Shunt resistor

Abstract

The invention relates to a shunt resistor. A shunt resistor (1) is equipped with at least two elements (150) mounted to an electrode member (10). At least two elements (150) are equipped with resistors (5) having different electrical resistivity.

Description

Technical Field

[0001] The present invention relates to a shunt resistor. Background Art

[0002] There is a shunt resistor that allows current to flow through the resistor, and measures the magnitude of the current based on the voltage (potential difference) across its two ends. Such a shunt resistor is equipped with a resistor and two electrodes connected to both ends of the resistor. Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Application Laid-Open No. 2018-536166 Summary of the Invention Problems to be Solved by the Invention

[0004] In a shunt resistor, in order to reduce the power loss caused by the resistor, a low resistance value is set. For example, in order to detect a current of 40 A, a resistance value of 0.5 mΩ is used, and the potential difference across the two ends of the resistor is about 20 mV. When the same potential difference is desired to be detected, when a current of 400 A flows, a resistance value of 50 μΩ is required. Thus, when the current value to be detected is different, the difference in the required resistance values is about 10 times.

[0005] When measuring a current of 400 A, for example, it is considered to use a 50 μΩ shunt resistor. However, if it is desired to also use the same shunt resistor to detect a current near 10 A, there is a case where the requirement for the measurement range becomes wider due to circuit design reasons. In this case, when measuring a current of 10 A using a 50 μΩ shunt resistor, since the potential difference becomes 0.5 mV, there is a problem that it is difficult to ensure the accuracy of current detection.

[0006] Thus, in a shunt resistor, it is desired to expand the range of the magnitude of the current to be measured (i.e., the measurement range). However, in the above-mentioned shunt resistor, since the measurement range largely depends on the resistivity (resistance value) of a single resistor disposed between the two electrodes, it is difficult to expand the measurement range. A shunt resistor in which a plurality of resistors are connected in series is known (for example, refer to Patent Document 1), but Patent Document 1 does not disclose a structure for expanding the measurement range.

[0007] Therefore, an object of the present invention is to provide a shunt resistor capable of expanding the measurement range. Means for Solving the Problems

[0008] In one aspect, there is provided a shunt resistor including: an electrode member made of a conductive material, and at least two elements mounted on the electrode member. The at least two elements are equipped with resistors having different resistivities.

[0009] In one mode, the at least two elements are stacked elements stacked in the thickness direction of the shunt resistor. In one mode, the at least two elements that are the stacked elements have the same shape. In one mode, the at least two elements are series elements arranged in the length direction of the shunt resistor.

[0010] In one mode, the resistor is provided with a sintered body arranged on one side and an alloy arranged on the other side. In one mode, the sintered body has a resistivity value of 450 μΩ·cm or more. In one mode, the alloy is composed of a CuMn-based alloy, and the sintered body is composed of a sintered body in which metal particles such as NiCr, CuMn, or CuNi and insulating particles such as alumina are mixed. In one mode, the electrode member has a convex portion formed in the central portion. Effects of the Invention

[0011] The shunt resistor is provided with resistors having different resistivity (resistance values). By passing large and small currents through the two types of resistors, the magnitudes of the large and small currents can be measured. Thus, the shunt resistor can expand the measurement range. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view showing an embodiment of a shunt resistor for current detection. Figure 2 is Figure 1 a longitudinal sectional view of the shunt resistor shown. Figure 3 is a view showing another embodiment of the shunt resistor. Figure 4 is a view showing another embodiment of the shunt resistor. Figure 5 is a view showing another embodiment of the shunt resistor. Figure 6 is a view showing another embodiment of the shunt resistor. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding structural elements are given the same reference numerals and repeated descriptions are omitted.

[0014] Figure 1 is a perspective view showing an embodiment of a shunt resistor for current detection. Figure 2 isFigure 1 A longitudinal cross-sectional view of the shunt resistor shown. As Figure 1 well as Figure 2 shown, the shunt resistor 1 is provided with an electrode member 10 made of a conductive material and at least two elements 150 mounted on the electrode member 10.

