JP2002184277A - Thermal protector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin thermal protector preventing chattering or arcing even if the container is made thine. SOLUTION: A fixed electrode element 3 having a fixed contact 2, and a movable electrode element 5 having a thermally actuating element 9 provided so as to attach/detach to/from the fixed electrode element 3 by a snap action are provided in a container 6 having a thickness of not more than 1.2 mm in such a way as to opposite to each other. When the fixed contact 2 and a movable contact 4 are in contact, space distance between a tip end portion of the movable electrode element 5 and a container 6 inner surface becomes from 0.3 mm to 0.4 mm. When the thermally actuating element 9 separates from the fixed electrode element 3 by the snap action, a tip end portion of the separating thermally actuating element 9 abuts on the inner surface of the container 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thermal protector.

[0002]

2. Description of the Related Art A thermal protector is provided in an electric device or a heat source application device, and has a function of detecting overheating or an overcurrent at the time of an abnormality of the device and temporarily interrupting a circuit current to detect an abnormal state of the device. Is a protection element that informs

[0003] There are various types of thermal protectors having different configurations, shapes, dimensions and operating characteristics according to the equipment to be used. Specifically, varieties that have been used for copper-iron ballasts for motors and fluorescent lamps, electronic inverter circuits, and the like, for example, are housed in a container having a thickness of 3.1 mm or 3.9 mm, for example. And has a relatively large shape.

In recent years, the development of portable information devices has been remarkable.
The development of thermal protectors for battery packs used in these portable information devices and the like has been developed and developed. With the development of such portable information devices and the like, the thermal protector for the battery pack used in them has a container There is a demand for downsizing, especially thinning of the shape. this is,
This is because by further reducing the size of the battery pack using the thermal protector, it is possible to reduce the size of a portable information device or the like using the battery pack.

Conventionally, such a small thermal protector 2
As shown in FIG. 9, a fixed electrode body 23 and a movable electrode body 24 which comes into contact with and separates from the fixed electrode body 23 are installed in a container 25 made of PBT resin or the like, as shown in FIG. (Japanese Patent No. 2636615).

The fixed electrode body 23 has a fixed contact 26 at one end.
, A fixed electrode support plate 28 connected to the other end of the contact plate 27, and a fixed electrode side lead wire 29 welded and connected to the fixed electrode support plate 28.

The movable electrode body 24 includes a thermoresponsive element 31 made of bimetal or trimetal having a hemispherical movable contact 30 welded to one end thereof, and a movable electrode support plate 32 connected to the other end of the thermoresponsive element 31. And the movable electrode support plate 3
2 comprises a movable electrode side lead wire 33 which is welded and connected.

[0008] The fixed electrode body 23 and the movable electrode body 24 are integrated by resin beads 34 to form a mount body 35, which is inserted into the container 25 and sealed with a resin filler 36. .

[0009] Such a conventional thermal protector 22
Means that the thermally responsive element 31 of the movable electrode body 23 performs a snap action operation due to a temperature rise due to overheating and overcurrent at the time of equipment abnormality, thereby separating the fixed contact 26 and the movable contact 30 and interrupting the current flowing to the equipment. I do.

The conventional thermal protector 22 includes a container 2
5 is 2.4 mm thick and has a chevron-shaped cross-section, so that a valley can be formed by juxtaposing multiple AA batteries of nickel-cadmium and nickel-hydrogen, which have been the mainstays of the prior art. The battery pack can be accommodated and arranged, and the size of the battery pack can be reduced. In addition, the contact resistance of this conventional thermal protector 22 is extremely low at 20 mΩ or less, and the contact resistance is very stable even after performing the opening and closing operation 5000 times. As a result, the resistance loss of the thermal protector connected in series to the battery pack is low, and a so-called low-impedance battery pack is realized, and the operating time of the battery pack can be prolonged accordingly.

[0011]

In recent years, lithium-ion batteries have been developed and spread as new high-capacity batteries to replace nickel-cadmium and nickel-metal hydride batteries that have been used in the past. The shape of this battery used in mobile phones and the like is mainly rectangular, and the protection element is preferably attached to the side wall surface of the battery, so that it is preferably thin.

