Current detection device

Abstract

To provide a current detection device with high positional displacement toughness while increasing the degree of freedom in the arrangement layout of multiple magnetic detection elements. [Solution] The current detection device 3 detects the current flowing through the busbars 6u, 6v, and 6w of the motor M, and includes a first magnetic detection element 81, a second magnetic detection element 82, and a third magnetic detection element 83 provided around the busbars 6u, 6v, and 6w, a magnetic sensitivity coefficient storage unit 23 that stores a plurality of magnetic sensitivity coefficient values ​​determined according to the relative positions of the magnetic detection elements 81 and 82 with respect to the busbars 6u, 6v, and 6w, and the output values ​​S of the magnetic detection elements 81, 82, and 83. x ,S y ,S z The system includes a two-phase current value calculation unit 22 that calculates a two-phase current value based on the values ​​of multiple magnetic sensitivity coefficients. The position of the detection center of the first magnetic detection element 81 and the orientation of its detection axis are determined by its output value S x This is determined to be proportional to the α-phase current value.

Description

[Technical Field]

[0001] The present invention relates to a current detection device. More specifically, it relates to a current detection device for detecting the current of each phase of a three-phase motor based on at least two magnetic detection elements. [Background technology]

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

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

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

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

[0006] Furthermore, Patent Document 2 by the applicant describes a technique (hereinafter, this technique will also be referred to as "spatial Clark transformation") that attempts to directly obtain two-phase currents (Iα, Iβ) without going through a Clark transformation performed by computer calculations by placing two magnetic detection elements at geometrically determined positions around three phase current lines.

[0007] However, the spatial Clark transformation described in Patent Document 2 limits the arrangement of the three phase current lines and the two magnetic detection elements to only a few patterns. Since electric vehicles require the efficient arrangement of various components, it is preferable to have as much freedom as possible in the arrangement of the magnetic detection elements.

[0008] Furthermore, if the magnetic detection element's installation position deviates from its ideal position, its output value will also deviate. However, Patent Document 2 does not take into account the effects of such positional deviations of the magnetic detection element.

[0009] The present invention aims to provide a current detection device with high positional displacement toughness while increasing the degree of freedom in the arrangement layout of multiple magnetic detection elements, and ultimately contributing to the improvement of energy efficiency. [Means for solving the problem]

[0010] (1) The current detection device according to the present invention (for example, current detection device 3 described later) detects the current flowing through the first phase busbar (for example, the U-phase busbar 6u described later), the second phase busbar (for example, the V-phase busbar 6v described later), and the third phase busbar (for example, the W-phase busbar 6w described later) of a three-phase motor (for example, the motor M described later), and comprises a first magnetic detection element (for example, the first magnetic detection element 81 described later) and a second magnetic detection element (for example, the second magnetic detection element 82 described later) provided around the first phase, second phase, and third phase busbars, a storage means (for example, the magnetic sensitivity coefficient storage unit 23 described later) for storing the values ​​of a plurality of coefficients (for example, the magnetic sensitivity coefficient described later) determined according to the relative positions of the first and second magnetic detection elements with respect to the first phase, second phase, and third phase busbars, and a first output value of the first magnetic detection element (for example, the output value S described later). x ) and the second output value of the second magnetic detection element (for example, the output value S described later) y The system comprises a two-phase current value calculation means (for example, a two-phase current value calculation unit 22 described later) that calculates a two-phase current value based on the values ​​of a plurality of coefficients, wherein when the current values ​​flowing through the first, second, and third phase busbars are I1, I2, and I3, the first output value is S1, and any constant other than "-1 / 2" is X, the position of the detection center of the first magnetic detection element and the orientation of the first detection axis (for example, the first detection axis Ox described later) of the first magnetic detection element on a first element arrangement plane (for example, an element arrangement plane P described later) that is orthogonal to the first, second, and third phase busbars and includes the detection center of the first magnetic detection element are determined such that the following equation (1) holds.

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[0011] (2) In this case, it is preferable that the first phase, second phase, and third phase busbars are arranged on a first virtual line (for example, the first virtual line L1 described later) with the second phase busbar as the center on the first element arrangement plane, and the detection center of the first magnetic detection element is arranged on a second virtual line (for example, the second virtual line L2 described later) which is perpendicular to the first virtual line and passes through the second phase busbar on the first element arrangement plane.

[0012] (3) In this case, the first phase, second phase, and third phase busbars are preferably arranged on a third virtual line (e.g., the first virtual line L1 described later) centered on the second phase busbar on a second element arrangement plane (e.g., the element arrangement plane P described later) that is orthogonal to the first phase, second phase, and third phase busbars and includes the detection center of the second magnetic detection element, and the detection center of the second magnetic detection element is preferably arranged on a fourth virtual line (e.g., the third virtual line L3 or the fourth virtual line L4 described later) that is orthogonal to the third virtual line on the second element arrangement plane and passes through the first phase busbar or the third phase busbar.

[0013] (4) In this case, it is preferable that the first detection axis is arranged parallel to the first virtual line on the first element arrangement plane, and the second detection axis of the second magnetic detection element (for example, the second detection axis Oy described later) is arranged parallel to the third virtual line on the second element arrangement plane.

