JP3004690U - Overheat prevention device for DC motor - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] A cycle of stopping and restarting prevents the motor whose temperature has risen from restarting due to a temperature drop after power-off, even when the operator does not intentionally shut off the switch. Prevent system troubles caused by. [Structure] A first relay 4 for turning on / off a power source of a DC motor is provided, and an exciting coil 5 of the first relay 4 is connected to a power source via an operating switch 6 and a second relay 7, and The relay 7 of No. 2 is kept energized by the set switch 8 and kept deenergized by the thermal switch 2. The second relay 7 is provided with a suction coil 9 and a holding coil 10, is energized by energizing the suction coil 9 and the holding coil 10, and is a relay or set coil and a reset coil that are continuously energized only by energizing the holding coil 10. A latch relay is used which is provided with the energization of the set coil and continues to be deenergized by the energization of the reset coil.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a device for preventing overheating of a DC motor, and in particular for a DC motor that prevents overheating that occurs when an abnormality occurs in the DC motor when a start switch for supplying power to the DC motor is installed in a place remote from the motor. The present invention relates to an overheat prevention device.

[0002]

[Prior art]

 As shown in FIG. 4, a conventional DC motor overheat prevention device is connected to the DC motor 1 via the external relay 50 with the power supply 3, and the exciting coil 51 of the external relay 50 is installed inside the DC motor. When the temperature of the DC motor 1 connected to the power source 3 via the switch 2 and the manual switch 60 rises abnormally, the contact of the thermal switch 2 opens and the external relay 50 is deenergized to supply the current to the DC motor 1. Was interrupted. This technique was effective in preventing overheating by stopping the motor 1 when the temperature of the DC motor 1 abnormally increased due to a failure, but the manual switch 60 was separated from the motor. In this case, if the operator cannot recognize the stop when the electric motor stops, the manual switch 60 is not cut off. Therefore, when the temperature of the electric motor 1 decreases after the stop, the contact of the thermal switch 2 closes, so that the external relay 50 is energized. Then, electric power is supplied to the electric motor 1 again, so that the rotation is restarted, and then the temperature rises and the electric motor 1 is stopped, which is an unfavorable cycle.

[0003]

[Problems to be solved by the device]

The present invention has been made in view of the above circumstances, and when the temperature of the DC motor exceeds a predetermined value, the thermal switch operates to shut off the power supply and suppress the temperature rise. In the DC motor overheat prevention device, the temperature rise prevents the motor from restarting due to a temperature drop after the power is cut off, and even if the operator does not intentionally cut off the start switch, it can be stopped and restarted. It is an object of the present invention to provide a device for preventing overheating of a DC motor, which prevents system troubles caused by the above cycle.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention comprises a first relay for turning on / off a power source of a DC motor, and an exciting coil of the first relay is connected to a power source through an operating switch and a second relay. At the same time, the first feature is that the second relay is continuously energized by the set switch and continuously deenergized by the thermal switch.

Further, the second relay includes a suction coil and a holding coil, is energized by energization of the suction coil and the holding coil, and is a relay that is continuously energized only by energizing the holding coil. It has a feature.

Furthermore, the second relay is a latch relay that includes a set coil and a reset coil, and is energized by energizing the set coil and deenergized by energizing the reset coil. It is a feature of.

A fourth feature is that the thermal switch is arranged on a terminal plate that supplies power to the DC motor.

[0009]

【Example】

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

FIG. 1 is a circuit diagram of an embodiment of a DC motor overheat prevention device according to the present invention, in which a direct current motor 1 is connected from a power source 3 via a first relay 4 and a first relay 4 is connected. The exciting coil 5 is connected from the power source 3 via the second relay 7 and the operation switch 6, and the B terminal of the set switch 8 is the power source 3, the P terminal is the suction coil 9 of the second relay 7, and the H terminal. Are connected to the holding coil 10 of the second relay 7 via the thermal switch 2 provided inside the DC motor 1.

The operation of FIG. 1 will be described. When the operator operates the set switch 8 from the OFF position to the ON position, the B terminal is connected to the H terminal and a current flows from the power supply 3 to the holding coil 10 of the second relay 7 via the thermal switch 2. At this time, the thermal switch 2 adopts a so-called normally-on type in which the contact is closed because the temperature of the DC motor 1 is low. Next, when the set switch 8 is operated to the starting position, a current flows from the power source 3 to the suction coil 9 of the second relay 7 via the P terminal, so that the second relay 7 is energized. When the operator releases the set switch 8 after the second relay is energized, the set switch 8 returns to the ON position by the action of a spring (not shown) and the excitation of the suction coil 9 of the second relay 7 is lost. However, since the holding coil 10 is continuously excited, the energization of the second relay 7 is continued. When the operation switch 6 is closed, a current flows through the exciting coil 5 of the first relay 4 and is energized to supply a current from the power supply 3 to the DC motor 1 to rotate the DC motor 1.

When the operator suspends the electric motor 1, if the operation switch 6 is disconnected, the first relay 4 is deenergized, the current from the power source 3 is cut off, the DC electric motor 1 is stopped, and the operation switch 6 is restarted. When the switch is turned on, the first relay is energized again, and the DC motor 1 restarts its rotation.

When the temperature of the DC motor 1 rises to a predetermined temperature, the contact of the thermal switch 2 is opened, so that the second relay supplied from the power source 3 via the set switch 8 The second relay 7 is deenergized because the energization of the holding coil 10 of No. 7 is cut off, and as a result, the current of the exciting coil 5 of the first relay 4 is cut off and the first relay 4 is deenergized. Therefore, the current from the power supply 3 of the DC motor 1 is cut off and the DC motor 1 is stopped.

After the temperature of the DC motor 1 is gradually decreased after the stop due to the temperature rise and the contact of the thermal switch 2 is closed again, a current is supplied to the holding coil 10 of the second relay 7 via the set switch 8. Since the suction coil 9 is supplied with no current, the second relay 7 maintains the deenergized state, and the DC motor 1 is continuously stopped. Therefore, the DC motor 1 will not be restarted unless the operator intentionally operates the set switch 8 to the starting position.

Next, another embodiment of the overheat prevention device for a DC motor according to the present invention shown in FIG. 2 will be described. The DC motor 1, the power source 3, the first relay 4, the exciting coil 5, and the operation switch 6 are the same as those shown in FIG. The thermal switch 2 uses a so-called normal-off type in which the contacts are open at normal temperature. The latch relay 13 which is characteristic of this embodiment will be described. The latch relay 13 has contacts and two coils, namely a set coil 11 and a reset coil 12. When a current flows through the set coil 11, the contact is mechanically locked while being closed, so that the contact is kept closed even if the current of the set coil 11 is cut off. When a current flows through the reset coil 12 with the contact closed, the contact is opened and mechanically locked in this state, so the contact remains open even if the current in the reset coil 12 is cut off. . Therefore, each coil is energized in a pulsed state.

The operation of FIG. 2 will be described. When the operator presses the start button 14, a current flows from the power supply 3 to the set coil 11 of the latch relay 13. At this time, since the temperature of the DC motor 1 is low and the contact of the thermal switch 2 is open, the reset coil 12 is not energized. Therefore, the contacts of the latch relay 13 are closed. Even if the operator releases the start button 14, the contact of the latch relay 13 remains closed as described above. Next, when the operation switch 6 is closed, a current flows through the exciting coil 5 of the first relay 4 to be energized, the current is supplied from the power source 3 to the DC motor 1, and the DC motor 1 rotates.

When the operator temporarily stops the electric motor 1, if the operation switch 6 is disconnected, the first relay 4 is deenergized, the current from the power source 3 is cut off, the DC electric motor 1 is stopped, and the operation switch 6 is restarted. When the switch is turned on, the first relay is energized again, and the DC motor 1 restarts its rotation.

When the temperature of the DC motor 1 rises to a predetermined temperature, the contacts of the thermal switch 2 are closed, so that a current flows from the power supply 3 to the reset coil 11 of the latch relay 13, The contact is opened, and as a result, the current of the exciting coil 5 of the first relay 4 is cut off and the first relay 4 is deenergized. Therefore, the current from the power supply 3 of the DC motor 1 is cut off and the DC motor 1 is stopped.

When the temperature of the DC motor 1 is gradually decreased and the contact of the thermal switch 2 is opened again after the stop due to the temperature rise, the current to the reset coil 12 of the latch relay 13 is dropped but the latch relay 13 is contacted. The open state is maintained and the DC motor 1 continues to be stopped. Therefore, the DC motor 1 is not restarted unless the operator consciously operates the start button.

FIG. 3 shows another embodiment of mounting the thermal switch 2. In the embodiment shown in FIGS. 1 and 2, the thermal switch 2 was provided inside the DC motor 1. However, it was necessary to secure a mounting place for the thermal switch from the design stage of the DC motor, and the size and weight could be reduced. It is expected that it will become difficult to install it as required these days. In addition, there is a market demand that an overheat prevention device be installed later on the existing DC motor, and it is desired to install a thermal switch that can be added to the outside of the DC motor. In FIG. 3, the electric wire 20 shows a part of a power supply line from the power source to the DC motor, and the electric wire 20 is divided and the terminal 21 is crimped to the conductor portion. The terminal plate 40 is provided with mounting holes for the terminals 21 at both ends of a metal plate, and the terminals 21 are fixed by bolts 22, nuts 23 and the like. The thermal switch 2 is fixed by a holder 24 in the approximate center of the terminal plate 40. Then, for the insulation of the conductive portion, the whole is encapsulated with resin 25. Of course, the encapsulation is not limited to resin, and the same effect can be obtained with silicon rubber or the like.

