Current Detector

Abstract

To provide a current detection device for three-phase motors with which it is possible to reduce a computation load in a motor control device in the subsequent stage that performs vector control.SOLUTION: A current detection device detects currents flowing in the U-phase current line 5u, V-phase current line 5v and W-phase current line 5w of a three-phase motor on the basis of a α-axis magnetism detection element Sα and a β-axis magnetism detection element Sβ provided in the periphery of these phase current lines 5u, 5v, 5w. These current lines 5u, 5v, 5w are parallel to each other and arranged at corners of an isosceles triangle in a cross sectional view, the output sensitivity of the β-axis magnetism detection element Sβ is larger than the α-axis magnetism detection element Sα, and the magnetism detection elements Sα, Sβ are arranged so that the respective center positions match on a first virtual line L1 passing through the apex angle of the isosceles triangle and a middle point P1 at the bottom and the detection axes of the magnetism detection elements Sα, Sβ cross at right angles. The distance between the apex angle and the middle point P1 is equal to the length of the bottom, and the center position of the magnetism detection elements Sα, Sβ is located in the inside of the isosceles triangle.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and vehicles are also becoming more susceptible to CO 2 Research and development into electric vehicles is ongoing to reduce emissions and improve energy efficiency.

[0003] So-called vector control is widely used as a control method for three-phase AC motors mounted on electric vehicles, home appliances (e.g., air conditioners, washing machines, etc.), etc. 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 dq coordinates, which are a rotational orthogonal coordinate system of the motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 058282 Summary of the Invention [Problem to be solved by the invention]

[0005] In this way, in the motor control device, in order to perform feedback control of the current on the dq coordinates, it is necessary to convert the U-phase current, V-phase current, and W-phase current of the motor detected by a current detection device such as that shown in Patent Document 1, into d-axis current and q-axis current. More specifically, in the motor control device, the three-phase current (Iu, Iv, Iw) detected by the current detection device is first converted by Clarke transformation into two-phase current (Iα, Iβ) defined in a fixed coordinate system, and then the two-phase current (Iα, Iβ) is converted by Park transformation using the rotation angle θ of the motor into two-phase current (Id, Iq) defined in the dq coordinate system. In this way, in the vector control using the output of the conventional current detection device, it is necessary to execute a calculation in the motor control device to convert the three-phase current (Iu, Iv, Iw) into the two-phase current (Id, Iq).

[0006] An object of the present invention is to provide a current detection device for a three-phase motor that can reduce the calculation load in a downstream motor control device that performs vector control, and ultimately to contribute to improving energy efficiency. [Means for solving the problem]

[0007] (1) A current detection device (e.g., a current detection device 3, 3' described later) according to the present invention detects currents flowing through a first phase current line (e.g., a U-phase current line 5u described later), a second phase current line (e.g., a V-phase current line 5v described later), and a third phase current line (e.g., a W-phase current line 5w described later) of a three-phase motor (e.g., a motor M described later) based on an α-axis magnetic detection element (e.g., an α-axis magnetic detection element Sα, Sα' described later) and a β-axis magnetic detection element (e.g., a β-axis magnetic detection element Sβ, Sβ' described later) provided around the first, second, and third phase current lines, and the α-axis and β-axis magnetic detection elements The center positions of the output elements are aligned, the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, and 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 α-axis magnetic detection element is Vα, and the output value of the β-axis magnetic detection element is Vβ, the relative positions of the α-axis and β-axis magnetic detection elements with respect to the first phase, second phase, and third phase current lines and the orientations of the detection axes (for example, the α-axis Oα and β-axis Oβ described below) are determined so that the following formula (1) is established.

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[0008] (2) A current detection device according to the present invention (for example, a current detection device 3 or 3' described later) detects currents flowing through a first phase current line (for example, a U-phase current line 5u described later), a second phase current line (for example, a V-phase current line 5v described later), and a third phase current line (for example, a W-phase current line 5w described later) of a three-phase motor (for example, a motor M described later) by detecting the currents flowing through an α-axis magnetic detection element (for example, an α-axis magnetic detection element Sα or Sα' described later) and a β-axis magnetic detection element (for example, a β-axis magnetic detection element Sα or Sα' described later) provided around the first phase, second phase, and third phase current lines. The first-phase, second-phase, and third-phase current lines are arranged in parallel to one another and at the corners of an isosceles triangle in a cross-sectional view, the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, and the α-axis and β-axis magnetic detection elements are arranged such that their respective central positions coincide on a first virtual line (e.g., a first virtual line L1 described later) passing through the apex angle and the midpoint of the base of the isosceles triangle (e.g., a midpoint P1 described later).

[0009] (3) In this case, it is preferable that the distance between the apex angle and the midpoint is equal to the length of the base, the center positions of the α-axis and β-axis magnetic detection elements are located on the apex angle side of the midpoint on the first virtual line, the α-axis (e.g., the α-axis Oα described below) which is the detection axis of the α-axis magnetic detection element is perpendicular to the first virtual line, and the β-axis (e.g., the β-axis Oβ described below) which is the detection axis of the β-axis magnetic detection element is parallel to the first virtual line.

[0010] (4) A current detection device (e.g., a current detection device 3, 3' described later) according to the present invention detects currents flowing through a first phase current line (e.g., a U-phase current line 5u described later), a second phase current line (e.g., a V-phase current line 5v described later), and a third phase current line (e.g., a W-phase current line 5w described later) of a three-phase motor (e.g., a motor M described later) based on an α-axis magnetic detection element (e.g., an α-axis magnetic detection element Sα, Sα' described later) and a β-axis magnetic detection element (e.g., a β-axis magnetic detection element Sβ, Sβ' described later) provided around the first phase, second phase, and third phase current lines. the first-phase, second-phase, and third-phase current lines are parallel to one another and are equally spaced apart on a straight line (e.g., a straight line L3 described later) in a cross-sectional view, the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, and the α-axis and β-axis magnetic detection elements are arranged so that their respective central positions coincide on a second virtual line (e.g., a second virtual line L2 described later) that is perpendicular to the straight line and passes through a central current line (e.g., a U-phase current line 5u described later) that is located in the center among the first-phase, second-phase, and third-phase current lines.

[0011] (5) In this case, it is preferable that the α-axis (e.g., the α-axis Oα described below), which is the detection axis of the α-axis magnetic detection element, is perpendicular to the second virtual line, and the β-axis (e.g., the β-axis Oβ described below), which is the detection axis of the β-axis magnetic detection element, is parallel to the second virtual line.

[0012] (6) In this case, it is preferable that the distance between the center positions of the α-axis and β-axis magnetic detection elements and the second and third phase current lines is two times larger than the distance between the center positions and the first phase current line, and the output sensitivity of the β-axis magnetic detection element is three times larger than the output sensitivity of the α-axis magnetic detection element.

[0013] (7) In this case, the α-axis and β-axis magnetic detection elements each include a coil (e.g., the α-axis coil 61 and the β-axis coil 71 described below) wound in a ring shape when viewed along the respective detection axes, and it is preferable that the α-axis and β-axis magnetic detection elements differ in any one or more of the linkage area of ​​the coil, the thickness of the wire of the coil, the material of the wire, the number of turns of the wire, the length of the wire, the presence or absence of a core, the material of the core, the shape of the core, and the cross-sectional area of ​​the core.

[0014] (8) In this case, the α-axis magnetic detection element has an α-axis coil (e.g., the α-axis coil 61 described later) wound in a circular shape when viewed along its detection axis, which is the α-axis (e.g., the α-axis Oα described later), and the β-axis magnetic detection element has a β-axis coil (e.g., the β-axis coil 71 described later) wound in a circular shape when viewed along its detection axis, which is the β-axis (e.g., the β-axis Oβ described later), and it is preferable that the inner diameter of the β-axis coil is larger than the outer diameter of the α-axis coil, and that the α-axis coil is arranged inside the β-axis coil so that their respective center positions coincide and the α-axis and the β-axis are perpendicular to each other.

[0015] (9) In this case, it is preferable that the α-axis magnetic detection element comprises the α-axis coil and an α-axis support member (e.g., α-axis support member 62 described later) that is arranged inside the α-axis coil and supports at least a portion of the inner circumference of the α-axis coil (e.g., inner circumference 61a described later), and the β-axis magnetic detection element comprises the β-axis coil and a β-axis support member (e.g., β-axis support member 72 described later) that is arranged inside the β-axis coil and supports at least a portion of the inner circumference of the β-axis coil (e.g., inner circumference 71a described later) and at least a portion of the α-axis magnetic detection element.

