JP4170232B2 - Safety device using bimetal - Google Patents

Description

  The present invention relates to a safety device for an electrical product having bimetal and PTC as essential components for interrupting current when an overcurrent flows through the electrical product or when the temperature of the electrical product rises excessively.

  Conventionally, safety devices using bimetal cut off the current to ensure safety when abnormalities occur, such as when an overcurrent flows in a motor such as an automobile or home appliance, or when the temperature rises excessively. Used as a protective device. In recent years, with the miniaturization and high performance of electrical equipment, there is a need for a safety device that is reliably secured and downsized. For example, safety devices for secondary batteries used in mobile phones and notebook computers, safety devices for DC circuits such as automobile motors and chargers, safety devices for AC circuits such as air conditioner fans and washing machines, etc. There is a need for highly safe and miniaturized safety devices.

  When the bimetal is used as a safety part of an electrical product, when the temperature of the electrical product rises excessively, the bimetal changes its shape (hereinafter referred to as “operation”), and is turned off to interrupt the current. However, if the temperature drops due to the interruption of the current, the bimetal will return to its pre-operational shape, turn on, current will flow, and energization may begin before safety is secured, improving safety. It was sought after.

As this improvement method, a safety device using a bimetal and a heating resistor in combination has been developed (see Patent Document 1). In this proposal, an electrical product and a bimetal are connected in series, and a PTC that is a heating resistor is connected in parallel. Under normal conditions, most of the current flows through the bimetal, the current flowing through the PTC is very small, and the temperature rise of the PTC is hardly seen. However, when an abnormality such as a temperature rise occurs, the bimetal is activated and turned off, the current flowing through the bimetal is interrupted, and all the current flows through the PTC. As the amount of current flowing through the PTC increases, a large amount of Joule heat is generated, the temperature of the PTC rises significantly, the bimetal continues to be heated, and the bimetal is kept off. In order to perform such an operation, a safety device in which bimetal and PTC are combined is an effective device with high safety.
JP 7-153499 A

  The safety device described in Patent Document 1 is used by using bimetal and PTC, and connecting each with an electrical product. However, in order to electrically connect bimetal and PTC to electrical products, there are restrictions on the shape and miniaturization of bimetal and PTC due to the provision of contacts on bimetal and PTC and connection to the power supply circuit. There was a limit to thinning. Further, the provision of the contact point to the bimetal and the connection of the power supply circuit are technically complicated and require many processes, resulting in poor productivity.

  An object of the present invention is to provide a safety device using a bimetal that is excellent in safety, small in size, and high in productivity.

In order to achieve the above object, the invention of claim 1 includes a resin case in which components including an arm terminal, a movable arm, a base terminal, a bimetal, and a temperature thermistor (hereinafter referred to as PTC) are capable of receiving the temperature of an electrical product. Built-in, the arm terminal, the movable arm and the base terminal are connected in series, and the current of the electrical product flows normally, and when the bimetal is activated due to the temperature rise, the movable arm is displaced and the movable arm and the base terminal In a safety device using a bimetal configured to be disconnected from the
The bimetal is normally installed in the resin case in a movable state, and the bimetal and the PTC are installed in a state in which they are not connected to an electric circuit. , PTC and the base terminal are brought into conduction.

  According to a second aspect of the present invention, in the safety device using the bimetal according to the first aspect, a cover terminal is incorporated between the cover of the resin case and the movable arm so that the movable arm is displaced when the bimetal is operated. It is what.

  The invention of claim 3 is a PTC in which an electrode is applied to 30 to 98% of the PTC surface facing the bimetal and the base terminal in the safety device using the bimetal according to claim 1 or claim 2. It is characterized by.

  A fourth aspect of the present invention is the safety device using the bimetal according to any one of the first to third aspects, wherein the PTC surface excluding the surface to which the electrode is applied is coated with a coating agent. It is characterized by that.

  According to a fifth aspect of the present invention, in the safety device using the bimetal according to any one of the first to fourth aspects, the base terminal has a protrusion for installing the PTC.

  According to the present invention, the bimetal and the PTC are installed in a state where they are not connected to the electric circuit, and the safety is high by using the bimetal and the PTC together. And since bimetal and PTC do not require contact processing for flowing current and connection processing with an electric circuit, the shape of bimetal and PTC is made as small and thin as possible as long as the function is not impaired. Things can be used. Moreover, since the space for wiring becomes unnecessary, the resin case itself can be downsized. Furthermore, a contact processing step for bimetal and PTC and a connection processing step with an electric circuit become unnecessary.

