JP2008071828A - Ptc element and battery protection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PTC element for effectively preventing thermal deterioration of an element body on the occasion of bonding of an electrode plate and a terminal plate with the welding process or the like even when only the electrode plate is formed thinner and for realizing reduction in thickness and weight while effectively utilizing natural functions of the elment itself. <P>SOLUTION: The PTC element includes an element body 4 that increases a resistance value with increase of temperature in the predetermined temperature region and a pair of first electrode plate 10 and a second electrode plate 12 bonded at the front and rear surfaces of the element body 4. At least the first electrode plate 10 among the above electrode plates includes a first element bonding piece 10a bonded to the element body 4 and a first terminal bonding piece 10b integrally formed to the first element bonding piece 10a and extended to the external side of the element body from the first element bonding piece 10a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PTC element used for the purpose of protecting a battery or an electronic circuit from an overcurrent, and a battery protection system having the PTC element.

  A PTC (positive temperature coefficient) element has a characteristic that the resistance value of the element increases when the temperature of the element rises in a predetermined temperature region. Such a property is called a PTC characteristic.

  The PTC element is incorporated in an electric circuit such as an electronic device. If an excessive current flows in the circuit for some reason during use of the electronic device, the temperature of the electronic device rises, and the temperature of the PTC element itself rises accordingly. When the temperature of the PTC element reaches the melting temperature of the polymer, the resistance value of the PTC element increases rapidly. As a result, in the electric circuit, the PTC element cuts off the excess current, and thus it is possible to prevent the electric device from being damaged by the excess current.

  Thus, the PTC element is used as a safety protection device against overheating and excessive current. Specifically, the PTC element is incorporated in a circuit (protection circuit) for protecting a secondary battery that is a power source of the mobile phone from overcurrent. When an excessive current flows during charging or discharging of the secondary battery, the PTC element cuts off the current and protects the secondary battery.

  An example of such a PTC element is a structure in which an element body (polymer positive temperature coefficient resistor) in which conductive particles are dispersed in a polymer material (crystalline polymer) is sandwiched between electrode plates (or metal foils). There is known a polymer PTC element having a thickness (see Patent Document 1).

  Such a polymer PTC element is usually produced by the following method. First, a polymer (such as high-density polyethylene) containing a conductive filler such as metal particles and carbon black is extruded to form an element body. And a polymer PTC element is completed by carrying out the thermocompression bonding of the electrode plate to the front and back of the element body.

  When the polymer PTC element is incorporated in a predetermined protection circuit, an electrode plate that is thermocompression bonded to the element body is joined to a terminal plate that is electrically connected to the protection circuit. This joining is conventionally performed by soldering, welding, or the like.

  When performing soldering, welding, etc., it is necessary to heat at least a part of the electrode plate and the terminal plate to a high temperature. For this reason, heat applied to the electrode plate during soldering and welding is conducted to the element body, and the element body becomes high temperature, which may cause thermal deterioration (softening or melting). When the element body is softened or melted, the dispersibility of the conductive particles in the polymer becomes locally non-uniform. In a polymer PTC element that has undergone such a thermal history, the resistance value at room temperature (room temperature resistance value) is greatly increased compared to that before this thermal history.

  Furthermore, if the temperature is repeatedly increased and decreased with respect to such a polymer PTC element, the room temperature resistance value of the polymer PTC element becomes higher. In such a polymer PTC element having a high room temperature resistance value, the power consumption increases. As described above, the increase in the room temperature resistance value of the polymer PTC element caused by heating when joining the electrode plate and the terminal plate is a problem such as shortening the battery life when mounted on a small device such as a mobile phone. Leads to.

  Therefore, in the conventional polymer PTC element, it is necessary to relatively increase the thickness of the electrode plate in order to relax conduction to the element body of heat applied to the electrode plate during soldering and welding. Therefore, it has been a hindrance to the reduction in thickness, weight, and cost of the element.

International Publication No. 2004/023499 Pamphlet

  The present invention has been made in view of such a situation, and its purpose is to reduce the thermal deterioration of the element body when the electrode plate and the terminal plate are joined by welding or the like even when the thickness of the electrode plate is reduced. An object of the present invention is to provide a PTC element that can be effectively prevented and can be reduced in thickness and weight while effectively exhibiting the original function of the element. Another object of the present invention is to provide a battery protection system capable of effectively protecting a battery when an excessive current flows.

