Current sensor

Abstract

To ensure that, although a core body is had whose cross section is shaped like the letter C and which has a corner, magnetic saturation at the corner hardly occurs.SOLUTION: Disclosed is a current sensor comprising: a core body that surrounds a conductor where the current to be detected flows and has a cross section shaped like the letter C, as viewed along a first direction in which the current to be detected flows; and a sensing element which is located in a first gap on the opening side of the shape of the letter C. The core body includes a second gap at corners on both closing sides of the shape of the letter C, as viewed along the first direction, and the second gap is such that the gap width on the side close to the conductor as viewed along the first direction is larger than the gap width on the side far from the conductor.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a current sensor. [Background technology]

[0002] A technique is known in which magnetic resistance is adjusted by providing a plurality of gaps and inserting a magnetic material into the gaps. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-154636 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, current sensors have come to have core bodies with C-shaped cross sections, such as rectangular cores, instead of circular core bodies, taking into consideration the heat dissipation properties of bus bars (conductors) that can handle large currents. In such configurations, magnetic saturation is likely to occur at the corners.

[0005] Therefore, in one aspect, an object of the present disclosure is to provide a core body having a C-shaped cross section with corner portions, while preventing magnetic saturation from occurring at the corner portions. [Means for solving the problem]

[0006] According to one aspect, the present invention provides a core body having a C-shaped cross section that surrounds a conductor through which a current to be detected flows when viewed in a first direction in which the current to be detected flows; a sensing element disposed in a first gap at an opening side of the C-shape; The core body has a second gap at both corners of the closed side of the C-shape when viewed in the first direction, A current sensor is provided in which the second gap has a larger gap width on a side closer to the conductor than on a side farther from the conductor when viewed in a direction along the first direction. Effect of the Invention

[0007] According to one aspect, the present disclosure makes it possible to have a core body having a C-shaped cross section with corner portions, while making it possible to prevent magnetic saturation from occurring at the corner portions. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a state in which a current sensor according to an embodiment of the present invention is arranged relative to three-phase bus bars. [Diagram 2] 2 is a plan view seen in the direction in which current flows in the bus bar, showing the state shown in FIG. 1. [Diagram 3] 4 is a plan view of the current sensor as viewed in the Y direction. FIG. [Figure 4] FIG. 11 is a contour diagram showing an analysis result relating to magnetic saturation characteristics according to a comparative example. [Diagram 5] FIG. 4 is a contour diagram showing an analysis result relating to magnetic saturation characteristics according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not limiting, and shapes and the like in the drawings may be partially exaggerated for the sake of explanation. In addition, in the drawings, for ease of viewing, reference symbols may be given to only some of the parts that exist in a plurality of parts with the same attribute.

[0010] Fig. 1 is a perspective view showing a state in which a current sensor 1 of this embodiment is arranged relative to a three-phase bus bar 80. Fig. 2 is a plan view seen in the direction in which a current flows in the bus bar 80, showing the state shown in Fig. 1.

[0011] 1 and 2, the XYZ coordinate axes are shown in a right-handed coordinate system.

[0012] 1, the current sensor 1 is provided for each of the three-phase bus bars 80. The three-phase bus bars 80 may form a current path that supplies current to a rotating electric machine (not shown) for driving a vehicle.

[0013] Each current sensor 1 generates an electric signal according to the magnitude of the current flowing through the corresponding bus bar 80. The current sensor 1 is of a Hall IC (Integrated Circuit) type. The bus bar 80 may have any shape, but in this embodiment, it is in the form of a plate having a cross-sectional shape (cross-sectional shape as viewed in the Y direction) in which the dimension in the X direction is significantly longer than the dimension (thickness) in the Z direction. Such a bus bar 80 can improve heat dissipation compared to a bus bar with a circular cross section. The bus bar 80 may have a uniform cross-sectional shape as viewed in the Y direction at least in the section passing through the current sensor 1.

