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 flowing through each of phase current lines 6u, 6v, and 6w of a motor M is detected using α-phase and β-phase magnetic detection elements Sα and Sβ which are arranged around the three phase current lines 6u, 6v, and 6w. When an imaginary plane perpendicular to the three phase current lines 6u, 6v, and 6w is defined as an α-phase layout plane Pα, and an imaginary plane that is perpendicular to at least the V-phase and W-phase current lines 6v and 6w, but different from the α-phase layout plane Pα is defined as a β-phase layout plane Pβ, these phase magnetic detection elements Sα and Sβ are arranged at positions on the α-phase and β-phase layout planes Pα and Pβ, respectively, such that an α-phase layout condition equation and a β-phase layout condition equation determined using a coefficient X other than -1 / 2 are satisfied at the positions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and 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) based on 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, and the current value flowing through the first phase current line is I1, the current value flowing through the second phase current line is I2, and When the current value flowing through the third-phase current line is I3, the output value of the α-phase magnetic detection element is Vα, the output value of the β-phase magnetic detection element is Vβ, an imaginary plane perpendicular to the first, second, and third-phase current lines is an α-phase arrangement plane (for example, the α-phase arrangement plane Pα described below), and an imaginary plane perpendicular to at least the second and third-phase current lines and different from the α-phase arrangement plane is a β-phase arrangement plane (for example, the β-phase arrangement plane Pβ described below), the α-phase and β-phase magnetic detection elements are disposed at positions within the α-phase and β-phase arrangement planes, respectively, such that the following equations (1-1) and (1-2), which are determined using a coefficient X other than "-1 / 2", hold.

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[0010] (2) In this case, it is preferable that the α-phase magnetic detection element is arranged on a virtual α-phase arrangement line (e.g., α-phase arrangement line Lα described later) that is perpendicular to an α-phase line segment (e.g., α-phase line L1 described later) connecting the second phase current line and the third phase current line within the α-phase arrangement plane and bisects the α-phase line segment.

[0011] (3) In this case, it is preferable that the first phase current line intersects the α phase layout plane at a point where the α phase line segment and the α phase layout line intersect, 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 α phase layout plane.

[0012] (4) In this case, it is preferable that the first phase current line intersects the α phase arrangement plane at a point other than the α phase arrangement line (for example, points P1, P2, P3, and P4 described below).

[0013] (5) In this case, it is preferable that the β-phase magnetic detection element is arranged on a virtual β-phase arrangement line (e.g., β-phase arrangement line Lβ described below) that is perpendicular to a β-phase line segment (e.g., β-phase line segment L2 described below) connecting the second phase current line and the third phase current line within the β-phase arrangement plane and bisects the β-phase line segment.

[0014] (6) In this case, it is preferable that the distance along the beta phase arrangement surface between the beta phase magnetic detection element and the first phase current line is longer than the distance along the beta phase arrangement surface between the beta phase magnetic detection element and the second or third phase current line.

[0015] (7) In this case, it is preferable that the detection axis of the β-phase magnetic detection element (for example, a detection axis Oβ described later) is perpendicular to the magnetic flux formed in the β-phase arrangement plane by the current flowing through the first phase current line.

[0016] (8) In this case, it is preferable to further provide a calculation means (e.g., a current correction calculation unit 22 described below) that multiplies the output value of the β-phase magnetic detection element by a β-phase gain (e.g., a β-phase gain Gβ described below) and outputs the result as a β-phase current value (e.g., a β-phase current value Iβ described below), and multiplies the output value of the α-phase magnetic detection element by an α-phase gain (e.g., an α-phase gain Gα described below) that has a value different from the β-phase gain and outputs the result as an α-phase current value (e.g., an α-phase current value Iα described below).

[0017] (9) In this case, it is preferable that 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. [Effects of the Invention]

[0018] (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 per current line, thereby reducing costs. Furthermore, in the current detection device according to the present invention, the α-phase and β-phase magnetic detection elements are arranged at positions that satisfy the above equations (1-1) and (1-2), 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-phase to third-phase current lines are determined so that a matrix equation equivalent to the Clarke transformation (i.e., equivalent to the case where X = 1 in the above 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.

[0019] Furthermore, 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 provided so that the above formula (1-1) holds 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, according to the current detection device of the present invention, by using the output values of two magnetic detection elements, the motor control device provided downstream does not need to perform Clarke transformation by calculation. This reduces the calculation load of the motor control device, thereby contributing to improved energy efficiency.