Hereinafter, a safety device using a bimetal according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a safety device. The safety device 1 is connected to an electrical product by an electrical circuit (not shown), and is a device that protects the electrical product from an overcurrent and an abnormal temperature rise that occur when the electrical product is used. In this safety device 1, a base terminal 3 is installed on a base 2a of a resin case 2 ready to receive the temperature of an electrical product, and a movable arm 7 connected to a PTC 4, a bimetal 5 and an arm terminal 6 is sequentially provided thereon. These are assembled and covered with a cover 2b of the resin case 2 from above. The PTC 4 and the bimetal 5 have conductivity, but neither has a contact or wiring for flowing electricity. The bimetal 5 is in contact with the movable arm 7 and is movable on the PTC 4 as shown in FIG. 1 or on the shelf 2c of the base 2a of the resin case 2 as shown in FIG. Installed at.

  One end of the base terminal 3 and the arm terminal 6 is led out to the outside of the resin case 2 and is connected to an electric product and an electric circuit, respectively. The movable arm 7 and the arm terminal 6 are connected by a known method such as welding or bolting. The movable arm 7 and the arm terminal 6 are preferably connected to each other as shown in FIG. 1, but the movable arm 7 and the arm terminal 6 may be integrated. The base terminal 3 and the movable arm 7 are arranged in contact with each other. In order to ensure contact between the base terminal 3 and the movable arm 7, it is preferable to have contacts 3a and 7a, respectively. Moreover, although the base 2a and the base terminal 3 of the resin case 2 may be separate parts, it is preferable that they are integrated by insert molding. The base 2a and the cover 2b of the resin case 2 are bonded together by welding or an adhesive.

FIG. 3 is a sectional view showing another embodiment of the safety device of the present invention.
In this example, the base terminal 3, the PTC 4, the bimetal 5, the movable arm 7 connected to the arm terminal 6, and the cover terminal 8 are built in the resin case 2 constituted by the base 2 a and the cover 2 b of the resin case 2. The cover terminal 8 is a component having an intermediate restraint 8 a and a stopper 8 b and is installed between the movable arm 7 and the cover 2 b of the resin case 2. When the temperature of the movable arm 7 exceeds a predetermined temperature due to an abnormal temperature rise of the electrical product, the bimetal 5 is activated. Since the working width of the bimetal 5 varies depending on the degree of temperature rise, the pushed-up width of the movable arm 7 pushed up by the bimetal 5 also fluctuates, and the movable arm 7 and the base terminal 3 are not sufficiently separated from each other. The movable arm 7 may be deformed by hitting the cover 2b of the case 2. For this reason, the bimetal 5 may be enlarged or the distance between the movable arm 7 and the cover 2b of the resin case 2 may be increased.

The cover terminal 8 has an intermediate retainer 8a and a stopper 8b, and even when the movable arm 7 is pushed down by a small width, the movable arm 7 comes into contact with the intermediate retainer 8a and the stopper 8b. By increasing the pushed-up width, the contact 7a of the movable arm 7 and the contact 3a of the base terminal 3 can be reliably separated. The intermediate restraint 8a may be provided at a position corresponding to the central portion 7c of the movable arm 7, and the shape and the like are arbitrary. As shown in FIG. 3, the stopper 8b is provided between the contact 7a of the movable arm 7 and the central portion 7c at a position close to the contact 7a. The shape is not particularly limited. One or both of the intermediate restraint 8a and the stopper 8b may be installed. Moreover, the cover terminal 8 can be integrated with the cover 2b of the resin case 2, and the space between the cover 2b of the resin case 2 and the movable arm 7 can be made as narrow as possible. By incorporating the cover terminal 8, the current can be reliably interrupted even when the movement width of the movable arm 7 is small, and the space between the resin case 2 and the cover 2 b can be narrowed. It is possible to reduce the thickness. The cover 2b and the cover terminal 8 of the resin case 2 may be separate parts, but it is preferable that the cover 2b and the cover terminal of the resin case 2 are integrated by insert molding. In addition, the movable arm 7 has a projection 7 b at a location where the bimetal 5 is operated to contact the movable arm 7.
By providing the projection 7b, even if the operation amount of the bimetal 5 is small, the movable arm 7 can be surely pushed up, so that a small bimetal can be used, and the space between the bimetal 5 and the movable arm 7 can be used. It is also possible to narrow down.

