JP7696256B2 - Shunt Resistor - Google Patents

Description

The present invention relates to a shunt resistor.

Patent document 1 shows a resistor that includes a resistive body and a first terminal and a second terminal provided at both ends of the resistive body.

The resistor material that forms the resistor of this resistor is generally a copper-based alloy. The electrodes of the resistor are also made of copper.

JP 2016-086129 A

In shunt resistors like the one above, copper alloys are used as the resistor material. This makes the shunt resistors heavy.

The objective of the present invention is to provide a shunt resistor that can be made lighter.

According to one aspect of the present invention, a shunt resistor includes a plate-shaped resistor made mainly of aluminum and electrodes bonded to the resistor , the resistor includes an alloy of aluminum and magnesium, and has a magnesium content of 0.7% by mass or more and 5.0% by mass or less, and the electrodes are made mainly of aluminum and are different from the resistor.

According to this embodiment, the main component of the plate-shaped resistor is aluminum, which has a smaller mass per volume than copper.

As a result, the shunt resistor of this embodiment can be made lighter than shunt resistors that use copper as the resistive material.

FIG. 1 is a perspective view showing a shunt resistor according to one embodiment. FIG. 2 is a front view showing a state in which a shunt resistor according to an embodiment is connected to a bus bar. FIG. 3A is a plan view showing a state in which plating portions are formed on each electrode of a shunt resistor according to one embodiment. FIG. 3B is a front view showing a state in which plating portions are formed on each electrode of a shunt resistor according to one embodiment. FIG. 4A is a plan view showing a shunt resistor according to a modified example. FIG. 4B is a front view showing a shunt resistor according to a modified example. FIG. 5 is an explanatory diagram illustrating a comparison between a shunt resistor according to an embodiment and a shunt resistor according to a comparative example.

In recent years, exhaust gas regulations have been strengthened in many countries in order to address environmental issues, and the development of electric vehicles (EVs) is progressing.

In electric vehicles, weight reduction is required to increase the distance they can travel on a single charge, and the materials that make up electric vehicle parts are being replaced with aluminum. Parts used in electric vehicles include battery electrodes and electric wires, and there are studies underway to replace the material of battery electrodes and electric wires with aluminum.

Electric vehicles also use shunt resistors, which are resistors used to detect current. The charge and discharge current of an electric vehicle's battery can exceed 400A, and large currents flow through the shunt resistors used in electric vehicles. As the detection current increases, the shunt resistors become larger, and the increased weight of larger shunt resistors is becoming a problem.

The resistive material generally used in shunt resistors is made of a copper-based alloy, and copper electrodes are often used as well. This copper-based resistive material is one of the factors that increases the weight of shunt resistors.

As a result, the inventor came up with the following embodiment.

(Embodiment)
Hereinafter, an embodiment of the present invention will be described. In this embodiment, a shunt resistor used for detecting the charge/discharge current of a battery of an electric vehicle will be described as an example, but the present invention is not limited to this. The shunt resistor according to this embodiment can be used as a shunt resistor for general current detection.

[Shunt resistor]
Fig. 1 is a perspective view showing a shunt resistor 10 according to one embodiment. Fig. 2 is a front view showing the shunt resistor 10 according to one embodiment connected to bus bars 40, 44. For convenience of explanation, Figs. 1 and 2 show the shunt resistor 10 with plating portions 30, 32 (see Figs. 3A and 3B) described below removed.

(Resistor)
1, the shunt resistor 10 includes a plate-shaped resistor 14 made mainly of aluminum (Al). By making the resistor 14 mainly made of aluminum, the shunt resistor 10 including the resistor 14 can be made lighter.

In order to set the resistance value of the shunt resistor 10, the resistor 14 must have a higher resistivity than the electrodes 16, 18. The resistor 14 must also exhibit a stable resistance value and have a certain level of heat resistance and corrosion resistance.

The aluminum used as the main component of the resistor material forming resistor 14 to reduce weight generally does not easily form solid solutions with other elements. For this reason, if the resistor material is made of an aluminum alloy to which additives have been added, the additive elements will form compounds and precipitate in the aluminum alloy. In this case, it is not possible to increase the resistance value of the resistor material made of an aluminum alloy.

Therefore, we will select a resistor material that is suitable for resistor 14, with aluminum as the main component.

(First resistor)
The first selected resistor 14 contains an alloy of aluminum (Al) and magnesium (Mg) (Al-Mg alloy). The content of magnesium in this resistor 14 is set to be 0.7 mass % or more and 5.0 mass % or less with respect to the total mass of the resistor 14.

