Current detection device

Abstract

To provide a current detection device for a three-phase motor with high toughness in preventing misalignment of the magnetic detection element relative to each phase current line. [Solution] The current detection device comprises an α-axis magnetic detection element and a β-axis magnetic detection element 8β provided around the current lines 6u and 6w. The detection axis Oβ of the β-axis magnetic detection element 8β is orthogonal to both current lines 6u and 6w and is positioned orthogonal to a first virtual line L1 connecting the current lines 6u and 6w on the β-axis element arrangement plane Pβ which includes the detection center of the β-axis magnetic detection element 8β. The detection center of the β-axis magnetic detection element 8β is positioned on a second virtual line L2 which is orthogonal to the first virtual line L1 and passes through the midpoint P0 of the first virtual line L1. The second axial distance Dy along the second virtual line L2 between the detection center of the β-axis magnetic detection element 8β and the U-phase current line 6u is within the range of an allowable installation error ±Δy centered on the first axial distance Dx along the first virtual line L1 between the U-phase current line 6u and the midpoint P0.

Description

[Technical Field]

[0001] The present invention relates to a current detection device. More specifically, it 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 technology]

[0002] In recent years, efforts to realize a low-carbon or decarbonized society have become more active, and in the field of vehicles, research and development on electric vehicles is being conducted to reduce CO2 emissions and improve energy efficiency.

[0003] Vector control is widely used as a control method for three-phase AC motors installed in electric vehicles and home appliances (such as air conditioners and washing machines). In vector control, the motor control device generates command signals to the inverter based on feedback control of the d-axis current and q-axis current defined on the dq coordinate system, which is the motor's rotating Cartesian coordinate system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2013 / 058282 [Patent Document 2] Chinese patent application CN202211040361.X [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Thus, in a motor control device, since feedback control of the current is performed on the dq coordinate system, 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 the one shown in Patent Document 1 into d-axis current and q-axis current. More specifically, in a motor control device, the three-phase current (Iu, Iv, Iw) detected by the current detection device is first converted into a two-phase current (Iα, Iβ) defined in a fixed coordinate system by Clarke transformation, and then this two-phase current (Iα, Iβ) is converted into a two-phase current (Id, Iq) defined in the dq coordinate system by Parke transformation using the motor rotation angle θ. In this way, in conventional vector control using the output of a current detection device, it is necessary to perform the operation of converting the three-phase current (Iu, Iv, Iw) to a two-phase current (Id, Iq) in the motor control device.

[0006] Furthermore, Patent Document 2 by the present applicant describes a technique (hereinafter also referred to as "spatial Clark transformation") that attempts to directly obtain two-phase currents (Iα, Iβ) without going through a Clark transformation performed by computer calculations by placing two magnetic detection elements at geometrically determined positions around three phase current lines. This spatial Clark transformation allows for a reduction in the number of magnetic detection elements and a reduction in the computational load on the computer compared to conventional methods.

[0007] However, Patent Document 2 did not adequately consider the effect of positional displacement of the magnetic detection element relative to each phase current line. In other words, in the spatial Clarke transformation technique shown in Patent Document 2, if the installation position of the magnetic detection element deviates from the initial ideal installation position, the relative position of this magnetic detection element with respect to each phase current line will also shift, and therefore the effect of positional displacement is considered to be significant.

[0008] The present invention aims to provide a current detection device for a three-phase motor with high toughness in positional misalignment of the magnetic detection element relative to each phase current line, and ultimately to contribute to improving energy efficiency. [Means for solving the problem]

[0009] (1) The current detection device according to the present invention (for example, current detection device 3 described later) detects the current flowing through the first phase current line (for example, the U phase current line 6u described later), the second phase current line (for example, the V phase current line 6V described later), and the third phase current line (for example, the W phase current line 6w described later) of a three-phase motor (for example, the motor M described later), and comprises an α-axis magnetic detection element (for example, the α-axis magnetic detection element 8α described later) provided around the first, second, and third phase current lines, and a β-axis magnetic detection element (for example, the β-axis magnetic detection element 8β described later) provided around the first and third phase current lines, wherein the detection axis of the β-axis magnetic detection element (for example, the detection axis Oβ described later) is orthogonal to both the first and third phase current lines and includes the detection center of the β-axis magnetic detection element The β-axis magnetic detection element is positioned on a placement surface (for example, the β-axis element placement surface Pβ, Pβ' described later) so as to be perpendicular to a first virtual line (for example, the first virtual line L1 described later) connecting the first and third phase current lines, the detection center of the β-axis magnetic detection element is positioned on a second virtual line (for example, the second virtual line L2 described later) that is perpendicular to the first virtual line and passes through the midpoint of the first virtual line (for example, the midpoint P0 described later), and the distance along the second virtual line between the detection center of the β-axis magnetic detection element and the first phase current line (for example, the second axis distance Dy described later) is within a predetermined allowable installation error range (for example, the allowable installation error ±Δy described later) centered on the distance along the first virtual line between the first phase current line and the midpoint (for example, the first axis distance Dx described later).