[0016] (10) In this case, it is preferable that the α-axis magnetic detection element includes a first α-axis coil (e.g., the first α-axis coil 81 described later) and a second α-axis coil (e.g., the second α-axis coil 84 described later) wound in a circular shape and arranged parallel to each other when viewed along the α-axis (e.g., the α-axis Oα described later) which is its detection axis, and the β-axis magnetic detection element includes a first β-axis coil (e.g., the first β-axis coil 91 described later) and a second β-axis coil (e.g., the second β-axis coil 95 described later) wound in a circular shape and arranged parallel to each other when viewed along the β-axis (e.g., the β-axis Oβ described later) which is its detection axis, and the second α-axis coil is oriented in a counter-rotating direction relative to the first α-axis coil when viewed along the α-axis, and the second β-axis coil is oriented in a counter-rotating direction relative to the first β-axis coil when viewed along the β-axis.

[0017] (11) In this case, it is preferable that the inner diameters of the first and second β-axis coils are larger than the outer diameters of the first and second α-axis coils, the first and second α-axis coils are arranged inside the first and second β-axis coils so that the α-axis and the β-axis are perpendicular to each other, the first and second α-axis coils are arranged parallel to each other across an intersection of the α-axis and the β-axis, and the first and second β-axis coils are arranged parallel to each other across the intersection.

[0018] (12) In this case, the α-axis magnetic detection element includes the first and second α-axis coils, a first α-axis support member (e.g., first α-axis support member 82 described later) that is provided inside the first α-axis coil and supports at least a portion of the inner periphery of the first α-axis coil (e.g., inner periphery 81a described later), and a second α-axis support member (e.g., second α-axis support member 85 described later) that is provided inside the second α-axis coil and supports at least a portion of the inner periphery of the second α-axis coil (e.g., inner periphery 84a described later), and the β-axis magnetic detection element includes the first and It is preferable that the coil assembly comprises a second β-axis coil, a first β-axis support member (e.g., first β-axis support member 92 described later) that is provided inside the first β-axis coil and supports at least a portion of the inner periphery of the first β-axis coil (e.g., inner periphery 91a described later) and at least a portion of the α-axis magnetic detection element, and a second β-axis support member (e.g., second β-axis support member 96 described later) that is provided inside the second β-axis coil and supports at least a portion of the inner periphery of the second β-axis coil (e.g., inner periphery 95a described later) and at least a portion of the α-axis magnetic detection element. Effect of the Invention

[0019] (1) In the current detection device according to the present invention, the current flowing through the 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 a conventional current detection device in which one magnetic detection element is provided for each current line, and the cost can be reduced accordingly. In addition, in the current detection device according to the present invention, the relative positions of the α-axis and β-axis magnetic detection elements with respect to the first to third phase current lines and the directions of the detection axes are determined so that the above formula (1), which is a matrix calculation formula equivalent to the Clarke transformation, holds. 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 Clarke transformation by calculation, and the calculation load of the motor control device can be reduced accordingly. In addition, according to the present invention, the calculation load of the motor control device can be reduced, thereby improving the energy efficiency of the entire system including the current detection device and the motor control device.

[0020] Furthermore, according to the present invention, by determining the relative positions and detection axis directions of the α-axis and β-axis magnetic detection elements with respect to the first to third phase current lines so that the above formula (1) is established, it is possible to utilize, as a significant signal, magnetic fields of multiple phases that would be noise in a conventional current detection device in which a magnetic detection element is provided for each current line of each phase. Therefore, it is possible to eliminate the need for measures against multiple phase magnetic field interference that were necessary in conventional current detection devices to suppress the above-mentioned noise.

[0021] In a conventional current detection device in which a magnetic detection element is provided for each current line of each phase, the relational expression between the output of each magnetic detection element (V1, V2, V3) and the current value of each phase (I1, I2, I3) is generally expressed by the following formula (2) using a non-diagonal matrix of current-sensor influence coefficients (a11, a12, ..., a33). For this reason, in a conventional current detection device, it is necessary to take measures against multi-phase magnetic field interference so that the influence coefficient of the non-diagonal components becomes 0, or to obtain the current value of each phase by multiplying the output of the magnetic detection element by an inverse matrix. In contrast, according to the present invention, such measures are unnecessary.

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[0022] According to the present invention, the α-axis and β-axis magnetic detection elements can be integrated by aligning the central positions of the α-axis and β-axis magnetic detection elements, thereby reducing the space occupied by the magnetic detection elements and facilitating the alignment of the magnetic detection elements with the first to third phase current lines. According to the present invention, the α-axis and β-axis magnetic detection elements can be aligned in central positions and the output sensitivity of the β-axis magnetic detection element can be made higher than the output sensitivity of the α-axis magnetic detection element, thereby making it possible to establish the above formula (1) while making the distances between the α-axis and β-axis magnetic detection elements and each current line equal.

[0023] (2) In the current detection device according to the present invention, the current flowing through the three current lines is detected based on two magnetic detection elements provided around the three 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, and the cost can be reduced accordingly. In addition, in the current detection device according to the present invention, a first virtual line passing through the apex and the midpoint of the base of an isosceles triangle is defined for the three current lines arranged at the apexes of the isosceles triangle in a cross-sectional view, and the α-axis and β-axis magnetic detection elements are arranged so that their respective central positions coincide on the first virtual line, thereby making it possible to integrate the α-axis and β-axis magnetic detection elements, thereby making it possible to reduce the space occupied by these magnetic detection elements and to easily align the magnetic detection elements with the first to third phase current lines. According to the present invention, by aligning the center positions of the α-axis and β-axis magnetic detection elements and making the output sensitivity of the β-axis magnetic detection element greater than that of the α-axis magnetic detection element, it is possible to obtain an output equivalent to the two-phase current after Clarke transformation shown in the above formula (1) from the α-axis and β-axis magnetic detection elements while making the distances between the α-axis and β-axis magnetic detection elements and each current line equal. 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 Clarke transformation by calculation, and the calculation load of the motor control device can be reduced accordingly. According to the present invention, by reducing the calculation load of the motor control device, it is also possible to improve the energy efficiency of the entire system including the current detection device and the motor control device.

[0024] (3) According to the present invention, the distance between the apex and the midpoint of the isosceles triangle is made equal to the length of the base, the centers of the α-axis and β-axis magnetic detection elements are located inside the isosceles triangle, the α-axis, which is the detection axis of the α-axis magnetic detection element, is made perpendicular to the first virtual line, and the β-axis, which is the detection axis of the β-axis magnetic detection element, is made parallel to the first virtual line, thereby making it possible to obtain an output equivalent to the two-phase current after Clarke transformation.

[0025] (4) In the current detection device according to the present invention, the current flowing through the three current lines is detected based on two magnetic detection elements provided around the three 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, and the cost can be reduced accordingly. In addition, in the current detection device according to the present invention, a second virtual line is defined that is perpendicular to the three current lines arranged at equal intervals on a straight line in a cross-sectional view and passes through the central current line, and the α-axis and β-axis magnetic detection elements are arranged so that their respective central positions coincide on the second virtual line, thereby integrating the α-axis and β-axis magnetic detection elements, thereby reducing the space occupied by these magnetic detection elements and facilitating the alignment of these magnetic detection elements with respect to the first to third phase current lines. According to the present invention, by aligning the center positions of the α-axis and β-axis magnetic detection elements and making the output sensitivity of the β-axis magnetic detection element greater than that of the α-axis magnetic detection element, it is possible to obtain an output equivalent to the two-phase current after Clarke transformation shown in the above formula (1) from the α-axis and β-axis magnetic detection elements while making the distances between the α-axis and β-axis magnetic detection elements and each current line equal. 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 Clarke transformation by calculation, and the calculation load of the motor control device can be reduced accordingly. According to the present invention, by reducing the calculation load of the motor control device, it is also possible to improve the energy efficiency of the entire system including the current detection device and the motor control device.

[0026] (5) According to the present invention, the α-axis, which is the detection axis of the α-axis magnetic detection element, is made perpendicular to the second virtual line, and the β-axis, which is the detection axis of the β-axis magnetic detection element, is made parallel to the second virtual line, thereby making it possible to obtain an output equivalent to the two-phase current after Clarke transformation.

[0027] (6) In the present invention, the distance between the center positions of the α-axis and β-axis magnetic detection elements and the second and third phase current lines is made two times larger than the distance between the center positions and the first phase current line, and the output sensitivity of the β-axis magnetic detection element is made three times larger than the output sensitivity of the α-axis magnetic detection element, so that an output equivalent to the two-phase current after Clarke transformation can be obtained from the α-axis and β-axis magnetic detection elements.

