JP2827079B2 - Thermal protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal protector in which a thermally responsive plate, which is deformed by a temperature change of a bimetal or a trimetal, is formed into a shallow dish to perform a snap operation, and the snap operation is applied to opening and closing of contacts. It is.

[0002]

2. Description of the Related Art As such a switch, for example, a thermally responsive snap switch as shown in FIG. 5 is disclosed in Japanese Patent Application Laid-Open No. 62-88232. The heat-responsive snap switch 101 shown in FIG. 5 has a switch base 102 and a conductive bracket 104 which is electrically insulated and fixed by an insulating material 103 such as glass. Switch base 1
A support 105 is fixed to 02, and a fixed contact 106 is fixed to the conductive fitting 104 via a fixed contact support 107. The elastic plate 10 is located near the fixed end of the support 105.
One end of an elastic plate 108 is fixed, and one end of a heat deformable plate 109 such as a bimetal having a shallow dish-shaped curved portion for jumping and reversing is fixed to the other end of the elastic plate 108 via a connecting piece 110. . A movable contact 111 is connected to the other end of the heat deformable plate 109.
Are fixed to face the fixed contact 106. A screw 112 for operating temperature calibration, which is a first support, is provided at the center of the support 105.

One end of the heat-deformable plate 109 has an elastic plate 108.
The second bearing 10 provided at the tip of the support 105 by the
It is pressed against 5A and rotatably supported. When the temperature of the heat-deformable plate 109 has not reached the predetermined temperature, the convex surface of the curved portion is pressed and supported by the screw 112 as the first support portion. Is supported by pressing the movable contact against the fixed contact with a predetermined pressure, and pressing the end fixed to the elastic plate against the second support. When the temperature of the heat deformable plate 109 reaches a predetermined temperature, the heat deformable plate 109 reverses the bulging direction by a snap operation, and the movable contact 111 and the fixed contact 10
And 6. Therefore, it is possible to reliably cut off the power supply to the control target device at a predetermined temperature.

[0004]

However, in the above-mentioned heat-responsive snap switch, the heat-deformable plate and the support are in contact with each other without being electrically insulated at the first and second support portions. During that time, a bypass current flows and the current flowing through the elastic plate decreases. Further, the magnitude of the bypass current varies greatly because it depends on the contact resistance of each of the support portions. Therefore, there is no problem with a simple temperature switch that operates by detecting only the ambient temperature change by setting the resistance of the elastic body and the heat responsive plate low, but there is no problem. Is set to a predetermined value and the operation is performed in association with the ambient temperature and the magnitude of the current value, the amount of heat generation is insufficient or the variation among products is large, and stable product characteristics cannot be obtained. There was a problem.

[0005]

Accordingly, the thermal protector of the present application has a cover plate in which conductive terminals are insulated and fixed to a substantially circular metal plate, and a thermally responsive plate support is fixed to the metal plate of the cover plate. The fixed contact support is fixed to the conductive terminal,
A fixed contact is fixed to the fixed contact support, and a first support portion is provided substantially at the center of the thermally responsive plate support and a second support portion is provided at a tip thereof, and the metal plate of the thermally responsive plate support is provided. One end of an elastic plate having a predetermined resistance value and assisting heat generation of the thermally responsive plate during energization is fixed near the fixed end of the elastic plate, and the elastic plate extends along the support and has a sharp end at the other end. One end of a thermally responsive plate having a shallow dish-shaped curved portion for reversing a jump is fixed, and one end of the thermally responsive plate is rotatably supported by being pressed against the second support portion by an elastic plate. A movable contact is fixed to the other end of the response plate, that is, a movable end, and the movable contact is arranged so as to face the fixed contact. When the temperature of the thermal response plate has not reached a predetermined temperature, the curved portion is provided. The swelled side of the first support portion provided on the heat responsive plate support The movable end of the thermally responsive plate is supported by pressing the movable contact against the fixed contact with a predetermined pressure, and the end fixed to the elastic plate is pressed against the second support portion and supported by the pressing force. The first bearing is provided with an operating temperature calibration mechanism for configuring the operating temperature by adjusting the pressing force on the heat responsive plate,
When the thermal responsive plate reaches a predetermined operating temperature and jumps and reverses, the movable end to which the movable contact is fixed is preliminarily biased to the fixed end by the elastic plate so that the movable end is separated from the fixed contact. The heat responsive plate is in contact with the first and second support portions via a thin and flexible insulating member having heat resistance higher than the operating temperature of the heat responsive plate and having sufficient flexibility. By doing so, it is characterized in that a bypass current is prevented from flowing through the thermally responsive plate support, thereby preventing variations in the amount of heat generated by the elastic plate and the thermally responsive plate during energization.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a thermal protector 1 according to the present invention. The thermal protector 1 has a cover plate 5 in which a conductive terminal 3 is hermetically sealed through a through hole 2A formed in a substantially circular metal plate 2 with an electrically insulating sealing material 4 such as glass or ceramic. . A thermally responsive plate support 6 is fixed to the metal plate 2 of the cover plate 5, and a fixed contact 8 is fixed to the conductive terminal 3 via a fixed contact support 7.

