JP6406881B2 - Fuse element - Google Patents

Description

  The present invention relates to a fuse element that is melted by Joule heat when an electric current larger than a rating flows to open an electric circuit.

  In recent years, lithium ion secondary batteries have been adopted in many mobile phones, notebook PCs, and the like. Since lithium ion secondary batteries have high weight energy density, in order to ensure the safety of users and electronic devices, in general, many protection circuits such as overcharge protection and overdischarge protection are built in the battery pack. It has a function of shutting off the output of the battery pack in a predetermined case. However, if the positive / negative electrode insulation fitting portion of the battery corrodes due to water wetting, the pressure inside the battery leaks, and there is a risk that the safety valve does not function correctly and leads to an explosion accident.

  Attaching a sticker that detects wet traces against water wetting and issuing a warning (see, for example, Patent Document 1) does not limit the use of the battery, so migration due to water on the circuit board There is a risk of circuit malfunction due to (insulation deterioration) or a short circuit. Moreover, there is a possibility that the same defect as described above may occur even when the electrolyte leaks due to battery abnormality.

Japanese Patent Laid-Open No. 11-144695 JP 2000-162081 A

  The present invention has been proposed in view of such a conventional situation, and provides a fuse element that can safely open an electric circuit against abnormalities such as water wetting and battery liquid leakage.

In order to solve the above-described problems, a fuse element according to the present invention includes a planar fuse element and an electrode made of a metal that is disposed in the vicinity of the fuse element and has a smaller ionization tendency than the fuse element. The electrode is disposed to face the fuse element .

  According to the present invention, for example, when water enters between the fuse element and the electrode, the electric resistance of the fuse element increases due to the electrolytic corrosion action, and the rated current value decreases, so that the electric circuit can be safely opened. Can do.

FIG. 1 is a perspective view showing a configuration example of a fuse element. FIG. 2 is a perspective view schematically showing the fuse element before electrolytic corrosion. FIG. 3 is a perspective view schematically showing the fuse element after electrolytic corrosion. FIG. 4 is a perspective view showing a configuration example of a fuse element in which a plurality of fuse elements are arranged in parallel. FIG. 5 is a cross-sectional view showing a configuration example of a fuse element in which a plurality of fuse elements are arranged in parallel. FIG. 6 is a block diagram showing an application example in which the fuse element is used in a circuit in a battery pack of a lithium ion secondary battery.

Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings.
1. 1. Configuration example of fuse element Application examples of fuse elements

<1. Example of fuse element configuration>
The fuse element according to the present embodiment includes a fuse element and an electrode made of a metal that is arranged close to the fuse element and has a smaller ionization tendency than the fuse element. Since the fuse element and the electrode are close to each other, the liquid enters between the fuse element and the electrode when there is an abnormality such as water wetting or battery fluid leakage, and the fuse element is eroded. As a result, the electrical resistance increases and the rated current value decreases, so that the electrical circuit can be safely opened by self-interruption by the energization current to the fuse element.

  FIG. 1 is a perspective view showing a configuration example of a fuse element. The fuse element 10 includes a flat fuse element 11 and electrodes 12 </ b> A and 12 </ b> B arranged to face both surfaces of the central portion of the fuse element 11. The fuse element 11 and the electrode 12 are close to each other so that water can enter, and the distance is preferably 0.01 mm to 10 mm. In addition, the smaller the distance between the fuse element 11 and the electrode 12, the greater the electric field strength and the stronger the electric erosion action. Therefore, in order to open the electric circuit more efficiently, the distance between the electrodes 12 is 0.01 to More preferably, it is 1 mm.

  The fuse element 11 has a predetermined rated current value, and blows when a current exceeding the rated current value is energized. The fuse element 11 is preferably composed mainly of any one selected from aluminum, iron, nickel, tin, and lead. In the present specification, the main component refers to a component that is 50 wt% or more based on the total mass of the material.

  The electrodes 12 </ b> A and 12 </ b> B are arranged to face both surfaces of the center portion of the fuse element 11. In addition, the electrodes 12A and 12B are preferably arranged so as to cover the entire surface of the central portion of the fuse element 11 so that the amount of the substance that erodes the fuse element 11 increases.

  Further, the electrodes 12A and 12B are made of a metal having a smaller ionization tendency than the fuse element, and preferably include any one selected from gold, platinum, silver, copper, and palladium as a main component. As a result, when water enters between the fuse element 11 and the electrode 12, the fuse element 11 made of a base metal is ionized (corroded) as a positive electrode, and the fuse element 11 is thinned or a pinhole is generated. As a result, the conductor resistance of the fuse element 11 increases, and the rated current value can be decreased.