[0014] Next, the configuration of one current sensor 1 will be described in more detail with reference to Fig. 3 onwards. Note that, in the following, the configuration of one arbitrary current sensor 1 among the three current sensors 1 will be particularly described, but the other two current sensors 1 may have the same configuration.

[0015] 3 is a plan view of the current sensor 1 as viewed in the Y direction. In the following description, unless otherwise specified, the cross-sectional shape is the cross-sectional shape as viewed in the Y direction.

[0016] The current sensor 1 has a core body 10. The core body 10 has a C-shaped cross-sectional shape surrounding the bus bar 80. In the example shown in FIG. 3, the C-shaped cross-sectional shape has an opening side on the positive side in the Z direction and a non-opening side (closed side) on the negative side in the Z direction. The C-shaped cross-sectional shape has a corner portion. That is, the C-shaped cross-sectional shape is not a cross-sectional shape with a circular part missing, but a cross-sectional shape with a non-circular part missing. In this embodiment, the C-shaped cross-sectional shape is a cross-sectional shape with a rectangular part missing, the dimension in the X direction being longer than the dimension in the Z direction, corresponding to the cross-sectional shape of the bus bar 80. In this case, four corner portions CN1 to CN4 are formed. Each of the corner portions CN1 to CN4 does not have to be a right angle, and may have a corner R as shown in FIG. 3.

[0017] The core body 10 has a gap GP1 for a sensing element at a spaced portion on the opening side of the C-shape. A sensing element 20 of the current sensor 1 is disposed in the gap GP1 for the sensing element. In this embodiment, the sensing element 20 is a Hall element that detects a magnetic field corresponding to a current.

[0018] When viewed in the Y direction, the core body 10 has a shape symmetrical about a straight line L in the XZ plane passing through the center point in the X direction and parallel to the Z direction. The gap GP1 for the sensing element is formed so as to pass through the straight line L. Note that when viewed in the Y direction, the bus bar 80 also has a shape symmetrical about the straight line L and is disposed symmetrical about the straight line L.

[0019] In this embodiment, the core body 10 has gaps (hereinafter, for the sake of distinction, also referred to as "corner gaps GP2, GP3", respectively) at both corners CN2 and CN3 on the negative side in the Z direction (the closed side of the C-shape) of the corners CN1 to CN4.

[0020] In this embodiment, the core body 10 is divided into three parts, which will be referred to as a first core 11, a second core 12, and a third core 13, respectively, hereinafter, for the sake of distinction.

[0021] The first core 11 and the second core 12 form a gap GP1 for the sensing element. That is, the first core 11 and the second core 12 are located on both sides of the gap GP1 for the sensing element.

[0022] The first core 11 and the second core 12 may be formed of a wound core, but are preferably formed of a laminated core. The lamination direction of the laminated core is preferably the Y direction. In this case, the molding (machining) of the first core 11 and the second core 12 becomes easy, and the productivity is improved. The material of the laminated core may be a silicon steel plate or the like.

[0023] The third core 13 faces the gap GP1 for the sensing element in the Z direction via the bus bar 80. The third core 13 cooperates with the first core 11 and the second core 12 to form corner gaps GP2 and GP3 at the corner portions CN2 and CN3. That is, a corner gap GP2 is formed between the third core 13 and the first core 11, and a corner gap GP3 is formed between the third core 13 and the second core 12.

[0024] The third core 13 may be formed of a wound core, but is preferably formed of a laminated core. The lamination direction of the laminated core for the third core 13 may be the Y direction, the same as the first core 11 and the second core 12, but is preferably the Z direction. When the lamination direction of the third core 13 is the Z direction, the effect of eddy currents in the third core 13 can be reduced, and the performance of the current sensor 1 (for example, the linearity of the output characteristics) can be improved.

[0025] The third core 13 preferably has a constant cross-sectional shape when viewed in the Z direction. That is, the third core 13 preferably has a rectangular shape when viewed in the Y direction. In this case, it becomes possible to set the lamination direction of the third core 13 to the Z direction, and the above-mentioned effects can be obtained. In this case, the third core 13 can also be easily used for other variations of current sensors (for example, current sensors having a core body 10 with a different shape), and in this case, costs can be reduced by standardizing parts.

