Current detection device

Abstract

Provided is a current detection device capable of redundantizing a magnetic detection element without increasing cost or size. 【Solution means】The current value acquisition unit 22 acquires the α-phase current value I α and the β-phase current value I β based on the output values of the magnetic detection elements 8α, 8β, 8γ provided around the phase current lines 6u, 6v, 6w. The relative position of the γ-axis magnetic detection element 8γ with respect to the phase current lines 6u, 6v, 6w and the direction of the detection axis are determined so that a predetermined conditional expression is satisfied. When the α-axis magnetic detection element 8α is normal, the current value acquisition unit 22 uses its output value S α as the α-phase current value I α to acquire, and when the β-axis magnetic detection element 8β is normal, uses its output value S β as the β-phase current value I β to acquire. When the β-axis magnetic detection element 8β fails, the difference value of the output values of the two magnetic detection elements 8α, 8γ is used as the β-phase current value I β to acquire, and when the α-axis magnetic detection element 8α fails, the difference value of the output values of the two magnetic detection elements 8β, 8γ is used as the α-phase current value I α to acquire.

Description

[Technical Field]

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

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

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

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

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

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

[0007] Incidentally, in some cases, on-board sensors installed in vehicles are required to be redundant in case of failure. For example, in a current detection device as shown in Patent Document 2, two-phase current (Iα, Iβ) is detected using an α-axis magnetic detection element and a β-axis magnetic detection element. Therefore, if the magnetic detection elements for each phase in such a current detection device are simply made redundant, two magnetic detection elements would be required for each phase, i.e., a total of four magnetic detection elements, which may increase the cost and size of the current detection device.

[0008] The present invention aims to provide a current detection device that can make magnetic detection elements redundant without increasing cost or size, and thereby contribute to improving energy efficiency. [Means for solving the problem]

[0009] (1) The current detection device according to the present invention detects the currents flowing through the first-phase current line (for example, the U-phase current line 6u described later), the second-phase current line (for example, the V-phase current line 6v described later), and the third-phase current line (for example, the W-phase current line 6w described later) of a three-phase motor (for example, the motor M described later) using an α-axis magnetic detection element (for example, the α-axis magnetic detection element 8α described later), a β-axis magnetic detection element (for example, the β-axis magnetic detection element 8β described later), and a γ-axis magnetic detection element (for example, the γ-axis magnetic detection element 8γ described later) provided around the first, second, and third-phase current lines, and includes a current value acquisition unit that acquires α-phase current values and β-phase current values based on the output values of the α-axis, β-axis, and γ-axis magnetic detection elements. Let the current values flowing through the first-phase, second-phase, and third-phase current lines be I1, I2, and I3, and let the output values of the α-axis, β-axis, and γ-axis magnetic detection elements be S γ , α , β , γ , β , β , S β , S γ Let the gain values of the α-axis, β-axis, and γ-axis magnetic detection elements be G α , G β , G γ Let the magnetic sensitivity coefficients of the α-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines be k α1 , k α2 , k α3 Let the magnetic sensitivity coefficients of the β-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines be k β1 , k β2 , k β3 In this case, the relative position of the γ-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines and the direction of the detection axis (for example, the γ-axis Oγ described later) are determined such that the following equation (1) holds. The current value acquisition unit acquires the output value S α of the α-axis magnetic detection element during normal operation as the α-phase current value I α , acquires the output value S β of the β-axis magnetic detection element during normal operation as the β-phase current value I β , and when the β-axis magnetic detection element fails, acquires the difference value S γ / G γ -S α as the β-phase current value I β , and when the α-axis magnetic detection element fails, acquires the difference value Sγ / G γ -S β The α-phase current value I α It is characterized by being acquired as such.

