Current detection device

Abstract

To provide a current detection device for a three-phase motor capable of reducing an arithmetic load in a post-stage motor control device which performs vector control.SOLUTION: A current detection device detects currents flowing in current lines 6u, 6v and 6w of a three-phase motor based on magnetic detection elements S1 and S2 provided around the current lines 6u, 6v and 6w. The current lines 6u, 6v and 6w are disposed parallel with one another and at angles of an isosceles triangle in a cross-sectional view, and the magnetic detection elements S1 and S2 are disposed on a first virtual line L1 passing a vertex angle and a midpoint P1 of a bottom side of the isosceles triangle. A distance between the vertex angle and the midpoint P1 is equal with a length of the bottom side. The first magnetic detection element S1 is provided at the side of the vertex angle rather than the midpoint P1, and the second magnetic detection element S2 is provided at the opposite side of the vertex angle rather than the midpoint P1. A first detection direction D1 of the first magnetic detection element S1 is orthogonal to the first virtual line L1, and a second detection direction D2 of the second magnetic detection element S2 is parallel with the first virtual line L1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a current detection device. More specifically, the present invention relates to a current detection device that detects the current of each phase of a three-phase motor based on two magnetic detection elements. [Background Art]

[0002] So-called vector control is widely adopted as a control method for three-phase AC motors mounted in electric vehicles, household electrical appliances (for example, air conditioners, washing machines, etc.) and the like. In vector control, a motor control device generates a command signal for an inverter based on feedback control of d-axis current and q-axis current defined on d-q coordinates, which is a rotating orthogonal coordinate system of the motor. [Prior Art Literature] [Patent Literature]

[0003] [Patent Literature 1] International Publication No. 2013 / 058282 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] As described above, in a motor control device, since current feedback control is performed on d-q coordinates, it is necessary to convert the U-phase current, V-phase current, and W-phase current of the motor detected using a current detection device such as that disclosed in Patent Document 1, for example, into d-axis current and q-axis current. More specifically, in the motor control device, after first converting the three-phase currents (Iu, Iv, Iw) detected by the current detection device into two-phase currents (Iα, Iβ) defined in a fixed coordinate system through Clarke transformation, the two-phase currents (Iα, Iβ) are converted into two-phase currents (Id, Iq) defined in a d-q coordinate system through Park transformation using the rotation angle θ of the motor. As described above, in conventional vector control using the output of a current detection device, it is necessary for the motor control device to execute the calculation for converting three-phase currents (Iu, Iv, Iw) into two-phase currents (Id, Iq).

[0005] The present invention aims to provide a current detection device for a three-phase motor that can reduce the computational load in a subsequent motor control device that performs vector control. [Means for solving the problem]

[0006] (1) The current detection device according to the present invention detects the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, wherein when the current value flowing through the first phase current line is I1, the current value flowing through the second phase current line is I2, the current value flowing through the third phase current line is I3, the output value of the first magnetic detection element is V1, and the output value of the second magnetic detection element is V2, the relative positions of the first and second magnetic detection elements with respect to the first phase, second phase, and third phase current line, and the direction of detection are determined such that the following formula (1) holds true.

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[0007] (2) In this case, it is preferable that the first phase, second phase, and third phase current lines are parallel to each other and arranged at the corners of an isosceles triangle in cross-sectional view, and that the first magnetic detection element and the second magnetic detection element are each arranged on a first imaginary line passing through the vertex angle and the midpoint of the base of the isosceles triangle.

[0008] (3) In this case, it is preferable that the first phase, second phase, and third phase current lines are arranged parallel to each other and at equal intervals on a straight line in cross-sectional view, and that the first magnetic detection element and the second magnetic detection element are arranged on a second imaginary line that is perpendicular to the straight line and passes through a central current line which is located in the center of the first phase, second phase, and third phase current lines.

[0009] (4) The current detection device according to the present invention detects the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, wherein the first phase, second phase, and third phase current line are parallel to each other and arranged at the corners of an isosceles triangle in cross-section, and the first magnetic detection element and the second magnetic detection element are each arranged on a first imaginary line passing through the vertex and the midpoint of the base of the isosceles triangle.