[0026] In this way, by forming the first core 11, the second core 12, and the third core 13 as laminated cores, it is possible to reduce costs compared to forming them by a wound core method. In addition, the yield (material utilization rate) of each steel plate for forming the core body 10 can be increased. That is, one steel plate for each of the first core 11, the second core 12, and the third core 13 can be punched out within an area smaller than the outer shape of the core body 10 when viewed in the Y direction, and the yield rate can be increased. In particular, in this embodiment, the first core 11 and the second core 12 are in an L-shape, and the third core 13 is in an I-shape, so that the material occupation area is reduced in the material layout, and the material utilization rate can be effectively increased.

[0027] The features of the corner gaps GP2 and GP3 of this embodiment will be described with continued reference to Fig. 3. Due to the above-mentioned symmetry, only the corner gap GP2 will be mainly described below.

[0028] 3, corner gap GP2 has a gap width w1 on the side closer to bus bar 80 larger than a gap width w2 on the side farther from bus bar 80 when viewed in the Y direction. That is, corner gap GP2 has a V-shape that is narrower on the side farther from bus bar 80 (negative side in the Z direction). Here, the gap widths of corner gap GP2 (gap widths w1, w2) are dimensions along the X direction. However, if the X-direction end face of third core 13 is not a plane having the X direction as a normal line, the gap width may be evaluated along a direction perpendicular to the X-direction end face of third core 13.

[0029] In this embodiment, the gap width of the corner gap GP2 gradually decreases as it moves away from the busbar 80. In this case, the gap width of the corner gap GP2 may be changed in a constant amount (i.e., proportional relationship) with respect to the change in the distance (distance in the Y direction) toward the side away from the busbar 80, or may not be constant. In another modification, the gap width of the corner gap GP2 may suddenly change in stages (step-like) in the process of moving toward the side away from the busbar 80. In this embodiment, the side surface on the first core 11 side that forms the corner gap GP2 (the side surface facing the third core 13 in the X direction) is flat, but may include a curved surface. For example, the shape of the side surface on the first core 11 side that forms the corner gap GP2 may be adapted in consideration of the effect of nonlinearity of current detection.

[0030] Next, the effects of this embodiment will be further described in comparison with a comparative example with reference to Figures 4 and 5. In the following description, the "inner side" of the core body 10 refers to the side closer to the center of the C-shaped cross-sectional shape when viewed in the Y direction, and the "outer side" of the core body 10 refers to the side farther from the center of the C-shaped cross-sectional shape when viewed in the Y direction.

[0031] Fig. 4 is a contour diagram showing the analysis results relating to the magnetic saturation characteristics of a comparative example, and Fig. 5 is a contour diagram showing the analysis results relating to the magnetic saturation characteristics of this embodiment. Figs. 4 and 5 are plan views viewed in the Y direction similar to Fig. 3. The magnetic field analysis relating to this analysis result was performed under the same conditions (magnitude of current, etc.).

[0032] The comparative example differs from this embodiment in that it does not have the corner gaps GP2 and GP3.

[0033] As can be seen from FIG. 4, in the comparative example not having corner gaps GP2, GP3, magnetic saturation is likely to occur at the corners of the core body (corners corresponding to corners CN2, CN3). In addition, in the corners, magnetic saturation is likely to occur on the inside (the side closer to the busbar 80), and magnetic saturation is significantly less likely to occur on the outside (the side farther from the busbar 80) than on the inside. Note that when magnetic saturation occurs at a certain current, the accuracy of current detection deteriorates when a current of a larger magnitude flows. Also, magnetic saturation is more likely to occur as the current increases. From this point of view, in the comparative example, restrictions are likely to occur on the magnitude of the current flowing through the busbar 80, which restricts the current sensor from increasing the current (increasing the current flowing through the rotating electric machine).

[0034] In contrast, in this embodiment, by providing the corner gaps GP2 and GP3, the inconveniences caused in the above-mentioned comparative example can be reduced. That is, according to this embodiment, magnetic saturation is less likely to occur at the corner portions CN2 and CN3 than in the comparative example, and the current flowing through the rotating electric machine can be increased.

[0035] In this embodiment, the corner gaps GP2, GP3 are set to a relatively large gap width w1 on the inside (the side closer to the bus bar 80), while a relatively small gap width w2 is set on the outside (the side farther from the bus bar 80). This is because, as described above, magnetic saturation is significantly less likely to occur on the outside (the side farther from the bus bar 80) than on the inside. In other words, according to this embodiment, the gap width on the outside (the side farther from the bus bar 80) of the corner gaps GP2, GP3 can be made relatively small while maintaining the effect of making magnetic saturation less likely to occur.

[0036] Here, when the gap width on the outside of the corner gaps GP2, GP3 (the side farther from the busbar 80) becomes larger, magnetic leakage from the outside of the corner gaps GP2, GP3 tends to become larger. Such magnetic leakage is likely to have an effect when multiple current sensors 1 are arranged side by side in the X direction as shown in Figures 1 and 2. In other words, magnetism leaking from one current sensor 1 is likely to affect the detection accuracy of another current sensor 1 adjacent to that one current sensor 1.

[0037] In contrast, according to this embodiment, as described above, the corner gaps GP2, GP3 are set to have a relatively small gap width w2 on the outer side (the side farther from the bus bar 80), thereby making it possible to reduce magnetic leakage from the outer side of the corner gaps GP2, GP3.

[0038] In this way, according to this embodiment, by providing corner gaps GP2 and GP3 having the gap width characteristics described above, a configuration in which magnetic saturation is less likely to occur can be realized while reducing the effects of magnetic leakage from outside the corner gaps GP2 and GP3.

[0039] Although each embodiment has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. In addition, it is also possible to combine all or a plurality of the components of the above-described embodiments.

[0040] For example, in the above-described embodiment, the core body 10 is formed from three divided cores (i.e., the first core 11, the second core 12, and the third core 13), but it may be formed from four or more divided cores. In this case, too, by providing corner gaps similar to the corner gaps GP2 and GP3, the same effects as those of the above-described embodiment can be obtained.

[0041] Also, for example, in the above-mentioned embodiment, the gap widths of the corner gaps GP2 and GP3 may be constant. In this case, the lamination direction of the third core 13 may be set to the Z direction, thereby obtaining the effect of reducing the influence of eddy currents. Such a modified example may be suitable for a configuration (specification) that does not need to accommodate large currents.

[0042] Also, for example, in the above-described embodiment, the X-direction end face of the third core 13 is a plane having a normal line in the X direction, but it may be a plane having a normal line in a direction inclined with respect to the X direction, or may include a curved surface. [Explanation of symbols]

[0043] 1...Current sensor, CN1 to CN4...Corner section, 80...Bus bar (conductor), 10...Core body, 11...First core, 12...Second core, 13...Third core, GP1...Gap for sensing element (first gap), GP2, GP3...Corner gap (second gap)

Claims

1. a core body having a C-shaped cross section that surrounds a conductor through which a current to be detected flows when viewed in a first direction in which the current to be detected flows; a sensing element disposed in a first gap at an opening side of the C-shape; The core body has a second gap at both corner portions on a closed side of the C-shape when viewed in a direction along the first direction, A current sensor, wherein the second gap has a larger gap width on a side closer to the conductor than on a side farther from the conductor when viewed in a direction along the first direction.

2. the core body has a first core and a second core on both sides of the first gap, and a third core at a position opposite to the first gap with the conductor interposed therebetween; The current sensor according to claim 1 , wherein the second gap is formed between the third core and the first core and between the third core and the second core.

3. The first core and the second core are each formed of a laminated core aligned along the first direction, The current sensor according to claim 2 , wherein the third core is formed by a laminated core along a second direction perpendicular to the first direction.

4. The current sensor according to claim 3 , wherein a plurality of the current sensors are arranged side by side in a third direction perpendicular to both the first direction and the second direction.

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