JP2000149742A - Thermal protector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal protector having large current capacity and high reliability. SOLUTION: This thermal protector has a fixed electrode plate 2 having a fixed contact 1, and a movable electrode plate 4 having a moving contact 3, and for the fixed electrode plate 2 and the movable electrode plate 4, the fixed contact 1 and the moving contact 3 are so formed oppositely to each other as to be able to be contacted on and disconnected from each other. A thermally actuated element 5 is formed on the side opposite to the fixed electrode plate 2 side of the movable electrode plate 4. The movable electrode plate 4 has a distorted part 4a formed by bending one part thereof and is an elastic body having a stress in the direction trying to separate from the fixed electrode plate 2, and although the movable electrode plate 4 is normally so pushed toward the fixed electrode plate 2 by the pressing force of the thermally actuated element 5 as to contact the moving contact 3 on the fixed contact 1, when the thermally actuated element 5 is reversed, the movable electrode plate 4 is separated from the fixed electrode plate 2 by the stress in the direction trying to separate from the fixed electrode plate 2 and thus separates the moving contact 3 from the fixed contact 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normally closed contact type self-resetting thermal protector.

[0002]

2. Description of the Related Art A normally closed contact type self-recovering type thermal protector is connected to a power supply circuit of an electric device, and is used only when an excessive current flows in the electric device or when an ambient temperature becomes abnormally high. The contact is opened by the bending action of the electric device, and the power supply to the electric device is cut off. Then, the contact automatically reset by the temperature drop due to the cutoff of the power supply restarts the power supply, which not only helps to prevent danger but also allows the electric device to always operate in a predetermined temperature range. In addition, it is possible to notify an abnormality of the electric device.

In recent years, thermal protectors used for motors and the like among electric appliances have been required to be further reduced in size and cost. Unlike a thermal protector for a general circuit, a thermal protector used for a motor or the like is required to have a relatively large rated current. When a large current flows through a thermally responsive element having a high resistance value, the temperature immediately rises due to the self-heating action, so that it is difficult to obtain a thermal protector having a desired low operating temperature.

As a countermeasure, a small-sized motor thermal protector uses an electrode material having a resistance as low as possible and, as shown in FIG. 3, is called a movable electrode plate 13 having a resistance lower than that of the thermal conductive element 12. Hook 14 on metal plate
And a structure in which the end portion of the thermally responsive element 12 is interposed between the hook portions 14 is proposed. That is, when a large current flows, the current is shunted to the movable electrode plate 13 having a low resistance, and the heat generation of the thermally responsive element 12 is to be suppressed as much as possible. In FIG. 3, reference numeral 15 denotes a movable contact, 1
Reference numeral 6 denotes a fixed contact, and 17 denotes a fixed electrode.

[0005]

However, in such a configuration, when the thermally responsive element 12 is inverted as shown in FIG. 4, the movable electrode plate 13 is lifted. For this reason, a load is applied to the thermoresponsive element 12 at the time of reversal, the operating temperature varies, and the hook portion 14 of the movable electrode plate 13
If the height of the hooks 14 is not uniform, for example, as shown in FIG. 5, if the bending width of the hook portion 14 is large, when the thermoresponsive element 12 is inverted, the interval between the movable contact 15 and the fixed contact 16 becomes short,
Because of chattering and arcing, there was a problem in reliability.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a thermal protector having a large current capacity and high reliability.

[0007]

A thermal protector according to the present invention has a fixed electrode plate having a fixed contact at one end and a movable electrode plate having a movable contact at one end. A thermally conductive element is provided on the opposite side of the movable electrode plate from the fixed electrode plate side while being provided so as to be capable of coming and going, and the movable electrode plate is provided with the fixed electrode. An elastic body having a stress that tends to separate from the plate, wherein the movable electrode plate is pressed toward the fixed electrode plate by a pressing force of the thermally conductive element,
When the movable contact and the fixed contact are in contact with each other, and when the thermally conductive element is inverted, the movable electrode plate separates from the fixed electrode plate due to the stress, and separates the movable contact and the fixed contact. It has the structure to make it.