On the other hand, as a new protective element for several years,
A so-called PTC thermistor, which is a positive temperature characteristic resistance element made of a conductive resin material, has been developed and commercialized. This PTC thermistor is characterized by an ultra-thin shape with a plate shape and a product thickness of about 0.8 mm, which makes it a widely used alternative to conventional thermal protectors as a mainstay protection element for new lithium-ion battery packs. I have.

By the way, the protection element of the PTC thermistor has an internal resistance which is equal to the contact resistance of the thermal protector.
It has been pointed out from the beginning that it is higher than mΩ or less.
That is, the internal resistance of the PTC thermistor is already as high as several tens mΩ or more as an initial value in a room temperature state before the operation, and the internal resistance may be further increased each time the switching operation is performed. Therefore, when the PTC thermistor is used, the resistance loss increases as compared with the case of the thermal protector, so that a low-impedance battery pack cannot be obtained, and it is inevitable that the use time of the device is shortened. Also, especially in the pulse current operation accompanying the digitalization of mobile phones in the future,
Problems due to the resistance loss of the PTC thermistor, such as the fact that a required pulse current cannot be obtained by limiting the peak current used by the resistance of the battery, are anticipated, and the market is strongly demanding low impedance measures.

The conventional thermal protector for a battery pack is smaller than the original type for motors, electronic circuits, and the like. Is a major issue.

According to the results of market research conducted by the inventor, it has been found that if the thickness of the thermal protector container is 1.2 mm or less, it can be well adapted to equipment for a lithium ion battery pack. However, when the thickness of the container is reduced, the distance between the accommodated fixed electrode plate and the movable electrode plate becomes shorter, so that there arises a problem that chattering and arcing occur.

An object of the present invention is to provide a thin thermal protector which does not cause chattering or arcing even if the thickness of the container is reduced, and is suitable for use in a battery pack of lithium ion or the like. .

[0017]

According to the first aspect of the present invention,
A fixed electrode body having a fixed contact and a movable electrode body having a thermally responsive element provided so as to be able to contact and separate from the fixed electrode body by a snap action operation are opposed to each other and have a thickness of 1.2 m.
m, and when the fixed contact and the movable contact are in contact with each other, the spatial distance between the distal end of the movable electrode body and the inner surface of the container is 0.3 mm or more.
When the thermoresponsive element is separated from the fixed electrode body by a snap action operation, the distal end of the separated thermoresponsive element is in contact with the inner surface of the container.

Thus, it is possible to obtain a thermal protector having an ultra-thin shape in which the thickness of the container 6 is 1.2 mm or less, having extremely low contact resistance, and capable of preventing chattering and arcing.

[0019]

FIG. 1, FIG. 2, FIG. 3 and FIG.
1 shows a thermal protector 1 according to an embodiment of the present invention.

The thermal protector 1 of the present embodiment has a fixed electrode body 3 having a fixed contact 2 and a movable electrode body 5 having a movable contact 4 and performing a snap action operation by heat. Is provided opposite to the fixed electrode body 3 so as to be able to contact and separate from the fixed electrode body 3 by a snap action operation. The fixed electrode body 3 and the movable electrode body 5 are housed in a container 6 made of a hardly soluble PBT resin or the like.

The fixed electrode body 3 comprises a disk-shaped fixed contact 2 (diameter 1.2 mm × thickness 0.2 mm) and a fixed electrode plate 7 (plate thickness 0.2 mm). The fixed electrode plate 7 is provided by a caulking method.
One end of the fixed electrode plate 7 is drawn out of the one end of the container 6 as an external lead plate 8. The fixed electrode plate 7 has a hole (not shown) into which the disk-shaped fixed contact 2 is fitted in advance. The fixed contact 2 is inserted into this hole, and pressure is applied from both sides of the fixed contact 2. It is caulked and fixed.

The movable electrode body 5 has a disk-shaped movable contact 4 (diameter 1.2 mm × thickness 0.2 to 0.25 mm) having a convex curved surface on the contact side with the fixed contact 2 at one end in the same manner as described above. The thermally responsive element 9 (length 7.5 mm × width 3.7) fixed by caulking
The movable electrode support plate 10 is connected and fixed to the other end of the thermoresponsive element 9 by a rivet 11. Here, one end of the movable electrode support plate 10 is drawn out to the outside of the other end of the container 6 as an external lead plate 12. The other end of the movable electrode support plate 10 is provided in the container 6 so as to face the same plane as the fixed electrode body 3. Note that the fixed electrode body 3 and the movable electrode support plate 10 are electrically non-conductive.

