JP2021027021A - Fuse element - Google Patents

Abstract

To provide a fuse element having a narrow part which has excellent durability performance and quick cutoff performance for an abnormal overcurrent in a normal use state.SOLUTION: A thin plate metal 1 having a narrow part is sandwiched between a pair of thick plate metals 2 having a plurality of punched holes 3 in an intermediate part and plated with tin, and joined by joining means or the like, such as thermocompression bonding, whereby a narrow thin plate metal part exposed from the punched hole forms a narrow portion 4 of a fuse element, a remaining punched hole part in the thick plate metal forms a wide part 5 which plays a role of a heat dissipation plate, and both end parts form a terminal part 7.SELECTED DRAWING: Figure 6

Description

The present invention relates to a fuse element of a fuse used in a high voltage and highly fluctuating large current flow circuit such as an EV or HEV main circuit.

The main circuit connected to high-voltage lithium-ion batteries such as EVs and HEVs, which are expanding on a global scale, causes great damage when a large current such as a short circuit flows. Therefore, a fuse is fused to achieve current cutoff quickly. The ^{fuse element is soluble by dissipating Joule heat generated in a narrow part for reducing I 2} t) and a long overcurrent of several seconds that frequently occurs due to acceleration or braking during normal driving. There is a demand for a fuse element having a wide portion that keeps the temperature of the portion below a certain temperature.

For the above purpose, the conventional fuse element is generally a fuse element in which a circular or diamond-shaped hole or a notch is welded to a metal plate and punched in parallel or in series by a press to form a narrow portion and a wide portion. Furthermore, in order to solve the complexity of the assembly process due to the difference between the metal plate thickness that satisfies the electrical performance required for the fuse element and the metal plate thickness of the electrode required for the fuse, the middle part of the metal plate is made thicker according to the fusing performance in advance. There is a fuse element in which a hole or notch is punched after being crushed.

Japanese Unexamined Patent Publication No. 2004-119105 Japanese Unexamined Patent Publication No. 2009-272184

According to the above-mentioned prior art, the narrow portion of the fuse element can be crushed to obtain a thickness according to the fusing performance, but the narrow portion that is most affected by thermal and mechanical stress during long-term use is large. Crushing and processing causes embrittlement due to work hardening, which reduces the durability against repeated thermal expansion and contraction due to earthquake resistance and current changes, and cutting processing for forming narrow portions reduces the chemical activity of the cut surface. There is a risk that it will be raised and corrosion will easily occur in a narrow area, reducing reliability.

In addition, the width of the narrow portion formed by punching a circular or diamond-shaped hole for forming a fuse element by press working and remaining adjacent to the hole does not cause deformation of the hole, so the hole diameter or outer shape is cut according to the plate thickness. Due to the restriction that the notch width needs to be about 1.5 times the plate thickness and about twice the plate thickness from the end of the hole to the end of the hole or the outer shape, a small fuse I ^{2 to achieve a quick current cutoff.} It is difficult to secure the cross-sectional area for obtaining t, and if the plate thickness of the crushed portion is made extremely thin in order to forcibly secure the ratio, there arises a problem that the mechanical strength is lowered.

The present invention has been made to solve the problems described above, the place of interest fusing time required for the circuit to be protected - a fuse element having a current characteristic and fusing I ^{2 t} can block quickly abnormal overcurrent Is to provide.

The fuse element according to claim 1 for solving the above problems is formed by sandwiching a thin plate metal having a narrow portion between a pair of thick plate metals having a plurality of punched holes in an intermediate portion and tin-plated, and thermocompression bonding or the like. The narrow thin plate metal part exposed from the punched hole forms a narrow part of the fuse element, and the remaining part of the thick plate metal punched hole forms a wide part that plays the role of a heat radiating plate. Both ends thereof form a terminal portion.

The fuse element according to claim 2 is the fuse element according to claim 1, characterized in that narrow portions of thin metal plates are connected in a row or in parallel.