The resistor 14 is formed using a resistor material whose main component is aluminum, which is difficult to dissolve in other elements. This resistor material is an alloy in which magnesium is dissolved in aluminum, and increases the amount of magnesium dissolved in the alloy while suppressing the precipitation of magnesium as a compound. This increases the adjustable range of resistivity and increases the resistivity.

In addition, by forming the resistor 14 from an alloy of aluminum and magnesium, which has good workability and excellent weldability, the ease of manufacturing the shunt resistor 10 is increased. Furthermore, by forming the resistor 14 from an alloy of aluminum and magnesium, which has good corrosion resistance, the corrosion resistance of the resistor 14 is increased.

The magnesium content in resistor 14 is set to 0.7% by mass or more and 5.0% by mass or less, thereby increasing the resistivity while suppressing the temperature coefficient of resistance of resistor 14.

Specifically, the resistivity is increased by setting the magnesium content in resistor 14 to 0.7 mass% or more. In addition, the magnesium content in resistor 14 to 5.0 mass% or less suppresses the precipitation of magnesium as a compound, and suppresses the decrease in resistivity that occurs after the precipitation of the compound.

(Second resistor)
The second selected resistor 14 contains an alloy (Al-Mn-Mg alloy) of aluminum (Al), manganese (Mn), and magnesium (Mg). This resistor 14 has a magnesium content of 0.7% by mass or more and 5.0% by mass or less, and a manganese content of 0.6% by mass or more and 2.0% by mass or less, relative to the total mass of the resistor 14. Furthermore, this resistor 14 has a combined magnesium and manganese content of 1.3% by mass or more and 7.0% by mass or less, relative to the total mass of the resistor 14.

The resistor 14 is formed using a resistor material whose main component is aluminum, which is difficult to dissolve other elements in. This resistor material is an alloy in which manganese and magnesium are dissolved in aluminum, and increases the amount of manganese or magnesium dissolved in the solid solution while suppressing the precipitation of manganese or magnesium as a compound. This makes it possible to increase the resistivity while widening the adjustment range of the resistivity.

In addition, the resistor material of resistor 14 can dissolve manganese without precipitating as a compound, even when the maximum amount of magnesium is added to the aluminum, as long as the magnesium in the aluminum does not precipitate as a compound.

By adding manganese and magnesium to a resistor material whose main component is aluminum, the total amount of additives that can be added in a solid solution state with aluminum is increased compared to when only magnesium is added to a resistor material whose main component is aluminum. This further widens the adjustment range of the resistivity of the resistor formed, and further increases the resistivity.

In addition, by forming the resistor 14 from an alloy of aluminum, manganese, and magnesium, which has good workability and weldability, the ease of manufacturing the shunt resistor 10 is increased. Furthermore, by forming the resistor 14 from an alloy of aluminum, manganese, and magnesium, which has good corrosion resistance, the corrosion resistance of the resistor 14 is increased.

The magnesium content in resistor 14 is set to 0.7% by mass or more and 5.0% by mass or less, the manganese content is set to 0.6% by mass or more and 2.0% by mass or less, and the combined magnesium and manganese content is set to 1.3% by mass or more and 7.0% by mass or less. This increases the resistivity while suppressing the temperature coefficient of resistance of resistor 14.

Specifically, the resistivity is increased by setting the magnesium content in resistor 14 to 0.7 mass% or more. In addition, the magnesium content in resistor 14 to 5.0 mass% or less suppresses the precipitation of magnesium as a compound, and suppresses the decrease in resistivity that occurs after the precipitation of the compound.

In addition, by setting the manganese content in resistor 14 to 0.6 mass% or more, the resistivity is increased. In addition, by setting the manganese content in resistor 14 to 2.0 mass% or less, the precipitation of manganese as a compound is suppressed, and the decrease in resistivity that occurs after the precipitation of the compound is suppressed.

The resistor 14 made of an alloy of aluminum and magnesium, and the resistor 14 made of an alloy of aluminum, manganese, and magnesium are both set so that their temperature coefficient of resistance (TCR) is 2000 ppm/°C or less.

This improves the temperature characteristics of the shunt resistor 10 compared to a resistor made only of aluminum, which has a temperature coefficient of resistance of approximately 4200 ppm/°C.

It is also known that there is a correlation between the temperature coefficient of resistance and the resistivity of resistors 14 made of aluminum alloys. Therefore, by increasing the resistivity of resistor 14 above a predetermined value, the temperature coefficient of resistance can be reduced to 2000 ppm/°C or less.

