JP5886609B2 - Breaker, safety circuit including the same, and secondary battery pack - Google Patents

Description

  The present invention relates to a small breaker or the like built in a secondary battery pack or the like of an electric device.

  Conventionally, a breaker has been used as a protection device for secondary battery packs and motors of various electrical devices. When the temperature of the secondary battery during charging / discharging rises excessively, or when an abnormality occurs such as when an overcurrent flows through a motor or the like equipped in a device such as an automobile or home appliance, Cut off current to protect secondary batteries and motors. A breaker used as a safety circuit of such a protective device is required to operate accurately following a temperature change and have a stable resistance value when energized in order to ensure the safety of the device. .

  In addition, when the breaker is used as a protection device for a secondary battery or the like installed in an electric device such as a thin-type multifunctional mobile phone called a notebook personal computer, a tablet-type portable information terminal device, or a smartphone, the above-described case is used. In addition to ensuring safety, miniaturization is required. In particular, in recent portable information terminal devices, users have a strong desire for miniaturization (thinning), and devices newly released by each company are designed to be small in order to ensure superiority in design. The tendency to be remarkable is remarkable. Against this background, breakers that are mounted together with secondary batteries as one component of portable information terminal devices are also strongly required to be further miniaturized.

  The breaker is provided with a thermally responsive element that operates according to a temperature change and conducts or shields a current. Patent Document 1 discloses a breaker to which a bimetal is applied as a thermally responsive element. Bimetal is an element that is formed by laminating two types of plate-like metal materials having different coefficients of thermal expansion, and controls the conduction state of the contact by changing the shape in accordance with a temperature change. The circuit breaker shown in the same document includes a fixed piece (base terminal), a movable piece (movable arm), a thermally responsive element, a PTC thermistor and the like housed in a resin case. Is used by being connected to an electric circuit of an electric device. A through hole is formed in the movable piece in the second elastic portion, and the elastic coefficient of the second elastic portion is optimized. In addition, a protrusion is inserted into the through hole, and the top portion thereof is joined to the back surface of the lid member, so that the strength and rigidity of the resin case is increased.

WO2011-105175

  In the breaker disclosed in Patent Document 1, when the through hole is formed in the second elastic portion having a constricted shape, the cross-sectional area perpendicular to the longitudinal direction of the movable piece is reduced in the second elastic portion, The conduction resistance increases. Therefore, the conduction resistance of the breaker during normal operation increases, making it difficult to obtain desired performance. In particular, when the width and thickness of the movable piece are set to be small in order to reduce the size of the breaker, it is difficult to secure a sufficient cross-sectional area of the movable piece as a conductor, and the above-described tendency becomes remarkable. .

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a breaker that can be downsized while suppressing conduction resistance during normal operation.

  In order to achieve the above object, a breaker according to the present invention includes a fixed piece having a fixed contact, an elastic portion that is elastically deformed, and a movable contact at a tip of the elastic portion, and the movable contact is used as the fixed contact. A movable piece that is pressed and brought into contact; a thermally responsive element that operates the movable piece so that the movable contact is separated from the fixed contact by being deformed as the temperature changes; and the fixed piece, the movable piece, and the thermal responsive element In the breaker provided with a resin case that accommodates the element, the movable piece has a through hole at a location where a cross-sectional area perpendicular to the longitudinal direction of the movable piece is larger than the cross-sectional area of the elastic portion. .

  In this invention, it is preferable that the through hole is formed at a location where the width dimension of the movable piece in the short direction of the movable piece is larger than the width dimension of the elastic portion.

  In this invention, it is preferable that the said through hole is an ellipse or ellipse shape long in either direction by planar view.

  In this invention, it is preferable that the resin case has a protrusion inserted into the through hole.

  In this invention, it is preferable that the movable piece has a constricted portion cut out in a short direction of the movable piece, and a part of the resin case is interposed in a cut-out portion of the movable piece.

  In addition, a safety circuit for an electric device according to the present invention includes the breaker.

  In addition, a secondary battery pack according to the present invention includes the breaker.

  According to the breaker of the present invention, since the through-hole is provided at a location where the cross-sectional area perpendicular to the longitudinal direction of the movable piece is larger than the cross-sectional area of the elastic portion, the cross-sectional area of the elastic portion in the peripheral portion of the through-hole. Is not significantly reduced. As a result, it is possible to reduce the size while suppressing the conduction resistance during the normal operation of the breaker.