[0014] (5) In this case, the current detection device further comprises a third magnetic detection element (for example, a third magnetic detection element 83 described later) provided around the first phase, second phase, and third phase busbars, wherein the first phase, second phase, and third phase busbars are arranged on a third virtual line (for example, a first virtual line L1 described later) centered on the second phase busbar on a second element arrangement plane (for example, an element arrangement plane P described later) that is orthogonal to the first phase, second phase, and third phase busbars and includes the detection center of the second magnetic detection element, and the detection center of the second magnetic detection element is on a fourth virtual line (for example, a third virtual line L3 described later) that is orthogonal to the third virtual line on the second element arrangement plane and passes through the first phase busbar Preferably, the first, second, and third phase busbars are arranged on a third element arrangement plane that is orthogonal to the first, second, and third phase busbars and includes the detection center of the third magnetic detection element, with the second phase busbar as the center, on a fifth virtual line (e.g., the first virtual line L1 described later), the detection center of the third magnetic detection element is arranged on a sixth virtual line (e.g., the fourth virtual line L4 described later) that is orthogonal to the fifth virtual line and passes through the third phase busbar on the third element arrangement plane, and the third detection axis of the third magnetic detection element (e.g., the third detection axis Oz described later) is arranged parallel to the fifth virtual line on the third element arrangement plane.

[0015] (6) In this case, the current detection device further comprises a fault determination means (for example, a fault determination unit 25 described later) for determining whether or not the first, second and third magnetic detection elements are faulty, and the two-phase current value calculation means preferably calculates the two-phase current value based on the second output value and the third output value of the third magnetic detection element and the values ​​of a plurality of coefficients when it is determined that the first magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the third magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the second magnetic detection element is faulty, when it is determined that the first output value and the second output value and the values ​​of a plurality of coefficients. [Effects of the Invention]

[0016] (1) In the current detection device according to the present invention, the current flowing through three busbars is detected based on two magnetic detection elements provided around these busbars. Therefore, according to the present invention, the number of magnetic detection elements can be reduced compared to conventional current detection devices that have one magnetic detection element for each busbar, and thus the cost can be reduced. Here, as described in Japanese Patent Application No. 2024-017475 by the present applicant, the current obtained by multiplying the three-phase current (I1, I2, I3) whose three-phase sum is 0 by the transformation matrix (-1 / 2, X, -1 / 2) described in equation (1) above is the same in phase as the current obtained by multiplying the three-phase current (I1, I2, I3) by the first row component (-1 / 2, 1, -1 / 2) of the Clarke transformation matrix, differing only in amplitude. Accordingly, in the present invention, by determining the position of the detection center of the first magnetic detection element and the orientation of the first detection axis such that the above equation (1), which includes any constant other than "-1 / 2", holds true, the output value S1 of the first magnetic detection element can be made proportional to the α-phase current value obtained by combining the currents flowing through the three busbars in a ratio determined by the Clarke transform. Note that when X = -1 / 2, the output value of the first magnetic detection element is always 0 for three-phase currents (I1, I2, I3) whose three-phase sum is 0, so this case is excluded. Furthermore, the present invention includes a storage means for storing the values ​​of a plurality of coefficients determined according to the relative positions of the first and second magnetic detection elements with respect to the three busbars, and a two-phase current value calculation means for calculating a two-phase current value based on the output values ​​of the first and second magnetic detection elements and the values ​​of the plurality of coefficients. Therefore, according to the present invention, while the arrangement layout of the second magnetic detection element among the two magnetic detection elements can be arbitrary, a two-phase current value obtained by converting the three-phase current flowing through the three busbars from three-phase to two-phase can be acquired, thereby increasing the degree of freedom in the arrangement layout of the two magnetic detection elements.

[0017] Furthermore, as will be explained later with reference to Figure 4, under the layout described in Patent Document 2, the β-axis magnetic detection element that outputs a value proportional to the β-phase current value has a larger error with respect to misalignment than the α-axis magnetic detection element that outputs a value proportional to the α-phase current value (i.e., the first magnetic detection element in the present invention). Therefore, in the present invention, by making the arrangement layout of the β-axis magnetic detection element, which has low misalignment toughness, arbitrary, both the degree of freedom in the arrangement layout of the two magnetic detection elements and their misalignment toughness can be increased, thereby contributing to an improvement in energy efficiency.

[0018] (2) In the present invention, the first phase, second phase, and third phase busbars are arranged on a first virtual line centered on the second phase busbar within the first element arrangement plane, and the detection center of the first magnetic detection element is arranged on a second virtual line that is perpendicular to the first virtual line and passes through the second phase busbar. As a result, the three busbars are arranged compactly, and the first magnetic detection element can be used as an α-axis magnetic detection element whose output value is proportional to the α-phase current value.

[0019] (3) In the present invention, the first phase, second phase, and third phase busbars are arranged on a third virtual line centered on the second phase busbar within the second element arrangement plane, and the detection center of the second magnetic detection element is arranged on a fourth virtual line that is perpendicular to the third virtual line and passes through the first phase busbar or the third phase busbar. As a result, in the present invention, the second magnetic detection element can be positioned directly above the first phase or third phase busbar while ensuring the distance along the arrangement direction of the three busbars between the second magnetic detection element and the first magnetic detection element, thereby improving the displacement toughness of the second magnetic detection element.

[0020] (4) In the present invention, the first detection axis is positioned parallel to the first virtual line, and the second detection axis is positioned parallel to the third virtual line. That is, both the first and second detection axes are positioned parallel to the alignment direction of the three busbars. This improves the misalignment toughness of these magnetic detection elements compared to the case where the first and second detection axes are positioned perpendicular to the alignment direction of the three busbars.

