JP2001076600A - Thermally reactive switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent chattering of contact points of a movable contact point and a fixed contact point by providing the fixed contact point, the movable contact point for contacting with and separating from the fixed contact point and a bimetal piece fixing the movable contact point to one end side and having a reversing part reversible according to a temperature, and forming a warp preventive means in the bimetal piece. SOLUTION: At a normal temperature and an ordinary working temperature, mutually oppositely arranged movable contact point 6 and fixed contact point 3 contact to put the contact points in an ON state. When a temperature rises, a reversing part 5a arranged in a bimetal piece 5 fixed with the movable contact point 6 performs reversing operation according to a temperature rise. The movable contact point 6 fixed to the bimetal piece 5 is driven together with the bimetal piece 5, and separates from the fixed contact point 3 to put the contact points in an OFF state. In the reversing part 5a of the reversed bimetal piece 5, a swelling part reverses, and projects in the direction of the fixed contact point 3. At slowly cooling time of a temperature drop, the reversing part 5a abuts to a support projection part 1a to avoid chattering of the contact points of the movable contact point 6 and the fixed contact point 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally responsive switch, and more particularly, to a switch structure for inverting a movable contact and opening and closing an electrical contact by the thermal response of a bimetal piece.

[0002]

2. Description of the Related Art A thermally responsive switch comprises a movable electrode having a movable piece of a thermally responsive element (bimetal) in which a plurality of metals having different coefficients of thermal expansion are bonded to each other, and a fixed electrode which forms a normally closed contact circuit together with the movable electrode. An electrode is provided and is connected to a circuit of the electric device to protect the electric device.

That is, a thermally responsive switch connected to a circuit of an electric device has a structure in which a switch contact is opened by an inversion action of a bimetal when an excessive current flows through the electric device or when an ambient temperature becomes abnormally high. Therefore, the power supply to the electric device is cut off.
Then, when the power supply to the electric equipment is cut off, the ambient temperature decreases, and the bimetal is automatically reset, and the switch contact is closed again to restart the power supply. It is possible to operate in a temperature range.

FIGS. 13 and 14 show the structure of a conventional thermally responsive switch. FIG. 13 is an explanatory diagram showing the state of the bimetallic piece at normal temperature, and FIG. 14 is an explanatory view showing the state of the bimetallic piece being inverted when the temperature rises.

In the figure, a case 11 is formed in a box shape with an insulating material such as a synthetic resin.
A support member to be described later is inserted and engaged with 1a.

The support member 12 is also formed of an insulating material such as a synthetic resin.
A base portion 12a is inserted into and engaged with 1a, and a contact holding portion 12b formed substantially in an L shape. An upright wall 12c is provided at the tip of the contact holding portion 12b, and a planar step 12d is provided inside the upright wall 12c. A fixed contact 13 made of a conductive material is provided on the step 12d. The contact holding portion 12b is formed with a protruding portion 12e protruding toward a reversing portion of a bimetal piece which will be described later. Note that, at normal temperature when a movable contact (to be described later) and the fixed contact 13 are in contact with each other, the protruding portion 12e is separated from the bimetal piece, and the movable contact and the fixed contact 1 (described later) are separated.
The height dimension of the bimetal piece is set so as to be in contact with the bimetal piece at the time of reversal where the 3 is separated.

On the opposite side of the base 12a, a pair of substantially parallel movable terminals 14 and fixed terminals 15 are provided which protrude outward from the opening 11a of the case 11 and are connected to an external circuit. I have. A central portion of the fixed terminal 15 is embedded in the contact holding portion 12b extending to the base portion 12a, and a tip portion thereof is electrically connected to the fixed contact 13. The movable terminal 14 has a central portion embedded in the base portion 12 a, and a distal end portion thereof is disposed inside the opening 11 a of the case 11.

In the base 12a, for example, a bimetal piece 16 formed by attaching two kinds of metal materials having different coefficients of thermal expansion into a flat plate shape is embedded. A movable contact 17 facing the fixed contact 13 is fixed to one end of the bimetal piece 16, and the other end is connected to the base 12a.
And a part thereof is connected to the movable terminal 14 disposed inside the opening 11a of the case 11 by spot welding or the like. In addition, a bulging reversal portion 16a for promoting reversal action is formed at the center of the bimetal piece 16, and by providing the reversal portion 16a, the reversal operation of the bimetal piece 16 according to the temperature is performed. I am sure that I can do it.