[0010] (5) In this case, it is preferable that the distance between the vertex angle and the midpoint is equal to the length of the base, the first magnetic detection element is provided on the first imaginary line on the side of the vertex angle that is closer to the midpoint, the second magnetic detection element is provided on the first imaginary line on the side of the vertex angle that is closer to the midpoint, the first detection direction of the first magnetic detection element is perpendicular to the first imaginary line, and the second detection direction of the second magnetic detection element is parallel to the first imaginary line.

[0011] (6) In this case, it is preferable that the distance between the vertex angle and the midpoint is equal to the length of the base, the first magnetic detection element is provided on the first imaginary line on the side of the vertex angle that is closer to the midpoint than the midpoint, the second magnetic detection element is provided on the first imaginary line between the midpoint and the first magnetic detection element, the first detection direction of the first magnetic detection element is perpendicular to the first imaginary line, and the second detection direction of the second magnetic detection element is parallel to the first imaginary line.

[0012] (7) The current detection device according to the present invention detects the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, wherein the first phase, second phase, and third phase current line are parallel to each other and arranged at equal intervals on a straight line in cross-sectional view, and the first magnetic detection element and the second magnetic detection element are arranged on a second imaginary line that is perpendicular to the straight line and passes through a central current line located in the center of the first phase, second phase, and third phase current line.

[0013] (8) In this case, it is preferable that the first magnetic detection element and the second magnetic detection element are provided on the second virtual line with the straight line in between, the distance between the second magnetic detection element and the central current line is shorter than the distance between the first magnetic detection element and the central current line, the first detection direction of the first magnetic detection element is perpendicular to the second virtual line, and the second detection direction of the second magnetic detection element is parallel to the second virtual line.

[0014] (9) In this case, it is preferable that the second magnetic detection element is provided on the second virtual line between the first magnetic detection element and the central current line, the first detection direction of the first magnetic detection element is perpendicular to the second virtual line, and the second detection direction of the second magnetic detection element is parallel to the second virtual line. [Effects of the Invention]

[0015] (1) In the current detection device according to the present invention, the current flowing through three current lines is detected based on two magnetic detection elements provided around these current lines. Therefore, according to the present invention, the number of magnetic detection elements can be reduced compared to conventional current detection devices that provide one magnetic detection element for each current line, thereby reducing costs. Furthermore, in the current detection device according to the present invention, the relative positions and detection directions of the first and second magnetic detection elements with respect to the first to third phase current lines are determined such that equation (1) above, which is a matrix operation formula equivalent to the Clarke transformation, holds true. Therefore, according to the current detection device of the present invention, by using the outputs of these two magnetic detection elements, the motor control device provided in the subsequent stage does not need to perform the Clarke transformation by calculation, thereby reducing the computational load on the motor control device.

[0016] Furthermore, according to the present invention, by determining the relative positions and detection directions of the first and second magnetic detection elements with respect to the first to third phase current lines such that equation (1) above holds true, the magnetic fields of multiple phases, which would otherwise be noise in conventional current detection devices that provide a magnetic detection element for each phase current line, can be used as a significant signal. For this reason, conventional current detection devices can eliminate the need for measures to suppress such noise, such as installing a magnetic core or using the differential output of multiple elements.

[0017] In conventional current detection devices, where a magnetic detection element is provided for each current line of each phase, the relationship between the output of each magnetic detection element (V1, V2, V3) and the current values ​​of each phase (I1, I2, I3) is generally expressed by equation (2) below, using an off-diagonal matrix of current-sensor influence coefficients (a11, a12, ..., a33). For this reason, in conventional current detection devices, it is necessary to take measures to prevent interference between multiple phase magnetic fields so that the influence coefficients of the off-diagonal components become zero, or to obtain the current values ​​of each phase by multiplying the output of the magnetic detection element by the inverse matrix. In contrast, according to the present invention, such measures are unnecessary.

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[0018] (2) According to the present invention, for three current lines arranged at the vertices of an isosceles triangle in cross-sectional view, a first virtual line is defined that passes through the midpoint between the vertex angle and the base of the isosceles triangle, and the first and second magnetic detection elements are placed on this first virtual line, thereby obtaining an output equivalent to the two-phase current after Clark transformation as described above.

