Protection element

Abstract

The present invention provides a protection device which includes a laminar element 16 which is formed of an insulation resin and has at least one throughhole; electrically conductive metal thin layers 22 and 28 which are positioned on each of main surfaces of the laminar element, and a fuse layer 40 which is positioned on a side surface defining said at least one throughhole and electrically connects the electrically conductive metal thin layers. The fuse layer includes a first metal layer 41 consisting of a metal having a higher melting point and a second metal layer 42 consisting of a metal having a lower melting point. The protection device of the present invention allows a larger amount of a current to flow therethrough and can provide a protection from an excessive current.

Claims

1. A protection device which comprises: an annular laminar element formed of an insulation resin and having a first throughhole at a radial center thereof; an annular metal foil positioned on each main surface of the laminar element and coaxial with the laminar element; an annular electrically conductive metal thin layer positioned on each of the metal foils and coaxial with the laminar element; and a first fuse layer disposed on a side surface defining the first throughhole and electrically connecting the electrically conductive metal thin layers, wherein the fuse layer comprises a first metal layer and a second metal layer, the first metal layer formed of a metal having a higher melting point than a metal from which the second metal layer is formed.

2. The protection device according to claim 1, characterized in that the metal having the higher melting point is Ni.

3. The protection device according to claim 1, characterized in that the metal having the lower melting point has a melting point lower than a decomposition temperature of the insulation resin.

4. The protection device according to claim 3, characterized in that the metal having the lower melting point is Sn, an SnCu alloy or an SnBi alloy.

5. The protection device according to claim 1, characterized in that the first metal layer is formed by electroless plating with the metal having the higher melting point and the second metal layer is formed by electrolytic plating with the metal having the lower melting point on the first metal layer.

6. The protection device according to claim 1, characterized in that a thickness ratio between the first metal layer and the second metal layer is 1:100 to 5:1.

7. The protection device according to claim 1, characterized in that the electrically conductive metal thin layer and the fuse layers are formed to be integral by plating with the metal having the higher melting point and the metal having the lower melting point.

8. The protection device according to claim 1, characterized in that the metal foil is a nickel foil.

9. The protection device according to claim 1, characterized in that the laminar element includes an inner periphery surface and an outer periphery surface, the inner periphery surface defining the first throughhole, the protection device further comprising a second throughhole positioned between the inner periphery surface and the outer periphery surface, the second throughhole having a second fuse layer disposed on a side surface thereof.

10. A secondary battery cell comprising a protection device which comprises: an annular laminar element formed of an insulation resin and having a first throughhole at a radial center thereof; an annular metal foil positioned on each main surface of the laminar element and coaxial with the laminar element; an annular electrically conductive metal thin layer positioned on each of the metal foils and coaxial with the laminar element; and a first fuse layer disposed on a side surface defining the first throughhole and electrically connecting the electrically conductive metal thin layers, wherein the fuse layer comprises a first metal layer and a second metal layer, the first metal layer formed of a metal having a higher melting point than a metal from which the second metal layer is formed.

11. The secondary battery cell according to claim 10, characterized in that the metal having the higher melting point is Ni.

12. The secondary battery cell according to claim 10, characterized in that the metal having the lower melting point has a melting point lower than a decomposition temperature of the insulation resin and is Sn, an SnCu alloy or an SnBi alloy.

13. A washer which comprises: an annular laminar element formed of an insulation resin and having a first throughhole at a radial center thereof; an annular metal foil positioned on each main surface of the laminar element and coaxial with the laminar element; an annular electrically conductive metal thin layer positioned on each of the metal foils and coaxial with the laminar element; and a first fuse layer disposed on a side surface defining the first throughhole and electrically connecting the electrically conductive metal thin layers, wherein the fuse layer comprises a first metal layer and a second metal layer, the first metal layer formed of a metal having a higher melting point than a metal from which the second metal layer is formed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a protection device of the present invention in a cross-sectional view along its thickness-direction;

(2) FIG. 2 schematically shows in a plane view the protection device which is shown in FIG. 1;

(3) FIG. 3 schematically shows in a cross-sectional view a fuse layer in the protection device which is shown in FIGS. 1 and 2;

(4) FIG. 4 schematically shows a protection device of the present invention of other embodiment in a cross-sectional view along its thickness-direction;

(5) FIG. 5 schematically shows the protection device in a plane view which is shown in FIG. 4; and

(6) FIG. 6 schematically shows in a cross-sectional view a fuse layer in the protection device which is shown in FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE INVENTION

(7) The protection device of the present invention will be described in detail with reference to the accompanied drawings. In FIG. 1, one embodiment of the protection device of the present invention is schematically shown in a cross-sectional view along its thickness-direction (a portion which appears as the cut plane is indicated with an arrow A). Also, in FIG. 2, the protection device shown in FIG. 1 is schematically shown in a plane view. Furthermore, in FIG. 3, a fuse layer in the protection device shown in FIGS. 1 and 2 is schematically shown in a cross-sectional view.