As a result, it is possible to supply a thermal protector with high reliability and good productivity.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a thermal protector according to an embodiment of the present invention comprises a fixed electrode plate 2 made of a copper-based alloy having a fixed contact 1 at one end and a movable contact at one end. The fixed electrode plate 2 and the movable electrode plate 4 are provided so that the fixed contact 1 and the movable contact 3 are opposed to each other so as to be able to contact and separate from each other. On the opposite side of the movable electrode plate 4 from the fixed electrode plate 2 side, Cu—Ni—Mn /
A thermally conductive element 5 made of Ni-Fe is provided at a position.

The fixed electrode plate 2 has a central portion buried in a resin bead 6 and the other end penetrated from the resin bead 6, and an external lead wire 7 is connected to the other end provided therethrough. Have been. The movable electrode plate 4 and the thermal conductive element 5 are welded at the other end to one end of a movable electrode plate support 8 provided with both ends penetrating from a resin bead 6. An external lead wire 9 is provided at the other end of the movable electrode plate support 8.
Is connected.

The resin bead 6 is inserted into the case 10 and is fixed with an epoxy-based filler 11. The filler 11 connects the other end of the movable electrode plate support 8 to the external lead wire 9. A connection portion and a connection portion between the other end of the fixed electrode plate 2 and the external lead wire 7 are embedded in the case 10.

The movable electrode plate 4 has a distorted portion 4a formed by bending a part of the movable electrode plate 4, and is an elastic body having a stress that tends to separate from the fixed electrode plate 2. The electrode plate 4 is pushed toward the fixed electrode plate 2 by the pressing force of the thermally conductive element 5 to bring the movable contact 3 and the fixed contact 1 into contact, but the thermally conductive element 5 is an electronic device (not shown). 2), the movable electrode plate 4 is separated from the fixed electrode plate 2 by a stress that tends to separate from the fixed electrode plate 2 as shown in FIG. The movable contact 3 and the fixed contact 1 are separated from each other.

In the present embodiment, a metal plate having a resistance value of the movable electrode plate 4 lower than a resistance value of the thermally responsive element 5 is used. For this reason, even if a large current flows through the thermal conductive element 5, the current can be diverted to the movable electrode plate 4 having a low resistance, and thus the heat generated by the thermal conductive element 5 can be suppressed as much as possible. That is, even if a large current flows, the thermal responsive element 5 is not immediately inverted, so that a thermal protector having a large current capacity can be realized.

The thermal protector of the present embodiment differs from the conventional thermal protector having the hook portion 14 shown in FIGS.
Since the movable electrode plate 4 opens the contact point due to its own spring property, the problem of arc or chattering caused by the variation of the hook width of the hook portion 14 is eliminated, and a great effect can be obtained in terms of reliability. Also, unlike the conventional thermal protector, the thermal protector according to the present embodiment does not have a structure in which the movable electrode plate 4 is pulled up by reversing the thermally responsive element 5, so that a load is not applied to the thermally responsive element 5. Can be reduced,
Reliability can be improved.

[0015]

As described above, according to the present invention, it is possible to obtain a thermal protector having a large current capacity capable of improving reliability as compared with a conventional thermal protector.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal protector according to an embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a cross-sectional view of a conventional thermal protector.

FIG. 4 is a sectional view of the same.

FIG. 5 is a sectional view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed contact 2 Fixed electrode plate 3 Movable contact 4 Movable electrode plate 4a Distortion part 5 Thermal conductive element

Claims (2)

[Claims] 1. A fixed electrode plate having a fixed contact at one end and a movable electrode plate having a movable contact at one end, wherein the fixed contact and the movable contact are provided so as to be able to contact and separate from each other. Along with the movable electrode plate on the opposite side to the fixed electrode plate side, a heat conducting element is located and provided,
The movable electrode plate is an elastic body having a stress that tends to separate from the fixed electrode plate, and the movable electrode plate is pressed toward the fixed electrode plate by a pressing force of the thermal conductive element, When the movable contact and the fixed contact are in contact with each other, and when the thermally conductive element is inverted, the movable electrode plate separates from the fixed electrode plate due to the stress, and separates the movable contact and the fixed contact. A thermal protector characterized by having 2. The thermal protector according to claim 1, wherein a resistance value of said movable electrode plate is lower than a resistance value of said thermoresponsive element.