JP6417220B2 - Protective element - Google Patents

Description

  The present invention relates to a protection element having a PTC element and a thermal fuse member, and more particularly to a protection element for protecting an electric device, for example, a secondary battery pack, from an excess current and / or an excess voltage. The present invention also relates to a protection circuit including such a protection element.

  Conventionally, thermal fuse elements, current fuse elements, polymer PTC elements, and the like have been used to protect electrical devices from excessive current. However, in a chargeable / dischargeable secondary battery pack or the like, not only protection from excessive current but also protection from excessive voltage may be required to prevent overcharge.

  As a protective element for protecting an electric device such as a secondary battery from such an excessive current and / or an excessive voltage, for example, a low melting point metal member (corresponding to a thermal fuse member) and a heating element are provided on a substrate, A protection element has been proposed in which a heating element is energized by a detection element that detects this abnormality, and a thermal fuse member is blown by heat generated from the heating element to interrupt the circuit (see Patent Document 1).

  However, in the protective element as described above, a resistor (heating element) and a thermal fuse under the influence of the heat are arranged on the ceramic substrate. From the structure, a plurality of thermal fuses are arranged in parallel in the element. There is a problem that it is difficult to arrange, and therefore the rated capacity of the current cannot be increased (for example, in the case of an existing protection element, the rated current is about 15 A). For this reason, in order to cope with a device requiring a large current such as a power tool, a single element cannot be used, and a plurality of, for example, four protection elements must be used in parallel. There is a problem that it becomes complicated and it becomes difficult to reduce the size.

JP 7-153367 A

  Therefore, the problem to be solved by the present invention is to provide protection against excess current and / or voltage, and even in an electric circuit that flows a relatively large current, for example, 30 A or more. It is an object of the present invention to provide a protective element that can appropriately protect an electric circuit with the element.

In the first aspect, the present invention provides:
A PTC element having a layered PTC element, a first conductive metal layer located on one main surface thereof, and a second conductive metal layer located on the other main surface;
An insulating layer located on the second conductive metal layer of the PTC element;
A thermal fuse member positioned on the insulating layer; a first lead connected to one end of the thermal fuse member; a second lead connected to the other end; and a portion of the second lead Is electrically connected to the second conductive metal layer,
A protective element is provided.

  The protection element of the present invention causes a current to flow from the switching element to the PTC element in response to excess voltage and / or excess current, thereby bringing the PTC element into a high temperature / high resistance state, that is, causing the PTC element to trip. The thermal fuse member is melted by the generated Joule heat. That is, in the protection element of the present invention, the thermal fuse member is under the thermal influence of the PTC element in the trip state.

  The protective element of the present invention includes a PTC element having a layered PTC element, a first conductive metal layer located on one main surface thereof, and a second conductive metal layer located on the other main surface. Have. In the protective element of the present invention, the PTC element is not particularly limited, but is preferably a so-called polymer PTC element. The polymer PTC element is formed by extruding a conductive polymer composition containing, for example, a polymer (eg, polyethylene, polyvinylidene fluoride, etc.) and a conductive filler (eg, nickel filler, carbon filler, etc.) dispersed therein. It can be obtained by obtaining an extrudate as a layered PTC element and thermocompression-bonding a conductive metal to both main surfaces thereof. A person skilled in the art can select an appropriate PTC element according to the characteristics and application of the protection element of the present invention.

  The PTC element of the present invention functions as a heating element by tripping to a high temperature / high resistance state in response to an excess voltage and / or an excess current. Further, the PTC element of the present invention has a function as a substrate for holding a temperature fuse member and the like in addition to a function as a heating element. By using a polymer PTC element as a substrate, processing such as cutting is facilitated and the structure of the protection element is simplified as compared with the case of using a ceramic substrate. Furthermore, it is not necessary to dispose a resistor as a heating element on the substrate, and the entire substrate (that is, the PTC element) generates heat substantially uniformly. Therefore, a plurality of temperature fuse members can be disposed on the substrate. It becomes possible.

  The protective element of the present invention comprises an insulating layer located on the second conductive metal layer of the PTC element. This insulating layer electrically insulates the first lead and the second conductive metal layer of the PTC element. With such a structure, after the thermal fuse member is melted, the current flow path from the first lead to the second lead via the PTC element can be interrupted.

  The insulating layer is made of an insulating material. Although it does not specifically limit as an insulating material, Preferably resin, ceramic, silicone, insulating oil, paper, etc. are mentioned. In particular, those excellent in thermal conductivity are preferable. By using an insulating material having excellent thermal conductivity, Joule heat generated in the PTC element can be more efficiently transmitted to the thermal fuse member. Such an insulating material having excellent thermal conductivity is not particularly limited, and examples thereof include ceramic and silicone.