  Further, according to the configuration in which the through hole is formed at a location where the width dimension of the movable piece in the short direction is larger than the width dimension of the elastic portion, the thickness distribution of the movable piece is made uniform and the periphery of the through hole is made uniform. A reduction in the cross-sectional area of the elastic portion in the region can be suppressed. As a result, it is possible to reduce the size while reducing the manufacturing cost of the movable piece and thus the breaker, while suppressing the conduction resistance during the normal operation of the breaker.

  In addition, according to the configuration in which the through hole is an ellipse or an ellipse that is long in either direction in plan view, the balance between the size reduction of the breaker and the rigidity of the movable piece can be easily adjusted. For example, by making the through hole an ellipse or an ellipse shape that is long in the short direction of the movable piece in plan view, the length of the movable piece can be reduced, and the breaker can be further miniaturized. Become. Moreover, the rigidity distribution of the movable piece can be changed by making the through hole into an oval or elliptical shape that is long in the longitudinal direction of the movable piece in plan view.

  Further, according to the configuration in which the resin case has the protrusion inserted into the through hole, the protrusion functions as a reinforcing portion, and the strength and rigidity of the resin case can be efficiently increased.

  In addition, according to the configuration in which the movable piece has a constricted portion cut in the short direction, and a part of the resin case is interposed in the cut portion of the movable piece, the part functions as a reinforcing portion. In addition, the strength and rigidity of the resin case can be increased more efficiently.

  Further, according to the safety circuit or the secondary battery pack provided with the breaker of the present invention, it is possible to reduce the size of the safety circuit or the secondary battery pack while suppressing the conduction resistance during the normal operation of the breaker. Become.

The assembly perspective view which shows the structure of the breaker by one Embodiment of this invention. Sectional drawing which shows operation | movement of the breaker in a normal charge or discharge state. Sectional drawing which shows operation | movement of a breaker in the time of an overcharge state or abnormality. The perspective view which shows a mode that a movable piece is integrated in a resin base. Sectional drawing which shows the state by which a cover member is integrated in the resin base and a movable piece is pushed by a cover member. The perspective view which shows another forms, such as a movable piece. The perspective view which shows another form, such as a movable piece.

  A breaker according to an embodiment of the present invention will be described with reference to the drawings. 1 to 3 show the configuration of the breaker. The breaker 1 includes a fixed piece 2 having a fixed contact 21, a movable piece 4 having a movable contact 3 at the tip, a thermally responsive element 5 that deforms with a change in temperature, a PTC (Positive Temperature Coefficient) thermistor 6, , A fixed piece 2, a movable piece 4, a thermally responsive element 5, and a resin case 7 that accommodates a PTC thermistor 6. The resin case 7 includes a resin base (first case) 71, a cover member (second case) 72 attached to the upper surface of the resin base 71, and the like.

  The fixed piece 2 is formed by pressing a metal plate mainly composed of phosphor bronze (in addition, a metal plate such as copper-titanium alloy, white or brass), and is embedded in the resin base 71 by insert molding. ing. A terminal 22 electrically connected to the outside is formed at one end of the fixed piece 2, and a PTC thermistor 6 is placed in the vicinity of the other end. The PTC thermistor 6 is placed on convex dowels (small protrusions) formed at three locations in the vicinity of the other end of the fixed piece 2. The fixed contact 21 is formed at a position facing the movable contact 3 by cladding, plating, coating, or the like of a conductive material such as silver, nickel, nickel-silver alloy, copper-silver alloy, gold-silver alloy. The resin base 71 is exposed from a part of the opening 73 formed above. The terminal 22 protrudes outward from one end of the resin base 71.

  The movable piece 4 is formed in an arm shape symmetrical to the center line in the longitudinal direction by pressing a metal plate equivalent to the fixed piece 2. A terminal 41 that is electrically connected to the outside is formed at one end in the longitudinal direction of the movable piece 4 and protrudes outward from the resin base 71. In the present embodiment, the movable piece 4 is bent in a crank shape at a step bending portion 46 inside the resin case 7 in order to make the height of the terminal 22 of the fixed piece 2 and the terminal 41 of the movable piece 4 uniform. . A movable contact 3 is formed at the other end of the movable piece 4 (corresponding to the tip of the arm-shaped movable piece 4). The movable contact 3 is made of the same material as the fixed contact 21 and is joined to the tip of the movable piece 4 by a technique such as welding. The movable piece 4 has a fixed portion 42 (corresponding to the base end of the arm-shaped movable piece 4) and an elastic portion 43 between the movable contact 3 and the terminal 41. The movable piece 4 is fixed by being sandwiched between the resin base 71 and the cover member 72 in the fixed portion 42, and the elastic portion 43 is elastically deformed, whereby the movable contact 3 formed at the tip thereof is pressed against the fixed contact 21 side. Thus, the fixed piece 2 and the movable piece 4 can be energized.