[0010] (2) The current detection device according to the present invention (for example, current detection device 3 described later) detects the current flowing through the first phase current line (for example, the U phase current line 6u described later), the second phase current line (for example, the V phase current line 6V described later), and the third phase current line (for example, the W phase current line 6w described later) of a three-phase motor (for example, the motor M described later), and comprises an α-axis magnetic detection element (for example, the α-axis magnetic detection element 8α described later) provided around the first, second, and third phase current lines, and a β-axis magnetic detection element (for example, the β-axis magnetic detection element 8β described later) provided around the first and third phase current lines, wherein the detection axis of the β-axis magnetic detection element (for example If, then, the detection axis Oβ) described later is orthogonal to both the first and third phase current lines and is arranged orthogonal to a first virtual line (e.g., the first virtual line L1 described later) connecting the first and third phase current lines on a β-axis element arrangement plane (e.g., the β-axis element arrangement plane Pβ, Pβ' described later) that includes the detection center of the β-axis magnetic detection element, and the detection center of the β-axis magnetic detection element is on a second virtual line (e.g., the second virtual line L2 described later) that is orthogonal to the first virtual line and passes through the midpoint of the first virtual line (e.g., the midpoint P0 described later), and the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line (e.g., the magnetic sensitivity coefficient k described later) is on the second virtual line (e.g., the second virtual line L2 described later) which is orthogonal to the first virtual line and passes through the midpoint of the first virtual line (e.g., the midpoint P0 described later). βu The system is characterized by being positioned within a predetermined allowable installation error range (for example, the allowable installation error ±Δy described later) centered on the position where the value of ) is the maximum or minimum value.

[0011] (3) In this case, it is preferable that the detection center of the α-axis magnetic detection element is located in an α-axis element arrangement plane (for example, the α-axis element arrangement plane Pα described later) that is perpendicular to the first, second and third phase current lines and different from the β-axis element arrangement plane.

[0012] (4) In this case, it is preferable that the α-axis magnetic detection element and the β-axis magnetic detection element are integrated. [Effects of the Invention]

[0013] (1) The current detection device according to the present invention comprises an α-axis magnetic detection element provided around three phase current lines and a β-axis magnetic detection element provided around at least two of the three lines (the first and third phase current lines), and detects the current flowing through the three current lines based on the output values ​​of these two magnetic detection elements. In the present invention, the detection axis of the β-axis magnetic detection element is positioned perpendicular to a first virtual line connecting the first and third phase current lines on the β-axis element arrangement plane which is perpendicular to both of the two phase current lines and includes the detection center. In the present invention, the detection center of the β-axis magnetic detection element is positioned on a second virtual line which is perpendicular to the first virtual line and passes through the midpoint of the first virtual line, i.e., at a position equal to the distance from the first and third phase current lines. In particular, in the present invention, the distance along the second virtual line between the detection center of the β-axis magnetic detection element and the first phase current line (hereinafter also referred to as the "second axis distance" between the β-axis magnetic detection element and the first phase current line) is set to within a predetermined allowable installation error range centered on the distance along the first virtual line between the detection center of the β-axis magnetic detection element and the first phase current line (hereinafter also referred to as the "first axis distance" between the β-axis magnetic detection element and the first phase current line). As will be explained later with reference to Figures 4 and 5, when the detection center of the β-axis magnetic detection element is installed at a position where the first axis distance and the second axis distance are approximately equal, the direction of change of the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line and the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the third phase current line, with respect to the positional displacement of the β-axis magnetic detection element along the first virtual line, is both towards zero. Therefore, according to the present invention, the positional displacement toughness of the β-axis magnetic detection element with respect to the first and third phase current lines along the first virtual line can be improved, and consequently, this can contribute to improving energy efficiency.

[0014] (2) In the current detection device according to the present invention, the detection center of the β-axis magnetic detection element is positioned on a second virtual line that is perpendicular to the first virtual line and passes through the midpoint of the first virtual line, that is, at a position equal to the first and third phase current lines, similar to the invention described in (1) above. In particular, in the present invention, the detection center of the β-axis magnetic detection element is positioned within a predetermined allowable installation error range centered on the position on the second virtual line where the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line is at its maximum or minimum value. As will be explained later with reference to Figures 4 and 5, when the detection center of the β-axis magnetic detection element is positioned near the position on the second virtual line where the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line is at its maximum or minimum value, the direction of change in the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line and the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the third phase current line, with respect to the positional displacement of the β-axis magnetic detection element along the first virtual line, is both towards 0. Therefore, according to the present invention, the positional misalignment toughness of the β-axis magnetic detection element along the first virtual line with respect to the first and third phase current lines can be improved, and consequently, this can contribute to improving energy efficiency.

[0015] (3) In the present invention, the detection center of the α-axis magnetic detection element is positioned in an α-axis element arrangement plane that is orthogonal to the first, second, and third phase current lines and different from the β-axis element arrangement plane. Therefore, according to the present invention, the output value of the α-axis magnetic detection element can be made proportional to the α-phase current value obtained by combining the currents flowing through the first, second, and third phase current lines in a ratio determined by the Clarke transformation. Furthermore, in the present invention, the detection center of the β-axis magnetic detection element is positioned in a β-axis element arrangement plane that is orthogonal to the first and third phase current lines and different from the α-axis element arrangement plane. Therefore, according to the present invention, the output value of the β-axis magnetic detection element can be made proportional to the β-phase current value obtained by combining the currents flowing through the first and third phase current lines in a ratio determined by the Clarke transformation and that is orthogonal to the α-phase current value.