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[0010] (2) In this case, the detection center positions of the α-axis, β-axis, and γ-axis magnetic detection elements coincide, the α-axis which is the detection axis of the α-axis magnetic detection element (for example, α-axis Oα as described later), the β-axis which is the detection axis of the β-axis magnetic detection element (for example, β-axis Oβ as described later), and the γ-axis which is the detection axis of the γ-axis magnetic detection element (for example, γ-axis Oγ as described later) are arranged in the same plane, the α-axis is perpendicular to the β-axis in the plane, and the angle θ between the γ-axis and the α-axis in the plane is preferably determined such that the following equation (2) holds.

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[0011] (3) In this case, the relative positions of the α-axis, β-axis, and γ-axis magnetic detection elements with respect to the first phase, second phase, and third phase current lines and the orientation of the detection axes are preferably determined such that the following equation (3) holds true.

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[0012] (1) In the current detection device according to the present invention, the current flowing through three current lines is detected based on three magnetic detection elements provided around these current lines. More specifically, the current value acquisition unit, when the α-axis and β-axis magnetic detection elements are functioning normally, acquires their output values ​​S α ,S β α-phase and β-phase current values ​​I α ,I βThe current value acquisition unit obtains the difference value S obtained using the output values ​​of the α-axis and γ-axis magnetic detection elements in the event of a failure of the β-axis magnetic detection element. γ / G γ -S α β-phase current value I β The difference value S is obtained using the output values ​​of the β-axis and γ-axis magnetic detection elements in the event of a failure of the α-axis magnetic detection element. γ / G γ -S β α-phase current value I α This can be obtained as follows. Thus, according to the present invention, by arranging the γ-axis magnetic detection element so that the above formula (1) holds true, even if either the α-axis magnetic detection element or the β-axis magnetic detection element fails, the γ-axis magnetic detection element can be used to obtain the α-phase and β-phase current values ​​I α ,I β This allows for continuous acquisition of this information. Therefore, according to the present invention, compared to the case where magnetic detection elements are made redundant for each phase, the magnetic detection elements can be made redundant without increasing cost or size, and this can contribute to improving energy efficiency.

[0013] (2) In the present invention, the size of the current detection device can be made compact by aligning the detection center positions of the three magnetic detection elements. In the present invention, the detection axes of the three magnetic detection elements are arranged in the same plane, the α axis and β axis are orthogonal, and the angle θ between the γ axis and α axis is determined so that equation (2) above holds true. This makes it possible to arrange the three magnetic detection elements so that equation (1) above holds true while aligning the detection center positions of the three magnetic detection elements.

[0014] (3) In the present invention, the relative positions of the α-axis, β-axis, and γ-axis magnetic detection elements with respect to the first, second, and third phase current lines, and the orientation of the detection axes, are determined such that equation (3) above, which is a matrix operation formula equivalent to the Clarke transformation, holds true. Therefore, according to the present invention, even if either the α-axis or β-axis magnetic detection element fails, the output values ​​of the remaining normal magnetic detection element and the γ-axis magnetic detection element are read by the current value acquisition unit, thereby directly obtaining the α-phase and β-phase current values ​​I without going through the Clarke transformation calculated by a computer. α ,I β You can continue to acquire it. [Brief explanation of the drawing]

[0015] [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 figure shows an example of the arrangement layout of three phase current lines and three magnetic detection elements. [Figure 3] This is a perspective view showing the configuration of the sensor unit. [Figure 4] This is a side view showing the configuration of the sensor unit. [Modes for carrying out the invention]

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The sensor unit 7 includes three magnetic detection elements (α-axis magnetic detection element 8α, β-axis magnetic detection element 8β, and γ-axis magnetic detection element 8γ) arranged around the three phase current lines (U-phase current line 6u, V-phase current line 6v, and W-phase current line 6w) that connect the motor M and the inverter 1. These magnetic detection elements 8α, 8β, and 8γ each generate a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each phase current line 6u, 6v, and 6w, along their respective detection axes. Specific examples of the arrangement layout of these magnetic detection elements 8α, 8β, and 8γ, as well as the three phase current lines 6u, 6v, and 6w, will be explained later with reference to Figures 2 to 4.