The movable electrode body 5 is made of a trimetal of Ni-Mn-Fe / Ni / Ni-Fe or a Ni-Cr-Fe / It is made of a bimetal made of Ni-Fe. The fixed contact 2 and the movable contact 4 are each made of silver. The fixed electrode plate 7 and the movable electrode support plate 10 are made of a copper-nickel-tin alloy.

The container 6 has a resin base 13 in which the fixed electrode plate 7 of the fixed electrode body 3 and the movable electrode support plate 10 of the movable electrode body 5 are integrated by so-called insert molding, and is mounted on the resin base 13 as an upper lid. Resin cover 14-2
Consists of two parts. The inside of the container 6 is filled with air at atmospheric pressure.

The resin base 13 has a rectangular shape (length 1).
0 mm x 4.7 mm in width), the inside is formed to be the hollow portion 15, and the side wall 16 is formed along the outer periphery. The thickness of the bottom of the resin base 13 is 0.1 m.
m. Then, the thermally responsive element 9 of the movable electrode body 5
Is installed so as to be located in the hollow portion 15 in the container 6. On the other hand, the resin cover 14 has a thickness of 0.3 mm and is formed of a rectangular body (length 10 mm × width 4.7 mm).

Generally, in a thermal protector, if the fixed contact and the movable contact are separated from each other, the current flowing through the circuit is cut off. If the distance is too short, the fixed electrode and the movable electrode are continuously opened and closed. Inconveniences such as operation or chattering occur. In particular, the chattering is likely to occur in the region of the slow motion of the movable electrode body. In order to solve such a problem, it is necessary to instantly separate the movable contact and the fixed contact largely by the snap action of the movable electrode body. However, if these contacts are largely separated, the size of the thermal protector itself becomes large. Becomes large, and thinning cannot be expected. In order to prevent chattering and to realize an ultra-thin shape of the thermal protector while maintaining predetermined characteristics as the thermal protector, the inventor moved the tip of the thermally responsive element 9 in the snap action operation. Consideration of the amount limit was made.

As a study method, as shown in FIG. 5, when there is a resin cover 14, and when there is no resin cover 14, as shown in FIG. The moving distance of the distal end of the movable electrode body 5, that is, the moving distance 17 a in which the distal end of the movable electrode body 5 abuts against the inner surface of the resin cover 14 and the separation movement is suppressed, and the case where the resin cover 14 is not provided. The free moving distance 17b was measured and examined.

As a result of this measurement, in the state before the snap action operation, that is, in the state where the fixed contact 2 and the movable contact 4 are in contact with each other, the tip of the movable electrode body 5 having the thermoresponsive element 9 and the resin cover 14 Distance g to the inner surface of
It has been found that chattering can be prevented if the distance (see FIG. 4) is at least 0.3 mm or more, preferably 0.35 mm or more. However, this spatial distance g is 0.3 m
If it is less than m, it is difficult to obtain a normal snap action operation, and if this space distance g is large, it is not possible to achieve a reduction in thickness, and the thermally responsive element 9 performs a gradual operation when returning. Therefore, the spatial distance g is preferably in the range of 0.3 mm or more and less than 0.4 mm from the viewpoint of suppressing the slow motion as much as possible. At this time, it is necessary that the tip of the thermo-responsive element 9 is in contact with the inner surface of the resin cover 14 in the fast-moving operation region of the thermo-responsive element 9. This is because, as the thickness of the container 6 is reduced, the distance between the fixed electrode body 3 and the movable electrode body 5 becomes short, and chattering easily occurs.
That is, in the fast-moving operation region of the thermal response element 9, the distal end portion of the thermal response element 9 is in contact with the inner surface of the resin cover 14, so that the separating operation is suppressed, that is, the thermal response element 9 should be opened originally. The position is regulated without opening to the position, and at this time, a force is generated in the thermally responsive element 9 to further separate it toward the resin cover 14 side, so that it does not move to the fixed electrode body 3 side and chattering can be prevented. It is.