[0019] (3) According to the present invention, for three current lines arranged at equal intervals on a straight line in a cross-sectional view, a second virtual line is defined that is perpendicular to this straight line and passes through the central current line, and the first and second magnetic detection elements are placed on this second virtual line, thereby obtaining an output equivalent to the two-phase current after Clark transformation as described above.

[0020] (4) In the current detection device according to the present invention, currents flowing through three current lines are detected based on two magnetic detection elements provided around these current lines. Therefore, according to the present invention, the number of magnetic detection elements can be reduced compared to a conventional current detection device in which one magnetic detection element is provided for each one current line, and thus costs can be reduced accordingly. Further, in the current detection device according to the present invention, for three current lines arranged at vertices of an isosceles triangle in cross-sectional view, a first imaginary line passing through the vertex of the isosceles triangle and the midpoint of the base is defined, and by arranging the first and second magnetic detection elements on this first imaginary line, outputs equivalent to the two-phase currents after the Clark transformation shown in the above formula (1) can be obtained from the first and second magnetic detection elements. Therefore, according to the current detection device of the present invention, by using the outputs of these two magnetic detection elements, the motor control device provided at the subsequent stage does not need to perform Clark transformation by calculation, and thus the calculation load of the motor control device can be reduced accordingly.

[0021] (5) According to the present invention, the distance between the vertex and the midpoint of the isosceles triangle is made equal to the length of the base, the first magnetic detection element is provided inside the isosceles triangle, the second magnetic detection element is provided outside the isosceles triangle, the first detection direction of the first magnetic detection element is made orthogonal to the first imaginary line, and the second detection direction of the second magnetic detection element is made parallel to the first imaginary line. Thereby, an output equivalent to the two-phase currents after Clark transformation can be obtained.

[0022] (6) According to the present invention, the distance between the vertex and the midpoint of the isosceles triangle is made equal to the length of the base, both the first and second magnetic detection elements are provided inside the isosceles triangle, the second magnetic detection element is provided between the first magnetic detection element and the midpoint, the first detection direction of the first magnetic detection element is made orthogonal to the first imaginary line, and the second detection direction of the second magnetic detection element is made parallel to the first imaginary line. Thereby, an output equivalent to the two-phase currents after Clark transformation can be obtained.

[0023] (7) In the current detection device according to the present invention, currents flowing through three current lines are detected based on two magnetic detection elements provided around these current lines. Therefore, according to the present invention, the number of magnetic detection elements can be reduced compared to a conventional current detection device in which one magnetic detection element is provided for each current line, so that the cost can be reduced accordingly. Further, in the current detection device according to the present invention, for three current lines arranged at equal intervals on a straight line in cross-sectional view, a second imaginary line that is orthogonal to the straight line and passes through the central current line is defined, and the first and second magnetic detection elements are arranged on the second imaginary line, whereby an output equivalent to the two-phase current after Clark transformation shown in the above formula (1) can be obtained from the first and second magnetic detection elements. Therefore, according to the current detection device of the present invention, by using the outputs of these two magnetic detection elements, the motor control device provided at the subsequent stage does not need to perform Clark transformation by calculation, so the calculation load of the motor control device can be reduced accordingly.

[0024] (8) According to the present invention, the first and second magnetic detection elements are provided with the straight line interposed therebetween, the distance between the second magnetic detection element and the central current line is made shorter than the distance between the first magnetic detection element and the central current line, the first detection direction of the first magnetic detection element is made orthogonal to the second imaginary line, and further the second detection direction of the second magnetic detection element is made parallel to the second imaginary line. Thereby, an output equivalent to the two-phase current after Clark transformation can be obtained.

[0025] (9) According to the present invention, the second magnetic detection element is provided between the first magnetic detection element and the central current line on the second imaginary line, the first detection direction of the first magnetic detection element is made orthogonal to the second imaginary line, and further the second detection direction of the second magnetic detection element is made parallel to the second imaginary line. Thereby, an output equivalent to the two-phase current after Clark transformation can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [Figure 1] It is a diagram showing a configuration of a current detection device according to an embodiment of the present invention and an electric vehicle including the current detection device. [Figure 2] It is a diagram showing a first setting example. [Figure 3] This figure shows a second example of the settings. [Figure 4] This figure shows a third example of the settings. [Figure 5] This figure shows the fourth example setting. [Modes for carrying out the invention]

[0027] Hereinafter, a current detection device according to one embodiment of the present invention and an electric vehicle equipped with this current detection device will be described with reference to the drawings.