The fuse element according to claim 3 is the fuse element according to claim 2, characterized in that the fuse element is exposed from a hole in a thick plate metal and the planar shape of a narrow portion is S-shaped.

The fuse element according to claim 4 is the fuse element according to claim 1, wherein a thin plate metal having a narrow portion is made of a linear metal.

The fuse element according to claim 5 is the fuse element according to claim 4, characterized in that a narrow linear metal forms a spiral shape.

In the fuse element of the present invention, in order to solve the above problems, a thin plate metal having a narrow portion is sandwiched between a pair of thick plate metals having a plurality of punched holes in the intermediate portion and tin-plated, and joined by thermal pressure bonding or the like. By joining by means or the like, the narrow thin plate metal part exposed from the punched hole forms a narrow part of the fuse element, and the remaining part of the thick plate metal punched hole forms a wide part that plays the role of a heat dissipation plate, and both ends thereof. By forming a terminal part, the cross-sectional area and shape of the narrow part can be freely set, so that the fusing time required for the circuit-current characteristics and fusing to achieve rapid abnormal overcurrent interruption I ² There is an advantage that t can be obtained.

On the other hand, the wide part, which plays the role of a heat dissipation plate, can be molded with the same plate thickness as the fuse electrode, so that the manufacturing process can be simplified without the need for the process of assembling electrodes with different plate thicknesses, and rapid melting. Since the narrow part in charge is made of linear metal or narrow thin plate metal, it is durable against repeated thermal expansion and contraction due to earthquake resistance and current change without causing work hardening due to unreasonable crushing and processing like the conventional fuse element. There is an advantage that a highly reliable fuse element having excellent properties can be obtained.

It is a perspective view which shows an example of the fuse to which the fuse element of this invention is applied. It is a perspective view before sandwiching a thin plate metal having a narrow part of the fuse element of FIG. 1 between thick plate metals. It is a perspective view when the thin plate metal having the narrow part of the fuse element of FIG. 2 is sandwiched between the thick plate metal. It is a perspective view before cutting off the unnecessary part of the fuse element of FIG. 2 and assembling into a fuse container. It is a perspective view when the fuse element of FIG. 2 is incorporated in a fuse container. It is a perspective view which showed only the fuse element of FIG. It is a top view of the fuse element of FIG. It is a side view of the fuse element of FIG. It is sectional drawing of AA'in FIG. It is a perspective view before sandwiching the linear metal which becomes the narrow part of another Example of a fuse element with a thick plate metal. It is a top view and the enlarged view when the narrow part forms an S shape in another embodiment of a fuse element. It is a graph which shows the blow time-current characteristic of the fuse element of this invention. This is a fuse element of Patent Document 1 cited as a prior art. This is a fuse element of Patent Document 2 cited as a prior art.

2 to 9 show an embodiment of the fuse element according to the present invention, and FIG. 2 is a perspective view of a thin metal having a narrow portion of the fuse element of FIG. 1 before being sandwiched between the thick metal and tin-plated. A thin plate metal 1 having a plurality of punched holes 3 in the middle portion of the thick plate metal 2 and having the same shape (excluding thickness) as the thick plate metal in the shape of the portion excluding the narrow portion from the holes 3 is added to another thickness. The shape shown in FIG. 3 is obtained by sandwiching the sheet metal 2 and joining by a joining means such as thermocompression bonding.

In FIG. 3, by leaving the connecting portion 6 of the thick plate metal serving as the left and right electrodes 7 of the fuse and cutting off the unnecessary portion, the thick plate metal remaining in the intermediate portion as shown in FIG. 4 plays the role of a heat dissipation plate. The narrow thin plate metal exposed from the punched hole portion 3 of the thick plate metal serves as a narrow portion 4 of the fuse element and terminals 7 at both ends of the thick plate metal for screwing the fuse.