  The insulating layer is not necessarily required to cover the entire second conductive metal layer of the PTC element. After the thermal fuse member is melted, leads on both ends of the thermal fuse member are interposed via the second conductive metal layer of the PTC element. The shape and arrangement of the insulating layer are not particularly limited as long as the current flowing between the first lead and the second lead described below can be interrupted. For example, the insulating layer has a part of the second conductive metal layer exposed. Can be arranged to do. Thus, by exposing a part of the second conductive metal layer, it is possible to facilitate electrical connection between the second conductive metal layer and the second lead.

  The thickness of the insulating layer is not particularly limited, but may be 10 to 100 μm, preferably 30 to 60 μm. The thinner the insulating layer, the more efficiently Joule heat generated in the PTC element can be transmitted to the thermal fuse member. Moreover, in order to ensure electrical insulation between the thermal fuse member and the second conductive metal layer, it is preferably 30 μm or more.

  The protective element of the present invention comprises a thermal fuse member located on the insulating layer. Preferably, the thermal fuse member has leads (hereinafter referred to as a first lead and a second lead, respectively) as terminals (electrodes) connected to both ends thereof. This fuse member is formed of a metal material having a predetermined melting point, for example, Sn, Bi, Pb, Cd, In, Ga, Zn or the like. A person skilled in the art can appropriately select, obtain or manufacture such a thermal fuse member according to desired characteristics in consideration of the temperature at the time of trip of the PTC element.

  A plurality of, for example, 2 to 10, and preferably 2 to 4 thermal fuse members can be arranged in parallel on the PTC element. By increasing the number of thermal fuse members in parallel, the rated capacity of the current of the protection element of the present invention can be increased.

  The thermal fuse member is disposed so as to be under the thermal influence of the PTC element. That is, the thermal fuse member is arranged to be blown by Joule heat generated in the tripped PTC element. Preferably, the thermal fuse member is entirely disposed on the insulating layer. By arranging in this way, when an excess voltage and / or excess current is detected, a current is passed through the PTC element, and the PTC element trips, the thermal fuse member is blown by Joule heat generated in the PTC element, A current interruption can be secured. The first lead connected to one end of the thermal fuse member should not be in contact with the second conductive metal layer of the PTC element, and preferably the connecting portion between the fuse member and the first lead is located on the insulating layer. Placed in. On the other hand, a part of the second lead connected to one end of the thermal fuse member is electrically connected to the second conductive metal layer of the PTC element. By arranging in this way, the path from the first lead to the second lead through the second conductive metal layer of the PTC element is blocked by the insulating layer, so that after the thermal fuse member is blown, the first and It is possible to reliably prevent a current from flowing between the second leads and to secure a current flowing through the PTC element.

  In another aspect, the protection element of the present invention further includes a second thermal fuse member connected in series to the PTC element. The second thermal fuse member may be connected in series or in parallel to the first thermal fuse member, but is preferably connected in series.

  The second thermal fuse member is under the thermal influence of the PTC element, and when an excess voltage and / or excess current is detected, current is passed through the PTC element, and the PTC element trips, the Joule generated in the PTC element Fusing by heat. By disposing such a second thermal fuse member, even after the thermal fuse member on the PTC element (hereinafter also referred to as the first thermal fuse member) is blown, the switching element is connected to the circuit via the PTC element. It is possible to cut off the inflowing minute current (leakage current) and make the circuit completely open. Examples of the second thermal fuse member include those similar to those used for the first thermal fuse member.

  The second thermal fuse member may be the same as or different from the first thermal fuse member. When the second thermal fuse member is the same as the first thermal fuse member, the second thermal fuse member is also connected in series to the first thermal fuse member, or the first thermal fuse member It is preferable that the installation conditions, for example, the distance from the PTC element, and the like are adjusted so as to be cut after the thermal fuse member. Further, when the second thermal fuse member is different from the first thermal fuse member, the second thermal fuse member has a characteristic of being blown after the first thermal fuse member. Is preferred. A person skilled in the art can appropriately select the type and arrangement of the second thermal fuse member according to desired characteristics.

  In yet another aspect, the protection element of the present invention includes a current fuse member connected in series to the first thermal fuse member. The current fuse member is blown when an excessive current flows in the circuit. That is, by arranging such a current fuse member, it is possible to more quickly and reliably protect the circuit from excessive current. A person skilled in the art can appropriately select a current fuse member to be used according to desired characteristics.