[0015] In Figure 1 the Figure 2 embodiment shown, the shunt resistor 1 is provided with two elements 150. However, it may also be provided with three or more elements 150. The plurality of elements 150 have the same shape (structure). With such a structure, the elements 150 can have high durability (thermal cycle, power cycle), and their reliability can be improved. Furthermore, the shunt resistor 1 equipped with a plurality of elements 150 having the same shape can have high stress balance. The plurality of elements 150 having the same shape are easy to design and can improve production efficiency.

[0016] Since the plurality of elements 150 have the same shape (structure), the structure of a single element 150 will be described below. The element 150 is provided with a plate-shaped (thin plate-shaped) resistor 5A (or resistor 5B) having a prescribed thickness and width, and a plate-shaped (thin plate-shaped) electrode (first electrode) 6A made of a conductive material. The electrode 6A is disposed on the side opposite to the electrode member 10 with the resistor 5A (or 5B) interposed therebetween.

[0017] In Figure 1 the Figure 2 embodiment shown, the plurality of elements 150 are respectively stacked elements stacked in the thickness direction of the shunt resistor 1. The thickness direction of the shunt resistor 1 is a direction parallel to the vertical direction. The first direction is the length direction of the shunt resistor 1. The second direction is the width direction of the shunt resistor 1, which is perpendicular to the first direction.

[0018] The two resistors 5A, 5B provided in the shunt resistor 1 have different resistivity (resistance values). More specifically, one of the two resistors 5A, 5B is made of a material with a large resistance value (for example, a sintered body), and the other is made of a material with a small resistance value (for example, an alloy). Hereinafter, in this specification, the resistors 5A, 5B may not be particularly distinguished and are sometimes referred to as resistor 5.

[0019] In one embodiment, the sintered body serving as the resistor 5 has a resistivity value of 450 to 500 μΩ·cm. For example, the sintered body is composed of NiCr - Al2O3, CuMn - Al2O3, CuNi - Al2O3, etc., which are sintered bodies formed by mixing metal particles such as NiCr, CuMn, or CuNi and insulating particles such as alumina. In one embodiment, the alloy serving as the resistor 5 has a resistivity value of 44 μΩ·cm. For example, the alloy is composed of a CuMn - based alloy or a CuMnNi - based alloy. In this embodiment, the resistivity values of the two resistors 5A and 5B differ by approximately 10 times.

[0020] In Figure 1 and Figure 2 the embodiment shown, since the two resistors 5A and 5B have the same shape, hereinafter, a single resistor 5 will be described. The resistor 5 has a first resistor surface 5a and a second resistor surface 5b which is the surface opposite to the first resistor surface 5a. The electrode member 10 is connected to the first resistor surface 5a, and the electrode 6A is connected to the second resistor surface 5b. That is, the electrode 6A, the resistor 5, and the electrode member 10 are stacked in sequence in the thickness direction of the shunt resistor 1.

[0021] The electrode member 10 is provided with a contact portion 10a that contacts the element 150. The number of contact portions 10a corresponds to the number of elements 150. In this embodiment, since the shunt resistor 1 is provided with two elements 150, the electrode member 10 has two contact portions 10a.

[0022] The two elements 150 are symmetrically arranged with respect to the center line CL of the electrode member 10 and are arranged in series and separated with respect to the electrode member 10 in the first direction of the shunt resistor 1. The center line CL is an imaginary line that extends parallel to the second direction of the shunt resistor 1 and bisects the electrode member 10. The electrode member 10 has end portions 23 in the first direction.

[0023] The electrode member 10 can also be connected to the first resistor surface 5a of the resistor 5 by a connection method such as welding with a conductive binder (silver paste using silver nanoparticles, copper paste using copper nanoparticles), pressure welding, or soldering. The electrode 6A is also connected to the second resistor surface 5b of the resistor 5 by the same connection method. In order to enable soldering installation of the electrode 6A, surface treatment such as Sn plating or Ni plating is performed. The surface plating of the electrode 6A may not be performed.

[0024] The electrode member 10 has a structure capable of adjusting the resistance temperature coefficient (TCR) according to its thickness. The resistance temperature system (TCR) is an index representing the ratio of the change in the resistance value caused by temperature. More specifically, by adjusting the thickness of the electrode member 10, the accuracy of the TCR can be improved. For example, by thinning the thickness of the electrode member 10, the TCR can be reduced. In one embodiment, the electrode member 10 may have the same thickness as the resistance 5, or may have a thickness thinner than that of the resistance 5.