One end of an elastic plate 9 is fixed near the fixed end of the thermally responsive plate support 6 to the metal plate 2. This elastic plate 9
Are disposed substantially parallel to the heat responsive plate support 6. To the other end of the elastic plate 9, one end of a thermally responsive plate 10 such as a bimetal formed into a shallow dish shape for quick reversal is fixed via a connection piece 11. The connection piece 11 is not always necessary, and the heat responsive plate 10 and the elastic plate may be directly fixed. A movable contact 12 is provided at the other end of the thermally responsive plate 10.
Are fixed so as to face the fixed contact 8 described above. A screw 13 as a first support is mounted near the center of the thermally responsive plate support 6, and a fixed portion between the elastic plate 9 and the thermally responsive plate 10 is held at the tip of the thermally responsive plate support 6. A second supporting portion 6A is provided.

The elastic plate 9 has a thermally responsive plate 10 and an elastic plate 9 in advance.
A biasing force is applied in a direction of pressing the connecting piece 11 which is a fixed portion to the second support portion 6A and separating the movable contact 12 of the thermally responsive plate 10 from the fixed contact. The screw 13 serving as the first bearing is inserted through a through hole (not shown) formed near the center of the elastic plate 9 so as not to contact the elastic plate, and abuts on the surface of the thermally responsive plate 10 which is swelled at normal temperature. Here, the first support and the second support are directly connected to the heat responsive plate 10 and the connection piece 1.
This is performed via a thin insulating member 14 so as not to make contact with 1. As the insulating member 14, a material having heat resistance higher than the operating temperature of the thermally responsive plate is used. For example, if the operating temperature of the thermally responsive plate after calibration is 150 ° C., 20
It is preferable to use a heat-resistant material such as aramid paper having a heat-resistant temperature of 0 ° C. or higher.

The operation temperature calibration of the thermal protector 1 will be described. The temperature calibration mechanism of the switch has a hole 6B formed in the heat responsive plate support 6 by punching of a press as shown in FIG. Screw 13 to be combined
It consists of. The hole 6B is a long hole having a threaded portion 6C for receiving the screw 13 at the center. Side holes 6D and 6E are formed on both sides along the hole 6B, and the elongated strips 6F and 6G are formed.
Is configured. The inner diameter of the threaded portion 6C is the screw 13
Is smaller than the outer diameter of

Therefore, at the time of temperature calibration, the screw 6 is screwed into the threaded portion 6C to expand the hole 6B outward and form a spiral groove on the inner surface of the threaded portion 6C. At this time, since the screw 13 is clamped and held by the reaction force of the strips 6F and 6G accompanying the expansion of the hole 6B, no play of the screw occurs at all, and the screw position does not return when calibrated. When the screw 13 is further screwed in, the tip of the screw comes into contact with the surface of the thermally responsive plate 10 that swells at normal temperature via the insulating member 14 to support the screw. With this pressing force, the heat responsive plate 1
The movable end of 0 is supported by pressing the movable contact 12 against the fixed contact 8 and pressing the end fixed to the elastic plate 9 against the second support portion. By adjusting the screwing amount of the screw 13, the stress applied to the thermally responsive plate 10 can be precisely adjusted. As described above, since there is no return immediately after the calibration due to the loosening of the screw 13, the operation reversal temperature of the switch can be accurately determined. Can be set to a desired value.