The temperature coefficient of resistance of resistor 14 may be 3000 ppm/°C or less. Furthermore, the temperature coefficient of resistance of resistor 14 may be 4000 ppm/°C or less.

If the temperature coefficient of resistance of the resistor 14 is set to 1000 ppm/°C or less, the temperature characteristics of the shunt resistor 10 will be further improved and the resistivity will be further increased, but the resistor material used to form the resistor 14 must be carefully selected.

Here, the temperature coefficient of resistance (TCR) is calculated based on the rate of change of resistance value and the amount of temperature change. For example, if an object that exhibits a first resistance value R1 at a first temperature T1 changes to a second resistance value R2 when the temperature is changed to a second temperature T2, the temperature coefficient of resistance TCR [ppm/°C] can be calculated using the following formula:

TCR=[{(R2-R1)/R1}/(T2-T1)]×1000000

(electrode)
The shunt resistor 10 includes electrodes 16, 18 joined to a resistive element 14. Each of the electrodes 16, 18 is formed in a plate shape and made mainly of aluminum (Al).

The term "mainly composed of aluminum" means that, from the viewpoint of reducing the weight of the shunt resistor 10, the aluminum content is 50% by mass or more relative to the total mass of each electrode 16, 18, preferably 80% by mass or more, and more preferably 90% by mass or more.

Examples of conductive materials that contain aluminum as a main component include pure aluminum with a purity of 99% or more, or aluminum alloys.

When different types of metals are joined, a local battery is formed at the joint due to the difference in the standard electrode potential between the metals, and galvanic corrosion may occur at the joint due to the presence of moisture, etc. This galvanic corrosion also occurs when aluminum is used as the metal.

In this embodiment, in order to reduce the weight of the shunt resistor 10, the resistor 14 is formed from a resistor material whose main component is aluminum, a light metal.

When the electrodes 16, 18 are made of a conductive material mainly composed of aluminum, and the resistor 14 is made of a resistor material that has a large potential difference from the standard electrode potential of aluminum, galvanic corrosion due to dissimilar metal contact may occur at the joints between the resistor 14 and the electrodes 16, 18. Examples of resistor materials that may cause galvanic corrosion between the electrodes 16, 18, mainly composed of aluminum, include copper, chromium, and iron.

Therefore, in the shunt resistor 10 according to this embodiment, the electrodes 16, 18 are formed from a conductive material whose main component is aluminum. By using aluminum for the resistor material and the electrode material, the shunt resistor 10 according to this embodiment can suppress galvanic corrosion at the joints between the resistor 14 and the electrodes 16, 18 while reducing its weight.

The electrodes of the shunt resistor 10 include a first electrode 16 joined to one end of the resistor 14 and a second electrode 18 joined to the other end of the resistor 14.

As shown in Figures 1 and 2, the first electrode 16 is formed with a first hole 16a through which a bolt 42 is inserted when connecting the first electrode 16 to the bus bar 40. The second electrode 18 is also formed with a second hole 18a through which a bolt 46 is inserted when connecting the second electrode 18 to the bus bar 44.

A first joint 20 is formed at the joint between the resistor 14 and the first electrode 16. A second joint 22 is formed at the joint between the resistor 14 and the second electrode 18.

Methods for joining the resistor 14 and each electrode 16, 18 include fusion welding, in which the materials to be joined are melted and joined together, and pressure welding, in which the materials to be welded are joined by the diffusion of metal atoms. Another method for joining the resistor 14 and each electrode 16, 18 includes brazing, in which the materials to be welded are joined with a brazing material.

In this embodiment, the resistor 14 and each electrode 16, 18 are joined by fusion welding or pressure welding without using a brazing material. Examples of fusion welding include laser welding and electron beam welding.

By joining in this manner, in this embodiment, no brazing material is interposed between the resistor 14 and each electrode 16, 18, improving the resistance characteristics of the shunt resistor 10.

The resistor 14 is a rectangular plate. Each of the electrodes 16, 18 is also a rectangular plate. The widths of the resistor 14 and each of the electrodes 16, 18 are set to approximately the same dimensions. As a result, the shunt resistor 10 in which the resistor 14 and each of the electrodes 16, 18 are joined is a rectangle that is long in the arrangement direction NH of each of the electrodes 16, 18 and the resistor 14.

(Plating Department)
The bus bars 40, 44 or harnesses etc. connected to the electrodes 16, 18, each of which is mainly made of aluminum, are assumed to be made of copper (Cu) based materials.