In order to achieve the above object, the PTC element according to the present invention includes:
An element body whose resistance value increases as the temperature rises in a predetermined temperature range;
A PTC element having a pair of first and second electrode plates bonded to the front and back surfaces of the element body,
At least one first electrode plate of the electrode plates is formed integrally with the first element bonding piece, which is bonded to the element body, and the first element bonding piece. A first terminal joining piece extending from the piece toward the outside of the element body.

  Preferably, the element body is a conductive polymer having a positive temperature coefficient.

  In the PTC element according to the present invention, the first electrode plate includes a first element joining piece for joining to the element body, and a first terminal joining piece for joining to the terminal plate by spot welding or the like. ,have. That is, when joining the first electrode plate to the terminal plate by spot welding or the like, the terminal plate is joined to the first terminal joining piece. Therefore, the heat at the time of spot welding the first terminal joining piece and the terminal plate is not easily transmitted to the element body, and thermal deterioration of the element body can be prevented.

  According to the PTC element of the present invention, it is possible to prevent thermal deterioration of the element body, so that it is possible to reduce power consumption during normal use, and when necessary, cut off the current. The original function of protecting electronic devices can be effectively exhibited.

In the PTC element of the present invention, preferably, the thickness of the first electrode plate is 25 to 300 μm, more preferably 25 to 150 μm.
Since the first electrode plate has the first element joint piece and the first terminal joint piece, even when the thickness of the first electrode plate is reduced as described above, It is possible to effectively prevent thermal deterioration of the element body due to heat generated during spot welding between the one-terminal joining piece and the terminal plate. As a result, it is possible to reduce the thickness, weight, and cost while effectively exhibiting the original function of the element. In addition, by reducing the thickness of the first electrode plate, even if an impact is applied to the joint between the first electrode plate and the terminal plate due to dropping or the like, the stress at the joint interface is reduced. Therefore, it is possible to prevent peeling at the interface of the joint portion.

Preferably, the second electrode plate is a clad plate in which two or more kinds of plate materials are laminated.
By configuring the second electrode plate with a clad plate, the second electrode plate to which the element body is bonded can be directly bonded to the electrode terminal of the battery, and the manufacturing process is made more efficient and the entire system is thin. And weight reduction can be realized. In particular, at least one surface of the second electrode plate is made of a material suitable for bonding to the element body, and the other surface of the second electrode plate is suitable for bonding to an electrode terminal of a battery. It is preferable to use a clad plate made of any material.

  Preferably, the second electrode plate is integrally formed with the second element bonding piece and the second element bonding piece bonded to the element main body, and the element main body is formed from the second element bonding piece. A second terminal joining piece extending outward. By configuring the second electrode plate as described above, the same effects as those of the first electrode plate described above can be obtained.

  Preferably, the thickness of the second electrode plate is 30 to 600 μm, more preferably 30 to 200 μm.

  Preferably, the first terminal joint piece of the first electrode plate and the second terminal joint piece of the second electrode plate extend in the same direction when viewed from the thickness direction of the element body. Yes. By adopting such a configuration, the entire element can be made compact.

  Preferably, a protective film is formed on the exposed surface of the element body which is not covered with the first and second electrode plates. The protective film preferably has an oxygen barrier property. By configuring the protective film, it is possible to prevent deterioration of the element body.

  In the present invention, metal foil may be laminated on the front and back surfaces of the element body, and the first and second electrode plates may be bonded to each metal foil.

  Any one of the first and second electrode plates may be configured to be electrically connected to the protection circuit, and the other may be configured to be electrically connected to the battery. In the present invention, the first electrode plate is configured to be electrically connected to the protection circuit, and the other second electrode plate is configured to be electrically connected to the battery. Is preferred.

The battery protection system according to the present invention includes:
A PTC element according to any of the above,
A protection circuit electrically connected to the first electrode plate of the PTC element;
A battery electrically connected to the second electrode plate of the PTC element.

  The battery protection system according to the present invention can effectively protect the battery even when an excessive current flows or even when an impact or pressure is applied.