[0028] Figure 1 shows the configuration of the current detection device 3 and the electric vehicle V equipped with this current detection device according to this embodiment. The following description will focus on the case where the current detection device 3 is mounted on the electric vehicle V, but the present invention is not limited to this. The current detection device 3 can be mounted on anything that controls a three-phase motor based on vector control, such as air conditioners and washing machines, in addition to the electric vehicle V.

[0029] The electric vehicle V comprises a three-phase AC motor M (hereinafter simply referred to as "motor M"), drive wheels W connected to the output shaft of the motor M via a power transmission mechanism (not shown), an inverter 1 connecting a battery (not shown) to the motor M, a current detection device 3 for detecting the current of the motor M, a resolver 4 for detecting the rotational position of the motor M, and a motor control device 2 for controlling the inverter 1 based on the detection signals from the current detection device 3 and the resolver 4.

[0030] Inverter 1 is a pulse-width modulation (PWM) inverter equipped with a bridge circuit formed by bridging multiple switching elements (e.g., IGBTs), and has the function of converting DC power to AC power. Inverter 1 is connected to a battery on its DC input / output side and to the U-phase, V-phase, and W-phase coils of motor M on its AC input / output side, and converts power between the battery and motor M. Inverter 1 drives the switching elements of each phase on / off according to gate drive signals generated at predetermined timings from a gate drive circuit (not shown), thereby converting DC power supplied from the battery to AC power and supplying it to motor M, and converting AC power supplied from motor M to DC power and supplying it to the battery.

[0031] The motor control device 2 generates a command signal for the inverter 1 by performing vector control based on detection signals from the current detection device 3 and the resolver 4, and inputs it to the gate drive circuit. More specifically, the motor control device 2 calculates the d-axis current Id and the q-axis current Iq by performing calculations using the detection signals from the current detection device 3 and the resolver 4, and obtains the d-axis current command Idc and the q-axis current command Iqc according to the driving force requested by the driver. By performing feedback control based on the deviation of these current values ​​(Idc-Id, Iqc-Iq), it generates a command signal according to the driving force requested by the driver. As will be explained below, the output value of the current detection device 3 is proportional to the two-phase current (Iα, Iβ) obtained by performing a Clarke transform on the three-phase current (Iu, Iv, Iw) of the motor M. Therefore, the motor control device 2 does not need to perform a Clarke transform when calculating the two-phase current (Id, Iq) in the dq coordinate system, and thus the computational load on the motor control device 2 can be reduced compared to conventional systems.

[0032] The current detection device 3 includes a first magnetic detection element S1 and a second magnetic detection element S2, which are provided around the three phase current lines connecting the motor M and the inverter 1. The current detection device 3 detects the current flowing through the three phase current lines based on these magnetic detection elements S1 and S2. More specifically, the magnetic detection elements S1 and S2 are coreless current sensors that output detection signals corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each phase current line, along each detection direction. Therefore, the output values ​​of the magnetic detection elements S1 and S2 change according to the relative position of the magnetic detection elements S1 and S2 with respect to the three phase current lines and the orientation of the detection direction.

[0033] Therefore, in the current detection device 3, if the current value flowing through the U-phase current line as the first phase current line is Iu, the current value flowing through the V-phase current line as the second phase current line is Iv, the current value flowing through the W-phase current line as the third phase current line is Iw, the output value of the first magnetic detection element S1 is V1, and the output value of the second magnetic detection element S2 is V2, then the relative positions and detection directions of the magnetic detection elements S1 and S2 with respect to these three phase current lines are determined such that the following equation (3), which is equivalent to the Clark transformation equation that converts three-phase current (Iu, Iv, Iw) to two-phase current (Iα, Iβ), holds true.

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[0034] Below, we will explain several examples of setting the relative positions and detection directions of the magnetic detection elements S1 and S2 with respect to the three phase current lines, such that equation (3) above holds true, with reference to Figures 2 to 5.

[0035] Figure 2 shows the first example of the setup. More specifically, Figure 2 shows the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w, which are arranged parallel to each other, viewed along a cross section perpendicular to their respective extension directions. In Figures 2 to 5, the direction of each current line 6u, 6v, and 6w is indicated by an "X" mark where positive current flows from the front to the back of the page, and by a black circle mark where positive current flows from the back to the front of the page.

[0036] As shown in Figure 2, in the first example setting, the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w are arranged parallel to each other and at the corners of an isosceles triangle in cross-sectional view. The lengths of the two equal sides of this isosceles triangle are set so that the distance between the vertex angle and the midpoint P1 of the base is equal to the length of the base. In the following, the length of the base is assumed to be 2L. In the following, the case in which the U-phase current line 6u is placed at the vertex angle and the V-phase current line 6v and W-phase current line 6w are placed at the two base angles is described, but the present invention is not limited to this. The positions of each current line 6u, 6v, and 6w may be swapped as appropriate. In the following, the case in which the direction of each current line 6u, 6v, and 6w is set so that the positive current flows from the front to the back of the page is described, but the present invention is not limited to this. The direction of each current line 6u, 6v, and 6w may be set so that the positive current flows from the back to the front of the page.

[0037] As shown in Figure 2, when the phase current lines 6u, 6v, and 6w are placed at the three angles of an isosceles triangle, the first magnetic detection element S1 and the second magnetic detection element S2 are each placed on a first imaginary line L1 that passes through the vertex angle and the midpoint P1 of the base. In the first example setting, the first magnetic detection element S1 is placed on the first imaginary line L1, closer to the vertex angle than the midpoint P1 (i.e., inside the isosceles triangle), more specifically, at a position midway between the midpoint P1 and the vertex angle. That is, the distance between the first magnetic detection element S1 and the vertex angle, and the distance between the first magnetic detection element S1 and the midpoint P1 are both L. In the first example setting, the second magnetic detection element S2 is placed on the first imaginary line L1, on the opposite side of the vertex angle from the midpoint P1 (i.e., outside the isosceles triangle). As shown in Figure 2, the second magnetic detection element S2 is placed closer to the midpoint P1 than the first magnetic detection element S1. More specifically, if the distance between the first magnetic detection element S1 and the midpoint P1 is L, the distance LS2 between the second magnetic detection element S2 and the midpoint P1 is set such that the following equation (4) holds true.

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[0038] As shown in Figure 2, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the first virtual line L1, and the second detection direction D2 of the second magnetic detection element S2 is parallel to the second virtual line L2. More specifically, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the first virtual line L1 and directed toward the V-phase current line 6v. The second detection direction D2 of the second magnetic detection element S2 is perpendicular to the magnetic field formed by the current flowing through the U-phase current line 6u, which is positioned at the apex angle, and more specifically, it is parallel to the first virtual line L1 and directed toward the opposite side of the midpoint P1.

[0039] According to the first example setting described above, the first magnetic detection element S1 detects the superposition of magnetic fields generated by the currents flowing through the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w, and the second magnetic detection element S2 detects the superposition of magnetic fields generated by the currents flowing through the V-phase current line 6v and the W-phase current line 6w. Therefore, the output values ​​V1 and V2 of the magnetic detection elements S1 and S2 satisfy equation (3) above.

[0040] Figure 3 shows a second example of the configuration. More specifically, Figure 3 shows the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w, which are arranged parallel to each other, viewed along a cross section perpendicular to their respective extension directions.

[0041] The arrangement of the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w is the same as in the first setting example explained with reference to Figure 2, so a detailed explanation will be omitted.

[0042] As shown in Figure 3, when the phase current lines 6u, 6v, and 6w are placed at the three angles of an isosceles triangle, the first magnetic detection element S1 and the second magnetic detection element S2 are placed on a first imaginary line L1 that passes through the vertex angle and the midpoint P1 of the base, respectively. In the second setting example, both the first magnetic detection element S1 and the second magnetic detection element S2 are placed on the first imaginary line L1, closer to the vertex angle than the midpoint P1 (i.e., inside the isosceles triangle). More specifically, the first magnetic detection element S1 is placed at an intermediate position between the midpoint P1 and the vertex angle. That is, the distance between the first magnetic detection element S1 and the vertex angle, and the distance between the first magnetic detection element S1 and the midpoint P1 are both L. In the second setting example, the second magnetic detection element S2 is placed on the first imaginary line L1, between the midpoint P1 and the first magnetic detection element S1. Furthermore, as shown in Figure 3, the second magnetic detection element S2 is positioned closer to the midpoint P1 than the first magnetic detection element S1. More specifically, if the distance between the first magnetic detection element S1 and the midpoint P1 is L, the distance LS2 between the second magnetic detection element S2 and the midpoint P1 is set such that equation (4) above holds true.

