JP2003059378A - Thermostat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive temperature sensitive normal-open switch having stable thermal response and surely operating another power cutoff device in an abnormal condition. SOLUTION: A bimetal 19 is positioned for all directions by fitting a central convex part 16-2 of a base part 16 into the central hole 19-1 of the bimetal 19 and a vertical displacement range of the central part of the bimetal is restricted by a central convex surface 21-1 of a protection cover 21. Terminal parts 19-2, 19-2 in the longer direction abut on the reverse side of the protection cover 21 by setting warpage the direction of which does not contact the terminals 17, 18 (contacts 17-1, 18-1) at a normal temperature. When the ambient temperature reaches a prescribed temperature or over, the bimetal 19 contacts the terminal 17, 18 by reversing the warpage and both terminals are short- circuited. The thermostat 15 is used in combination with a leakage breaker or a current breaker or the like which operates on a small current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to provide a temperature-sensitive switch which is open at room temperature and which is inexpensive and has a stable thermal response and a reliable short-circuiting operation between terminals and a small number of parts.

[0002]

2. Description of the Related Art Conventionally, at home or at work,
Various electric devices are widely used. However, it has been widely known that some electric appliances cause a fire due to an incorrect usage method or forgetting to turn off the power after use.

Therefore, in recent years, most electric devices are internally provided with a safety element such as a current fuse, a temperature fuse, and a thermostat for cutting off a direct power source in order to ensure safety in the event of an abnormality. However, in the case of an element with only one operation, such as a fuse, if the operation is interrupted once, the element becomes unusable, so the element must be replaced. In other words, it will take the form of repairing electrical equipment. However, since this is inconvenient, it is often the case that a thermostat is used, which allows repeated movement.

FIG. 4 is a side sectional view showing an example of a typical thermostat among such conventional safety elements.
As shown in the figure, the conventional thermostat 1 has external terminals 7a and 7b via a base body 2 made of an insulating resin or the like.
And internal terminals 8 and 9 are connected to each other. One end of the metal movable plate 4 is fixed to one of the internal terminals 8, and a fixed contact 11 is provided on the other internal terminal 9 so as to project upward. A movable contact 10 is provided so as to project downward at the other end of the metal movable plate 4 facing the fixed contact 11. A hole is provided in the center of the metal movable plate 4, and the protrusion 12 at the center of the base 2 is fitted into this hole to position the metal movable plate 4. Bimetal engaging portions 5a, 5a are provided in the middle and in the middle of the end of the metal movable plate 4, and the position regulating pieces 5b, 5b (the position regulating piece 5b on the front side is a cross-sectional view, so Invisible) is erected.

The side portions of the bimetal 3 in the lateral direction (depth direction in the drawing) are regulated by the position regulating pieces 5b, 5b, and the bimetal engaging portions 5a are disposed at both ends in the longitudinal direction (horizontal direction in the drawing). 5a, respectively. As a result, when the bimetal 3 is warped upward in a convex shape at room temperature as shown by the solid line in the figure, the metal movable plate 4 is also biased in a convex direction, and the movable contact at the other end is biased. 10
Is pressed against the fixed contact 11 to close the contact portion 6 and the external terminal 7
Conduction is made between a and 7b.

On the other hand, when the bimetal 3 is inverted in a downward convex shape as shown by the broken line in the figure at the time of abnormality, the metal movable plate 4 is also urged in a downward convex direction, and the other end The movable contact 10 is separated from the fixed contact 11 to open the contact portion 6 to cut off the current between the external terminals 7a and 7b.

As described above, in the conventional electric equipment, the safety element itself is supplied with the main current for driving the electric equipment, and the safety element itself functions to cut off the current.

[0008]

By the way, with the recent expansion of the electric capacity, it may be dangerous to simply perform repeated off and on operations as in the above-mentioned thermostat. Therefore, safety is required so that once an abnormal operation is performed, it does not return to the normal operation unless manually reset.

However, the conventional thermostat is
As described above, since the normal load current (main current for driving electric equipment) is cut off by the thermostat itself, in order to energize a large current without interruption during normal energization,
A large-sized contact, which is commensurate with the load current, and a spring member, which secures the contact pressure of this contact and maintains contact reliability, are essential for its structure.

Since the structure is complicated as described above, some thermostat resetting methods are difficult to be manually operated and some problems remain. Also,
Originally, in order to cut off a large current flowing in an electric device, it is more reliable to use a relay or circuit breaker that cuts off the power supply by energizing it, but a simple device for operating these relays or circuit breakers is available. It has never existed before.