After the operating temperature calibration is calibrated by the above-described method, the opening of the bottomed cylindrical metal housing 15 is air-tightly fixed to the metal plate 2 of the cover plate 5 by a method such as ring projection welding. By doing so, the thermal protector can have an airtight structure. Further, at this time, by replacing the gas in the internal space with an inert gas such as argon or helium, or a pollution preventing gas such as nitrogen, corrosion of each component such as rust can be prevented. Further, by including at least helium in the sealed gas, a helium leak detector can be used in an airtightness test of the housing, and the airtightness can be confirmed with high accuracy.

The elastic plate 9 for electrically connecting the thermally responsive plate support 6 and the thermally responsive plate 10 has high rigidity against a force in a direction along the plane, but has a high rigidity in a direction perpendicular to the plane. Since the heat responsive plate 10 is sufficiently flexible, no excessive bending stress is applied to the heat responsive plate 10 during temperature calibration. For example, since the curved shape of the heat responsive plate 10 has a difference due to manufacturing variations, when the elastic plate 9 is not used and one end of the heat responsive plate 10 is fixed, the heat responsive plate 1
If the curvature of 0 is large, the contact pressure between the movable contact 12 and the fixed contact 8 increases before the temperature calibration, and a large bending stress is applied near the fixed end of the thermally responsive plate 10. On the other hand, if the curvature of the thermally responsive plate is small, a stress larger than a normal one is applied by the temperature calibration mechanism in order to obtain a contact pressure between the movable contact 12 and the fixed contact 8, so that the vicinity of the fixed end is increased. Has a large bending stress.

However, by using the elastic plate 9, the fixed end of the thermally responsive plate 10 with the elastic plate 9 can be operated in a direction perpendicular to the plane of the thermally responsive plate 10, and the thermally responsive plate 10 is fixed by the second support. It is supported so as to be rotatable about the fixed end in a direction perpendicular to the plane. Therefore, even under the condition where a large stress is applied as described above, since the elastic plate bends and the fixed end rotates, most of the bending stress is absorbed by the elastic plate. Therefore, the bending stress is close to the fixed end of the thermally responsive plate. It is possible to avoid a change in operating characteristics due to permanent deformation of the thermally responsive plate and a decrease in durability due to stress concentration without concentration.

In the thermal protector according to the present invention, not only the contacts are simply opened and closed by heat, but also the amount of heat generated by the components due to the current and the operating characteristics are linked so that the current can be cut off even when an overcurrent flows. . That is, the thermally responsive plate 10
In addition, the resistance value of the elastic body 9 is set to a predetermined value,
For example, even when the ambient temperature is lower than the operating temperature of the switch, each component generates heat by the current flowing through the switch, and when a current exceeding a predetermined value such as an overcurrent flows, the temperature of the thermally responsive plate 10 is calibrated. When the operating temperature becomes higher than the set operating temperature and a jump reversal operation is performed, the gap between the contacts is opened.

For example, the thermal protector 1 shown in FIG. 1 includes a conductive terminal 3, a fixed contact support 7, a fixed contact 8, and a movable contact 12.
Power is supplied through the path of the heat responsive plate 10, the connecting piece 11, the elastic plate 9, the heat responsive plate support 6, the metal plate 2 and the housing 15.
Here, if the insulating member 14 is not provided, the screw 13 as the first support directly contacts the thermally responsive plate 10 and the second support 6A.
Directly contact the connection piece 11. Therefore, a bypass current is generated that directly flows between the thermally responsive plate support 6 and the thermally responsive plate 10 without passing through the elastic plate 9. As a result, the current passing through the elastic plate 9 decreases, the amount of heat generation decreases, and the desired performance cannot be obtained.
Also, the value of this bypass current depends on the contact resistance between the first and second support portions and the heat responsive plate, and therefore, there is a large individual difference for each product. It is impossible to design products in anticipation.

However, in the thermal protector 1 of the present invention, the insulating member 14 is disposed on the first and second support portions, and the bypass current flowing directly between the thermally responsive plate support 6 and the thermally responsive plate 10 is eliminated. doing.

The insulating member 14 has a thin plate shape as shown in FIG. 3, and has a through hole 14A for assembling. The insulating member 14 is held by fixing the thermally responsive plate 10 and the elastic body 9 in a state where the thermally responsive plate 10 or the connecting piece 11 is bent through the through hole 14A as shown by an arrow A in FIG. . In this state, the elastic plate 9 is fixed to the thermally responsive plate support 6, so that the long side 14B of the insulating member 14 is in contact with the contact point between the thermally responsive plate 10 and the first support and the short side 14C.
Cover the contact points with the second bearings and insulate between the respective bearings and the thermally responsive plate 10.