Next, the member of FIG. 4 is assembled so that the electrode connecting portion 6 enters the electrode connecting portion fixing groove 12 of the fuse container 8 shown in FIG. 5, and then the thick plate metal connecting portion 6 is cut to cut the fuse container. After filling the container with an arc-extinguishing agent through the end face hole 10 of the fuse container, the fuses shown in FIG. 1 are obtained by press-fitting the bases 9 from the left and right sides of the fuse container. If only the fuse element is shown, the shape shown in FIG. 6 is obtained.

The narrow portion 4 of the fuse element made of the narrow thin plate metal 1 sandwiched between the thick plate metal 2 is required to have a greater degree of freedom than processing the cross-sectional area and shape of the fuse element with the same member as the conventional thick electrode terminal. Fusing time-It is possible to obtain ^{a fusing I 2} t to achieve current characteristics and interruption of abnormal overcurrent.

On the other hand, the wide portion 5 responsible for heat dissipation does not require a process of assembling electrodes having different plate thicknesses like a fuse element formed by punching from a single plate metal like a conventional fuse, and generates heat as an electrode. It is easily integrated by joining a pair of thick plate metal 2 with a plate thickness tin-plated at about 250 ° C. by a joining means such as thermocompression bonding, which has sufficient current-carrying capacity and can secure a large heat dissipation as a wide portion 5. It can be manufactured without the need for the process of assembling the electrode and the fuse element, and the process can be simplified.

Next, an application example of a high-voltage fuse having a rated current of 150 A using the fuse element according to the present invention will be described.
The current endurance condition of the high-voltage fuse used for EV or HEV is as a model waveform of the current, transient in JASO D 622-3: 2016 "Automotive parts-High-voltage fuse Part 3: Screw-tightened high-voltage fuse". Current intermittent endurance test (starts energization at 200% of rated current, decays from 125% to 135% of rated current in 0.25 seconds, energizes 50% of rated current for 1 to 10 seconds, and then pauses for 50 seconds Cycle) is specified, and the first part of the high voltage fuse: Definition and general test requirements The JASO D622-1 standard requires that this cycle be energized at least 50,000 times.
This model waveform is displayed as an instantaneous current value (% of rated current) as a function of elapsed time, not as an effective value. Using this model waveform as a function of the elapsed time, the square root of the average of the squares of the instantaneous currents up to the elapsed time T is calculated to be approximately the value of the broken line in FIG.

When the fuse element is made of copper material, in order to satisfy the above requirements, it is necessary to have a fusing time-current characteristic (one-dot chain line in FIG. 12) with a safety factor of twice or more the model waveform based on the actual durability test results. The design target is the fusing time-current characteristic shown by the solid line in FIG. 12 in order to achieve current interruption as soon as possible against the accident current.

^{In order to obtain 1,200 A (fuse I 2} t = 14,400 A ² s) in 10 ms in the fusing time-current characteristics of the solid line in Fig. 12 of the design target, the narrow part is composed of a parallel structure of three narrow thin metal plates. In this case, the fuse is sandwiched between a pair of thick metal plates with a thickness of 0.74 mm and tin-plated using a plate thickness of 0.2 mm and a plate width of 0.54 mm (according to the JASO D 622-3 standard, a fuse with a rated current of 150 A). Since the terminal thickness of the electrode is specified as 1.5 mm), it is possible to secure the ^{design target fusing I 2} t without forcibly deforming or processing for forming a narrow part as in the conventional technology. It becomes.

The fuse element is made of a plate material having the same thickness as the electrode by the conventional technology, and the above-mentioned work hardening problem caused by crushing and machining is ^{closed, and the above-mentioned fusing I 2} t = 14,400 A ² s is restricted by press working ( When trying to obtain the same plate width of 0.54 mm as in the above embodiment while keeping the plate thickness from the end of the hole to the end of the hole or the outer shape), the terminal thickness of the electrode is about 1/7 of the terminal thickness of 1.5 mm. It is necessary to crush the crushed portion to 0.2 mm (L2 in the case of FIG. 14) and punch out the crushed portion to form a narrow portion, which may cause a problem in durability against violent vibration generated in an automobile.