[0028] (7) In the present invention, the α-axis and β-axis magnetic detection elements are coils, and differences are provided between these α-axis and β-axis magnetic detection elements in one or more of the linkage area, wire thickness, wire material, number of turns of wire, wire length, presence or absence of a core, core material, core shape, and core cross-sectional area, which makes it easy to make the output sensitivity of the β-axis magnetic detection element greater than that of the α-axis magnetic detection element.

[0029] (8) In the present invention, the inner diameter of the β-axis coil of the β-axis magnetic detection element is made larger than the outer diameter of the α-axis coil of the α-axis magnetic detection element, and the α-axis coil is arranged inside the β-axis coil so that their respective center positions coincide and the α-axis and β-axis are perpendicular to each other, thereby reducing the space occupied by these magnetic detection elements.

[0030] (9) In the present invention, the shape of the α-axis coil can be maintained by supporting at least a part of the inner circumference of the α-axis coil with the α-axis support member. Also, by supporting at least a part of the inner circumference of the β-axis coil and at least a part of the α-axis magnetic detection element with the β-axis support member, the shape of the β-axis coil can be maintained while aligning the central positions of the α-axis coil and the β-axis coil. Therefore, according to the present invention, deformation and displacement of the α-axis and β-axis coils due to vibration can be prevented, and the current detection accuracy can be maintained.

[0031] (10) In the present invention, the α-axis magnetic detection element is configured with two α-axis coils that rotate in opposite directions when viewed along the α-axis, and the β-axis magnetic detection element is configured with two β-axis coils that rotate in opposite directions when viewed along the β-axis. Therefore, according to the present invention, by utilizing the differential output of each coil in each magnetic detection element, it is possible to cancel common-mode noise (such as noise generated between the ground of the signal source and the ground of the measurement circuit, or noise generated when a current of another circuit flows into the ground of the measurement circuit), thereby improving the current detection accuracy.

[0032] (11) In the present invention, the inner diameters of the first and second β-axis coils are made larger than the outer diameters of the first and second α-axis coils, the first and second α-axis coils are arranged inside the first and second β-axis coils so that the α-axis and β-axis are perpendicular to each other, the first and second α-axis coils are arranged parallel to each other across an intersection of the α-axis and the β-axis, and the first and second β-axis coils are arranged parallel to each other across this intersection. This makes it possible to reduce the space occupied by the α-axis and β-axis magnetic detection elements while aligning the central positions of these magnetic detection elements.

[0033] (12) In the present invention, the first α-axis support member supports at least a part of the inner circumference of the first α-axis coil, and the second α-axis support member supports at least a part of the inner circumference of the second α-axis coil, thereby making it possible to maintain the shapes of the first and second α-axis coils. Also, the first β-axis support member supports at least a part of the inner circumference of the first β-axis coil and at least a part of the α-axis magnetic detection element, and the second β-axis support member supports at least a part of the inner circumference of the second β-axis coil and at least a part of the α-axis magnetic detection element, thereby making it possible to maintain the shapes of the first and second β-axis coils while aligning the central positions of the α-axis and β-axis magnetic detection devices. Therefore, according to the present invention, it is possible to prevent deformation and displacement of the first and second α-axis coils and the first and second β-axis coils due to vibration, thereby making it possible to maintain the detection accuracy of the current. [Brief description of the drawings]

[0034] [Figure 1]1 is a diagram showing the configuration of a current detection device according to a first embodiment of the present invention and an electric vehicle including the current detection device. [Diagram 2] FIG. 1 is a diagram showing a first layout example. [Diagram 3] FIG. 11 is a diagram showing a second layout example. [Figure 4] 2 is a perspective view showing a configuration of a two-axis magnetic detection unit of the current detection device according to the present embodiment. FIG. [Diagram 5] FIG. 11 is a perspective view showing a configuration of a two-axis magnetic detection unit of a current detection device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] First Embodiment Hereinafter, a current detection device according to a first embodiment of the present invention and an electric vehicle equipped with the current detection device will be described with reference to the drawings.

[0036] 1 is a diagram showing the configuration of a current detection device 3 according to this embodiment and an electric vehicle V equipped with this current detection device. Note that, although the following will describe a case where the current detection device 3 is mounted on an electric vehicle V, the present invention is not limited to this. In addition to the electric vehicle V, the current detection device 3 can be mounted on any device that controls a three-phase motor based on vector control, such as an air conditioner or a washing machine.

[0037] 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 and the motor M, a current detection device 3 that detects the current of the motor M, a resolver 4 that detects the rotational position of the motor M, and a motor control device 2 that controls the inverter 1 based on the detection signals of the current detection device 3 and the resolver 4.

[0038] The inverter 1 is, for example, a PWM inverter using pulse width modulation that includes a bridge circuit formed by connecting a plurality of switching elements (for example, IGBTs) in a bridge configuration, and has a function of converting DC power and AC power. The inverter 1 is connected to a battery on its DC input / output side, and to coils of U-phase, V-phase, and W-phase of the motor M on its AC input / output side, and converts power between the battery and the motor M. The inverter 1 drives the switching elements of each phase on / off in accordance with a gate drive signal generated at a predetermined timing from a gate drive circuit (not shown), thereby converting the DC power supplied from the battery into AC power and supplying it to the motor M, or converting the AC power supplied from the motor M into DC power and supplying it to the battery.

[0039] 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 the command signal 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, obtains the d-axis current command Idc and the q-axis current command Iqc according to the driving force required by the driver, and generates a command signal according to the driving force required by the driver by performing feedback control based on the deviation (Idc-Id, Iqc-Iq) of these current values. As described below, the output value of the current detection device 3 is proportional to the two-phase currents (Iα, Iβ) obtained by Clarke transforming the three-phase currents (Iu, Iv, Iw) of the motor M. Therefore, the motor control device 2 does not need to perform Clarke transform to calculate the two-phase currents (Id, Iq) in the dq coordinate system, and therefore the calculation load in the motor control device 2 can be reduced compared to the conventional method.

[0040] The current detection device 3 includes an α-axis magnetic detection element Sα and a β-axis magnetic detection element Sβ arranged around three current lines connecting the motor M and the inverter 1. The current detection device 3 detects the current flowing through the three current lines based on these magnetic detection elements Sα and Sβ. More specifically, these magnetic detection elements Sα and Sβ are current sensors that output detection signals according to the components along the respective detection axes of the magnetic flux density of the magnetic field generated by the current flowing through each current line. Therefore, the output values ​​of the magnetic detection elements Sα and Sβ change depending on the relative positions of the magnetic detection elements Sα and Sβ with respect to the three current lines, the orientation of the detection axes, and the output sensitivity of the magnetic detection elements Sα and Sβ. In this embodiment, the ratio of the output to the input to the magnetic detection elements Sα and Sβ (output / input) is defined as the output sensitivity of these magnetic detection elements Sα and Sβ.

[0041] 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 α-axis magnetic detection element Sα is Vα, and the output value of the β-axis magnetic detection element Sβ is Vβ, the relative positions and detection axis directions of the magnetic detection elements Sα and Sβ with respect to these three current lines, as well as the output sensitivities of the magnetic detection elements Sα and Sβ are determined so that the following equation (3), which is equivalent to the Clarke transformation equation that converts three-phase currents (Iu, Iv, Iw) into two-phase currents (Iα, Iβ), holds.

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[0042] Incidentally, the applicant of the present application has filed a Chinese patent application CN202211040361.X (hereinafter, also referred to simply as the "prior application") which describes several specific examples of the layout of the three current lines and the two magnetic detection elements Sα and Sβ such that the above formula (3) holds when the two magnetic detection elements Sα and Sβ are arranged at different positions. However, as described in the prior application, when the two magnetic detection elements Sα and Sβ are arranged at different positions, the relative positions of the two magnetic detection elements Sα and Sβ with respect to the three current lines and the directions of the detection axes must be fixed by separate support members, which makes it easy for misalignment to occur and also increases the weight of the entire current detection device 3. In addition, in the layout described in the prior application, it is necessary to secure a sufficient space around the three current lines in order to arrange the two magnetic detection elements Sα and Sβ apart.

[0043] Therefore, the following describes the case where the two magnetic detection elements Sα and Sβ are arranged in the same position, more specifically, where the two magnetic detection elements Sα and Sβ are arranged so that their respective central positions coincide. However, if the central positions of the two magnetic detection elements Sα and Sβ are made to coincide, the distances between the central positions of the magnetic detection elements Sα and Sβ and the three current lines become equal. Therefore, the above formula (3) cannot be established by simply adjusting the layout of the two magnetic detection elements Sα and Sβ relative to the three current lines. On the other hand, the above formula (3) can be modified as shown in the following formula (4). This means that by making the output sensitivity of the β-axis magnetic detection element Sβ three times larger than the output sensitivity of the α-axis magnetic detection element Sα, and making the distance between the central positions of the two magnetic detection elements Sα, Sβ and the V-phase and W-phase current lines two times larger than the distance between the central positions of the two magnetic detection elements Sα, Sβ and the U-phase current line, the above equation (3) and the following equation (4) can be established while aligning the respective central positions of the two magnetic detection elements Sα, Sβ.

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[0044] Below, with reference to Figures 2 and 3, we will explain several layout examples of the relative positions and detection axis directions of the magnetic detection elements Sα and Sβ with respect to the three current lines so that the above equations (3) and (4) hold when the central positions of the two magnetic detection elements Sα and Sβ are aligned and the output sensitivity of the β-axis magnetic detection element Sβ is made greater than the output sensitivity of the α-axis magnetic detection element Sα.

[0045] Fig. 2 is a diagram showing a first layout example. More specifically, Fig. 2 is a diagram showing a U-phase current wire 5u, a V-phase current wire 5v, and a W-phase current wire 5w arranged in parallel to each other, viewed along a cross section perpendicular to the direction of extension of each current wire. In Figs. 2 and 3, regarding the direction of each current wire 5u, 5v, 5w, a cross indicates a current wire in which a positive current flows from the front of the paper to the back, and a black circle indicates a current wire in which a positive current flows from the back of the paper to the front.

[0046] As shown in FIG. 2, in the first setting example, the U-phase current wire 5u, the V-phase current wire 5v, and the W-phase current wire 5w are arranged parallel to each other and at the corners of an isosceles triangle in a cross-sectional view. The lengths of the two equal sides of the isosceles triangle are set so that the distance between the apex 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 set to 2L. In the following, a case will be described in which the U-phase current wire 5u is arranged at the apex angle, and the V-phase current wire 5v and the W-phase current wire 5w are arranged at the two base angles, respectively, but the present invention is not limited to this. The positions at which the current wires 5u, 5v, and 5w are arranged may be appropriately interchanged. In the following, a case will be described in which the direction of the current wires 5u, 5v, and 5w is such that a positive current flows from the front to the back of the paper, but the present invention is not limited to this. The direction of the current wires 5u, 5v, and 5w may be such that a positive current flows from the back to the front of the paper.

[0047] As shown in Fig. 2, when the current lines 5u, 5v, and 5w are arranged at the three corners of an isosceles triangle, the output sensitivity of the β-axis magnetic detection element Sβ is made larger than that of the α-axis magnetic detection element Sα, and the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ are arranged so that their respective central positions coincide on a first virtual line L1 passing through the apex angle and the midpoint P1 of the base. In addition, in the first layout example, the central positions of the α-axis and β-axis magnetic detection elements Sα and Sβ are arranged on the first virtual line L1 on the apex angle side of the midpoint P1 (i.e., inside the isosceles triangle), more specifically, at a midpoint between the midpoint P1 and the apex angle. In other words, the distance between the central positions of the two magnetic detection elements Sα and Sβ and the apex angle and the distance between the central positions of the two magnetic detection elements Sα and Sβ and the midpoint P1 are both L and are equal. As described above, the distance between the midpoint P1 and the V-phase current line 5v and the distance between the midpoint P1 and the W-phase current line 5w are both equal, being L. Therefore, the distance between the center positions of the two magnetic detection elements Sα, Sβ and the V-phase current line 5v and the W-phase current line 5w is 2 times larger than the distance between the center positions of the two magnetic detection elements Sα, Sβ and the U-phase current line 5u.

[0048] 2, the α-axis Oα, which is the detection axis of the α-axis magnetic detection element Sα, is disposed so as to be perpendicular to the first virtual line L1 and so as to be on the V-phase current line 5v side, and the β-axis Oβ, which is the detection axis of the β-axis magnetic detection element Sβ, is perpendicular to the α-axis Oα, parallel to the first virtual line L1, and so as to be on the midpoint P1 side, and the positive side. In other words, the β-axis Oβ of the β-axis magnetic detection element Sβ is perpendicular to the magnetic field formed by the current flowing through the U-phase current line 5u disposed at the apex angle, so the output value Vβ of the β-axis magnetic detection element Sβ does not change even if the current flowing through the U-phase current line 5u changes.

[0049] According to the first layout example described above, the α-axis magnetic detection element Sα detects the superposition of magnetic fields generated by currents flowing through the U-phase current line 5u, the V-phase current line 5v, and the W-phase current line 5w, and the β-axis magnetic detection element Sβ detects the superposition of magnetic fields generated by currents flowing through the V-phase current line 5v and the W-phase current line 5w with an output sensitivity that is 3 times larger than that of the α-axis magnetic detection element Sα. Therefore, the output values ​​Vα and Vβ of the two magnetic detection elements Sα and Sβ satisfy the above expressions (3) and (4).

[0050] Fig. 3 is a diagram showing a second layout example, more specifically, a U-phase current wire 5u, a V-phase current wire 5v, and a W-phase current wire 5w provided in parallel with each other, viewed along a cross section perpendicular to the direction in which each wire extends.

[0051] As shown in FIG. 3, in the second layout example, the U-phase current line 5u, the V-phase current line 5v, and the W-phase current line 5w are arranged parallel to each other and at equal intervals on a straight line L3 in a cross-sectional view. In the following, the length between adjacent current lines, that is, in the example of FIG. 3, the length between the U-phase current line 5u and the V-phase current line 5v and the length between the U-phase current line 5u and the W-phase current line 5w, are all L. In the following, a case will be described in which the U-phase current line 5u is arranged in the center on the straight line L3, the V-phase current line 5v is arranged on the right side of the U-phase current line 5u in FIG. 3 on the straight line L3, and the W-phase current line 5w is arranged on the left side of the U-phase current line 5u in FIG. 3 on the straight line L3, but the present invention is not limited to this. The positions at which the current lines 5u, 5v, and 5w are arranged may be appropriately interchanged. In the following, when three current lines are arranged on the straight line L3 in a cross-sectional view, the current line arranged in the center is also referred to as a central current line. That is, in the example of FIG. 3, the U-phase current line 5u is the central current line.

[0052] In the following, a case will be described in which the direction of two current lines other than the central current line among the three current lines is such that a positive current flows from the front to the back of the paper, and the direction of the central current line among the three current lines is such that a positive current flows from the back to the front of the paper, but the present invention is not limited to this. The direction of two current lines other than the central current line among the three current lines may be such that a positive current flows from the back to the front of the paper, and the direction of the central current line among the three current lines may be such that a positive current flows from the front to the back of the paper.

[0053] As shown in Fig. 3, when the current lines 5u, 5v, and 5w are arranged at equal intervals on a straight line L3, the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ are arranged on a second imaginary line L2 that is perpendicular to the straight line L3 and passes through the central current line 5u. In the second layout example, the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ are arranged above the straight line L3 in Fig. 3 so that their respective central positions coincide on the second imaginary line L2. More specifically, the two magnetic detection elements Sα and Sβ are installed at positions on the second imaginary line L2, a distance L away from the central current line 5u. In other words, the distance between the central positions of the two magnetic detection elements Sα and Sβ and the central current line 5u is equal to the distance between the central current line 5u and the left and right current lines 5v and 5w, both of which are L. Therefore, the distance between the center positions of the two magnetic detection elements Sα, Sβ and the V-phase current line 5v and the W-phase current line 5w is 2 times larger than the distance between the center positions of the two magnetic detection elements Sα, Sβ and the U-phase current line 5u.

[0054] 3, the α-axis Oα, which is the detection axis of the α-axis magnetic detection element Sα, is disposed so as to be perpendicular to the second virtual line L2 and so as to be positive on the V-phase current line 5v side. The β-axis Oβ, which is the detection axis of the β-axis magnetic detection element Sβ, is perpendicular to the α-axis Oα, parallel to the second virtual line L2, and so as to be positive on the V-phase current line 5v side. In other words, the β-axis Oβ of the β-axis magnetic detection element Sβ is perpendicular to the magnetic field formed by the current flowing through the U-phase current line 5u located in the center, so the output value Vβ of the β-axis magnetic detection element Sβ does not change even if the current flowing through the U-phase current line 5u changes.

[0055] According to the second layout example described above, the α-axis magnetic detection element Sα detects the superposition of magnetic fields generated by currents flowing through the U-phase current line 5u, the V-phase current line 5v, and the W-phase current line 5w, and the β-axis magnetic detection element Sβ detects the superposition of magnetic fields generated by currents flowing through the V-phase current line 5v and the W-phase current line 5w with an output sensitivity that is 3 times larger than that of the α-axis magnetic detection element Sα. Therefore, the output values ​​Vα and Vβ of the two magnetic detection elements Sα and Sβ satisfy the above expressions (3) and (4).

[0056] As described above, in the first and second layout examples, the two magnetic detection elements Sα and the β-axis magnetic detection element Sβ are arranged so that their detection axes Oα, Oβ are perpendicular to each other and have the same central position. Below, a specific configuration of the two-axis magnetic detection unit S in which the two magnetic detection elements Sα, Sβ are integrated so that their detection axes Oα, Oβ are perpendicular to each other and have the same central position will be described.

[0057] 4 is a perspective view showing the configuration of the two-axis magnetic detection unit S according to this embodiment. In the following, a case where the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ are each configured by a coil wound in a circular shape (i.e., a so-called coil type) will be described, but the present invention is not limited to this. Either or both of the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ may be configured by, for example, a Hall element.

[0058] The two-axis magnetic detection unit S is configured by combining an α-axis magnetic detection element Sα, which outputs a detection signal corresponding to the component along the α-axis Oα of the magnetic flux density of the magnetic field generated by a current flowing through a current line not shown, and a β-axis magnetic detection element Sβ, which outputs a detection signal corresponding to the component along the β-axis Oβ of the magnetic flux density, so that their respective detection axes Oα, Oβ are perpendicular to each other and their respective center positions coincide.

[0059] The α-axis magnetic detection element Sα includes an α-axis coil 61 formed by winding a conductive wire in an annular shape (for example, clockwise) as viewed along the α-axis Oα extending vertically upward in Fig. 4, and an α-axis support member 62 provided inside the α-axis coil 61 and supporting at least a part of the inner periphery 61a of the α-axis coil 61. Note that in the α-axis magnetic detection element Sα thus formed by combining the α-axis coil 61 and the α-axis support member 62, the center of the α-axis coil 61 becomes the center of the α-axis magnetic detection element Sα.

[0060] The α-axis support member 62 is disk-shaped extending along a plane perpendicular to the α-axis Oα, and supports the inner peripheral portion 61a of the α-axis coil 61 over the entire circumference. A central through-hole 63 extending along the α-axis Oα is formed in the center of the α-axis support member 62. Note that in this embodiment, the α-axis support member 62 supports the inner peripheral portion 61a of the α-axis coil 61 over the entire circumference, but the present invention is not limited to this. The α-axis support member 62 may support at least a portion of the inner peripheral portion 61a of the α-axis coil 61, including two opposing sides, similar to the β-axis support member 72 described below.

[0061] The β-axis magnetic detection element Sβ includes a β-axis coil 71 configured by winding a conductive wire in a circular shape (for example, clockwise) as viewed along the β-axis Oβ extending from the back side to the front side of the page along the horizontal direction in Fig. 4, and a β-axis support member 72 that is provided inside the β-axis coil 71 and supports at least a part of the inner periphery 71a of the β-axis coil 71 and at least a part of the α-axis magnetic detection element Sα. Note that in the β-axis magnetic detection element Sβ configured by combining the β-axis coil 71 and the β-axis support member 72 in this manner, the center of the β-axis coil 71 becomes the center of the β-axis magnetic detection element Sβ.

[0062] 4, the inner diameter of the β-axis coil 71 is larger than the outer diameter of the α-axis coil 61. This allows the α-axis coil 61 to be disposed inside the β-axis coil 71, which has a larger diameter than the α-axis coil 61, as shown in FIG. 4, and also allows the output sensitivity of the β-axis magnetic detection element Sβ to be larger than the output sensitivity of the α-axis magnetic detection element Sα. More specifically, by making the diameter of the β-axis coil 71 larger than the diameter of the α-axis coil 61 so that the linkage area of ​​the β-axis coil 71 is 3 times larger than the linkage area of ​​the α-axis coil 61, the output sensitivity of the β-axis magnetic detection element Sβ can be 3 times larger than the output sensitivity of the α-axis magnetic detection element Sα.

[0063] The β-axis support member 72 is plate-shaped and extends along the radial direction of the β-axis coil 71 in a plane perpendicular to the β-axis Oβ. The β-axis support member 72 supports the inner periphery 71a of the β-axis coil 71 by contacting two opposing sides of the inner periphery 71a of the β-axis coil 71 at both ends, the first inner periphery support portion 731 and the second inner periphery support portion 732. Note that in this embodiment, a case will be described in which the β-axis support member 72 supports at least a portion of the inner periphery 71a of the β-axis coil 71, including the two opposing sides, but the present invention is not limited thereto. The β-axis support member 72 may support the inner periphery 71a of the β-axis coil 71 over the entire circumference, similar to the α-axis support member 62 described above.

[0064] A central through hole 741 extending along the β-axis Oβ is formed in the center of the β-axis support member 72. In addition, in the β-axis support member 72, a first outer periphery support portion 742 and a second outer periphery support portion 743 are formed as through holes between the central through hole 741 and the first inner periphery support portion 731 and between the central through hole 741 and the second inner periphery support portion 732, respectively, extending along the β-axis Oβ. As shown in FIG. 4, the annular α-axis magnetic detection element Sα is inserted into these outer periphery support portions 742, 743 as through holes. In addition, when the α-axis magnetic detection element Sα is inserted into the α-axis support portions 742, 743 in this manner, the inner periphery of these α-axis support portions 742, 743 contact two opposing sides of the outer periphery portion 61b of the α-axis coil 61. As a result, the β-axis support member 72 supports at least a portion of the inner circumference 71a of the β-axis coil 71 and at least a portion of the α-axis magnetic detection element Sα so that the center position of the α-axis coil 61 and the center position of the β-axis coil 71 coincide and the α-axis Oα and the β-axis Oβ are perpendicular to each other.

[0065] In this embodiment, the α-axis support member 62 and the β-axis support member 72 are molded from a non-magnetic material, more specifically, from a resin, but the present invention is not limited to this. Either or both of the α-axis support member 62 and the β-axis support member 72 may be molded from a ferromagnetic material or a resin mixed with a ferromagnetic material. This allows the α-axis support member 62 and the β-axis support member 72 to be used as cores for the α-axis coil 61 and the β-axis coil 71.

[0066] In the two-axis magnetic detection unit S configured by integrating the two magnetic detection elements Sα and Sβ as described above, the output sensitivity of the β-axis magnetic detection element Sβ is set to the square root of 3 times the output sensitivity of the α-axis magnetic detection element Sα. The output sensitivity of the coil-type magnetic detection elements Sα and Sβ as described above is correlated with a plurality of output sensitivity adjustment parameters such as the interlinkage area of ​​the coil, the thickness of the coil wire, the material of the wire, the number of turns of the wire, the length of the wire, the presence or absence of a core, the material of the core, the shape of the core, and the cross-sectional area of ​​the core. Therefore, in this embodiment, the ratio of the output sensitivity of the α-axis magnetic detection element Sα to the output sensitivity of the β-axis magnetic detection element Sβ is adjusted to 1:√3 by providing a difference in one or more of the plurality of output sensitivity adjustment parameters between the two magnetic detection elements Sα and Sβ.

[0067] The current detection device 3 according to this embodiment provides the following advantages. (1) In the current detection device 3, the current flowing through the three current lines 5u, 5v, and 5w is detected based on two magnetic detection elements Sα and Sβ provided around the current lines 5u, 5v, and 5w. Therefore, according to this embodiment, 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, and the cost can be reduced accordingly. In addition, in the current detection device 3 according to this embodiment, the relative positions of the α-axis magnetic detection element Sα and the β-axis magnetic detection element Sβ with respect to the current lines 5u, 5v, and 5w and the directions of the detection axes Oα and Oβ are determined so that the above formulas (3) and (4), which are matrix calculation formulas equivalent to the Clarke transformation, are satisfied. Therefore, according to the current detection device 3, by using the outputs of these two magnetic detection elements Sα and Sβ, the motor control device 2 provided at the rear stage does not need to perform Clarke transformation by calculation, and the calculation load of the motor control device 2 can be reduced accordingly. Furthermore, the current detection device 3 reduces the computational load of the motor control device 2, thereby improving the energy efficiency of the entire system including the current detection device 3 and the motor control device 2.

[0068] Moreover, according to the current detection device 3, by determining the relative positions of the two magnetic detection elements Sα, Sβ with respect to the current lines 5u, 5v, 5w and the orientations of the detection axes Oα, Oβ so that the above formulas (3) and (4) hold, it is possible to utilize, as a significant signal, the magnetic fields of multiple phases that would be noise in a conventional current detection device in which a magnetic detection element is provided for each of the current lines 5u, 5v, 5w. This makes it possible to eliminate the need for measures against multiple-phase magnetic field interference that were necessary to suppress the above-mentioned noise in conventional current detection devices.

