JPH1166993A - Contact point welding detecting device of motor having brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which can cope even with accidental welding of a relay contact point by providing a contact point welding detecting device to detect welding of a contact point of a brake relay, in a motor having a brake having the brake relay to turn on and off excitation of a brake coil. SOLUTION: In order to connect a brake coil 1 to a power source R.T, a normally closed contact point 2b and a welding detecting load resistor 3 are connected in series to a relay normally opening contact point 2a. Both ends of the welding detecting load resistor 3 are connected to a welding detecting device 4. The welding detecting device 4 is composed of a full wave rectifier 7, a smoothing capacitor 10, a series connecting circuit of a resistor 8 and a light emitting diode 9 and a phototransistor 11 to receive the light of the light emitting diode 9. When a relay contact point is welded, an electric potential difference is caused between both ends of the welding detecting loading resistor 3, and this electric potential difference is rectified, and is stored in the smoothing capacitor 10, and the light emitting diode 9 emits the light, and the phototransistor 11 is electrically continued, and a relay is actuated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact detection device for a brake-equipped motor for preventing a brake-equipped motor from being brought into a dangerous state by welding a contact of a brake relay for controlling a brake coil of the brake-equipped motor. .

[0002]

2. Description of the Related Art Motors with brakes have been used in manipulators and vertical transfer machines of industrial robots because they may move due to the action of gravity in a power-off state. The brake-equipped motor keeps the brake state when the power is turned off, and it takes a little time for the control circuit of the motor to become effective even when the power is turned on. Then, only after the power supply is turned on, the control circuit of the motor with brake becomes effective and the motor with brake can be electrically controlled, and the brake coil is excited to release the brake. However, when the contacts of the brake relay are welded, when the power supply of the motor main circuit is turned on, the brake is released and a dangerous state where the brake cannot be applied is obtained. FIG. 3 shows a conventional control circuit for the brake coil. In the figure, 31 is a brake coil, 32 is a contact of a motor main circuit electromagnetic contactor, and 33 is a contact of a brake relay. Now, when a main circuit switch of a motor with a brake (not shown) is turned on, the contact 32
Closes. However, since the brake relay contact 33 connected in series with the contact 32 is in the open state, the brake coil 31 is not yet energized and the brake is held. On the other hand, when the main circuit is switched on, electric power is supplied to the motor, the motor control circuit is activated, and the motor can be electrically controlled only when the brake relay contact 33 is closed and the brake coil 31 is attached. The brakes are released. If the contact 33 of the brake relay is welded, the contact 32 associated therewith is closed when the main circuit of the motor is turned on, and at the same time, the brake coil 31 is energized and the brake is released. Before it becomes effective, the manipulators and the like of the industrial robot have disadvantages such as moving by gravity. In addition, since the brake coil of a motor with a brake is generally DC-excited, the contacts of the brake relay are turned on and off while DC voltage is applied to the brake coil 31, so that the contacts of the brake relay are more welded. It was easy. Conventionally, therefore, measures such as adopting a brake relay with a sufficiently large current capacity to make welding less likely, and estimating the life of the brake relay and replacing the brake relay before contact welding occurs, etc. Was taking.

[0003]

However, such conventional measures are costly and time-consuming, and cannot cope with accidental contact welding. That is, whether or not the contacts of the brake relay are welded largely depends on the use situation, the use frequency, and the like, and it is very difficult to uniformly estimate the replacement time. Therefore, assuming the worst case, it was necessary to select a relay having a large capacity with a considerably high safety factor, or to replace the relay early. However, no matter how high the safety factor is, or how frequently the relay is replaced, accidental welding of the relay contacts cannot be prevented, and it is impossible to cope with accidental welding. Accordingly, an object of the present invention is to provide a contact welding detection device capable of coping with accidental welding of a relay contact.

[0004]

According to the first aspect of the present invention, a contact of the brake relay is welded to a brake-equipped motor having a brake relay for turning on and off the excitation of a brake coil. A welding detection device for detecting the According to the invention described in claim 2, in the contact welding detection device for the brake-equipped motor, the contact welding detection device is connected to a power supply via a normally open contact and a normally closed contact of the brake relay, When the charging voltage charged by the power supply voltage exceeds a predetermined value, a welding detection signal is output. According to the third aspect of the present invention, in the contact welding detection device for the brake-equipped motor, the brake is not released by a welding detection signal of the contact welding detection device, According to the invention described in claim 4, in the contact welding detection device for the brake-equipped motor, power is not supplied to the main circuit of the brake-equipped motor by the welding detection signal of the welding detection device. Things.

[0005]

FIG. 1 is a connection circuit diagram of a relay contact welding detecting device according to an embodiment of the present invention. In the drawing, 1 is a brake coil, 6d and 6e are normally open contacts of a motor main circuit electromagnetic contactor, 2a and 2b are contacts of a brake relay (not shown), 2a is a normally open contact, and 2b is a normally closed contact. . A normally closed contact 2b and a welding detection load resistor 3 are connected in series with a relay normally open contact 2a for connecting the brake coil 1 to the power supply R / T. A welding detection device 4 is connected to both ends of the welding detection load resistor 3.
One specific embodiment of the welding detection device 4 is shown within a dashed line. That is, the welding detection device 4 includes the full-wave rectifier 7
A smoothing capacitor 10 for smoothing the output, a series connection circuit of a resistor 8 and a light emitting diode 9 connected to both ends of the smoothing capacitor 10, and a light emitting diode 9
And a phototransistor 11 that receives the light. The voltage at both ends of the welding detection load resistor 3 is applied to the input side of the full-wave rectifier 7, and both ends of the phototransistor 11 are connected in parallel to the self-holding normally open contact 5 a of the relay contact welding detection signal output relay 5. I have. The relay contact welding detection signal output relay 5 includes a normally open contact 5a and a normally closed contact 5b.
(FIG. 2). Now the relay contact 2a is normal,
When the motor is not rotating (that is, when the relay contact 2a is open), no potential difference occurs between both ends of the welding detection load resistor 3, so that the light emitting diode 9 does not emit light and the phototransistor 11 is also in a non-conductive state. No current flows through the relay contact welding detection signal output relay 5. However, when welding of the relay contact 2a occurs, a potential difference occurs at both ends of the welding detection load resistor 3, and this potential difference is rectified and stored in the smoothing capacitor 10, and the light emitting diode 9 is turned on by the voltage across the smoothing capacitor 10. The light is emitted, and the light causes the phototransistor 11 to conduct, so that the relay contact welding detection signal output relay 5 is operated. Then, the relay contact welding detection signal output relay 5 becomes a self-holding normally open contact 5.
a is closed and the welding detection signal is continuously output. The release of the brake and the operation of the motor may be prohibited by the welding detection signal as described later, and the operator may be notified by sounding an alarm buzzer or blinking an alarm lamp. Also, when the relay contact 2a is normal and the motor rotates (that is, the relay contact 2a is closed), the potential difference does not occur at both ends of the welding detection load resistor 3 because the relay contact 2b is open, Therefore, the light emitting diode 9
Does not emit light, the phototransistor 11 is also non-conductive, and no current flows through the relay contact welding detection signal output relay 5. Therefore, there is no prohibition of brake release and motor operation. Further, even if welding of the relay contact 2a occurs during rotation of the motor, the motor control circuit is effective, so that there is no problem even if the welding detection device 4 is not working. When the motor stops and the relay contact 2b is closed, the welding detection device 4 outputs a welding detection signal to prohibit brake release and motor operation.

