Current detection device

Abstract

In the magnetic shielding portions (3u, 3v) of the current detection device of the present invention, bending portions (30u, 30v) are formed such that near the end portion (6u) where the opening portion (5u) is formed, as approaching the end portion (6u), the opening area of the opening portion (5u) gradually becomes larger. When focusing on the U-phase and its adjacent V-phase, due to the influence of the current flowing in the V-phase conductor (Bv), a magnetic field (Bvu) is input from the V-phase to the U-phase into the magnetic shielding portion (3u), but the magnetic field (Bvu) is guided by the bending portions (30u, 30v) and concentrated at the end portion (6u) of the opening portion (5u) of the magnetic shielding portion (3u). That is, since the gap between the bending portions (30u, 30v) is narrow, the local magnetic resistance becomes small, the magnetic flux can be concentrated in the bending portions (30u, 30v), and the magnetic flux flowing into the inside of the magnetic shielding portion (3u) can be reduced. Therefore, the magnetic detection element (2u) is not easily affected by the magnetic field from the adjacent phase.

Description

Technical Field

[0001] The present invention relates to a current detection device. Background Art

[0002] There is a current detection device that is provided near a conductor, detects a magnetic field generated according to a current flowing through the conductor, and detects the amount of current flowing through the conductor. The current detection device is provided, for example, near each of three-phase conductors led out from an inverter that converts direct current into three-phase alternating current.

[0003] Patent Document 1 discloses a current sensor including: a conductive portion through which a current flows; a detection portion that detects a magnetic field generated by the current flowing through the conductive portion; and a shield that surrounds the conductive portion and the detection portion.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-181415 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] The technique described in Patent Document 1 has a problem that the current detection accuracy deteriorates due to the influence of the current flowing through an adjacent conductor.

[0009] Technical Solution for Solving the Technical Problem

[0010] The current detection device of the present invention includes: a first current detection element; a second current detection element; a first shield portion that forms a first accommodation space for accommodating a part of a first conductor and the first current detection element, and forms a first opening portion that communicates the first accommodation space with the outside; and a second shield portion that is adjacent to the first shield portion, forms a second accommodation space for accommodating a part of a second conductor and the second current detection element, and forms a second opening portion that communicates the second accommodation space with the outside. The first shield portion is formed such that, near an end portion where the first opening portion is formed, as approaching the end portion, an opening area of the first opening portion gradually increases. The second shield portion is formed such that, near an end portion where the second opening portion is formed, as approaching the end portion, an opening area of the second opening portion gradually increases.

[0011] Advantages of the Invention

[0012] According to the present invention, by suppressing the influence of the current flowing through an adjacent conductor, it is possible to reduce deterioration of current detection accuracy. Brief Description of the Drawings

[0013] Figure 1 is a perspective view of the current detection device.

[0014] Figure 2 is a cross-sectional view of the current detection device.

[0015] Figure 3 The (A) and (B) of are diagrams showing the influence of magnetic shielding portions with different shapes on the magnetic field from the outside.

[0016] Figure 4 The (A) and (B) of are diagrams showing the influence of magnetic shielding portions with different shapes on the magnetic field from the adjacent phase. Detailed implementation mode

[0017] Figure 1 is a perspective view of the current detection device 100 of the present implementation mode.

[0018] In the present implementation mode, the current detection device 100 detects the value of the current flowing in the Z-axis direction among the three orthogonal directions (X-axis, Y-axis, and Z-axis directions) shown in the figure in the U-phase, V-phase, and W-phase conductors Bu, Bv, and Bw in a non-contact manner.

[0019] The current detection device 100 is constituted by arranging a U-phase current detection device 100u, a V-phase current detection device 100v, and a W-phase current detection device 100w side by side in the X-axis direction among the three orthogonal directions (X-axis, Y-axis, and Z-axis directions) shown in the figure.

[0020] The current detection device 100u detects the value of the current flowing in the U-phase conductor Bu in a non-contact manner. The current detection device 100v detects the value of the current flowing in the V-phase conductor Bv in a non-contact manner. The current detection device 100w detects the value of the current flowing in the W-phase conductor Bw in a non-contact manner.

[0021] The structure of the U-phase current detection device 100u will be described. The magnetic detection element 2u placed on the substrate 1u is provided near the upper part shown in the figure of the U-phase conductor Bu. A specified length portion of the conductor Bu, the substrate 1u, and the magnetic detection element 2u are housed in the magnetic shielding portion 3u having a substantially U-shaped cross section. That is, the magnetic shielding portion 3u forms a housing space 4u for housing a part of the conductor Bu, the substrate 1u, and the magnetic detection element 2u, and forms an opening portion 5u for communicating the housing space 4u with the outside. Moreover, the magnetic shielding portion 3u is formed such that near the end portion 6u where the opening portion 5u is formed, the opening area of the opening portion 5u gradually increases as it approaches the end portion 6u.