In view of the above conventional circumstances, an object of the present invention is to
It is an object of the present invention to provide a temperature-sensitive switch in an open circuit state at room temperature which has a stable thermal response and can operate a relay, a circuit breaker or the like by performing a reliable short-circuiting operation between terminals in an abnormal condition.

[0012]

The structure of the thermostat according to the present invention will be described below. The thermostat of the present invention is a thermostat in an open circuit state at room temperature, comprising a pair of terminals, a base portion for insulating and supporting the pair of terminals, and a bimetal arranged in the base portion, wherein the bimetal is A warp direction is set so as not to contact the pair of terminals at room temperature, and the warp direction is set so as to contact each of the pair of terminals at a predetermined temperature or more at at least one position to short-circuit the pair of terminals. Is configured to invert.

The base portion is provided with a heat conductive cover which comes into contact with a warped end portion of the bimetal when the bimetal is warped in a direction in which the bimetal is not in contact with the pair of terminals. When the bimetal is turned over so as to contact each of the pair of terminals at at least one position, pressure contact is made to the central portion that is convex above the bimetal. Then, it is configured by including a holding portion that limits the reverse displacement space of the bimetal. In this case, the pressing portion may be configured by a projecting portion that is formed in a convex shape downward in the center of the heat conductive cover, as described in claim 4, for example.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 (a) is a plan view showing the structure of the thermostat according to the embodiment.
(b), (c) is the sectional side view, It is a figure which shows an operating state.

As shown in FIGS. 1A and 1B, the thermostat 15 includes a base portion 16 made of an insulating resin and a pair of terminals 17 and 18 insulated and supported by the base portion 16.
And a bimetal 19 arranged in the base portion 16. The terminal 17 has an internal contact 17-1 and an external terminal 17-2, and the terminal 18 has an internal contact 18-1 and an external terminal 18-2.

The bimetal 19 is arranged in the base portion 16, and a hole 19-1 formed at the center of the bimetal 19 is fitted into the central convex portion 16-2 of the base portion 16 to position the front, rear, left and right thereof. Protective cover 2
The upper and lower displacement ranges are restricted by the central convex surface 21-1. The protective cover 21 is a projecting portion 2 on the lower center of both sides.
1-2 is bent inward and is arranged around the bottom surface of the base portion 16. As a result, the protective cover 2
Reference numeral 1 fixes the position of itself by embracing the base portion 16 by the projecting portion 21-2, thereby ensuring the pressing (regulating force) of the central convex surface 21-1.

At room temperature, the bimetal 19 has a warp-back direction, as shown in FIG.
(That is, the internal contact 17-1 of the terminal 17, the same applies to the following) and the terminal 18 (that is, the internal contact 18-1 of the terminal 18 and the same applies to the following) are set so as to be in a non-contact direction. At this time, the longitudinal end portion 19-2 of the bimetal 19
And 19-2 contact the back surface of the protective cover 21.

In the above-mentioned positional relationship between the bimetal 19 and the protective cover 21 at room temperature, the protective cover 21 is provided at an appropriate position so that the warped shape of the bimetal 19 and the reversal characteristic from this shape are not affected. The bimetal 19 can be set to be appropriately pressed. As a result, the longitudinal end portions 19-2 and 19-2 of the bimetal 19 and the back surface of the protective cover 21 are pressed against each other with a moderate force.

The material of the protective cover 21 may be resin, but it is more preferable that it is a material having good thermal conductivity such as metal or ceramic. When the protective cover 21 is made of a material having good thermal conductivity, the bimetal 19 and the protective cover 21 are properly pressed against each other at both longitudinal end portions of the bimetal 19 as described above, so that the bimetal 1 is resistant to an increase in ambient temperature.
It is possible to improve the thermosensitive response of No. 9.

Further, when the bimetal 19 is bent back in the direction in which it is not in contact with the pair of terminals 17 and 18, and the thermostat 15 is in the open state, that is, the bimetal 1
The ends 19-2 and 19-2 of the pair of terminals 9 have a pair of terminals 17 and 1.
8 When separated from each other, one end does not always contact (fix) with either terminal as in the conventional case, and the heat transferred from the outside to the bimetal 19 is protected. The distribution of heat transferred from the outside to the bimetal 19 is always symmetrical with respect to the center, only from both longitudinal end portions in contact with the cover 21 and from the central portion in contact with the base portion 16. There is no large uneven distribution of heat, and this makes it possible to form a temperature-sensitive switch with stable thermal response.