[0020] As shown in the above formula (1-2), the β-phase magnetic detection element must be located so as not to be affected by the current flowing through the first-phase current line. Therefore, if the α-phase and β-phase magnetic detection elements are arranged in the same arrangement plane perpendicular to the three phase current lines so as to satisfy the above formulas (1-1) and (1-2), the location where the β-phase magnetic detection element can be arranged is limited. Therefore, in the present invention, the α-phase magnetic detection element is arranged in the α-phase arrangement plane perpendicular to the first-, second-, and third-phase current lines, and the β-phase magnetic detection element is arranged in a β-phase arrangement plane perpendicular to at least the second- and third-phase current lines and different from the α-phase arrangement plane. Therefore, according to the present invention, the degree of freedom in the layout of the three phase current lines and the two magnetic detection elements can be further improved compared to when two magnetic detection elements are arranged in a common arrangement plane.

[0021] (2) In the present invention, the α-phase magnetic detection element is arranged on a virtual α-phase arrangement line that is perpendicular to the α-phase line connecting the second and third phase current lines within the α-phase arrangement plane and bisects this α-phase line, so that the α-phase magnetic detection element can be arranged at any position required while still satisfying the above formula (1-1).

[0022] (3) In the present invention, by arranging the first, second, and third phase current lines side by side within the α-phase arrangement plane, the three phase current lines can be compactly arranged while satisfying the above formula (1-1). 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 the orientation 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.

[0023] (4) In the present invention, the first phase current line is arranged at a position perpendicular to the α-phase arrangement plane at a point other than the α-phase arrangement line, so that the first phase current line can be arranged at any position while satisfying the above formula (1-1).

[0024] (5) In the present invention, the β-phase magnetic detection element is arranged on a virtual β-phase arrangement line that is perpendicular to the β-phase line connecting the second and third phase current lines within the β-phase arrangement plane and bisects this β-phase line, so that the β-phase magnetic detection element can be arranged at any position required while still satisfying the above equation (1-2).

[0025] (6) In the present invention, by providing the β-phase magnetic detection element at a position within the β-phase arrangement plane such that the first phase current line is farther away than the second or third phase current line, the first phase current line can be arranged at any position required while still satisfying the above formula (1-2).

[0026] (7) In the present invention, by arranging the β-phase magnetic detection element so that its detection axis is perpendicular to the magnetic flux formed in the β-phase arrangement plane by the current flowing through the first phase current line, the β-phase magnetic detection element can be arranged at any position required while still satisfying the above formula (1-2).

[0027] (8) In the present invention, the calculation means calculates the α-phase and β-phase current values by multiplying the output values of the α-phase and β-phase magnetic detection elements by the α-phase and β-phase gains, respectively. Therefore, in the present invention, the calculation by the calculation means can eliminate the difference in amplitude between the output values of the two magnetic detection elements caused by the coefficient X included in the above equation (1-1). Therefore, according to the present invention, the α-phase and β-phase current values can be obtained without performing Clarke transform calculations.

[0028] (9) In the present invention, by setting the values of the α-phase and β-phase gains so that the amplitudes of the α-phase and β-phase current values are equal, the α-phase and β-phase current values can be obtained without performing Clarke transformation calculations. [Brief explanation of the drawings]

[0029] [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]FIG. 1 is a side view of three phase current lines and an α-phase arrangement plane and a β-phase arrangement plane that are orthogonal to these phase current lines. [Figure 3] 10 is a diagram for explaining the arrangement range of the α-phase magnetic detection element that satisfies the α-phase layout conditional expression within the α-phase arrangement surface; FIG. [Figure 4] 10A and 10B are diagrams showing other examples of the arrangement range of the α-phase magnetic detection elements that satisfies the α-phase layout conditional expression within the α-phase arrangement surface; [Figure 5] 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. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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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[0039] 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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[0040] 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.

[0041] 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.

[0042] 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).

[0043] 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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[0044] 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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[0045] 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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[0046] 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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[0047] 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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[0048] 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".

[0049] 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). Note that, 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.

[0050] Fig. 2 is a side view of three phase current lines 6u, 6v, and 6w, as well as an α-phase arrangement plane Pα and a β-phase arrangement plane Pβ that are orthogonal to these phase current lines. Below, as shown in Fig. 2, a case will be described in which the α-phase magnetic detection element Sα is provided in a virtual α-phase arrangement plane Pα that is orthogonal to the three phase current lines 6u, 6v, and 6w, and the β-phase magnetic detection element Sβ is provided in a β-phase arrangement plane Pβ that is orthogonal to at least two phase current lines 6v and 6w and different from the α-phase arrangement plane Pα. However, the present invention is not limited to this. These two magnetic detection elements Sα and Sβ may both be provided in the same α-phase arrangement plane Pα.

[0051] FIG. 3 is a diagram schematically illustrating an α-phase arrangement plane Pα on which the α-phase magnetic detection element Sα is provided. More specifically, FIG. 3 is a diagram illustrating an arrangement range of the α-phase magnetic detection element Sα within the α-phase arrangement plane Pα that satisfies the α-phase layout conditional expression (5-1). Note that FIG. 3 illustrates a case in which the three phase current wires 6u, 6v, and 6w are arranged at equal intervals within the α-phase arrangement plane Pα in the order of the V-phase current wire 6v, the U-phase current wire 6u, and the W-phase current wire 6w. However, the present invention is not limited to this. Also, FIG. 3 illustrates a case in which the DC currents flowing through the phase current wires 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 α-phase arrangement plane Pα. However, the present invention is not limited to this.

[0052] First, to satisfy the α-phase layout condition formula (5-1), the α-phase magnetic detection element Sα must be arranged on an imaginary α-phase arrangement line Lα that is perpendicular to an imaginary α-phase line L1 connecting the V-phase current line 6v and the W-phase current line 6w within the α-phase arrangement plane Pα and that bisects this α-phase line L1. In other words, the α-phase magnetic detection element Sα must be arranged at a position (i.e., on the α-phase arrangement line Lα) such that the distance between the V-phase current line 6v and the W-phase current line 6w within the α-phase arrangement plane Pα is equal.

[0053] 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 α-phase layout plane Pα, as shown in Figure 3. However, in this case, if the α-phase magnetic detection element Sα is placed at the intersection of the α-phase 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 α-phase line segment L1.

[0054] 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 on the α-phase layout plane Pα, 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 α-phase line L1 as shown in FIG. 3. For example, the α-phase layout condition formula (5-1) is satisfied even if the U-phase current line 6u is located at a point other than the α-phase layout plane Lα that intersects the α-phase layout plane Pα at a point perpendicular to the α-phase layout plane Pα, such as points P1, P2, P3, and P4. Here, the dead point P0 is the location of the U-phase current line 6u where the output value Vα of the α-phase magnetic sensor Sα is steadily zero, as mentioned above. When the α-phase magnetic sensor Sα and the v-phase and w-phase current lines 6v and 6w are located as shown in FIG. 3, the dead point P0 appears on the α-phase layout line Lα, as shown in FIG. 3.

[0055] 4 is a diagram showing another example of the arrangement range of the α-phase magnetic detection elements Sα that satisfies the α-phase layout condition formula (5-1) within the α-phase arrangement plane Pα. Unlike the example in FIG. 3, FIG. 4 shows a case in which 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.

[0056] As shown in Figure 4, even when the three phase current lines 6u, 6v, and 6w are arranged at the corners of an isosceles triangle within the α-phase arrangement plane Pα, the α-phase magnetic detection element Sα can be arranged on the α-phase arrangement line Lα so that the detection axis Oα is perpendicular to the α-phase arrangement line Lα, thereby satisfying the α-phase layout condition equation (5-1).

[0057] Fig. 5 is a diagram schematically illustrating a β-phase layout plane Pβ on which the β-phase magnetic detection elements Sβ are provided. More specifically, Fig. 5 is a diagram for explaining the layout range of the β-phase magnetic detection elements Sβ within the β-phase layout plane Pβ that satisfies the β-phase layout conditional expression (5-2). Fig. 5 also illustrates a case in which the DC currents flowing through the phase current lines 6v and 6w from the inverter 1, which serves as the power source, to the motor M are oriented in the same direction on the β-phase layout plane Pβ, but the present invention is not limited to this.

[0058] First, to satisfy the β-phase layout condition formula (5-2), the β-phase magnetic detection element Sβ must be arranged on a virtual β-phase arrangement line Lβ that is perpendicular to a virtual β-phase line L2 connecting the V-phase current line 6v and the W-phase current line 6w within the β-phase arrangement plane Pβ and that bisects the β-phase line L2. In other words, the β-phase magnetic detection element Sβ must be arranged at a position (i.e., on the β-phase arrangement line Lβ) such that the distance between the V-phase current line 6v and the W-phase current line 6w within the β-phase arrangement plane Pβ is equal.

[0059] In addition, 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 β-phase layout line Lβ within the β-phase layout plane Pβ, as illustrated in Figure 5.