[0021] The motor control device 2 is a computer that generates a drive signal for the gate drive circuit of the inverter 1 and inputs it to the gate drive circuit by performing vector control based on detection signals from three magnetic detection elements 8α, 8β, and 8γ and the resolver 4.

[0022] The motor control device 2 includes, as modules related to the execution of the vector control described above, an AD conversion unit 21, a current value acquisition unit 22, a dq conversion unit 23, a duty cycle calculation unit 24, and a fault determination unit 25.

[0023] The AD conversion unit 21 performs AD conversion on the detection signals of the three magnetic detection elements 8α, 8β, and 8γ to obtain the output values ​​(Sα, Sβ, Sγ) of these three magnetic detection elements 8α, 8β, and 8γ.

[0024] The fault determination unit 25 determines whether or not the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β are faulty. The fault determination unit 25 determines, for example, the output values ​​(S) of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β obtained by the AD conversion unit 21. α ,S β Based on this, the presence or absence of malfunctions in these magnetic detection elements 8α and 8β is determined.

[0025] The current value acquisition unit 22 acquires the output values ​​(S) of the three magnetic detection elements 8α, 8β, and 8γ acquired by the AD conversion unit 21. α ,S β ,S γ ) and based on the fault determination result by the fault determination unit 25, the output values ​​(S) of the three magnetic detection elements 8α, 8β, 8γ α ,S β ,S γ Based on this, the α-phase current value I, which corresponds to the two-phase current obtained by performing a Clarke transform on the three-phase current (Iu, Iv, Iw), is... α and β-phase current value I β Obtain it.

[0026] More specifically, when the α-axis magnetic detection element 8α is functioning normally, the current value acquisition unit 22 acquires the output value S of the α-axis magnetic detection element 8α as shown in equation (4-1) below.α α-phase current value I α The current value acquisition unit 22 acquires the output value S of the β-axis magnetic detection element 8β when the β-axis magnetic detection element 8β is functioning normally, as shown in equation (4-2) below. β β-phase current value I β The current value acquisition unit 22 acquires the output value S of the α-axis magnetic detection element 8α when the fault determination unit 25 determines that the α-axis magnetic detection element 8α is functioning correctly. α current value I α The output value S of the β-axis magnetic detection element 8β is obtained, and if the fault determination unit 25 determines that the β-axis magnetic detection element 8β is normal, then the output value S of the β-axis magnetic detection element 8β is obtained. β current value I β It will be acquired as follows.

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[0027] Furthermore, in the event of a failure of the β-axis magnetic detection element 8β, the current value acquisition unit 22 will acquire the output value S of the γ-axis magnetic detection element 8γ, as shown in equation (5) below. γ The gain value G described later γ The value obtained by dividing by and the output value S of the α-axis magnetic detection element 8α α The difference value S γ / G γ -S α β-phase current value I β This is how the current value acquisition unit 22 obtains the β-phase current value I by using the output values ​​of the α-axis magnetic detection element 8α and the γ-axis magnetic detection element 8γ, even if the β-axis magnetic detection element 8β is faulty. β You can obtain it.

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[0028] Furthermore, in the event of a failure of the α-axis magnetic detection element 8α, the current value acquisition unit 22 will acquire the output value S of the γ-axis magnetic detection element 8γ, as shown in equation (6) below. γ The gain value G described later γ The value obtained by dividing by and the output value S of the β-axis magnetic detection element 8β βThe difference value S γ / G γ -S β α-phase current value I α This is how the current value acquisition unit 22 obtains the α-phase current value I by using the output values ​​of the β-axis magnetic detection element 8β and the γ-axis magnetic detection element 8γ, even if the α-axis magnetic detection element 8α is faulty. α You can obtain it.

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[0029] Therefore, in this embodiment, the current detection device 3 for detecting the current flowing through the three-phase current lines 6u, 6v, and 6w of the motor M is composed of three magnetic detection elements 8α, 8β, and 8γ, an AD conversion unit 21, and a current value acquisition unit 22.