  Next, the operation of the safety device 1 of the present invention will be described with reference to FIGS. While the electrical product is being used safely, the safety device 1 is connected to the electrical product (not shown) at the point where the arm terminal 6 and the base terminal 3 are led out. In the safety device 1, the movable arm 7 connected to the arm terminal 6 and the base terminal 3 are in contact with each other, and electricity flows. The PTC 4 and the bimetal 5 are held in a state where no electricity flows. When the temperature of the electrical product rises abnormally, the temperature of the movable arm 7 rises, and as shown in FIG. 4, the bimetal 5 operates to push up the movable arm 7 and the movable arm 7 and the base terminal 3 are disconnected. As a result, the electrical product enters a current interruption (off) state. At this time, the bimetal 5 comes into contact with the PTC 4, whereby the arm terminal 6, the movable arm 7, the bimetal 5, the PTC 4, and the base terminal 3 (all of which are conductive) are connected, and a current flows through the PTC 4. When the current flows, the PTC 4 generates a large amount of Joule heat, the temperature rises, and the bimetal 5 is heated until the power is cut off. Therefore, the bimetal 5 keeps the movable arm 7 pushed up. As a result, the movable arm 7 and the base terminal 3 are kept in the current interrupted state. Most of the current flowing through the PTC 4 is used for heat generation, and the current flowing through the base terminal 3 is very small, so that the safety of the electrical product can be maintained.

Next, components used in the present invention will be described.
As the bimetal 5, a known bimetal is used. For example, a laminate of two materials of Cu—Ni—Mn on the high thermal expansion side and Ni—Fe on the low thermal expansion side is used. Although the operating temperature and the return temperature vary depending on the requirements of the electric product used, in the present invention, a bimetal having an operating temperature of 90 ± 25 ° C. and a return temperature of 50 ± 15 ° C. is preferable. Since the bimetal 5 used in the present invention does not need a contact and does not need to be connected to an electric circuit, the longest part of the bimetal having a length of about 2 to 4 mm can be used.

  The PTC 4 is an element that generates a large amount of Joule heat when a current flows and maintains a high temperature. As PTC4, a ceramic sintered body or a polymer in which conductive particles such as carbon are dispersed is used. In the present invention, a ceramic sintered body containing barium titanate is preferable and used. In addition to barium titanate, strontium titanate, calcium titanate, and the like may be included. In the present invention, the PTC 4 preferably has a resistance value range of 5 to 20Ω and a resistance sudden change point temperature (Curie temperature) of 65 to 90 ° C. The shape of the PTC 4 is not particularly limited, and various shapes such as a cylindrical shape and a prismatic shape can be used. An example of a cylindrical shape is shown in FIGS. Although PTC4 can be used without an electrode, as shown in FIG. 5, the one provided with electrodes 4a and 4b is preferably used. Since the PTC 4 does not need to be connected to an electric circuit, a PTC 4 having a small shape can be used as long as it has characteristics. A cylindrical shape having a diameter of 1.5 to 2.5 mm and a thickness of 0.2 to 0.4 mm can be used.

  When electrodes are applied to the surface of the PTC 4, as shown in FIG. 6, the electrode 4 a is applied to the surface of the PTC 4 that contacts the activated bimetal 5, and the electrode 4 b is applied to the surface of the PTC 4 that contacts the base terminal 3. The electrode is applied to the surface of the PTC 4 by a known method. For example, a conductive powder obtained from gold, silver, platinum, copper, aluminum or a compound of these metals, or a mixture thereof is dispersed in an organic system such as a polyester polymer, an epoxy resin or an acrylic resin. The electrode paste mixed and dispersed in the agent is applied to a predetermined surface of PTC4 by a method such as screen printing, coater, hand coating, machine coating, or by electroless plating of silver, nickel, copper, etc. . As shown in FIG. 5, the electrodes 4a and 4b on the surface of the PTC 4 are applied at a distance of 0.01 mm or more, preferably 0.05 mm or more from the outermost end of the PTC 4. The thickness of the electrodes 4a and 4b is not particularly limited, but is 0.001 mm or more, preferably 0.003 to 0.2 mm. The electrode is provided at 30 to 98%, preferably 50 to 95% of the surface of the PTC4.

  The ceramic PTC 4 is fragile as is well known, and may be damaged when the safety device 1 is manufactured or used. If a broken piece of the PTC 4 is present in the resin case 2 of the safety device 1, an electrical failure such as non-conduction may be caused, and the function as the safety device may be impaired. Therefore, in the present invention, PTC4 in which one or more parts of the surface of PTC4 to which no power is applied is coated with a coating agent is preferable and used.

