1. Field of the Invention
The present invention relates to a thermoprotector in which the melting point or the softening point of a fusible material is set as the operating temperature, a thermosensor which is useful in the thermoprotector, and a method of producing a thermosensor.
2. Explanation of Related Art
As a thermoprotector which senses abnormal heating of an electrical or electronic apparatus, and which performs a cut-off operation based on this sense to interrupt the apparatus from a power supply, thereby preventing overheat of the apparatus and occurrence of a fire, a system in which elastic distortion energy is stored and the elastic distortion energy is released by melting or softening of a fusible material is known.
For example, an elastic metal piece 2′ is forcibly bent as shown in (10A) of
As shown in (11A) of
In the system shown in
In the system shown in
It is an object of the invention to ensure a long-term stability of a thermosensor of a type in which elastic distortion energy of an elastic member that holds the elastic distortion energy by joint fixation due to a soluble material such as solder is released by melting of the soluble material, thereby causing an operation, and improve the operation reliability of a thermoprotector using such a thermosensor.
The thermosensor of the invention is characterized in that both ends of an elastic member are fixed to a body in a state where the elastic member is compressed in a longitudinal direction, to form the elastic member into a convex curved shape, one end side of the convex curved shape is raised by a predetermined angle with respect to the body, a flexure angle of another end of the convex curved shape is zero, the fixation of one end portion of the elastic member and the body is conducted via a fusible material, and a melting point or a softening point of the fusible material is an operating temperature.
The thermosensor of the invention is characterized in that, in the thermosensor, one end portion of the elastic member is inward folded, and a folded piece is face joined to a surface of the body via the fusible material.
The thermosensor of the invention is characterized in that, in the thermosensor, one end portion of the elastic member is folded, and an inner side face of a folded piece is face joined to a rear face of a tip end portion of the body via the fusible material.
The thermosensor of the invention is characterized in that, in the thermosensor, the elastic member is a metal, a composite material of a metal and a resin, or a polymer.
The thermosensor of the invention is characterized in that, in the thermosensor, the fusible material is a low-melting point metal.
The thermosensor of the invention is characterized in that, in the thermosensor, the fusible material is a thermoplastic resin.
The thermosensor of the invention is characterized in that, in the thermosensor, the elastic member is a metal, and forms a part of a conduction path.
The thermoprotector of the invention is characterized in that the thermosensor is configured with setting as a body face a surface of one of paired electrodes which are disposed via a gap, an elastic metal of the thermosensor and the one electrode are electrically conducted with each other, and the elastic metal of the thermosensor and another one of the electrodes are in contact with other.
The thermoprotector of the invention is characterized in that the thermoprotector has a stationary electrode and a movable electrode, and the thermosensor is incorporated so that the movable electrode is contacted with the stationary electrode by an operation of the thermosensor.
The method of producing a thermosensor of the invention is a method of producing the thermosensor, and characterized in that one end portion of a wide elastic member material is face joined to a wide body material via a fusible material, the joined member is cut into many strips and the elastic member piece is folded back with setting the face joined portion as a boarder, or the elastic member material is folded back with setting the face joined portion as a boarder and the joined member is cut into many strips, and thereafter another end portion of the elastic member piece is fixed to a body at a flexure angle of zero in a state where the elastic member piece is compressed in a longitudinal direction.
The method of producing a thermosensor of the invention is a method of producing the thermosensor, and characterized in that one end portion of a wide elastic member material is face joined to a rear face of a tip end portion of a wide body material via a fusible material, the joined member is cut into many strips and the elastic member piece is folded back toward a surface of a body, or the elastic member material is folded back toward a surface of the body and the joined member is cut into many strips, and thereafter another end portion of the elastic member piece is fixed to the body at a flexure angle of zero in a state where the folded elastic member piece is compressed in a longitudinal direction.