According to the fuse element of the present invention, it is possible to change the required rated current and fusing time-current characteristics simply by changing the number of parallel lines and the thickness of the narrow thin plate metal 1, and the fuse element is formed by press working as in the conventional technique. It is not necessary to invest in a large number of punching dies for drilling circular or diamond-shaped holes according to the fusing time-current characteristics, and a fuse element with the required characteristics can be obtained at low cost.

Further, according to the fuse element of the present invention, a high-voltage fuse filled with an arc-extinguishing agent is difficult to blow. At a small accident current of about twice the rated current, tin near a narrow portion where a pair of thick plate metals 2 are joined. The plating flows into the narrow portion 4 due to the heat generated by the narrow portion 4, and reliable fusing can be achieved by the diffusion action thereof.

Further, the narrow thin plate metal 1 may have a composition different from that of the thick plate metal, and by treating the plating having excellent corrosion resistance, it has excellent environmental resistance and large heat dissipation due to the wide portion 5 having a larger heat dissipation and heat capacity than the narrow portion. By action, heat is dissipated so that the temperature of the narrow portion 4 becomes lower than the recrystallization temperature of the narrow thin plate metal 1, and the fusing current is raised in a long region where the fusing time exceeds 10 seconds (fusing time-current characteristics become almost horizontal). ), And long-term reliability for continuous energization can be ensured.

FIG. 10 shows the configuration of a fuse element in which the thin plate metal 1 having a narrow portion is replaced with the linear metal 11 in another embodiment of the present invention. In this embodiment, the thick plate metal 2 is replaced with the linear metal 11. In some cases, a concave groove is formed so that the thick plate metal 2 can be brought into close contact with the facing surface.

Further, as another embodiment of the present invention, as shown in FIG. 11, the punched hole 3, the exposed narrow thin plate metal 1 or the linear metal 11 is used to form an S shape, or the exposed portion of the linear metal 11 is formed into a spiral shape. By setting this, the time that occurs intermittently in the normal operating state is short, and the stress due to thermal expansion of the fuse element due to a large overcurrent that cannot exert the heat dissipation effect in the wide portion 5 can be alleviated, and excellent durability performance. Can be obtained.

The number of narrow thin plate metal 1 or linear metal 11 in parallel is not limited to the three shown in the figure, and the number of punched holes 3 formed in the thick plate metal 2 also changes depending on the rated voltage at three locations. It is not limited to.

1 Thin plate metal with narrow part 2 Thick plate metal 3 Punched hole made in thick plate metal 4 Narrow part made of thin plate metal narrow part 5 Wide part made of thick plate metal 6 Electrode connection part before disconnection 7 Fuse electrode 8 Fuse Container 9 Base 10 Arc-extinguishing agent filling hole 11 Linear metal 12 Electrode connection fixing groove

Claims (5)

A thin sheet metal having a narrow portion is sandwiched between a pair of thick plate metals having a plurality of punched holes in the middle portion and tin-plated, and joined by a joining means such as thermocompression bonding to expose the narrow thin plate from the punched holes. The metal part forms a narrow part of the fuse element, the remaining part of the punched hole of the thick plate metal forms a wide part that plays the role of a heat dissipation plate, and both ends thereof form a terminal part integrated type. Fuse element. The fuse element according to claim 1, wherein the narrow portion of the thin metal plate has a shape in which one row or a plurality of narrow portions are connected in parallel. The fuse element according to claim 2, wherein the fuse element is exposed from a hole in a thick plate metal and the plane shape of the narrow portion is S-shaped. The fuse element according to claim 1, wherein the thin plate metal having a narrow portion is replaced with a linear metal. The fuse element according to claim 4, wherein the linear metal in the narrow portion forms a spiral shape.

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