  For the surface coating of PTC4, a known organic or inorganic coating agent can be used. The surface coating is performed on the surface of the PTC 4 excluding the electrode portions 4a and 4b. This surface coat is desirably coated on the entire surface of the PTC 4 except for the electrode portions 4a and 4b. However, if even one portion is coated, there is an effect of preventing damage to the PTC 4. Therefore, if even one part is coated, it is within the scope of the present invention. In addition, it is preferable that the coating agent is impregnated not only on the surface of PTC 4 but also the inside, since the damage prevention effect is large. Although there is no restriction | limiting in particular in the thickness of a coat, The thinner one is preferable and it is 0.3 mm or less, Preferably, it is 0.001-0.1 mm.

A known organic or inorganic coating agent is used as a material for coating the surface of PTC4. Examples of organic coating agents include polyester polymers, polyurethane polymers, polyamide polymers, polyester ether polymers, polyester urethane polymers, polyolefin polymers, polycarbonate polymers, polyamide polymers, and other known thermoplastic polymers and thermoplastics. Epoxy-based, acrylic-based, urethane-based, and silicone-based thermosetting resins and photosensitive resins that can be cured by elastomers, ultraviolet rays, heat, and the like can be used.
Among these, epoxy type, acrylic type, urethane type, and silicone type resins that are cured by ultraviolet rays, heat, etc., can be easily applied to the surface of PTC4, easily impregnated inside PTC4, and have an effect of preventing damage. Since it is high, it is preferably used.

  The surface of the PTC 4 is coated with the organic coating agent by a known coating method such as screen printing, coater, hand coating, machine coating, or dipping. Although the specific example of a coat is described below, it is not limited to these methods. When the thermoplastic resin is coated, the resin is dissolved in an appropriate solvent by about 0.1 to 10%, and the solution is thinly applied to the surface of the PTC 4 and then the solvent is removed by drying or the like.

  In the case of epoxy, acrylic, urethane, or silicone coatings that are cured by ultraviolet rays, visible light, or heat, a predetermined time required for curing is required after thinly applying these coating agents to the PTC4 surface by a known method. The surface of the PTC 4 can be coated by irradiating with ultraviolet light, visible light or the like, or by heating. Moreover, it can coat also by the method of painting the surface of PTC4.

  The PTC 4 is placed so that the electrode 4 b of the PTC 4 is in contact with the upper surface of the base terminal 3. Although the upper surface of the base terminal 3 may be smooth, the contact between the electrode 4b of the PTC 4 and the upper surface of the base terminal 3 may become unstable, and the contact area may vary. In order to ensure contact between the electrode 4b of the PTC 4 and the upper surface of the base terminal 3 and stabilize the contact area, it is preferable to provide unevenness and protrusions 3b on the upper surface of the base terminal 3 as shown in FIG. When the protrusions 3b are provided on the upper surface of the base terminal 3, the number and shape of the protrusions 3b are not particularly limited as long as the PTC 4 can be held in a stable state. Usually, the number of the protrusions 3b is preferably 3 to 5. Although the example of arrangement | positioning of the processus | protrusion 3b was shown to Fig.8 (a) (b), it is not limited to this. The protrusion can be provided at the same time when the base terminal 3 is pressed. Alternatively, a conductive material can be attached to the upper surface of the base terminal 3 by a method such as welding to form the protrusion 3b.

  In addition, the PTC 4 may be installed on the base terminal 3 in a movable state. However, in order to reliably install in a stable state, the PTC 4 and the base terminal 3 are bonded to each other as shown in FIG. You may fix by 9 etc. In this case, it is preferable to use an adhesive containing silver, aluminum, copper powder or the like in order to prevent the electrical conductivity from being lowered by the adhesive 9 used for fixing. In addition, when fixing PTC4 to the base terminal 3 with the adhesive agent 9, it may be with or without said protrusion 3b. The fixing method is performed by dropping the adhesive 9 on the upper surface of the base terminal 3 and placing the PTC 4 on the PTC 4 with a little pressure.

  The base terminal 3 and the arm terminal 6 are made of copper, nickel or the like, and the movable arm 7 is made of a conductive metal material such as copper, stainless steel or titanium. The cover terminal 8 does not particularly need conductivity, but it is preferable to use a metal material such as copper or stainless steel. The base terminal 3, the arm terminal 6, the movable arm 7, and the cover terminal 8 are all manufactured by pressing.

  When the electric product is normally used, the base terminal 3 and the movable arm 7 are in contact and energized. A contact 7 a is provided at the tip of the movable arm 7 in order to improve the power supply to the base terminal 3. The surface of the contact 7a of the movable arm 7 and the surface of the contact surface 3a of the base terminal 3 may be the same as the material surface, but the contact may become unstable and energization may be hindered. Therefore, it is preferable to roughen one or both of the surface of the contact 7a of the possible arm 7 and the contact surface 3a of the base terminal 3 to increase the contact area. As a roughening method, the surface may be roughened by a known method such as cutting the surface portion of the contact 7a or the contact surface 3a of the base terminal 3 with a scissors, providing unevenness during pressing, or hitting with a metal material. Further, there is a method in which metals collide with each other, for example, a contact 7a of the movable arm 7 and a contact surface 3a of the base terminal 3 are collided. The roughening point is appropriately determined depending on the range in which the contact 7a of the movable arm 7 operates.