As a result, the current flowing through the elastic body 9 and the thermally responsive plate 10 does not vary from product to product, and the desired heat generation with respect to the supplied current is obtained, so that the electric circuit is reliably cut off even with overcurrent. can do.

Here, by using a thin plate having sufficient flexibility and toughness, such as aramid paper, polyimide, polyphenylene sulfide film, etc., the insulating member 14 can be easily processed and mounted. For example, when an insulator is used as an insulating member, the insulator must be formed into a complicated shape in order to insulate the first support and the second support with one member as in the present embodiment, and processing becomes difficult. .
In addition, it is difficult to form a thin plate due to poor flexibility, and there is no toughness and no durability.

However, by using a thin plate having sufficient flexibility and toughness as the insulating member 14 as in the present invention, processing and mounting of the insulating member become easy,
In addition, the thin plate shape minimizes the distance between the thermally responsive plate 10 and the elastic plate 9, and the heat from the elastic plate is quickly transmitted to the thermally responsive plate. Further, since the insulating member 14 has sufficient flexibility, the operation of the thermally responsive plate 10 and the elastic plate 9 is not affected.

[0021]

According to the thermal protector of the present invention,
Since the contact between the heat responsive plate and the first support portion and the second support portion of the heat responsive plate support is made via the insulating member, the bypass current flowing directly between the heat responsive plate support and the heat responsive plate. The current flowing through the elastic body and the heat responsive plate does not vary from product to product, and the desired amount of heat generated for the supplied current is obtained. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the thermal protector of the present invention.

FIG. 2 is a longitudinal sectional view of the thermal protector of FIG.

FIG. 3 is an embodiment of an insulating member used in the thermal protector of the present invention.

FIG. 4 is a view for explaining assembly of the insulating member of FIG. 3;

FIG. 5 is a cross-sectional view of an example of a conventional heat-responsive snap switch.

[Explanation of symbols]

 1: thermal protector 2: metal plate 3: conductive terminal 4: sealing material 5: lid plate 6: thermally responsive plate support 6A: second support 7: fixed contact support 8: fixed contact 9: elastic plate 10: Thermal response plate 11: Connection piece 12: Movable contact 13: Screw (first support) 14: Insulating member 15: Housing

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01H 37/00-37/56

Claims (1)

(57) [Claims] A cover plate in which conductive terminals are insulated and fixed to a substantially circular metal plate, a thermally responsive plate support is fixed to the metal plate of the cover plate, and a fixed contact support is fixed to the conductive terminals. A fixed contact is fixed to the contact support, a first support portion is provided at substantially the center of the thermally responsive plate support, and a second support portion is provided at the tip, and the metal plate of the thermally responsive plate support is provided. One end of an elastic plate having a predetermined resistance value and assisting heat generation of the thermally responsive plate when energized is fixed near the fixed end of the elastic plate. The elastic plate extends along the support and jumps to the other end. One end of a thermally responsive plate having a shallow dish-shaped curved portion for inversion is fixed, and one end of the thermally responsive plate is rotatably supported by being pressed against the second support portion by an elastic plate. A movable contact is fixed to the other end of the plate, that is, the movable end. When the temperature of the heat responsive plate does not reach a predetermined temperature, the bulged side of the curved portion is pressed against a first support provided on the heat responsive plate support when the temperature of the heat responsive plate does not reach a predetermined temperature. With this pressing force, the movable end of the thermally responsive plate is supported by pressing the movable contact against the fixed contact with a predetermined pressure and pressing the end fixed to the elastic plate against the second support portion. The first support is provided with an operating temperature calibrating mechanism for adjusting the pressing force to the thermal responsive plate to configure the operating temperature, and the thermal responsive plate reaches a predetermined operating temperature and rapidly jumps over. Then, the movable end to which the movable contact is fixed is configured to receive a biasing force in advance by the elastic plate so that the movable end to which the movable contact is fixed is separated from the fixed contact. The contact with the bearing is higher than the operating temperature of the thermo-responsive plate. By using a heat-resistant and sufficiently flexible thin plate-shaped insulating member, bypass current is prevented from flowing through the heat-responsive plate support. Thermal protector characterized by preventing variations in the amount of heat generated.