[0016] (4) In the present invention, by integrating the α-axis magnetic detection element and the β-axis magnetic detection element, the amount of misalignment of these α-axis and β-axis magnetic detection elements with respect to each phase current line can be made equal. Furthermore, as will be explained later with reference to Figures 7 and 8, in the state in which these α-axis and β-axis magnetic detection elements are integrated, the fluctuation in the phase error between the output values ​​of these α-axis and β-axis magnetic detection elements with respect to the misalignment of the detection center of these α-axis and β-axis magnetic detection elements along the first virtual line is minimized when the second axial distance and the first axial distance between the detection center of the α-axis and β-axis magnetic detection elements and the first phase current line are made approximately equal. Therefore, according to the present invention, the misalignment toughness of the α-axis and β-axis magnetic detection elements with respect to the first, second and third phase current lines along the first virtual line can be improved. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows the configuration of a current detection device according to the first embodiment of the present invention and an electric vehicle equipped with this current detection device. [Figure 2] This is a side view of the three phase current lines and the α-axis element arrangement plane and β-axis element arrangement plane perpendicular to these phase current lines. [Figure 3] This diagram schematically shows an example of the arrangement of three phase current lines and an α-axis magnetic detection element on the α-axis element arrangement plane. [Figure 4] This diagram schematically shows an example of the arrangement of two phase current lines and a β-axis magnetic detection element on the β-axis element arrangement plane. [Figure 5] This figure shows the change in the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the U-phase current line and W-phase current line in response to a change in the first axis distance. [Figure 6] This figure schematically shows an example of the arrangement of three phase current lines and a β-axis magnetic detection element on the β-axis element arrangement surface according to a modified example of the first embodiment. [Figure 7] This figure schematically shows the configuration of a sensor unit according to a second embodiment of the present invention. [Figure 8] This figure shows the relationship between the misalignment of the detection centers of the two magnetic detection elements and the phase error between the output values ​​of the two magnetic detection elements. [Modes for carrying out the invention]

[0018] <First Embodiment> Hereinafter, a current detection device according to the first embodiment of the present invention and an electric vehicle equipped with this current detection device will be described with reference to the drawings.

[0019] 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.

[0020] 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 sensor unit 7 that generates a signal corresponding to the current flowing through 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 from the sensor unit 7 and the resolver 4.

[0021] 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.

[0022] The sensor unit 7 includes an α-axis magnetic detection element 8α provided around three phase current lines (U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w) connecting the motor M and the inverter 1, and a β-axis magnetic detection element 8β provided around at least two of these three phase current lines 6u, 6v, and 6w. These magnetic detection elements 8α and 8β each generate a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each phase current line 6u, 6v, and 6w along their respective detection axes. Specific examples of the arrangement layout of these α-axis and β-axis magnetic detection elements 8α and 8β and the three phase current lines 6u, 6v, and 6w will be explained later with reference to Figures 2 to 6.

[0023] The motor control device 2 is a computer that generates a drive signal for the gate drive circuit of the inverter 1 and inputs it to the gate drive circuit by performing vector control based on detection signals from two magnetic detection elements 8α and 8β and the resolver 4.

[0024] The motor control device 2 includes an AD conversion unit 21, a current value acquisition unit 22, a dq conversion unit 23, and a duty cycle calculation unit 24 as modules related to the execution of the vector control described above.

[0025] The AD conversion unit 21 performs AD conversion on the detection signals of the α-axis and β-axis magnetic detection elements 8α and 8β, thereby converting the output values ​​(S) of these α-axis and β-axis magnetic detection elements 8α and 8β. α ,S β ) obtain.

[0026] The current value acquisition unit 22 acquires the output values ​​(S) of the α-axis and β-axis magnetic detection elements 8α and 8β obtained by the AD conversion unit 21. α ,S β Based on this, the α-phase current value I, which corresponds to the two-phase current obtained by performing a Clarke transform on the three-phase current (Iu, Iv, Iw) as shown in equation (1-1) below, is obtained. α and β-phase current value I βObtain it. In this embodiment, the current value acquisition unit 22 uses the output values (S α , S β ) of the α-axis and β-axis magnetic detection elements 8α and 8β as they are as the α-phase and β-phase current values (I α , I β ) for explanation. However, the present invention is not limited to this. For example, as described in Japanese Patent Application No. 2024-017417 by the applicant of the present application, the current value acquisition unit 22 multiplies the output values (S α , S β ) of the α-axis and β-axis magnetic detection elements 8α and 8β respectively by a predetermined α-phase gain G α and β-phase gain G β to obtain the α-phase current value I α and β-phase current value I β . In this case, the values of these α-phase and β-phase gains (G α , G β ) are set so that the amplitudes of the α-phase and β-phase current values (I α , I β ) are equal. Therefore, in this embodiment, the current detection device 3 that detects the current flowing through the three-phase current lines 6u, 6v, and 6w of the motor M is composed of two magnetic detection elements 8α and 8β, an AD conversion unit 21, and a current value acquisition unit 22.

Number

[0027] The dq conversion unit 23 calculates the d-axis current Id and the q-axis current Iq by performing a known calculation using the current values (I α , I β ) acquired by the current value acquisition unit 22 and the detection signal of the resolver 4.

[0028] The duty calculation unit 24 obtains the d-axis current command Idc and the q-axis current command Iqc corresponding to the required driving force by the driver, and performs feedback control based on the deviation (Idc - Id, Iqc - Iq) of these current values to generate a driving signal for the gate drive circuit of the inverter 1 so as to realize the required driving force by the driver, and inputs it to the gate drive circuit.

[0029] Figure 2 is a side view of the three phase current lines 6u, 6v, and 6w, as well as the α-axis element arrangement plane Pα and β-axis element arrangement plane Pβ which are perpendicular to these phase current lines. In this embodiment, as shown in Figure 2, the detection center of the α-axis magnetic detection element 8α is provided in a virtual α-axis element arrangement plane Pα which is perpendicular to the three phase current lines 6u, 6v, and 6w, and the detection center of the β-axis magnetic detection element 8β is provided in a β-axis element arrangement plane Pβ which is perpendicular to at least two phase current lines 6u, 6w and is different from the α-axis element arrangement plane Pα. That is, the following description will focus on the case where the distance between the β-axis magnetic detection element 8β and the V-phase current line 6v is sufficiently greater than the distance between the β-axis magnetic detection element 8β and the other two phase current lines 6u, 6w, but the present invention is not limited to this. The case in which the β-axis magnetic detection element 8β is arranged near the three phase current lines 6u, 6v, and 6w, similar to the α-axis magnetic detection element 8α, will be described later with reference to Figure 6 as a modified example.

[0030] Figure 3 schematically shows an example of the arrangement of three phase current lines 6u, 6v, and 6w and the α-axis magnetic detection element 8α on the α-axis element arrangement plane Pα. In Figure 3, the three phase current lines 6u, 6v, and 6w are arranged linearly at equal intervals in the order of U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w on the α-axis element arrangement plane Pα, but the present invention is not limited to this. When the three phase current lines 6u, 6v, and 6w are arranged in this way, the detection axis Oα of the α-axis magnetic detection element 8α is arranged parallel to the imaginary line passing through the three phase current lines 6u, 6v, and 6w, as shown in Figure 3. Furthermore, the detection center of the α-axis magnetic detection element 8α is positioned at a predetermined location on an imaginary line that is perpendicular to the imaginary line passing through the three phase current lines 6u, 6v, and 6w and also passes through the central V-phase current line 6v, as shown in Figure 3.

[0031] Here, the output value S of the α-axis magnetic detection element 8α is given. α This is the magnetic sensitivity coefficient (k) for each phase current line 6u, 6v, 6w of the α-axis magnetic detection element 8α. αu ,k αv ,k αw Using ), it can be expressed by the following equation (2-1). These magnetic sensitivity coefficients (kαu ,k αv ,k αw ) are values ​​determined by the relative position of the α-axis magnetic detection element 8α with respect to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axis. More specifically, for example, the magnetic sensitivity coefficient k of the α-axis magnetic detection element 8α with respect to the W phase current line 6w. αw It is defined by the following equation (2-2) according to Ampère's law. In the following equation (2-2), μ is the permeability. Also, in the following equation (2-2), θ wα is the angle between the magnetic field vector of the W-phase current line 6w and the detection axis of the α-axis magnetic detection element 8α, and (x α ,y α ) is the coordinate value of the α-axis magnetic detection element 8α on the α-axis element arrangement plane, and (x w ,y w ) are the coordinate values ​​of the W-phase current line 6w on the α-axis element arrangement plane. Note that other magnetic sensitivity coefficients (k αu ,k αw ) is also defined based on Ampere's law, similar to equation (2-2) below, so a detailed explanation is omitted. As described above, the magnetic sensitivity coefficient (k αu ,k αv ,k αw The position of the α-axis magnetic detection element 8α relative to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axis are determined accordingly.

number

[0032] Furthermore, the detection center of the α-axis magnetic detection element 8α is located on the α-axis element arrangement surface Pα, where the magnetic sensitivity coefficient (k αu ,k αv ,k αw The α-axis magnetic detection element 8α is positioned such that the following equation (3) holds true. α α-phase current value I α It can be made proportional to that.

number

[0033] Figure 4 schematically shows an example of the arrangement of two phase current lines 6u and 6w and a β-axis magnetic detection element 8β on the β-axis element arrangement plane Pβ.