The dynamic state of the elastic member can be approximated to that in the case where a column in which one end is fixed and the other end is hinge-supported is compressed in an axial direction. Application of a bending moment reaction force on the fixed portion of the one end of the elastic member which corresponds to a hinge-supported side can be sufficiently suppressed. Main stress acting on the face joining interface by the fusible material between the one end of the elastic member and the body can be restricted to shearing stress, so that application of a cleavage force due to the bending moment reaction force on the interface can be largely reduced.
Therefore, the face joining interface by the fusible material can be stably held, and an operation failure due to, for example, creep of the fusible material of the joining interface can be satisfactorily prevented from occurring.
In a battery pack of a lithium-ion secondary battery, a lithium polymer secondary battery, or the like, a thermoprotector which senses abnormal heat generation of the battery or a power transistor, and which interrupts the energization is necessary. The thermoprotector of the invention can be easily miniaturized, and can be satisfactorily incorporated in a battery pack. Consequently, the thermoprotector can be preferably used as a battery thermoprotector.
(1A) and (1B) of
Referring to (1A) and (1B) of
In the example of (1B) of
In both the basic structures, the elastic member 2 is deformed into a convex curved shape, and elastic bending distortion energy is stored. When the fusible material 3 is melted or softened, the fixation by the face joint is canceled, the elastic bending distortion energy is released, and the height h of the convex curved shape is reduced. The reduction appears as a heat sensing signal, and the sensor operates. In both the basic structures, one end portion 20 of the elastic member 2 which is deformed into the convex curved shape is dynamically equivalent to a rigid joint of a predetermined angle.
Referring to
d2y/dx2=−Mx/EI
is held (EI is the flexural rigidity of the column), and the bending moment Mx is given by
Mx=py−Mox/L.
When p/EI=k2, therefore, the shape y of a convex curve is given by
y=A[cos kx−(sin kx/kL)+(x/L)−1]tan kL=kL.
Since the height h of the convex curve y is known at x=L′, the coefficient A can be obtained from
yx=L′=h, (dy/dx)x=L′=0.
Therefore, the flexure angle θL at the hinge-supported end is given by
θL=(dy/dx)x=L=A[(cos kL/L)−k(sin kL)+(1/L)].
Referring to
A column indicated by the broke line 3B in
In the thermosensor of the invention, as shown in
When the longitudinal compression force acting on the elastic member is indicated by p and the area of the joining interface is indicated by S, shearing stress τ of the joining interface is given by τ=p/S. The shearing strength of the joining interface must exceed f/S. The shearing strength must be provided with a sufficient safety factor. Therefore, preferably, a hole, a recess, or a notch is formed in one or both of the other end portion of the elastic member and the body face which are to be face joined to each other, and the fusible material is caused to enter the hole or the like, or one or both of the other end portion of the elastic member and the body face which are face joined to each other are roughened, whereby the shearing strength of the joining interface is enhanced. Alternatively, in order to mechanically reinforce the interface which is face joined by the fusible material, the fusible material may be applied to the tip end face of the elastic member and the body face.
As the body 1, a material which can endure the longitudinal compression force p is used.
As the elastic member 2, a metal, a synthetic resin, or a composite material of a metal and a synthetic resin may be used. Such a composite material may include a resin to which metal powder is mixed. When a material having a high electrical resistance such as a resin to which metal powder is mixed is used as the elastic member, the sensor or the protector can be operated by causing the fusible material to be melted by heat generation due to energization of a resistor.
As the fusible material 3, a fusible alloy such as solder, a single metal, a thermoplastic resin, or a conductive thermoplastic resin to which conductive powder is added may be used.
One face or both faces of the whole length of the elastic member may be coated with the fusible material to uniformalize the flexural rigidity of the whole length of the elastic member. This is effective for preventing concentration of bending stress.
As the body, a base of a housing of a thermoprotector may be used as described later. Usually, an electrode having a lead portion is used as the body, and one end portion of the elastic member is face joined to a tip end portion of the electrode via the fusible material.
A set member of the electrode and the elastic member can be obtained in the following manner. As shown in (4A) of
A wide electrode material and a wide elastic member material may be face joined to each other, the elastic member material may be folded back at a predetermined angle, and the joined member may be then cut into many rectangular strips.