  Further, the movable piece 4 has a through hole 45 that penetrates in the thickness direction of the movable piece 4 and through which the protrusion 74 of the resin base 71 is inserted, a step bent portion 46 formed in a crank shape, and a step bent portion 46. Part of the movable piece 4 in the short direction perpendicular to the longitudinal direction of the movable piece 4, the formed slope 47, the pair of engaging portions 48 engaged with the first positioning portion 75 of the resin base 71 A constricted portion 49 is formed by removing the portion. The through hole 45, the step bent part 46, the slope 47, the engaging part 48, and the constricted part 49 are provided on the opposite side of the movable contact 3 with the elastic part 43 interposed therebetween, that is, on the terminal 41 side with respect to the elastic part 43. ing. The through hole 45 is provided on the center line in the longitudinal direction of the movable piece 4. The slope 47 is formed continuously along the direction of the movable piece 4. The engaging portions 48 are provided at two locations along the short direction of the movable piece 4.

  In addition, a pair of small protrusions 44 are formed on the lower surface of the elastic portion 43 so as to face the thermally responsive element 5. The small protrusion 44 and the thermal response element 5 come into contact with each other, and the deformation of the thermal response element 5 is transmitted to the elastic portion 43 through the small protrusion 44 (see FIGS. 2 and 3). The material of the movable piece 4 is preferably a material mainly composed of phosphor bronze. In addition, a conductive elastic material such as copper-titanium alloy, white or brass may be used. Note that the movable piece 4 is curved or bent at the elastic portion 43 by press working. The degree of bending or bending is not particularly limited as long as the thermally responsive element 5 can be accommodated, and may be set as appropriate in consideration of the elastic force at the operating temperature and the return temperature, the pressing force of the contacts, and the like.

  The through hole 45 is formed in the fixed portion 42 of the movable piece 4. The fixed portion 42 is formed wider than the elastic portion 43 in the short direction of the movable piece 4. Thereby, the cross-sectional area perpendicular to the longitudinal direction of the movable piece 4 in the fixed portion 42 becomes a portion larger than the cross-sectional area in the elastic portion 43. Further, the through hole 45 is formed in an oval shape that is long in the lateral direction of the movable piece 4 in plan view (as viewed in the thickness direction of the movable piece 4).

  The engaging portion 48 is formed at the edge of the constricted portion 49 on the terminal 41 side. The constricted portion 49 is disposed between the fixed portion 42 and the terminal 41 on the opposite side of the elastic portion 43 with the fixed portion 42 interposed therebetween. The width dimension of the constricted portion 49 (the length dimension of the movable piece 4 in the short direction, hereinafter the same) is preferably set equal to or less than the width dimension of the elastic portion 43, but at least the fixed portion 42 and What is necessary is just to set smaller than the width dimension of the terminal 41. FIG. The constricted part 49 in this embodiment has a function as the second elastic part in the above-mentioned Patent Document 1, and absorbs an external force and an impact applied to the terminal 41 and appropriately maintains the position of the movable contact 3. .

  The thermally responsive element 5 has an initial shape curved in an arc shape and is made of a composite material such as bimetal or trimetal. When the operating temperature is reached due to overheating, the curved shape is reversely warped with snap motion, and is restored when the temperature falls below the return temperature due to cooling. The initial shape of the thermoresponsive element 5 can be formed by pressing. As long as the elastic portion 43 of the movable piece 4 is pushed up by the reverse warping operation of the thermal response element 5 at a desired temperature and returns to the original state by the elastic force of the elastic portion 43, the material and shape of the thermal response element 5 are particularly limited. Although not intended, a rectangular shape is desirable from the viewpoint of productivity and efficiency of reverse warping operation, and it is desirable that the rectangular shape is close to a square in order to efficiently push up the elastic portion 43 while being small. Examples of the material of the thermally responsive element 5 include, for example, white, brass, and stainless steel including copper-nickel-manganese alloy or nickel-chromium-iron alloy on the high expansion side and iron-nickel alloy on the low expansion side. A material obtained by laminating two kinds of materials made of various alloys having different coefficients of thermal expansion is used in combination according to the required conditions.