[0030] The dq conversion unit 23 converts the current value (I) obtained by the current value acquisition unit 22. α ,I β The d-axis current Id and q-axis current Iq are calculated by performing known calculations using the detection signals of resolver 4.

[0031] The duty cycle calculation unit 24 acquires the d-axis current command Idc and q-axis current command Iqc according to the driving force requested by the driver, and generates a drive signal for the gate drive circuit of the inverter 1 to realize the driving force requested by the driver by performing feedback control based on the deviation of these current values ​​(Idc-Id, Iqc-Iq), and inputs it to the gate drive circuit.

[0032] Next, we will explain the conditions imposed on the arrangement layout of the three phase current lines 6u, 6v, and 6w and the three magnetic detection elements 8α, 8β, and 8γ in order to satisfy the above equations (4-1), (4-2), (5), and (6).

[0033] FIG. 2 is a diagram showing an example of the layout of three-phase current lines 6u, 6v, 6w and three magnetic detection elements 8α, 8β, 8γ. In the following, for the sake of easy understanding, as shown in FIG. 2, the case where the three-phase current lines 6u, 6v, 6w are arranged linearly and at equal intervals in the X-Y plane orthogonal to these three-phase current lines 6u, 6v, 6w is shown, but the present invention is not limited to this. Also, in the following, for the sake of easy understanding, as shown in FIG. 2, the case where the detection centers of the three magnetic detection elements 8α, 8β, 8γ are all arranged in the above X-Y plane is shown, but the present invention is not limited to this. Also, in the following, for the sake of easy understanding, as shown in FIG. 2, the case where the detection axes of the three magnetic detection elements 8α, 8β, 8γ are all arranged in the above X-Y plane is shown, but the present invention is not limited to this.

[0034] The following formula (7) is a conditional formula imposed on the layout of the three-phase current lines 6u, 6v, 6w and the three magnetic detection elements 8α, 8β, 8γ in order to satisfy the above formulas (5) and (6). In the following formula (7), (Iu, Iv, Iw) respectively represent the current values flowing through the u-phase current line 6u, the v-phase current line 6v, and the w-phase current line 6w. Also (G α ,G β ,G γ 0) respectively represent the gain values unique to the α-axis magnetic detection element 8α, the β-axis magnetic detection element 8β, and the γ-axis magnetic detection element 8γ. These gain values (G α ,G β ,G γ ) are the ratios of the output values (S α ,S β ,S γ ) of the respective magnetic detection elements 8α, 8β, 8γ to the components along the detection axes of the magnetic flux densities at the detection centers of the respective magnetic detection elements 8α, 8β, 8γ, and are determined by the materials and structures of the respective magnetic detection elements 8α, 8β, 8γ. More specifically, these gain values (G α ,G β ,G γ ) are determined by the materials and structures of coils 61, 71, 81 and support members 62, 72, etc. as shown in FIG. 3 to be described later in the case of the magnetic detection elements 8α, 8β, 8γ. Also, in the following formula (7), (k αu ,k αv ,kαw ) indicates the magnetic sensitivity coefficients for the three-phase current lines 6u, 6v, and 6w of the α-axis magnetic detection element 8α respectively, (k βu , k βv , k βw ) indicates the magnetic sensitivity coefficients for the three-phase current lines 6u, 6v, and 6w of the β-axis magnetic detection element 8β respectively.