  According to the present invention, it is possible to effectively prevent thermal deterioration of the element body when the electrode plate and the terminal plate are joined by welding or the like, so that the thickness of the electrode plate can be reduced. It is possible to provide a PTC element that can be reduced in thickness and weight while effectively exhibiting the above function.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a cross-sectional view showing a main part of a PTC element according to an embodiment of the present invention,
FIG. 2 is a cross-sectional view of an essential part showing details of spot welding,
FIG. 3 is a cross-sectional view of a PTC element according to another embodiment of the present invention.
FIG. 4 is a cross-sectional view of a main part showing a usage state of a PTC element according to another embodiment of the present invention.

Overall Configuration of Polymer PTC Element First, a polymer PTC element for protecting a secondary battery cell used as a power source of a mobile phone will be described as an embodiment of a PTC element according to the present invention.

A polymer PTC element 2 shown in FIG. 1 is incorporated between a secondary battery cell 32 which is a power source of a mobile phone and a protection circuit 30 for protecting the secondary battery cell 32 from overcurrent. The polymer PTC element 2 cuts off the current between the protection circuit 30 and the secondary battery cell 32 when an overcurrent that cannot be controlled by the protection circuit 30 flows during charging or discharging of the secondary battery cell 32. Thus, the secondary battery cell 32 is protected.
Below, the whole structure of a polymer PTC element is demonstrated first.

  A polymer PTC element 2 shown in FIG. 1 includes an element body 4 made of a conductive polymer having a positive resistance temperature characteristic (PTC characteristic). The element body 4 has front and back surfaces (a first surface 6 and a second surface 8 facing each other). A first electrode plate 10 and a second electrode plate 12 are joined to the first surface 6 and the second surface 8, respectively. As a result, the element body 4 is disposed so as to be sandwiched between the first electrode plate 10 and the second electrode plate 12. As shown in FIG. 1, the second electrode plate 12 is a clad plate composed of a laminated plate of a nickel layer 14 and an aluminum layer 16.

  The first electrode plate 10 is integrally formed with the first element joint piece 10a to be joined to the element body 4 and the first element joint piece 10a, and is on the same plane as the first element joint piece 10a. 1st terminal joining piece 10b located in this. The first terminal bonding piece 10 b is configured to extend from the first element bonding piece 10 a toward the outside of the element body 4. The first terminal joining piece 10 b is joined to the terminal plate 18, whereby the polymer PTC element 2 is electrically connected to the protection circuit 30.

  That is, as shown in FIG. 1, in the present embodiment, the first terminal joining piece 10 b extending to a portion that does not overlap with the element body 4 when seen from the thickness direction of the element body 4 is joined to the terminal plate 18. Yes. In the present embodiment, the first terminal joining piece 10b and the terminal plate 18 are joined by spot welding.

  The extension length of the first terminal joining piece 10b (the length of the portion that does not overlap the element body 4 when viewed from the thickness direction of the element body 4) L1 may be appropriately determined according to the size of the product. , Preferably it is the range of 0.4-35 mm, More preferably, it is the range of 1.5-5.0 mm. If the extension length L1 is too small, the heat generated when the first terminal joining piece 10b and the terminal plate 18 are joined by spot welding or the like is conducted to the element body 4, and the element body 4 is thermally deteriorated. There is a risk of it. On the other hand, if the extension length L1 is too large, the cost is increased and it is against the request for downsizing of the entire element.

  In addition, the width of the first terminal bonding piece 10b (the width when viewed from the thickness direction of the element body 4) may be the same as the width of the first element bonding piece 10a, or the width of the first element bonding piece 10a may be the same. It may be smaller than the width.

  In the present embodiment, the element bonding surface 10c of the first element bonding piece 10a in the first electrode plate 10 is in direct contact with the first surface 6 of the element body 4, and the element bonding surface 10c is uneven. is there. Further, the terminal bonding surface 10d of the first terminal bonding piece 10b is flatter than the element bonding surface 10c.

  The unevenness formed on the element bonding surface 10c is for strengthening thermocompression bonding with the element body 4, and the formation method is not particularly limited, but, for example, roughening treatment by forming a plating film is preferable. . A large number of nodular protrusions can be formed on the element bonding surface 10c of the first element bonding piece 10a by the roughening treatment by the plating film formation. This nodule-like protrusion is a convex part with a difference in unevenness of about 5 to 15 μm and a narrowed middle part or base part with respect to the head, and thermocompression bonding between the element body 4 and the element bonding surface 10c of the element bonding piece 10a. Strength can be improved.

  In addition, as a method of forming the unevenness formed on the element bonding surface 10c, in addition to the roughening treatment by plating film formation, the surface roughening treatment by acid machining, etching treatment, blast treatment, cutting, etc. Other processes are exemplified. The terminal bonding surface 10d of the first electrode plate 10 may be formed by forming a concavo-convex shape on the entire surface of one surface of the first electrode plate 10 and then performing a flattening process by pressing or the like. Alternatively, a portion other than the element bonding surface 10c may be masked to form irregularities only on the element bonding surface 10c.

  In the present embodiment, the first electrode plate 10 is made of nickel or a nickel alloy, and the terminal plate 18 connected to the protection circuit 30 is also a nickel plate that can be easily joined to the first electrode plate 10 by spot welding. It is configured.

  The thickness of the first electrode plate 10 is preferably 25 to 300 μm, and more preferably 25 to 150 μm. In the present embodiment, since the first electrode plate 10 and the terminal plate 18 are joined by spot welding to the first terminal joining piece 10b extending from the first element joining piece 10a, heat generated by spot welding is used. Can be made difficult to be transmitted to the element body 4. Therefore, it is possible to prevent thermal degradation of the element body 4 without adopting a method of relatively increasing the thickness of the first electrode plate 10, and as a result, the first electrode plate 10 can be made thinner. Can do.

  If the thickness of the first electrode plate 10 is too thin, the strength of the first electrode plate 10 itself is lowered, and the reliability may be lowered. On the other hand, if it is too thick, it is difficult to make the polymer PTC element 2 thinner, lighter, and lower in cost, and further, an impact is applied to the joint between the first electrode plate 10 and the terminal plate 18 due to dropping or the like. In this case, the stress applied to the joint interface increases, and peeling at the joint interface tends to occur.

  Moreover, the thickness of the terminal board 18 is about 100-300 micrometers normally.

  The second electrode plate 12 is composed of a clad plate in which two types of plate materials of a nickel layer 14 and an aluminum layer 16 are laminated. As shown in FIG. 1, the second electrode plate 12 is formed integrally with a second element joining piece 12 a that is joined to the element body 4 and the second element joining piece 12 a. And a second terminal joining piece 12b located on an extended plane of the joining piece 12a. The second terminal joining piece 12b is configured to extend from the second element joining piece 12a toward the outside of the element body 4, and the extending direction is the same as that of the first terminal joining piece 10b. .

  The 2nd element joining piece 12a in the 2nd electrode plate 12 is comprised from the nickel layer 14a and the aluminum layer 16a, and the element joining surface 12c which is the outer surface of the nickel layer 14a has the above-mentioned 1st element joining piece 10a. Concavities and convexities similar to those of the element bonding surface 10c are formed.

  In addition, the second terminal joining piece 12b in the second electrode plate 12 is composed of a nickel layer 14b and an aluminum layer 16b, and the aluminum layer 16b and the electrode terminal 34 are joined, whereby the secondary battery cell 32 and the second battery cell 32 are electrically connected. Connected. The aluminum layer 16b of the second terminal joining piece 12b and the electrode terminal 34 are joined by spot welding. The electrode terminal 34 of the secondary battery cell 32 is generally made of an aluminum material and is easily joined to the aluminum layer 16b in the clad plate.

  The terminal bonding surface 12d of the second element bonding piece 12a in the second electrode plate 12 is preferably a flat surface without the unevenness formed on the element bonding surface 12c. The method for forming unevenness on the element bonding surface 12c in the second electrode plate 12 and the method for flattening the terminal bonding surface 12d other than the element bonding surface 12c partially form the uneven surface on the first electrode plate 10. It is the same as the method for doing.

  Although the thickness of the 2nd electrode plate 12 is not specifically limited, Preferably it is 30-600 micrometers, More preferably, it is 30-200 micrometers. The thickness ratio of the nickel layer 14 and the aluminum layer 16 in the second electrode plate 12 is preferably (nickel layer 14: aluminum layer 16) = 50: 50 to 67:33. The length of the 2nd electrode plate 12 is not specifically limited, It designs freely according to a use. Further, the nickel layer 14 may be composed of a nickel alloy in addition to the nickel simple substance, and similarly, the aluminum layer 16 may be composed of an aluminum alloy other than the aluminum simple substance.

  As shown in FIG. 1, a protective film 3 is formed on the surface of the element body 4 on the side surface not surrounded by the electrode plates 10 and 12 as necessary. By forming the protective film 3, it is possible to suppress the oxidation of the element body 4 due to oxygen in the atmosphere and to prevent the element body 4 from being deteriorated. The type of the protective film 3 is not particularly limited as long as it has a function of shielding oxygen, and examples thereof include epoxy resin, EVOH (ethylene-vinyl alcohol copolymer), PVA (polyvinyl alcohol), and the like.

  In the present embodiment, since the first terminal joining piece 10b is configured to extend from the first element joining piece 10a toward the outside of the element body 4, a resin is applied to the exposed surface of the element body 4. When the protective film 3 is formed, the resin that tends to go around from the exposed surface of the element body 4 to the surface of the first electrode plate 10 (the side to which the terminal plate 18 is bonded) is hindered by the first terminal bonding piece 10b. . That is, it is possible to prevent the resin from being applied to the terminal joint surface 10d that is the joint surface with the terminal plate 18 of the first electrode plate 10, and thus the protective film 3 is formed on the terminal joint surface 10d of the first electrode plate 10. In other words, the step due to the protective film 3 does not occur, so that the first electrode plate 10 and the terminal plate 18 can be well adhered and bonded.

  The shape of the element body 4 is not particularly limited, and examples thereof include a rectangular parallelepiped type and a cylindrical type. When the shape of the element body 4 is a rectangular parallelepiped, the dimensions of the element body 4 are about 3 to 5 mm in length, 2 to 5 mm in width, and about 0.5 to 1.0 mm in thickness.

Manufacturing Method of Polymer PTC Element 2 Next, a manufacturing method of the polymer PTC element 2 will be described.

Element body 4
The element body 4 is generally composed of a resin composition (conductive polymer) including a polymer (polymer compound such as a thermosetting resin or a thermoplastic resin) as main components and conductive particles. The element body 4 may include both a thermosetting resin and a thermoplastic resin as a polymer.

  First, a polymer compound (thermosetting resin, thermoplastic resin, etc.), conductive particles (metal powder, carbon black, etc.), a low molecular organic compound, a reaction initiator for cross-linking the polymer compounds, etc. Weigh and knead to adjust the PTC composition. The kneading method is not particularly limited, and examples thereof include a kneader, an extruder, and a mill. Further, as the conductive particles to be contained in the PTC composition, only conductive particles having a predetermined particle diameter are classified using a sieve or the like. Next, this PTC composition is shape | molded and the element main body 4 (FIG. 1) is obtained.

  Although it does not specifically limit as a thermosetting resin, An epoxy resin, a polyimide resin, unsaturated polyester resin, a silicon resin, a polyurethane resin, a phenol resin, etc. are mentioned. Preferably, an epoxy resin is used as the thermosetting resin. By using an epoxy resin, the polymer PTC element can have a sufficient resistance change amount and heat resistance. As for the molecular weight of the thermosetting resin, the weight average molecular weight Mw is usually about 300 to 10,000. Said thermosetting resin may be used independently and multiple types of resin may be used. Moreover, you may use the compound which has a structure where different kinds of thermosetting resins were bridge | crosslinked.

  Although it does not specifically limit as a thermoplastic resin, Preferably, a crystalline polymer is used. The melting point of the thermoplastic resin is not particularly limited, but is preferably about 70 to 200 ° C. By using a resin having a melting point within this range, it is possible to prevent the thermoplastic resin from melting, flowing, and deformation of the element body during the operation of the polymer PTC element.

  The thermoplastic resin is not particularly limited, but polyolefin such as polyethylene, copolymer such as ethylene-vinyl acetate copolymer, vinyl halide and vinylidene polymer such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene fluoride, 12-nylon, etc. Polyamide, polystyrene, polyacrylonitrile, thermoplastic elastomer, polyethylene oxide, polyacetal, thermoplastic modified cellulose, polysulfones, polymethyl (meth) acrylate, and the like.