  In yet another aspect, the protection element of the present invention includes a second PTC element and a second PTC element connected in series to the second PTC element and under the thermal influence of the second PTC element. 3 thermal fuse members, which are connected in parallel to the first thermal fuse member (and the current fuse member and the second thermal fuse member, if present). With such a configuration, when the first thermal fuse member (and the current fuse member and the second thermal fuse member, if present) is blown, the current flowing therethrough is The commutation to the circuit on the second PTC element side can suppress the generation of an arc accompanying the fusing of the fuse member. That is, the voltage resistance of the protective element of the present invention can be improved. Further, after the first thermal fuse member (and the current fuse member and the second thermal fuse member, if present) is blown, a joule generated in the second PTC element tripped by the commutated current is generated. The third thermal fuse member is melted by heat, and a minute current passing through the second PTC element can be completely cut off. When the third thermal fuse member is blown, only a very small current flows through the circuit, so that it can be safely shut off.

In the second aspect, the present invention provides:
There is provided a protection circuit comprising the protection element of the present invention and a switching element for energizing the PTC element of the protection element in response to an excess current and / or an excess voltage.

  In the protection circuit of the present invention, the protection element of the present invention includes, for example, a first lead connected to a power source, a second lead connected to a protected device, a first conductive metal layer connected to a switching element, The two conductive metal layers are connected to the protected device through the second lead. When an excess current and / or an excess voltage occurs, the switching element supplies current to the PTC element accordingly, the PTC element trips to a high temperature / high resistance state, and the thermal fuse member is blown by Joule heat generated in the PTC element. Then, the circuit is opened and the protected device is protected.

  In the protection circuit of the present invention, examples of the switching element include a field effect transistor element (hereinafter also referred to as “FET”). Among them, the FET is particularly preferable because a current can be passed through the PTC element in accordance with an abnormal voltage. When other switching elements are used, there may be a need for a mechanism that detects excess voltage and / or excess current and causes the switching elements to start energizing the PTC element.

  In a third aspect, the present invention relates to an electric device (for example, a secondary battery pack, particularly an electric vehicle, a cordless cleaner, an electric tool, a radio base station, or the like having a protective element or a protective circuit). Used, in particular for high voltage and / or high current).

  The protection element of the present invention protects a circuit from excessive current and / or excessive voltage while allowing a large current, for example, 30 A or more, to flow because a plurality of thermal fuse members can be arranged on the PTC element. Enable. In addition, since the PTC element and the first lead portion are electrically insulated by the insulating layer, the flow path from the first lead to the second lead via the PTC element is surely cut off after the thermal fuse member is melted. Can be.

FIG. 1 is a schematic side view of one embodiment of the protection element of the present invention. FIG. 2 is a schematic plan view of the protection element of FIG. FIG. 3 is a circuit diagram schematically showing a protection circuit including the protection element of FIG. FIG. 4 is a circuit diagram schematically showing a protection circuit including another embodiment of the protection element of the present invention. FIG. 5 is a circuit diagram schematically showing a protection circuit including still another embodiment of the protection element of the present invention. FIG. 6 is a circuit diagram schematically showing a protection circuit including still another aspect of the protection element of the present invention.

  The protection element of the present invention will be described in detail with reference to the drawings. However, it should be noted that the protection element of the present invention is not limited to the illustrated example.

  FIG. 1 shows a schematic side view of one embodiment of the protection element of the present invention, FIG. 2 shows a schematic plan view of the protection element shown in FIG. 1, and FIG. 3 further includes the protection element of FIG. A protection circuit is schematically shown as an equivalent circuit. In FIG. 3, the portion surrounded by the dotted line corresponds to the protective element of the present invention.

  As shown in FIG. 1 and FIG. 2, the protection element 10 of the present embodiment includes a layered PTC element 12, a first conductive metal layer 14 positioned on one main surface thereof, and a main surface on the other side. A PTC element 18 having a second conductive metal layer 16; an insulating layer 20 positioned on the second conductive metal layer 16 of the PTC element 18; and a heat of the PTC element 18 positioned on the insulating layer 20 It has a fuse member 22 under influence, and a first lead 24 and a second lead 26 located at both ends thereof. Further, as shown in FIG. 1, a part of the second lead 26 is electrically connected to the second conductive metal layer 16 of the PTC element 18, and the second conductive metal layer 16 and the device to be protected are connected. Also serves as an electrical connection. As shown in FIG. 2, in this aspect, there are four thermal fuse members, which are collectively connected to the first lead and the second lead, but the protection element of the present invention is limited to this aspect. Not. For example, each fuse member may have a separate first lead and second lead, and there may be two, three, or five thermal fuses.

  In this embodiment, for example, when an excessive voltage is generated between the contacts a and b shown in FIG. 3, the FET passes a current between the contacts a and FET and the contact c. This current causes the PTC element 18 to trip and generate heat, and the heat causes the thermal fuse member 22 under the thermal influence of the PTC element 18 to melt and cut off the current (however, a minute current flows through the PCT element). sell). In this way, the protected devices connected to the contact x and the contact y are protected.