[0069] In a conventional current detection device in which a magnetic detection element is provided for each current line 5u, 5v, 5w, the relational expression between the output (V1, V2, V3) of each magnetic detection element and the current value (I1, I2, I3) of each phase is generally expressed by the following formula (5) using a non-diagonal matrix of current-sensor influence coefficients (a11, a12, ..., a33). For this reason, in a conventional current detection device, it is necessary to take measures against multi-phase magnetic field interference so that the influence coefficient of the non-diagonal components becomes 0, or to obtain the current value of each phase by multiplying the output of the magnetic detection element by an inverse matrix. In contrast, such measures are not necessary with a current detection device.

number

[0070] Moreover, according to the current detection device 3, by aligning the central positions of the two magnetic detection elements Sα, Sβ, these magnetic detection elements Sα, Sβ can be integrated into a two-axis magnetic detection unit S, so that the space occupied by these magnetic detection elements Sα, Sβ can be reduced and the magnetic detection elements Sα, Sβ can be easily aligned with respect to the current lines 5u, 5v, 5w. Furthermore, according to the current detection device 3, by aligning the central positions of these magnetic detection elements Sα, Sβ and making the output sensitivity of the β-axis magnetic detection element Sβ greater than the output sensitivity of the α-axis magnetic detection element Sα, it is possible to establish the above formulas (3) and (4) while making the distances between the magnetic detection elements Sα, Sβ and the current lines 5u, 5v, 5w equal.

[0071] (2) In the first layout example, the three current lines 5u, 5v, and 5w are arranged at the vertices of an isosceles triangle in a cross-sectional view, and a first virtual line L1 passing through the vertex and the midpoint P1 of the base of the isosceles triangle is defined. The two magnetic detection elements Sα and Sβ are arranged so that their respective central positions coincide on the first virtual line L1. This makes it possible to integrate the two magnetic detection elements Sα and Sβ into a two-axis magnetic detection unit S, thereby reducing the space occupied by the magnetic detection elements Sα and Sβ and also making it easier to align the magnetic detection elements Sα and Sβ with respect to the respective current lines 5u, 5v, and 5w.

[0072] (3) According to the first layout example, the distance between the apex and the midpoint P1 of the isosceles triangle is set equal to the length of the base, the centers of the two magnetic detection elements Sα and Sβ are located inside the isosceles triangle, the α-axis Oα which is the detection axis of the α-axis magnetic detection element Sα is perpendicular to the first virtual line L1, and the β-axis Oβ which is the detection axis of the β-axis magnetic detection element Sβ is parallel to the first virtual line L1. This makes it possible to obtain an output equivalent to the two-phase current after Clarke transformation.

[0073] (4) In the second layout example, three current lines 5u, 5v, and 5w are arranged at equal intervals on a straight line L3 in a cross-sectional view. A second virtual line L2 is defined that is perpendicular to the straight line L3 and passes through the central current line 5u. Two magnetic detection elements Sα and Sβ are arranged so that their respective central positions coincide on the second virtual line L2. This makes it possible to integrate the two magnetic detection elements Sα and Sβ into a two-axis magnetic detection unit S. This reduces the space occupied by these magnetic detection elements Sα and Sβ and also makes it easier to align these magnetic detection elements Sα and Sβ with respect to each of the current lines 5u, 5v, and 5w.

[0074] (5) According to the second layout example, the α-axis Oα of the α-axis magnetic detection element Sα is perpendicular to the second virtual line L2, and the β-axis Oβ of the β-axis magnetic detection element Sβ is parallel to the second virtual line L2. This makes it possible to obtain an output equivalent to the two-phase current after Clarke transformation.

[0075] (6) In this embodiment, the distance between the center positions of the two magnetic detection elements Sα, Sβ and the current lines 5v, 5w is made two times larger than the distance between the center positions and the current line 5u, and the output sensitivity of the β-axis magnetic detection element Sβ is made three times larger than the output sensitivity of the α-axis magnetic detection element Sα. This makes it possible to obtain an output equivalent to the two-phase current after Clarke transformation from the two magnetic detection elements Sα, Sβ.

[0076] (7) In this embodiment, the two magnetic detection elements Sα, Sβ are each a coil, and differences are provided between these two magnetic detection elements Sα, Sβ in one or more of a plurality of output sensitivity adjustment parameters, such as the interlinkage area, wire thickness, wire material, number of turns of the wire, wire length, presence or absence of a core, core material, core shape, and core cross-sectional area. This makes it easy to adjust the output sensitivity of the β-axis magnetic detection element Sβ to be higher than the output sensitivity of the α-axis magnetic detection element Sα, and more specifically, to adjust the ratio of the output sensitivity of the α-axis magnetic detection element Sα to the output sensitivity of the β-axis magnetic detection element Sβ to 1:√3.

[0077] (8) In this embodiment, the inner diameter of the β-axis coil 71 is made larger than the outer diameter of the α-axis coil 61, and the α-axis coil 61 is arranged inside the β-axis coil 71 so that their respective central positions coincide and the α-axis Oα and the β-axis Oβ are perpendicular to each other, thereby making it possible to reduce the space occupied by these magnetic detection elements Sα and Sβ.

[0078] (9) In this embodiment, the shape of the α-axis coil 61 can be maintained by supporting at least a part of the inner circumferential portion 61a of the α-axis coil 61 with the α-axis support member 62. Furthermore, by supporting at least a part of the inner circumferential portion 71a of the β-axis coil 71 and at least a part of the α-axis magnetic detection element Sα with the β-axis support member 72, the shape of the β-axis coil 71 can be maintained while the central positions of the α-axis coil 61 and the β-axis coil 71 are aligned. Therefore, according to this embodiment, deformation and displacement of the α-axis coil 61 and the β-axis coil 71 due to vibration can be prevented, and therefore the current detection accuracy can be maintained.

[0079] <Second embodiment> Next, a current detection device according to a second embodiment of the present invention will be described with reference to the drawings. The current detection device according to this embodiment differs from the current detection device 3 according to the first embodiment in the configuration of the biaxial magnetic detection unit. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0080] 5 is a perspective view showing the configuration of a biaxial magnetic detection unit S' of a current detection device 3' according to this embodiment. In the following, a case will be described in which the two magnetic detection elements Sα', Sβ' are coil-type like the biaxial magnetic detection unit S according to the first embodiment, but the present invention is not limited to this. Either or both of these magnetic detection elements Sα', Sβ' may be configured by, for example, a Hall element.

[0081] The two-axis magnetic detection unit S' is configured by combining an α-axis magnetic detection element Sα' that outputs a detection signal corresponding to a component along the α-axis Oα of the magnetic flux density of the magnetic field generated by a current flowing through a current line (not shown), and a β-axis magnetic detection element Sβ' that outputs a detection signal corresponding to a component along the β-axis Oβ of the magnetic flux density, so that the detection axes Oα, Oβ are perpendicular to each other and their central positions coincide. Note that the α-axis magnetic detection element Sα' and β-axis magnetic detection element Sβ' according to this embodiment differ from the α-axis magnetic detection element Sα and β-axis magnetic detection element Sβ according to the first embodiment in that they each output two systems of detection signals.

[0082] The α-axis magnetic detection element Sα' comprises two circular, annular first α-axis coil 81 and second α-axis coil 84 arranged parallel to each other, a first α-axis support member 82 arranged inside the first α-axis coil 81 and supporting at least a portion of the inner periphery 81a of the first α-axis coil 81, and a second α-axis support member 85 arranged inside the second α-axis coil 84 and supporting at least a portion of the inner periphery 84a of the second α-axis coil 84.

[0083] The first α-axis coil 81 and the second α-axis coil 84 are each formed by winding an independent conductive wire in a circular shape as viewed along the α-axis Oα. The first α-axis coil 81 is wound, for example, clockwise as viewed along the α-axis Oα, and the second α-axis coil 84 is wound, for example, counterclockwise as viewed along the α-axis Oα, that is, in a reverse direction to the first α-axis coil 81. The first α-axis coil 81 and the second α-axis coil 84 are arranged parallel to each other at a predetermined interval so as to be coaxial with the α-axis Oα as the central axis. Therefore, in the α-axis magnetic detection element Sα' formed by combining these two α-axis coils 81 and 84, the midpoint between the center of the first α-axis coil 81 and the center of the second α-axis coil 84 on the α-axis Oα becomes the center of the α-axis magnetic detection element Sα'. In the following description, it is assumed that the distance between these α-axis coils 81, 84 along the α-axis Oα is sufficiently small compared with the distance between the center of this α-axis magnetic detection element Sα' and each of the current lines 5u, 5v, 5w.