In general, the operation of a movable electrode body in a thermal protector having a thermally responsive element is such that the displacement of the thermally responsive element gradually increases with an increase or decrease in temperature before the fixed contact and the movable contact are separated or come into contact with each other. Alternatively, a gradually decreasing operation is always performed, and thereafter, when a predetermined temperature is reached, separation or contact is performed by a so-called fast operation by a snap action operation.

In the present invention, the slow motion performed by the thermally responsive element 9 is suppressed as much as possible, and only the fast motion is performed as much as possible. In other words, the thermally responsive element 9 performs the slow motion operation by positioning the fixed contact 2 of the fixed electrode body 3 in the fast movement area near the point where the thermally responsive element 9 switches from the slow motion to the fast motion. The snap action operation is immediately performed at a predetermined temperature without a gap, and the gap is instantaneously separated. In addition, by shortening the space distance g between the tip of the movable electrode body 5 and the inner surface of the resin cover 14 of the container 6 to the limit as described above, the separated thermally responsive element 9 moves slowly when returning. The operation is suppressed as much as possible, and a snap action operation is immediately performed at a predetermined temperature to return.
As a result, chattering can be prevented, and a thin thermal protector can be obtained.

In the thermal protector 1 of the present embodiment, the spatial distance g is 0.35 mm, so that the spatial distance g is smaller than that of the conventional thermal protector 23 shown in FIG. It can be reduced by 0.15 mm.

Further, by making the contact surface of the fixed contact 2 in the fixed electrode body 3 substantially flush with the surface of the fixed electrode plate 7 without protruding from the surface of the fixed electrode plate 7, the fixed contact 26 in the conventional thermal protector 22 can be formed. Contact plate 2 on contact surface of
7 The height of protrusion from the surface of 0.2 mm can be reduced.

As described above, according to the present embodiment, the spatial distance g is 0.35 mm, the thickness between the contact surface of the fixed contact 2 and the bottom surface of the resin base 13 is 0.3 mm, and the movable contact 4 Since the sum of the three values obtained by adding the maximum value of the thickness of 0.25 mm is 0.9 mm, the thickness of the resin cover 14 is added to 0.3 mm, and finally the thickness of the container 4 becomes 1. 2
Thus, it is possible to obtain an ultra-thin thermal protector 1 having a thickness of mm.

The thermal protector 1 of the present embodiment
In this case, a value of 10 mΩ was obtained as the contact resistance, and the characteristic in terms of the original performance that the contact resistance was extremely low was maintained. The operating temperature and the return temperature can be arbitrarily set within the range of 60 ° C. to 100 ° C., for example, 70 ± 5 ° C., by changing the configuration of the punching process of the thermoresponsive element 9. it can.

Further, the thermally responsive element 9 is provided with a rivet 11 on a movable electrode support plate 10 insert-molded on a resin base 13.
Thus, the thermal protector 1 can withstand 20,000 times of opening / closing operations, far exceeding the life standard value of 5000 times of the thermal protector, whereby the highly reliable thermal protector 1 can be obtained. In this case, the rivet connection / fixing portion 18 between the movable electrode support plate 10 and the thermally responsive element 9 is bent toward the hollow portion 15 corresponding to the rivet method. This allows
The end face of the rivet 11 on the fixed electrode body side can be prevented from protruding from the outer surface of the resin base 13 and insulation can be achieved.

The fixed electrode body 3 and the movable electrode support plate 10
Are provided on the resin base 13 so as to face each other on the same plane. On the ends where the fixed electrode body 3 and the movable electrode support plate 10 are close to each other, a resin bar 19 covering each end is provided. Is provided. The resin bar 19 serves as a pressing member between adjacent ends of the fixed electrode body 3 and the movable electrode support plate 10, as well as insulating walls between these ends and the fixed electrode body 3 and the movable electrode support plate 10. Is provided on a step of 0.1 mm formed at an end which is close to each other, and functions as a so-called spacer for insulating the thermally responsive element 9 from the fixed electrode body 3.