  When the energization of the fixed piece 2 and the movable piece 4 is interrupted by the reverse warping operation of the thermal response element 5, the current flowing through the PTC thermistor 6 increases. As long as the PTC thermistor 6 is a positive temperature coefficient thermistor that limits the current by increasing the resistance value as the temperature rises, the type of operation current, operation voltage, operation temperature, return temperature, etc. can be selected as necessary. The shape is not particularly limited as long as these properties are not impaired.

  The resin base 71 and the cover member 72 constituting the resin case 7 are formed of a resin such as flame retardant polyamide, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), or polybutylene terephthalate (PBT) having excellent heat resistance. ing. The resin base 71 is formed with an opening 73 for accommodating the fixed piece 2, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the like. Note that the edges of the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6 incorporated in the resin base 71 are in contact with each other by a frame formed inside the opening 73, so that the thermal responsive element 5 is reversely warped. It is guided at times.

  The resin base 71 is fitted with a projection 74 inserted through the through hole 45 of the movable piece 4, a pair of first positioning portions 75 for positioning the movable piece 4, and a convex portion 79 of the cover member 72. A pair of concave portions (second positioning portions) 76. The protrusion 74 corresponds to the through hole 45, is formed in an oval shape in plan view, and reinforces the resin base 71. The first positioning portions 75 are provided at two locations along a direction perpendicular to the longitudinal direction of the movable piece 4. In the present embodiment, a part of the side wall of the resin base 71 is formed in a shape corresponding to the constricted portion 49 of the movable piece 4 and constitutes the first positioning portion 75. In other words, the first positioning portion 75 is interposed in a portion cut out in the vicinity of the constricted portion 49 and reinforces the resin base 71. The concave portions 76 are also provided at two locations along the direction perpendicular to the longitudinal direction of the movable piece 4. Note that three or more recesses 76 may be provided. In this case, three or more convex portions 79 corresponding to the concave portions 76 are also provided.

  The cover member 72 includes a stepped portion 77 projecting from the inner wall surface thereof into a shape corresponding to the stepped bent portion 46 of the movable piece 4, a slope 78 (see FIG. 5) formed on the stepped portion 77, and a concave portion of the resin base 71. And a convex portion 79 to be inserted into 76. The slope 78 corresponds to the slope 47 of the movable piece 4 and is continuously formed along a direction perpendicular to the longitudinal direction of the movable piece 4. Two convex portions 79 are provided at positions corresponding to the concave portions 76 of the resin base 71.

  A cover piece 8 is embedded in the cover member 72 by insert molding. The cover piece 8 is formed by pressing a metal plate mainly composed of phosphor bronze or a metal plate such as stainless steel. As shown in FIGS. 2 and 3, the cover piece 8 is in contact with the upper surface of the movable piece 4 as appropriate to restrict the movement of the movable piece 4, and the cover member 72 and the rigidity of the resin case 7 as a casing are also provided. Increase strength.

  As shown in FIG. 1, a cover member 72 is formed on the upper surface of the resin base 71 so as to close the opening 73 of the resin base 71 that houses the fixed piece 2, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the like. Installed. The resin base 71 and the cover member 72 are joined by, for example, ultrasonic welding.

  FIG. 2 shows the operation of the breaker 1 in a normal charge or discharge state. In a normal charging or discharging state, the thermal responsive element 5 maintains the initial shape (before reverse warping), the fixed contact 21 and the movable contact 3 come into contact with each other, and the breaker 1 passes through the elastic portion 43 of the movable piece 4. The terminals 22 and 41 are electrically connected. The elastic part 43 of the movable piece 4 and the thermal responsive element 5 are in contact, and the movable piece 4, the thermal responsive element 5, the PTC thermistor 6 and the fixed piece 2 are electrically connected as a circuit. However, since the resistance of the PTC thermistor 6 is overwhelmingly larger than the resistance of the movable piece 4, the current flowing through the PTC thermistor 6 is substantially larger than the amount flowing through the fixed contact 21 and the movable contact 3. It can be ignored.