  The resin case 2 uses a resin such as polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polybutylene terephthalate (PBT), polyamide (PA), etc., and the resin case 2 covers the cover 2a and the resin case 2 by injection molding. It is obtained by separately molding the base 2b. After the base terminal 3, the PTC 4, the bimetal 5, the arm terminal 6, the movable arm 7, and the cover terminal are assembled, the base 2 a and the cover 2 b of the resin case 2 are bonded by ultrasonic melting, an adhesive, or the like. The base 2a and the cover 2b of the resin case 2 may be individually injection molded, the base 2a of the resin case 2 may be insert-molded with the base terminal 3, and the cover 2b may be insert-molded with the cover terminal 8. In addition, a metal material can also be used for the cover 2b of the resin case 2.

  The safety device of the present invention includes a protection switch in place of a fusing fuse used as a safety device when an overcurrent flows or when the temperature rises abnormally, an overcurrent protection switch for AC or DC power output, a power supply for a circuit board Used for overcurrent protection switch installed at the supply inlet. Specific examples include electric products such as batteries, electric kotatsu, electric blankets, rice cookers, automobiles, and temperature sensors for industrial equipment. It can be used for the above various electric products, and after the bimetal 5 is activated and cuts off the current, the Joule heat of the PTC 4 can prevent the bimetal 5 from returning, so that there is a possibility of trouble due to overcurrent. It is preferably used for electrical products. In addition, the bimetal 5 of the present invention is movably installed, and both the bimetal 5 and the PTC 4 do not require a circuit for connecting to a power source. Therefore, the shape and size are not limited, and the bimetal 5 can be made as small and thin as possible. It is suitable as a safety device for electrical products. In addition, this invention is not restricted to the said embodiment, A various deformation | transformation utilization is possible.

Sectional drawing of the safety device which concerns on one Embodiment of this invention. Sectional drawing when the bimetal in a safety device same as the above is placed on the base shelf of the resin case. Sectional drawing of a safety device same as the above which has a cover terminal as another Example. Sectional drawing of the state which the bimetal act | operated by abnormal temperature rise in a safety device same as the above. (A) and (b) are a front view and a side view of a cylindrical PTC used in the safety device. Sectional drawing of the safety device with which PTC provided with the electrode as a modification was installed. Sectional drawing when using the base terminal with the protrusion for installing PTC as a modification. (A) and (b) are the front view and side view of a base terminal which have the said protrusion. Sectional drawing when PTC and a base terminal are being fixed as a modification.

Explanation of symbols

1 Safety Device 2 Resin Case 2a Resin Case Base 2b Resin Case Cover 3 Base Terminal 3a Base Terminal Contact 3b Base Terminal Protrusion 4 PTC
5 Bimetal 6 Arm terminal 7 Movable arm 7a Movable arm contact 8 Cover terminal

Claims (4)

Components including an arm terminal, a movable arm, a base terminal, a bimetal, and a temperature thermistor (hereinafter referred to as PTC) are built in a resin case that can receive the temperature of an electrical product. The arm terminal, the movable arm, and the base terminal are A bimetal that is connected in series and that is in a state where electric current flows normally, and when the bimetal operates due to temperature rise, the movable arm is displaced and the connection between the movable arm and the base terminal is cut off. In the safety device using
An electrode is applied to 30 to 98% of the PTC surface facing the bimetal and the base terminal, and the electrode is obtained by mixing and dispersing conductive powder in an organic dispersant,
In the resin case, the bimetal is normally installed in a movable state, and the bimetal and the PTC are installed in a state not connected to an electric circuit,
A safety device using a bimetal, wherein the movable arm, the bimetal, the PTC, and the base terminal are in a conductive state in a shut-off state due to the bimetal operation.   The safety device using a bimetal according to claim 1, wherein a cover terminal is incorporated between the cover of the resin case and the movable arm so that the movable arm is displaced when the bimetal is operated. The safety device using a bimetal according to claim 1 or 2 , wherein the PTC surface excluding the surface to which the electrode is applied is a PTC coated with a coating agent. The safety device using a bimetal according to any one of claims 1 to 3 , wherein the base terminal has a protrusion for installing the PTC.

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