Current detection device

Abstract

To provide a current detection device for a three-phase motor that can reduce a calculation load in a downstream motor control device for performing vector control.SOLUTION: A current detection device includes two magnetic detection elements Sα and Sβ arranged around three phase current lines 6u, 6v, and 6w, and a current correction calculation unit 22 that multiplies output values (Vα, Vβ) of the magnetic detection elements Sα and Sβ by α-phase and β-phase gains (Gα, Gβ) and outputs the results as α-phase and β-phase current values (Iα, Iβ). The relative positions and detection axis directions of the two magnetic detection elements Sα and Sβ with respect to the three phase current lines 6u, 6v, and 6w are determined such that an α-phase layout condition equation and a β-phase layout condition equation which are determined using a coefficient X other than -1 / 2 are satisfied, and the values of the α-phase and β-phase gains (Gα, Gβ) are set such that the amplitudes of the α-phase and β-phase current values (Iα, Iβ) are equal to each other.SELECTED DRAWING: Figure 4

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 research and development into electric vehicles is being conducted to reduce CO2 emissions and improve energy efficiency.

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

[0004] [Patent Document 1] International Publication No. 2013 / 058282 [Patent Document 2] Chinese patent application CN202211040361.X Summary of the Invention [Problem to be solved by the invention]

[0005] In this way, motor control devices perform feedback control of current on the dq coordinate system, and therefore require the motor's U-, V-, and W-phase currents, detected using a current detection device such as that described in Patent Document 1, to be converted into d-axis and q-axis currents. More specifically, the motor control device first converts the three-phase currents (Iu, Iv, Iw) detected by the current detection device into two-phase currents (Iα, Iβ) defined in a fixed coordinate system using Clarke transformation, and then converts these two-phase currents (Iα, Iβ) into two-phase currents (Id, Iq) defined in the dq coordinate system using Park transformation using the motor's rotation angle θ. In this way, vector control using the output of a conventional current detection device requires the motor control device to perform calculations to convert the three-phase currents (Iu, Iv, Iw) into two-phase currents (Id, Iq).

[0006] Furthermore, Patent Document 2 filed by the applicant of the present application describes a technique for directly obtaining two-phase currents (Iα, Iβ) without undergoing Clarke transform calculations using a computer by providing two magnetic detection elements at geometrically determined positions around three phase current lines (hereinafter, this technique will also be referred to as the "spatial Clarke transform"). This spatial Clarke transform can reduce the number of magnetic detection elements and the computational load on the computer compared to conventional techniques.

[0007] However, the spatial Clarke transform disclosed in Patent Document 2 limits the number of layout patterns for the three phase current lines and two magnetic detection elements to just a few. Because an electric vehicle requires efficient layout of various components, it is preferable to have as much freedom as possible in the layout of the phase current lines and magnetic detection elements.

[0008] 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]

[0009] (1) A current detection device (for example, a current detection device 3 described later) according to the present invention detects currents flowing through a first current line (for example, a U-phase current line 6u described later), a second-phase current line (for example, a V-phase current line 6v described later), and a third-phase current line (for example, a W-phase current line 6w described later) of a three-phase motor (for example, a motor M described later). The current detection device detects currents flowing through a first current line (for example, a U-phase current line 6u described later), a second-phase current line (for example, a V-phase current line 6v described later), and a third-phase current line (for example, a W-phase current line 6w described later) of a three-phase motor. The current detection device detects currents flowing through an α-phase magnetic detection element (for example, an α-phase magnetic detection element Sα described later) and a β-phase magnetic detection element (for example, a β-phase magnetic detection element Sβ described later) provided around the first, second, and third-phase current lines. The current detection device calculates an α-phase current value (for example, an α-phase current value Iα described later) by multiplying the output values of the α-phase and β-phase magnetic detection elements by an α-phase gain (for example, an α-phase gain Gα described later) and a β-phase gain (for example, a β-phase gain Gβ described later). and a calculation means (e.g., a current correction calculation unit 22 described later) for outputting a β-phase current value (e.g., a β-phase current value Iβ described later), wherein, when the current value flowing through the first-phase current line is I1, the current value flowing through the second-phase current line is I2, the current value flowing through the third-phase current line is I3, the output value of the α-phase magnetic detection element is Vα, and the output value of the β-phase magnetic detection element is Vβ, the relative positions and directions of the detection axes of the α-phase and β-phase magnetic detection elements with respect to the first-phase, second-phase, and third-phase current lines are determined so that the following equations (1-1) and (1-2) are satisfied, which are determined using a coefficient X other than "-1 / 2", and the values of the α-phase and β-phase gains are set so that the amplitudes of the α-phase and β-phase current values are equal.