[0043] As shown in Figure 3, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the first virtual line L1, and the second detection direction D2 of the second magnetic detection element S2 is parallel to the second virtual line L2. More specifically, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the first virtual line L1 and directed toward the V-phase current line 6v. The second detection direction D2 of the second magnetic detection element S2 is perpendicular to the magnetic field formed by the current flowing through the U-phase current line 6u, which is positioned at the apex angle, and more specifically, it is parallel to the first virtual line L1 and directed toward the midpoint P1.

[0044] According to the second example setting described above, the first magnetic detection element S1 detects the superposition of magnetic fields generated by the currents flowing through the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w, and the second magnetic detection element S2 detects the superposition of magnetic fields generated by the currents flowing through the V-phase current line 6v and the W-phase current line 6w. Therefore, the output values ​​V1 and V2 of the magnetic detection elements S1 and S2 satisfy equation (3) above.

[0045] Figure 4 shows a third example of the configuration. More specifically, Figure 4 shows the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w, which are arranged parallel to each other, viewed along a cross section perpendicular to their respective extension directions.

[0046] As shown in Figure 4, in the third configuration example, the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w are arranged parallel to each other and at equal intervals on a straight line L3 in cross-sectional view. In the following, the length between adjacent phase current lines, i.e., in the example of Figure 4, the length between the U-phase current line 6u and the V-phase current line 6v, and the length between the U-phase current line 6u and the W-phase current line 6w, will both be L. In the following, we will describe the case in which the U-phase current line 6u is placed in the center of the straight line L3, the V-phase current line 6v is placed to the right of the U-phase current line 6u in Figure 4 on the straight line L3, and the W-phase current line 6w is placed to the left of the U-phase current line 6u in Figure 4 on the straight line L3, but the present invention is not limited to this. The positions of each current line 6u, 6v, and 6w may be swapped as appropriate. In the following, when the three phase current lines are arranged on a straight line L3 in cross-sectional view, the current line placed in the center will also be called the central current line. That is, in the example of Figure 4, the U-phase current line 6u is the central current line.

[0047] Furthermore, the following description will explain the case where, of the three current lines, the two lines excluding the central current line are oriented so that the positive current flows from the front to the back of the page, and the central current line is oriented so that the positive current flows from the back to the front of the page; however, the present invention is not limited to this. The two lines excluding the central current line of the three current lines may be oriented so that the positive current flows from the back to the front of the page, and the central current line may be oriented so that the positive current flows from the front to the back of the page.

[0048] As shown in Figure 4, when the phase current lines 6u, 6v, and 6w are arranged at equal intervals on a straight line L3, the first magnetic detection element S1 and the second magnetic detection element S2 are each positioned on a second virtual line L2 that is perpendicular to the straight line L3 and passes through the central current line 6u. In the third setting example, the first magnetic detection element S1 and the second magnetic detection element S2 are provided on the second virtual line L2, with the straight line L3 in between. In the third setting example, the first magnetic detection element S1 is positioned above the straight line L3 in Figure 4, and the second magnetic detection element S2 is positioned below the straight line L3 in Figure 4. More specifically, the first magnetic detection element S1 is installed on the second virtual line L2 at a distance L from the central current line 6u. That is, the distance between the first magnetic detection element S1 and the central current line 6u is equal to the distance between the central current line 6u and the left and right current lines 6v and 6w. Furthermore, the second magnetic detection element S2 is positioned closer to the central current line 6u than the first magnetic detection element S1. That is, the distance between the second magnetic detection element S2 and the central current line 6u is shorter than the distance between the first magnetic detection element S1 and the central current line 6u. More specifically, if the distance between the first magnetic detection element S1 and the central current line 6u is L, the distance LS2 between the second magnetic detection element S2 and the central current line 6u is set such that equation (4) above holds true.