  FIG. 4 schematically shows another embodiment of the protection element of the present invention in an equivalent circuit. In FIG. 4, the portion surrounded by the dotted line corresponds to the protection element of the present invention. This embodiment has a second thermal fuse member 30 connected in series to the PTC element 18 in addition to the embodiment of FIG. The second thermal fuse member 30 is under the thermal influence of the PTC element 18. That is, the second thermal fuse member 30 is melted by Joule heat generated in the tripped PTC element 18.

  In this embodiment, a minute current between the contact a-FET and the contact c that can flow through the PTC element 18 even after the thermal fuse member 22 is cut by the Joule heat generated in the PTC element 18 is used as the second temperature fuse. The member 30 can be cut off by fusing with the heat of the PTC element 18, and a complete open of the circuit can be achieved. The arrangement of the second thermal fuse member 30 is not limited to the illustrated position as long as it is connected in series to the PTC element 18 and is under the thermal influence of the PTC element.

  FIG. 5 schematically shows still another aspect of the protection element of the present invention in an equivalent circuit. In FIG. 5, the portion surrounded by the dotted line corresponds to the protection element of the present invention. This embodiment has a current fuse member 40 connected in series to the thermal fuse member 22 in addition to the embodiment of FIG. Since the current fuse member 40 is blown quickly when an excess current is generated, the protection against the excess current can be made quicker and more reliable. The arrangement of the current fuse member 40 is not particularly limited as long as it is in series with the thermal fuse member 22, but the PTC element 18 is arranged as shown in the drawing so that a minute current that can flow through the PTC element 18 can be cut off. It is preferable to connect in series.

  FIG. 6 schematically shows still another aspect of the protective element of the present invention in an equivalent circuit. In FIG. 6, a portion surrounded by a dotted line corresponds to the protection element of the present invention. This embodiment has a second PTC element 50 and a third thermal fuse member 52 in parallel with the thermal fuse member 22 and the current fuse member 40 in addition to the embodiment of FIG. The third thermal fuse member 52 is connected in series to the second PTC element 50 and is under the thermal influence of the second PTC element 50, but the thermal influence of the PTC element 18 is substantially reduced. I do not receive it. In this embodiment, when the thermal fuse member 22 is blown against an excessive voltage, or when the current fuse member 40 is blown by an excessive current, the thermal fuse member 22 and the current fuse member 40 are connected between the contacts de. A part of the current flowing through the current flows through the circuit on the second PTC element 50 side. As a result, the generation of an arc when the thermal fuse member 22 or the current fuse member 40 is blown is suppressed. Thereafter, all the current between the contact points d and e flows to the second PTC element 50, the second PTC element 50 trips and generates heat, the third thermal fuse member 52 is blown, and the second PTC element 50 is blown. The minute current flowing through is cut off. In this aspect, the arrangement of each PTC element, current fuse member, and each temperature fuse member is not limited to the illustrated example as long as they are connected so as to exhibit the effects described above. Those skilled in the art can appropriately select such an arrangement.

  The protective element of the present invention can be used in various electric devices as, for example, a protective element for a secondary battery.

DESCRIPTION OF SYMBOLS 10 Protection element 12 Layered PTC element 14 1st electroconductive metal layer 16 2nd electroconductive metal layer 18 PTC element 20 Insulating layer 22 Thermal fuse member 24 1st lead 26 2nd lead 30 2nd thermal fuse member 40 Current fuse member 50 Second PTC element 52 Third thermal fuse member

Claims (8)

A PTC element having a layered PTC element, a first conductive metal layer located on one main surface thereof, and a second conductive metal layer located on the other main surface, and functioning as a substrate;
An insulating layer located on the second conductive metal layer of the PTC element;
A plurality of temperature fuse members located on the insulating layer, each of which is arranged in parallel; a first lead connected to one end of each of the temperature fuse members; and the other of the temperature fuse members A second lead connected to an end of the second lead, wherein a part of the second lead is electrically connected to the second conductive metal layer,
A protective element comprising:   The protection element according to claim 1, wherein the second thermal fuse member is connected in series to the PTC element. The protection element according to claim 2 , wherein two or more of the second thermal fuse members exist in parallel.   The protection element according to claim 1, further comprising a current fuse member connected in series to the temperature fuse member. A protection circuit comprising: the protection element according to claim 1; and a switching element for energizing the PTC element of the protection element in response to an excess current and / or an excess voltage.   The protection circuit according to claim 5, wherein the switching element is a field effect transistor.   An electric device comprising the protective element according to claim 1 or the protective circuit according to claim 5 or 6.   The electric device according to claim 7, wherein the electric device is a secondary battery cell.

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