JP5578922B2 - Temperature protection element - Google Patents

Description

  The present invention relates to a temperature protection element that uses bimetal to turn on and off between circuit contacts, and more particularly to a temperature protection element that maintains an off state during bimetal operation until the abnormality is eliminated by heat generation of an energization heating element.

  Conventionally, it is well known to use a bimetal as a circuit interruption element. For example, in order to stop charging when the temperature rises due to charging, there is an overcharge prevention circuit protection element that turns off the bimetal thermostat and at the same time provides a heating element in parallel with this to prevent the thermostat from returning. A battery pack using a circuit protection element is known. The battery pack disclosed in Patent Document 1 has a built-in heating resistor that heats the thermal shutdown element in the cutoff state in parallel with the bimetallic thermostat of the thermal shutdown element, and the Joule heat of the heating resistance is combined together. The built-in thermal shut-off element is heated to prevent recovery.

  As an improvement plan for a battery pack safety device incorporating a thermal shutdown element and a heating resistor, Patent Document 2 provides a movable arm between terminals, and this movable arm is operated by a bimetal, and at the same time, PTC is used in combination with the heating element. Disclosed is a safety device that brings a movable arm, a bimetal, and a PTC into a conductive state with a base-side terminal in an off state during shut-off. In the safety device using the bimetal, the movable arm serves as an energization path between the terminals in a normal state, and the bimetal and the PTC are not connected on the electric circuit. On the other hand, when the ambient temperature rises and the bimetal reverses, the movable arm is pushed up, the contact is opened, and at the same time, the circuit is switched to an electric circuit that supplies current to the PTC through the inverted bimetal, and the PTC generates heat until the power supply voltage decreases. Holds the inverted state of the bimetal.

Patent Document 1: JP 07-153499 A Patent Document 2: JP 2005-203277 A

  The safety device disclosed in Patent Document 2 complicates the circuit configuration to use the movable arm, and in addition to the heat generated by the PTC when the bimetal is operated, the energization heat due to the relatively high resistance of the bimetal itself, and the movable arm and the bimetal. And heat generated by contact resistance between the two. Therefore, undesired heat generation is transferred to the movable arm and becomes overheated. Further, the overheating of the movable arm causes the insulating case that accommodates these components to thermally deform. In particular, in order to prevent thermal deformation of the cover made of PLATCH on the movable arm, it is necessary to form and incorporate a thin metal plate on the inner surface of the cover in advance, and it is necessary to shield the case cover from the heat of the movable arm. It was. As described above, in addition to the movable arm, there are disadvantages in terms of cost associated with an increase in the number of parts and the complexity of the assembly work, such as accessory parts such as a metal thin plate for preventing arm overheating and processing on the assembly structure.

  Therefore, the object of the present invention is proposed in order to eliminate the above-mentioned drawbacks, and it is not desired to reduce the cost by reducing the number of parts used and to turn off (separate) the thermal shut-off element after the bimetal is activated. It is an object of the present invention to provide a new and improved temperature protection element having a function of preventing energization heat generation on a circuit and maintaining a PTC of a heating element appropriately in operation.

  The temperature protection element according to the present invention accommodates the bimetal of the thermal shutdown element and the PTC of the heating element in an insulating case provided with contacts on a pair of terminals. In the temperature protection element that keeps the bimetal off by operating in an off state that sometimes breaks the terminal contacts and generating heat by energizing the PTC in the event of an abnormality, the bimetal is a conductor on the tip side. Is provided, and the two contacts of the pair of terminals are bridge-connected by a conductor provided on the bimetal distal end side to be turned on. That is, a first contact provided at the first terminal, a second contact provided at the second terminal, a PTC connected to the first terminal, and a second terminal connected to the PTC via a bimetal, or The bimetal has either a bimetal fixed to the second terminal connected to the PTC, and the bimetal has a conductor in which a conductive path connecting the first and second contacts is formed by a contact material on the tip side. The temperature protection element is packaged by an insulating case and an insulating cover except for the lead-out portions of the pair of terminals. If necessary, the first terminal is provided with a third contact for connection with one electrode terminal of the PTC, and the second terminal is provided with a branch for connection with the other electrode terminal of the bimetal and the PTC. Are fixed together. Here, in the on state of the bimetal, the main circuit formed by the first terminal, the first contact, the conductor, the second contact, and the second terminal is energized between the pair of terminals, and the normal on state is maintained. . On the other hand, in the off state of the bimetal, the energization heating circuit formed from the first terminal-PTC-bimetal-second terminal or the first terminal-PTC-second terminal is energized. The off state is maintained. Bimetal and PTC are housed in a case with an insulating cover to protect the components. The bimetal is a conductor and bridges between the first contact and the second contact when normal, and the first contact and the second contact are separated by the reversal action of the bimetal when abnormal. In the normal state, a main circuit is formed which energizes between the two terminals via the conductor. In the abnormal state, the temperature protection element is switched to the energization heat generation circuit via the PTC.