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[0010] (2) In this case, the α-phase and β-phase magnetic detection elements are preferably provided in the same arrangement plane (for example, arrangement plane P described below) that is perpendicular to the first, second, and third phase current lines.

[0011] (3) In this case, it is preferable that the α-phase magnetic detection element is arranged on a virtual arrangement line (e.g., the α-phase arrangement line Lα described later) that is perpendicular to a line segment (e.g., the line segment L1 described later) connecting the second phase current line and the third phase current line within the arrangement plane and bisects the line segment.

[0012] (4) In this case, it is preferable that the first phase current line is perpendicular to the arrangement plane at the intersection of the line segment and the arrangement line, and the direction of the DC current flowing through the first, second, and third phase current lines from the power source toward the three-phase motor is the same on the arrangement plane.

[0013] (5) In this case, it is preferable that the β-phase magnetic detection elements are arranged on the arrangement line within the arrangement plane.

[0014] (6) In this case, the β-phase magnetic detection element is preferably arranged on the arrangement line so that its detection axis (for example, a detection axis Oβ described later) is parallel to the arrangement line. [Effects of the Invention]

[0015] (1) In the current detection device according to the present invention, currents flowing through three current lines are detected using two magnetic detection elements arranged around these current lines. Therefore, the number of magnetic detection elements can be reduced compared to conventional current detection devices that provide one magnetic detection element for each current line, thereby reducing costs. In the current detection device according to the present invention, the relative positions and detection axis directions of the α-phase and β-phase magnetic detection elements with respect to the first to third phase current lines are determined so that the above-mentioned equations (1-1) and (1-2) hold, which are determined using a coefficient X other than "-1 / 2." Meanwhile, in the spatial Clarke transformation described in Chinese Patent Application CN202211040361.X (hereinafter simply referred to as the "prior application") filed by the present applicant, the relative positions and detection axis directions of the α-phase and β-phase magnetic detection elements with respect to the first to third phase current lines are determined so that a matrix equation equivalent to the Clarke transformation (i.e., the case where X = 1 in the above-mentioned equations (1-1) and (1-2)) holds. Therefore, according to the present invention, the above equations (1-1) and (1-2) include an arbitrary coefficient X, which allows for a higher degree of freedom in the layout of the three phase current lines and two magnetic detection elements than the conventional spatial Clarke transform.

[0016] As will be described in detail later, the current obtained by multiplying three-phase currents (I1, I2, I3) whose phases differ by 2π / 3 by the transformation matrix (X, -1 / 2, -1 / 2) described in the above formula (1-1) differs only in amplitude but in phase from the current obtained by multiplying the three-phase currents (I1, I2, I3) by the first-row elements (1, -1 / 2, -1 / 2) of the Clarke transformation transformation matrix. This means that the output value Vα of the α-phase magnetic detection element configured to satisfy the above formula (1-1) can be made equal to the output value of the magnetic detection element described in the prior application by multiplying it by a predetermined gain. Therefore, in the present invention, the calculation means multiplies the output values of the α-phase and β-phase magnetic detection elements by the α-phase and β-phase gains, respectively, and outputs the results as α-phase and β-phase current values. The α-phase and β-phase gain values are set so that the amplitudes of the α-phase and β-phase current values are equal. Therefore, in the current detection device of the present invention, the difference in amplitude between the output values of the two magnetic detection elements, which is caused by the coefficient X included in the above equation (1-1), can be eliminated by calculation in the calculation means. Therefore, according to the present invention, by using the α-phase and β-phase current values output from the calculation means, the motor control device provided downstream does not need to perform Clarke transform by calculation, which reduces the calculation load of the motor control device and ultimately contributes to improving energy efficiency.

[0017] (2) In the present invention, by arranging the α-phase and β-phase magnetic detection elements in an arrangement plane perpendicular to the three phase current lines, the two magnetic detection elements can be compactly arranged around the three phase current lines while satisfying the above equations (1-1) and (1-2).