  The weight average molecular weight Mw of the thermoplastic resin is not particularly limited, but is preferably 10,000 to 5,000,000. These thermoplastic resins may be used alone or a plurality of types of resins may be used. Moreover, you may use the compound which has a structure where different types of thermoplastic resins were bridge | crosslinked.

  Although it does not specifically limit as electroconductive particle contained in the element main body 4, Metal powder, carbon black, etc. are illustrated. Preferably, metal powder is used as the conductive particles. As the metal powder, a powder mainly composed of nickel is preferably used. The average particle diameter of the metal powder is preferably 0.1 μm or more, and more preferably about 0.5 to 4.0 μm.

  In the element body 4, the content of the conductive particles in the resin composition is preferably 20 to 80% by mass with respect to the entire resin composition. By setting the content of the conductive particles within this range, the room temperature resistance value during non-operation can be sufficiently lowered, and a large resistance change amount can be obtained. Furthermore, variation in element resistance can be sufficiently reduced.

  The resin composition constituting the element body 4 further includes, for example, a low-molecular organic compound such as wax, oil, fatty acid, and higher alcohol in addition to the above-described thermosetting resin, thermoplastic resin, and conductive particles. But you can. As a result, it is possible to increase the resistance change amount accompanying the temperature rise of the element body 4.

  The element body 4 may include a base material that has a gap inside and can fill the gap with the resin composition. Such a substrate is not particularly limited as long as it can play the above role, and examples thereof include woven fabrics, nonwoven fabrics, and continuous porous bodies.

  The element body 4 is irradiated with an electron beam as necessary. By this electron beam irradiation, the reaction initiator functions and the cross-linking reaction between the polymers is promoted. The energy source for the crosslinking reaction is not limited to electron beams, and gamma rays, ultraviolet rays, heat, and the like are also used. What is necessary is just to adjust suitably the acceleration voltage and electron beam irradiation amount of the electron beam to irradiate according to the kind of high molecular compound contained in the element main body 4, or the dimension of an element main body. The electron beam irradiation may be performed after the electrode plates 10 and 12 are joined.

Formation of First Electrode Plate 10 and Second Electrode Plate 12 and Thermocompression Bonding First electrode plate 10 is formed by punching and molding a nickel metal plate or nickel alloy plate having a predetermined thickness. The clad plate constituting the second electrode plate 12 is formed by rolling a nickel metal plate or nickel alloy plate having a predetermined thickness and an aluminum metal plate or aluminum alloy plate having a predetermined thickness. Concavities and convexities are formed on the element bonding surface 10c of the first electrode plate 10 and the element bonding surface 12c of the second electrode plate 12 for strengthening thermocompression bonding with the element body 4 by the method described above.

Next, the first electrode plate 10 and the second electrode plate 12 are thermocompression bonded to the front and back surfaces (the first surface 6 and the second surface 8) of the element body 4 by a hot press machine or the like. Although the heating temperature at the time of thermocompression bonding depends on the material of the element body 4, it is preferably about 130 to 180 ° C. The pressure during thermocompression bonding is preferably about 1 × 10 ^{6 to} 3 × 10 ⁶ Pa.

  At the time of thermocompression bonding, the element main body 4 is slightly crushed in the thickness direction due to pressure and may protrude slightly to the side of the electrode plates 10 and 12, but unnecessary portions can be easily removed.

Formation of the protective film 3 Next, the protective film 3 is formed on the exposed side surface of the element body 4 that is not surrounded by the electrode plates 10 and 12 as necessary. A method for forming the protective film 3 is not particularly limited, and examples thereof include a method in which the above-described resin is applied and dried.

Note that, as described above, in the present embodiment, the first terminal joining piece 10b is configured to extend from the first element joining piece 10a toward the outside of the element body 4, and therefore, when the resin is applied. In addition, the resin that tends to go around from the exposed surface of the element body 4 to the surface of the first electrode plate 10 (the side to which the terminal plate 18 is bonded) is blocked by the first terminal bonding piece 10b. Therefore, the protective film 3 is sandwiched between the first terminal joining piece 10b and the second terminal joining piece 12 as shown in FIG. 1 on the side surface on the first terminal joining piece 10b side. It is formed in the state.
In this way, as shown in FIG. 1, the polymer PTC element 2 according to this embodiment is completed.