[0060] To satisfy the β-phase layout condition (5-2), the β-phase magnetic detection element Sβ must be located at a position where it is not affected by the magnetic flux formed in the β-phase layout plane Pβ by the current flowing through the U-phase current line 6u (not shown). This can be achieved, for example, by making the distance along the β-phase layout plane Pβ between the β-phase magnetic detection element Sβ and the U-phase current line 6u (not shown) sufficiently longer than the distance along the β-phase layout plane Pβ between the β-phase magnetic detection element Sβ and the V-phase current line 6v or the W-phase current line 6w. When the U-phase current line 6u is positioned so as to be perpendicular to the β-phase layout plane Pβ at the intersection P5 between the β-phase line segment L2 and the β-phase layout line Lβ, this can also be achieved by arranging the detection axis Oβ of the β-phase magnetic detection element Sβ parallel to the β-phase layout line Lβ and perpendicular to the magnetic flux formed in the β-phase layout plane Pβ by the current flowing through the U-phase current line 6u.

[0061] 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.

[0062] 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 these 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 α-phase magnetic detection element Sα and the β-phase magnetic detection element Sβ are arranged in positions within the α-phase layout plane Pα and the β-phase layout plane Pβ, respectively, such that the α-phase layout condition formula (5-1) and the β-phase layout condition formula (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.

[0063] Furthermore, 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) described 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, but has the same phase. This means that the output value Vα of the α-phase magnetic detection element Sα, which is provided so as to satisfy the α-phase layout conditional formula (5-1), 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, according to the current detection device 3, by using the output values (Vα, Vβ) of the two magnetic detection elements Sα and Sβ, the motor control device 2 provided downstream does not need to perform Clarke transformation by calculation. This reduces the calculation load of the motor control device 2, thereby contributing to improved energy efficiency.

[0064] As indicated by the β-phase layout condition (5-2), the β-phase magnetic detection element Sβ must be located so as not to be affected by the current flowing through the U-phase current line 6u. Therefore, if the α-phase and β-phase magnetic detection elements Sα and Sβ are located on the same α-phase layout plane Pα that is perpendicular to the three phase current lines 6u, 6v, and 6w so as to satisfy the α-phase layout condition (5-1) and the β-phase layout condition (5-2), the location where the β-phase magnetic detection element Sβ can be located is limited. Therefore, in the current detection device 3, the α-phase magnetic detection element Sα is located on the α-phase layout plane Pα that is perpendicular to the three phase current lines 6u, 6v, and 6w, and the β-phase magnetic detection element Sβ is located on the β-phase layout plane Pβ that is perpendicular to at least the V-phase and W-phase current lines 6v and 6w and that is different from the α-phase layout plane Pα. Therefore, according to the current detection device 3, the degree of freedom in the layout of the three phase current lines 6u, 6v, 6w and the two magnetic detection elements Sα and Sβ can be further improved compared to when the two magnetic detection elements Sα and Sβ are arranged within a common α-phase arrangement plane Pα.

[0065] (2) 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 α-phase line L1 connecting the V-phase and W-phase current lines 6v, 6w within the α-phase arrangement plane Pα and bisects this α-phase line 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).

[0066] (3) In the current detection device 3, by arranging the three phase current wires 6u, 6v, and 6w side by side within the α-phase layout plane Pα, the three phase current wires 6u, 6v, and 6w can be compactly arranged while satisfying the α-phase layout condition formula (5-1). Note that while the spatial Clarke transformation described in the prior application also allows the three phase current wires 6u, 6v, and 6w to be arranged side by side, the orientation of the central U-phase current wire 6u must be reversed from the orientation of the other two (see Figures 4 and 5 of the prior application), and therefore the U-phase current wire 6u must be twisted. In contrast, the current detection device 3 allows the three phase current wires 6u, 6v, and 6w to be arranged side by side without twisting the phase current wires.

[0067] (4) In the current detection device 3, the U-phase current line 6u is arranged at a position perpendicular to the α-phase arrangement plane Pα at a point other than the α-phase arrangement line Lα, so that the U-phase current line 6u can be arranged at any position while satisfying the α-phase layout condition equation (5-1).

[0068] (5) In the current detection device 3, the β-phase magnetic detection element Sβ is arranged on a virtual β-phase arrangement line Lβ that is perpendicular to the β-phase line L2 connecting the V-phase and W-phase current lines 6v, 6w within the β-phase arrangement plane Pβ and bisects this β-phase line L2, thereby making it possible to arrange the β-phase magnetic detection element Sβ at any position required while satisfying the β-phase layout condition equation (5-2).

[0069] (6) In the current detection device 3, by arranging the β-phase magnetic detection element Sβ in a position within the β-phase layout plane Pβ such that the U-phase current line 6u is farther away than the V-phase or W-phase current lines 6v, 6w, the U-phase current line 6u can be positioned freely according to requirements while satisfying the β-phase layout condition equation (5-2).

[0070] (7) In the current detection device 3, by arranging the β-phase magnetic detection element Sβ so that the detection axis Oβ of the β-phase magnetic detection element Sβ is perpendicular to the magnetic flux formed within the β-phase placement plane Pβ by the current flowing through the U-phase current line 6u, the β-phase magnetic detection element Sβ can be arranged at any position required while satisfying the β-phase layout condition equation (5-2).

[0071] (8) In the current detection device 3, the current correction calculation unit 22 calculates the α-phase and β-phase current values (Iα, Iβ) by multiplying the output values (Vα, Vβ) of the α-phase and β-phase magnetic detection elements Sα, Sβ by the α-phase and β-phase gains (Gα, Gβ). Therefore, in the current detection device 3, the calculation in the current correction calculation unit 22 can eliminate the difference in amplitude between the output values (Vα, Vβ) of the two magnetic detection elements Sα, Sβ, which is caused by the coefficient X included in the α-phase layout condition equation (5-1). Therefore, the current detection device 3 can obtain the α-phase and β-phase current values without performing Clarke transform calculations.

[0072] (9) In the current detection device 3, by setting the values of the α-phase and β-phase gains (Gα, Gβ) so that the amplitudes of the α-phase and β-phase current values (Iα, Iβ) are equal, the α-phase and β-phase current values (Iα, Iβ) can be obtained without performing Clarke transformation calculations.

[0073] 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]

[0074] 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 Pα…α phase arrangement surface L1…α phase line segment Lα…α phase arrangement line Sβ...β-phase magnetic detection element Oβ…Detection axis Pβ…β phase arrangement surface L2...β phase line segment Lβ…β phase arrangement line 4...Resolver

Claims

1. A current detection device that detects currents flowing through first, second, and third phase current lines of a three-phase motor based on an α-phase magnetic detection element and a β-phase magnetic detection element provided around the first, second, and third phase current lines, a current detection device characterized in that, when a current value flowing through the first phase current line is I1, a current value flowing through the second phase current line is I2, a current value flowing through the third phase current line is I3, an output value of the α-phase magnetic detection element is Vα, an output value of the β-phase magnetic detection element is Vβ, an imaginary plane orthogonal to the first, second, and third phase current lines is an α-phase arrangement plane, and an imaginary plane orthogonal to at least the second and third phase current lines and different from the α-phase arrangement plane is a β-phase arrangement plane, the α-phase and β-phase magnetic detection elements are respectively disposed in positions within the α-phase and β-phase arrangement plane such that the following equations (1-1) and (1-2) hold, which are determined using a coefficient X other than "-1 / 2": [Equation 1]

2. 2. The current detection device according to claim 1, wherein the α-phase magnetic detection element is arranged on a virtual α-phase arrangement line that is perpendicular to an α-phase line connecting the second-phase current line and the third-phase current line within the α-phase arrangement plane and bisects the α-phase line.

3. the first phase current line is perpendicular to the α phase arrangement plane at an intersection of the α phase line segment and the α phase arrangement line; 3. The current detection device according to claim 2, wherein the directions of the DC currents flowing through the first, second, and third phase current lines from a power source toward the three-phase motor are the same in the α-phase arrangement plane.

4. 3. The current detection device according to claim 2, wherein the first phase current line is perpendicular to the α-phase arrangement plane at a point other than the α-phase arrangement line.

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

6. 6. The current detection device according to claim 5, wherein a distance along the beta-phase arrangement surface between the beta-phase magnetic detection element and the first phase current line is longer than a distance along the beta-phase arrangement surface between the beta-phase magnetic detection element and the second or third phase current line.

7. 7. The current detection device according to claim 6, wherein the detection axis of the β-phase magnetic detection element is perpendicular to a magnetic flux formed in the β-phase arrangement plane by a current flowing through the first phase current line.

8. A current detection device as described in any one of claims 1 to 7, further comprising a calculation means for multiplying the output value of the β-phase magnetic detection element by a β-phase gain and outputting the result as a β-phase current value, and for multiplying the output value of the α-phase magnetic detection element by an α-phase gain having a value different from the β-phase gain and outputting the result as an α-phase current value.

9. 9. The current detection device according to claim 8, 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.

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