, and a failure determination is made due to brake seizure.

On the other hand, if |detected current value|>IL1, the process advances to S7 and it is determined whether the rotational position of the motor 21 has changed. If the rotational position has not changed, the process returns to S2, and if it has changed, the process proceeds to S8. In S8, motor 21
The current value supplied to the motor, that is, the current value I1 at the start of motor rotation, is read from the current detector 31, and in S9, the motor switch 30 is turned off to stop the motor 21. In S10, the brake switch 27 is turned on to operate the brake, and in S11, the motor switch 30 is turned on and the controller 29 is activated to slightly increase the current supplied to the motor 21. In S12, the current value supplied to the motor 21 is read from the current detector 31, and in S13, the rotational position of the motor 21 is read from the rotational position detector 32.

[0018] In S14, it is determined whether |detected current value|>IL2 (however, IL2 is a preset overcurrent reference value).
If |detected current value|>IL2, that is,
If an overcurrent flows through the motor 21, the process proceeds to S15, where it is determined that the failure is due to brake seizure. On the other hand, if |detected current value|>IL2, the process advances to S16 and the motor 21
Determine whether the rotational position of has changed. If the rotational position has not changed, return to S11; if it has changed, return to S11.
Proceed to step 17. In S17, the current value supplied to the motor 21, that is, the current value I2 at the start of motor rotation, is read from the current detector 31, and in S18, the motor switch 30 is turned off to stop the motor 21.

In S19, the difference between I1 and I2, that is,
Compare the difference between the motor starting current I1 with the brake released and the motor starting current I2 with the brake applied with a set value corresponding to the brake torque, specifically,
It is determined whether |I1-I2|>IS. However, IS
is a threshold, and is set to be smaller than the value corresponding to the brake torque, taking into account errors and the like. If |I1-I2|>IS, the process advances to S20 and it is determined that the brake is normal. On the other hand, |I1-I2|>
If it is not IS, the process proceeds to S21, where it is determined that the brake has failed due to disconnection of the actuating coil 25 or that the brake shoe 24 needs to be replaced. Specifically, when the brake is normal, |I1-I2| becomes a value almost equivalent to the brake torque, which is larger than IS, and the working coil 2
5 is disconnected, the difference between I1 and I2 will be almost zero, and even if the brake shoe 24 is worn and the brake torque is drastically reduced, the difference between I1 and I2 will be almost zero. The above-mentioned determination can be made in S20 and S21.

As described above, in this embodiment, in S1 to S3 and S5, the current supplied to the motor 21 is gradually increased with the motor 21 stopped and the brake released, and the detected current value and the overcurrent reference are adjusted. On the other hand, in S9 to S12 and S14, the current supplied to the motor 21 is gradually increased with the motor 21 stopped and the actuating coil 25 energized, and the detected current value is compared with IL2. Since the current values are compared, the respective detected current values are IL1 and IL1.
When it becomes larger than 2, it can be detected as a mechanical failure of the brake due to seizure between the brake shoe 24 and the brake disc 23. Also, S
4. In S7 and S8, the current value I1 at the start of rotation of the motor 21 is detected, in S13, S16 and S17, the current value I2 at the start of rotation of the motor 21 is detected, and in S19,
|I1-I2| is compared in size with the IS set corresponding to the brake torque equivalent value, so |I1-I2
When | becomes larger than IS, it can be detected that a failure due to disconnection of the actuating coil 25 has occurred and that it is time to replace the brake shoe 24. In addition, the brake failure detection described above can be performed using the existing configuration of the brake device.
That is, the brake switch 27, the controller 29,
This can be achieved on program software using the motor switch 30, current detector 31, rotational position detector 32, control unit 34, etc., making hardware such as a dedicated circuit for brake failure detection unnecessary. It is possible to reduce costs.

Although this embodiment has been described with reference to the case where the brake is actuated by energizing the actuating coil 25, conversely, when the brake is actuated by de-energizing the actuating coil 25, the brake switch 27 can also be operated. It goes without saying that the same effects as in this embodiment can be obtained simply by reversing the on/off operation.

[0022]

According to the present invention, in the first to third steps, the current value at the start of rotation of the motor is detected while gradually increasing the current supplied to the motor during braking and non-braking, Since the difference between these detected current values is compared with a set value corresponding to brake torque, brake failures can be detected without using hardware such as a dedicated circuit for detecting brake failures, reducing costs. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a brake device to which a brake failure detection method according to the present invention is applied.

FIG. 2 is a flowchart showing an example of a detection procedure of a brake failure detection method according to the present invention.

FIG. 3 is a circuit diagram showing a conventional brake failure detection circuit.

FIG. 4 is a circuit diagram showing another conventional brake failure detection circuit.

[Explanation of symbols]

21 Motor 22 Driving body 23 Brake disc 24 Brake shoe 25 Working coil 27 Brake switch 29 Controller 30 Motor switch 31 Current detector 32 Rotational position detector 34 Control section

Claims (1)

[Claims] Claim 1: A brake failure detection method for braking a driving body driven by a motor by energizing or de-energizing an operating coil, the method comprising: The first step is to detect the current value at the start of motor rotation while gradually increasing the current supplied to the motor.The first step is to detect the current value at the start of motor rotation while gradually increasing the current supplied to the motor. a second step of detecting a current value at the start of rotation;
A third step of comparing the difference between the detected current value at the time when the motor starts rotating in the first step and the detected current value when the motor starts rotating in the second step with a set value corresponding to the brake torque. A brake failure detection method characterized by: