JP7567261B2 - Current Detector - Google Patents

Description

The present invention relates to a current detection device having a shunt resistor.

Conventionally, a current detection device having a shunt resistor has been proposed (see, for example, Patent Document 1). Specifically, this current detection device has a bus bar having a flat first member and a flat second member, and the first member and the second member are arranged to sandwich the shunt resistor. The first member and the second member each have a terminal portion that is connected to an external circuit. In this current detection device, protrusions are formed on the first member and the second member, and each terminal portion is provided on the protrusions. Therefore, in this current detection device, a step is formed between the terminal portion and the shunt resistor. In addition, the shunt resistor is made of a material with a smaller temperature coefficient of resistance than the bus bar.

In such a current detection device, it is difficult for current to flow through the path connecting the shunt resistor and the terminal portion. In other words, it is difficult for current to flow through the first and second members with a large resistance temperature coefficient that are located between the shunt resistor and the terminal portion. As a result, in the above current detection device, the potential difference between the shunt resistor and the terminal portion can be reduced. Therefore, by measuring the voltage between the terminal portions that are arranged to sandwich the shunt resistor with a small resistance temperature coefficient, the current flowing through the current detection device can be detected with high accuracy.

European Patent Application Publication No. 2474008

However, the current detection device described above tends to become large due to the protrusions formed on the first and second members. In particular, when mounting such a current detection device on a vehicle, it is desirable to miniaturize the current detection device so that the mounting space can be reduced.

In view of the above, the present invention aims to provide a current detection device that can improve detection accuracy while preventing the device from becoming too large.

In order to achieve the above object, a current detection device having a shunt resistor (20) is provided,
The first member (101) is a flat plate having a terminal portion (31, 32) on one side.
The present invention relates to a bus bar (10) having a first member (102) and a second member (102), and a shunt resistor having a flat plate shape having one surface (20a) and another surface (20b) opposite to the one surface, the other surface being arranged between the first member and the second member with the other surface being parallel to the other surfaces of the first member and the second member, and made of a material having a smaller temperature coefficient of resistance than the bus bar. The first member and the second member have grooves (50) in a portion of the one surface located on the opposite side to the shunt resistor across the terminal portion.
The shunt resistor is formed such that one surface of the shunt resistor is in contact with one surface of the first member and the second member.
The groove portion is recessed relative to one surface of the member, and extends in a normal direction to the one surface, passing through the terminal portion, in a direction intersecting the arrangement direction of the first member, the second member, and the shunt resistor, so as to intersect with an imaginary line (K) extending in a direction parallel to the one surfaces of the first member and the second member, and further, the groove portion extends to the ends of the first member and the second member on the shunt resistor side .

By forming the groove, current is less likely to flow through the path connecting the shunt resistor and the terminal. In other words, current is less likely to flow through the first and second members with a large resistance temperature coefficient that are located between the shunt resistor and the terminal. As a result, the above current detection device can reduce the potential difference between the shunt resistor and the terminal. Therefore, by measuring the voltage between the terminals that are arranged to sandwich the shunt resistor with a small resistance temperature coefficient, the current flowing through the current detection device can be detected with high accuracy.

In addition, by forming the groove, the deterioration of detection accuracy can be prevented, and therefore the size can also be prevented from increasing.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

1 is a perspective view of a current detection device according to a first embodiment. 1 is a plan view of a current detection device according to a first embodiment. FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. 11A and 11B are diagrams illustrating simulation results of a current flowing through a current detection device. FIG. 4 is a plan view of a current detection device according to a modified example of the first embodiment. FIG. 4 is a plan view of a current detection device according to a modified example of the first embodiment. FIG. 11 is a plan view of a current detection device according to a second embodiment. FIG. 11 is a plan view of a current detection device according to a modified example of the second embodiment. FIG. 11 is a plan view of a current detection device according to a modified example of the second embodiment. FIG. 11 is a plan view of a current detection device according to a modified example of the second embodiment.

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are identical or equivalent to each other are denoted by the same reference numerals.

First Embodiment
A first embodiment will be described with reference to the drawings. The current detection device of the present embodiment is suitable for use in detecting a motor current that drives an electric vehicle or the like.

As shown in Figs. 1 to 3, the current detection device of this embodiment includes a busbar 10, a shunt resistor 20, and a pair of terminals 31, 32. The busbar 10 includes a first member 101 having a flat plate shape with one surface 101a and another surface 101b opposite to the first surface 101a, and a second member 102 having a flat plate shape with one surface 102a and another surface 102b opposite to the first surface 102a. The first member 101 and the second member 102 are made of, for example, copper, and have the same thickness.

