JPH03230440A - Overload protecting device - Google Patents

Abstract

PURPOSE:To obtain a smooth restart after a start miss by providing a ring- shaped insulating plate at the opening section of a case so that a bimetal is brought into contact with the insulating plate to close it when operated. CONSTITUTION:A ring-shaped insulating plate 9 is fitted at the opening section of a case 2 and coupled with a groove 11. A gap is formed between a bimetal 5 and the insulating plate 9 when an overload protecting relay 1 is not operated, the periphery of the bimetal 5 is brought into contact with the insulating plate 9 to close the opening section of the case 2. When the bimetal 5 is not operated, the temperature of a casing 10 is easily detected because the case 2 is opened, and the operation characteristic of the bimetal 5 is improved. When the bimetal 5 is operated, the opening section is closed, if the temperature of the casing 10 is low, the heat of a heater 6 is hardly absorbed by the casing 10, and the operation of the bimetal 5 is improved. The protection performance of the protecting device 1 is improved, and a smooth restart can be performed after a start miss.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an overload protection device used to protect an electric motor, electric compressor, etc. during overload.

(B) Conventional technology In general, this type of overload protection device consists of a bottomed case with one end open, and contacts that are placed inside the case and open and close by reversing in response to temperature changes. It consists of a bimetal, a heater that heats the bimetal, and a terminal plate that is electrically connected to the heater and the bimetal and extends outside the case, and by connecting the bimetal in series to a common winding of a compressor or the like. When the compressor is locked or operating under overload, the compressor's heat or self-heating shuts off the circuit to protect the motor. (Jitsukai 58-818
(C) Problems to be Solved by the Invention According to the above-mentioned configuration, one end surface of the casing, which is the load side of a compressor, etc., is open, so when it is attached to a compressor,
When the load casing temperature is high, it is easier to detect the load temperature and the operating characteristics of the bimetal improve, so protection performance can be improved. On the other hand, when the load casing temperature is low, the heat from the bimetal and the heat is absorbed by the casing. Sisters,
Not only will the bimetal's operation be delayed and its protective performance deteriorate, but the recovery time after operation will be shortened, and the load on the compressor, etc. will remain in an abnormal state for a long period of time, increasing the risk of motor burnout. There was the problem of inviting.

In addition, in recent years, PTC relays (non-contact relays using positive temperature coefficient thermistor elements), which are most commonly used as starting relays for refrigerator compressors, etc., have an initial resistance of several Ω when energized, but increase to several Ω. The temperature of the element increases from 170 to 18
Although the temperature is as high as 0° C., if a -variable compressor makes a startup error, it will take time for the elements to return to below the Curie temperature in order to restart. Here, if the recovery time of operation 12 or the overload protection device is shorter than the recovery time of the PTC relay due to the above-mentioned startup error, the PTC relay will reach the Curie temperature and cannot become lower than I, so the overload protection device will operate again. There is a problem in that repeating these operations many times causes a rise in temperature inside the compressor and damages the product.

The present invention has been made in view of the above, and is designed to prevent the heat of the heater from being absorbed into the casing when the casing temperature of the load is low, thereby ensuring good operation of the bimetal, improving protection performance, and improving the protection performance after operation. By increasing the recovery time of
It is an object of the present invention to provide an overload protection device that can smoothly restart a PTC relay after a startup error.

(d) Means for Solving the Problems The present invention provides a device in which a disc-shaped bimetal is housed in a bottomed case, and contacts are opened and closed according to temperature changes, in which the opening of the case A ring-shaped insulating plate is provided, and when the bimetal is operated, the bimetal and the insulating plate come into contact to close the opening.

(E) Function The overload protection device of the present invention has the above-mentioned configuration, and has an opening on one end face on the load side, so that when the load casing temperature is high, the load temperature can be easily detected as before, and the overload protection device is made of bimetallic metal. While improving the operating characteristics of the bimetal, when the bimetal is in operation, the bimetal and the insulating plate close the opening on the load side of the overload protection device to prevent heat from the heater from being absorbed into the casing when the casing temperature of the load is low. This allows the bimetal to operate well, improves protection performance, and lengthens the recovery time after operation, preventing the overload protection device from operating before the PTC relay drops below the Curie temperature. , it is possible to smoothly restart after a startup error.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

1 is an overload protection relay. This relay consists of a bottomed case 2 made of a metal material such as synthetic resin, a dish-shaped bimetal 5 arranged inside the case and fixed to the case 2 by a bolt 3 at the center, and having a contact 4; It consists of a ring-shaped heater 6 disposed close to the heater 6, and terminal plates 7 and 8 that are electrically connected to the heater and the bimetal 5 and extend outside the case 2. This overload protection 1 Ru-I is achieved by connecting the bimetal 5 in series to the common winding of the compressor and attaching it to the casing 10 of the compressor. The motor is protected by cutting off the circuit due to heat generated by the motor or self-heating.

A ring-shaped insulating plate 9 as shown in FIG. 3 is attached to the opening of the case 2. As shown in FIG.

This insulating plate has a structure that fits into a groove 11 formed in the case 2. When the overload protection relay 1 is not in operation, a gap is formed between the bimetal 5 and the insulating plate 9, as shown in FIG. During the reversal operation, the periphery of the bimetal contacts the insulating plate 9 as shown in FIG. 2, eliminating the above-mentioned gap and closing the opening of the case 2.

The overload protection device configured in this way can easily detect the temperature of the casing 10 of the compressor, which is the load, through the opening of the casing 2, which is the load side, as shown in FIG. Characteristics can be improved. Also, when the device is in operation, that is, when the bimetal 5 is inverted, the periphery of the bimetal comes into contact with the insulating plate 9, eliminating the gap between the bimetal S and the case 2, as shown in FIG. Since the opening of the case 2 is closed, when the temperature of the casing 11 of the compressor, which is the load, is low, the heat of the heater 6 can be made difficult to be absorbed by the casing IO, and the operation of the bimetal 5 can be improved. The protection performance can be improved.Also, since the heater 6 is located in the closed space formed by the bimetal 5 and the case 2 as described above, it is possible to prevent the heat of the heater 6 from leaking out of the case 2. As a result, when the overload protection device is connected to a starting circuit using a PTC relay, the overload protection device is activated before the PTC relay becomes below the Curie temperature. 1 can be prevented from operating, and restarting after a starting error can be smoothly performed.

In this embodiment, the insulator 9 is attached separately from the case 2 of the overload protection device 1, but the same effect can be obtained even if the insulator 9 is formed integrally with the case 2. Equivalents do not depart from the invention.

(G) Effects of the Invention As described above, according to the present invention, while maintaining the recommended characteristics when the load casing temperature is high as before, when the load casing temperature is low, the heat of the heater is reduced. By preventing the overload protection device from being absorbed by the casing, it is possible to improve the bimetal's operation, improve protection performance, and lengthen the recovery time after operation.A starting circuit is constructed by combining the overload protection device with a PTC starting relay. Even in such cases, restarting after a starting error can be smoothly performed.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an overload protection device in an inoperative state showing an embodiment of the present invention, Fig. 2 is a sectional view of the overload protection device in an operating state, and Fig. 3 is a plan view of an insulating plate. . 1... Overload protection relay, 2... Case, 4... Contact 5... Bimetal, 6... Heater, 9... Insulating plate.

Claims (1)

[Claims] (1) A disc-shaped bimetal is housed in a bottomed case, and the contacts are opened and closed according to temperature changes, and a ring-shaped insulating plate is provided at the opening of the case,
An overload protection device characterized in that, when the bimetal is operated, the bimetal and the insulating plate come into contact with each other to close the opening.