JPS623328Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electromagnetic brake protection device that releases the rotating shaft of the main engine by excitation of the excitation coil of the brake to enable the main engine to operate, and brakes the main engine by de-energizing the excitation coil.

FIG. 1 shows a conventional example of an excitation circuit for an electromagnetic brake. In the figure, 1 is an electromagnetic coil of an electromagnetic brake (not shown), 2 is an electromagnetic contactor, and 3
is a holding resistor, 4 is a discharge resistor, 5 is an electromagnetic contactor for shorting the holding resistor, and 6 is an excitation power source.
is opened and closed at the same time as the main circuit electromagnetic contactor 8 of the main motor, for example, the DC motor 7, shown in FIG. 2 is opened and closed. 9 is the main engine power supply.

In this conventional example, when a driving command is given to the DC motor 7, the electromagnetic contactors 2 and 5 are closed at the same time as the main circuit electromagnetic contactor 8 is closed, and a forced excitation current flows through the excitation coil 1 of the electromagnetic brake. , the braking by the brake is released and the DC motor 7 is started. Furthermore, after a short period of time, the electromagnetic contactor 5 opens, and a holding current begins to flow through the excitation coil 1 to maintain the released state of the brake.

For this reason, if the DC motor 7 is started and stopped frequently, the contacts of the electromagnetic contactors 2 and 5 will be damaged, the holding resistor 3, etc. will be disconnected, and the excitation power will be lost, resulting in no brake command. Despite this, the brake operation is performed. However, since no command to stop the DC motor 7 has been issued, the motor 7 will continue to operate while the brake is applied, resulting in damage to the lining and shoe of the electromagnetic brake, as well as damage to the DC motor. This had the disadvantage of causing damage to the shaft of the motor 7.

This idea was made in order to eliminate the above-mentioned drawbacks of the conventional brakes. A current relay is inserted into the excitation circuit of the electromagnetic brake to detect the actual loss of excitation power, and the main engine is activated by the operation of the current relay. It is an object of the present invention to provide an electromagnetic brake protection device that can completely prevent damage to the electromagnetic brake due to substantial loss of excitation power by having a configuration in which a drive circuit is released.

An embodiment of this invention will be described below with reference to the drawings.

In FIGS. 3 and 4, reference numeral 10 denotes a current relay inserted in series with the electromagnetic contactor 2 in the electromagnetic brake excitation circuit. 11 is a main engine drive circuit, 12 is a start push button switch, 13 is a stop push button switch,
8a and 8b are the coil and self-holding contact of the main circuit electromagnetic contactor 8, respectively, and 14a is the normally closed contact of the electromagnetic relay 14, which opens the main engine drive circuit 11 when loss of the electromagnetic brake power source is detected.

10a is a normally closed contact of the current relay 10, and a time-limiting contact 8c of the main circuit electromagnetic contactor 8 and the electromagnetic relay 14
It is connected to the control power source 15 via the power source 15, and is closed when the electromagnetic brake power source is lost. The time limit contact 8c is set to close after the current relay 10 is activated when the current flowing through the post-energization excitation circuit reaches approximately the holding current of the electromagnetic brake.

In this configuration, the starting push button switch 12
The main circuit electromagnetic contactor 8 is energized by the input of
At the same time, as in the case of the conventional example, the electromagnetic contactors 2 and 5 are closed, a forced excitation current flows through the excitation coil 1, and the normally closed contact 10a of the current relay 10 is opened. The electromagnetic brake is
It is released and the DC motor 7 starts. Time limit contact 8c
Since the circuit is closed only after the current flowing through the exciting coil 1 reaches a predetermined level and the normally closed contact 10a of the current relay 10 is opened, the main engine drive circuit 11 is not released when the DC motor 7 is started.

While the DC motor 7 is in operation, the brake power supply is lost due to a break in the electromagnetic brake excitation circuit, etc., and the current flowing into the excitation coil 1 drops below a predetermined level, even though a command to stop the DC motor 7 is not issued. Then, the normally closed contact 10a of the current relay 10 is closed. Since the time limit contact 8c is closed during operation, the electromagnetic relay 14 for detecting loss of brake power is energized, its normally closed contact 14a is opened, and the main engine drive circuit 11 is released. As a result, the electromagnetic contactor 8
is opened, and the DC motor 7 is disconnected from the power source 9 and stopped.

As described above, according to this invention, a current relay is inserted into the excitation circuit of the electromagnetic brake, and when the current flowing through the excitation coil of the electromagnetic brake becomes approximately equal to or less than the holding current, the current relay operates to release the main engine drive circuit. Because of this structure, even if there is an abnormality in the excitation circuit and the brake power is lost, the main engine is simultaneously disconnected from the power supply, which prevents the problem of the main engine continuing to operate when the electromagnetic brake is applied. This completely eliminates the risk of damage to the electromagnetic brake and even the main engine.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a conventional excitation circuit for an electromagnetic brake, Figure 2 is a diagram showing the main circuit of the main engine subjected to braking action, and Figures 3 and 4 are examples of an implementation of the electromagnetic brake protection device according to this invention. An example circuit diagram is shown, and FIG. 3 is a diagram showing an excitation circuit of an electromagnetic brake.
FIG. 4 is a diagram showing the start/stop circuit of the main engine. In the figure, 1... Excitation coil of electromagnetic brake, 7... Main engine, 8... Magnetic contactor for main circuit, 8
a... Coil of main circuit electromagnetic contactor, 8c... Time-limited contact, 10... Current relay, 10a... Normally closed contact of current relay, 11... Main engine drive circuit, 14...
. . . Electromagnetic relay, 14a . . . Normally closed contact of the electromagnetic relay. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] A current relay inserted in the excitation circuit of the electromagnetic brake, a time limit contact that closes after a predetermined time delay when the main engine drive circuit closes, and when this time limit contact is closed, the normally closed contact of the current relay closes, causing the main engine drive circuit to close. An electromagnetic brake protection device characterized by being equipped with an electromagnetic relay that releases.