[0034] As shown in Figure 4, the detection axis Oβ of the β-axis magnetic detection element 8β is orthogonal to both the U-phase current line 6u and the W-phase current line 6w, and is positioned orthogonal to the first virtual line L1 connecting the U-phase current line 6u and the W-phase current line 6w on the β-axis element arrangement plane Pβ which includes the detection center of the β-axis magnetic detection element 8β. Furthermore, the detection center of the β-axis magnetic detection element is positioned on a second virtual line L2 which is orthogonal to the first virtual line L1 and passes through the midpoint P0 of the first virtual line L1. As a result, the output value S of the β-axis magnetic detection element 8β is as shown in equation (4) below. β β-phase current value I β It can be made proportional to that.

number

[0035] In the following, the distance along the first virtual line L1 between the detection center of the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) on the β-axis element arrangement plane Pβ will be referred to as the first axis distance and denoted as "Dx". The distance along the second virtual line L2 between the detection center of the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) on the β-axis element arrangement plane Pβ will be referred to as the second axis distance and denoted as "Dy".

[0036] Figure 5 shows the magnetic sensitivity coefficient k for each phase current line 6u, 6w of the β-axis magnetic detection element 8β with respect to the change in the first axis distance Dx. βu ,k βw This figure shows the change. In Figure 5, the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the U-phase current line 6u is shown. βu The thick line indicates the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the W-phase current line 6w. βw This is shown by a thin line. Figure 5 also shows the magnetic sensitivity coefficient k when the second axial distance Dy is 2 [mm], 4 [mm], and 6 [mm]. βu ,k βw These are illustrated using different line types.

[0037] As shown in Figure 5, the magnetic sensitivity coefficient k βu and magnetic sensitivity coefficient k βw Although the signs are opposite, the absolute values ​​are the same because the distance between the β-axis magnetic detection element 8β and the phase current lines 6u and 6w is the same. When the second axis distance Dy is increased, the distance between the β-axis magnetic detection element 8β and the phase current lines 6u and 6w also increases, so the magnetic sensitivity coefficient k βu ,k βw It also approaches 0.

[0038] Furthermore, when the first axis distance Dx is varied between 0 [mm] and 20 [mm], the magnetic sensitivity coefficient k βu It exhibits upward convex behavior, and the magnetic sensitivity coefficient k βw It exhibits downward convex behavior. More specifically, when the second axial distance Dy is 2 [mm], the magnetic sensitivity coefficient k is when the first axial distance Dx is approximately 2 [mm]. βu The magnetic sensitivity coefficient k reaches its maximum value. βw This is the minimum value. Also, when the second axis distance Dy is 4 [mm], the magnetic sensitivity coefficient k is when the first axis distance Dx is approximately 4 [mm]. βu The magnetic sensitivity coefficient k reaches its maximum value. βw This is the minimum value. Also, when the second axis distance Dy is 6 [mm], the magnetic sensitivity coefficient k is when the first axis distance Dx is approximately 6 [mm]. βu The magnetic sensitivity coefficient k reaches its maximum value. βw The magnetic sensitivity coefficient k is minimized. βu The value reaches its maximum when the first axial distance Dx and the second axial distance Dy between the β-axis magnetic detection element 8β and the U-phase current line 6u are approximately equal. Also, the magnetic sensitivity coefficient k βw This value is minimized when the first axial distance Dx and the second axial distance Dy between the β-axis magnetic detection element 8β and the W-phase current line 6w are approximately equal.

[0039] Here, as shown in Figure 4, we assume that the detection center of the β-axis magnetic detection element 8β is shifted by a distance dx from the second virtual line L2 toward the U-phase current line 6u in a direction perpendicular to the second virtual line L2. When the β-axis magnetic detection element 8β is displaced toward the U-phase current line 6u in this way, the first axial distance between the β-axis magnetic detection element 8β and the U-phase current line 6u becomes shorter, while the first axial distance between the β-axis magnetic detection element 8β and the W-phase current line 6w becomes longer.

[0040] Therefore, as shown by the white circle in Figure 5, the second axial distance Dy is made approximately equal to the first axial distance Dx, in other words, the second axial distance Dy is equal to the magnetic sensitivity coefficient k. βu The value reaches its maximum and the magnetic sensitivity coefficient k βw When the position of the β magnetic detection element 8β is set to the position where it is at its minimum value, the magnetic sensitivity coefficient k, which is a positive value, will be affected. βu The magnetic sensitivity coefficient k decreases towards 0 and is negative. βw It increases towards 0. Also, the second axis distance Dy is the magnetic sensitivity coefficient k. βu ,k βw When the length is set such that it reaches an extreme value, the magnetic sensitivity coefficient k for minute positional displacements is βu ,k βw The change is also small. In contrast, as shown by the black circles in Figure 5, when the second axial distance Dy is set to a length that is significantly different from the first axial distance Dx, in other words, when the second axial distance Dy is set to the magnetic sensitivity coefficient k βu ,k βw When the magnetic sensitivity coefficient k is set to a length significantly different from the length at which it reaches its extreme value, and a positional displacement of the β magnetic detection element 8β occurs as described above, the magnetic sensitivity coefficient k is positive. βu The magnetic sensitivity coefficient k increases in the direction away from 0 and is negative. βw It increases toward 0.