The standard electrode potential of aluminum is -1.68 V, and the standard electrode potential of copper is +0.34 V. Therefore, the electrodes 16, 18, which are primarily made of aluminum, and the bus bars 40, 44, etc., which are made of copper-based materials, form local batteries at the contact points, and corrosion can occur if moisture or the like is present at the contact points. For this reason, it is considered to provide a moisture-proof and waterproof structure to prevent moisture or the like from penetrating into the contact points between the electrodes 16, 18 and the bus bars 40, 44, etc.

A commonly known moisture-proof and waterproof structure is one in which the contact areas between each electrode 16, 18 and each bus bar 40, 44, etc. are covered with a plastic cover.

However, there is a risk of moisture seeping in from the contact interface between the metal and plastic of each bus bar 40, 44, etc. Also, because plastic melts easily at high temperatures, there is a concern that deformation at high temperatures may occur if the contact parts are covered with a plastic cover.

In addition, after connecting each bus bar 40, 44, etc. to each electrode 16, 18, the user must cover the contact points between each electrode 16, 18 and each bus bar 40, 44, etc. with a plastic cover, which may make the device less user-friendly.

Therefore, in this embodiment, each electrode 16, 18 has a plating containing nickel (Ni) or zinc (Zn).

The standard electrode potential of nickel is -0.26 V, which is smaller than the standard electrode potential of copper, which has a standard electrode potential of +0.34 V, and therefore galvanic corrosion is less likely to occur.

In addition, the standard electrode potential of zinc is -0.76 V, which is smaller than the standard electrode potential of copper, which has a standard electrode potential of +0.34 V, and so galvanic corrosion is less likely to occur.

Figure 3A is a plan view showing the state where plating portions 30, 32 are formed on each electrode 16, 18 of a shunt resistor 10 according to one embodiment. Figure 3B is a front view showing the state where plating portions 30, 32 are formed on each electrode 16, 18 of a shunt resistor 10 according to one embodiment.

As shown in Figures 3A and 3B, the first electrode 16 has an area including the outer periphery of the first hole 16a covered with a first plating portion 30. The second electrode 18 has an area including the outer periphery of the second hole 18a covered with a second plating portion 32. Each plating portion 30, 32 is formed with a plating containing nickel (Ni) or zinc (Zn).

The first plating portion 30 covers the surface 16b, back surface 16c, both side surfaces 16d, 16e, one end surface 16f, and the inner surface of the first hole 16a of the first electrode 16. The second plating portion 32 covers the surface 18b, back surface 18c, both side surfaces 18d, 18e, the other end surface 18f, and the inner surface of the second hole 18a of the second electrode 18.

As a result, as shown in FIG. 2, when the bus bars 40, 44 are stacked and connected to the electrodes 16, 18 of the shunt resistor 10, direct contact between the electrodes 16, 18 and the bus bars 40, 44 is suppressed. In addition, direct contact between the electrodes 16, 18 and the bolts 42, 46 that pass through the holes 16a, 18a of the electrodes 16, 18 to fix the electrodes 16, 18 to the bus bars 40, 44 is suppressed.

In this embodiment, as shown in Figures 3A and 3B, a shunt resistor 10 is shown in which a portion of the first electrode 16 is covered with a first plating portion 30 and a portion of the second electrode 18 is covered with a second plating portion 32, but the present invention is not limited to this.

For example, the shunt resistor 10 may be configured as shown in the following modified example.

(Modification)
A modification of this embodiment will now be described.

Figure 4A is a plan view showing a shunt resistor according to a modified example. Figure 4B is a plan view showing a shunt resistor according to a modified example. This shunt resistor 50 is a modified example of the shunt resistor 10 described above, and is different from the shunt resistor 10 described above in that the range of each plating portion 30, 33 formed on each electrode 16, 18 is different.

As shown in Figures 4A and 4B, the first plating portion 30 formed on the first electrode 16 reaches the first joint portion 20, which is the joint portion between the first electrode 16 and the resistor 14, and the entire surface of the first electrode 16 is covered with the first plating portion 30. The second plating portion 32 formed on the second electrode 18 reaches the second joint portion 22, which is the joint portion between the second electrode 18 and the resistor 14, and the entire surface of the second electrode 18 is covered with the second plating portion 32.

As a result, as shown in FIG. 2, when the bus bars 40, 44 are stacked and connected to the electrodes 16, 18 of the shunt resistor 50, direct contact between the electrodes 16, 18 and the bus bars 40, 44 is suppressed. In addition, direct contact between the bolts 42, 46 inserted into the holes 16a, 18a of the electrodes 16, 18 and the electrodes 16, 18 is suppressed.