Then, when the temperature around the thermostat 15 exceeds a predetermined temperature, the bimetal 19 reverses the return direction, as shown in FIG. The pair of terminals 17 and 18 are brought into contact with each other at one place to short-circuit them.

In this way, the bimetal 19 forms the pair of terminals 1.
When inverted so as to come into contact with 7 and 18, respectively, as shown in FIG. 6 (c), the bimetal 19 which is convex upward by this inversion is convex to the center of the protective cover 21 and downward convex to the center of the protective cover 21. The projecting portion 21-1 formed on the base plate 21 is pressed to form a pressing portion that limits the reverse displacement space of the bimetal 19.

As described above, the bimetal 19 has a limited displacement space in the central portion which is deformed in an upward convex shape,
It is possible to concentrate the stress due to the inversion displacement, which is inverted downward around this central portion, to the longitudinal end portions 19-2, 19-2, which are the outermost end portions, and thereby the longitudinal end portions 19-2. , 19-2 is stronger than terminals 17 and 18
To ensure contact with terminals 17 and 18.

The contact pressure set by the conventional contact reinforcing spring plate is usually about 10 g, but by controlling the displacement of the center of the reversing bimetal as described above, the pressure exceeding 10 g above is reversed at the time of reversing. It can be generated instantaneously at the contact point with the contact. Therefore, as in this example, the bimetal switch is a normally open switch,
If applied to a system that only needs to pass a momentary small current for shutting down the power when it is closed in an abnormal condition, it will not pass a large main current that operates electrical equipment in normal times, so the thermostat configuration described above , It can be fully utilized as a built-in component of a power shutoff device in the event of an abnormality.

FIG. 2 is a plan view showing the structure of a thermostat according to another embodiment. The thermostat 22 shown in the figure also includes a base portion 23 made of an insulating resin, a pair of terminals 24 and 25 insulated and supported by the base portion 23, and a bimetal 26 arranged in the base portion 23. ing.

Also in this case, in the bimetal 26, the hole 26-1 formed in the center thereof has the central convex portion 23- of the base portion 23.
The front and rear and left and right are fitted by being fitted to the second member 2, and the center portion thus positioned is restricted in the vertical displacement range by the central convex surface 27-1 of the protective cover 27. Further, the protective cover 27 is arranged such that the projecting portions 27-2 at the lower center of both sides are bent inward and wrap around the bottom surface of the base portion 23, and the projecting portion 27-2 holds the base portion 23. The position of the center convex surface 27-1 is fixed so that the center convex surface 27-1 is securely pressed (regulating force).

The terminals 24 and 25 are internal terminals 24-1 and 25-1 arranged in parallel inside the base portion 23, respectively, and the external terminal 24-2 for connecting to an external circuit.
And 25-2, and internal terminals 24-1 and 25
-1 includes a longitudinal end portion 2 of the bimetal 26, respectively.
A plurality of (two) contacts 24-3, 24-3 and 25-3, 25-3 are provided at positions facing 6-2, 26-2. The internal terminals 24-1 and 25-1 provided in parallel may be bare lead wires, for example.

The bimetal 26 of this thermostat 22
Also, as in the case of the thermostat 15 of FIG. 1, at room temperature, the warping direction has a pair of terminals 24 and 25 (that is, the contacts 24-3 and 24-3 of the terminal 24 and the contacts 25-3 and 25- of the terminal 25). (3, the same applies hereinafter) is set in advance so as to be in a non-contact direction. The positional relationship between the bimetal 26 and the protective cover 27 at this time is also the same as in the case of FIG.

In the thermostat 22, when the ambient temperature exceeds a predetermined temperature and the bimetal 26 reverses the warp direction, one longitudinal end portion 26-2 of the bimetal 26 has the parallel terminals 24-. 1 and 2
5-1 is a terminal 24 press-contacted to one of the contacts 24-3 and 25-3, and the other longitudinal end 26-2 thereof is also parallel.
-1 and 25-1 are pressed against the other contacts 24-3 and 25-3 to short-circuit the parallel terminals 24-1 and 25-1 so as to bridge them.

Thus, the thermostat 22 is
At the end of the rectangular bimetal 26 where the displacement is greatest, the parallel terminals are short-circuited at two locations. As a result, the short circuit operates in two locations in parallel, so the bimetal 2
The contact reliability between 6 and the terminals 24 and 25 is improved.