Also, when the reversing portion 16a is reversed according to the temperature, the projection 12e is provided on the contact holding portion 12b.
When a is returned without reversing due to a gradual temperature change (gradual cooling), the reversing portion 16a comes into contact with the protrusion 12e, so that the movable contact 17 and the fixed contact 13 The contact is kept in a separated state, and the movable contact 17 and the fixed contact 13 come into contact with each other only when the inverting portion 16a returns to the inverted state, so that the movable contact 17 and the fixed contact 13 at the time of slow cooling are connected. The occurrence of chattering at the contacts can be prevented.

[0010]

However, in the above-described structure of the conventional thermally responsive switch, the bulging inversion portion 16a is formed on the flat bimetal piece 16 to which the movable contact 17 is fixed. The movable contact 17 is separated from the fixed contact 13 by the reversing operation of the reversing part 16a, and the space between the movable contact 17 and the reversing part 16a is flat, and the flat part is the reversing part. Since the movable contact 17 and the fixed contact 13 are separated from each other, there is a problem that chattering occurs between the movable contact 17 and the fixed contact 13 since the movable contact 17 is separated from the fixed contact 13.

Therefore, the present invention solves the above-mentioned problems, and when the bimetal piece performs the reversing operation in accordance with the temperature, the reversing operation can be reliably performed, and the contact state between the movable contact and the fixed contact can be reduced. An object of the present invention is to provide a thermally responsive switch capable of stabilizing and preventing chattering of a contact between a movable contact and a fixed contact when the contact is reversed and separated when the temperature rises.

[0012]

According to the present invention, as a first means for solving the above-mentioned problems, a fixed contact, a movable contact which comes into contact with and separates from the fixed contact, and the movable contact are fixed to one end, And a bimetal piece having a dome-shaped reversal portion that can be reversed according to temperature, wherein a warpage preventing means is formed on the bimetal piece.

[0013] As a second means, the warpage preventing means is characterized in that the inversion portion of the bimetal piece is inverted according to temperature, and the inversion portion does not invert when the movable contact is separated from the fixed contact. In this case, the movable contact and the fixed contact are formed on a flat plate portion of the bimetal piece so as not to be separated from each other.

As a third means, the warp preventing means is formed near the movable contact and the reversing portion.

As a fourth means, the warp preventing means is a rib formed on the bimetal piece.

As a fifth means, the warp preventing means is a bent portion formed on a side end of the bimetal piece.

As a sixth means, the warpage preventing means is constituted by an intermediate member interposed between the movable contact and the bimetal piece.

As a seventh means, the intermediate member is formed larger than the outer shape of the movable contact.

As an eighth means, the intermediate member is formed of Cu and its alloy material.

As a ninth means, the warp preventing means is a curved surface portion protruding in a direction opposite to a dome-shaped bulging direction of the inverted portion formed on the bimetal piece.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5 show a structure of a thermally responsive switch according to a first embodiment of the present invention. FIG. 1 is an exploded perspective view of the thermally responsive switch, FIG. 2 is a plan view thereof, FIG. Is a plan view of the bimetal piece with the movable contact fixed thereto, and FIG. 5 is a front view of the same.

In the figure, an insulating case 1 is formed in a box shape with an upper surface opened by an insulating material such as a synthetic resin. Terminals, which will be described later, are provided on the inner bottom of the insulating case 1, and one end of each terminal is led out from both sides of the insulating case 1. Also,
At the center of the inner bottom surface of the insulating case 1, there is provided a support projection 1a projecting hemispherically from the inner bottom surface.

The first terminal 2 is formed of a conductive metal material such as phosphor bronze in a flat plate shape. At one end of the first terminal 2 is provided a mounting hole 2a to which a fixed contact 3 made of silver tin oxide or the like is fixed. At the other end of the first terminal 2, the insulating case is provided. A connection terminal portion 2b is provided which is led out from the side surface portion 1 and is connected to a circuit of another electric device.

The first terminal 2 has a mounting hole 2a to which the fixed contact 3 is fixed, and a connection terminal 2b.
A wide opening 2c near the mounting hole 2a.
Is provided. The opening 2 c is formed on the center line passing through the mounting hole 2 a in the longitudinal direction of the first terminal 2, and the width of the opening 2 c in the width direction of the first terminal 2. Is formed so as to be larger than the width of the mounting hole 2a. Further, the opening 2c is formed by cutting so as to go around the outer periphery of the mounting hole 2a.

The first terminal 2 is provided with an inclined portion 2d at a portion including the opening 2c, and a mounting hole 2 to which the fixed contact 3 is fixed via the inclined portion 2d.
The configuration is such that the portion a is connected to the connection terminal portion 2b. When the first terminal 2 is attached to the insulating case 1, the inclined portion 2 d is embedded and attached to the inner bottom of the insulating case 1.

The second terminal 4 is also formed of a conductive metal material such as phosphor bronze in a flat plate shape. A projecting portion 4a is formed on one end side of the second terminal 4 by biasing the thickness with a press or the like, and the projecting portion 4a is inserted and fixed in a fixing hole at one end of a bimetal piece described later. It is a welded part. At the other end of the second terminal 4, there is provided a connection terminal 4b which is led out from the side surface of the insulating case 1 and is connected to a circuit of another electric device.

The second terminal 4 has a wide opening 4c near the protrusion 4a between the protrusion 4a for fixing a bimetal piece to be described later and the connection terminal 4b. Is provided. The opening 4c is formed on the center line passing through the protrusion 4a in the longitudinal direction of the second terminal 4, and in the width direction of the second terminal 4,
The width of the opening 4c is formed to be larger than the width of the protrusion 4a. The opening 4c is
The cutout is formed so as to orbit around the outer periphery of the protrusion 4a.

The second terminal 4 is provided with an inclined portion 4d at a portion including the opening 4c, and a projecting portion 4a to which a bimetal piece to be described later is fixed via the inclined portion 4d. , And the connection terminal portion 4b. When the second terminal 4 is attached to the insulating case 1, the inclined portion 4 d is embedded and attached to the inner bottom of the insulating case 1.

As described above, by providing the openings 2c and 4c in the first and second terminals 2 and 4,
For example, during transportation or mounting, the connection terminal portions 2b, 4
Even if an external force is applied to the connection terminals 2b and a force such as bending in the thickness direction is applied to the connection terminal portions 2b and 4b, the stress is interrupted by the openings 2c and 4c. The influence of external stress on the fixed portion with the movable contact and the fixed portion with the fixed contact 3 can be reduced, the influence on the displacement of each contact portion can be reduced, and the temperature characteristics can be stabilized. Thus, a thermally responsive switch can be obtained.

The inclined portions 2d and 4d are provided in portions including the openings 2c and 4c, and the inclined portions 2d and 4d are embedded in the inner bottom portion of the insulating case 1 and attached. In addition, the embedded portions of the second terminals 2 and 4 can be lengthened, and can be firmly fixed without increasing the outer shape of the insulating case 1, so that downsizing can be achieved. Further, it is possible to prevent flux from entering the inside during soldering.

The bimetal piece 5 is made of, for example, a flat plate made of at least two types of metal materials having different coefficients of thermal expansion, that is, a high expansion material made of a material having a high coefficient of thermal expansion and a low expansion material made of a material having a low coefficient of thermal expansion. It is formed by laminating and joining in a shape. A movable contact 6 made of silver tin oxide or the like, which comes into contact with or separates from the fixed contact 3, is fixed to one end of the bimetal piece 5, which is a free end, by a method such as electric spot welding. Are fixed to the protruding portions 4a provided on the second terminals 4 by a method such as electric spot welding.

In this case, the connecting point between the second terminal 4 and the other end of the bimetal piece 5 is not the whole surface, but
Since the partial coupling is performed only at the protruding portion 4a, the operation characteristics are not impaired when the bimetal piece 5 performs the reversing operation.

In the center of the bimetal piece 5,
Inflated dome-shaped reversing portion 5 for promoting reversing action
a is formed, and by forming the inversion portion 5a, the inversion operation of the bimetal piece 5 according to the temperature characteristic, that is, the temperature, can be surely performed.

Further, the bimetal piece 5 is provided with a rib 5b as a warp preventing means near the movable contact 6 and the reversing portion 5a. The rib 5b is formed in a flat plate portion 5c located between the movable contact 6 and the reversing portion 5a by linearly protruding by a press or the like. Further, the rib 5b is connected to the flat plate portion 5c.
Are formed so as to face each other in the vicinity of the side end side. By providing the rib 5b on the flat plate portion 5c, it is possible to prevent the flat plate portion 5c from warping due to heat.

By providing the bimetal piece 5 with the rib 5b, the inversion part 5a of the bimetal piece 5 is inverted according to the temperature, and the movable contact 6 is connected to the fixed contact 3
When the bimetal piece 5 is separated from the movable contact 6 for some reason, even if the reversing portion 5a does not reverse, the bimetal piece 5 can be prevented from warping due to heat when the temperature rises. Fixed contact 3
And the occurrence of chattering between the contacts can be prevented. The warp preventing means may be formed in a region including the movable contact 6 outside the edge facing the movable contact 6 in the outer peripheral edge of the dome of the inverted portion 5a. .

The cover 7 is formed in a substantially plate shape from an insulating material such as a synthetic resin. The cover 7 is mounted on an opening of the insulating case 1 and is provided inside the insulating case 1. The influence of dust, gas, and the like on the second terminals 2 and 4, the bimetal piece 5, the movable contact 6, the fixed contact 3, and the like is prevented.

Next, the operation of the above-described thermoresponsive switch of the present invention will be described. At a normal temperature and a normal use temperature, the movable contact 6 and the fixed contact 3, which are arranged to face each other, are in contact with each other and the contacts are in an ON state. If the temperature rises from this state for some reason, the inversion section 5a provided on the bimetal piece 5 to which the movable contact 6 is fixed performs an inversion operation according to the rise in temperature. At this time, the movable contact 6 fixed to the bimetal piece 5 is
, And is separated from the fixed contact 3, so that the contact is turned off. In this case, the swelling portion of the inverted portion 5a of the inverted bimetal piece 5 is inverted, and projects in the direction of the fixed contact 3, that is, the direction of the inner bottom surface of the insulating case 1.

Further, when the temperature decreases from this state and returns to the normal temperature, the inversion portion 5a of the bimetal piece 5 reverses and returns according to the decrease in temperature, and the direction opposite to the direction of the fixed contact 3 is reversed. As the movable contact 6 comes into contact with the fixed contact 3, the contact is turned on and the contact returns to the initial state.

In the above-described structure of the thermally responsive switch according to the present invention, a dome-shaped reversing portion is provided at the center of the bimetal piece 5 to promote a reversing action when reversing according to temperature. Since the layer 5a is formed, the reversing operation is reliably performed. Note that the support projection 1a is provided on the inner bottom surface of the insulating case 1. Therefore, if the reversing portion 5a does not reverse due to the temperature gradually changing (cooled down) when the temperature decreases, the reversing portion 5a comes into contact with the support protrusion 1a. The contact between the movable contact 6 and the fixed contact 3 is kept in a separated state, and chattering of the contact between the movable contact 6 and the fixed contact 3 during slow cooling can be prevented.

FIGS. 6 and 7 show the structure of a thermally responsive switch according to a second embodiment of the present invention. FIG. 6 is a plan view of a bimetal piece with a movable contact fixed thereto, and FIG. is there. 1 to 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this case, the difference from the first embodiment is that the configuration of the warpage preventing means provided on the bimetal piece 5 is slightly different. That is, in the configuration of the warp preventing means provided on the bimetal piece 5 of the thermally responsive switch according to the second embodiment of the present invention, a downward bent portion 5d is integrally formed on the side end side of the bimetal piece 5. The structure is formed as follows.

The bent portion 5d is formed on a flat plate portion 5c located between the movable contact 6 and the reversing portion 5a by working with a press or the like. Further, the bent portion 5d is formed so as to face the side end of the flat plate portion 5c in a pair. By providing the bent portion 5d on the flat plate portion 5c, it is possible to prevent the flat plate portion 5c from warping due to heat.

According to the configuration of the second embodiment of the present invention described above, when the inverting portion 5a of the bimetal piece 5 is inverted according to the temperature and the movable contact 6 is separated from the fixed contact 3, If for some reason, the reversing unit 5a
Is not inverted, the bimetal piece 5
Since it is possible to prevent the occurrence of warpage due to heat when the temperature rises, it is possible to prevent the movable contact 6 and the fixed contact 3 from being accidentally separated from each other and to prevent chattering between the contacts.

FIGS. 8 and 9 show the structure of a thermally responsive switch according to a third embodiment of the present invention. FIG. 8 is a plan view of a bimetal piece with a movable contact fixed thereto, and FIG. is there. 1 to 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this case, the difference from the first and second embodiments is that the configuration of the warpage preventing means provided on the bimetal piece 5 is slightly different. That is, the third aspect of the present invention
The configuration of the warp preventing means provided on the bimetal piece 5 of the thermally responsive switch according to the embodiment is constituted by an intermediate member 8 interposed between the movable contact 6 and the bimetal piece 5.

The intermediate member 8 is interposed at a fixed portion between the bimetal piece 5 and the movable contact 6 and is formed of a material having relatively low electric resistance, such as Cu (copper) or a Cu alloy. The outer shape of the intermediate member 8 is the same as that of the movable contact 6.
The movable contact 6 and the reversing portion 5
a, and is fixed to the flat plate portion 5c located between them by a method such as spot welding.

Since the intermediate member 8 is interposed in the fixed portion between the bimetal piece 5 and the movable contact 6, the resistance of the fixed portion can be reduced, and the temperature rise in the fixed portion can be suppressed. Thus, a thermally responsive switch with a stable inversion operation can be obtained. Further, by fixing the intermediate member 8 larger than the movable contact 6 to the flat plate portion 5c, it is possible to prevent the flat plate portion 5c from warping due to heat. The shape of the intermediate member 8 is not limited to a circle, and may be formed in a substantially triangular shape (indicated by a two-dot chain line in FIG. 8) on the flat plate portion 5c in accordance with the outer peripheral edge of the reversing portion 5a. .

According to the configuration of the third embodiment of the present invention, when the inverting portion 5a of the bimetal piece 5 is inverted according to the temperature and the movable contact 6 is separated from the fixed contact 3, If for some reason, the reversing unit 5a
Is not inverted, the bimetal piece 5
Since it is possible to prevent the occurrence of warpage due to heat when the temperature rises, it is possible to prevent the movable contact 6 and the fixed contact 3 from being accidentally separated from each other and to prevent chattering between the contacts.

FIGS. 10 to 12 show the structure of a thermally responsive switch according to a fourth embodiment of the present invention. FIG. 10 is a plan view of a bimetal piece with a movable contact fixed thereto, FIG. 12 is a cross-sectional view of the same, 12A is a cross-sectional view taken along line 12A-12A in FIG. 11, and FIG. 12B is a cross-sectional view taken along line 12B-12B in FIG. 1 to 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this case, the difference from the first, second and third embodiments is that the configuration of the warpage preventing means provided on the bimetal piece 5 is slightly different. That is, the configuration of the warp preventing means provided on the bimetal piece 5 of the thermally responsive switch according to the fourth embodiment of the present invention is different from the dome-shaped bulging direction of the reversing portion 5a formed on the bimetal piece 5. Has a configuration in which a curved surface portion 5e protruding to the opposite side is formed.

The curved surface portion 5e is formed by subjecting the flat plate portion 5c of the bimetal piece 5 to processing such as pressing. In this case, the direction in which the curved surface portion 5e protrudes is formed so as to be located on the opposite side to the direction in which the inverted portion 5a bulges in a dome shape. Also,
The curved surface portion 5e may be formed by performing a drawing process in a mortar shape such that the fixed portion of the movable contact 6 becomes a bottom surface.

When the curved surface portion 5e is formed, first, the curved surface portion 5e is formed on the flat plate portion 5c of the bimetallic piece 5 by a method such as drawing, and then the movable contact 6 is connected to the bimetallic piece. 5 is welded by spot welding or the like. After that, the dome-shaped inverted portion 5a is formed on the bimetal piece 5 by a method such as drawing. According to the method for forming the bimetal piece 5, the processing of the curved surface portion 5 e and the fixing of the movable contact 6 are performed before the formation of the inversion portion 5 a. Since there is no fear of affecting the shape of the reversing portion 5a, a stable reversing operation can be obtained. Further, by providing the curved surface portion 5e on the flat plate portion 5c,
Warpage of the flat plate portion 5c due to heat can be prevented.

According to the configuration of the fourth embodiment of the present invention described above, when the reversing portion 5a of the bimetal piece 5 reverses according to the temperature and the movable contact 6 separates from the fixed contact 3, If for some reason, the reversing unit 5a
Is not inverted, the bimetal piece 5
Since it is possible to prevent the occurrence of warpage due to heat when the temperature rises, it is possible to prevent the movable contact 6 and the fixed contact 3 from being accidentally separated from each other and to prevent chattering between the contacts.

[0054]

As described above, the thermally responsive switch according to the present invention comprises a bimetal piece having a dome-shaped reversal portion having a movable contact fixed to one end and reversible according to temperature.
Due to the formation of the warpage preventing means, when the reversing part of the bimetal piece is reversed according to the temperature and the movable contact is separated from the fixed contact, for some reason, even if the reversing part is not reversed, Since it is possible to prevent the occurrence of warpage due to heat when the temperature rises, it is possible to prevent accidental separation between the movable contact and the fixed contact, and to prevent chattering between the contacts.

Further, the warp preventing means is provided such that when the inverted portion of the bimetal piece is inverted according to the temperature and the movable contact is separated from the fixed contact, the movable contact and the fixed contact are not separated if the inverted portion is not inverted. As described above, since the bimetal piece is formed on the flat portion, chattering between the contacts can be prevented with a simple structure.

Further, since the warp preventing means is formed near the movable contact and the reversing portion, it is possible to reliably prevent the warpage due to heat when the temperature rises.

Further, since the warpage preventing means is a rib formed on the bimetal piece, the structure is simple and the cost can be reduced.

Further, since the warp preventing means is a bent portion formed on the side end side of the bimetal piece, the structure is also simple and the cost can be reduced.

Further, since the warp preventing means is constituted by an intermediate member interposed between the movable contact and the bimetal piece, it is possible to reduce costs without increasing the number of steps and parts.

Further, since the intermediate member is formed larger than the outer shape of the movable contact, warpage can be prevented with a simple structure.

Since the intermediate member is formed of Cu and its alloy material, it is possible to cope with the same equipment.

Further, since the warpage preventing means is a curved portion protruding in the direction opposite to the dome-shaped bulging direction of the inverted portion formed on the bimetal piece, warpage can be prevented with a simple structure.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a thermally responsive switch according to a first embodiment of the present invention.

FIG. 2 is a plan view showing the same thermally responsive switch of the present invention.

FIG. 3 is a sectional view showing the same thermally responsive switch of the present invention.

FIG. 4 is a plan view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 5 is a front view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 6 is a plan view showing a bimetal piece to which a movable contact according to a second embodiment of the present invention is fixed.

FIG. 7 is a front view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 8 is a plan view showing a bimetal piece to which a movable contact according to a third embodiment of the present invention is fixed.

FIG. 9 is a front view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 10 is a plan view showing a bimetal piece with a movable contact fixed thereto according to a fourth embodiment of the present invention.

FIG. 11 is a front view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 12 is a cross-sectional view of the bimetal piece of the present invention with the movable contact fixed thereto, and FIG. 12A is a sectional view of FIG.
FIG. 12B is a sectional view taken along line -12A, and FIG.
It is sectional drawing in the -12B line.

FIG. 13 is an explanatory view showing a state of a bimetal piece at a normal temperature of a conventional thermally responsive switch.

FIG. 14 is an explanatory diagram showing a state in which the bimetal piece is inverted when the temperature of the conventional thermoresponsive switch rises.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation case 1a Support projection part 2 First terminal 2a Mounting hole 2b Connection terminal part 2c Opening part 2d Inclined part 3 Fixed contact 4 Second terminal 4a Projection part 4b Connection terminal part 4c Opening 4d Inclined part 5 Bimetal piece 5a Reversing portion 5b Rib (warpage preventing means) 5c Flat plate portion 5d Bent portion (warping preventing means) 5e Curved surface portion (warping preventing means) 6 Movable contact 7 Cover 8 Intermediate member (warping preventing means)

Claims (9)

[Claims] 1. A fixed contact, a movable contact that comes into contact with and separates from the fixed contact, and a bimetal piece having a dome-shaped reversing portion fixed to one end of the movable contact and reversible according to temperature, A thermally responsive switch, wherein a warpage preventing means is formed on the bimetal piece. 2. The warpage preventing means includes: a movable contact that is turned over when the inverted portion of the bimetal piece is inverted according to a temperature and the movable contact is separated from the fixed contact; 2. A thermally responsive switch according to claim 1, wherein said switch is formed on a flat plate portion of said bimetal piece so that said fixed contact and said fixed contact do not separate from each other. 3. The warp preventing means is formed near the movable contact and the reversing part.
The thermally responsive switch as described. 4. The thermally responsive switch according to claim 2, wherein said warpage preventing means is a rib formed on said bimetal piece. 5. The thermally responsive switch according to claim 2, wherein the warp preventing means is a bent portion formed on a side end of the bimetal piece. 6. The thermally responsive switch according to claim 2, wherein said warpage preventing means is constituted by an intermediate member interposed between said movable contact and said bimetal piece. 7. The thermally responsive switch according to claim 6, wherein said intermediate member is formed larger than an outer shape of said movable contact. 8. The thermally responsive switch according to claim 6, wherein said intermediate member is formed of Cu and its alloy material. 9. The device according to claim 2, wherein the warpage preventing means is a curved portion formed on the bimetal piece and protruding in a direction opposite to a dome-shaped bulging direction of the inversion portion. Thermo-responsive switch.