  According to the present invention, the normal current flows from the first contact provided at one terminal to the second contact provided at the other terminal by the bridge connection of the low resistance conductor provided at the bimetal. The current and the higher resistance bimetal and PTC are not energized, and the power loss due to the energization heating circuit is minimized. On the other hand, when the temperature rise at the time of abnormality is detected, the first contact and the second contact are separated by the reversing operation of the bimetal, and switching is performed so that a current flows mainly through the energization heat generation circuit to the PTC. As described above, the temperature protection element of the present invention has a current flowing on the high resistance side using the electrical resistance difference between the low resistance conductor provided on the bimetal tip side and the higher resistance bimetal itself or PTC. Thus, even when the terminal, the bimetal, and the PTC are in contact with each other at normal times, they can function normally.

  In the temperature protection element of the present invention, since the conductor connecting the pair of terminals is provided at the tip of the bimetal, the electric resistance of the main circuit in the normal state can be reduced and the power consumption can be minimized. Furthermore, excessive resistance heating of the bimetal can be prevented by not energizing the bimetal itself at the time of abnormality or by minimizing the energization distance. For this reason, it is not necessary to take measures against energization overheating of the bimetal on the component parts, and the component parts can be simplified, so that the economic effect is great. In particular, with a pair of bimetal terminals as a specific structure, the contacts on both sides are placed close to each other and the conductor provided on the bimetal is used as a common contact point for mounting, reducing the number of components used, thereby facilitating assembly. This contributes to a reduction in man-hours and can provide a low-cost temperature protection element.

It is a disassembled perspective view which shows the principal part structure of the temperature protection element of Example 1 which concerns on this invention. Similarly, FIG. 2A shows the temperature protection element of FIG. 1, FIG. 2A is a front view of the insulating case body side excluding the cover, FIG. 2B is a cross-sectional view in a normal on state, and FIG. It is sectional drawing in an OFF state. FIG. 3A is a front view of the insulating case main body side excluding the cover, and FIG. 3B is a cross-sectional view and a diagram in the normal on state. FIG. 3C is a cross-sectional view in an off state at the time of abnormality. It is a disassembled perspective view which shows the principal part structure of the temperature protection element of Example 2 which concerns on this invention. FIG. 5 (a) is a front view of the insulating case main body side excluding the cover, FIG. 5 (b) is a cross-sectional view in the normal on state, and FIG. 5 (c) is an abnormal state. It is sectional drawing in an OFF state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show a temperature protection element 10 according to a first embodiment of the present invention, which includes an insulating case 12 provided with a pair of lead-out terminals 11. Insulating case 12 is made of polyamide, polyacetal, polycarbonate, polybutylene terephthalate, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyarylate, polyetherimide, polymethylpentene, liquid crystal polymer, fluororesin Engineering plastics such as these are molded into plastic casings that enclose each terminal by injection molding. The insulating case 12 includes a first terminal 11-1 and a second terminal 11-2. Each terminal formed in advance is integrally formed in the insulating case by injection molding, and the terminals are connected in the insulating case. The electrode portion for use is exposed. That is, as shown in FIG. 1, four parts including a processed part in which a pair of terminals 11 are integrated in an insulating case 12, an insulating cover 19 covering the opening of the case, a PTC 22 housed in the insulating case 12, and a bimetal 25. Consists of The bimetal 25 provided with the conductor 26 at the front end is connected and fixed at the electrode portion 13 whose rear end is connected to the second terminal 11-2, and the PTC 22 is connected to the first terminal so that the lower surface thereof is connected to the first terminal. An electrode portion (third contact) 14 is provided at 11-1. Furthermore, in order to form a main circuit, the electrode part 15 and the contact 17 are provided in the 1st terminal 11-1, and the electrode part 16 and the contact 18 are provided in the 2nd terminal 11-2. These contacts 17 and 18 are disposed so as to be in contact with the conductor 26 of the bimetal 25 and turn on and off the main circuit. PTC22 which has an electrode on both surfaces is installed so that it may connect with the electrode part (3rd contact) 14 and the bimetal 25 of the 1st terminal 11-1. Thereby, the PTC 22 is arranged and connected between the first and second terminals. On the upper and lower surfaces of the PTC 22, for example, electrodes made of a simple substance or a composite such as Ag, Zn, Ni, and carbon are applied. Although not shown, it is preferable to provide a contact protrusion on the lower surface of the bimetal for the purpose of press-contacting the bimetal and the PTC electrode when the bimetal is reversed. Note that the conductor 26 serving as an electrical connection path for the bimetal 25 may be any conductive material having a lower electrical resistance than the material of the bimetal body, such as Cu, Ag, Au, Cu alloy, Ag alloy, and Au alloy. The metal material can be selected from various metal materials, and the selected material is bonded and fixed, or the contact material is clad or plated. After the PTC 22 and the bimetal 25 are assembled in the insulating case 12, the insulating cover 19 is put over the opening, and the insulating case opening is covered with the insulating cover 19 and packaged. In the first embodiment, as shown in FIG. 2B, by providing a pressing portion 19-1 inside the insulating cover 19, the initial deformation of the bimetal is restrained and the bimetal chattering operation is suppressed.