In addition, in the shunt resistor 50 according to this modified example, the entire surfaces of the electrodes 16, 18 are covered with the plating portions 30, 32. This prevents corrosion of the electrodes 16, 18 over their entire surfaces.

(Action and Effects)
Next, the effects of the first embodiment will be described.

The shunt resistors 10 and 50 of this embodiment include a plate-shaped resistor 14 whose main component is aluminum, and electrodes 16 and 18 joined to the resistor 14.

In this configuration, the main component of resistor 14 is aluminum, which has a smaller mass per volume than copper.

This makes it possible to reduce the weight of shunt resistors 10 and 50 compared to shunt resistors that use copper as the resistive material.

In addition, in the shunt resistors 10 and 50 of this embodiment, each electrode 16 and 18 is a plate made primarily of aluminum.

In this configuration, the main component of each electrode 16, 18 is also aluminum, which has a smaller mass per volume than copper.

This makes it possible to further reduce the weight of the shunt resistors 10 and 50 compared to shunt resistors in which copper is used for each electrode 16 and 18.

Here we will explain the weight reduction in detail.

Figure 5 is an explanatory diagram showing a comparison between the shunt resistors 10 and 50 according to one embodiment and the shunt resistor 100 according to a comparative example.

Figure 5 shows a comparative example shunt resistor 100 having a resistive body 114 and electrodes 116, 118 made primarily of copper, and shunt resistors 10, 50 according to the present embodiment having a resistive body 14 and electrodes 16, 18 made primarily of aluminum.

The shunt resistor 100 according to the comparative example has a length L of 80.0 mm, a width W of 80.0 mm, and a thickness T of 2.0 mm, and weighs approximately 25.6 g.

While maintaining the dimensions of the shunt resistor 100 according to this comparative example, the shunt resistors 10 and 50 according to this embodiment are formed using a resistor 14 whose main component is aluminum and electrodes 16 and 18 whose main component is aluminum.

In this case, since the specific gravity of aluminum is 2.7 g/cm ³ , the weight of the shunt resistors 10 and 50 formed is approximately 7.8 g, which is approximately 70% lighter than the shunt resistor 100 of the comparative example.

Aluminum has a higher resistivity than copper. For this reason, in order to pass the same current through the aluminum-based shunt resistors 10 and 50 as through the copper-based shunt resistor 100, the cross-sectional area of the resistor 14 must be increased. This increases the volume of the resistor 14 of the shunt resistors 10 and 50, and also increases the volume of each of the electrodes 16 and 18.

Specifically, the resistivity of copper is 1.7×10 ⁻⁸ Ω·m, and the resistivity of aluminum is 2.7×10 ⁻⁸ Ω·m, which is about 1.6 times that of copper. Therefore, in order to pass a current equivalent to that of the shunt resistor 100 whose main component is copper through the shunt resistors 10 and 50 whose main component is aluminum, it is necessary to make the thickness T of the shunt resistors 10 and 50 about 1.6 times that of the shunt resistor 10 whose main component is copper.

As a result, the thickness T of the shunt resistors 10 and 50 according to this embodiment, which are primarily made of aluminum, is approximately 3.2 mm, and the weight is approximately 12.5 g. This allows the weight of the shunt resistors 10 and 50 according to this embodiment to be reduced by approximately 51% compared to the shunt resistor 100 according to the comparative example, which weighs approximately 25.6 g.

The unit price of aluminum is generally about 1/3 of the unit price of copper. And the weight of aluminum is about 1/2 of the weight of copper. Taking these factors into consideration, the material cost of the resistor 14 and each electrode 16, 18 can be reduced to about 1/6.

As a result, the shunt resistors 10 and 50 according to this embodiment can reduce material costs compared to the shunt resistor 100 according to the comparative example.

The resistor 14 and electrodes 16, 18 that make up the shunt resistors 10, 50 are primarily made of aluminum. This makes it possible to suppress galvanic corrosion that can occur when the resistor 14 and electrodes 16, 18 are made of different types of metals.

Furthermore, the resistor 14 and the electrodes 16, 18 that form the shunt resistors 10, 50 are plate-shaped. Therefore, the shunt resistors 10, 50 can be formed as a whole in a plate shape.

As a result, the electrodes connected to the end faces of the resistor 14 are formed in a rectangular parallelepiped shape, making it possible to make the entire shunt resistors 10 and 50 thinner than shunt resistors in which part of the electrodes protrude below the resistor 14.