[0049] As shown in Figure 4, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the second virtual line L2, and the second detection direction D2 of the second magnetic detection element S2 is parallel to the second virtual line L2. More specifically, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the second virtual line L2 and directed toward the V-phase current line 6v side. The second detection direction D2 of the second magnetic detection element S2 is perpendicular to the magnetic field formed by the current flowing through the central current line 6u, more specifically, it is parallel to the second virtual line L2 and directed toward the opposite side of the central current line 6u.

[0050] According to the third example setting described above, the first magnetic detection element S1 detects the superposition of magnetic fields generated by the currents flowing through the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w, and the second magnetic detection element S2 detects the superposition of magnetic fields generated by the currents flowing through the V-phase current line 6v and the W-phase current line 6w. Therefore, the output values ​​V1 and V2 of the magnetic detection elements S1 and S2 satisfy equation (3) above.

[0051] Figure 5 shows a fourth example of the configuration. More specifically, Figure 5 shows the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w, which are arranged parallel to each other, viewed along a cross section perpendicular to their respective extension directions.

[0052] The arrangement of the U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w is the same as in the third setting example explained with reference to Figure 4, so a detailed explanation will be omitted.

[0053] As shown in Figure 4, when the phase current lines 6u, 6v, and 6w are arranged at equal intervals on a straight line L3, the first magnetic detection element S1 and the second magnetic detection element S2 are each positioned on a second virtual line L2 that is perpendicular to the straight line L3 and passes through the central current line 6u. In the fourth setting example, the second magnetic detection element S2 is provided on the second virtual line L2 between the first magnetic detection element S1 and the central current line 6u. In the third setting example, the first magnetic detection element S1 and the second magnetic detection element S2 are positioned above the straight line L3 in Figure 4. More specifically, the first magnetic detection element S1 is installed on the second virtual line L2 at a distance L from the central current line 6u. That is, the distance between the first magnetic detection element S1 and the central current line 6u is equal to the distance between the central current line 6u and the left and right current lines 6v and 6w. The second magnetic detection element S2 is positioned closer to the central current line 6u than the first magnetic detection element S1. In other words, the distance between the second magnetic detection element S2 and the central current line 6u is shorter than the distance between the first magnetic detection element S1 and the central current line 6u. More specifically, if the distance between the first magnetic detection element S1 and the central current line 6u is L, the distance LS2 between the second magnetic detection element S2 and the central current line 6u is set such that equation (4) above holds true.

[0054] As shown in Figure 5, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the second virtual line L2, and the second detection direction D2 of the second magnetic detection element S2 is parallel to the second virtual line L2. More specifically, the first detection direction D1 of the first magnetic detection element S1 is perpendicular to the second virtual line L2 and directed toward the V-phase current line 6v. The second detection direction D2 of the second magnetic detection element S2 is perpendicular to the magnetic field formed by the current flowing through the central current line 6u, more specifically, it is parallel to the second virtual line L2 and directed toward the central current line 6u.

[0055] According to the fourth setting example described above, the first magnetic detection element S1 detects the superposition of magnetic fields generated by the currents flowing through the U-phase current line 6u, the V-phase current line 6v, and the W-phase current line 6w, and the second magnetic detection element S2 detects the superposition of magnetic fields generated by the currents flowing through the V-phase current line 6v and the W-phase current line 6w. Therefore, the output values ​​V1 and V2 of the magnetic detection elements S1 and S2 satisfy equation (3) above.

[0056] The current detection device 3 according to this embodiment provides the following effects. In the current detection device 3, the currents flowing through the three current lines 6u, 6v, and 6w are detected based on two magnetic detection elements S1 and S2 placed around these current lines 6u, 6v, and 6w. Therefore, the current detection device 3 reduces the number of magnetic detection elements compared to conventional current detection devices that have one magnetic detection element for each current line, thereby reducing costs. In addition, in the current detection device 3, the relative positions and detection directions of the magnetic detection elements S1 and S2 with respect to each current line 6u, 6v, and 6w are determined such that equation (3) above, which is a matrix operation equivalent to the Clarke transformation, holds true. Therefore, in the current detection device 3, by using the outputs of these two magnetic detection elements S1 and S2, the motor control device 2 installed in the subsequent stage does not need to perform the Clarke transformation by calculation, thereby reducing the computational load on the motor control device 2.

