JPH0260417A - Controlling circuit for dc brake - Google Patents

Abstract

PURPOSE:To protect a controlling transistor by detecting current flowing through a brake circuit and turning the control transistor OFF upon detection of overcurrent. CONSTITUTION:Current fed from an AC power source 1 is rectified through a diode 2 and smoothed through a capacitor C1 then the smoothed current is fed to a brake solenoid L. Upon provision of a brake conduction command, a controlling transistor Q4 is turned ON through a photocoupler PC1 to feed power to the solenoid L. Current flowing through the solenoid L is detected through a resistor R41, and a transistor Q1 is turned ON upon detection of overcurrent so as to turn a photo-thyristor PT41 and a photocoupler PC41 ON thus turning a transistor Q3 OFF through a transistor Q2 and blocking power supply to the photocoupler PC1. Consequently, the controlling transistor Q4 is turned OFF and protected from breakdown.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control circuit for a DC brake used in an industrial robot, and in particular, to protect the control transistor by turning off the control transistor when the brake circuit is short-circuited. This invention relates to a control circuit for a DC brake that can be accessed.

[Conventional technology]

The mechanical parts of industrial robot devices are driven by servo motors, and these mechanical parts are in a free state when the power is turned off. Therefore, each mechanical part operates when the power is turned off.
A brake is required to fix the mechanism, and DC brakes are particularly used for such applications.

The DC brake operating circuit includes a brake circuit consisting of a DC brake solenoid and a series circuit of a control transistor that controls the energizing current of the solenoid, a command circuit that controls the control transistor to turn on and off based on an energization command,
and a control circuit that performs other controls.

Here, if an overcurrent flows through the brake circuit due to some abnormality, the brake circuit is generally disconnected from the power supply by blowing a fuse to protect components such as the solenoid.

[Problem to be solved by the invention]

However, the control transistor is extremely vulnerable to instantaneous large currents, so if a solenoid layer short circuit or a short circuit between connecting wires occurs, the control transistor will be destroyed before the fuse blows. Sometimes I put it away.

The present invention has been made in view of these points, and has an object to prevent destruction of the control transistor due to overcurrent by detecting short-circuit current in the brake circuit and turning off the control transistor in a short time. The purpose of this invention is to provide a DC brake control circuit that can perform the following functions.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a DC brake control circuit that controls a brake circuit configured by a series circuit of a DC brake solenoid and a control transistor that controls the current flowing through the solenoid. A current detection resistor is connected in series to the brake circuit, and when an overcurrent flows through the brake circuit due to a short circuit failure, a rise in the terminal voltage of the current detection resistor is detected to generate a short circuit signal, and the short circuit signal is held. A DC brake control circuit is provided, comprising: a short-circuit signal generation circuit that outputs a short-circuit signal; and a cut-off circuit that cuts off a control power source for the control transistor in response to the short-circuit signal.

[Effect]

When an overcurrent flows through the brake circuit, the terminal voltage of a current detection resistor connected in series with the brake circuit increases. The short circuit signal generation circuit detects this rise in terminal voltage, generates a short circuit signal, holds this signal, and outputs it. When the cutoff circuit receives this short circuit signal, it cuts off the control power supply of the control transistor. As a result, the control transistor is turned off. This operation occurs within a short time after the overcurrent occurs, so
Even when the solenoid is short-circuited, the control transistor can be protected from destruction due to overcurrent.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram of a DC brake control circuit according to an embodiment of the present invention. In the figure, ■ is an AC power source. 2 is a rectifying diode, CI is a smoothing capacitor, and these supply a DC voltage Va to a brake circuit composed of a solenoid and a control transistor.

L is a DC brake solenoid. Capacitor C2
The resistor R1 absorbs the back electromotive force generated when the solenoid L is cut off from the energized state. Also, barista VD
Similarly, the solenoid L is an element for absorbing the back electromotive voltage generated and protecting the control transistor from overvoltage. Q4 is a control transistor, and here a FET (field effect transistor) having a lower on-resistance than a bipolar transistor is used.

B1 and B2 are brake energization command input terminals. When the brake energization command BS is issued, the photocoupler PCI
When transistor Q3 is conductive and in normal operation, voltage control circuit 3, which will be described later, connects transistor Q3 and photocoupler P.
A voltage is supplied to the gate of the control transistor Q4 through CI and the resistor R2, the control transistor Q4 is turned on, current flows through the solenoid, and the DC brake (not shown) is released. R2 and R3 are resistors for setting the gate voltage of transistor Q4.

3 is a voltage control circuit. Diode D31, resistor R3
1. Zener diode ZD31 and capacitor C3
1 constitutes a voltage stabilizing circuit, and when the supply voltage Va of the brake circuit is equal to or higher than a predetermined voltage based on the Zener voltage of the Zener diode ZD3, the short circuit signal generating circuit 4
and supplies the stabilized DC voltage Vc to the cutoff circuit 5. A case where the supply voltage Va of the brake circuit is lower than a predetermined voltage will be described later.