  FIG. 3 shows the operation of the breaker 1 in an overcharged state or an abnormality. When the PTC thermistor 6 is overheated due to overcharging or abnormality, the thermal actuator 5 that has reached the operating temperature is warped in reverse, and the elastic portion 43 of the movable piece 4 is pushed up so that the fixed contact 21 and the movable contact 3 Are separated from each other. At this time, the current flowing between the fixed contact 21 and the movable contact 3 is interrupted, and a slight leakage current flows through the thermal actuator 5 and the PTC thermistor 6. Since the PTC thermistor 6 continues to generate heat as long as such a leakage current flows, the resistance value is drastically increased while maintaining the thermally actuated element 5 in the reverse warped state, so that the current is a path between the fixed contact 21 and the movable contact 3. There is only the above-described slight leakage current (which constitutes a self-holding circuit). This leakage current can be used for other functions of the safety device.

  When the overcharge state is canceled or the abnormal state is resolved, the heat generation of the PTC thermistor 6 is also stopped, and the thermal actuator 5 returns to the return temperature and is restored to the original initial shape. Then, the movable contact 3 and the fixed contact 21 come into contact again by the elastic force of the elastic portion 43 of the movable piece 4, the circuit is released from the interruption state, and returns to the conduction state shown in FIG.

  FIG. 4 shows how the movable piece 4 is incorporated into the resin base 71. The movable piece 4 is guided into the openings 73 a and 73 b of the resin base 71 and incorporated into the resin base 71. At this time, the first positioning portion 75 is engaged with the engaging portions 48 on both sides of the constricted portion 49 formed in the movable piece 4, and the protrusion 74 of the resin base 71 is inserted into the through hole 45. Thereby, since the movable piece 4 is guided by the first positioning portion 75 and the protrusion 74, the temporary alignment of the movable piece 4 with respect to the resin base 71 is performed. Further, in addition to the protrusion 74 being inserted into the through hole 45, the engagement of the pair of engaging portions 48 and the pair of first positioning portions 75 restricts the rotation of the movable piece 4 with respect to the resin base 71. Is easily positioned.

  In this temporary alignment stage, it is not necessary that the movable piece 4 is accurately positioned with respect to the resin base 71. Further, the movable piece 4 is placed on the resin base 71 so as to be finally aligned in a later process, and is not fixed. In addition, the positions, shapes, dimensions, and the like of the openings 73a and 73b and the protrusions 74 of the resin base 71 are such that the movable piece 4 can be easily guided from the position where provisional alignment is performed to the fixed position where the positioning is completely performed. It is formed in a similar shape to the corresponding part of the movable piece 4.

  As shown in FIG. 4, after the movable piece 4 is incorporated into the resin base 71, the cover member 72 is attached to the resin base 71. The cover member 72 inserts the convex portion 79 into the concave portion 76 and presses the stepped portion 77 of the cover member 72 against the stepped bent portion 46 of the movable piece 4 to align the movable piece 4 with the resin base 71. Installed.

  FIG. 5 shows the state in which the movable piece 4 is pushed by the cover member 72 while being sandwiched between the resin base 71 and the cover member 72 when the cover member 72 is completely attached to the resin base 71. A section including the portion 79 is shown. When the cover member 72 is pressed in the direction of the resin base 71 while the cover member 72 is being attached to the resin base 71 (the white arrow in the figure), the slope 47 of the movable piece 4 and the slope 78 of the cover member 72. And abut. Since the inclined surface 47 and the inclined surface 78 are continuously formed along the direction perpendicular to the longitudinal direction of the movable piece 4, the movable piece is still pressed when the cover member 72 is pressed in the direction of the resin base 71. The four slopes 47 are pushed (biased) by the slope 78 of the cover member 72 in the longitudinal direction of the movable piece 4. As a result, the direction of the force is changed by the inclined surfaces 78 and 47, and the entire movable piece 4 is pushed and moved in the longitudinal direction, that is, the arrow A direction where the fixed piece 2 exists. At this time, the pair of engaging portions 48 disposed to face the inclined surface 47 and the pair of first positioning portions 75 disposed to face the inclined surface 78 are brought into contact with each other and engaged. As a result, the movable piece 4 that has been temporarily aligned by the protrusion 74 or the like in FIG. 4 is accurately positioned with respect to the resin base 71. That is, the error at the time of temporary alignment that occurs when the movable piece 4 is assembled with the resin base 71 is reduced, and the positioning error of the movable piece 4 with respect to the resin base 71 is substantially reduced. 1 The positioning portion 75 and the engaging portion 48 of the movable piece 4 can be limited to a dimensional error at the time of manufacturing.