(8) The illustrated protection device 10 comprises an annular laminar element 16 which is formed of the insulation resin and has at least one throughhole (in the illustrated embodiment, two throughholes of a central throughhole 12 having a circular cross-section and a surrounding throughhole 14 having a circular cross-section). The protection device 10 comprises electrically conductive metal thin layers 22 and 24 which are positioned on both main surfaces 18 and 20 respectively of the laminar element 16. It is noted that in the illustrated embodiment, separate metal layers 26 and 28 are present between the laminar element 16 and the electrically conductive metal thin layers.

(9) In the illustrated embodiment, the fuse layer is absent on an inner periphery 30 of the circular ring which defines the central throughhole, i.e. on a side surface inside of the annular ring. In the illustrated embodiment, a fuse layer 40 is present on a peripheral side surface 38 which defines the surrounding throughhole 14 positioned through a main body 36 of the laminar element between the inner periphery 30 and the outer periphery 34.

(10) In the illustrated embodiment, the fuse layer 40 consists of a first metal layer 41 located on the peripheral side surface 38 which defines the surrounding throughhole 14 and a second metal layer 42 located on the first metal layer 41.

(11) In the illustrated embodiment, the surrounding throughhole 14 having the fuse layer 40 is only one which is provided at the midpoint of the main body 36 along the diameter (shown with a broken line in FIG. 2) passing through a center O of the laminar element, but such surrounding throughhole may be provided at the opposite side along the diametrical direction. In this case, it results in providing surrounding throughholes at every 180 (totally providing two throughholes) around the center O. In a further other embodiment, three, four, six or eight of the surrounding throughholes having the fuse layer may be provided at an equal angle interval of 120, 90, 60 or 45 around the center O of the circle, respectively.

(12) It is noted that since the diameter of the central throughhole is far larger than the diameter of the surrounding throughhole, the fuse layer is absent on the side surface of the inner periphery 30 of the annular ring. However, the fuse layer may be provided on the side surface of the inner periphery 30 of the annular ring if necessary when the diameter of the central throughhole is the similar to or smaller than the diameter of the surrounding throughhole. It is noted that in a certain embodiment, when a convex part corresponding to the central throughhole is provided to an electrical apparatus to which the protection device is to be disposed, the protection device may be located on the electrical apparatus by fitting the convex part into the large diameter part of the central throughhole. For example, such convex part is provided on a sealing plate of a secondary battery cell, so that the convex part is fitted into the central throughhole, and thereby enabling to position the protection device on the sealing plate.

(13) In other embodiment, the laminar element 16 does not have the central throughhole 12 (therefore, the laminar element is in a disk-shape) and has only at least one surrounding throughhole 14 which may have the fuse layer 40.

(14) A protection device 10 of a further embodiment of the present invention is shown in FIGS. 4 and 5 similarly to FIGS. 1 and 2. A fuse layer 32 is shown in FIG. 6 similarly to FIG. 3. It is noted that the same reference numerals are used for the same elements as in FIGS. 1-3. In the illustrated embodiment, the laminar element 16 does not have the surrounding throughhole 14 and has only the central throughhole 12 which has the fuse layer 32. The fuse layer 32 consists of a first metal layer 43 located on the inner periphery 30 which defines the central throughhole 12 and a second metal layer 44 located on the first metal layer 43.

Example 1

(15) The protection device of the present invention shown in FIGS. 1 and 2 was produced. Therefore, the protection device 10 was produced which has only the fuse layer 40 but does not have the fuse layer 32. It is noted that eight surrounding throughholes 14 were circumferentially formed at an equal angle interval.

(16) First, a sheet of an insulation resin (made of polyethylene, having a thickness of 0.3 mm, corresponding to the laminar element 16) was prepared, nickel foils (having a thickness of 22 m, corresponding to the separate metal layers 26 and 28) were positioned on the both side of the sheet, and they were pressed while heating to be integral to obtain a pressure-bonded product wherein the nickel foils were applied to the both main surfaces.

(17) Throughholes (corresponding to the surrounding throughhole 14) which were of 0.6 mm in a diameter were formed at prescribed positions of the pressure-bonded product, and then plating the pressure-bonded product with Ni by an electroless plating process. The thickness of the nickel layer which was formed by Ni-plating was about 1.5 m. Then, the pressure-bonded product was plated with Sn by an electrolytic plating process. The thickness of the tin layer which was formed by Sn-plating was about 6.5 m. By such plating processes, the electrically conductive metal thin layers (corresponding to the electrically conductive metal thin layers 22 and 24), and the fuse layer (corresponding to the fuse layer 40) consisting of the first metal layer (corresponding to the first metal layer 41) and the second metal layer (corresponding to the second metal layer 42) were obtained. Then, the annular element was stamped out from the pressure-bonded product to obtain the protection device 10 of the present invention wherein eight throughholes were positioned in place at every 45 around the center of the annular element as prescribed.