As described above, as shown in the above embodiments, in any case, the bimetal (19 or 26) itself forms the normally open (closed at the time of abnormality) switch with the contact, so that the minimum component configuration is required. Therefore, an inexpensive temperature sensitive switch can be configured.

Further, as described above, the temperature sensitive switch is highly reliable because it is stable and has a stable thermal response and the contact with the contact is surely made. be able to. 3 (a) and (b) are
It is a figure which shows two examples of use of the thermostat of embodiment mentioned above. Figure (a) shows the diagram when applied to a relay. In the relay circuit shown in FIG.
1 and 28-2, an electromagnet 29 connected in series, a normally open switch 31 driven by the electromagnet 29, power lines 28-1, 28-2 and a load side power supply line 32-1,
The electromagnets 2 are also arranged in series between 32-2
Normally closed switches 33-1 and 33-2 driven by 9 are arranged. The thermostat 15 is provided between the electromagnet 29 and the power supply 28-2 in parallel with the normally open switch 31.
(Or 22) is connected.

In this relay circuit, at room temperature, the electromagnet 29 and the power supply line 28-2 are disconnected from each other, as shown in FIG. Then, the power supply line 28-1 and the load side power supply line 3
2-1 is closed by the normally closed switch 33-1 and the power supply line 28-2 and the load side power supply line 32-2 are also closed by the normally closed switch 33-2. Is supplied to.

When an abnormality occurs and the ambient temperature rises and a predetermined temperature abnormality occurs, the thermostat 15 (or 22)
Works. That is, the bimetal is inverted, both external terminals are short-circuited, and the electromagnet 29 is energized. As a result, the normally open switch 31 is closed to maintain the energization of the electromagnet 29, and the normally closed switches 33-1 and 33-2 are opened to supply the power supply lines 28-1 and 28-2 and the load side power supply line 32-. One, three
Cut off between 2 and 2 respectively. Even if the thermostat 15 (or 22) returns to the normal open state, the relay circuit electrically holds itself and keeps the cutoff state until the power is turned off.

As described above, the thermostat of the present invention, which does not normally energize and maintains the open circuit state at room temperature, is combined with a safety device for shutting off power by energizing as shown in FIG. A safety system that avoids situations can be built. As a result, it is possible to accurately ensure safety in the event of an abnormality.

FIG. 3B is a diagram showing an example applied to an earth leakage breaker. As shown in FIG.
1, 34-2 and the load side power supply lines 35-1, 35-2 are connected via interlocking switches 41-1 and 41-2 of the earth leakage breaker 36. Sensing line 37 of this earth leakage breaker 36
Is one of the load side power supply lines (35-1 in the example of FIG. 2B) and the other load side power supply line after passing through the sensor core 38 in the earth leakage breaker (FIG. 2B). In the example of 35-
2) is short-circuited with and the thermostat 15 (or 22) and the resistor 39 are interposed in the sensing line 37,
In the normal state, the disconnection state of the sensing line 37 is maintained.

When an abnormality occurs, the thermostat 15
(Or 22) is closed to generate a pseudo-leakage in the sensing line 37, and the earth leakage breaker 36 operates to interlock the switch 41-1.
41-2 is opened to disconnect the power supply lines 34-1 and 34-2 from the load side power supply lines 35-1 and 35-2, respectively.
Also in this case, even if the thermostat 15 (or 22) returns to the normally open state, the earth leakage breaker 36 electrically holds itself and holds the cutoff state until the power is turned off.

Thus, the thermostat of the present invention is
It works better when used in combination with a circuit breaker that operates with a small current. In addition, in the case of a system that shuts off the power supply by energizing it in this way, or in a system that shuts off the operating current (sensing line current) instantaneously when energized, the operating current for powering off Therefore, the thermostat structure of this example, which does not use members such as large-sized contacts and contact reinforcing springs, which have been conventionally required as the structure of the thermostat, can be sufficiently utilized.

Further, when the contact reinforcing spring is removed from the structure like the thermostat of this example, the weak contact pressure is usually a problem. However, in this example, the bimetal switch structure is a normally open switch. It is only necessary to pass a small current for shutting off the power when closed in an abnormal condition, and not a large main current that normally operates electrical equipment.Therefore, the end of the displacement amount of the bimetal is the largest. Terminal contacts are arranged in the terminal, multiple terminal contacts are provided, both terminals are short-circuited with either end of the bimetal, and the protective cover covers the upper and lower positions of the center of the displacement due to the reversal of the bimetal. The device is configured to maximize the contact force with the terminal contact due to the reversal stress at the outermost part, and to ensure contact during a short circuit. Contact pressure of the problems like becomes groundless.