[0041] Magnetic sensitivity coefficient k for each phase current line 6u, 6w of the β-axis magnetic detection element 8β βu ,k βw Because of the above characteristics regarding positional misalignment, by making the second axis distance Dy approximately equal to the first axis distance Dx, the output value S of the β-axis magnetic detection element 8β caused by positional misalignment is determined. βIt can be said that the phase error can be minimized. Here, the output value S of the β-axis magnetic detection element 8β β The phase error refers to the output value S of the β-axis magnetic detection element 8β before the positional deviation occurs β and the output value S of the β-axis magnetic detection element 8β after the positional deviation occurs β refers to the phase difference therebetween. For this reason, the second-axis distance Dy between the β-axis magnetic detection element 8β and the U-phase current line 6u (or the W-phase current line 6w) is set within a range of a predetermined allowable installation error ±Δy centered on the first-axis distance Dx between the β-axis magnetic detection element 8β and the U-phase current line 6u (or the W-phase current line 6w) (Dx - Δy ≤ Dy ≤ Dx + Δy). In other words, the detection center of the β-axis magnetic detection element 8β is within a range of an allowable installation error ±Δy centered on the position where the magnetic sensitivity coefficient k βu (or the magnetic sensitivity coefficient k βw ) of the β-axis magnetic detection element 8β with respect to the U-phase current line 6u (or the W-phase current line 6w) on the second virtual line L2 becomes the maximum value (or the minimum value). Here, the width Δy of the allowable installation error is set to a length less than the second-axis distance Dy (Δy ≤ Dy), more specifically, a length less than one-tenth of the second-axis distance Dy (Δy ≤ Dy / 10).

[0042] According to the current detection device 3 according to the present embodiment, the following effects are obtained. (1) The current detection device 3 includes an α-axis magnetic detection element 8α provided around three phase current lines 6u, 6v, 6w, and a β-axis magnetic detection element 8β provided around two phase current lines 6u, 6w, and the output values (S α , S βBased on this, the current flowing through the three phase current lines 6u, 6v, and 6w is detected. In the current detection device 3, the detection axis Oβ of the β-axis magnetic detection element 8β is positioned perpendicular to the first virtual line L1 connecting the U-phase current line 6u and the W-phase current line 6w on the β-axis element arrangement plane Pβ which is perpendicular to both of the two phase current lines 6u and 6w and includes their detection center. In the current detection device 3, the detection center of the β-axis magnetic detection element 8β is positioned on the second virtual line L2 which is perpendicular to the first virtual line L1 and passes through the midpoint P0 of the first virtual line L1, i.e., at a position equal to the distance from the U-phase current line 6u and the W-phase current line 6w. In particular, in this embodiment, the second axial distance Dy between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) is set within a predetermined allowable installation error ±Δy centered on the first axial distance Dx between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w). As described above, when the detection center of the β-axis magnetic detection element 8β is positioned such that the first axial distance Dx and the second axial distance Dy are approximately equal, the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the U-phase current line 6u is given by the positional displacement of the β-axis magnetic detection element 8β along the first virtual line L1. βu and the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the W-phase current line 6w βw The direction of change is always towards 0. Therefore, the current detection device 3 can improve the positional misalignment toughness of the β-axis magnetic detection element 8β along the first virtual line L1 with respect to the U-phase current line 6u and W-phase current line 6w, and thereby contribute to improving energy efficiency.

[0043] (2) In this embodiment, the detection center of the β-axis magnetic detection element 8β is set to the magnetic sensitivity coefficient k of the U-phase current line 6u (or W-phase current line 6w) of the β-axis magnetic detection element 8β on the second virtual line L2. βu (or, magnetic sensitivity coefficient k) βw The detection center of the β-axis magnetic detection element 8β is positioned within a predetermined allowable installation error ±Δy centered on the position where the value (or minimum value) is maximized (or minimized). As described above, the detection center of the β-axis magnetic detection element 8β is positioned on the second virtual line L2 with respect to the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the U-phase current line 6u (or W-phase current line 6w). βu (or, magnetic sensitivity coefficient k) βwWhen installed near the position where [[ID=]]) becomes the maximum value (or the minimum value), the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the displacement along the first virtual line L1 and with respect to the U-phase current line 6u of the β-axis magnetic detection element 8β βu and the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the W-phase current line 6w βw both change in the direction of the zero side. Therefore, according to the current detection device 3, the positional deviation toughness along the first virtual line L1 with respect to the U-phase current line 6u and the W-phase current line 6w of the β-axis magnetic detection element 8β can be improved, and thus it can contribute to the improvement of energy efficiency.

[0044] (3) In this embodiment, the detection center of the α-axis magnetic detection element 8α is arranged in the α-axis element arrangement plane Pα that is orthogonal to the three-phase current lines 6u, 6v, 6w and different from the β-axis element arrangement plane Pβ. Therefore, according to this embodiment, the output value Sα of the α-axis magnetic detection element 8α can be made proportional to the α-phase current value I α obtained by synthesizing the currents flowing through the three-phase current lines 6u, 6v, 6w at a ratio determined by Clarke transformation. Also, in this embodiment, the detection center of the β-axis magnetic detection element 8β is arranged in the β-axis element arrangement plane Pβ that is orthogonal to the U-phase current line 6u and the W-phase current line 6w and different from the α-axis element arrangement plane Pα. Therefore, according to this embodiment, the output value S β of the β-axis magnetic detection element 8β can be made proportional to the β-phase current value I α obtained by synthesizing the currents flowing through the U-phase current line 6u and the W-phase current line 6w at a ratio determined by Clarke transformation and orthogonal to the α-phase current value I β .