[0021] (5) In the present invention, the first, second, and third phase busbars are arranged on a third imaginary line centered on the second phase busbar within the second element arrangement plane, and the detection center of the second magnetic detection element is arranged on a fourth imaginary line perpendicular to the third imaginary line and passing through the first phase busbar. Furthermore, the first, second, and third phase busbars are arranged on a fifth imaginary line centered on the second phase busbar within the third element arrangement plane, and the detection center of the third magnetic detection element is arranged on a sixth imaginary line perpendicular to the fifth imaginary line and passing through the third phase busbar. In this invention, the second and third magnetic detection elements can be positioned directly above the first and third phase busbars, respectively, while ensuring the distance along the arrangement direction of the three busbars between the first, second, and third magnetic detection elements, thereby improving the positional misalignment toughness of the second and third magnetic detection elements.

[0022] (6) In the present invention, if any of the three magnetic detection elements fails, the two-phase current value calculation means calculates the two-phase current value based on the output values ​​of the remaining two magnetic detection elements and the values ​​of a plurality of coefficients stored in the storage means. Therefore, according to the present invention, even if any of the three magnetic detection elements fails, the two-phase current value can be continuously obtained using the remaining two magnetic detection elements. [Brief explanation of the drawing]

[0023] [Figure 1] This figure shows a current detection device according to one embodiment of the present invention and the configuration of an electric vehicle equipped with this current detection device. [Figure 2] This diagram schematically shows the configuration of the sensor unit. [Figure 3] This diagram schematically shows an example of the arrangement of three busbars and three magnetic detection elements on an element arrangement plane perpendicular to the three busbars. [Figure 4] This figure schematically shows the α-axis magnetic detection element and the β-axis magnetic detection element described in Patent Document 2. [Modes for carrying out the invention]

[0024] Hereinafter, a current detection device according to one embodiment of the present invention and an electric vehicle equipped with this current detection device will be described with reference to the drawings.

[0025] Figure 1 shows the configuration of the current detection device 3 and the electric vehicle V equipped with this current detection device according to this embodiment. The following description will focus on the case where the current detection device 3 is mounted on the electric vehicle V, but the present invention is not limited to this. The current detection device 3 can be mounted on anything that controls a three-phase motor based on vector control, such as air conditioners and washing machines, in addition to the electric vehicle V.

[0026] The electric vehicle V comprises a three-phase AC motor M (hereinafter simply referred to as "motor M"), drive wheels W connected to the output shaft of the motor M via a power transmission mechanism (not shown), an inverter 1 connecting a battery (not shown) to the motor M, a sensor unit 7 that generates a signal corresponding to the current flowing through the motor M, a resolver 4 that detects the rotational position of the motor M, and a motor control device 2 that controls the inverter 1 based on the detection signals from the sensor unit 7 and the resolver 4.

[0027] Inverter 1 is a pulse-width modulation (PWM) inverter equipped with a bridge circuit formed by bridging multiple switching elements (e.g., IGBTs), and has the function of converting DC power to AC power. Inverter 1 is connected to a battery on its DC input / output side and to the U-phase, V-phase, and W-phase coils of motor M on its AC input / output side, and converts power between the battery and motor M. Inverter 1 drives the switching elements of each phase on / off according to gate drive signals generated at predetermined timings from a gate drive circuit (not shown), thereby converting DC power supplied from the battery to AC power and supplying it to motor M, and converting AC power supplied from motor M to DC power and supplying it to the battery.

[0028] The sensor unit 7 includes three magnetic detection elements 81, 82, and 83 provided around three busbars (U-phase busbar 6u, V-phase busbar 6v, and W-phase busbar 6w) that connect the motor M and the inverter 1. These magnetic detection elements 81, 82, and 83 each generate a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each busbar 6u, 6v, and 6w along their respective detection axes. In this embodiment, the case in which the three magnetic detection elements 81 to 83 are provided around the three busbars 6u, 6v, and 6w is described, but the present invention is not limited to this. As will be described below, if there are at least two of these three magnetic detection elements 81 to 83, the two-phase current value (I) described later, which is necessary for the vector control of the motor M, can be detected. d ,I q ) can be obtained. When only two magnetic detection elements are provided around the three busbars 6u, 6v, and 6w, it is preferable to combine them so as to include at least a first magnetic detection element 81 in order to maintain the highest possible detection accuracy. That is, it is preferable to combine the first magnetic detection element 81 with the second magnetic detection element 82, or to combine the first magnetic detection element 81 with the third magnetic detection element 83.

[0029] Figure 2 is a schematic diagram showing the configuration of the sensor unit 7. The sensor unit 7 comprises a first magnetic detection element 81, a second magnetic detection element 82, and a third magnetic detection element 83 arranged around three busbars 6u, 6v, and 6w, and a substrate 80 on which these magnetic detection elements 81 to 83 are fixed. In other words, the three magnetic detection elements 81 to 83 are arranged around the three busbars 6u, 6v, and 6w in an integrated state by the substrate 80.