The shunt resistor 20 is flat with one surface 20a and another surface 20b opposite to the first surface 20a, and is made of Manganin (registered trademark) or the like, which has a smaller temperature coefficient of resistance than the busbar 10. In this embodiment, the shunt resistor 20 is thinner than the first member 101 and the second member 102.

The shunt resistor 20 is disposed between the first member 101 and the second member 102, and is integrated with the first member 101 and the second member 102 by welding or the like. Specifically, the shunt resistor 20, the first member 101, and the second member 102 are integrated so that their other surfaces 20b, 101b, and 102b are located on the same plane. Therefore, the one surface 20a of the shunt resistor 20 is recessed more than the one surface 101a of the first member 101 and the one surface 102a of the second member 102. In other words, the current detection device of this embodiment has a recess 40 formed in the portion where the shunt resistor 20 is provided.

The terminals 31 and 32 are rod-shaped and made of copper or the like, and are provided on one surface 101a of the first member 101 and one surface 102a of the second member 102, respectively, so as to sandwich the shunt resistor 20. The terminals 31 and 32 are provided on the first member 101 and the second member 102 by welding, riveting, soldering, or the like.

The above is the basic configuration of the current detection device in this embodiment. In this type of current detection device, terminals 31 and 32 are connected to an external circuit, and the current flowing is detected based on the voltage between terminals 31 and 32.

In the current detection device of this embodiment, grooves 50 are formed in the first member 101 and the second member 102. Hereinafter, the arrangement direction of the first member 101, the second member 102, and the shunt resistor 20 is defined as the X direction, and the direction perpendicular to the X direction and parallel to the surface direction of the first member 101, etc. is defined as the Y direction.

The groove portion 50 of this embodiment is formed along the Y direction on one surface 101a, 102a of the first member 101 and the second member 102, on the opposite side of the terminal portions 31, 32 from the shunt resistor 20. The groove portion 50 of this embodiment is formed, for example, by press molding, and has a triangular cross-sectional shape. However, the cross-sectional shape of the groove portion 50 is not limited to this, and may be rectangular.

In addition, the groove portion 50 in this embodiment is not formed to penetrate the first member 101 and the second member 102. In other words, the groove portion 50 is configured to have a bottom surface within the first member 101 and the second member 102.

According to the present embodiment described above, grooves 50 are formed on one surface 101a of the first member 101 and one surface 102a of the second member 102 on the opposite side of the shunt resistor 20 across the terminals 31 and 32. Therefore, when a current flows through the current detection device, as shown in FIG. 3 and FIG. 4, the current is less likely to flow through the path connecting the terminals 31 and 32 and the shunt resistor 20. In other words, the current is less likely to flow through the first member 101 and the second member 102, which have a large resistance temperature coefficient and are located between the terminals 31 and 32 and the shunt resistor 20. Therefore, in such a current detection device, it is possible to suppress the occurrence of a potential difference between the terminals 31 and 32 and the shunt resistor 20, and to suppress a decrease in detection accuracy.

In addition, in this embodiment, the grooves 50 are formed in the first member 101 and the second member 102 to prevent a decrease in detection accuracy. This also prevents the current detection device from becoming larger. In addition, the grooves 50 can be easily formed by press molding or the like compared to forming protrusions or the like in the first member 101 and the second member 102, which prevents the manufacturing process from becoming complicated and the yield from becoming low.

Furthermore, in this embodiment, the one surface 20a of the shunt resistor 20 is recessed, and the terminals 31, 32 are arranged on the one surface 101a, 102a side of the first member 101 and the second member 102. Therefore, compared to the case where the one surface 20a of the shunt resistor 20 is located on the same plane as the one surfaces 101a, 102a of the first member 101 and the second member 102, the current is prevented from spreading in the thickness direction of the first member 101 and the second member 102 between the part of the first member 101 and the second member 102 where the groove portion 50 is formed and the shunt resistor 20. In other words, it is possible to further prevent the current from flowing near the part of the first member 101 and the second member 102 where the terminals 31, 32 are provided. Therefore, it is possible to further prevent the detection accuracy from decreasing.

In addition, the groove portion 50 is not formed so as to penetrate the first member 101 and the second member 102. Therefore, compared to a case where the groove portion 50 is formed so as to penetrate the first member 101 and the second member 102 (i.e., a through hole is formed), it is possible to prevent the range through which the current flows in the first member 101 and the second member 102 from becoming smaller, and it is possible to prevent heat generation from becoming large.