[0084] The first α-axis support member 82 is disk-shaped extending along a plane perpendicular to the α-axis Oα, and supports the inner peripheral portion 81a of the first α-axis coil 81 over the entire circumference. A central through-hole 83 extending along the α-axis Oα is formed in the center of the first α-axis support member 82. The second α-axis support member 85 is disk-shaped extending along a plane perpendicular to the α-axis Oα, and supports the inner peripheral portion 84a of the second α-axis coil 84 over the entire circumference. A central through-hole 86 extending along the α-axis Oα is formed in the center of the second α-axis support member 85. Note that in this embodiment, a case will be described in which these α-axis support members 82 and 85 support the inner peripheral portions 81a and 84a of the α-axis coils 81 and 84, respectively, over the entire circumference, but the present invention is not limited to this. These α-axis support members 82, 85 may support at least a portion of inner circumferential portions 81a, 84a of the α-axis coils 81, 84, including two opposing sides, similarly to the β-axis support members 92, 96 described below.

[0085] The β-axis magnetic detection element Sβ' includes two annular first β-axis coil 91 and second β-axis coil 85 arranged parallel to each other, a first β-axis support member 92 arranged inside the first β-axis coil 91 and supporting at least a portion of the inner circumference 91a of the first β-axis coil 91, and a second β-axis support member 96 arranged inside the second β-axis coil 95 and supporting at least a portion of the inner circumference 95a of the second β-axis coil 95.

[0086] The first β-axis coil 91 and the second β-axis coil 95 are each formed by winding an independent conductive wire in a circular shape as viewed along the β-axis Oβ. The first β-axis coil 91 is wound, for example, clockwise as viewed along the β-axis Oβ, and the second β-axis coil 95 is wound, for example, counterclockwise as viewed along the β-axis Oβ, that is, in a reverse direction to the first β-axis coil 91. The first β-axis coil 91 and the second β-axis coil 95 are arranged parallel to each other at a predetermined interval so as to be coaxial with the β-axis Oβ as the central axis. Therefore, in the β-axis magnetic detection element Sβ' formed by combining these two β-axis coils 91 and 95, the midpoint between the center of the first β-axis coil 91 and the center of the second β-axis coil 95 on the β-axis Oβ becomes the center of the β-axis magnetic detection element Sβ'. In the following description, it is assumed that the distance between these β-axis coils 91, 95 along the β-axis Oβ is sufficiently small compared with the distance between the center of this β-axis magnetic detection element Sβ' and each of the current lines 5u, 5v, 5w.

[0087] As shown in Fig. 5, the inner diameter of these β-axis coils 91, 95 is larger than the outer diameter of the above-mentioned α-axis coils 81, 84. As a result, the two α-axis coils 81, 84 can be arranged inside the β-axis coils 91, 95, which have a larger diameter than the α-axis coils 81, 84, so that the α-axis Oα and the β-axis Oβ are perpendicular to each other and the center position of the α-axis magnetic detection element Sα' and the center position of the β-axis magnetic detection element Sβ' coincide with the intersection of the α-axis Oα and the β-axis Oβ. As a result, the two α-axis coils 81, 84 are arranged parallel to each other with the intersection of the α-axis Oα and the β-axis Oβ between them, and the two β-axis coils 9, 95 are arranged parallel to each other with the intersection between them. In addition, the output sensitivity of the β-axis magnetic detection element Sβ' can be made larger than the output sensitivity of the α-axis magnetic detection element Sα'. More specifically, by making the diameters of the β-axis coils 91, 95 larger than the diameters of the α-axis coils 81, 84 so that the linkage area of ​​the β-axis coils 91, 95 is three times larger than the linkage area of ​​the α-axis coils 81, 84, the output sensitivity of the β-axis magnetic detection element Sβ' can be made three times larger than the output sensitivity of the α-axis magnetic detection element Sα'.

[0088] The first β-axis support member 92 is in the shape of a plate extending in a plane perpendicular to the β-axis Oβ along the radial direction of the first β-axis coil 91. The first β-axis support member 92 supports the inner periphery 91a of the first β-axis coil 91 by contacting two opposing sides of the inner periphery 91a of the first β-axis coil 91 at its two ends, that is, a first inner periphery support portion 931 and a second inner periphery support portion 932.

[0089] The second β-axis support member 96 is in the form of a plate extending along the radial direction of the second β-axis coil 95 in a plane perpendicular to the β-axis Oβ. The second β-axis support member 96 supports the inner periphery 95a of the second β-axis coil 95 by contacting two opposing sides of the inner periphery 915 of the second β-axis coil 95 at its two ends, that is, a first inner periphery support portion 971 and a second inner periphery support portion (not shown).

[0090] In this embodiment, the β-axis support members 92, 96 support at least a portion of the inner circumferential portions 91a, 95a of the β-axis coils 91, 95, including two opposing sides, but the present invention is not limited to this. Similar to the α-axis support members 82, 85 described above, these β-axis support members 92, 96 may support the inner circumferential portions 91a, 95a of the β-axis coils 91, 95 over the entire circumference.

[0091] These β-axis support members 92, 96 each have a plurality of (three in the example of FIG. 5) through holes 941, 981 formed therein that extend along the β-axis Oβ. The first α-axis support member 82 is fixed to an upper end portion 942, 982 of the β-axis support members 92, 96 on the upper side in FIG. 5 along the α-axis Oα, together with the first α-axis coil 81. The second α-axis support member 85 is fixed to a lower end portion 943, 973 of the β-axis support members 92, 96 on the lower side in FIG. 5 along the α-axis Oα, together with the second α-axis coil 84. As a result, the β-axis support members 92, 96 support at least a portion of the inner circumferential portions 91a, 95a of the β-axis coils 91, 95 and at least a portion of the α-axis magnetic detection element Sα' so that the center position of the α-axis magnetic detection element Sα' coincides with the center position of the β-axis magnetic detection element Sβ' and so that the α-axis Oα and the β-axis Oβ are perpendicular to each other.

[0092] In this embodiment, the α-axis support members 82, 85 and the β-axis support members 92, 96 are described as being molded from a non-magnetic material, more specifically, from a resin, but the present invention is not limited to this. Either or both of the α-axis support members 82, 85 and the β-axis support members 92, 96 may be molded from a ferromagnetic material or a resin mixed with a ferromagnetic material. This allows the α-axis support members 82, 85 and the β-axis support members 92, 96 to be used as cores for the α-axis coils 81, 84 and the β-axis coils 91, 95.

[0093] In the two-axis magnetic detection unit S' configured by integrating the two magnetic detection elements Sα', Sβ' as described above, the output sensitivity of the β-axis magnetic detection element Sβ' is set to the square root of 3 times the output sensitivity of the α-axis magnetic detection element Sα'. As in the first embodiment, the output sensitivity of the coil-type magnetic detection elements Sα', Sβ' described above is adjusted to a ratio of 1:√3 between the output sensitivity of the α-axis magnetic detection element Sα' and the output sensitivity of the β-axis magnetic detection element Sβ' by providing a difference in one or more of the plurality of output sensitivity adjustment parameters between the two magnetic detection elements Sα', Sβ'.

[0094] The current detection device 3' according to this embodiment has the following advantages. (10) In the current detection device 3', the α-axis magnetic detection element Sα' is composed of two α-axis coils 81, 84 that rotate in opposite directions when viewed along the α-axis Oα, and the β-axis magnetic detection element Sβ' is composed of two β-axis coils 91, 95 that rotate in opposite directions when viewed along the β-axis Oβ. Therefore, according to the current detection device 3', by using the differential outputs of the α-axis coils 81, 84 and the β-axis coils 91, 95 in the α-axis magnetic detection element Sα' and the β-axis magnetic detection element Sβ', it is possible to cancel common-mode noise (such as noise generated between the ground of the signal source and the ground of the measurement circuit, or noise generated when a current of another circuit flows into the ground of the measurement circuit), thereby improving the current detection accuracy.