In addition, in the shunt resistors 10 and 50 of this embodiment, the resistor 14 contains an alloy of aluminum and magnesium.

In this configuration, even in resistor materials whose main component is aluminum, which is difficult to dissolve with other elements, the amount of magnesium in solid solution can be increased while suppressing the precipitation of magnesium as a compound. This makes it possible to increase the adjustment range of resistivity and to increase the resistivity, compared to when additives whose amount in solid solution in aluminum is limited are dissolved in solid solution.

In addition, resistor 14 with such a high resistivity can be formed from an aluminum alloy. Because of this, it is possible to form resistor 14 with a certain thickness compared to the case where a resistor must be formed by forming a mixture of aluminum and other elements, due to the structure of forming a resistor using an element whose amount of solid solubility in aluminum is limited.

Increasing the thickness of the resistor 14 makes it possible to increase the current passing through the resistor 14. This allows the shunt resistors 10 and 50 to be used in circuits through which large currents flow, making it possible to detect large currents.

In addition, alloys of aluminum and magnesium have good workability and excellent weldability. This makes it easier to manufacture the shunt resistors 10 and 50. Furthermore, alloys of aluminum and magnesium have good corrosion resistance. This makes it possible to improve the corrosion resistance of the resistor 14.

In addition, in the shunt resistors 10 and 50 of this embodiment, the resistor 14 has a magnesium content of 0.7% by mass or more and 5.0% by mass or less.

In this configuration, by setting the magnesium content in resistor 14 to 0.7% by mass or more and 5.0% by mass or less, the resistivity of resistor 14 can be increased while suppressing the temperature coefficient of resistance.

In addition, in the shunt resistors 10 and 50 of this embodiment, the resistor 14 contains an alloy of aluminum, manganese, and magnesium.

In this configuration, even in resistor materials whose main component is aluminum, which is difficult to dissolve other elements in, it is possible to increase the amount of manganese and magnesium dissolved in solid solution while suppressing the precipitation of manganese or magnesium as a compound.

This allows for a wider range of resistivity adjustment and higher resistivity compared to dissolving additives whose amount of solid solubility in aluminum is limited.

In addition, even if the maximum amount of magnesium is added to a resistor material whose main component is aluminum without causing magnesium to precipitate as a compound, manganese can be dissolved in the material without precipitating as a compound.

This allows the amount of additives added to the resistor material, which is primarily composed of aluminum, to be increased, further increasing the range of adjustment for the resistivity of the resistor 14 that is formed and further increasing the resistivity.

In addition, resistor 14 with such a high resistivity can be formed from an alloy. Therefore, it is possible to form resistor 14 with a certain thickness compared to the case where a resistor must be formed by forming a mixture of aluminum and other elements, because the resistor is formed using an element whose amount of solid solution in aluminum is limited.

Increasing the thickness of the resistor 14 makes it possible to increase the current passing through the resistor 14. This allows the shunt resistors 10 and 50 to be used in circuits through which large currents flow, making it possible to detect large currents.

Also, alloys of aluminum, manganese, and magnesium have good workability and excellent weldability. This makes it easier to manufacture the shunt resistors 10, 50. Furthermore, alloys of aluminum, manganese, and magnesium have good corrosion resistance. This makes it possible to improve the corrosion resistance of the resistor 14.

In the shunt resistors 10 and 50 of this embodiment, the resistor 14 has a magnesium content of 0.7% by mass or more and 5.0% by mass or less, and a manganese content of 0.6% by mass or more and 2.0% by mass or less. The combined magnesium and manganese content of the resistor 14 is 1.3% by mass or more and 7.0% by mass or less.

In this configuration, it is possible to increase the resistivity while suppressing the temperature coefficient of resistance of the resistor 14.

In addition, in the shunt resistors 10 and 50 of this embodiment, the resistor 14 is an aluminum alloy with a temperature coefficient of resistance of 2000 ppm/°C or less.

In this configuration, the temperature characteristics of the shunt resistors 10 and 50 can be improved compared to when the resistor is made of only aluminum, which has a resistance temperature coefficient of approximately 4200 ppm/°C.

It is also known that there is a correlation between the temperature coefficient of resistance and the resistivity of resistors 14 made of aluminum alloys. Therefore, by increasing the resistivity of resistors 14, the temperature coefficient of resistance can be reduced to 2000 ppm/°C or less.

In addition, in the shunt resistors 10 and 50 of this embodiment, each electrode 16 and 18 has a plating containing nickel or zinc.