  The distance from the engaging portion 48 of the movable piece 4 to the contact location of the movable contact 3 (see FIG. 2) and the distance from the first positioning portion 75 of the resin base 71 to the contact location of the fixed contact 21 (see FIG. 2). The distance is set equal in plan view. Therefore, when the movable piece 4 is accurately positioned, the movable contact 3 and the fixed contact 21 come into contact with each other at an appropriate contact location. Thereby, the contact resistance between both at the time of electricity supply is optimized.

  In the present embodiment, a pair of engaging portions 48 and first positioning portions 75 are provided along the short direction of the movable piece 4. Further, since the pair of engaging portions 48 and the pair of first positioning portions 75 are located on the outer side of the slope 47 and the slope 78 in the short direction of the movable piece 4, the movable piece 4 is rotated. Deviation from the resin base 71 can be suppressed. This also prevents interference between the tip of the movable piece 4 and the resin base 71 even if the clearance between the tip of the movable piece 4 and the opening 73b of the resin base 71 is set small. Further downsizing can be achieved.

  When the cover member 72 is completely attached to the resin base 71, ultrasonic vibration is applied to one or both of the resin base 71 and the cover member 72, and the resin base 71 and the cover member 72 are welded. At this time, the tip of the protrusion 74 of the resin base 71 contacts the inner wall surface of the cover member 72 and is joined by ultrasonic welding. Accordingly, the movable piece 4 is firmly joined from above and below by the resin base 71 and the cover member 72 around the through hole 45, that is, at the fixed portion 42. Thereby, the movable piece 4 is fixed at a fixed position (position where it should be) with respect to the resin base 71. Even after the cover member 72 is welded to the resin base 71 and the movable piece 4 is fixed, the inclined surface 47 and the inclined surface 78 remain in contact with each other, and the movable piece 4 continues to be pushed in the direction of arrow A. Accordingly, the first positioning portion 75 and the engaging portion 48 maintain the engaged state, and the position and posture of the movable piece 4 with respect to the resin base 71 continue to be maintained normally.

  By the ultrasonic welding described above, the top portion of the protrusion 74 and the top portion of the first positioning portion 75 that function as the reinforcing portion are joined to the back surface (lower surface) of the cover member 72 together with the peripheral portion of the resin base 71. Thereby, since the protrusion 74 and the cover member 72 which are reinforcement parts are directly joined in the center vicinity of the fixing | fixed part 42, the rigidity of the resin case 7 can be improved efficiently. In addition, since the first positioning portion 75 that is the reinforcing portion is directly joined to the cover member 72 at the cut-out portion near the constricted portion 49 in plan view, the rigidity of the resin case 7 near the constricted portion 49 is obtained. Can be improved efficiently.

  In the normal charging or discharging state shown in FIG. 2, a current flows in the longitudinal direction of the movable piece 4 from the terminal 41 of the movable piece 4 toward the tip portion where the movable contact 3 is provided. Therefore, if there is a portion where the cross-sectional area perpendicular to the longitudinal direction of the movable piece 4 is smaller than other locations, that portion becomes a bottleneck, the conduction resistance increases, and the power consumed by the breaker 1 increases. Therefore, if the arrangement, shape, size, and the like of the through holes 45 are set taking into account only the rigidity of the resin case 7, the conduction resistance in the peripheral region increases and desired electrical characteristics cannot be obtained. This is because by forming the through hole 45 in the movable piece 4, the cross-sectional area perpendicular to the longitudinal direction of the movable piece 4 in that region, that is, the cross-sectional area of the movable piece 4 as a conductor is reduced.

  In the present embodiment, the position where the through hole 45 is formed is a constricted portion 49 (corresponding to the second elastic portion in Patent Document 1) in which the cross-sectional area perpendicular to the longitudinal direction of the movable piece 4 is smaller than the cross-sectional area of the elastic portion 43. However, since the cross-sectional area of the elastic part 43 is larger than the cross-sectional area of the fixing part 42, an increase in conduction resistance associated with the formation of the through hole 45 can be suppressed. The cross-sectional area in the peripheral region of the through hole 45 depends on the shape and size of the fixed portion 42 and the through hole 45 in addition to the thickness dimension of the movable piece 4, but the cross-sectional area in the peripheral region of the through hole 45 is It is desirable to set the specifications of the fixing portion 42 and the through-hole 45 so that they are equal to or greater than the same cross-sectional area of the elastic portion 43 and the constricted portion 49.

