JPH01158237A - Control circuit of direct current brake - Google Patents

Abstract

PURPOSE:To surely carry out current control, when an electromagnetic brake of a robot or the like is controlled, by lowering the voltage between the emitter and collector of an electrification-control transistor, and by controlling the electrification command current by an electric-field-effect transistor. CONSTITUTION:When a transistor driving command 1c is given to a photocoupler 60, a phototransistor 66 is energized to pass an electrification command current to FET 7, and a transistor 5 is energized to electrify a brake coil 35, so that a magnetic force is applied to an armature disk 33 against a spring 34 to separate from a brake disk 32. In this case, even if such a transistor that has a rated voltage comparatively near to the bipolar transistor 5 is used, the current amplification factor in the electrification control circuit 50 including the FET 7 is improved, and even if the brake current is increased, the current can be controlled without complicating the circuit 50. Further, since the base current to the transistor 5 is sufficiently supplied by the FET 7, the voltage between the emitter and the collector can be reduced, thus heat generation can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control circuit for a DC brake used in an industrial robot.

(Prior art) In industrial robot equipment, etc., a DC brake as shown in Figure 2 is usually used in the mechanism that drives heavy objects in the vertical direction against the force of gravity to prevent them from falling. Ru.

The DC brake device 3 in FIG. 2 includes a brake housing 31 fixed to the robot frame 1, a brake disc 32 fixed to the feed screw 2, an armature disc 33 disposed opposite to the brake disc 32, and a brake disc 32 fixed to the feed screw 2. A spring member 34 that normally acts to press the armature disk 33 to the brake disk 32, a brake coil 35 that acts to separate the armature disk 33 from the brake disk 32, and a brake coil 35 that acts to separate the armature disk 33 from the brake disk 32. an armature steady rest 3 that holds the surrounding yoke 36 and the armature disk 33 within the brake housing 31;
It consists of

That is, while a predetermined current is not being applied to the brake coil 35, the armature disk 33 is pressed against the brake disk 32 by the spring member 34, and the feed screw 2 is thereby fixed to the robot frame 1.

On the other hand, when the brake coil 35 is energized, the yaw 36
A magnetic force acts between the armature disk 33 and the armature disk 3
3 is pulled away from the brake disc 32, and the brake action is released. This allows the feed screw 2 to rotate freely.

FIG. 3 shows a DC brake control circuit for controlling such a brake device. A brake coil 35 of a DC brake and a current supply control transistor 5 are connected in series to both ends of the DC power supply circuit 4 , and a base electrode of the transistor 5 is connected to an output terminal of a transistor drive circuit 6 .

Note that the back electromotive force suppression circuit 7 connected in parallel with the brake coil 35 uses, for example, a series circuit of a resistor and a capacitor.

(Problems to be Solved by the Invention) With regard to such conventional DC brake control circuits, the following problems have arisen as it has recently become necessary to make the brakes larger. In the conventional DC brake control circuit, when the current flowing through the brake coil 35 is increased to cope with the increase in brake size, the transistor 5 that controls the current generates a large amount of heat corresponding to the increased current. In order to solve this problem, large heat dissipation fins have become necessary.

The present invention has been made in view of the above points, and even when multiple brakes are required or the load is large, the current flow can be reliably maintained without increasing the voltage between the emitter and collector when the energization control transistor is turned on. The purpose of this invention is to provide a control circuit for a DC brake that can be controlled.

(Means for Solving Problems) According to the present invention, a series circuit of an electromagnetic brake solenoid and a transistor for controlling energization of the solenoid is connected to a DC power source, and the current to the solenoid is controlled by the transistor for controlling energization. A control circuit for a DC brake that controls to activate or release the electromagnetic brake includes an energization control means configured by connecting a field effect transistor in a Darlington configuration to drive the energization control transistor; It is possible to provide a control circuit for a DC brake, characterized in that the control circuit includes command means for supplying a control command for the electromagnetic brake to the means.

(Function) In the DC brake control circuit of the present invention, when controlling the electromagnetic brake of a robot, etc., the emitter-collector voltage of the energization control transistor is lowered, and the energization command current is amplified by the field effect transistor. , it is possible to control the solenoid current.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the DC brake control circuit of the present invention, in which a brake coil 35 used as an electromagnetic brake solenoid is connected in series with an energization control circuit 5° including a energization control transistor 5. It is connected. This series circuit is connected between the output terminals of a diode bridge 41 constituting the DC power supply 4, and is also connected to the energization and control circuit 5o.
A transistor drive circuit 6 is connected to supply a brake control command. The DC power supply circuit 4 includes an AC power supply 42
A diode bridge 41 performs full-wave rectification on the alternating current voltage waveform, and a smoothed output is supplied to the transistor drive circuit 6 by a smoothing capacitor 43 .