[0045] <Modification Example> In this embodiment, as shown in FIG. 4, the case where the detection center of the β-axis magnetic detection element 8β is arranged in the β-phase arrangement plane Pβ that is orthogonal to the two-phase current lines 6u, 6w has been described, but the present invention is not limited to this.

[0046] The detection center of the β-axis magnetic detection element 8β may be positioned within the β-phase element arrangement plane Pβ' which is perpendicular to the three phase current lines 6u, 6v, and 6w, as shown in Figure 6. In this case, the V-phase current line 6v is positioned so as to intersect the β-phase element arrangement plane Pβ' at the midpoint P0 of the first virtual line L1 which passes through the U-phase current line 6u and the W-phase current line 6w, and the detection center of the β-axis magnetic detection element 8β is positioned on the second virtual line L2, similar to the example shown in Figure 4, and the detection axis Oβ of the β-axis magnetic detection element 8β is preferably positioned perpendicular to the first virtual line L1. This makes it possible to make the magnetic field formed by the current flowing through the V-phase current line 6v and the detection axis Oβ of the β-axis magnetic detection element 8β perpendicular, so that the output value S of the β-axis magnetic detection element 8β can be made perpendicular to the first virtual line L1, as shown in equation (4) above. β β-phase current value I β It can be made proportional to that.

[0047] Furthermore, similar to the example shown in Figure 4, it is preferable that the second axial distance Dy between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) be set within a predetermined allowable installation error ±Δy (Dx-Δy≦Dy≦Dx+Δy) centered on the first axial distance Dx between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w). In other words, the detection center of the β-axis magnetic detection element 8β is the magnetic sensitivity coefficient k of the β-axis magnetic detection element 8β with respect to the U-phase current line 6u (or W-phase current line 6w) on the second virtual line L2. βu (or magnetic sensitivity coefficient k) βw It is preferable to position the element within the range of the allowable installation error ±Δy centered on the position where the value is at its maximum (or minimum) value. This improves the positional misalignment toughness of the β-axis magnetic detection element 8β, similar to the example shown in Figure 4.

[0048] Furthermore, as shown in Figure 6, when a β-axis magnetic detection element 8β is provided, if the detection center of the β-axis magnetic detection element 8β shifts from the second virtual line L2 along a direction perpendicular to this second virtual line L2, the output value S of the β-axis magnetic detection element 8β will change. β This will be affected by the current flowing through the V-phase current line 6v. However, the two magnetic sensitivity coefficients k for positional displacement βu ,k βwThe change is the same as in the example shown in Figure 4. Therefore, even when the detection center of the β-axis magnetic detection element 8β is placed on the β-phase element arrangement plane Pβ' as shown in Figure 6, the misalignment toughness of the β-axis magnetic detection element 8β can be improved, similar to the example shown in Figure 4.

[0049] <Second Embodiment> Next, a current detection device according to a second embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for components that are the same as those in the current detection device 3 according to the first embodiment, and detailed descriptions are omitted. 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 sensor unit.

[0050] Figure 7 is a schematic diagram showing the configuration of the sensor unit 7A according to this embodiment. The sensor unit 7A comprises an α-axis magnetic detection element 8α and a β-axis magnetic detection element 8β provided around three phase current lines 6u, 6v, and 6w, and a substrate 80 to which these magnetic detection elements 8α and 8β are fixed. The detection center and detection axis of the α-axis magnetic detection element 8α are arranged within the α-axis element arrangement plane Pα in the manner described with reference to Figure 3, and the detection center and detection axis of the β-axis magnetic detection element 8β are arranged within the β-axis element arrangement plane Pβ' in the manner described with reference to Figure 6. In other words, the sensor unit 7A according to this embodiment differs from the sensor unit 7 according to the first embodiment in that the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β are integrated by the substrate 80. Therefore, for example, as shown in Figure 6, if the detection center of the β-axis magnetic detection element 8β is shifted by a distance dx toward the U-phase current line 6u side along a direction perpendicular to the second virtual line L2, the α-axis magnetic detection element 8α will also be shifted by a distance dx toward the U-phase current line 6u side.

[0051] Figure 8 shows the displacement (dx) of the detection centers of the two magnetic detection elements 8α and 8β, and the output value S of the two magnetic detection elements 8α and 8β. α ,S β This figure shows the relationship with the phase error between the two magnetic detection elements 8α and 8β. Here, the phase error is the output value S of the two magnetic detection elements 8α and 8β. α ,S βThis refers to the error relative to the phase difference (90°). Figure 8 also illustrates the phase error for different line types when the ratio of the second axial distance Dy to the first axial distance Dx between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) (Dy / Dx) is set to "0.5", "0.7", "1", and "1.6".