  FIG. 3 shows a modification of the temperature protection element 10 according to the first embodiment of the present invention. In the temperature protection element 10, a pressing portion is provided on the inner side of the insulating cover, but the modification is different in that the inner side of the insulating cover is formed flat as shown in FIG. The temperature protection element of the modification performs suppression of chattering operation and fine adjustment of the reversal temperature by laser processing a part of the bimetal surface in the assembly process. In the above modification, the contact protrusion 25-1 may be provided on the inner side of the concave surface of the bimetal 25 for the purpose of pressing the bimetal and the PTC when the bimetal is reversed.

  4 and 5 show the temperature protection element 30 of the second embodiment according to the present invention, but detailed description of the same structure as that of the first embodiment will be omitted. In the first embodiment, the insulating case main body is processed together with the terminal parts, whereas in this second embodiment, a pair of terminals are also cited as constituent parts, which are composed of six parts as shown in FIG. The That is, the insulating case 32 and the insulating cover 33 are molded into a predetermined shape, and the first terminal 31-1 and the second terminal 31-2 are prepared by sheet metal processing into a predetermined shape. The PTC 42 and the bimetal 45 are accommodated in a package including the insulating case 32 and the insulating cover 33. Each of the pair of terminals 31 is provided with a contact point 37 and a contact point 38. The on / off operation between these contacts is performed by the operation of the conductor 46 provided at the tip of the bimetal 45 as in the first embodiment. Further, the PTC 42 is disposed between the pair of terminals 31 and is in contact with each other to form an energization heat generation circuit, as in the first embodiment. In this embodiment, a rectangular PTC 42 is disposed in a sandwiched state on each planar portion of the first terminal 31-1 and the second terminal 31-2 facing it. The conductor 46 provided on the front end side of the bimetal 45 is disposed so as to be openable and closable between the first contact 37 and the second contact 38, and the rear end side of the bimetal 45 is connected to the second terminal 31-2. Join and fix to the top surface. The conductor 46 may be a conductive material having an electric resistance smaller than that of the bimetal material as in the first embodiment, and is selected from metal materials such as Cu, Ag, Au, Cu alloy, Ag alloy, and Au alloy. .

  In the above-described embodiments, the low-resistance conductor applied to the bimetal may be partially provided on the entire surface of the bimetal or a part where electrical contact is required by film formation such as plating. When the body is provided, it is preferable to resistance-weld a low-resistance single material or a clad material to the corresponding portion. Further, the terminal or bimetal contact surface of the portion facing the upper surface of the rectangular plate-like PTC may be formed entirely or partially by cladding or plating. The conductor provided on the bimetal is preferably provided with a barrier layer such as Ni on the interface with the bimetal so that the composition of the low-resistance conductive material and the bimetal material do not mix with each other due to diffusion or the like. In addition to this, the conductor is a bimetal that is used by applying a conductive paint using at least one conductive material selected from Cu, Ag, Au, Cu alloy, Ag alloy, and Au alloy as a conductive filler to the bimetal arm. A film having a resistance lower than that of PTC may be formed.