Assembling Method of Polymer PTC Element 2 The polymer PTC element 2 is assembled between the secondary battery cell 32 and the protection circuit 30 as shown in FIG. In order to connect the polymer PTC element 2 as shown in FIG. 1, for example, first, the aluminum layer 16 b side of the terminal joining piece 12 b of the second electrode plate 12 in the element 2 is connected to the electrode terminal 34 of the secondary battery cell 32. And spot welded. When a gap is formed between the element 2 and the secondary battery cell 32, a spacer 36 or the like is disposed between the element 2 and the secondary battery cell 32.

  Next, the terminal plate 18 connected to the protection circuit 30 is joined to the first terminal joining piece 10b of the first electrode plate 10 by spot welding. In spot welding, as shown in FIG. 2, a pair of electrode rods 50 are pressed from the surface of the terminal plate 18 with the support plate 52 inserted into the element body 4 side of the first electrode plate 10. A current is passed between the electrode rods 50 to perform spot welding of the terminal plate 18 and the first terminal joining piece 10b. The first terminal joining piece 10b and the terminal plate 18 may be joined before the first terminal joining piece 12b and the electrode terminal 34 are joined.

  In the polymer PTC element 2 according to the present embodiment, when the terminal plate 18 is joined to the first electrode plate 10 by spot welding or the like, from the first element joining piece 10 a toward the outside of the element body 4. The terminal plate 18 is joined to the extended first terminal joining piece 10b. Therefore, the heat at the time of spot welding the first terminal joining piece 10b and the terminal plate 18 is difficult to be transmitted to the element body 4, and thermal deterioration of the element body 4 can be prevented.

  Furthermore, in the present embodiment, since the heat generated by spot welding can be made difficult to be transmitted to the element body 4, the first electrode plate 10 is made relatively thick in order to prevent thermal deterioration of the element body 4. As a result, the first electrode plate 10 can be made thinner. Since the first electrode plate 10 can be made thin, it is possible to reduce the thickness, weight, and cost while effectively exhibiting the original function of the element.

  That is, the polymer PTC element 2 according to the present embodiment can reduce power consumption during normal use while realizing thinning, weight reduction, and cost reduction. The original function of blocking the current and protecting the secondary battery cell 32 can be effectively exhibited.

  In addition, by reducing the thickness of the first electrode plate 10, even if an impact is applied to the joint between the first electrode plate 10 and the terminal plate 18 due to dropping or the like, the stress at the joint interface is reduced. Therefore, it is possible to prevent peeling at the joint interface.

  Further, in the present embodiment, since the second electrode plate 12 is constituted by a clad plate composed of the nickel layer 14 and the aluminum layer 16, the second electrode plate 12 to which the element body 4 is bonded is interposed via the aluminum layer 16. Thus, it can be directly joined to the electrode terminal 34 of the secondary battery 32, and the manufacturing process can be made more efficient and the overall system can be made thinner and lighter.

  Furthermore, the first terminal joining piece 10b of the first electrode plate 10 and the second terminal joining piece 12b of the second electrode plate 12 are extended in the same direction when viewed from the thickness direction of the element body 4. Thus, the entire element 2 can be made compact.

The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, as shown in FIG. 3, in the present invention, metal foils 60 such as nickel are laminated on the front and back surfaces of the element body 4. The electrode plate 12 may be bonded via the solder layer 62. The metal foil 60 is made of a metal or an alloy such as nickel, and is integrated with the element body 4 by hot pressing the metal foil on both sides of the sheet-like element body 4 and then punching it out to a predetermined dimension. can do. The thickness of the metal foil 60 is thinner than the thickness of the electrode plates 10 and 12, and is generally 25-30 μm. Even in this case, the same effect as the above-described embodiment can be obtained.

  Further, as shown in FIG. 4, the extending direction of the first terminal joining piece 100 b of the first electrode plate 100 and the extending direction of the second terminal joining piece 12 b of the second electrode plate 12 define the element body 4. It may be configured such that it is sandwiched and extends to the opposite side. Similarly, in FIG. 4, the extending direction of the first terminal joining piece 100 b of the first electrode plate 100 is perpendicular to the extending direction of the second terminal joining piece 12 b of the second electrode plate 12 (that is, The direction may be perpendicular to the paper surface.