  Further, in order to cope with an increase in local conductive resistance of the movable piece 4 in the peripheral region of the through hole 45, the shape of the through hole 45 is a perfect circle in plan view, or an oval or ellipse that is long in either direction. Is desirable. By making the shape of the through hole 45 an ellipse or an ellipse that is long in either direction in plan view, the balance between the size reduction of the breaker 1 and the rigidity of the movable piece 4 can be easily adjusted. For example, as shown in FIGS. 1 and 4, the length of the movable piece 4 can be reduced by making the through hole 45 an ellipse or ellipse long in the short direction of the movable piece 4 in plan view. This is preferable for further downsizing of the breaker 1. Moreover, the distribution of the bending rigidity and the torsional rigidity of the movable piece 4 can be changed by making the through hole 45 into an oval or elliptical shape that is long in the longitudinal direction of the movable piece 4 in plan view. When the through hole 45 is a rectangular square hole in plan view, it is desirable that the corner is rounded or rounded. For the same purpose, it is desirable that the corner 43a (see FIG. 4) of the elastic portion 43 facing the through hole 45 and the corner 49a (see FIG. 4) of the constricted portion 49 are rounded or rounded. This is because the conductive resistance is suppressed by increasing the cross-sectional area perpendicular to the direction in which the current flows. The through hole 45 may be formed in a wide area from the fixing portion 42 to the step bending portion 46 and the slope 47.

  As described above, according to the breaker 1 of the present embodiment, the through hole 45 is provided in the fixed portion 42 where the cross-sectional area perpendicular to the longitudinal direction of the movable piece 4 is larger than the cross-sectional area of the elastic portion 43. Therefore, the cross-sectional area of the elastic portion is not significantly reduced in the peripheral region of the through hole 45. As a result, it is possible to reduce the size while suppressing the conduction resistance during the normal operation of the breaker 1. And it becomes possible to achieve size reduction of a safety circuit or a secondary battery pack provided with the breaker 1.

  Further, since the through hole 45 is formed at a location where the width dimension in the short direction of the movable piece 4 is larger than the width dimension of the elastic portion 43, the through hole 45 is made uniform in the thickness distribution of the movable piece 4. The reduction in the cross-sectional area of the elastic portion 43 in the peripheral portion of the can be suppressed. Accordingly, it is possible to reduce the size while reducing the manufacturing cost of the movable piece 4 and thus the breaker 1 while suppressing the conduction resistance during the normal operation of the breaker 1.

  Further, since the through hole 45 has an oval shape that is long in the short direction of the movable piece 4 in plan view, the length dimension of the movable piece 4 can be reduced. As a result, the breaker 1 can be further reduced in size. Further, the combination of the movable piece 4 with the structure in which the through hole 45 is formed at a location where the width dimension in the short direction of the movable piece 4 is larger than the width dimension of the elastic portion 43, the movable piece 4 around the through hole 45. A decrease in torsional rigidity can be suppressed.

  Moreover, since the resin base 71 has the protrusion 74 inserted in the through hole 45, the protrusion 74 functions as a reinforcing portion, and the strength and rigidity of the resin case 7 can be efficiently increased. Further, since the movable piece 4 has a constricted portion 49 cut in the short direction, and the first positioning portion 75 of the resin base 71 is interposed in the cut portion of the movable piece 4, the first positioning portion 75 functions as a reinforcing portion, and the strength and rigidity of the resin case 7 can be further increased efficiently.

  The present invention is not limited to the configuration of the above embodiment, and at least the movable piece 4 has a through hole 45 at a location where the cross-sectional area perpendicular to the longitudinal direction is larger than the cross-sectional area of the elastic portion 43. It only has to be.

  The present invention can be variously modified. For example, FIG. 6 shows a movable piece 4 </ b> A as a modification of the movable piece 4. The movable piece 4A is different from the movable piece 4 in that the step bending portion 46 and the inclined surface 47 are eliminated. In this configuration, by eliminating the step bending portion 46 and the inclined surface 47, the longitudinal dimension of the movable piece 4A and the resin base 71 can be reduced, and the breaker 1 can be further downsized. Also in this configuration, the inclined surface 78 of the cover member 72 and the end of the constricted portion 49 of the movable piece 4A on the fixed portion 42 side are brought into contact with each other so that the inclined surface 78 pushes the movable piece 4A in the direction of arrow A. May be. The step bending portion 46 and the slope 47 may be provided outside the resin base 71 as necessary.