The combination with the thermostat of the present invention is not limited to the earth leakage circuit breaker, and can be operated in the same manner as described above even if it is combined with a current circuit breaker that operates by an overcurrent. Further, various shapes of the pair of terminals inside for ensuring the short circuit of the thermostat at the time of the abnormality described above are conceivable, and for example, although not particularly shown, a kerf is formed in the middle of which the shape is changed to a ∪ shape. It may be provided, or may be configured by providing two or more protrusions or the like even if it is not parallel as described above. The point is that if the contact force is strongest after the reversal of the bimetal, that is, at the two ends of the longitudinal direction where the displacement is the largest, each terminal is contacted at least at one point, preferably <2 points or more, the contact is made. That is, the short circuit between the terminals becomes reliable, and the reliability of the switch can be improved.

Therefore, for example, a hexagonal bimetal may be configured so as to be short-circuited at three points, or a polygon having another shape may be used. However, it goes without saying that it is preferable to use a shape that is economically highly feasible.

[0042]

As described above in detail, according to the present invention, since the normally open switch is formed by the bimetal itself, it is possible to provide the inexpensive temperature sensitive switch with the minimum component configuration.

Further, since the bimetal is separated from each of the pair of terminals in the open state, there is no uneven distribution of heat in the bimetal, which makes it possible to provide a temperature sensitive switch with stable thermal response. Further, since a plurality of contact points with the bimetal are provided on the terminal side, reliable contact can be obtained even though there is no member for contact reinforcement such as a spring material,
As a result, stable and highly reliable switch operation can be ensured.

[Brief description of drawings]

FIG. 1A is a plan view showing the configuration of a thermostat according to an embodiment, and FIGS. 1B and 1C are side sectional views showing the operating state.

FIG. 2 is a plan view showing a configuration of a thermostat according to another embodiment.

3 (a) and 3 (b) are views showing two examples of use of the thermostat of the embodiment.

FIG. 4 is a side sectional view showing an example of a typical thermostat among conventional safety elements.

[Explanation of symbols]

1 thermostat 2 Base part 3 bimetal 4 Metal movable plate 5a Bimetal engagement part 5b Position control piece 6 contact points 7a, 7b External terminal 8, 9 internal terminals 10 movable contacts 11 fixed contacts 12 Projection 15 thermostat 16 Base part 16-2 Central convex part 17 terminals 17-1 Internal contact 17-2 External terminal 18 terminals 18-1 Internal contact 18-2 External terminal 19 bimetal 19-1 hole 19-2 Longitudinal end 21 Protective cover 21-1 Central convex surface 21-2 Projection part 22 Thermostat 23 Base part 23-2 Central convex part 24, 25 terminals 26 Bimetal 26-1 hole 27 Protective cover 27-1 Central convex surface 27-2 Projection part 28-1, 28-2 Power line 29 Electromagnet 31 Normally open switch 32-1 and 32-2 load side power supply line 33-1 and 33-2 Normally closed switch 34-1, 34-2 Power line 35-1, 35-2 Load side power supply line 36 Earth leakage breaker 37 Sensing line 39 Resistance 41-1 and 41-2 interlocking switch

Claims (4)

[Claims] 1. A pair of terminals, a base portion that insulates and supports the pair of terminals, and a bimetal disposed in the base portion.
A thermostat in an open circuit state at normal temperature, wherein the bimetal has a warp direction set in a direction in which the bimetal is not in contact with the pair of terminals at a normal temperature, and at least one place is provided on each of the pair of terminals at a predetermined temperature or higher. The thermostat, wherein the warping direction is reversed so that the pair of terminals are short-circuited by contacting with each other. 2. The base portion is provided with a heat conductive cover that comes into contact with a warped end portion of the bimetal when the bimetal is warped in a direction in which the bimetal is not in contact with the pair of terminals. The thermostat as claimed in claim 1. 3. The inversion of the bimetal, wherein the base portion is in pressure contact with a central portion of the bimetal which is convex when the bimetal is inverted so as to contact the pair of terminals at at least one position. The thermostat according to claim 1 or 2, further comprising a holding portion that limits a displacement space. 4. The thermostat according to claim 3, wherein the pressing portion is a projecting portion that is formed in a downward convex shape at the center of the heat conductive cover.