[0030] FIG. 3 schematically shows an example of the arrangement of three bus bars 6u, 6v, 6w and three magnetic detection elements 81 to 83 on an element arrangement plane P orthogonal to the three bus bars 6u, 6v, 6w. Hereinafter, the case where the detection centers of the three magnetic detection elements 81 to 83 are arranged within a common element arrangement plane P as shown in FIG. 3 will be described, but the present invention is not limited thereto. For example, the detection center of the first magnetic detection element 81 may be arranged on a first element arrangement plane orthogonal to the three bus bars 6u, 6v, 6w, the detection center of the second magnetic detection element 82 may be arranged on a second element arrangement plane orthogonal to the three bus bars 6u, 6v, 6w and different from the first element arrangement plane, and the detection center of the third magnetic detection element 83 may be arranged on a third element arrangement plane orthogonal to the three bus bars 6u, 6v, 6w and different from the first and second element arrangement planes. In FIG. 3, within the element arrangement plane P, as the most suitable example, the case where the three bus bars 6u, 6v, 6w are arranged at equal intervals on a straight first virtual line L1 in the order of the U-phase bus bar 6u, the V-phase bus bar 6v, and the W-phase bus bar 6w is shown, but the present invention is not limited thereto. The three bus bars 6u, 6v, 6w do not have to be arranged linearly, and the intervals between these bus bars 6u, 6v, 6w do not have to be equal intervals.

[0031] The output value S of the first magnetic detection element 81 x is such that u , I v , I w ) is proportional to the α-phase current value I α obtained by performing a Clarke transformation on the three-phase current values (I

[0032] ). More specifically, as shown in FIG. 3, the detection center of the first magnetic detection element 81 is arranged on a second virtual line L2 that is orthogonal to the first virtual line L1 on the element arrangement plane P and passes through the central V-phase bus bar 6v. The first detection axis Ox of the first magnetic detection element 81 is arranged to be parallel to the arrangement direction of the three bus bars 6u, 6v, 6w, that is, the first virtual line L1.In contrast, the second magnetic detection element 82 and the third magnetic detection element 83 are basically placed at any position on the element arrangement plane P. In other words, no matter where these two magnetic detection elements 82 and 83 are placed on the element arrangement plane P, the two-phase current value (I) required for the vector control of the motor M can be determined. d ,I q ) can be obtained. However, in order to minimize detection errors and errors due to positional misalignment, it is preferable to place these two magnetic detection elements 82 and 83 in the positions shown in Figure 3.

[0033] More specifically, if a virtual line perpendicular to the first virtual line L1 and passing through the U-phase busbar 6u on the element arrangement plane P is defined as the third virtual line L3, and a virtual line perpendicular to the first virtual line L1 and passing through the W-phase busbar 6w is defined as the fourth virtual line L4, then it is preferable that the detection centers of the second magnetic detection element 82 and the third magnetic detection element 83 be placed on either the third virtual line L3 or the fourth virtual line L4, respectively. In this embodiment, as shown in Figure 3, the case in which the detection center of the second magnetic detection element 82 is placed on the third virtual line L3 and the detection center of the third magnetic detection element 83 is placed on the fourth virtual line L4 is described, but the present invention is not limited to this. For example, the detection center of the second magnetic detection element 82 may be placed on the fourth virtual line L4, and the detection center of the third magnetic detection element 83 may be placed on the third virtual line L3. By arranging the detection centers of the three magnetic detection elements 81-83 in the positions described above, it is possible to position each magnetic detection element 81-83 directly above each of the three busbars 6u, 6v, and 6w while increasing the spacing between them along the alignment direction of the three busbars 6u, 6v, and 6w.

[0034] Furthermore, as shown in Figure 3, it is preferable that the second detection axis Oy of the second magnetic detection element 82 and the third detection axis Oz of the third magnetic detection element 83 be arranged parallel to the first virtual line L1, similar to the first detection axis Ox.

[0035] Here, the output values ​​of the three magnetic detection elements 81-83 (S x ,S y ,S z) is the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the first magnetic detection element 81. xu ,k xv ,k xw ), the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the second magnetic detection element 82. yu ,k yv ,k yw ), and the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the third magnetic detection element 83. zu ,k zv ,k zw Using ), it is expressed by the following equation (2-1): Magnetic sensitivity coefficient (k xu ,k xv ,k xw ) is a value determined by the relative position of the first magnetic detection element 81 with respect to the three busbars 6u, 6v, and 6w, and the orientation of the first detection axis Ox. Magnetic sensitivity coefficient (k yu ,k yv ,k yw ) is a value determined by the relative position of the second magnetic detection element 82 with respect to the three busbars 6u, 6v, and 6w, and the orientation of the second detection axis Oy. Magnetic sensitivity coefficient (k zu ,k zv ,k zw ) are values ​​determined by the relative position of the third magnetic detection element 83 with respect to the three busbars 6u, 6v, and 6w, and the orientation of the third detection axis Oz, respectively. More specifically, for example, the magnetic sensitivity coefficient k of the first magnetic detection element 81 with respect to the W-phase busbar 6w. xw It is defined by the following equation (2-2) according to Ampère's law. In the following equation (2-2), μ is the permeability. Also, in the following equation (2-2), θ xw (x) is the angle between the magnetic field vector of the W-phase busbar 6w and the first detection axis Ox of the first magnetic detection element 81, and x ,z x ) is the coordinate value of the first magnetic detection element 81 on the element arrangement plane P, and (x w ,z w ) is the coordinate value of the W-phase busbar 6w on the element arrangement plane P. Note that other magnetic sensitivity coefficients (k xu ,k xw ,k yuSince the formulas ,…) are also defined based on Ampère's law, similar to equation (2-2) below, a detailed explanation will be omitted.

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[0036] Here, the position of the detection center of the first magnetic detection element 81 and the orientation of the first detection axis Ox on the element arrangement plane P are determined such that the following equation (3) holds. When the three busbars 6u, 6v, and 6w are arranged on the first virtual line L1 as described above, the detection center of the first magnetic detection element 81 is arranged on the second virtual line L2, and the first detection axis Ox is arranged parallel to the first virtual line L1, the following equation (3), which is defined including any constant X other than "-1 / 2", can be made to hold by adjusting the distance between the detection center of the first magnetic detection element 81 and the V-phase busbar 6v. Note that the following equation (3) is defined by the ratio of the three magnetic sensitivity coefficients k xu :k xv :k xw This is equivalent to setting =-1 / 2:X:-1 / 2.

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[0037] Returning to Figure 1, the motor control device 2 is a computer that generates a drive signal for the gate drive circuit of the inverter 1 by performing vector control based on detection signals from the sensor unit 7 and resolver 4, and inputs this signal to the gate drive circuit.

[0038] The motor control device 2 includes, as modules related to the execution of the vector control described above, an AD conversion unit 21, a two-phase current value calculation unit 22, a magnetic sensitivity coefficient storage unit 23, a duty cycle calculation unit 24, and a fault determination unit 25.

[0039] The AD conversion unit 21 performs AD conversion on the detection signals of the three magnetic detection elements 81 to 83, thereby converting the output values ​​(S) of these three magnetic detection elements 81 to 83. x ,S y ,S z ) obtain.

[0040] The fault determination unit 25 determines whether or not there is a fault in the three magnetic detection elements 81, 82, and 83. The fault determination unit 25 determines, for example, the output values ​​(S) of the three magnetic detection elements 81 to 83 obtained by the AD conversion unit 21. x ,S y ,S z Based on this, the presence or absence of a malfunction in these magnetic detection elements 81 to 83 is determined.

[0041] The duty cycle calculation unit 24 calculates the two-phase current value (I) calculated by the two-phase current value calculation unit 22 according to a procedure that will be described later. d ,I q ) and the d-axis current command I corresponding to the driving force requested by the driver. dc and q-axis current command I qc The difference between these current values ​​(I dc -I d ,I qc -I q By performing feedback control based on the above, a drive signal is generated for the gate drive circuit of inverter 1 to realize the driving force requested by the driver, and input to the gate drive circuit.

[0042] The magnetic sensitivity coefficient storage unit 23 stores a plurality of magnetic sensitivity coefficients (k) determined according to the relative positions of the three magnetic detection elements 81 to 83 with respect to the three busbars 6u, 6v, and 6w. xu ,k xv ,k xw ,k yu ,k yv ,k yw ,k zu ,k zv ,k zw Store the value of ).

[0043] The two-phase current value calculation unit 22 calculates the output values ​​(S) of the three magnetic detection elements 81 to 83 obtained by the AD conversion unit 21. x ,S y ,S z Based on at least two of the above, the rotational position θ of the motor M detected by the resolver 4, and the value of the magnetic sensitivity coefficient stored in the magnetic sensitivity coefficient storage unit 23, the two-phase current value (Id ,I q ) is calculated. In the following, the two-phase current value calculation unit 22 calculates the three-phase current value (I u ,I v ,I w This section describes how to calculate the d-axis current value Id and the q-axis current value Iq obtained by applying Clark and Park transforms to the given values.

[0044] First, generally speaking, the three-phase current value (I u ,I v ,I w ) from the two-phase current value (I d ,I q The conversion to ) is expressed by the following equation (4) using the rotational position θ of the motor M. In the following equation (4), "B" is a constant, and its value is the square root of 2 / 3 in the case of absolute conversion and 2 / 3 in the case of relative conversion.

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[0045] Here, as shown in equation (5-1) below, if we define the matrix of magnetic sensitivity coefficients defined by equation (2-1) above as "A", then equation (4) above is its inverse matrix A. -1 Using this, it can be rewritten as follows: Equation (5-2). That is, the output values ​​(S) of the three magnetic detection elements 81 to 83 x ,S y ,S z This is a conversion formula that converts ) to two-phase current values ​​(Id, Iq).

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[0046] The inverse matrix A in equation (5-2) above (3 x 3) -1 The inverse matrix A in equation (5-2) above can be expressed by equation (6-1) below, using the determinant and cofactor matrix of matrix A of the magnetic sensitivity coefficients. Furthermore, the determinant and cofactor matrix of matrix A can be expressed by equations (6-2) and (6-3) below, using the magnetic sensitivity coefficients.Therefore, the inverse matrix A in equation (5-2) above can be expressed by equation (6-1) below. -1The value of each component can be calculated based on the values of the magnetic sensitivity coefficients (k xu , k xv , k xw , k yu , k yv , k yw , k zu , k zv , k zw ) stored in the magnetic sensitivity coefficient storage unit 23.

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[0047] The two-phase current value calculation unit 22 inputs the output values (S x , S y , S z ) of the three magnetic detection elements 81 to 83, the rotational position θ, and the values of a plurality of magnetic sensitivity coefficients read from the magnetic sensitivity coefficient storage unit 23 into the above conversion formula (5-2), thereby calculating the two-phase current values (I d , I q ).

[0048] Note that the above formula (2-1) is a conversion formula for converting the three-phase current values (I u , I v , I w ) into the output values (S x , S y , S z ) of the three magnetic detection elements 81 to 83. However, when the three-phase sum is 0 (I u + I v + I w = 0), the conversion formula (2-1) can be rewritten as the following formulas (7-1) to (7-3). That is, the following formula (7-1) is a conversion formula for converting the three-phase current values (I u , I v , I w ) into the output values (S x , S y ) of the two magnetic detection elements 81 and 82, and the following formula (7-2) is a conversion formula for converting the three-phase current values (I u , I v , I w ) into the output values (S x , S zThis is a conversion formula to convert to ), and the following formula (7-3) is a three-phase current value (I u ,I v ,I w ) is the output value (S) of the two magnetic detection elements 82, 83 y ,S z This is a conversion formula that converts to ).

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[0049] Therefore, according to the above equation (7-1), in the above conversion equation (5-2), the three magnetic sensitivity coefficients (k) relating to the third magnetic detection element 83 zu ,k zv ,k zw By setting all the values ​​of ) to "1" (that is, k zu =k zv =k zw =1), output values ​​of the first and second magnetic detection elements 81, 82 (S x ,S y ) from the two-phase current value (I d ,I q A conversion formula can be obtained to convert to ). Furthermore, according to the above formula (7-2), in the above conversion formula (5-2), the three magnetic sensitivity coefficients (k) relating to the second magnetic detection element 82 can be obtained. yu ,k yv ,k yw By setting all the values ​​of ) to "1" (that is, k yu =k yv =k yw =1), output values ​​of the first and third magnetic detection elements 81, 83 (S x ,S z ) from the two-phase current value (I d ,I q A conversion formula can be obtained to convert to ). Furthermore, according to the above formula (7-3), in the above conversion formula (5-2), the three magnetic sensitivity coefficients (k) relating to the first magnetic detection element 81 can be obtained. xu ,k xv ,k xw By setting all the values ​​of ) to "1" (that is, k xu =k xv =k xw =1), output values ​​of the second and third magnetic detection elements 82, 83 (S y,S z ) from the two-phase current value (I d ,I q A conversion formula can be obtained to convert to ).

[0050] As described above, the two-phase current value calculation unit 22 calculates the output values ​​(S) of the three magnetic detection elements 81 to 83. x ,S y ,S z The two-phase current value (I d ,I q The two-phase current value calculation unit 22 then selects at least two of the three magnetic detection elements 81 to 83 that have been determined to be normal by the fault determination unit 25, and calculates the two-phase current value (I) based on the output values ​​of the selected at least two magnetic detection elements. d ,I q Calculate ).

[0051] More specifically, if all three magnetic detection elements 81-83 are determined to be normal, the two-phase current value calculation unit 22 calculates all the output values ​​(S) of the three magnetic detection elements 81-83. x ,S y ,S z ), output values ​​(S) of the first and second magnetic detection elements 81, 82 x ,S y ), or the output value (S) of the first and third magnetic detection elements 81, 83. x ,S z Based on this, the two-phase current value (I d ,I q The two-phase current value calculation unit 22 calculates the two-phase current value (I) by combination so as to include at least the output value of the first magnetic detection element 81, in order to maintain the detection accuracy as high as possible. d ,I q It is preferable to calculate ).

[0052] If it is determined that the first magnetic detection element 81 is faulty and the second and third magnetic detection elements 82 and 83 are functioning normally, the two-phase current value calculation unit 22 calculates the output values ​​(S) of the second and third magnetic detection elements 82 and 83. y ,S zBased on this, the two-phase current value (I d ,I q Calculate ).

[0053] If it is determined that the second magnetic detection element 82 is faulty and the first and third magnetic detection elements 81 and 83 are functioning normally, the two-phase current value calculation unit 22 calculates the output values ​​(S) of the first and third magnetic detection elements 81 and 83. x ,S z Based on this, the two-phase current value (I d ,I q Calculate ).

[0054] Furthermore, if it is determined that the third magnetic detection element 83 is faulty and the first and second magnetic detection elements 81 and 82 are functioning normally, the two-phase current value calculation unit 22 calculates the output values ​​(S) of the first and second magnetic detection elements 81 and 82. x ,S y Based on this, the two-phase current value (I d ,I q Calculate ).

[0055] The current detection device 3 according to this embodiment provides the following effects. (1) In the current detection device according to the present invention, the current flowing through the three busbars 6u, 6v, and 6w is detected based on at least two magnetic detection elements 81 and 82 provided around these busbars 6u, 6v, and 6w. Therefore, according to this embodiment, the number of magnetic detection elements can be reduced compared to a conventional current detection device that has one magnetic detection element for each busbar, and thus the cost can be reduced. Here, as described in Japanese Patent Application No. 2024-017475 by the present applicant, the current obtained by multiplying the three-phase current (I1, I2, I3) whose three-phase sum is 0 by the transformation matrix (-1 / 2, X, -1 / 2) described in equation (1) above is the same in phase as the current obtained by multiplying the three-phase current (I1, I2, I3) by the first row component (-1 / 2, 1, -1 / 2) of the Clarke transformation matrix, differing only in amplitude. Therefore, in this embodiment, the position of the detection center of the first magnetic detection element 81 and the orientation of the first detection axis Ox are determined such that the above equation (3) holds true, thereby determining the output value S of the first magnetic detection element 81. xThe α-phase current value I is obtained by combining the currents flowing through the three busbars 6u, 6v, and 6w in a ratio determined by the Clark transform. α It can be made proportional to this. Furthermore, this embodiment includes a magnetic sensitivity coefficient storage unit 23 that stores a plurality of magnetic sensitivity coefficient values ​​determined according to the relative positions of the first and second magnetic detection elements 81 and 82 with respect to the three busbars 6u, 6v, and 6w, and the output value S of the first and second magnetic detection elements 81 and 82. x ,S y Based on the above multiple magnetic sensitivity coefficient values, the two-phase current value (I d ,I q The system includes a two-phase current value calculation unit 22 that calculates the two-phase current value (I) obtained by converting the three-phase current flowing through the three busbars 6u, 6v, and 6w from three-phase to two-phase, while allowing the arrangement layout of the second magnetic detection element 82 among the two magnetic detection elements 81 and 82 to be arbitrary. d ,I q Since it is possible to obtain ), the degree of freedom in the arrangement layout of the two magnetic detection elements 81 and 82 can be increased.