(18) The diameter of the outer peripheral circle 34 of the obtained circular annular element was 15 mm, and the diameter of the obtained inner peripheral circle 30 (i.e. the diameter of the central throughhole) was 6.4 mm. This circular annular element had nickel foils functioning as the separate metal layers 26 and 28 on the both main surfaces of the insulation resin layer as the laminar element 16, and had the surrounding throughholes 14 at the midpoint of the maim body 36 which was a part of the circular annular element. Also, the circular annular element had plated layers (the nickel plated layer and the tin plated layer) as the electrically conductive metal thin layers 22 and 24 on the nickel foils, and had plated layers functioning as the fuse layers 40 consisting the first metal layers 41 and the second metal layers 42 on the inner peripheral surfaces which define the surrounding throughholes.

Examples 2 and 3

(19) The protection devices of Examples 2 and 3 were obtained similarly to Example 1 except that SnCu plating (Cu 4% by weight) and SnBi plating (Bi 16% by weight) were conducted in place of tin-plating, respectively.

Comparative Examples 1 to 3

(20) The protection devices of Comparative Examples 1-3 were obtained similarly to Example 1 except that nickel-plating were conducted in place of tin-plating, and the thickness of the nickel plated layer formed by the nickel plating was 4.5, 6.5 and 8.5 m, respectively.

(21) Characteristics of Examples 1-3 and Comparative Example 1-3 are shown below.

(22) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Electroless plated material Ni Ni Ni Electrolytic plated Sn SnCu SnBi material (Cu 4 wt %) (Bi 16 wt %) Thickness of electroless 1.5 1.5 1.5 plate (m) Thickness of electrolytic 6.5 6.5 6.5 plate (m) Total plate thickness 8.0 8.0 8.0 (m) Higher melting point plate/ 23.1 23.1 23.1 Lower melting point plate ratio (%) Comparative Comparative Comparative Example 1 Example 2 Example 3 Electroless plated material Ni Ni Ni Electrolytic plated Ni Ni Ni material Thickness of electroless 1.5 1.5 1.5 plate (m) Thickness of electrolytic 4.5 6.5 8.5 plate (m) Total plate thickness 6.0 8.0 10.0 (m) Higher melting point plate/ 33.3 23.1 17.6 Lower melting point plate ratio (%)

(23) Experiment 1: A current listed in following Table 2 was passed through the protection devices of Examples 1-3 and Comparative Examples 1-3 from one electrically conductive metal thin layer 22 to the other electrically conductive metal thin layer 24, and a current value which does not cause a blow was evaluated even when the current was passed for 10 minutes (at 60 Vdc). The maximum value of current which continues to flow without blowing (melting) of the fuse layer was defined as rated capacity. The results are shown in Table 2. It is noted that denotes no blow occurred for 10 minutes, x denotes the blow occurred within 10 minutes, and denotes no data is available.

(24) TABLE-US-00002 TABLE 2 Com- Com- Com- parative parative parative Current Exam- Exam- Exam- Exam- Exam- Exam- Value ple 1 ple 2 ple 3 ple 1 ple 2 ple 3 10 A 15 A 17.5 A 20 A 22.5 A 25 A x x 30 A x x x x

(25) Experiment 1: A current which was 150%, 200%, 300% and 400% of a rated capacity was passed through the protection device of Examples 1-3 and Comparative Examples 1-3 from one electrically conductive metal thin layer 22 to the other electrically conductive metal thin layer 24, and a current-interrupted time (i.e. time which elapsed before the fuse layer was blown) was measured. The results are shown in following Table 3.

(26) TABLE-US-00003 TABLE 3 Elapsed time before blowing (second) Com- Com- Excessive Com- parative parative Current Exam- Exam- Exam- parative Exam- Exam- (%) ple 1 ple 2 ple 3 Example 1 ple 2 ple 3 150 4.80 13.1 2.00 no blow no blow no blow within within within 30 sec 30 sec 30 sec 200 1.64 1.65 0.80 3.56 3.80 4.50 300 0.29 0.21 0.19 0.25 0.26 0.29 400 0.07 0.04 0.04 0.06 0.07 0.07

(27) From these results, it has been confirmed that the protection device of the present invention provides rapid and sure protection with an excessive current about 1.5 times its rated capacity.

(28) The protection device of the present invention can be used as a protection device which interrupts an excessive current when the excessive current flows in an electrical apparatus such as a secondary battery. The protection device of the present invention can also be used as an alternative to a nickel washer, a washer in which a stainless material is nickel-plated or the like which is for example incorporated into a sealing plate in a cylindrical lithium ion secondary battery cell. In this case, since the protection device has the laminar element which is formed of the insulation resin, the function of the protection device as a washer is increased due to elasticity of the resin. Therefore, the present invention can also be used as a washer which has characteristics of the protection device of the present invention as described above.

(29) The element reference numerals are: 10, 10protection device; 12central throughhole 14surrounding throughhole; 16laminar element 18, 20main surface; 22, 24electrically conductive metal thin layer 26, 28other metal layer; 30inner periphery 32fuse layer; 34outer periphery 36main body; 38side surface; 40fuse layer 41first metal layer; 42second metal layer 43first metal layer; 44second metal layer