Patent Application
20230187107
The present invention relates to a shunt resistor.
A shunt resistor is used for sensing current flowing through a semiconductor power module or the like mounted on an electric vehicle, for example.
Patent Literature 1 describes a shunt resistor which is easy to attach, does not require an excessively large attachment space, and is capable of performing highly accurate current sensing.
The shunt resistor described in Patent Literature 1 includes: a first terminal and a second terminal each made of an electrically conductive metal material and having a first plane, a second plane, and an outer peripheral surface around the planes; and resistive elements connected to the respective first planes and connecting the first terminal and the second terminal together, the respective first planes of the first terminal and the second terminal opposing each other. The joint area between the resistive elements and the first planes is smaller than the area of the first planes. The first terminal and the second terminal each have a hole portion penetrating through from the first plane to the second plane.
Such a shunt resistor may be referred to as a “bushing shunt (resistor).”
In the shunt resistor disclosed in the above Patent Literature 1, a plurality of cylindrical resistive elements are arranged between the first terminal and the second terminal, and the opposite end faces of the resistive elements have a surface connection with the first terminal and the second terminal through welding, for example. Thus, there is a demand for enhancing the strength of the shunt resistor and reducing the electrical resistance.
An object of the present invention is to enhance the strength of a shunt resistor. In addition, an object of the present invention is to reduce the electrical resistance between the resistive elements and the terminals in the shunt resistor.
According to an aspect of the present invention, there is provided a shunt resistor including: a first terminal and a second terminal each made of an electrically conductive metal material; and a resistive element disposed between the first terminal and the second terminal. The first terminal and the second terminal each have a through-hole. The resistive element is embedded in the through-holes of the first terminal and the second terminal in a depth direction thereof. Regions connecting the resistive element to the first terminal and the second terminal each have an alloy portion formed along an inner peripheral surface of the through-hole.
With the resistive element and the alloy portion formed by laser beam welding or electron beam welding, for example, the strength of the shunt resistor can be enhanced.
Preferably, the resistive element includes a plurality of resistive elements, and the plurality of resistive elements are provided in parallel and connect the first terminal and the second terminal together.
Preferably, the first terminal and the second terminal each have a flange portion formed at a position connected to the resistive element by reducing a diameter of the through-hole toward the position connected to the resistive element.
The flange portion allows securely fixing the first terminal and the second terminal.
At least a portion of the through-hole may be filled with solder, and the resistive element may be connected to a surface of the solder.
Since the resistive element is connected to the surface of the solder between the first terminal and the second terminal, the electrical resistance between the resistive element and the terminals in the shunt resistor can be reduced.
According to the present invention, the electrical resistance between the resistive elements and the terminals in the shunt resistor can be reduced. In addition, it is possible to suppress partial imbalance of the current density and the heat transfer effect of the shunt resistor and reduce manufacturing variations of a resistance value. The present invention also produces the effect of suppressing local heating at a large current.
Furthermore, the strength of the shunt resistor can be enhanced.
Hereinafter, a shunt resistor in accordance with embodiments of the present invention will be described in detail with reference to the drawings.
A shunt resistor A according to the present embodiment includes: a first terminal (electrode) 1 made of an electrically conductive metal material, such as Cu, and having a first plane 11a, a second plane 11b on the back surface side thereof, and an outer peripheral surface (side surface) 11c around the planes; and a second terminal (electrode) 3 made of an electrically conductive metal material, such as Cu, and having a first plane 13a, a second plane 13b, and an outer peripheral surface (side surface) 13c around the planes.
Further, the first terminal 1 and the second terminal 3 respectively have hole portions 1a, 3a penetrating through from the first planes 11a, 13a to the second planes 11b, 13b.
The respective first planes 11a, 13a of the first terminal 1 and the second terminal 3 oppose each other, and a plurality of resistive elements 5 that connect the first terminal 1 and the second terminal 3 are provided in parallel on the respective first planes 11a, 13a. As the material of the resistive elements 5, Cu—Ni based, Cu—Mn based, and Ni—Cr based metal materials, for example, manganin, can be used.
The area of the end portions 5a, 5b of the resistive elements 5 with respect to the first plane 11a and 13a is smaller than the area of the first planes 11a, 13a. In the present example, the plurality of resistive elements 5 are arranged concentrically about the hole portions (center holes) 1a, 3a respectively formed in the first terminal 1 and the second terminal 3 at four corners. The number of resistive elements 5 and the arrangement thereof are not limited thereto, and may, be changed appropriately.