As shown in (4D) of
After the set member of the electrode and the elastic member is produced, the other end portion 22 of the elastic member 2 is fixed by face joining to the body face at a flexure angle of zero. In the fixation, useful is riveting in which a previously disposed projection of a synthetic resin (having a softening point which is higher than the softening point of the fusible material) is used as a fixing part, an adhesive agent having a melting or softening point which is higher than the melting or softening point of the fusible material, or welding (preferably, welding in which a flux is used) such as resistance welding, or electromagnetic induction heating welding.
As described above, the thermosensor of the invention is dynamically equivalent to a column in which one end is fixed and the other end is hinge-supported. When the height of the convex curve is h and the length of the elastic member is L, the stored elastic bending distortion energy is an intermediate value between the elastic bending distortion energy 2 h2π4/L3 of a column in which both ends are fixed, and the elastic bending distortion energy h2π4/(2 L3) of a column in which both ends are hinge-supported. As compared with a thermosensor in which both ends of the elastic member are fixed at a flexure angle of zero, the length of the elastic member can be shortened under the conditions of the same stored elastic bending distortion energy. This is advantageous in miniaturization of a thermosensor.
When the height h of the convex curve is identical, the total length of the convex curve in a column in which one end is fixed and the other end is hinge-supported is longer (about 1.2 times) than that in a column in which both ends are fixed. Under the conditions of the same total length of the convex curve, therefore, the distance between the supports in the column is shortened. In the thermosensor of the invention, the length can be correspondingly shortened.
(5A) of
Referring to
As the housing 6, an insulator such as ceramics or a synthetic resin is used. The housing may be configured by upper and lower two split pieces, and assembled by, for example, fusion bonding such as high-frequency welding, an adhesive agent, or fitting.
In the thermoprotector, normally, the electrical conduction is made through a path of the lead portion of the one electrode→the elastic plate→the contact face of the elastic plate and the other electrode→the lead portion of the other electrode. Since the fusible material 3 is not included in the conduction path, the conductivity of the fusible material does not participate in that of the conduction path. As the fusible material, also a thermoplastic resin may be used.
The operation of the thermoprotector will be described. When the external temperature is raised and the fusible material 3 is heated to the melting point or the softening point, the face joint by the fusible material 3 between the one end portion 21 of the elastic plate and the one electrode 51 is released by the bending distortion energy of the elastic plate 2. As shown in
In order to assure reliable insulation between the folded portion of the tip end of the elastic member and the other electrode, it is preferable to dispose an insulating film 502 on the other electrode 52 as shown in
A contact pressure is applied to the contact face between the outer face of the convex curve of the elastic plate 2 and the other electrode 52 in (5B) of
In the thermoprotector of the invention, it is preferable to commonly configure the upper and lower housing pieces.
When the width of the auxiliary wall 65 is a, the width of the riveting projection 4 is b, the inner width of the housing piece is c, (2b+a) is slightly smaller than c. A gap (c−a−2b) which is produced as a result of this dimensional relationship is small, and can be closed by deformation of the resin of the housing in heating joint by ultrasonic welding of housing pieces which will be described later.
The thermoprotector of the invention is produced with using such housing pieces in the following manner. First, a hole is opened in the elastic member-provided electrode which is obtained as shown in
In order to make the levels of the lead portions coincident with each other, the one lead portion 520 may be bent via a step along the end face of the housing as shown in
(8A) of
(8C) of
Referring to
In the case where a fusible metal is used in the joint fixation of the tip end portion 2 of the elastic lead conductor to the body face under the face contact, the fixation may be conducted after the body face is metallized by applying and etching of metal foil, or printing and baking of metal powder paste.
The reference numeral 520 denotes another flat lead conductor in which a tip end portion 52 is bent and shaped to be in contact with the bent top face of tip end portion 2 of the one elastic lead conductor.