The energization control circuit 50 includes a field effect transistor (hereinafter referred to as F) between the collector and base of the energization control transistor 5.
The FET 7 is configured as a Darlington circuit in which the drain and source terminals of the FET 7 are directly connected, and a control command is supplied from the transistor drive circuit 6 to the gate of the FET 7. The source side of the FET 7 is grounded via a source resistor 71, and a varistor 8 is connected between the emitter and collector of the bipolar transistor 5 whose emitter is grounded.
is connected, and its voltage is limited by the energizing voltage of the varistor 8 even when the current is cut off.

Further, in the transistor drive circuit 6, a photocoupler 60
is connected to the positive output side of the diode bridge 41 of the DC power supply circuit 4 via a diode 61 and a resistor 62, and connected to the negative output side via a parallel circuit of a Zener diode 63 and a capacitor 64. The transistor drive command Ic is supplied to a photodiode 65 constituting the photocoupler 60, and a phototransistor 66 that is insulated and driven by the photodiode 65 is connected to a resistor 6.
The signal current is output to the gate of the FET 7 through the FET 7. A resistor 68 is connected to the gate of the FET 7 and is also connected to the negative output side of the diode bridge 41.

Note that, if necessary, a noise prevention circuit 9 in which a capacitor 91 and a resistor 92 are connected in series is provided in parallel with the brake coil 35.

Next, the circuit operation of the above embodiment will be explained.

When the transistor drive command 1c is supplied to the photodiode of the photocoupler, the phototransistor becomes conductive.
An energization command current is supplied to the gate of FET7. As a result, the transistor 5 becomes conductive and current flows through the brake coil 35, causing a magnetic force to act on the armature disk 33 against the spring member 34 shown in FIG. 2, thereby pulling it away from the brake disk 32.

At that time, even if a bipolar transistor 5 having a relatively low rated voltage is used, the current flowing through the brake coil 35 increases because the current amplification factor in the energization control circuit 50 including the FET 7 is improved. Even though
Current can be controlled without complicating the configuration of the energization control circuit 50. Also, the base current to transistor 5 is FE
Since the voltage can be sufficiently supplied by T7, the voltage between the emitter and collector of the energization control transistor can be reduced, and there is no need to increase the size of a fin device for dissipating heat generation.

When the supply of transistor drive command Ic is stopped, FE
The current supply from the transistor 5 to the base of the energization control transistor 5 is stopped, and its collector-emitter voltage increases. At this time, a counter electromotive force is generated in the brake coil 35, but it is clamped by the conduction voltage of the varistor 8. In other words, when the energization command current is cut off, the brake coil 35
The current flowing through the transistor 5 is quickly cut off by the transistor 5 within a short period of time.

Although the present invention has been described in some detail with respect to its most preferred embodiment, the description of the preferred embodiment may include variations in the detailed structure and contrary to the spirit of the invention as set forth in the claims. It is clear that various modifications or combinations thereof may be made.

(Effects of the Invention) As explained above, according to the present invention, even when the brake current of the electromagnetic brake solenoid increases, the current can be reliably maintained without increasing the emitter-collector voltage when the energization control transistor is turned on. It is possible to provide a control circuit for DC brakes that can be controlled.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a DC brake for an industrial robot, and Fig. 3 is a block diagram showing a conventional DC brake control circuit. It is. 1...Robot frame, 2...Feed screw, 3...
・DC brake, 4...DC power supply circuit, 5...Electrification control transistor, 6...Transistor drive circuit,
7...FET. Patent applicant: Representative of FANUC Co., Ltd. Patent attorney: Minoru Tsuji Second cause, Figure 3

Claims (1)

[Claims] A DC brake in which a series circuit of an electromagnetic brake solenoid and a transistor for controlling energization of the solenoid is connected to a DC power source, and the current to the solenoid is controlled by the transistor for controlling energization to activate or release the electromagnetic brake. The control circuit includes energization control means configured by connecting a field effect transistor in a Darlington configuration to drive the energization control transistor, and command means for supplying a control command for the electromagnetic brake to the energization control means. A DC brake control circuit characterized by: