JP2001256873A - Heat sensitive switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide structure of a heat sensitive switch using a piece of bimetal capable of easily positioning the piece of bimetal on a stationary terminal and preventing deformation of the piece of bimetal on setting it into a housing. SOLUTION: The switch comprises a housing 1, a stationary contact 3 settled on the inner surface of the bottom of the housing 1, a piece of bimetal 5 having a bending part 5a bendable according to the temperature, to one end of which a movable contact 6 is fixed so as to contact and part from the stationary contact 3, and a stationary terminal 4 to which the other end of the piece of bimetal 5 is fixed in cantilever shape. An extension arm 5b which extends from the fixing part of the stationary terminal 4 in the opposite side of the position of the bending part 5a is formed on the piece of bimetal 5. A coupling holding part 1b which is positioned on the housing 1 by engagement with the extension arm 5b is formed.

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. 7 and 8 show the structure of a conventional thermally responsive switch. FIG. 7 is an exploded perspective view of the thermally responsive switch, and FIG. 8 is a sectional view of the same.

In the figure, a housing 11 is formed of an insulating material such as a synthetic resin in a box shape having an open upper surface.
On the inner bottom surface of the housing 11, a fixed contact 12 and a fixed terminal 13 made of a conductive metal are disposed facing each other with a certain interval.

A bimetal piece 15 having a movable contact 14 fixed to one end thereof is fixed to the fixed terminal 13 in a cantilever manner. The movable contact 14 can be separated from and fixed to the fixed contact 12. They are arranged facing each other.
The bimetal piece 15 has a dome-shaped inverted portion 15a formed at the center thereof, and the inverted portion 15a is formed so that it can be inverted according to a change in temperature.

The bimetal piece 15 is fixed on the fixed terminal 13 by spot welding or the like.
It is formed on the other end side facing the movable contact 14 via 5a. A plate-like cover 16 is attached so as to cover the opening of the housing 11 in which the bimetal piece 15 is stored.

When the bimetal piece 15 is fixed on the fixed terminal 13, the bimetal piece 15 to which the movable contact 14 is fixed is positioned at a predetermined position by using a positioning jig prepared separately. The laser welding was carried out in the state of being held and assembled.

[0009]

However, in the structure of the conventional thermally responsive switch described above, when the bimetal piece 15 is fixed on the fixed terminal 13, it is fixed to one end of the bimetal piece 15. In order to match the mounting positions of the movable contact 14 and the fixed contact 12, a dedicated positioning jig is required, and the assembling process is complicated, so that there is a problem that it is difficult to reduce the cost.

Further, since the bimetal piece 15 is sandwiched by the positioning jig, the reversing portion 15a may be deformed, and there is a problem that the reversing operation of the bimetal piece 15 does not work well. .

Therefore, the present invention solves the above-mentioned problems, and the structure of the thermally responsive switch using the bimetal piece enables the bimetal piece to be easily positioned on the fixed terminal when the bimetal piece is incorporated into the housing. It is another object of the present invention to provide a structure of a thermally responsive switch capable of preventing deformation of a bimetal when assembled.

[0012]

According to the present invention, as a first means for solving the above-mentioned problems, a housing, a fixed contact provided on an inner bottom surface of the housing, and a movable contact which comes into contact with and separates from the fixed contact. A bimetal piece having a reversal portion having a contact fixed to one end side and capable of reversing according to temperature; and a fixed terminal having the other end side of the bimetal piece fixed in a cantilever manner, wherein the bimetal piece is fixed to the bimetal piece. An engagement holding portion that forms an extension arm that extends from a portion fixed to the terminal to a side opposite to a position where the reversing portion is formed, and that is positioned by engaging the extension arm with the housing. Is formed.

As a second means, the extension arm extends in a direction orthogonal to a center line connecting the movable contact and the fixed portion of the fixed terminal and in a plane direction to face each other. And an engagement protrusion with the engagement holding portion is formed on a free end side of the extension arm portion.

As a third means, the engagement holding portion is formed by a groove provided in the housing, and an inner wall surface of the groove is engaged with the engagement projection to form the bimetal piece. Are positioned on the fixed terminal.

As a fourth means, a bent piece is formed on the extension arm portion to hold the bimetal piece when the bimetal piece is incorporated in the housing.

[0016]

1 to 6 show an embodiment of the present invention. 1 is a plan view of the thermally responsive switch with a cover removed, FIG. 2 is a sectional view of the same, FIG. 3 is a plan view of a housing provided with fixed contacts and fixed terminals, FIG. 4 is a sectional view of FIG. Is a plan view of the bimetal piece with the movable contact fixed thereto, and FIG. 6 is a front view of the same.

In the figure, a housing 1 is formed of an insulating material such as a synthetic resin in a box shape having an open upper surface. Terminals to be described later are arranged on the inner bottom of the housing 1, and one end of each terminal is led out from both sides of the housing 1. Also,
At the center of the inner bottom surface of the housing 1, a support protrusion 1a projecting hemispherically from the inner bottom surface is provided.