[0022] The structures of the V-phase current detection device 100v and the W-phase current detection device 100w are the same as the structure of the U-phase current detection device 100u.

[0023] The conductors Bu, Bv, and Bw are current conductors that extend in the Z-axis direction and carry current in the Z-axis direction.

[0024] The conductors Bu, Bv, and Bw are made of a conductive material through which current flows. The conductors Bu, Bv, and Bw generate a magnetic field around them according to the value of the current flowing through them.

[0025] The magnetic detection elements 2u, 2v, and 2w detect the magnetic field generated by the current flowing through the conductors Bu, Bv, and Bw. The magnetic detection elements 2u, 2v, and 2w detect, for example, a magnetic field that is substantially parallel to the X-axis direction in Figure 1 . The magnetic detection elements 2u, 2v, and 2w use semiconductors such as Si and GaAs, for example, to convert the detected magnetic field into a voltage, and the converted voltage is used for the control of the motor.

[0026] Let the width of the magnetic shielding portions 3u, 3v, and 3w in the X-axis direction be W, the height in the Y-axis direction be H, and the depth in the Z-axis direction be L (the illustration is omitted). The magnetic shielding portions 3u, 3v, and 3w are made of silicon steel sheets and have the function of concentrating the magnetic flux generated by the current and shielding the magnetic field from the outside. For example, they are made of magnetic materials such as Si-Fe and Ni-Fe that have a high saturation magnetic flux density. The magnetic detection elements 2u, 2v, and 2w and a part of the conductors Bu, Bv, and Bw are arranged inside the magnetic shielding portions 3u, 3v, and 3w, and the magnetic field input from the outside to the magnetic detection elements 2u, 2v, and 2w is shielded, thereby reducing the influence of interference.

[0027] Figure 2 is a cross-sectional view of the current detection device 100 according to the present embodiment. This cross-sectional view is a cross-section of a plane parallel to the plane formed by the X-axis and Y-axis of Figure 1 . The same reference numerals are given to the same parts as in Figure 1 , and their descriptions are omitted. The U-phase current detection device 100u, the V-phase current detection device 100v, and the W-phase current detection device 100w are arranged side by side in the X-axis direction among the three orthogonal directions (X-axis, Y-axis, and Z-axis directions) in the figure. Moreover, the magnetic shielding portions 3u, 3v, and 3w are formed such that near the ends 6u, 6v, and 6w where the openings 5u, 5v, and 5w are formed, the opening area of the openings 5u, 5v, and 5w gradually increases as they approach the ends 6u, 6v, and 6w.

[0028] In the present embodiment, the current detection device 100 detects the currents flowing through the three-phase conductors Bu, Bv, and Bw of the U-phase, V-phase, and W-phase, respectively. The current detection device 100 is a so-called coreless current sensor having magnetic detection elements 2u, 2v, 2w and magnetic shielding portions 3u, 3v, 3w. In the coreless current sensor, the magnetic field generated by energizing the conductors Bu, Bv, Bw is concentrated by the magnetic shielding portions 3u, 3v, 3w to increase the magnetic flux density, and is detected by the magnetic detection elements 2u, 2v, 2w and a voltage is output. In addition, the coreless current sensor is smaller in volume than the core type, but the magnetic shielding effect of the magnetic shielding portions 3u, 3v, 3w is weak. Therefore, the influence of an interfering magnetic field (such as crosstalk) other than the magnetic field generated in the conductors Bu, Bv, Bw to be detected easily causes a detection error, and there is a problem that the current detection accuracy deteriorates.

[0029] Figure 3 (A), Figure 3 (B) is a diagram showing the influence of magnetic shielding portions 3 of different shapes on an external magnetic field. Figure 3 (A) shows a comparative example of the present embodiment, Figure 3 (B) shows the present embodiment. In Figure 3 (A) and Figure 3 (B), the U-phase current detection device 100u is taken as an example for explanation. In the same parts as Figure 1 、 Figure 2 the same reference numerals are given and their descriptions are omitted.

[0030] In Figure 3 (A) of the comparative example shown, the magnetic shielding portion 3’u of the comparative example is formed in a substantially U-shape, and its opening area is constant including the end portion forming the opening. On the other hand, in the magnetic shielding portion 3u of the present embodiment shown in Figure 3 (B), a bent portion 30u is formed so that the opening area of the opening gradually increases as it approaches the end portion 6u near the end portion forming the opening. The bending angle θ of the bent portion 30u is preferably 20 degrees to 60 degrees.

[0031] As Figure 3 (A) shows, when the magnetic field B acts from the outside of the magnetic shielding portion 3’u in the X-axis direction, the magnetic field B’ passing through the magnetic shielding portion 3’u is guided in the X-axis direction and then guided in the Y-axis direction. On the other hand, in the present embodiment, as Figure 3 (B) shows, when the magnetic field B acts from the outside of the magnetic shielding portion 3u in the X-axis direction, the magnetic field B’ passing through the magnetic shielding portion 3u is guided in the Y-axis direction due to the bent portion 30u. That is, in the present embodiment, the influence of the external magnetic field received by the magnetic detection element 2u can be reduced.

[0032] Figure 4 (A),Figure 4 (B) is a diagram showing the influence of the magnetic shielding portions 3 of different shapes on the magnetic fields from adjacent phases. Figure 4 (A) shows a comparative example of the present embodiment, Figure 4 (B) shows the present embodiment. The same reference numerals are given to the same parts as Figure 1 、 Figure 2 and their description is omitted.

[0033] In Figure 4 the magnetic shielding portion 3’u in the comparative example shown in (A) is formed in a substantially U shape, and its opening area remains unchanged including the end portion forming the opening. When focusing on the U phase and its adjacent V phase, due to the influence of the current flowing in the V-phase conductor Bv, the magnetic field B’vu is input from the V phase to the magnetic shielding portion 3’u in the -X axis direction. The magnetic field B’vu is input to the entire side surface of the magnetic shielding portion 3’u. That is, since the magnetic resistance is uniform, the magnetic fluxes from adjacent phases flow in almost uniformly. Therefore, in the comparative example, the magnetic detection element 2u is easily affected by the magnetic fields from the outside.

[0034] On the other hand, in Figure 4 the magnetic shielding portions 3u, 3v in the present embodiment shown in (B), the bent portions 30u, 30v are formed, so that near the end portion 6u forming the opening portion 5u, as approaching the end portion 6u, the opening area of the opening portion 5u gradually becomes larger. When focusing on the U phase and its adjacent V phase, due to the influence of the current flowing in the V-phase conductor Bv, the magnetic field Bvu is input from the V phase to the magnetic shielding portion 3u, but the magnetic field Bvu is guided by the bent portions 30u, 30v and concentrated at the end portion 6u of the opening portion 5u of the magnetic shielding portion 3u. That is, since the gap between the adjacent bent portions 30u, 30v is narrow, the local magnetic resistance becomes small, the magnetic fluxes can be concentrated in the adjacent bent portions 30u, 30v, and the magnetic fluxes flowing into the inside of the magnetic shielding portion 3u can be reduced. Therefore, in the present embodiment, the magnetic detection element 2u is not easily affected by the magnetic fields from adjacent phases.

[0035] The current detection device 100 is provided near, for example, three-phase conductors led out from an inverter for converting direct current into three-phase alternating current, and detects the values of the currents flowing in the U-phase, V-phase, and W-phase conductors Bu, Bv, Bw in a non-contact manner. The currents flowing in the conductors Bu, Bv, Bw are supplied to a motor, and the detection error can be reduced by the current detection device 100 of the present embodiment. Therefore, the torque accuracy of the motor can be improved based on the detected current values. In addition, although the magnetic shielding ability of the magnetic shielding portion 3 depends on the magnetic permeability, a material having a low magnetic permeability can also be used as the magnetic shielding portion 3.

[0036] According to this embodiment, by expanding the opening area of the end portion of the magnetic shielding portion 3, the interfering magnetic field of the adjacent X-axis component is guided in the Y-axis direction, the intensity of the interfering magnetic field detected by the magnetic detection element 2 can be reduced, and the detection error can be reduced. In other words, by enhancing the magnetic coupling with the adjacent phase at the end portion of the magnetic shielding portion 3, the magnetic flux from the adjacent phase flowing into the position where the magnetic detection element 2 is provided is reduced.

[0037] According to the embodiment described above, the following effects can be obtained.

[0038] (1) The current detection device 100 includes a first current detection element 2u; a second current detection element 2v; a first shielding portion 3u that forms a first accommodation space 4u for accommodating a part of the first conductor Bu and the first current detection element 2u, and forms a first opening portion 5u that communicates the first accommodation space 4u with the outside; a second shielding portion 3v that is adjacent to the first shielding portion 3u, forms a second accommodation space 4v for accommodating a part of the second conductor Bv and the second current detection element 2v, and forms a second opening portion 5v that communicates the second accommodation space 4v with the outside. The first shielding portion 3u is formed such that, in the vicinity of the end portion 6u where the first opening portion 5u is formed, as it approaches the end portion 6u, the opening area of the first opening portion 5u gradually increases. The second shielding portion 3v is formed such that, in the vicinity of the end portion 6v where the second opening portion 5v is formed, as it approaches the end portion 6v, the opening area of the second opening portion 5v gradually increases. Thereby, the influence of the current flowing through the adjacent conductors can be suppressed, and the deterioration of the current detection accuracy can be alleviated.

[0039] (Variant example)

[0040] The present invention can be implemented by modifying the embodiment described above as follows.

[0041] (1) An example is shown in which the bending angle θ of the bent portion 30 of the magnetic shielding portion 3 is fixed and bent linearly, so that in the vicinity of the end portion where the opening portion is formed, as it approaches the end portion 6, the opening area of the opening portion gradually increases. However, it may be bent in a curved shape, and it is sufficient that the opening area of the opening portion gradually increases as it approaches the end portion 6.

[0042] (2) An example is shown in which both end portions of the magnetic shielding portion 3 are bent, so that in the vicinity of both end portions where the opening portion is formed, as it approaches the end portion 6, the opening area of the opening portion gradually increases. However, it may be formed such that at least in the vicinity of the end portion on the side adjacent to the adjacent phase, as it approaches the end portion 6, the opening area of the opening portion gradually increases.

[0043] The present invention is not limited to the above embodiments, and other modes that can be considered within the technical idea of the present invention are also included in the scope of the present invention as long as the features of the present invention are not damaged. In addition, it may also be a structure that combines the above embodiments and multiple modified examples.

[0044] Reference Numeral Explanation

[0045] 1u, 1v, 1w substrates

[0046] 2u, 2v, 2w magnetic detection elements

[0047] 3u, 3v, 3w magnetic shielding parts

[0048] 4u, 4v, 4w accommodation spaces

[0049] 5u, 5v, 5w openings

[0050] 6u, 6v, 6w ends

[0051] Bu, Bv, Bw conductors

[0052] 100 Current detection device

[0053] 100u U-phase current detection device

[0054] 100v V-phase current detection device

[0055] 100w W-phase current detection device.

Claims

1. A current detection device, characterized in that, comprising: a first current detection element; a second current detection element arranged side by side with the first current detection element; a first shielding portion that forms a first accommodation space for accommodating a part of a first conductor and the first current detection element, and forms a first opening for communicating the first accommodation space with the outside; and a second shielding portion that is adjacent to the first shielding portion, forms a second accommodation space for accommodating a part of a second conductor and the second current detection element, and forms a second opening for communicating the second accommodation space with the outside, wherein the first shielding portion has: a first connecting portion that is disposed opposite to the second shielding portion and is spaced apart from the second shielding portion; and a first bending portion that is formed in a part of the pair of ends forming the first opening and closer to the end on the side of the second shielding portion, and the interval between the first bending portion and the second shielding portion is shorter than the interval between the first connecting portion and the second shielding portion, and as it approaches the end, the interval between the first bending portion and the second shielding portion becomes narrower, wherein the second shielding portion has: a second connecting portion that is disposed opposite to the first shielding portion and is spaced apart from the first shielding portion; and a second bending portion that is formed in a part of the pair of ends forming the second opening and closer to the end on the side of the first shielding portion, and the interval between the second bending portion and the first shielding portion is shorter than the interval between the second connecting portion and the first shielding portion, and as it approaches the end, the interval between the second bending portion and the first shielding portion becomes narrower.

2. The current detection device according to claim 1, characterized in that, the first bending portion and the second bending portion are formed to be bent by a predetermined angle with respect to the first connecting portion and the second connecting portion respectively.

3. The current detection device according to claim 1 or 2, characterized in that, comprising: a third current detection element arranged side by side with the second current detection element; and a third shielding portion that is adjacent to the second shielding portion, forms a third accommodation space for accommodating a part of a third conductor and the third current detection element, and forms a third opening for communicating the third accommodation space with the outside, wherein the third shielding portion has: a third connecting portion that is disposed opposite to the second shielding portion and is spaced apart from the second shielding portion; and a third bending portion that is formed in a part of the pair of ends forming the third opening and closer to the end on the side of the second shielding portion, and the interval between the third bending portion and the second shielding portion is shorter than the interval between the third connecting portion and the second shielding portion, and as it approaches the end, the interval between the third bending portion and the second shielding portion becomes narrower, wherein the second shielding portion has: a fourth connecting portion that is disposed opposite to the third shielding portion and is spaced apart from the third shielding portion; and The fourth bending portion is formed in a part of the pair of end portions including the end portion closer to the third shielding portion among the pair of end portions forming the second opening portion, and the interval between the fourth bending portion and the third shielding portion is shorter than the interval between the fourth connecting portion and the third shielding portion, and the interval between the fourth bending portion and the third shielding portion becomes narrower as it approaches the end portion.

Images