[Second Embodiment] FIG. 2 shows a specific example of using a welding detection device 4 to prevent the motor from being turned on. The stator winding 14 of the motor 12 with brake is
The power sources R, S, and T are turned on and off by the contacts 6a, 6b, and 6c of the motor main circuit electromagnetic contactor. The rotor 15 is provided with an electromagnetic brake 16 coaxially. The electromagnetic brake is applied when the motor is not operated. During the operation of the motor, the brake coil 13 of the electromagnetic brake 16 is excited to release the brake. Excitation of the brake coil 13 is established by closing the contacts 6d and 6e and the closing of the relay contact 2a which interlock with the motor main circuit electromagnetic contactor. here,
A series circuit of a relay contact 2b (normally closed) and a welding detection load resistor 3 is connected between the relay contact 2a and the power supply, and the above-described welding detection device 4 is provided at both ends of the welding detection load resistor 3. As described above, when welding occurs at the relay contact 2a, the relay contact welding detection signal output relay 5 is operated as described above. When the relay contact welding detection signal output relay 5 operates, the self-holding normally open contact 5a
Is closed, and the emergency stop circuit 1 in the controller 17 is closed.
9, the normally closed contact 5b is opened. Normally closed contact 5b
Is opened, the emergency stop circuit 19 operates, and when the emergency stop circuit 19 operates, power is not supplied to the circuit of the motor main circuit electromagnetic contactor 6 and the circuit of the brake relay 2. Therefore, the contacts 6d and 6e are opened, and the power is not connected to the motor. The normally open contact 2a of the brake relay 2
, And the brake coil 13 is in a non-excited state. As described above, when the contact welding detection signal of the relay contact is output, the relay contact welding detection signal output relay 5 operates, and the brake release and the operation of the motor are prohibited by this operation. When the relay contact 2a is in a normal state, the relay contact 2a is open when the motor is not rotating, and the relay contact 2b is open when the motor is rotating. In any case, the relay contact welding detection signal output relay 5 does not operate and is normally closed. Contact 5b
Is closed. When the normally closed contact 5b is closed, the emergency stop circuit in the controller 17 is not operated. Now, when the motor start switch 20 is turned on, a current flows through the motor main circuit electromagnetic contactor 6, and its contacts 6a, 6b, 6c are closed, and the operation of the motor is permitted. Also, the contact 6d ・ 6
e is also closed, but since the relay contact 2a is open, no current flows through the brake coil 13 and the brake is not released yet. Eventually, when the operation of the motor is permitted and the control circuit of the motor becomes effective, the controller 17 energizes the brake relay 2 and closes the normally open contact 2a and opens the normally closed contact 2b. The brake is released and the operation of the welding detection device 4 ends. As another embodiment, by reading the output relay contact 5a of the brake relay contact welding signal as an input signal of the controller 17, it is possible to perform an alarm process in the controller 17 and prohibit the operation after turning on the power supply of the motor main circuit. It is possible.

[0007]

As described above, according to the present invention, since the relay contact and the welding detection load resistor are connected in series and connected to the power supply, if this normally open contact When welding, a current also flows through the welding detection load resistor connected in series with this, causing a potential difference between both ends of this resistor,
Since this potential difference is detected by the welding detection device and the relay contact welding detection signal output relay is operated, the brake release and the operation of the motor are prohibited. Further, if an alarm buzzer or an alarm lamp is operated, the welding of the relay contact can be notified to the operator before turning on the motor power. Therefore, it is only necessary to replace the relay each time the contacts are welded, which not only makes maintenance easier, but also detects welding of the relay contacts before turning on the motor power. The effect that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a connection circuit diagram of a relay contact welding detection device according to an embodiment of the present invention.

FIG. 2 shows a specific example in which the welding detection device 4 of the present invention is used to prevent a brake-equipped motor from being turned on.

FIG. 3 is a control circuit diagram of a brake coil of a conventional motor with a brake.

[Explanation of symbols]

 1, 13, 31 Brake coil 2 Brake relay 2a, 2b, 33 Relay contact 3 Welding detection load resistor 4 Welding detection device 5 Relay contact welding detection signal output relay 5a, 5b contact 6 Motor main circuit electromagnetic contactor 6a, 6b , 6c, 6d, 6e, 32 contacts 7 full-wave rectifier 8 resistor 9 light-emitting diode 10 smoothing capacitor 11 phototransistor 12 motor with brake 14 stator winding 15 rotor 16 electromagnetic brake 17 controller 19 emergency stop circuit 20 motor start switch

Claims (4)

[Claims] 1. A welding detection device for detecting welding of a contact point of a brake relay provided on a brake-equipped motor provided with a brake relay for turning on and off the excitation of a brake coil. apparatus. 2. The contact welding detection device for a motor with a brake, wherein the contact welding detection device is connected to a power supply via a normally open contact and a normally closed contact of the brake relay, and is charged by a power supply voltage. 2. The contact welding detection device for a motor with a brake according to claim 1, wherein a welding detection signal is output when the voltage exceeds a predetermined value. 3. The contact of a brake-equipped motor according to claim 1, wherein the brake is not released by a welding detection signal of the contact-welding detection device. Welding detector. 4. The contact welding detection device for a motor with a brake, wherein power is not supplied to a main circuit of the motor with a brake by a welding detection signal of the welding detection device. 5. The contact welding detection device for a motor with a brake according to claim 1.