  In addition, a separator is preferably provided between the fuse element 11 and the electrode 12. Moreover, it is preferable that a separator consists of insulators, such as a mesh form and a porous form. Thereby, while suppressing the direct short circuit between the fuse element 11 and the electrode 12, the retainability of water and electrolyte solution can be ensured. The separator preferably supports an electrolyte such as NaCl. Thereby, the electrical conductivity of water and electrolyte solution can be improved, and electrolytic corrosion can be promoted.

  A water-absorbing or hygroscopic insulator may be disposed between the fuse element 11 and the electrode 12. Further, an insulator made of sol, gel, or solid may be disposed between the fuse element 11 and the electrode 12, and conductivity may be expressed by water. Further, when an electrolyte made of sol or gel enters between the fuse element 11 and the electrode 12, the electrolytic corrosion action of the fuse element 11 may be exhibited.

  Moreover, it is preferable that the fuse element 11 is connected as a positive electrode and the electrode 12 is connected as a negative electrode. Thereby, the electrolytic corrosion reaction can be promoted, and the rated current value of the fuse element 11 can be quickly reduced.

  That is, the fuse element 10 is composed of a fuse element 11 connected in series as a positive electrode to a DC power source, and a metal that is arranged close to the fuse element 11 and has a lower ionization tendency than the fuse element 11, and is connected as a negative electrode. A cutoff circuit including the electrode 12 is configured. In addition, a first terminal and a second terminal for energizing the fuse element 11 and a third terminal connecting the electrode 12 as a negative electrode are provided, and the first terminal and the second terminal are connected to a positive electrode energization path. Are connected in series, and the third terminal is connected to the negative electrode or grounded.

  2 and 3 are perspective views schematically showing fuse elements before and after electrolytic corrosion, respectively. As shown in FIG. 2, the fuse element 11 before electrolytic corrosion maintains a short shape. When water intrudes between the fuse element 11 and the electrode 12, the fuse element 11 made of a base metal is ionized (corroded) as a positive electrode as shown in FIG. May occur. For this reason, the conductor resistance of the fuse element 11 increases, and the rated current value decreases. Although heat and electrolyte between the fuse element 11 and the electrode 12 may evaporate due to heat generation due to an increase in the conductor resistance, the rated current value is reduced, so that the self-current due to the energizing current to the fuse element 11 It can be shut off and the electrical circuit can be opened safely.

  Further, the fuse element is not limited to the above-described configuration example, and for example, a plurality of fuse elements may be arranged in parallel and electrodes may be arranged between the fuse elements. FIG. 4 is a perspective view showing a configuration example of a fuse element in which a plurality of fuse elements are arranged in parallel, and FIG. 5 is a cross-sectional view showing a configuration example of the fuse element in which a plurality of fuse elements are arranged in parallel. As shown in FIG. 5, the fuse element includes a first electrode 22A, a first separator 23A, a first fuse element 21A, a second separator 23B, a second electrode 22B, and a third electrode. Separator 23C, second fuse element 21B, fourth separator 23D, third electrode 22C, fifth separator 23E, third fuse element 21C, sixth separator 23F, 4 electrodes 22D are stacked in this order.

  The first to third fuse elements 21A, 21B, 21C, the first to fourth electrodes 22A, 22B, 22C, 22D, and the first to sixth separators 23A, 23B, 23C, 23D, 23E, 23F These are the same as the above-described fuse element 11, electrode 12, and separator, respectively, and description thereof is omitted here.

  By arranging a plurality of fuse elements in parallel in this way, the rated current can be increased, and electrolytic corrosion of the fuse elements when water enters between the fuse elements and the electrodes can be promoted.

<2. Application example of fuse element>
FIG. 6 is a block diagram showing an application example in which the fuse element is used in a circuit in a battery pack of a lithium ion secondary battery. As shown in FIG. 6, for example, the fuse element 10 is used by being incorporated in a battery pack 30 having a battery stack 35 including battery cells 31 to 34 of a total of four lithium ion secondary batteries.

  The battery pack 30 includes a battery stack 35, a charge / discharge control circuit 40 that controls charging / discharging of the battery stack 35, a fuse element 10 that cuts off the output of the battery stack 35 when an abnormality occurs, and the voltages of the battery cells 31 to 34. And a detection circuit 36 for detection.

  The battery stack 35 is formed by connecting battery cells 31 to 34 that need to be controlled for protection from overcharge and overdischarge states, and is detachable via the positive electrode terminal 30a and the negative electrode terminal 30b of the battery pack 30. Are connected to the charging device 45, and a charging voltage from the charging device 45 is applied thereto. By connecting the battery pack 30 charged by the charging device 45 to the positive terminal 30a and the negative terminal 30b to an electronic apparatus that operates with a battery, the electronic apparatus can be operated.