In this configuration, even if each electrode 16, 18 is connected to each bus bar 40, 44, etc., made of a metal of a different type from that of the electrodes 16, 18, it is possible to suppress galvanic corrosion that may occur at the contact points.

In this embodiment, the shunt resistors 10 and 50 are described as rectangular plate-shaped, but the shunt resistors 10 and 50 are not limited to this shape.

For example, the shunt resistors 10 and 50 may have a shape in which the electrodes 16 and 18 are provided on the underside of the resistor 14, or in which the L-shaped electrodes 16 and 18 are provided on the end faces of the resistor 14. The shunt resistors 10 and 50 may also have a shape in which the electrodes 16 and 18 provided on the end faces of the resistor 14 protrude downward beyond the resistor 14.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Next, the composition of the resistor material that forms the resistor 14 of the shunt resistors 10 and 50 according to each embodiment will be described.

The resistor 14 must have a higher resistivity than the electrodes 16, 18 in order to set the resistance of the shunt resistors 10, 50. The resistor 14 must also exhibit a stable resistance value and have a certain level of heat resistance and corrosion resistance.

The aluminum used as the main component of the resistor material forming resistor 14 to reduce weight generally does not easily form solid solutions with other elements. For this reason, if the resistor material is made of an aluminum alloy to which additives have been added, the additive elements will form compounds and precipitate in the aluminum alloy. In this case, it is not possible to increase the resistance value of the resistor material made of an aluminum alloy.

Therefore, in order to select a resistor material that is suitable for the resistor 14 of the shunt resistors 10 and 50, multiple alloys of each composition were prepared, with aluminum as the main component and the following elements added in predetermined amounts. The resistivity (ρ) and temperature coefficient of resistance (TCR) were then measured for each alloy composition.

The elements added to aluminum are manganese (Mn), magnesium (Mg), chromium (Cr), copper (Cu), and silicon (Si), and aluminum contains other components as impurities.

Alloys of aluminum (Al) and magnesium (Mg) (Al-Mg alloys) are known to have good workability, excellent weldability, and good corrosion resistance. For this reason, Al-Mg alloys are promising as resistor materials. It is known that magnesium can dissolve in aluminum in large amounts, and Al-Mg alloys are expected to have improved resistivity.

Also, alloys of aluminum (Al) and manganese (Mn) (Al-Mn alloys) are known to have excellent corrosion resistance and good weldability, so these Al-Mn alloys are promising as resistor materials.

Manganese is also known to increase the amount of solid solution in aluminum. For this reason, using manganese as an additive to aluminum is expected to improve resistivity.

Manganese is also an additive that is often added together with magnesium. By dissolving manganese and magnesium in aluminum, an Al-Mn-Mg alloy can be formed.

Table 1 shows the alloy composition of the resistor material and the measurement results of the resistivity (ρ) and temperature coefficient of resistance (TCR) of the resistor material made of alloys of each composition.

In Table 1, resistance materials made of alloys of various compositions are ranked, and each rank of resistor material is determined based on the resistivity (ρ) and temperature coefficient of resistance (TCR) of the resistor material.

To be more specific, the higher the resistivity (ρ), the more suitable the material is for use as a resistor material and the higher its rank. Also, the smaller the temperature coefficient of resistance (TCR), the more suitable the material is for use as a resistor material and the higher its rank.

The ranks listed in the rank column indicate suitability as resistor materials in the order of "C", "B", "A", and "S".

From Table 1, alloys having a composition corresponding to the "S" rank are most suitable as resistor materials, and it is desirable to use alloys having a composition corresponding to the "A" rank or higher as resistor materials.
It is also preferable to use an alloy having a composition that corresponds to rank "B" or higher as the resistor material, and it is also possible to use an alloy having a composition that corresponds to rank "C" or higher as the resistor material.

Table 1 also shows that an Al-Mn-Mg alloy containing aluminum, manganese, and magnesium, or an Al-Mg alloy containing aluminum and magnesium, is suitable as a resistor material. In particular, an Al-Mn-Mg alloy containing aluminum, manganese, and magnesium is suitable as a resistor material.

Next, we will explain the composition of the alloy that makes up each resistor material.

(Alloy containing aluminum and magnesium)
In the Al-Mg alloys containing aluminum and magnesium, the Al-1Mg alloy has a resistivity (ρ) of 3.4×10 ^-8 Ω·m and a temperature coefficient of resistance (TCR) of 3155 ppm/°C. The Al-2.6Mg alloy has a resistivity (ρ) of 5.0×10 ^-8 Ω·m and a temperature coefficient of resistance (TCR) of 2206 ppm/°C. The Al-4.4Mg alloy has a resistivity (ρ) of 6.0×10 ^-8 Ω·m and a temperature coefficient of resistance (TCR) of 1809 ppm/°C.