[0056] Figure 4 is a schematic diagram showing the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β described in Patent Document 2. In the invention described in Patent Document 2, the output values ​​of these two magnetic detection elements 8α and 8β are combined in a ratio determined by the Clarke transform of the currents flowing through the three busbars 6u, 6v, and 6w to obtain the α-phase current value I α and β-phase current value I β The elements are arranged in proportion to the α-axis magnetic detection element 8α. The α-axis magnetic detection element 8α is positioned in the same location as the first magnetic detection element 81 in this embodiment. Also, as shown in Figure 4, when the three busbars 6u, 6v, and 6w are arranged side by side, the β-axis magnetic detection element 8β needs to be positioned directly above the V-phase busbar 6v. The output value of the β-axis magnetic detection element 8β is the β-phase current value I β To make it proportional, the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β with respect to the V-phase busbar 6v must be set to 0. For this reason, the detection axis Oβ of the β-axis magnetic detection element 8β must be arranged orthogonal to the arrangement direction of the three busbars 6u, 6v, and 6w, as shown in Figure 4.

[0057] However, the detection axis Oβ of such a β-axis magnetic detection element 8β is orthogonal only directly above the V-phase busbar 6v to the magnetic flux formed concentrically around the V-phase busbar 6v (see dashed line in Figure 4). Therefore, if the detection center of the β-axis magnetic detection element 8β is shifted along the alignment direction of the three busbars 6u, 6v, and 6w, the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β with respect to the V-phase busbar 6v becomes non-zero. Furthermore, since the magnetic flux formed concentrically around the U-phase busbar 6u (see dashed line in Figure 4) is approximately parallel to the detection axis Oβ, the change in the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β with respect to the V-phase busbar 6v due to a positional shift is greater than the change in the magnetic sensitivity coefficient of the α-axis magnetic detection element 8α with respect to the V-phase busbar 6v due to a positional shift. Therefore, the β-axis magnetic detection element 8β, which outputs a value proportional to the β-phase current value, has a larger error in terms of misalignment than the α-axis magnetic detection element 8α (i.e., the first magnetic detection element 81 in this embodiment), which outputs a value proportional to the α-phase current value. In contrast, in this embodiment, by not employing the β-axis magnetic detection element 8β, which has low misalignment toughness, and by allowing the placement layout of the second magnetic detection element 82 to be arbitrary, both the degree of freedom in the placement layout of the two magnetic detection elements 81 and 82 and their misalignment toughness can be increased, thereby contributing to an improvement in energy efficiency.

[0058] (2) In this embodiment, the three busbars 6u, 6v, and 6w are arranged on a first virtual line L1 with the V-phase busbar 6v as the center within the element arrangement plane P, and the detection center of the first magnetic detection element 81 is arranged on a second virtual line L2 that is orthogonal to the first virtual line L1 and passes through the V-phase busbar 6v. This allows the three busbars 6u, 6v, and 6w to be arranged compactly, while the first magnetic detection element 81 can be used as an α-axis magnetic detection element whose output value is proportional to the α-phase current value.

[0059] (3) In this embodiment, the detection center of the second magnetic detection element 82 is positioned on a third virtual line L3 or a fourth virtual line L4 that is orthogonal to the first virtual line L1 and passes through the U-phase busbar 6u or the W-phase busbar 6w. In this embodiment, the second magnetic detection element 82 can be positioned directly above the U-phase busbar 6u or the W-phase busbar 6w while ensuring the distance along the alignment direction of the three busbars 6u, 6v, and 6w between the second magnetic detection element 82 and the first magnetic detection element 81, thereby improving the displacement toughness of the second magnetic detection element 82.

[0060] (4) In this embodiment, the first detection axis Ox is arranged parallel to the first virtual line L1, and the second detection axis Oy is arranged parallel to the first virtual line L1. That is, both the first and second detection axes Ox and Oy are arranged parallel to the arrangement direction of the three busbars 6u, 6v, and 6w. This improves the misalignment toughness of these magnetic detection elements 81 and 82 compared to the case in which the first and second detection axes Ox and Oy are arranged orthogonal to the arrangement direction of the three busbars 6u, 6v, and 6w.

[0061] (5) In this embodiment, the detection center of the second magnetic detection element 82 is positioned on a third virtual line L3 that is orthogonal to the first virtual line L1 and passes through the U-phase busbar 6u. The detection center of the third magnetic detection element 83 is positioned on a fourth virtual line L4 that is orthogonal to the first virtual line L1 and passes through the W-phase busbar 6w. In this embodiment, the distance along the alignment direction of the three busbars 6u, 6v, and 6w between the first, second, and third magnetic detection elements 81, 82, and 83 can be secured, and the second magnetic detection element 82 and the third magnetic detection element 83 can be positioned directly above the U-phase busbar 6u and the W-phase busbar 6w, respectively, thereby improving the positional displacement toughness of the second and third magnetic detection elements 82 and 83.