The terminal plate 40 is a minute resistor whose cross-sectional area is predetermined depending on the current value of the DC motor, and whose temperature rises according to the heat generation of the DC motor. The thermal switch 2 indirectly detects the temperature of the DC motor by detecting the temperature of the terminal plate 40. Therefore, it is possible to provide a wide range of overheat protection device by calculating the size and cross-sectional area of the terminal plate 40 according to the output of the DC motor and considering the compatibility with the thermal switch 2. It is possible to realize an overheat protection device with the same effect as when a thermal switch is installed inside the DC motor without affecting the design of the DC motor and as an option of the existing DC motor.

[0022]

[Effect of device]

 As described above, the first feature of the present invention is provided with the first relay for turning on / off the power source of the DC motor, and the exciting coil of the first relay is connected via the operation switch and the second relay. By connecting to the power supply, the second relay is kept energized by the set switch and kept deenergized by the thermal switch, preventing the motor whose temperature has risen from restarting due to the temperature drop after the power is cut off. However, even if the operator does not intentionally cut off the start switch, it is possible to prevent system troubles due to the cycle of stop and restart.

Furthermore, the second feature, which is a second relay, includes a suction coil and a holding coil, is energized by energizing the suction coil and the holding coil, and is continuously energized only by energizing the holding coil. Therefore, during normal operation, the second relay continues to be energized by energizing only the holding coil, and the power consumption of the relay can be reduced.

Further, the third feature of the present invention is that the second relay includes a set coil and a reset coil, and the latch is energized by energizing the set coil and deenergized by energizing the reset coil. Since it is a relay, current does not flow in the exciting coil of the relay during normal operation, so the power consumption can be significantly reduced.

The fourth characteristic, the thermal switch, is distributed to the terminal plate that supplies power to the DC electric motor, so that the temperature of the electric motor can be detected without providing a thermal switch inside the electric motor. Of electric motors can be provided without modification.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a DC motor overheat prevention device according to the present invention.

FIG. 2 is a circuit diagram of another embodiment of a DC motor overheat prevention device according to the present invention.

FIG. 3 is an explanatory view of the vicinity of a terminal plate of a DC motor overheat prevention device according to the present invention.

FIG. 4 is a circuit diagram of a conventional DC motor overheat prevention device.

[Explanation of symbols]

 1 ... DC motor 2 ... Thermal switch 3 ... Power supply 4 ... First relay 5 ... Excitation coil 6 ... Actuation switch 7・ ・ ・ ・ ・ Second relay 8 ・ ・ ・ Set switch 9 ・ ・ ・ Suction coil 10 ・ ・ ・ ・ Holding coil 11 ・ ・ ・ ・ Set coil 12 ・ ・ ・ ・ ・ ・ Reset coil 13 ・ ・ ・・ Latch relay 40 ・ ・ ・ ・ Terminal plate

Claims (4)

[Scope of utility model registration request] 1. A DC motor, wherein when the temperature of the DC motor (1) exceeds a predetermined value, the thermal switch (2) is actuated to shut off the power supply (3) and suppress the temperature rise. In the overheat prevention device, a first relay (4) for turning on / off the power source of the DC motor (1) is provided, and an exciting coil (5) of the first relay (4) is connected to an operation switch (6). Power supply (3) via the second relay (7)
A device for preventing overheating of a DC motor, characterized in that the second relay (7) is continuously energized by a set switch (8) and continuously deenergized by the thermal switch (2). 2. The second relay (7) according to claim 1.
Is equipped with a suction coil (9) and a holding coil (10), is energized by energizing the suction coil (9) and the holding coil (10), and continues energizing only by energizing the holding coil (10). Overheat prevention device for a DC motor, which is a relay that can be used. 3. A reset coil (12) according to claim 1, wherein the second relay includes a set coil (11) and a reset coil (12) and is continuously energized by energizing the set coil (11). A device for preventing overheating of a DC motor, which is a latch relay (13) that is continuously deenergized by energizing the device. 4. The overheat prevention device for a DC motor according to claim 1, wherein the thermal switch (2) is arranged on a terminal plate (40) for supplying power to the DC motor.