  The movable piece 4 </ b> A is the same as the movable piece 4 in that the through hole 45 is formed in the fixed portion 42 in which the width dimension in the short direction of the movable piece 4 is larger than the width dimension of the elastic portion 43. . Further, the shape and size of the through hole 45, the corner 43a of the elastic portion 43, the corner 49a of the constricted portion 49, and the like are the same as those of the movable piece 4.

  FIG. 7 shows a movable piece 4 </ b> B as another modification of the movable piece 4. The movable piece 4B is different from the movable piece 4A in that the constricted portion 49 is eliminated, the movable portion 4B is continuously formed from the fixed portion 42 to the terminal 41, and the through hole 45B is changed to a square hole shape. The corner of the through hole 45B is rounded or rounded. Similarly to the movable piece 4, the shape of the through hole 45 </ b> B may be a perfect circle, an ellipse, or an ellipse in plan view. The size of the through hole 45B, the corner 43a of the elastic portion 43, and the like are the same as those of the movable piece 4. Accordingly, the protrusion 74B of the resin base 71 is also deformed into a shape corresponding to the through hole 45B.

  Further, the projection 74 or 74B inserted through the through hole 45 or 45B may be provided on the cover member 72 side. Similarly, it may be configured such that portions projecting downward from the bottom surface of the cover member 72 are interposed in portions where the movable piece 4 is cut off on both sides of the constricted portion 49.

  In the present embodiment, the self-holding circuit using the PTC thermistor 6 is provided. However, the present invention can be applied to a configuration in which such a configuration is omitted, and the breaker 1 can be reduced in size while suppressing conduction resistance. Can be achieved. Moreover, the structure which forms the movable piece 4 and the thermally responsive element 5 integrally by forming the movable piece 4 with a bimetal or a trimetal etc. may be sufficient. In this case, the configuration of the breaker is simplified, and further miniaturization can be achieved.

  Further, the inclined surface 47 and the inclined surface 78 are not limited to a form in which the inclination angle is constant, and may be an aspect in which the inclination angle gradually increases or decreases. Further, the resin case 7 is not limited to the form constituted by the resin base 71 and the cover member 72, but may be any other form as long as it is constituted by two parts.

  In addition, the present invention may be applied to a structure that is divided into the terminal 41 side and the movable contact 3 side at or near the fixed portion 42 as disclosed in JP-A-2005-203277.

DESCRIPTION OF SYMBOLS 1 Breaker 2 Fixed piece 3 Movable contact 4 Movable piece 5 Thermally responsive element 7 Resin case 21 Fixed contact 43 Elastic part 45 Through hole 49 Constriction part 74 Protrusion

Claims (7)

A fixed piece having a fixed contact;
A movable piece having an elastic part that is elastically deformed and a movable contact at a tip of the elastic part, and pressing the movable contact against the fixed contact;
A thermally responsive element that operates the movable piece so that the movable contact is separated from the fixed contact by being deformed with a temperature change;
In a breaker comprising a resin case for housing the fixed piece, the movable piece, and the thermally responsive element,
The movable piece is
A through hole formed at a location where the cross-sectional area perpendicular to the longitudinal direction of the movable piece is larger than the cross-sectional area of the elastic portion ;
A constricted part excised in the short direction of the movable piece;
A step bent portion bent in a crank shape between the through hole and the constricted portion;
The said resin case protrudes in the shape corresponding to the said step bending part, and has a step part which contact | abuts to this step bending part, The breaker characterized by the above-mentioned. The breaker according to claim 1, wherein the cross-sectional area of the peripheral region of the through hole is equal to or greater than the cross-sectional area of the constricted portion . 3. The breaker according to claim 1 , wherein the cross-sectional area of the step bending portion is larger than the cross-sectional area of the constricted portion and larger than the cross-sectional area of the elastic portion . The breaker according to any one of claims 1 to 3, wherein the through hole is formed in a fixed portion where the movable piece is fixed by the resin case . The breaker according to any one of claims 1 to 4, wherein the through hole is an ellipse or an ellipse that is long in a short direction of the movable piece in plan view . A safety circuit for an electric device comprising the breaker according to claim 1.   A secondary battery pack comprising the breaker according to claim 1.

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