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[0035] Here, these magnetic sensitivity coefficients (k αu , k αv , k αw ) and (k βu , k βv , k βw ) are values determined by the relative positions of the three-phase current lines 6u, 6v, and 6w of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β respectively and the directions of the detection axes. More specifically, for example, the magnetic sensitivity coefficient k αv for the V-phase current line 6v of the α-axis magnetic detection element 8α is defined by the following formula (8) according to Ampere's law. In the following formula (8), μ is the magnetic permeability. Also, in the following formula (8), θ vα is the angle formed by the magnetic field vector of the V-phase current line 6v and the detection axis of the α-axis magnetic detection element 8α, and (x α , y α ) are the coordinate values of the α-axis magnetic detection element 8α in the X-Y plane, and (x v , y v ) are the coordinate values of the V-phase current line 6v in the X-Y plane. Note that the other magnetic sensitivity coefficients (k αu , k αw ) and (k βu , k βv , k βw ) are also defined based on Ampere's law in the same way as the following formula (8), so detailed explanations are omitted. As described above, the magnetic sensitivity coefficients (k αu , k αv , k αw ) and (k βu , k βv , k βwThe relative positions of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β with respect to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axis, respectively, are determined.

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[0036] Also, in the above formula (7), (G α k αu +G β k βu ,G α k αv +G β k βv ,G α k αw +G β k βv ) corresponds to the magnetic sensitivity coefficients for the three phase current lines 6u, 6v, and 6w of the γ-axis magnetic detection element 8γ, respectively. That is, the relative position of the γ-axis magnetic detection element 8γ with respect to the three phase current lines 6u, 6v, and 6w and the orientation of the detection axis are determined by the gain values ​​(G) of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β. α ,G β ) and magnetic sensitivity coefficient (k αu ,k αv ,k αw ) and (k βu ,k βv ,k βw By setting the above formula (7), which is defined based on ), to hold, the above formulas (5) and (6) can be made to hold.

[0037] Furthermore, equation (9) below is a conditional expression imposed on the arrangement layout of the three phase current lines 6u, 6v, 6w and the three magnetic detection elements 8α, 8β, 8γ in order to satisfy equations (4-1), (4-2), (5), and (6) above. That is, as shown in equations (4-1) and (4-2) above, the output values ​​(S) of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β α ,S β ) and two-phase current (I α ,I βTo make it equal to ), the relative positions of the three magnetic detection elements 8α, 8β, and 8γ with respect to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axes are determined such that the following equation (9), derived from the Clark transformation equation, holds true.

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[0038] Next, specific examples of sensor units 7 that satisfy equations (7) and (9) above will be explained with reference to Figures 3 and 4.

[0039] Figure 3 is a perspective view showing the configuration of the sensor unit 7 according to this embodiment. Figure 4 is a side view showing the configuration of the sensor unit 7. In the following description, the case in which the α-axis magnetic detection element 8α, the β-axis magnetic detection element 8β, and the γ-axis magnetic detection element 8γ are each constructed by coils wound in a ring shape (i.e., the so-called coil type), is described, but the present invention is not limited to this. All or any of these magnetic detection elements 8α, 8β, and 8γ may be constructed by, for example, Hall elements.

[0040] The sensor unit 7 is composed of an α-axis magnetic detection element 8α that outputs a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through a current line (not shown) along the detection axis Oα (hereinafter, the detection axis of the α-axis magnetic detection element 8α is also referred to as the α axis), a β-axis magnetic detection element 8β that outputs a detection signal corresponding to the component along the detection axis Oβ (hereinafter, the detection axis of the β-axis magnetic detection element 8β is also referred to as the β axis), and a γ-axis magnetic detection element 8γ that outputs a detection signal corresponding to the component along the detection axis Oγ (hereinafter, the detection axis of the γ-axis magnetic detection element 8γ is also referred to as the γ axis). As shown in Figures 3 and 4, the three magnetic detection elements 8α, 8β, and 8γ are combined such that their respective detection center positions coincide and the α axis Oα, β axis Oβ, and γ axis Oγ are arranged in the same arrangement plane.

[0041] The α-axis magnetic detection element 8α comprises an α-axis coil 61, which is constructed by winding a conductive wire in an annular shape (for example, clockwise) along the α-axis Oα extending downward in the vertical direction in Figure 3, and an α-axis support member 62, which is provided inside the α-axis coil 61 and supports at least a portion of the inner circumference of the α-axis coil 61. In the α-axis magnetic detection element 8α constructed by combining the α-axis coil 61 and the α-axis support member 62 in this way, the center of the α-axis coil 61 becomes the center of the α-axis magnetic detection element 8α.

[0042] The α-axis support member 62 is disc-shaped, extending along a plane perpendicular to the α-axis Oα, and supports the inner circumference of the α-axis coil 61 over its entire circumference. A central through-hole 63 extending along the α-axis Oα is formed in the center of the α-axis support member 62. In this embodiment, the case in which the α-axis support member 62 supports the inner circumference of the α-axis coil 61 over its entire circumference is described, but the present invention is not limited to this. The α-axis support member 62 may support at least a portion of the inner circumference of the α-axis coil 61, including two opposing sides, similar to the β-axis support member 72 described later.

[0043] The β-axis magnetic detection element 8β comprises a β-axis coil 71, which is constructed by winding a conductive wire in an annular shape (for example, clockwise) along the β-axis Oβ extending horizontally from the back to the front of the paper in Figure 3, and a β-axis support member 72, which is provided inside the β-axis coil 71 and supports at least a portion of the inner circumference of the β-axis coil 71 and at least a portion of the α-axis magnetic detection element 8α. In the β-axis magnetic detection element 8β constructed by combining the β-axis coil 71 and the α-axis support member 72 in this way, the center of the β-axis coil 71 is the center of the β-axis magnetic detection element 8β.

[0044] As shown in Figure 3, the inner diameter of the β-axis coil 71 is larger than the outer diameter of the α-axis coil 61. This allows the detection center positions of the β-axis magnetic detection element 8β and the α-axis magnetic detection element 8α to coincide, and the α-axis coil 61 to be positioned inside the larger-diameter β-axis coil 71 so that the β-axis Oβ is perpendicular to the α-axis Oα.

[0045] In this embodiment, the α-axis support member 62 and the β-axis support member 72 are described in the case where they are molded from a non-magnetic material, more specifically from a resin, but the present invention is not limited to this. Both or either of the α-axis support member 62 and the β-axis support member 72 may be molded from a ferromagnetic material or a resin mixed with ferromagnetic material. This allows the α-axis support member 62 and the β-axis support member 72 to be used as cores for the α-axis coil 61 and the β-axis coil 71.

[0046] The γ-axis magnetic detection element 8γ includes a γ-axis coil 81 constructed by winding a conductive wire in a circular (for example, clockwise) manner along the γ-axis Oγ extending downward to the right in Figure 4. In such a γ-axis magnetic detection element 8γ, the center of the γ-axis coil 81 is the center of the γ-axis magnetic detection element 8γ.

[0047] As shown in Figures 3 and 4, the inner diameter of the γ-axis coil 81 is larger than the outer diameters of the α-axis coil 61 and the β-axis coil 71. This allows the detection centers of the three magnetic detection elements 8α, 8β, and 8γ to coincide, the α-axis Oα, β-axis Oβ, and γ-axis Oγ to be arranged in the same arrangement plane, and the γ-axis coil 81 can be positioned outside the α-axis coil 61 and β-axis coil 71, which have smaller diameters than the γ-axis coil 81, so that the α-axis Oα is perpendicular to the β-axis Oβ in the arrangement plane.

[0048] In the sensor unit 7 configured as described above, if we define the angle between the γ axis Oγ and the α axis Oα as "θ" as shown in Figure 4, then the current values ​​(Iu, Iv, Iw) flowing through the three phase current lines and the output values ​​(S) of the three magnetic detection elements are determined. α ,S β ,S γ The following equation (10) holds between ) and ).

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[0049] Furthermore, the angle θ between the γ axis Oγ and the α axis Oα in the arrangement plane is the gain value G of the α-axis magnetic detection element 8α. α and the gain value G of the β-axis magnetic detection element 8ββ Based on the following equation (11-1), if we define it so that it holds, then equation (10) can be transformed into equation (11-2). Therefore, as shown in equation (11-3) below, the gain value G of the γ-axis magnetic detection element 8γ γ By redefining the above equation (11-2), equation (11-2) becomes equivalent to conditional equation (7) imposed on the arrangement layout to satisfy equations (5) and (6). Therefore, when the detection center positions of the three magnetic detection elements 8α, 8β, and 8γ are aligned as shown in Figures 3 and 4, equations (5) and (6) can be satisfied by adjusting the angle θ between the γ axis Oγ and the α axis Oα such that equation (11-1) below is satisfied.

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[0050] Furthermore, as shown in Figure 2, when the three phase current lines 6u, 6v, and 6w are arranged linearly and at equal intervals within the arrangement plane, the detection center positions of these three magnetic detection elements 8α, 8β, and 8γ are placed at predetermined positions on a virtual line L2 that is perpendicular to the virtual line L1 passing through each phase current line 6u, 6v, and 6w and passes through the central V-phase current line 6v, and by setting θ = π / 4, the above equation (11-2) can be transformed as shown in the following equation (12). The following equation (12) is equivalent to conditional equation (9) imposed on the arrangement layout to satisfy the above equations (4-1), (4-2), (5), and (6). Therefore, as shown in Figures 3 and 4, when the detection center positions of the three magnetic detection elements 8α, 8β, and 8γ are made to coincide, the above equations (4-1), (4-2), (5), and (6) can be satisfied by placing these detection center positions at predetermined positions defined on the virtual line L2 and setting θ = π / 4.

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[0051] The current detection device 3 according to this embodiment provides the following effects. (1) The current detection device 3 detects the current flowing through the three phase current lines 6u, 6v, and 6w based on three magnetic detection elements 8α, 8β, and 8γ provided around these phase current lines 6u, 6v, and 6w. More specifically, the current value acquisition unit 22 acquires the output values ​​S of the α-axis and β-axis magnetic detection elements 8α and 8β when they are functioning normally. α ,S β α-phase and β-phase current values ​​I α ,I β The current is obtained as follows. In the current detection device 3, the relative position of the γ-axis magnetic detection element 8γ with respect to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axis are determined so that the above equation (7) holds true. As a result, the current value acquisition unit 22 obtains the output values ​​(S) of the α-axis and γ-axis magnetic detection elements 8α and 8γ in the event of a failure of the β-axis magnetic detection element 8β. α ,S γ The difference value S obtained using ) γ / G γ -S α β-phase current value I β The output values ​​(S) of the β-axis and γ-axis magnetic detection elements 8β and 8γ are obtained as follows: In the event of a failure of the α-axis magnetic detection element 8α, the output values ​​(S) of the β-axis and γ-axis magnetic detection elements 8β and 8γ are obtained as follows: β ,S γ The difference value S obtained using ) γ / G γ -S β α-phase current value I α This can be obtained as follows. Thus, with the current detection device 3, by arranging the γ-axis magnetic detection element 8γ such that the above equation (7) holds true, even if either the α-axis magnetic detection element 8α or the β-axis magnetic detection element 8β fails, the γ-axis magnetic detection element 8γ can be used to obtain the α-phase and β-phase current values ​​I α ,I β This allows for continuous acquisition of the magnetic detection element. Therefore, according to the current detection device 3, compared to the case where a magnetic detection element is made redundant for each phase, the magnetic detection element can be made redundant without increasing cost or size, and in turn, contribute to improving energy efficiency.

[0052] (2) In the current detection device 3, the size of the current detection device 3 can be made compact by aligning the detection center positions of the three magnetic detection elements 8α, 8β, and 8γ. In the current detection device 3, the detection axes Oα, Oβ, and Oγ of the three magnetic detection elements 8α, 8β, and 8γ are arranged in the same arrangement plane, the α axis Oα and the β axis Oβ are orthogonal to each other, and the angle θ between the γ axis Oγ and the α axis Oα is determined so that the above equation (11-1) holds true. In this way, the three magnetic detection elements 8α, 8β, and 8γ can be arranged so that the above equation (7) holds true while aligning the detection center positions of the three magnetic detection elements 8α, 8β, and 8γ.