[0057] Furthermore, according to the current detection device 3 of this embodiment, measures such as multi-phase magnetic field interference countermeasures and inverse matrix multiplication, which were necessary in conventional current detection devices that detect the current value of each phase based on the above equation (2), become unnecessary.

[0058] Although one embodiment of the present invention has been described above, the present invention is not limited thereto. Within the scope of the spirit of the present invention, the details of the configuration may be modified as appropriate. [Explanation of Symbols]

[0059] V...vehicle W…Drive wheels M...Motor (three-phase motor) 6u…U phase current line 6v…V phase current line 6w…W phase current line 1…Inverter 2…Motor control device 3…Current detection device S1...First magnetic detection element D1...First detection direction S2...Second magnetic detection element D2...Second detection direction 4…Resolver

Claims

1. A current detection device for detecting the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, A current detection device characterized in that, when the current value flowing through the first phase current line is I1, the current value flowing through the second phase current line is I2, the current value flowing through the third phase current line is I3, the output value of the first magnetic detection element is V1, and the output value of the second magnetic detection element is V2, the relative positions of the first and second magnetic detection elements with respect to the first, second, and third phase current lines and the orientation of the detection direction are determined such that the following equation (1) holds true. [Math 1]

2. The first, second, and third phase current lines are parallel to each other and arranged at the corners of an isosceles triangle in cross-sectional view. The current detection device according to claim 1, characterized in that the first magnetic detection element and the second magnetic detection element are each arranged on a first imaginary line passing through the vertex angle and the midpoint of the base of the isosceles triangle.

3. The first, second, and third phase current lines are arranged parallel to each other and at equal intervals in a straight line when viewed in cross-section. The current detection device according to claim 1, characterized in that the first magnetic detection element and the second magnetic detection element are arranged on a second imaginary line that is perpendicular to the straight line and passes through a central current line which is located in the center of the first phase, second phase, and third phase current lines.

4. A current detection device for detecting the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, The first, second, and third phase current lines are parallel to each other and arranged at the corners of an isosceles triangle in cross-sectional view. The current detection device is characterized in that the first magnetic detection element and the second magnetic detection element are each arranged on a first imaginary line passing through the vertex angle and the midpoint of the base of the isosceles triangle.

5. The distance between the vertex angle and the midpoint is equal to the length of the base. The first magnetic detection element is provided on the first virtual line, on the side of the apex angle that is closer to the midpoint than the midpoint, The second magnetic detection element is provided on the first dashed line on the side opposite to the vertex angle from the midpoint, The first detection direction of the first magnetic detection element is perpendicular to the first virtual line, The current detection device according to claim 2 or 4, characterized in that the second detection direction of the second magnetic detection element is parallel to the first virtual line.

6. The distance between the vertex angle and the midpoint is equal to the length of the base. The first magnetic detection element is provided on the first virtual line, on the side of the apex angle that is closer to the midpoint than the midpoint, The second magnetic detection element is provided on the first dashed line between the midpoint and the first magnetic detection element, The first detection direction of the first magnetic detection element is perpendicular to the first virtual line, The current detection device according to claim 2 or 4, characterized in that the second detection direction of the second magnetic detection element is parallel to the first virtual line.

7. A current detection device for detecting the current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor based on a first magnetic detection element and a second magnetic detection element provided around the first phase, second phase, and third phase current line, The first, second, and third phase current lines are arranged parallel to each other and at equal intervals in a straight line when viewed in cross-section. The current detection device is characterized in that the first magnetic detection element and the second magnetic detection element are arranged on a second virtual line that is perpendicular to the straight line and passes through a central current line which is located in the center of the first phase, second phase, and third phase current lines.

8. The first magnetic detection element and the second magnetic detection element are provided on the second virtual line, with the straight line in between them. The distance between the second magnetic detection element and the central current line is shorter than the distance between the first magnetic detection element and the central current line. The first detection direction of the first magnetic detection element is perpendicular to the second virtual line, The current detection device according to claim 3 or 7, characterized in that the second detection direction of the second magnetic detection element is parallel to the second virtual line.

9. The second magnetic detection element is provided on the second virtual line between the first magnetic detection element and the central current line, The first detection direction of the first magnetic detection element is perpendicular to the second virtual line, The current detection device according to claim 3 or 7, characterized in that the second detection direction of the second magnetic detection element is parallel to the second virtual line.

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