[0095] That is, if the output value Vα1 of the first α-axis coil 81 is expressed as the sum of component A induced by a magnetic field and component B of the in-phase noise as shown in the following formula (6-1), the output value Vα2 of the second α-axis coil 84, which is rotated in the opposite direction to the first α-axis coil 81, as described above, is expressed by the following formula (6-2). Therefore, in the α-axis magnetic detection element Sα', the in-phase noise component B can be easily canceled by using the differential output (Vα1-Vα2) of the two α-axis coils 81, 84. Note that in the β-axis magnetic detection element Sβ' as well, the in-phase noise component can be easily canceled by using the differential output in a similar manner. Vα1=A+B (6-1) Vα2=-A+B (6-2)

[0096] (11) In the current detection device 3', the inner diameter of the two β-axis coils 91, 95 is made larger than the outer diameter of the two α-axis coils 81, 84, the two α-axis coils 81, 84 are arranged so that the α-axis Oα and the β-axis Oβ are perpendicular to each other inside the two β-axis coils 91, 95, the α-axis coils 81, 84 are arranged parallel to each other across the intersection of the α-axis Oα and the β-axis Oβ, and the β-axis coils 91, 95 are further arranged parallel to each other across this intersection. This makes it possible to reduce the space occupied by the magnetic detection elements Sα', Sβ' while aligning the central positions of the magnetic detection elements Sα', Sβ'.

[0097] (12) In the current detection device 3', at least a part of the inner peripheral portion 81a of the first α-axis coil 81 is supported by the first α-axis support member 82, and at least a part of the inner peripheral portion 84a of the second α-axis coil 84 is supported by the second α-axis support member 85, so that the shapes of these α-axis coils 81, 84 can be maintained. Furthermore, at least a part of the inner peripheral portion 91a of the first β-axis coil 91 and at least a part of the α-axis magnetic detection element Sα' are supported by the first β-axis support member 92, and at least a part of the inner peripheral portion 95a of the second β-axis coil 95 and at least a part of the α-axis magnetic detection element Sα' are supported by the second β-axis support member 96, so that the shapes of the β-axis coils 91, 95 can be maintained while the central positions of these magnetic detection devices Sα', Sβ' are aligned. Thus, according to the current detection device 3', it is possible to prevent deformation and displacement of the α-axis coils 81, 84 and the β-axis coils 91, 95 due to vibration, and therefore the current detection accuracy can be maintained.

[0098] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. The detailed configuration may be appropriately changed within the scope of the spirit of the present invention. [Explanation of symbols]

[0099] V…Vehicle W…Drive wheel M...Motor (three-phase motor) 5u…U phase current line 5v…V phase current line 5w…W phase current line 1...Inverter 2. Motor control device 3,3´…Current detection device S,S´…2-axis magnetic detection unit Sα, Sα´: α-axis magnetic detection element 61...α-axis coil 62...α-axis support member Sβ, Sβ´…β-axis magnetic detection element 71...β-axis coil 72...β-axis support member 731…First inner support part 732…Second inner circumference support part 742...First outer peripheral support part 743…Second outer peripheral support part 81…First α-axis coil 82...First α-axis support member 84…Second α-axis coil 85...Second α-axis support member 91…First β-axis coil 92...First β-axis support member 931…First inner support part 932…Second inner circumference support part 95…Second β-axis coil 96...Second β-axis support member 971…First inner support part

Claims

1. A current detection device that detects currents flowing through first, second and third phase current lines of a three-phase motor based on an α-axis magnetic detection element and a β-axis magnetic detection element provided around the first, second and third phase current lines, The central positions of the α-axis and β-axis magnetic detection elements are aligned, the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, a current detection device characterized in that, when a current value flowing through the first phase current line is I1, a current value flowing through the second phase current line is I2, a current value flowing through the third phase current line is I3, an output value of the α-axis magnetic detection element is Vα, and an output value of the β-axis magnetic detection element is Vβ, the relative positions and directions of the detection axes of the α-axis and β-axis magnetic detection elements with respect to the first phase, second phase, and third phase current lines are determined so that the following equation (1) is satisfied: [0010]

2. A current detection device that detects currents flowing through first, second and third phase current lines of a three-phase motor based on an α-axis magnetic detection element and a β-axis magnetic detection element provided around the first, second and third phase current lines, comprising: the first phase, second phase and third phase current lines are parallel to each other and arranged at corners of an isosceles triangle in a cross-sectional view; the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, A current detection device characterized in that the α-axis and β-axis magnetic detection elements are arranged so that their respective center positions coincide on a first imaginary line passing through the apex angle and the midpoint of the base of the isosceles triangle.

3. the distance between the apex angle and the midpoint is equal to the length of the base; the central positions of the α-axis and β-axis magnetic detection elements are provided on the first virtual line on the apex angle side of the midpoint, an α-axis that is a detection axis of the α-axis magnetic detection element is perpendicular to the first virtual line; 3. The current detection device according to claim 2, wherein a β-axis that is a detection axis of the β-axis magnetic detection element is parallel to the first imaginary line.

4. A current detection device that detects currents flowing through first, second and third phase current lines of a three-phase motor based on an α-axis magnetic detection element and a β-axis magnetic detection element provided around the first, second and third phase current lines, comprising: the first phase, second phase and third phase current wires are arranged parallel to each other and at equal intervals on a straight line in a cross-sectional view, the β-axis magnetic detection element has a higher output sensitivity than the α-axis magnetic detection element, a current detection device characterized in that the α-axis and β-axis magnetic detection elements are arranged so that their respective center positions coincide on a second virtual line that is perpendicular to the straight line and passes through a central current line that is located in the middle of the first, second, and third phase current lines.

5. an α-axis that is a detection axis of the α-axis magnetic detection element is perpendicular to the second virtual line; 5. The current detection device according to claim 4, wherein a β-axis that is a detection axis of the β-axis magnetic detection element is parallel to the second imaginary line.

6. a distance between a center position of the α-axis and β-axis magnetic detection elements and the second and third phase current lines is greater than a distance between the center position and the first phase current line by a square root of two; 6. The current detection device according to claim 1, wherein an output sensitivity of the β-axis magnetic detection element is greater than an output sensitivity of the α-axis magnetic detection element by a square root of three.

7. The α-axis and β-axis magnetic detection elements each include a coil wound in a circular shape when viewed along the detection axis of the element, The current detection device of claim 6, characterized in that the α-axis and β-axis magnetic detection elements differ in one or more of the linkage area of ​​the coil, the thickness of the wire of the coil, the material of the wire, the number of turns of the wire, the length of the wire, the presence or absence of a core, the material of the core, the shape of the core, and the cross-sectional area of ​​the core.

8. The α-axis magnetic detection element includes an α-axis coil wound in an annular shape when viewed along the α-axis, which is the detection axis of the element, The β-axis magnetic detection element includes a β-axis coil wound in an annular shape when viewed along the β-axis that is the detection axis of the element, an inner diameter of the β-axis coil is larger than an outer diameter of the α-axis coil, 6. The current detection device according to claim 1, wherein the α-axis coil is disposed inside the β-axis coil such that their respective central positions coincide with each other and the α-axis and the β-axis are perpendicular to each other.

9. the α-axis magnetic detection element includes the α-axis coil and an α-axis support member that is provided inside the α-axis coil and supports at least a part of an inner periphery of the α-axis coil, The current detection device according to claim 8, characterized in that the β-axis magnetic detection element comprises the β-axis coil and a β-axis support member that is arranged inside the β-axis coil and supports at least a portion of an inner periphery of the β-axis coil and at least a portion of the α-axis magnetic detection element.

10. The α-axis magnetic detection element includes a first α-axis coil and a second α-axis coil wound in a circular shape and arranged in parallel to each other when viewed along the α-axis, which is the detection axis of the element, The β-axis magnetic detection element includes a first β-axis coil and a second β-axis coil wound in a circular shape and arranged in parallel to each other when viewed along a β-axis that is a detection axis of the element, the second α-axis coil has a reverse rotation relative to the first α-axis coil when viewed along the α-axis, 6. The current detection device according to claim 1, wherein the second β-axis coil has a reverse rotation relative to the first β-axis coil when viewed along the β-axis.

11. The inner diameters of the first and second β-axis coils are larger than the outer diameters of the first and second α-axis coils, the first and second α-axis coils are provided inside the first and second β-axis coils such that the α-axis and the β-axis are perpendicular to each other, The first and second α-axis coils are arranged parallel to each other across an intersection of the α-axis and the β-axis, The current detection device according to claim 10 , wherein the first and second β-axis coils are provided in parallel with each other across the intersection.

12. the α-axis magnetic detection element includes the first and second α-axis coils, a first α-axis support member provided inside the first α-axis coil and supporting at least a part of an inner periphery of the first α-axis coil, and a second α-axis support member provided inside the second α-axis coil and supporting at least a part of an inner periphery of the second α-axis coil, The current detection device according to claim 11, characterized in that the β-axis magnetic detection element comprises the first and second β-axis coils, a first β-axis support member provided inside the first β-axis coil and supporting at least a portion of an inner periphery of the first β-axis coil and at least a portion of the α-axis magnetic detection element, and a second β-axis support member provided inside the second β-axis coil and supporting at least a portion of an inner periphery of the second β-axis coil and at least a portion of the α-axis magnetic detection element.

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