The reference numeral 6 denotes a housing which is configured by an insulator such as ceramics or a synthetic resin, and bonded to the base body by, for example, fusion bonding such as high-frequency welding (in the case where both the base and the housing are made of a synthetic resin), an adhesive agent, or fitting.
As the one lead conductor, an elastic round wire in which a tip end portion is crushed to be thinned may be used.
In the thermoprotector, normally, the electrical conduction is made through a path of the one lead conductor 510→the contact face between the convex curved portion of the tip end portion 2 of the lead conductor and the tip end portion 52 of the other lead conductor 520→the other lead conductor 520. Since the fusible material 3 is not included in the conduction path, the conductivity of the fusible material does not participate in that of the conduction path.
The operation of the thermoprotector will be described. When the external temperature is raised and the fusible material 3 is heated to the melting point or the softening point, the face joint by the fusible material 3 between the tip end portion 2 of the one lead conductor and the body face is released by the bending distortion energy of the tip end portion 2 of the one elastic lead conductor. As shown in (8C) of
Also in the case described above, a contact pressure is applied to the contact face between the outer bent face of the tip end portion 2 of the elastic lead conductor and the tip end portion 52 of the other lead conductor 520, and the contact resistance is reduced. In order to further reduce the contact resistance, the contact face may be bonded by solder which is lower in melting point than the fusible material.
(9A) of
Referring to
The welding and fixation of the elastic plate 2 to the body face under the face contact, and the joining and fixation by the fusible material 3 under the face contact may be conducted after the body face is metallized by applying and etching of metal foil, or printing and baking of metal powder paste.
The reference numeral 6 denotes a housing which is configured by an insulator such as ceramics or a synthetic resin, and bonded to the base body 1 by, for example, fusion bonding such as high-frequency welding (in the case where both the base and the housing are made of a synthetic resin), an adhesive agent, or fitting.
In the thermoprotector, normally, the electrical conduction is made through a path of the one lead conductor→the stationary electrode→the contact face between the stationary electrode and the movable electrode→the movable electrode→the other lead conductor. Since the fusible material 3 is not included in the conduction path, the conductivity of the fusible material does not participate in that of the conduction path.
The operation of the thermoprotector will be described. When the external temperature is raised and the fusible material 3 is heated to the melting point or the softening point, the face joint by the fusible material 3 between the elastic plate 2 and the body face is released by the bending distortion energy of the elastic plate 2 of the thermosensor A. As shown in (9C) of
As the elastic metal material, for example, phosphor bronze can be used. In the case where a resin product is used as the elastic material, FRP in which a resin (a thermoplastic resin or a thermosetting resin) is reinforced by fibers such as glass fibers, metal fibers, or synthetic fibers, high-rigidity engineering plastic, or the like can be selected in consideration of relative relationships with the melting point of a thermoplastic resin used as the fusible material. As the elastic material, a composite material of an elastic metal material and a synthetic resin, such as a laminated member of a phosphor bronze plate and a polyamide film may be used.
For example, the dimensions of the elastic member are set in the following manner. In the case of a metal elastic plate, the thickness is 0.008 to 0.1 mm, the width is 0.3 to 4.6 mm, and the length is 1.5 to 11 mm.
As a resin used as the elastic material, and a thermoplastic resin as the fusible material, resins of a predetermined melting point can be selected from: engineering plastics such as polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polybutylene terephthalate, polyphenylene oxide, polyethylene sulfide, and polysulfone; engineering plastics such as polyacetal, polycarbonate, polyphenylene sulfide, polyoxybenzoyl, polyether ether ketone, and polyetherimide; polypropylene; polyvinyl chloride; polyvinyl acetate; polymethyl methacrylate; polyvinylidene chloride; polytetrafluoroethylene; ethylene-polytetrafluoroethylene copolymer; ethylene-vinyl acetate copolymer (EVA); AS resin; ABS resin; ionomer; AAS resin; ACS resin; etc.
As the housing, in place of these resins, also ceramics may be used. The dimensions of the housing are set, for example, so that the thickness is 0.3 to 1.5 mm, the width is 1 to 5 mm, and the length is 2 to 12 mm.