[0025] As Figure 1 and Figure 2 shown, the shunt resistor 1 is mounted on the mounting pad model. One end of the voltage detection wiring 25 is connected to the central portion of the upper surface of the electrode member 10, and the other end of the voltage detection wiring 25 is connected to a connector (not shown in the figure). In one embodiment, the voltage detection wiring 25 may also be a bonding wire. On the upper surface of the electrode member 10, a surface treatment capable of connecting a bonding wire (for example, NiP plating or NiP plating, etc.) is implemented. The shunt resistor device is constituted by the shunt resistor 1 and the voltage detection wiring 25 connected to the upper surface of the electrode member 10.

[0026] The shunt resistor 1 is disposed on the adjacent energization patterns 30. The energization patterns 30 are formed on a circuit board such as a printed circuit board (not shown in the figure). The element 150 (more specifically, the electrode 6A) is connected to the energization pattern 30 by soldering or the like.

[0027] Between the energization patterns 30, a voltage detection wiring (lead wire) 33 is disposed. The voltage detection wiring 33 is a voltage detection terminal for detecting the potential difference generated between the electrode member 10. The voltage detection wiring 25 is a wiring (terminal) for detecting the potential difference between the electrode member 10 and the voltage detection wiring 33.

[0028] The electrode member 10 to which the voltage detection wiring 25 is connected to the shunt resistor 1, and the voltage detection wiring 33 is connected to the energization pattern 30, forming a current path flowing in the thickness direction of the shunt resistor 1 from the energization pattern 30. The potential difference between the voltage detection wiring 25 and the voltage detection wiring 33 (that is, the potential difference at the resistance 5) is measured by a voltage measuring device (not shown in the figure). By measuring this potential difference, the current value is calculated.

[0029] By flowing a large current through the resistance 5 having a small resistivity value, heat generation from the resistance 5 can be suppressed. On the other hand, by flowing a small current through the resistance 5 having a small resistivity value, the potential difference becomes small. It is difficult to measure a small potential difference.

[0030] According to this embodiment, a shunt resistor 1 having a large difference in resistance values can be implemented in one structure. More specifically, since the shunt resistor 1 is provided with resistors 5 having different resistivities, by passing a small current through the resistor 5 having a large resistivity value, the potential difference can be increased. As a result, the potential difference can be easily measured.

[0031] For example, as Figure 1 shown, when the resistance value of one resistor 5 is set to 50 μΩ and the resistance value of another resistor 5 is set to 500 μΩ, and the voltage detection wiring 25 is led out from the electrode member 10 of the shunt resistor 1, and each voltage detection wiring 33 between the energization patterns 30 is led out, a potential difference corresponding to 50 μΩ is obtained from one voltage detection wiring 33 and the voltage detection wiring 25 when the resistance value of one resistor 5 is 50 μΩ. A potential difference corresponding to 500 μΩ is obtained from the voltage detection wiring 25 and another voltage detection wiring 33 when the resistance value of the other resistor 5 is 500 μΩ.

[0032] In the case of detecting a current at the 400 A level, the detection wiring between the low resistance values is used, and in the case of detecting a current at the 10 A level, the detection wiring on the high resistance value side is used. With such a structure, detection can be performed over a wide current range. In this case, the difference in resistance values between the two resistors 5A and 5B is 10 times.

[0033] In addition, when a load of 400 A current is applied using the shunt resistor 1 provided with the resistor 5 having such a resistance value, the resistor 5 having a resistance value of 50 μΩ generates 8 W of heat, and the resistor 5 having a resistance value of 500 μΩ generates 80 W of heat.

[0034] Since the resistor 5 that generates 80 W of heat becomes high temperature, more efficient heat dissipation is required. In this embodiment, since the entire surface of the element 150 as a plate-like laminated element is connected to the energization pattern 30 via the electrode 6A, the contact area between the electrode 6A and the energization pattern 30 can be increased. Thus, the shunt resistor 1 can dissipate heat from the resistor 5 via the energization pattern 30.