A rectangular groove 1b is formed at one end of the housing 1. The groove 1b has
An extension arm 5b of a bimetal piece 5 described later is engaged and positioned.

The first terminal 2 is formed of a conductive metal material such as brass in a flat plate shape. At one end of the first terminal 2, a fixed contact 3 formed of a small circular plane exposed on the inner bottom surface of the housing 1 is provided. At the other end of the first terminal 2, A connection terminal portion 2b is provided which is led out from the side surface portion of the housing 1 and connected to a circuit of another electric device or the like.

The first terminal 2 has a wide opening 2c near the fixed contact 3 between the fixed contact 3 and the connection terminal 2b. The opening 2 c is formed on the center line passing through the fixed contact 3 in the longitudinal direction of the first terminal 2, and
In the width direction of the terminal 2, the width of the opening 2 c is formed to be larger than the outer peripheral width of the fixed contact 3.
In addition, the opening 2 c is formed so as to be cut along the outer periphery of the fixed contact 3.

The first terminal 2 is provided with an inclined portion 2d at a portion including the opening 2c. The fixed contact 3 and the connection terminal portion 2 are provided through the inclined portion 2d.
b is connected. The first terminal 2
Is attached to the housing 1, the inclined portion 2 d is embedded and attached to the inner bottom of the housing 1.

The second terminal 4 is also formed of a conductive metal material such as brass into a flat plate shape. A projecting portion 4a is formed on one end side of the second terminal 4 by biasing with a press or the like, and the projecting portion 4a is a welded portion for fixing one end of a bimetal piece described later. Also, this second
The other end of the terminal 4 is provided with a connection terminal portion 4b which is led out from the side surface portion of the housing 1 and is connected to a circuit of another electric device or the like.

The second terminal 4 has a wide opening 4c near the protrusion 4a between the protrusion 4a for fixing a bimetal piece 5 to be described later and the connection terminal 4b. Is provided. The opening 4c is provided in the second
The terminal 4 is formed on a center line passing through the protrusion 4a in the longitudinal direction, and the width of the opening 4c is larger than the width of the protrusion 4a in the width direction of the second terminal 4. It is formed to be large. The opening 4c
Are formed so as to be cut along the outer periphery of the protruding portion 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 described later is fixed via the inclined portion 4d. , And the connection terminal portion 4b. When the second terminal 4 is attached to the housing 1, the inclined portion 4 d is embedded and attached to the inner bottom of the housing 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 stress 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.
It is possible to reduce the influence of external stress on a fixed portion between a bimetal piece and a movable contact, which will be described later, and the fixed contact 3.
The influence on the position displacement of each contact can be reduced,
A thermally responsive switch having stable temperature characteristics 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 buried and attached to the inner bottom of the housing 1. Since 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 housing 1, it is possible to cope with miniaturization. Further, it is possible to prevent flux from entering the inside during soldering.

The bimetal piece 5 is formed by laminating two kinds of metal materials having different coefficients of thermal expansion, for example, a high expansion material made of a material having a high electric resistance and a low expansion material made of a material having a low electric resistance in a plate shape. It is formed by joining. 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 welding. The projection is fixed to the projection 4a provided on the second terminal 4 by a method such as laser welding. In this case, the joint between the second terminal 4 and the other end of the bimetal piece 5 is
Since the partial connection is made only at the protruding portion 4a, not at the entire surface, the operation characteristics are not hindered when the bimetal piece 5 performs an inversion 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, at the other end of the bimetal piece 5, an extension arm extending outward from a position where the bimetal piece 5 is fixed to the second terminal 4 and opposite to the position where the reversing portion 5 a is formed. 5b are formed. The extension arms 5b extend in a direction orthogonal to a center line connecting the movable contact 6 and the fixed portion of the second terminal 4 and in a state in which the extension arms 5b face each other in the plane direction and extend. Is formed. The extension arm 5b
On the free end side, an engaging protrusion 5c bulging in an arc shape is formed on both sides facing each other, and the engaging protrusion 5c is engaged with the inner wall of the groove 1b of the housing 1. Thus, the bimetal pieces 5 are positioned and held in the housing 1.

In this case, the extension arm 5b is
When the bimetal piece 5 is assembled into the housing 1, the bimetal piece 5 is turned over when the bimetal piece 5 is assembled into the housing 1. The deformation of the portion 5a can be prevented, and the assembly can be easily performed. On the free end side of the extending arm portion 5b, an engaging protrusion 5c bulging in an arc shape is formed on both sides facing each other.
Since c is engaged with the inner wall of the groove 1b of the housing 1, the movement of the bimetal piece 5 in the rotation direction can be effectively suppressed, and the positioning accuracy is improved.