It should be noted that the first terminal 1 and the second terminal 3 may be polygonal, such as triangular, as well as rectangular, and may be circular. The hole portions 1a, 3a may be polygonal, such as rectangular, as well as circular.
As illustrated in
The counterbores 1b, 3b may each have a diameter that is reduced in the depth direction at positions (in the depth direction) connected to the end portions 5a, 5b of the resistive element 5 on the sides of the first planes 11a, 13a of the first terminal 1 and the second terminal 3. This configuration can form flange portions 1x, 3x on the sides of the first planes 11a, 13a of the first terminal 1 and the second terminal 3. In this case as well, on the respective contact surfaces between the terminals and the resistive element, the flange portions 1x, 3x may, preferably be formed in the regions substantially equal to the end portions of the resistive element 5, that is, in regions that narrow by the area corresponding to the counterbores.
Regions connecting the end portions 5a, 5b of the resistive element 5 to opening edge portions 1c, 3c of the counterbores 1b, 3b of the first terminal 1 and the second terminal 3 respectively have ring-shaped alloy portions 21a, 21b formed along the outer peripheries of the first terminal 1 and the second terminal 3 by alloying an electrode (terminal) material and a resistive material through laser beam welding or electron beam (EB) welding, for example.
As described above, according to the present embodiment, the laser welding allows ensuring structural strength of the shunt resistor A. In addition, soldering allows ensuring electrical characteristics. Through such composite structure formation, a shunt resistor with stable performance can be manufactured.
According to the present embodiment, it is possible to reduce the electrical resistance, and also suppress partial imbalance of the current density and the heat transfer effect and reduce manufacturing variations of a resistance value by leveling the current density. In addition, the heat transfer effect (ensuring a heat transfer area) produces the effect of suppressing local heating at a large current.
Next, a second embodiment of the present invention will be described.
According to the present embodiment, the flange portions 1x, 3x allow the solder material filled portions 7a, 7b connected to the resistive element 5 to be securely fixed in the first terminal 1 and the second terminal 3.
The counterbores 1b, 3b of the first terminal 1 and the second terminal 3 are each filled with solder material, and thus have the solder material filled portions 7a, 7b respectively formed therein. The flange portions 1x, 3x allow the solder material filled portions 7a, 7b connected to the resistive element 5 to be securely fixed in the first terminal 1 and the second terminal 3.
As illustrated in
As illustrated in
Next, laser irradiation AR1 is performed on the boundary between the end portions 5a, 5b of the resistive element 5 and the opening edge portions 1c, 3c of the counterbores 1b, 3b of the first terminal 1 and the second terminal 3. More specifically, the end portions 5a, 5b of the resistive element 5 are joined to the opening edge portions 1c, 3c of the counterbores 1b, 3b of the first terminal 1 and the second terminal 3 by performing laser welding in a circular manner along the opening edge portions 1c, 3c. Then, the laser-welded parts become the alloy portions 21a, 21b including an alloy, thereby connecting the first terminal 1 and the second terminal 3 to the resistive element 5. The laser welding allows ensuring structural strength. It should be noted that the outer peripheral part is ring-shaped due to a trace of laser.
As illustrated in
With the solder material filled portions 7a, 7b connected to the end portions 5a, 5b of the resistive element 5, the electrical resistance between the resistive element 5 and the terminals 1, 3 can be reduced.
As described above, the laser welding allows ensuring structural strength of the shunt resistor A. In addition, soldering allows ensuring electrical characteristics. Through such composite structure formation, a shunt resistor with stable performance can be manufactured.
It should be noted that in the manufacturing steps of
It should be noted that
In the foregoing embodiments, the configurations and the like illustrated in the drawings are not limiting, and may be modified, as appropriate, as long as the effects of the present invention can be obtained. Other modifications may be made and implemented, as appropriate, without departing from the scope of the purpose of the present invention. The constituent elements of the present invention may be selectively employed or not employed, and an invention provided with a selected configuration is also included in the present invention.
The present invention is applicable to shunt resistors.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-084745 | May 2020 | JP | national |
The application is a 371 application of PCT/JP2021/017351 having an international filing date of May 6, 2021, which claims priority to JP 2020-084745 filed May 13, 2020, the entire content of each of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/017351 | 5/6/2021 | WO |