[0035] In the above embodiment, the plurality of elements 150 have the same shape, but in one embodiment, the plurality of elements may also have different shapes. In one embodiment, the heat dissipation performance of the resistor 5 can be improved by increasing the size of the resistor 5 of the element 150.

[0036] Figure 3 It is a diagram showing another embodiment of the shunt resistor. In Figure 3 the shown embodiment, the element 150 is a series element arranged in the longitudinal direction of the shunt resistor 1. As Figure 3As shown, the electrode 6A, the resistor 5, and the electrode member 10 are arranged in sequence in the longitudinal direction of the shunt resistor 1. In Figure 3 the illustrated embodiment, both end portions 23 of the electrode member 10 correspond to two contact portions 10a.

[0037] Figure 4 FIG. is a diagram showing another embodiment of the shunt resistor. In Figure 4 the illustrated embodiment, the electrode member 10 has a convex portion 10b formed in the central portion. The convex portion 10b is disposed between the elements 150, 150 that are laminated elements. By forming the convex portion 10b, heat from the resistor 5 can be dissipated with higher efficiency.

[0038] As Figure 4 shown, the number of voltage detection wirings 25 corresponds to the number of elements 150. Accordingly, the shunt resistor device is provided with at least two voltage detection wirings 25 connected to at least two contact portions 10a. The two voltage detection wirings 25 are disposed on the side of both end portions 23 of the electrode member 10.

[0039] By adjusting the positions (bonding positions) of the two voltage detection wirings 25, the TCR can be adjusted. More specifically, by disposing the two voltage detection wirings 25 on the side of both end portions 23, the TCR decreases, and by disposing the two voltage detection wirings 25 on the central portion side of the electrode member 10, the TCR increases.

[0040] Figure 5 FIG. is a diagram showing another embodiment of the shunt resistor. In Figure 5 the illustrated embodiment, the shunt resistor device is provided with a jumper terminal 10c extending from the central portion of the electrode member 10 instead of the voltage detection wiring 25. The jumper terminal 10c is a member integrally formed with the electrode member 10 and is connected to the energization pattern 31. In the present embodiment, the jumper terminal 10c extends from below the electrode member 10.

[0041] Figure 6 FIG. is a diagram showing another embodiment of the shunt resistor. In Figure 6 the illustrated embodiment, the element 150 as a laminated element may also be provided with an electrode (second electrode) 6B disposed between the resistor 5 and the electrode member 10.

[0042] The above embodiments are described for the purpose that a person having ordinary knowledge in the technical field to which the present invention pertains can implement the present invention. Various modifications of the above embodiments are obvious to those skilled in the art, and the technical concept of the present invention is also applicable to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed as covering the broadest scope consistent with the technical concept defined by the scope of the claims. Industrial applicability

[0043] The present invention can be used for shunt resistors Description of reference numerals 1 Shunt resistor 5(5A, 5B) Resistor 5a First resistor surface 5b Second resistor surface 6A First electrode 6B Second electrode 10 Electrode member 10a Contact portion 10b Protrusion 10c Jumper terminal 23 Both ends 25 Voltage detection wiring 30 Energization pattern 31 Energization pattern 33 Voltage detection wiring 150 Component CL Center line

Claims

1. A shunt resistor, wherein, Equipped with: An electrode member made of a conductive material; and At least two elements mounted on the electrode member, The at least two elements being equipped with resistors having different resistivities.

2. The shunt resistor according to claim 1, wherein, The at least two elements are laminated elements laminated in the thickness direction of the shunt resistor.

3. The shunt resistor according to claim 2, wherein, The at least two elements as the laminated elements have the same shape.

4. The shunt resistor according to claim 1, wherein The at least two elements are series elements arranged in the length direction of the shunt resistor.

5. The shunt resistor according to claim 1, wherein, The resistor is equipped with a sintered body disposed on one side and an alloy disposed on the other side.

6. The shunt resistor according to claim 5, wherein, The sintered body has a resistivity value of 450 μΩ·cm or more.

7. The shunt resistor according to claim 5, wherein, The alloy is composed of a CuMn-based alloy, The sintered body is composed of a sintered body in which metal particles of NiCr, CuMn, or CuNi and insulating particles such as alumina are mixed.

8. The shunt resistor according to claim 1, wherein The electrode member has a convex portion formed in the central portion.

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