In the ultra-thin thermal protector 1 of the present embodiment, the distance between the fixed electrode plate 7 of the fixed electrode body 3 and the thermally responsive element 9 of the movable electrode body 5 is too small, so that the thermally responsive element in an abnormal state In the opening / closing operation of No. 9, the occurrence of an arcing phenomenon or a dielectric breakdown phenomenon between them was feared. Therefore, by providing the above-mentioned step and keeping the interval between them at a specified value, it is possible to prevent the arcing phenomenon or the dielectric breakdown phenomenon from occurring.

In the present embodiment, the thickness of the resin cover 14 is 0.3 mm, but as shown in FIG. 7 or FIG.
May be formed in a stepped shape or a curved shape, and the thickness may be gradually reduced from 0.3 mm to 0.15 mm. Further, even if the thickness of the resin covers 20 and 21 is partially reduced to 0.15 mm, which is the minimum thickness, the resin covers 20 and 21 can withstand the impact due to the contact of the thermally responsive element 9 due to the snap action operation, and the problem such as breakage occurs. Has been confirmed not to.

As a result, the distance between the inner surface of the resin cover 14 and the movable electrode body 3 can be further reduced, and the thickness of the container 6 of the thermal protector 1 can be further reduced by 0.15 mm. The thickness of the container 4 is 1.05m
m, an ultra-thin shape intended for the present invention,
The thermal protector 1 equivalent to the thickness of the C thermistor can be obtained.

The thermal protector 1 of this embodiment is provided in contact with the surface of a rectangular lithium ion battery or the like housed in a battery pack container (not shown).

As described above, the thermal protector of the present embodiment has an ultra-thin shape in which the thickness of the container 6 is 1.2 mm or less, for example, 1.05 to 1.2 mm, and the contact resistance is extremely small. It is low and can prevent chattering and arcing.

[0042]

As described above, according to the present invention, an ultra-thin container having a thickness of 1.2 mm or less, for example, 1.0 to 1.2 mm is achieved, and the contact resistance is extremely low. The features are retained, and a thermal protector that can be adequately adapted for a battery pack such as a new lithium ion can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a sectional plan view of the same.

FIG. 3 is a cross-sectional front view of a resin base in which metal parts are insert-molded.

FIG. 4 is a sectional front view similarly showing a spatial distance g.

FIG. 5 is a sectional front view showing a spatial distance g when a resin cover is provided.

FIG. 6 is a sectional front view showing a spatial distance g when no resin cover is provided.

FIG. 7 is a sectional front view showing another shape of the resin cover.

FIG. 8 is a sectional front view showing another shape of the resin cover.

FIG. 9 is a cross-sectional front view showing a conventional thermal protector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal protector 3 Fixed electrode body 5 Movable electrode body 6 Container 7 Fixed electrode plate 9 Thermal response element 10 Movable electrode support plate 11 Rivets 13 Resin base 14 Resin cover 15 Hollow part 19 Resin beam

Claims (5)

[Claims] 1. A fixed electrode body having a fixed contact and a movable electrode body having a thermally responsive element provided so as to be able to contact and separate from the fixed electrode body by a snap action operation, and have a thickness of 1.2 mm or less. When the fixed contact and the movable contact are in contact with each other, the spatial distance between the tip of the movable electrode body and the inner surface of the container is 0.3 mm or more and 0.4 mm or less. A thermal protector, wherein when the thermoresponsive element is separated from the fixed electrode body by a snap action operation, a distal end portion of the separated thermoresponsive element is in contact with an inner surface of the container. 2. The thermal protector according to claim 1, wherein a contact surface of said fixed contact and a surface of said fixed electrode body are provided on substantially the same plane. 3. The container includes a resin base and a resin cover serving as an upper lid of the resin base, and a thickness of the resin cover in a portion facing the movable contact and in the vicinity thereof is the resin cover. The thermal protector according to claim 1, wherein the thermal protector is formed to be thinner than the thickness of other portions of the thermal protector. 4. The thermal protector according to claim 1, wherein the heat responsive element and a movable electrode support fixed to a resin base are fixed by rivets. 5. The apparatus according to claim 1, wherein a spacer is provided between said fixed electrode body and said thermoresponsive element.
The thermal protector according to claim 4.