(Modification of the first embodiment)
A modified example of the first embodiment will be described. For example, as shown in Fig. 5A, two grooves 50 may be formed in each of the first member 101 and the second member 102. Although not particularly shown, three grooves 50 may be formed in each of the first member 101 and the second member 102. Furthermore, the number of grooves 50 formed in the first member 101 may be different from the number of grooves 50 formed in the second member 102.

Also, as shown in FIG. 5B, the groove portion 50 may have a longer length (i.e., width) along the X direction compared to the first embodiment. Even if the groove portion 50 is formed in this manner, the formation of the groove portion 50 makes it difficult for current to flow near the terminal portions 31 and 32, so that the same effect as the first embodiment can be obtained.

Second Embodiment
A second embodiment will be described. In this embodiment, the shape of the groove 50 is changed from that of the first embodiment. As the rest of the configuration is the same as that of the first embodiment, a description thereof will be omitted here.

In this embodiment, as shown in FIG. 6, the groove portion 50 extends in a normal direction (hereinafter simply referred to as the normal direction) to the surface direction of the first member 101, etc., passing through the terminal portions 31 and 32 and intersecting with a virtual line K extending in the Y direction. Note that the normal direction to the surface direction of the first member 101, etc. can also be referred to as the direction when viewed from the normal direction to the surface direction of the first member 101, etc.

The groove portion 50 in this embodiment is substantially V-shaped so that it has a portion that intersects with the imaginary line K. Furthermore, the groove portion 50 in this embodiment is formed so as to reach the ends of the first member 101 and the second member 102 on the shunt resistor 20 side.

Compared to the first embodiment, this makes it possible to reduce the amount of current that flows around the portions of the first member 101 and the second member 102 where the terminal portions 31 and 32 are provided from the Y direction. This further prevents the detection accuracy from decreasing.

(Modification of the above second embodiment)
A modified example of the second embodiment will be described. In the second embodiment, as shown in Fig. 7A, the groove 50 may be substantially U-shaped in the normal direction. In Fig. 7A, the groove 50 is substantially U-shaped with two corners, but the groove 50 may be substantially U-shaped with no corners and only a curved portion.

Also, as shown in Figures 7B and 7C, the groove portion 50 may be formed so that it does not reach the ends of the first member 101 and the second member 102 on the shunt resistor 20 side in the normal direction. In other words, the groove portion 50 may be formed so as to terminate within the first member 101 and the second member 102.

Other Embodiments
Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

For example, in each of the above embodiments, the groove portion 50 may be formed only on one of the first member 101 and the second member 102. Also, in each of the above embodiments, the shunt resistor 20 may be arranged so as to be located on the same plane as one surface 101a of the first member 101 and 102a of the second member 102, and the other surface 20b side may be recessed. Furthermore, the shunt resistor 20 may have the same thickness as the first member 101 and the second member 102. With such a current detection device, the groove portion 50 is formed, and thus the same effect as in each of the above embodiments can be obtained.

In addition, in each of the above embodiments, the shape of the terminal portions 31, 32 can be changed as appropriate. For example, predetermined areas of the first member 101 and the second member 102 may be made into the terminal portions 31, 32, and the terminal portions 31, 32 may be connected to an external circuit by a bonding wire or the like, or the terminal portions 31, 32 may be connected to a printed circuit board as an external circuit by solder or the like. In other words, the terminal portions 31, 32 may be formed as part of the first member 101 and the second member 102.

REFERENCE SIGNS LIST 10 bus bar 20 shunt resistor 31, 32 terminal portion 50 groove portion 101 first member 101a one surface 101b other surface 102 second member 102a one surface 102b other surface

Claims (1)

A current detection device having a shunt resistor (20),
A bus bar (10) having a flat plate shape with one surface (101a, 102a) and another surface (101b, 102b) opposite to the one surface, the bus bar having a first member (101) and a second member (102) provided with terminal portions (31, 32) on the one surface side;
the shunt resistor is in the form of a flat plate having one surface (20a) and another surface (20b) opposite to the one surface, and is disposed between the first member and the second member with the other surface being parallel to the other surfaces of the first member and the second member, and is made of a material having a smaller temperature coefficient of resistance than the bus bar;
A groove portion (50) is formed in a portion of the first member and the second member that is located on the opposite side of the shunt resistor across the terminal portion, of the one surface,
The shunt resistor has one surface recessed from one surface of the first member and one surface of the second member,
the groove portion passes through the terminal portion in a normal direction to the one surface, and extends in a direction intersecting an arrangement direction of the first member, the second member, and the shunt resistor, so as to intersect with a virtual line (K) extending in a direction parallel to the one surface of the first member and the second member;
Further, the groove portion extends to an end of the first member or the second member on the shunt resistor side .

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