4 is a short circuit signal generating circuit. R41 is a current detection resistor and is connected in series to the brake circuit. When an overcurrent flows in the brake circuit due to a layer short circuit of the solenoid L, the terminal voltage of the resistor R41 increases, and the base current flows to the transistor Q1 via the resistor R42.
Transistor Q1 turns on. PT41 is a photothyristor, and when transistor Q1 turns on,
The applied voltage VC causes current to flow through the resistor R43 to the diode on the primary side of the photothyristor PT41, turning on the thyristor on the secondary side. The photothyristor PT4 maintains this on state. Resistor R44 and capacitor C41 are photothyristor PT4
It has the function of stabilizing the operation of 1.

Terminals AO and A1 are connected to another power source (not shown). This separate power supply is shared with the power supply of other signal circuits in the robot device, and outputs a DC voltage of approximately 24V. When the thyristor of the photothyristor PT41 is turned on, current flows from this separate power supply through the resistor R45 to the diode of the photocoupler PC41, and the photocoupler PC
41 transistor is turned on. This photocoupler PC
The ON signal of 41 becomes a short circuit signal output to the cutoff circuit 5. Note that at the same time as the short circuit signal is output, a current flows to the light emitting diode LED through the resistor R46, the light emitting diode LED lights up, and a short circuit alarm is displayed externally.

5 is a cutoff circuit that cuts off the control power supply of the control transistor Q4. In addition to being operated by the ON signal of the photocoupler PC41, the cutoff circuit 5 can also operate when the supply voltage Va of the brake circuit decreases to turn off the control transistor Q4.

First, a case where the device operates due to a decrease in the supply voltage Va will be described. Supply voltage Va is Zener diode ZD
When the voltage drops below a predetermined voltage based on the Zener voltage of 31, the voltage Vc, which had been stabilized up to that point, suddenly drops. The voltage Vc is approximately the Zener diode Z of the cutoff circuit 5.
When the Zener voltage drops below the Zener voltage of D51, the transistor Q
The current flowing to the base of transistor Q2 suddenly decreases, and transistor Q2 shifts from on to off.

Here, when the transistor Q2 starts transitioning to the off state, the current flowing through the resistor R51 and the resistor R54 decreases, so the base voltage of the transistor Q3 decreases, and the transistor Q3 shifts from on to off. When transistor Q3 begins to transition to the off state, resistor R55
The base current of the transistor Q2, which was being supplied through the transistor Q2, is reduced, further promoting the turning off of the transistor Q2, and thus also the turning off of the transistor Q3. Due to such a positive feedback effect, the transistor Q3 is turned off suddenly and quickly. Therefore, the control power source of the control transistor Q4 is cut off, and the control transistor Q4 is turned off within a short time.

Next, a case will be described in which the short-circuit signal generation circuit 4 is operated by an ON signal from the photocoupler PC41. When the transistor of the photocoupler PC41 is turned on, the base of the transistor Q2 is short-circuited, so that the transistor Q2 is turned off. When transistor Q2 turns off, resistor R51
And since almost no current flows through R54, the base voltage of transistor Q3 decreases and transistor Q3
turns off. When the transistor Q3 is turned off, the control power source of the control transistor Q4 is cut off, and the control transistor Q4 is turned off. Since this operation is performed in an extremely short time, even when the solenoid is short-circuited, the control transistor can be protected from destruction due to overcurrent.

〔Effect of the invention〕

As explained above, in the present invention, even if a solenoid layer short circuit or a short circuit in the solenoid connection wire occurs, the control transistor can be turned off in a short time, so the control transistor can be reliably protected. . Furthermore, in the event of a short circuit, an alarm can be displayed externally, making maintenance and inspection work easier.

Furthermore, once the short-circuit accident is recovered, the brake circuit can continue to operate without replacing parts or performing a reset operation, which improves the operability of the robot device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a DC brake control circuit according to an embodiment of the present invention. AC power supply voltage control circuit Short circuit signal generation circuit 1 = - Cutoff circuit Solenoid control transistor Current detection resistor Photothyristor Photocoupler Light emitting diode Separate power supply connection terminal L ----------- T4 1 P C41 ------- −−−−−− ED AOlAl Patent applicant Fanasoku Co., Ltd. Agent Patent attorney Takeshi Hattori

Claims (4)

[Claims] (1) In a DC brake control circuit that controls a brake circuit configured by a series circuit of a DC brake solenoid and a control transistor that controls the current flowing through the solenoid, a current detection resistor is connected in series to the brake circuit. and a short-circuit signal generation circuit that detects a rise in terminal voltage of the current detection resistor to generate a short-circuit signal when an overcurrent flows in the brake circuit due to a short-circuit failure, and holds and outputs the short-circuit signal. A control circuit for a DC brake, comprising: a cutoff circuit that cuts off a control power source for the control transistor in response to the short circuit signal. (2) The DC brake control circuit according to claim 1, wherein the short circuit signal is held by a photothyristor. (3) The DC brake control circuit according to claim 1, wherein the output of the short circuit signal is performed by a photocoupler. (4) The DC brake control circuit according to claim 1, wherein the short circuit signal generating circuit displays an alarm on a display device at the same time as the short circuit signal is generated.