In the above-described embodiment, the second electrode plate 12 is a clad plate made of the nickel layer 14 and the aluminum layer 16, but the layers 14 and 16 may be made of a material other than nickel and aluminum.
Further, the second electrode plate 12 may be a single plate made of nickel, for example, without being a clad plate. In this case, a single plate made of nickel (corresponding to the second electrode plate 12) may be connected to the electrode terminal 34 of the secondary battery cell 32 through another clad plate made of a nickel layer and an aluminum layer. .

  The polymer PTC element 2 according to the present invention is used not only as an overcurrent protection element for the secondary battery cell 32 but also as a self-control heating element, a temperature sensor, a current limiting element, an overcurrent protection element, and the like. It is possible.

In the present invention, the method for producing the polymer PTC element 2 is not particularly limited. For example, as in the above-described embodiment, the polymer PTC element 2 is manufactured as follows without joining the element body 4, the first electrode plate 10, and the second electrode plate 12 to each other alone. Also good.
That is, the sheet-like element body constituting the element body 4 after cutting and the pair of sheet-like electrodes that respectively constitute the first electrode plate 10 and the second electrode plate 12 after cutting are unnecessary after thermocompression bonding. Individual polymer PTC elements 2 may be formed by punching out the parts with a press. In that case, the efficiency of the manufacturing process of the polymer PTC element 2 can be improved by joining the assembly of parts constituting the polymer PTC element 2 at a time.

FIG. 1 is a cross-sectional view of a principal part showing a usage state of a PTC element according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part showing details of spot welding. FIG. 3 is a cross-sectional view of a PTC element according to another embodiment of the present invention. FIG. 4 is a cross-sectional view of a main part showing a usage state of a PTC element according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Polymer PTC element 3 ... Protective film 4 ... Element main body 10 ... 1st electrode plate 10a ... 1st element joining piece 10b ... 1st terminal joining piece 10c ... Element joining surface 10d ... Terminal joining surface 12 ... 2nd electrode plate 12a ... 2nd element joining piece 12b ... 2nd terminal joining piece 12c ... Element joining surface 12d ... Terminal joining surface 14 ... Nickel layer 16 ... Aluminum layer 18 ... Terminal board 30 ... Protection circuit 32 ... Secondary battery cell 34 ... Electrode terminal 50 ... Electrode rod 60 ... Metal foil 62 ... Solder layer

Claims (10)

An element body whose resistance value increases as the temperature rises in a predetermined temperature range;
A PTC element having a pair of first and second electrode plates bonded to the front and back surfaces of the element body,
At least one first electrode plate of the electrode plates is formed integrally with the first element bonding piece, which is bonded to the element body, and the first element bonding piece. And a first terminal joining piece extending from the piece toward the outside of the element body.   The PTC element according to claim 1, wherein the element body is a conductive polymer having a positive temperature coefficient.   The PTC element according to claim 1, wherein the first electrode plate has a thickness of 25 to 300 μm.   The PTC element according to any one of claims 1 to 3, wherein the second electrode plate is formed of a clad plate in which two or more kinds of plate materials are laminated.   The second electrode plate is integrally formed with the second element joining piece to be joined to the element body and the second element joining piece, and extends from the second element joining piece toward the outside of the element body. The PTC element according to any one of claims 1 to 4, further comprising: a second terminal joining piece extending.   The PTC element according to claim 1, wherein the second electrode plate has a thickness of 30 to 600 μm.   The first terminal joint piece of the first electrode plate and the second terminal joint piece of the second electrode plate extend in the same direction when viewed from the thickness direction of the element body. 5. The PTC element according to 5 or 6.   The PTC element according to claim 1, wherein a protective film is formed on an exposed surface of the element body that is not covered with the first and second electrode plates.   The PTC element according to claim 1, wherein metal foils are laminated on the front and back surfaces of the element body, and the first and second electrode plates are bonded to each metal foil. . A PTC element according to any one of claims 1 to 9,
A protection circuit electrically connected to the first electrode plate of the PTC element;
And a battery electrically connected to the second electrode plate of the PTC element.

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