  In the temperature protection element of Example 1 in FIG. 2, the insulating case 12 was produced by injection molding of a liquid crystal polymer. Further, the copper material is exposed on the inner side of the casing of each electrode portion of the connection electrode and the contact electrode with the bimetal or PTC of the terminal. Specifically, the first terminal 11-1 in the insulating case 12 is provided with a first contact 17 and a third contact 14 made of an Ag—Ni alloy material, and is positioned at the center of the PTC insertion hole 22-1. The third contact 14 and the disk-shaped ceramic PTC 22 are in contact with each other. Furthermore, the electrode part 13 which joins the bimetal 25 which contacts the upper surface of PTC22 to the 2nd terminal 11-2 is provided with the Ag-Ni alloy material. The insulating cover that covers the opening of the insulating case is also made of a liquid crystal polymer. The conductor 26 used in Example 1 is provided with a tape-shaped crossbar contact material at a predetermined position of the end of the bimetal by projection welding. When the protection element of this embodiment detects an abnormal temperature, as shown in FIG. 2 (c), the end of the bimetal 25 is moved by the operation of reversing the bimetal, and the conductor 26 is connected to the first contact 17 and the second contact. The connection of the contact 18 is released. As a result, switching is performed so that current flows exclusively through the energization heat generation circuit of the PTC 22. For an overcurrent, when the current value exceeds the energization capacity of the conductor 26 installed at the end of the bimetal, the bimetal reversely operates due to resistance heat generation of the conductor. The energization heat generation circuit that passes through the PTC 22 operates after being turned off by the opening due to the operation, and the self-heating of the bimetal arm stops at that time.

  In the modification of the first embodiment, as shown in FIG. 3B, the inside of the liquid crystal polymer insulating cover is formed flat. Further, a contact protrusion 25-1 is provided on the inner side of the concave surface of the bimetal 25, and the bimetal is pressed against the ceramic PTC 22 during operation to improve the contact property. Other configurations and operating principles are the same as those in the first embodiment, and are therefore omitted.

  In the temperature protection element of Example 2 in FIG. 5, the insulating case 32 and the insulating cover 33 are molded with a liquid crystal polymer insulating material. A rectangular plate-shaped ceramic PTC 42 is sandwiched between a pair of formed copper terminals 31 inside the case, the PTC 42 is brought into contact with the first terminal 31-1 and the second terminal 31-2, and The bimetal 45 is joined to the upper part of the two terminals. The contacts 37 and 38 of each terminal 31 are made of an Ag—Cu alloy material, and the conductor 46 provided at the tip of the bimetal 45 is also made of an Ag—Cu alloy material. The opening of the insulating case 32 is covered with an insulating cover 33, and both are fused. The conductor 46 used in Example 2 is provided with a tape-like crossbar contact material at a predetermined position at the end of the bimetal by projection welding. When the temperature protection element 30 of the second embodiment detects an abnormal temperature, as shown in FIG. 5C, the conductor 46 opens the first contact and the second contact by reversing the bimetal. To do. As a result, a current flows through the energization heat generation circuit that exclusively energizes the PTC 42. On the other hand, for the overcurrent, when the current value exceeds the current carrying capacity of the conductor provided at the end of the bimetal, the bimetal 45 is reversed by the resistance heat generation of the conductor, thereby opening both the contacts. Since it switches to the energization heat generation circuit which passes through PTC42 after an operation | movement, the self-heating of a bimetal stops at that time.

  The temperature protection element of the present invention is used for preventing overheating of electric / electronic circuits, and is particularly useful as a protection element for preventing overcharge of secondary batteries.

10, 30 ... temperature protection element, 11, 31 ... terminal,
11-1, 31-1 ... Terminal 1,
11-2, 31-2 ... Terminal 2,
12, 32 ... Insulating case 19, 33 ... Insulating cover,
13 ... Bimetal electrode part, 14 ... PTC electrode part (third contact),
15 ... 1st contact electrode part, 16 ... 2nd contact electrode part,
17, 37 ... 1st contact, 22, 42 ... PTC,
18, 38 ... second contact, 25, 45 ... bimetal,
26, 46 ... conductor, 19-1 ... bimetal pressing part,
22-1 ... PTC insertion hole, 25-1 ... contact protrusion.

Claims (2)

A first terminal having a first contact, a PTC connected to the first terminal, a second terminal having a second contact and connected to the PTC, and a conductor made of a contact material and fixed to the second terminal. A bimetal, an insulating case and a cover for storing the bimetal and the PTC, the first metal contact and the second contact are bridge-connected by the conductor of the bimetal, and the first contact is formed by an inversion action of the bimetal. A temperature protection element that disconnects the connection between the second contacts and switches between an energization heating circuit that energizes the PTC and a main circuit that energizes between both terminals via the conductor, the conductor comprising the bimetal A temperature protection element characterized by being a metal material selected from the group consisting of Cu, Ag, Au, Cu alloy, Ag alloy, and Au alloy, which has a lower electrical resistance than the material . The conductor provided on the bimetal is characterized in that a Ni barrier layer is provided on the boundary surface with the bimetal so that the composition of the low-resistance conductive material and the bimetal material do not mix with each other due to diffusion or the like. The temperature protection element according to claim 1.

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