A bent piece 5 protruding toward the opening direction of the upper surface of the housing 1 is provided on the extension arm 5b.
d is formed. By forming the bent piece 5d, when the bimetal piece 5 is incorporated into the housing 1, the bent piece 5d can be sandwiched by an installation jig or the like, so that the bimetal piece 5 is not deformed. Incorporation becomes possible, and assembly can be performed easily.

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 the opening of the housing 1 and is provided inside the housing 1. To the terminals 2, 4, the bimetal piece 5, the movable contact 6, the fixed contact 3 and the like.

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 housing 1.

Further, when the temperature falls from this state and returns to the normal temperature, the inversion portion 5a of the bimetal piece 5 returns to the inversion in response to the decrease in the 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 central portion 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 housing 1. Therefore, when the temperature is lowered, if the reversing portion 5a returns without being reversed due to a gradual temperature change (cooling), the reversing portion 5a contacts the support protrusion 1a. The contact makes it possible to keep the contact between the movable contact 6 and the fixed contact 3 in a separated state, thereby preventing chattering of the contact between the movable contact 6 and the fixed contact 3 when the contact is reversed again when the temperature rises. Has become.

[0036]

As described above, the thermally responsive switch of the present invention has a movable contact fixed to and separated from a fixed contact at one end, and is fixed to a bimetal piece having a reversing portion which can be reversed according to temperature. An extension arm portion is formed to extend from a portion fixed to the terminal to a side opposite to a position where the reversing portion is formed, and an engagement holding portion is formed in the housing, where the extension arm portion is engaged and positioned. Therefore, when the bimetal piece is assembled into the housing, deformation of the inverted portion of the bimetal piece can be prevented, and assembly can be performed easily.

The extension arms extend in a direction orthogonal to a center line connecting the movable contact and the fixed portion of the fixed terminal and in a plane direction to face each other. Since the engagement projection with the engagement holding part was formed on the free end side,
The movement of the bimetal piece in the rotating direction can be effectively suppressed, and the positioning accuracy is improved.

Further, the engagement holding portion is formed by a groove provided in the housing, and the inner wall surface of the groove is engaged with the engagement projection to position the bimetal piece on the fixed terminal. Positioning can be performed reliably, and assembly can be performed easily.

Further, since a bent piece is formed in the extension arm portion to be sandwiched when the bimetal piece is incorporated in the housing, the bimetal piece can be incorporated without being deformed, thereby facilitating assembly. be able to.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which a cover of a thermally responsive switch according to an embodiment of the present invention is removed.

FIG. 2 is a cross-sectional view showing a state in which a cover of the thermoresponsive switch of the present invention is removed.

FIG. 3 is a plan view showing a housing of the present invention in which fixed contacts and fixed terminals are also arranged.

FIG. 4 is a cross-sectional view showing a housing of the present invention in which fixed contacts and fixed terminals are also arranged.

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

FIG. 6 is a front view showing the bimetal piece of the present invention with the movable contact fixed thereto.

FIG. 7 is an exploded perspective view showing a conventional thermally responsive switch.

FIG. 8 is a sectional view showing a conventional thermally responsive switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 1a Support projection part 1b Groove part (engagement holding part) 2 First terminal 2b Connection terminal part 2c Opening 2d Inclined part 3 Fixed contact 4 Second terminal (fixed terminal) 4a Projection part 4b Connection terminal part 4c Opening Part 4d Inclined part 5 Bimetal piece 5a Reversal part 5b Extension arm 5c Engagement protrusion 5d Bend piece 6 Movable contact 7 Cover

Claims (4)

[Claims] 1. A bimetal having a housing, a fixed contact disposed on an inner bottom surface of the housing, and a movable contact which is in contact with and separated from the fixed contact at one end, and having a reversing portion which can be reversed according to temperature. And a fixed terminal to which the other end of the bimetal piece is fixed in a cantilever manner, and the bimetal piece extends from the portion where the bimetal piece is fixed to the fixed terminal to the side opposite to the position where the inverted portion is formed. A thermally responsive switch, wherein an extension arm portion is formed, and an engagement holding portion is formed in the housing to engage and position the extension arm portion. 2. The extension arm portion extends in a direction orthogonal to a center line connecting the movable contact and a fixed portion of the fixed terminal and in a plane direction so as to face each other. 2. The thermally responsive switch according to claim 1, wherein an engagement protrusion with the engagement holding portion is formed on a free end side of the arm portion. 3. The engaging and holding part is formed by a groove provided in the housing, and an inner wall surface of the groove and the engaging projection are engaged with each other to place the bimetal piece on the fixed terminal. 3. The thermally responsive switch according to claim 2, wherein the switch is positioned. 4. The thermally responsive device according to claim 1, wherein a bent piece is formed on the extension arm to hold the bimetal piece when the bimetal piece is incorporated into the housing. switch.