[0053] (3) In the current detection device 3, the relative positions of the three magnetic detection elements 8α, 8β, and 8γ with respect to the three phase current lines 6u, 6v, and 6w, and the orientation of the detection axes, are determined such that the above equation (12), which is a matrix operation equivalent to the Clarke transformation, holds true. Therefore, according to the current detection device 3, even if one of the α-axis and β-axis magnetic detection elements 8α and 8β fails, the output values ​​of the remaining normal magnetic detection element and the γ-axis magnetic detection element 8γ are read by the current value acquisition unit 22, thereby directly obtaining the α-phase and β-phase current values ​​I without going through the Clarke transformation calculated by a computer. α ,I β You can continue to acquire it.

[0054] 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]

[0055] V...Electric vehicle M...Motor (three-phase motor) W…Drive wheels 1…Inverter 2…Motor control device 21…AD conversion unit 22...Current value acquisition unit 23...dq conversion section 24... Duty Calculation Unit 25...Failure determination section 4…Resolver 6u…U phase current line 6v…V phase current line 6w…W phase current line 3…Current detection device 7…Sensor unit 8α...α-axis magnetic detection element 8β…β-axis magnetic detection element 8γ…γ-axis magnetic detection element

Claims

1. The current flowing through the first phase current line, second phase current line, and third phase current line of a three-phase motor is detected by α-axis magnetic detection elements, β-axis magnetic detection elements, and γ-axis magnetic detection elements provided around the first, second, and third phase current lines. A current detection device comprising a current value acquisition unit that acquires α-phase current values ​​and β-phase current values ​​based on the output values ​​of the α-axis, β-axis, and γ-axis magnetic detection elements, Let the current values flowing through the first-phase, second-phase, and third-phase current lines be I1, I2, and I3, and let the output values of the α-axis, β-axis, and γ-axis magnetic detection elements be S β３ , β１ , β２ ,S β ,S γ ,and let the gain values of the α-axis, β-axis, and γ-axis magnetic detection elements be G α ,G β ,G γ ,and let the magnetic sensitivity coefficients of the α-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines be k α１ ,k α２ ,k α３ ,and let the magnetic sensitivity coefficients of the β-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines be k β１ ,k β２ ,k β３ ,then the relative positions of the γ-axis magnetic detection element with respect to the first-phase, second-phase, and third-phase current lines and the directions of the detection axes are determined such that the following formula (1) holds The current value acquisition unit, The output value S is normal when the α-axis magnetic detection element is functioning correctly. α The α-phase current value I α Acquired as, The output value S is normal when the β-axis magnetic detection element is functioning correctly. β The β-phase current value I β Acquired as, When the β-axis magnetic detection element fails, the difference value S γ / G γ -S α The β-phase current value I β Acquired as, When the α-axis magnetic detection element fails, the difference value S γ / G γ -S β The α-phase current value I α A current detection device characterized by acquiring as such. [Math 1]

2. The detection center positions of the α-axis, β-axis, and γ-axis magnetic detection elements coincide. The α-axis, which is the detection axis of the α-axis magnetic detection element, the β-axis, which is the detection axis of the β-axis magnetic detection element, and the γ-axis, which is the detection axis of the γ-axis magnetic detection element, are arranged in the same plane. The α-axis is perpendicular to the β-axis in the plane, The current detection device according to claim 1, characterized in that the angle θ between the γ axis and the α axis in the plane is determined such that the following equation (2) holds true. [Math 2]

3. The current detection device according to claim 1 or 2, characterized in that the relative positions of the α-axis, β-axis, and γ-axis magnetic detection elements with respect to the first phase, second phase, and third phase current lines and the orientation of the detection axes are determined such that the following formula (3) holds true. [Math 3]

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