  The charge / discharge control circuit 40 includes two current control elements 41 and 42 connected in series to a current path flowing from the battery stack 35 to the charging device 45, and a control unit 43 that controls the operation of these current control elements 41 and 42. Is provided. The current control elements 41 and 42 are configured by, for example, field effect transistors (hereinafter referred to as FETs), and control of the gate voltage by the control unit 43 to control conduction and interruption of the current path of the battery stack 35. To do. The control unit 43 operates by receiving power supply from the charging device 45 or the battery stack 35, and cuts off the current path when the battery stack 35 is overdischarged or overcharged according to the detection result by the detection circuit 36. In addition, the operation of the current control elements 41 and 42 is controlled.

  The fuse element 10 includes a first terminal and a second terminal for energizing the fuse element 11, and a third terminal connecting the electrode 12 as a negative electrode. For example, the first terminal and the second terminal Is connected on the charge / discharge current path between the battery stack 35 and the charge / discharge control circuit 40, and the third terminal is connected to the negative electrode side.

  The detection circuit 36 is connected to each of the battery cells 31 to 34, detects the voltage value of each of the battery cells 31 to 34, outputs a signal to the current control element 38 in the event of an abnormality, and supplies the signal to the current control element 38. Breaks the discharge current path.

  The protection element 37 is connected, for example, on a charge / discharge current path between the battery stack 35 and the charge / discharge control circuit 40, and its operation is controlled by the current control element 38. The protective element 10 has, for example, a circuit configuration including a soluble conductor and a heating element that melts the soluble conductor by energizing and generating heat through a connection point of the soluble conductor, and the soluble conductor is filled with the soluble element. The heating element is connected to the current control element 38 in series on the discharge current path.

  The current control element 38 operates the protection element 37 when the voltage value of the battery cells 31 to 34 exceeds a predetermined overdischarge or overcharge state by the detection signal output from the detection circuit 36, Control is performed so that the charge / discharge current path of the battery stack 35 is cut off regardless of the switching operation of the current control elements 31 and 32.

  According to such an application example, water enters between the fuse element 11 and the electrode 12 at the time of abnormality such as water leakage, and the fuse element 11 is eroded. As a result, the rated current value is lowered, so that the current can be shut off by the energizing current to the fuse element 11 and the electric circuit can be opened safely.

  In addition, when the fuse element 11 is connected as a positive electrode and the electrode 12 is connected as a negative electrode in order to efficiently open an electric circuit in the event of an abnormality, the connection destination of the third terminal of the fuse element 10 is particularly limited. It is not something. For example, when the third terminal is connected to the detection circuit 36, it is possible to detect that water has entered between the fuse element 11 and the electrode 12. Further, for example, using a primary battery, the positive electrode side may be connected to the fuse element 11 and the negative electrode side may be connected to the third terminal. Further, the third terminal may be grounded. In addition, since the metal having a large ionization tendency is eroded simply by immersing two metals having different ionization tendencies in the electrolyte, the third terminal may be opened.

10 fuse elements, 11 fuse elements, 12 electrodes, 21A, 21B, 21C 1st to 3rd fuse elements, 22A, 22B, 22C, 22D 1st to 4th electrodes, 23A, 23B, 23C, 23D, 23D, 23E, 23F First to sixth separators, 30 battery pack, 30a positive terminal, 30b negative terminal, 31-34 battery cell, 35 battery stack, 36 detection circuit, 37 protection element, 38 current control element, 40 charge / discharge control Circuit, 41, 42 Current control element, 43 Control unit, 45 Charging device

Claims (8)

A planar fuse element;
An electrode made of a metal arranged close to the fuse element and having a smaller ionization tendency than the fuse element ;
A fuse element in which the electrode is disposed to face the fuse element. The fuse element is mainly composed of any one selected from aluminum, iron, nickel, tin, lead,
2. The fuse element according to claim 1, wherein the electrode is composed mainly of any one selected from gold, platinum, silver, copper, and palladium.   The fuse element according to claim 1, wherein the electrode is disposed so as to face both surfaces of a central portion of the fuse element.   The fuse element according to claim 1, further comprising a separator between the fuse element and the electrode.   The fuse element according to claim 4, wherein the separator carries an electrolyte. A plurality of the fuse elements are arranged in parallel,
The fuse element according to claim 1, wherein the electrodes are arranged between the fuse elements. The fuse element is connected as a positive electrode,
The fuse element according to claim 1, wherein the electrode is connected as a negative electrode. A fuse element connected in series as a positive electrode to a DC power source;
An interrupting circuit comprising: an electrode that is disposed in the vicinity of the fuse element, made of a metal that has a smaller ionization tendency than the fuse element, and is connected as a negative electrode.

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