[0018] (3) In the present invention, the α-phase magnetic detection element is arranged on a virtual arrangement line that is perpendicular to the line segment connecting the second and third phase current lines within the arrangement plane and bisects this line segment, so that the α-phase magnetic detection element can be arranged at any position required while satisfying the above equations (1-1) and (1-2).

[0019] (4) In the present invention, by arranging the first, second, and third phase current lines side by side, the three phase current lines can be compactly arranged while satisfying the above formulas (1-1) and (1-2). Note that while the spatial Clarke transformation described in the prior application also allows three phase current lines to be arranged side by side, the orientation of the central phase current line must be reversed from that of the other two (see Figures 4 and 5 of the prior application), and therefore the phase current lines must be twisted. In contrast, according to the present invention, the three phase current lines can be arranged side by side without twisting them.

[0020] (5) In the present invention, by arranging three phase current lines side by side and further providing α-phase and β-phase magnetic detection elements on an arrangement line passing through the central first phase current line, it is possible to compactly arrange the three phase current lines and two magnetic detection elements while satisfying the above equations (1-1) and (1-2).

[0021] (6) In the present invention, by arranging the β-phase magnetic detection element on the arrangement line so that its detection axis is parallel to the arrangement line, the β-phase magnetic detection element can be arranged close to the first phase current line while preventing the influence of the current flowing through the first phase current line from affecting the β-phase magnetic detection element. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram showing the configuration of a current detection device according to an embodiment of the present invention and an electric vehicle equipped with this current detection device; [Figure 2] 10 is a diagram for explaining the arrangement range of the α-phase magnetic detection element that satisfies the α-phase layout conditional expression. FIG. [Figure 3] 10 is a diagram for explaining the arrangement range of the β-phase magnetic detection elements that satisfies the β-phase layout conditional expression; FIG. [Figure 4] FIG. 10 is a diagram showing a first example of a layout of three phase current lines and two magnetic detection elements that satisfies both the α-phase and β-phase layout conditional expressions within the layout plane. [Figure 5]FIG. 10 is a diagram showing a second example of a layout of three phase current lines and two magnetic detection elements that satisfies both the α-phase and β-phase layout conditional expressions within the layout plane. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A current detection device according to an embodiment of the present invention and an electric vehicle equipped with the current detection device will be described below with reference to the drawings.

[0024] 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 the following description will be made on the case where the current detection device 3 is mounted on an electric vehicle V, but the present invention is not limited to this. In addition to the electric vehicle V, the current detection device 3 can also be mounted on any device that controls a three-phase motor based on vector control, such as an air conditioner or a washing machine.

[0025] 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 sensor unit S that generates a signal according 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 of the sensor unit S and the resolver 4.

[0026] The inverter 1 is, for example, a pulse-width modulated PWM inverter equipped with a bridge circuit formed by bridge-connecting a plurality of switching elements (e.g., IGBTs), and has the function of converting DC power and AC power. The inverter 1 is connected to a battery on its DC input / output side and to the U-, V-, and W-phase coils of the motor M on its AC input / output side, and converts power between the battery and the motor M. The inverter 1 converts DC power supplied from the battery into AC power and supplies it to the motor M, or converts AC power supplied from the motor M into DC power and supplies it to the battery, by driving the switching elements of each phase on / off in accordance with gate drive signals generated at predetermined timing by a gate drive circuit (not shown).

[0027] The sensor unit S includes an α-phase magnetic detection element Sα and a β-phase magnetic detection element Sβ arranged 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. These magnetic detection elements Sα and Sβ generate detection signals corresponding to components of the magnetic flux density along each detection axis of the magnetic field generated by the current flowing through each of the phase current lines 6u, 6v, and 6w. Specific examples of the layout of these α-phase and β-phase magnetic detection elements Sα and Sβ and the three phase current lines 6u, 6v, and 6w will be described later with reference to FIGS. 2 to 5.

[0028] The motor control device 2 is a computer that performs vector control based on detection signals from two magnetic detection elements Sα and Sβ and a resolver 4, thereby generating a drive signal for the gate drive circuit of the inverter 1 and inputting it to the gate drive circuit.

[0029] The motor control device 2 includes an AD conversion unit 21, a current correction calculation unit 22, a dq conversion unit 23, and a duty calculation unit 24 as modules related to the execution of the above-mentioned vector control.

[0030] The AD conversion unit 21 performs AD conversion on the detection signals of the α-phase and β-phase magnetic detection elements Sα and Sβ to obtain output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα and Sβ.

[0031] The current correction calculation unit 22 multiplies the output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα, Sβ acquired by the AD conversion unit 21 by the α-phase gain Gα and the β-phase gain Gβ, respectively, and outputs the results as the α-phase current value Iα and the β-phase current value Iβ, as shown in the following equation (2). Note that the values of these α-phase and β-phase gains (Gα, Gβ) are set so that the amplitudes of the α-phase and β-phase current values (Iα, Iβ) are equal.

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[0032] As will be described below, the α-phase and β-phase current values (Iα, Iβ) calculated by the current correction calculation unit 22 are proportional to the two-phase currents (Iα_ideal, Iβ_ideal) obtained by multiplying the three-phase currents (Iu, Iv, Iw) of the motor M by a 2-by-3 Clarke transformation matrix as shown in the following equation (3). In the following description, the current value flowing through the U-phase current line 6u is referred to as Iu, the current value flowing through the V-phase current line 6v is referred to as Iv, and the current value flowing through the W-phase current line 6w is referred to as Iw. Therefore, in the motor control device 2, when the dq transformation unit 23 (described later) calculates the two-phase currents (Id, Iq) in the dq coordinate system, it is not necessary to perform calculations using the Clarke transformation matrix shown in the following equation (3). This reduces the calculation load on the motor control device 2 compared to conventional methods. 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 Sα and Sβ, an AD conversion unit 21, and a current correction calculation unit 22.

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[0033] The dq conversion unit 23 performs a known calculation using the output values (Iα, Iβ) of the current correction calculation unit 22 and the detection signal of the resolver 4 to calculate the d-axis current Id and the q-axis current Iq.

[0034] The duty calculation unit 24 acquires the d-axis current command Idc and the q-axis current command Iqc according to the driving force required by the driver, and performs feedback control based on the deviation of these current values (Idc-Id, Iqc-Iq) to generate a driving signal for the gate drive circuit of the inverter 1 so as to realize the driving force required by the driver, and inputs the signal to the gate drive circuit.

[0035] Next, a description will be given of the conditions imposed on the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ in order to establish the above formula (3).

[0036] First, as described above, the current correction calculation unit 22 calculates the α-phase and β-phase current values (Iα, Iβ) so that their amplitudes are equal by multiplying the output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα and Sβ by the α-phase and β-phase gains (Gα, Gβ). Therefore, the phase difference between the output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα and Sβ must be equal to the phase difference between the two-phase currents (Iα_ideal, Iβ_ideal) obtained by the above equation (3). However, the amplitudes of these output values (Vα, Vβ) may be different. In other words, the difference in amplitude between these output values (Vα, Vβ) can be eliminated by adjusting the values of the α-phase and β-phase gains (Gα, Gβ) in the current correction calculation unit 22. Therefore, if the three phase current lines 6u, 6v, 6w and the two magnetic detection elements Sα, Sβ are arranged so that the following equations (4-1) and (4-2), which are imposed separately on the two output values (Vα, Vβ), hold, the above equation (3) can be established.

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[0037] As will be explained later, assuming that the current values (Iu, Iv, Iw) flowing through the phase current lines 6u, 6v, and 6w have a phase difference of 2π / 3, the above equations (4-1) and (4-2) can be generalized using an arbitrary coefficient X to give the following equations (5-1) and (5-2). Therefore, in this embodiment, the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ (i.e., the layout of the three phase current lines 6u, 6v, and 6w and the relative positions and detection axis directions of the two magnetic detection elements Sα and Sβ with respect to these phase current lines 6u, 6v, and 6w) is determined so that the following equations (5-1) and (5-2), which are determined using a coefficient X other than "-1," hold. In a layout where the value of coefficient X in equation (5-1) is "-1 / 2," the output value of the magnetic detection element Sα is theoretically always "0." Therefore, in the following formula (5-1), layouts in which the value of the coefficient X is "-1 / 2" are excluded.