[0062] (6) In this embodiment, if any of the three magnetic detection elements 81, 82, and 83 fail, the two-phase current value calculation unit 22 calculates the two-phase current value based on the output values ​​of the remaining two magnetic detection elements and the values ​​of a plurality of magnetic sensitivity coefficients stored in the magnetic sensitivity coefficient storage unit 23. Therefore, according to this embodiment, even if any of the three magnetic detection elements 81, 82, and 83 fail, the two-phase current value can be continuously obtained using the remaining two magnetic detection elements.

[0063] Although one embodiment of the present invention has been described above, the present invention is not limited thereto. Within the scope of the spirit of the present invention, the details of the configuration may be modified as appropriate. [Explanation of Symbols]

[0064] V...vehicle W…Drive wheels M...Motor (three-phase motor) 6u…U-phase busbar (first-phase busbar) 6V...V-phase busbar (second phase busbar) 6w...W-phase busbar (third-phase busbar) 1…Inverter 2…Motor control device 21…AD conversion unit 22...Two-phase current value calculation unit (two-phase current value calculation means) 23... Magnetic sensitivity coefficient storage unit (storage means) 24... Duty Calculation Unit 25...Failure judgment section (failure judgment means) 3…Current detection device 7…Sensor unit 81…First magnetic detection element Ox...First detection axis 82...Second magnetic detection element Oy...Second detection axis 83...Third magnetic detection element Oz...Third detection axis P...this arrangement surface 4…Resolver

Claims

1. A current detection device for detecting the current flowing through the first phase busbar, second phase busbar, and third phase busbar of a three-phase motor, A first magnetic detection element and a second magnetic detection element are provided around the first phase, second phase, and third phase busbars, A storage means for storing the values ​​of a plurality of coefficients determined according to the relative positions of the first and second magnetic detection elements with respect to the first, second, and third phase busbars, The system includes a two-phase current value calculation means that calculates a two-phase current value based on the first output value of the first magnetic detection element, the second output value of the second magnetic detection element, and the values ​​of a plurality of coefficients, A current detection device characterized in that, when the current values ​​flowing through the first, second, and third phase busbars are I1, I2, and I3, the first output value is S1, and X is an arbitrary constant other than "-1 / 2", the position of the detection center of the first magnetic detection element and the orientation of the first detection axis of the first magnetic detection element on a first element arrangement plane that is orthogonal to the first, second, and third phase busbars and includes the detection center of the first magnetic detection element are determined such that the following equation (1) holds true. [Math 1]

2. The first phase, second phase, and third phase busbars are arranged on a first imaginary line centered on the second phase busbar in the first element arrangement plane. The current detection device according to claim 2, characterized in that the detection center of the first magnetic detection element is positioned on a second virtual line that is perpendicular to the first virtual line and passes through the second phase busbar on the first element arrangement surface.

3. The first, second, and third phase busbars are arranged on a third imaginary line centered on the second phase busbar in a second element arrangement plane that is orthogonal to the first, second, and third phase busbars and includes the detection center of the second magnetic detection element. The current detection device according to claim 3, characterized in that the detection center of the second magnetic detection element is positioned on a fourth virtual line that is perpendicular to the third virtual line on the second element arrangement surface and passes through the first phase busbar or the third phase busbar.

4. The first detection axis is positioned parallel to the first virtual line on the first element arrangement plane. The current detection device according to claim 3, characterized in that the second detection axis of the second magnetic detection element is arranged parallel to the third virtual line on the second element arrangement surface.

5. The system further comprises a third magnetic detection element provided around the first, second, and third phase busbars, The first, second, and third phase busbars are arranged on a third imaginary line centered on the second phase busbar in a second element arrangement plane that is orthogonal to the first, second, and third phase busbars and includes the detection center of the second magnetic detection element. The detection center of the second magnetic detection element is positioned on a fourth virtual line that is perpendicular to the third virtual line and passes through the first phase busbar on the second element arrangement surface. The first, second, and third phase busbars are arranged on a fifth imaginary line centered on the second phase busbar in a third element arrangement plane that is orthogonal to the first, second, and third phase busbars and includes the detection center of the third magnetic detection element. The detection center of the third magnetic detection element is positioned on a sixth virtual line that is perpendicular to the fifth virtual line and passes through the third phase busbar on the third element arrangement surface. The current detection device according to claim 1 or 2, characterized in that the third detection axis of the third magnetic detection element is arranged parallel to the fifth virtual line on the third element arrangement surface.

6. The system further includes a fault determination means for determining whether or not the first, second, and third magnetic detection elements are faulty, The two-phase current value calculation means is If it is determined that the first magnetic detection element has failed, the two-phase current value is calculated based on the second output value, the third output value of the third magnetic detection element, and the values ​​of the multiple coefficients. If it is determined that the second magnetic detection element has failed, the two-phase current value is calculated based on the first output value, the third output value and the values ​​of the plurality of coefficients. The current detection device according to claim 5, characterized in that, when it is determined that the third magnetic detection element has failed, the two-phase current value is calculated based on the first output value, the second output value and the values ​​of a plurality of coefficients.

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