As a fusible alloy used as the fusible material, it is preferable to use an alloy which does not contain an element harmful to the biological system, such as Pb or Cd. A composition which can realize a melting point suitable to the operating temperature of the thermoprotector can be selected, for example, from: [A] compositions of In—Sn—Bi alloys such as (1) 43%<Sn≦70%, 0.5%≦In≦10%, and the balance Bi, (2) 25%≦Sn≦40%, 50%≦In ≦55%, and the balance Bi, (3) 25%<Sn≦44%, 55%<In≦74%, and 1%≦Bi<20%, (4) 46%<Sn≦70%, 18%≦In<48%, and 1%≦Bi≦12%, (5) 5%≦Sn≦28%, 15%≦In<37%, and the balance Bi (excluding a range of Bi±2%, In and Sn±1% with respect to Bi 57.5%, In 25.2%, and Sn 17.3%, and Bi 54%, In 29.7%, and Sn 16.3%), (6) 10%≦Sn≦18%, 37%≦In≦43%, and the balance Bi, (7) 25%<Sn≦60%, 20%≦In<50%, and 12%<Bi≦33%, (8) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 weight parts of any one of (1) to (7), (9) 33%≦Sn≦43%, 0.5%≦In≦10%, and the balance Bi, (10) a composition in which 3 to 5 weight parts of Bi are added to 100 weight parts of 47%≦Sn≦49% and 51%≦In≦53%, (11) 40%≦Sn≦46%, 7%≦Bi≦12%, and the balance In, (12) 0.3%≦Sn≦1.5%, 51%≦In≦54%, and the balance Bi, (13) 2.5%≦Sn≦10%, 25%≦Bi≦35%, and the balance In, (14) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 weight parts of any one of (9) to (13), and (15) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 weight parts of 10%≦Sn≦25%, 48%≦In≦60%, the balance Bi; [B] compositions of Bi—Sn—Sb alloys such as (16) 30%≦Sn≦70%, 0.3%≦Sb≦20%, the balance Bi, and (17) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of (16); [C] compositions of added to 100 weight parts of (16); [C] compositions of In—Sn alloys such as (18) 52%≦In≦85% and the balance Sn, and (19) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 weight parts of (18); [D] compositions of In—Bi alloys such as (20) 45%≦Bi≦55% and the balance In, and (21) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 weight parts of (20); [E] compositions of Bi—Sn alloys such as (22) 50%≦Bi≦56% and the balance Sn, and (23) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of (22); [F] In alloys such as (24) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of In, (25) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of 90%≦In≦99.9% and 0.1%≦Ag≦10%, and (26) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of 95%≦In≦99.9% and 0.1%≦Sb≦5%; and (27) a composition in which 0.01 to 7 weight parts of a total of one or two or more of Au, In, Cu, Ni, Pd, Pt, Ga, Ge, and P more of Au, In, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 weight parts of 2%≦Zn≦15%, 70%≦Sn≦95%, the balance Bi, and the alloy.
When the fusible alloy contains a large amount of a metal having a crystal structure of b.c.c., c.p.h., or the like, plastic deformation is suppressed, and the creep strength can be improved.
Preferably, these alloys, particularly, Bi-rich alloys previously cover laminarly the metal elastic member.
As the electrodes and the lead conductors, a conductive metal or a conductive alloy such as nickel, copper or a copper alloy can be used, and plating may be applied as required.
As described above, an electrode can be disposed in a tip end portion of a lead conductor, and a tip end portion of an elastic metal lead conductor can be crushed to be formed into an elastic plate-like shape.
In these cases, the body, and the lead conductor outside the housing can have an arbitrary shape.
A joined portion of an electrode or a lead conductor, an elastic member, or both fusible metals may be locally replaced with a material having an excellent weldability.
The electrode with a lead portion, and the lead conductor have, for example, a thickness of 0.05 to 0.3 mm, and a width of 0.5 to 4.6 mm.
Number | Date | Country | Kind |
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2004-227765 | Aug 2004 | JP | national |