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[0038] Next, we will explain why the above formula (4-1) can be generalized to the above formula (5-1). First, the output value Vα′ of the α-phase magnetic detection element Sα when the α-phase magnetic detection element Sα and the three phase current lines 6u, 6v, and 6w are respectively arranged at arbitrary positions is expressed by the following formula (6) using arbitrary coefficients (X, A, and B). Here, the values of the coefficients (X, A, and B) vary depending on the relative position and the direction of the detection axis of the α-phase magnetic detection element Sα with respect to the three phase current lines 6u, 6v, and 6w. More specifically, the value of coefficient X is determined depending on the relative position and the direction of the detection axis of the α-phase magnetic detection element Sα with respect to the U-phase current line 6u. The value of coefficient A is determined depending on the relative position and the direction of the detection axis of the α-phase magnetic detection element Sα with respect to the V-phase current line 6v. The value of coefficient B is determined depending on the relative position and the direction of the detection axis of the α-phase magnetic detection element Sα with respect to the W-phase current line 6w.

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[0039] Furthermore, assuming that the current values (Iu, Iv, Iw) flowing through the respective phase current lines 6u, 6v, 6w have a phase difference of 2π / 3 with the U phase as the reference, the following equation (7) can be derived from the above equation (6) by the addition theorem. In the following equation (7), Iu = sinθ, Iv = sin(θ - 2π / 3), and Iw = sin(θ + 2π / 3).

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[0040] Here, in the above equation (7), if we assume A = B, as in the above equation (4-1), the following equation (8) can be derived. Note that the assumption of A = B corresponds to arranging the phase current lines 6v, 6w and the α-phase magnetic detecting element Sα at positions where the distance between the V-phase current line 6v and the α-phase magnetic detecting element Sα is equal to the distance between the W-phase current line 6w and the α-phase magnetic detecting element Sα, and where the angle formed by the line segment connecting the V-phase current line 6v and the α-phase magnetic detecting element Sα and the detection axis of the α-phase magnetic detecting element Sα is equal to the angle formed by the line segment connecting the W-phase current line 6w and the α-phase magnetic detecting element Sα and the detection axis of the α-phase magnetic detecting element Sα.

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[0041] As shown in Equation (8), assuming A = B, the cosθ term disappears from Equation (7), and the output value Vα′ of the α-phase magnetic detection element Sα is proportional only to sinθ. This means that, within the range where A = B, the phase of the output value Vα′ does not change regardless of how the relative position and the orientation of the detection axis of the α-phase magnetic detection element Sα with respect to the U-phase current line 6u change (i.e., how the value of X changes). In other words, within the range where A = B, only the amplitude of the output value Vα′ changes regardless of how the relative position and the orientation of the detection axis of the α-phase magnetic detection element Sα with respect to the U-phase current line 6u change (i.e., how the value of X changes). Note that, as shown in Equation (8), if the α-phase magnetic detection element Sα is positioned where all the coefficients are equal (i.e., where X = A = B), the output value Vα′ is steadily zero. For the above reasons, the above equation (4-1) can be generalized as shown in the above equation (5-1) by using any coefficient X except "-1 / 2".

[0042] Next, we will explain the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ that satisfies the above equations (5-1) and (5-2). Hereinafter, the above equation (5-1) imposed on the output value Vα of the α-phase magnetic detection element Sα will be referred to as the α-phase layout condition equation, and the above equation (5-2) imposed on the output value Vβ of the β-phase magnetic detection element Sβ will be referred to as the β-phase layout condition equation. Hereinafter, we will explain the case where the two magnetic detection elements Sα and Sβ are both arranged in the same layout plane that is perpendicular to the three phase current lines 6u, 6v, and 6w, but the present invention is not limited to this. These two magnetic detection elements Sα and Sβ may also be arranged in different layout planes.

[0043] FIG. 2 is a schematic diagram illustrating an arrangement plane P of two magnetic detection elements Sα and Sβ that are perpendicular to the three phase current lines 6u, 6v, and 6w. More specifically, FIG. 2 illustrates an arrangement range of the α-phase magnetic detection elements Sα within the arrangement plane P that satisfies the α-phase layout conditional expression (5-1). Note that FIG. 2 illustrates a case in which the three phase current lines 6u, 6v, and 6w are arranged at equal intervals in the arrangement plane P in the order of the V-phase current line 6v, the U-phase current line 6u, and the W-phase current line 6w. However, the present invention is not limited to this arrangement. Also, FIG. 2 illustrates a case in which the DC currents flowing through the phase current lines 6u, 6v, and 6w from the inverter 1, which serves as the power source, toward the motor M are aligned in the same direction within the arrangement plane P. Also, the β-phase magnetic detection element Sβ is not illustrated in FIG. 2 for ease of understanding.

[0044] First, to satisfy the α-phase layout condition formula (5-1), the α-phase magnetic detection element Sα needs to be arranged on an imaginary α-phase arrangement line Lα that is perpendicular to an imaginary line L1 connecting the V-phase current line 6v and the W-phase current line 6w within the arrangement plane P and that bisects this line L1. In other words, the α-phase magnetic detection element Sα needs to be arranged at a position (i.e., on the α-phase arrangement line Lα) such that the distance within the arrangement plane P between the V-phase current line 6v and the W-phase current line 6w is equal.

[0045] Furthermore, to satisfy the α-phase layout condition formula (5-1), the detection axis Oα of the α-phase magnetic detection element Sα must be perpendicular to the α-phase layout line Lα within the layout plane P, as shown in Figure 2. However, in this case, if the α-phase magnetic detection element Sα is placed at the intersection of the line segment L1 and the α-phase layout line Lα, the detection axis Oα will be perpendicular to the magnetic flux formed by the phase current lines 6v and 6w. For this reason, the α-phase magnetic detection element Sα must be placed at a position on the α-phase layout line Lα other than the intersection with the line segment L1.

[0046] As mentioned above, the α-phase layout condition formula (5-1) includes an optional coefficient X. Therefore, the U-phase current line 6u may be located anywhere within the layout plane P, except for the dead point P0 where the coefficient X is -1 / 2. That is, the U-phase current line 6u is not limited to the midpoint of the line segment L1 shown in FIG. 2. For example, the α-phase layout condition formula (5-1) can be established even if the U-phase current line 6u is located at a position such as points P1, P2, P3, or P4 within the layout plane P. The dead point P0 is the location of the U-phase current line 6u where the output value Vα of the α-phase magnetic detection element Sα is steadily zero, as mentioned above. When the α-phase magnetic detection element Sα and the v-phase and w-phase current lines 6v and 6w are located as shown in FIG. 2, the dead point P0 appears on the α-phase layout line Lα, as shown in FIG. 2.

[0047] 3 is a diagram schematically illustrating an arrangement plane P of two magnetic detection elements Sα and Sβ that are perpendicular to the three phase current lines 6u, 6v, and 6w. More specifically, FIG. 3 is a diagram for explaining the arrangement range of the β-phase magnetic detection element Sβ that satisfies the β-phase layout condition formula (5-2) within the arrangement plane P. Note that the α-phase magnetic detection element Sα is not shown in FIG. 3 to facilitate understanding.

[0048] First, in order to satisfy the β-phase layout condition formula (5-2), the β-phase magnetic detection element Sβ must be arranged on the α-phase layout line Lα, similar to the α-phase magnetic detection element Sα, within the layout plane P. In other words, the β-phase magnetic detection element Sβ must be arranged at a position (i.e., on the α-phase layout line Lα) such that the distance within the layout plane P between the V-phase current line 6v and the W-phase current line 6w is equal.

[0049] Furthermore, to satisfy the β-phase layout condition formula (5-2), the detection axis Oβ of the β-phase magnetic detection element Sβ must be perpendicular to the magnetic flux formed by the current flowing through the U-phase current line 6u. Therefore, when the three phase current lines 6u, 6v, and 6w are arranged at equal intervals as shown in Figure 3, in order to satisfy the β-phase layout condition formula (5-2), the detection axis Oβ of the β-phase magnetic detection element Sβ must be parallel to the α-phase layout line Lα within the layout plane P, as shown in the example of Figure 3. Therefore, by arranging the β-phase magnetic detection element Sβ on the α-phase layout line Lα so that its detection axis Oβ is parallel to the α-phase layout line Lα, the β-phase layout condition formula (5-2) can be satisfied.

[0050] Fig. 4 is a diagram showing a first example of the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ that satisfies both the α-phase layout conditional formula (5-1) and the β-phase layout conditional formula (5-2) within the layout plane P. Fig. 4 shows the case where the three phase current lines 6u, 6v, and 6w are arranged side by side at equal intervals, as described with reference to Figs.

[0051] When the three phase current lines 6u, 6v, and 6w are arranged at equal intervals in this manner, the α-phase layout condition formula (5-1) can be satisfied by arranging the α-phase magnetic detection element Sα on the α-phase layout line Lα so that its detection axis Oα is perpendicular to the α-phase layout line Lα. Also, the β-phase magnetic detection element Sβ can be arranged on the α-phase layout line Lα so that its detection axis Oβ is parallel to the β-phase layout line Lβ, so that the β-phase layout condition formula (5-2) can be satisfied.

[0052] 5 is a diagram showing a second example of the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ that satisfies both the α-phase layout conditional formula (5-1) and the β-phase layout conditional formula (5-2) within the layout plane P. Note that Fig. 5 shows a case where the phase current lines 6u, 6v, and 6w are arranged at the corners of an isosceles triangle with the U-phase current line 6u as the apex angle.

[0053] 5, even when the three phase current lines 6u, 6v, and 6w are arranged at the corners of an isosceles triangle within the arrangement plane P, the α-phase layout condition formula (5-1) can be satisfied by arranging the α-phase magnetic detection element Sα on the α-phase arrangement line Lα so that its detection axis Oα is perpendicular to the α-phase arrangement line Lα. Also, the β-phase layout condition formula (5-2) can be satisfied by arranging the β-phase magnetic detection element Sβ on the α-phase arrangement line Lα so that its detection axis Oβ is parallel to the β-phase arrangement line Lβ.

[0054] The current detecting device 3 according to this embodiment has the following advantages. (1) The current detection device 3 detects the currents flowing through the three phase current lines 6u, 6v, and 6w based on two magnetic detection elements Sα and Sβ arranged around the three phase current lines 6u, 6v, and 6w. Therefore, the current detection device 3 can reduce the number of magnetic detection elements compared to conventional current detection devices that provide one magnetic detection element for each current line, thereby reducing costs. Furthermore, in the current detection device 3, the relative positions and detection axis directions of the α-phase and β-phase magnetic detection elements Sα and Sβ with respect to the three phase current lines 6u, 6v, and 6w are determined so that the α-phase layout conditional equation (5-1) and the β-phase layout conditional equation (5-2), which are determined using a coefficient X other than "-1 / 2," are satisfied. Therefore, according to the current detection device 3, the above equations (5-1) and (5-2) include an arbitrary coefficient X, which allows for a higher degree of freedom in the layout of the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ than the spatial Clarke transformation described in the previous application by the applicant of the present application.

[0055] As described above, the current obtained by multiplying the three-phase currents (Iu, Iv, Iw) whose phases differ by 2π / 3 by the transformation matrix (X, -1 / 2, -1 / 2) defined in the α-phase layout conditional formula (5-1) differs only in amplitude from the current obtained by multiplying the three-phase currents (Iu, Iv, Iw) by the first-row elements (1, -1 / 2, -1 / 2) of the Clarke transformation transformation matrix. This means that the output value Vα of the α-phase magnetic detection element Sα, which is arranged so that the α-phase layout conditional formula (5-1) is satisfied, can be made equal to the output value of the first magnetic detection element described in the prior application by multiplying it by a predetermined gain. Therefore, in the current detection device 3, the current correction calculation unit 22 multiplies the output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα and Sβ, respectively, by the α-phase and β-phase gains (Gα, Gβ), and outputs the results as the α-phase and β-phase current values (Iα, Iβ). The values of the α-phase and β-phase gains (Gα, Gβ) are set so that the amplitudes of the α-phase and β-phase current values (Iα, Iβ) are equal. Therefore, in the current detection device 3, the difference in amplitude between the output values (Vα, Vβ) of the two magnetic detection elements Sα and Sβ, which is caused by the coefficient X included in the α-phase layout conditional equation (5-1), can be eliminated by calculation in the current correction calculation unit 22. Therefore, in the current detection device 3, by using the α-phase and β-phase current values (Iα, Iβ) output from the current correction calculation unit 22, the dq transformation unit 23 provided downstream does not need to perform Clarke transformation by calculation. This reduces the calculation load of the motor control device 2, which in turn contributes to improving energy efficiency.

[0056] (2) In the current detection device 3, the α-phase and β-phase magnetic detection elements Sα and Sβ are arranged within an arrangement plane P that is perpendicular to the three phase current lines 6u, 6v, and 6w. This allows the two magnetic detection elements Sα and Sβ to be compactly arranged around the three phase current lines 6u, 6v, and 6w while satisfying the α-phase layout condition equation (5-1) and the β-phase layout condition equation (5-2).

[0057] (3) In the current detection device 3, the α-phase magnetic detection element Sα is arranged on a virtual α-phase arrangement line Lα that is perpendicular to the line segment L1 connecting the v-phase and w-phase current lines 6v, 6w within the arrangement plane P and bisects this line segment L1, so that the α-phase magnetic detection element Sα can be arranged at any position required while satisfying the α-phase layout condition equation (5-1) and the β-phase layout condition equation (5-2).

[0058] (4) In the current detection device 3, by arranging the three phase current lines 6u, 6v, and 6w side by side, the three phase current lines 6u, 6v, and 6w can be compactly arranged while satisfying the α-phase layout conditional expression (5-1) and the β-phase layout conditional expression (5-2). Note that while the spatial Clarke transformation described in the prior application also allows the three phase current lines 6u, 6v, and 6w to be arranged side by side, the orientation of the central U-phase current line 6u must be reversed from the orientation of the other two current lines (see Figures 4 and 5 of the prior application), and therefore the U-phase current line 6u must be twisted. In contrast, the current detection device 3 allows the three phase current lines 6u, 6v, and 6w to be arranged side by side without twisting them.

[0059] (5) In the current detection device 3, the three phase current lines 6u, 6v, and 6w are arranged side by side, and the α-phase and β-phase magnetic detection elements Sα and Sβ are provided on the α-phase layout line Lα that passes through the central U-phase current line 6u. This makes it possible to compactly arrange the three phase current lines 6u, 6v, and 6w and the two magnetic detection elements Sα and Sβ while satisfying the α-phase layout condition equation (5-1) and the β-phase layout condition equation (5-2).

[0060] (6) In the current detection device 3, the β-phase magnetic detection element Sβ is arranged on the α-phase arrangement line Lα so that its detection axis Oβ is parallel to the α-phase arrangement line Lα. This prevents the influence of the current flowing through the U-phase current line 6u on the β-phase magnetic detection element Sβ, while allowing the β-phase magnetic detection element Sβ to be arranged close to the U-phase current line 6u.

[0061] Although one embodiment of the present invention has been described above, the present invention is not limited to this, and the detailed configuration may be modified as appropriate within the scope of the spirit of the present invention. [Explanation of symbols]

[0062] 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 section 22...Current correction calculation section (calculation means) 23...dq conversion section 24...Duty calculation section 3...Current detection device Sα...α-phase magnetic detection element Oα…detection axis Sβ...β-phase magnetic detection element Oβ…Detection axis P...Placement surface L1...line segment Lα…α phase arrangement line (arrangement line) 4...Resolver

Claims

1. A current detection device for detecting currents flowing through a first current line, a second phase current line, and a third phase current line of a three-phase motor, an α-phase magnetic detection element and a β-phase magnetic detection element provided around the first-phase, second-phase, and third-phase current lines; a calculation means for multiplying the output values of the α-phase and β-phase magnetic detection elements by an α-phase gain and a β-phase gain, respectively, and outputting the results as an α-phase current value and a β-phase current value, When the value of the current flowing through the first phase current line is I1, the value of the current flowing through the second phase current line is I2, the value of the current flowing through the third phase current line is I3, the output value of the α-phase magnetic detection element is Vα, and the output value of the β-phase magnetic detection element is Vβ, the relative positions and directions of the detection axes of the α-phase and β-phase magnetic detection elements with respect to the first phase, second phase, and third phase current lines are determined so that the following equations (1-1) and (1-2) are satisfied, which are determined using a coefficient X other than "-1 / 2": The current detection device according to claim 1, wherein the values of the α-phase and β-phase gains are set so that the amplitudes of the α-phase and β-phase current values are equal to each other. [Equation 1]

2. 2. The current detection device according to claim 1, wherein the α-phase and β-phase magnetic detection elements are provided in the same layout plane perpendicular to the first, second, and third phase current lines.

3. 3. The current detection device according to claim 2, wherein the α-phase magnetic detection element is arranged on a virtual arrangement line that is perpendicular to a line segment connecting the second-phase current line and the third-phase current line within the arrangement plane and bisects the line segment.

4. the first phase current line is perpendicular to the layout plane at an intersection of the line segment and the layout line; 4. The current detection device according to claim 3, wherein the directions of the direct currents flowing through the first, second and third phase current lines from the power source to the three-phase motor are the same in the layout plane.

5. 5. The current detection device according to claim 4, wherein the β-phase magnetic detection element is arranged on the arrangement line within the arrangement plane.

6. 6. The current detection device according to claim 5, wherein the β-phase magnetic detection element is arranged on the arrangement line so that its detection axis is parallel to the arrangement line.

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