When the magnesium content exceeds 5.0 mass% relative to the total mass of the resistor material, grain boundary precipitation of magnesium compounds increases. Therefore, in resistor materials with a magnesium content of more than 5.0 mass%, the tendency for the resistance temperature coefficient to decrease becomes smaller, and the amount of change in resistance value increases during storage tests in an environment of 175°C.

Specifically, the Al-1.3Mn-5.0Mg-0.3Cr alloy has a resistivity (ρ) of 6.9×10 ⁻⁸ Ω·m and a temperature coefficient of resistance (TCR) of 1760 ppm/° C. Thus, it can be seen that as the amount of magnesium added approaches 5.0 mass %, the amount of decrease in the temperature coefficient of resistance (TCR) becomes smaller.

Therefore, in order to achieve a temperature coefficient of resistance of 2500 ppm/°C or less, it is preferable to add magnesium in an amount between 0.7% and 5.0% by mass relative to the total mass of the resistor material.

(Alloy containing aluminum, manganese and magnesium)
In the Al-Mn-Mg alloy containing aluminum, manganese, and magnesium, the Al-1Mn-0.3Mg alloy has a resistivity (ρ) of 3.9×10 ^-8 Ω·m and a temperature coefficient of resistance (TCR) of 2878 ppm/°C. The Al-1Mn-1Mg alloy has a resistivity (ρ) of 4.4×10 ^-8 Ω·m and a temperature coefficient of resistance (TCR) of 2406 ppm/°C.

The Al-1.8Mn-1Mg alloy has a resistivity (ρ) of 8.4×10 ⁻⁸ Ω·m and a temperature coefficient of resistance (TCR) of 938 ppm/° C. The Al-2Mn-1Mg alloy has a resistivity (ρ) of 9.5×10 ⁻⁸ Ω·m and a temperature coefficient of resistance (TCR) of 824 ppm/° C.

In the case of an alloy containing aluminum, manganese, and magnesium, a rank A or higher is an indicator of a good product, and the magnesium content is set to 0.7% by mass to 5.0% by mass, and the manganese content is set to 0.6% by mass to 2.0% by mass, relative to the total mass of the resistor material. In addition, in an alloy containing aluminum, manganese, and magnesium, good resistance characteristics can be obtained by setting the combined magnesium and manganese content to 1.3% by mass to 7.0% by mass.

In particular, in the case of an Al-Mn-Mg alloy, the resistance characteristics are good when the manganese content is between 1.8% and 2.0% by mass, and the magnesium content is 1.0% by mass, relative to the total mass of the resistor material. This is worthy of an S rank.

In the case of Al-Mn-Mg alloys, simply setting the manganese content within the normal solid solution range does not significantly improve the resistance characteristics. However, it can be said that the resistance characteristics can be improved by setting the combined magnesium and manganese content to 1.3% by mass or more and 7.0% by mass or less, based on the minimum and maximum values of manganese and magnesium for A rank to S rank.

10, 50 Shunt resistor 14 Resistor 16 First electrode 18 Second electrode 30 First plating portion 32 Second plating portion TCR Temperature coefficient of resistance

Claims (6)

A plate-shaped resistor whose main component is aluminum,
an electrode joined to the resistor ;
the resistor comprises an alloy of aluminum and magnesium;
The magnesium content is 0.7% by mass or more and 5.0% by mass or less,
The electrodes are mainly made of aluminum and are different from the resistor.
Shunt resistor. 2. The shunt resistor of claim 1 ,
The resistor comprises an alloy of aluminum, manganese and magnesium.
Shunt resistor. 3. The shunt resistor according to claim 2 ,
The resistor has a manganese content of 0.6% by mass or more and 2.0% by mass or less, and a combined magnesium and manganese content of 1.3% by mass or more and 7.0% by mass or less.
Shunt resistor. The shunt resistor according to any one of claims 1 to 3 ,
The resistor is an aluminum alloy having a temperature coefficient of resistance of 2000 ppm/°C or less.
Shunt resistor. The shunt resistor according to any one of claims 1 to 3,
The resistor is an aluminum alloy having a temperature coefficient of resistance of 1000 ppm/°C or less.
Shunt resistor. The shunt resistor according to any one of claims 1 to 5 ,
The electrode has a plating including nickel or zinc.
Shunt resistor.