[0052] As shown in Figure 8, when the misalignment of the detection centers of the two magnetic detection elements 8α and 8β is changed from 0, the output values ​​S of the two magnetic detection elements 8α and 8β change. α ,S β The phase difference changes from 90°. Also, the slope of the phase error near dx=0 decreases in the order of ratio Dy / Dx being "0.5", "1.6", "0.7", and "1". In other words, by making the second axis distance Dy and the first axis distance Dx approximately equal, the slope of the phase error near dx=0 can be minimized. Therefore, by integrating the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β, and further setting the second axis distance Dy between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w) within a predetermined allowable installation error ±Δy (Dx-Δy≦Dy≦Dx+Δy) centered on the first axis distance Dx between the β-axis magnetic detection element 8β and the U-phase current line 6u (or W-phase current line 6w), the positional misalignment toughness of the two magnetic detection elements 8α and 8β along the first virtual line L1 can be improved. In other words, the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β are integrated, and the detection center of the β-axis magnetic detection element 8β is set to the magnetic sensitivity coefficient k of the U-phase current line 6u (or W-phase current line 6w) of the β-axis magnetic detection element 8β on the second virtual line L2. βu (or magnetic sensitivity coefficient k) βw By positioning the two magnetic detection elements 8α and 8β within a range of allowable installation error ±Δy centered on the position where the value is maximum (or minimum), the positional misalignment toughness along the first virtual line L1 can be improved.

[0053] In addition to the effects described in (1) to (3) above, the current detection device according to this embodiment provides the following effects.

[0054] (4) In this embodiment, by integrating the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β, the amount of positional displacement of these magnetic detection elements 8α and 8β with respect to the respective phase current lines 6u, 6v, and 6w can be made equal. Furthermore, as described above, in the state in which these magnetic detection elements 8α and 8β are integrated, the output value S of these magnetic detection elements 8α and 8β with respect to the positional displacement of the detection center of these magnetic detection elements 8α and 8β along the first virtual line L1 can be made equal. α ,S β The variation in phase error between these magnetic detection elements 8α and 8β is minimized when the second axial distance Dy and the first axial distance Dx between the detection centers of these magnetic detection elements 8α and 8β and the U-phase current line 6u (or W-phase current line 6w) are made approximately equal. Therefore, according to this embodiment, the positional misalignment toughness along the first virtual line L1 for each phase current line 6u, 6v, and 6w of these magnetic detection elements 8α and 8β can be improved.

[0055] 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]

[0056] V...vehicle W…Drive wheels M...Motor (three-phase motor) 6u…U phase current line (1st phase current line) 6v…V phase current line (2nd phase current line) 6w…W phase current line (3rd phase current line) 1…Inverter (power supply) 2…Motor control device 21…AD conversion unit 22...Current value acquisition unit 23...dq conversion section 24... Duty Calculation Unit 3…Current detection device 8α...α-axis magnetic detection element Oα...Detection axis Pα…α-axis element arrangement surface 8β…β-axis magnetic detection element Oβ...Detection axis Pβ,Pβ´…β-axis element arrangement surface L1…First virtual line L2…Second virtual line 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, The α-axis magnetic detection element provided around the first, second, and third phase current lines, The system comprises a β-axis magnetic detection element provided around the first and third phase current lines, The detection axis of the β-axis magnetic detection element is orthogonal to both the first and third phase current lines and is arranged so as to be orthogonal to a first virtual line connecting the first and third phase current lines in the β-axis element arrangement plane including the detection center of the β-axis magnetic detection element. The detection center of the β-axis magnetic detection element is positioned on a second virtual line that is perpendicular to the first virtual line and passes through the midpoint of the first virtual line. A current detection device characterized in that the distance along the second virtual line between the detection center of the β-axis magnetic detection element and the first phase current line is within a predetermined allowable installation error range centered on the distance along the first virtual line between the detection center of the β-axis magnetic detection element and the first phase current line.

2. 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, The α-axis magnetic detection element provided around the first, second, and third phase current lines, The system comprises a β-axis magnetic detection element provided around the first and third phase current lines, The detection axis of the β-axis magnetic detection element is orthogonal to both the first and third phase current lines and is arranged so as to be orthogonal to a first virtual line connecting the first and third phase current lines in the β-axis element arrangement plane including the detection center of the β-axis magnetic detection element. The current detection device is characterized in that the detection center of the β-axis magnetic detection element is positioned within a predetermined allowable installation error range centered on a second virtual line that is orthogonal to the first virtual line and passes through the midpoint of the first virtual line, where the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the first phase current line is at its maximum or minimum value.

3. The current detection device according to claim 1 or 2, characterized in that the detection center of the α-axis magnetic detection element is arranged in an α-axis element arrangement plane that is perpendicular to the first, second and third phase current lines and different from the β-axis element arrangement plane.

4. The current detection device according to claim 1 or 2, characterized in that the α-axis magnetic detection element and the β-axis magnetic detection element are integrated.

5. The current detection device according to claim 3, characterized in that the α-axis magnetic detection element and the β-axis magnetic detection element are integrated.

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