Current detection device

Abstract

To provide a current detection device for a three-phase motor with high toughness in preventing misalignment of the magnetic detection element relative to each phase current line. [Solution] The current detection device detects the current flowing through three busbars and comprises an α-axis magnetic detection element and a β-axis magnetic detection element 8β provided around the three busbars. A slit S extending in the width direction is formed in the V-phase busbar 6v. The detection axis Oβ of the β-axis magnetic detection element 8β is orthogonal to the V-phase busbar 6v and is positioned orthogonal to the width direction of the V-phase busbar 6v on the β-axis element arrangement plane Pβ which includes the detection center of the β-axis magnetic detection element 8β. The detection center of the β-axis magnetic detection element 8β is located at the center of the V-phase busbar 6v in the width direction when viewed along the detection axis Oβ of the β-axis magnetic detection element 8β, and is offset by a predetermined distance a from the slit S along the extending direction of the V-phase busbar 6v.

Description

[Technical Field]

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

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

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

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

[0005] Thus, in the motor control device, in order to perform feedback control of current on the d-q 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 as shown in, for example, Patent Document 1, into d-axis current and q-axis current. More specifically, in the motor control device, first, the three-phase current (Iu, Iv, Iw) detected by the current detection device is converted into two-phase current (Iα, Iβ) defined in the stationary coordinate system by Clark transformation, and then this two-phase current (Iα, Iβ) is converted into two-phase current (Id, Iq) defined in the d-q coordinate system by Park transformation using the rotation angle θ of the motor. In this way, in the vector control using the output of the conventional current detection device, it is necessary to execute an operation for converting the three-phase current (Iu, Iv, Iw) into the two-phase current (Id, Iq) in the motor control device.

[0006] In addition, in Patent Document 2 by the applicant of the present application, there is described a technique (hereinafter, such a technique is also referred to as "spatial Clark transformation") for directly obtaining two-phase current (Iα, Iβ) without going through Clark transformation by computer operation by providing two magnetic detection elements at geometrically determined positions around three phase current lines. According to such spatial Clark transformation, it is possible to reduce the number of magnetic detection elements and also reduce the computational load of the computer compared with the conventional case.

[0007] However, in Patent Document 2, the influence of the positional deviation of the magnetic detection element with respect to each phase current line has not been sufficiently studied. That is, in the spatial Clark transformation technique as shown in Patent Document 2, if the installation position of the magnetic detection element deviates from the initial ideal installation position, the relative position of this magnetic detection element with respect to each phase current line also deviates, so the influence of the positional deviation is considered to be large.

[0008] An object of the present invention is to provide a current detection device for a three-phase motor with high positional deviation toughness with respect to each phase current line of a magnetic detection element, and ultimately to contribute to the improvement of energy efficiency.

Means for Solving the Problem

[0009] (1) The current detection device according to the present invention (for example, current detection device 3 described later) detects the current flowing through the first phase 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 an α-axis magnetic detection element (for example, the α-axis magnetic detection element 8α described later) and a β-axis magnetic detection element (for example, the β-axis magnetic detection element 8β described later) provided around the first, second, and third phase busbars, and the second phase busbar has a slit extending in the width direction. A slit (for example, the slit S described later) is formed, and the detection axis of the β-axis magnetic detection element (for example, the detection axis Oβ described later) is orthogonal to the width direction of the second phase busbar on a β-axis element arrangement surface (for example, the β-axis element arrangement surface Pβ described later) that is orthogonal to the second phase busbar and includes the detection center of the β-axis magnetic detection element, and the detection center of the β-axis magnetic detection element is located at the center in the width direction of the second phase busbar when viewed along the detection axis of the β-axis magnetic detection element and offset from the slit along the extending direction of the second phase busbar.

[0010] (2) In this case, it is preferable that the first phase, second phase, and third phase busbars are arranged at equal intervals on the β-axis element arrangement plane, with the second phase busbar as the center and along a straight line in the width direction of the second phase busbar.

[0011] (3) In this case, it is preferable that the output value of the α-axis magnetic detection element is 90° out of phase with respect to the output value of the β-axis magnetic detection element. [Effects of the Invention]

[0012] (1) The current detection device according to the present invention comprises an α-axis magnetic detection element and a β-axis magnetic detection element provided around three busbars, and detects the current flowing through the three busbars based on the output values ​​of these two magnetic detection elements. In the present invention, the detection axis of the β-axis magnetic detection element is positioned perpendicular to the second phase busbar and perpendicular to the width direction of the second phase busbar on the β-axis element arrangement plane which includes the detection center of the β-axis magnetic detection element, and the detection center of the β-axis magnetic detection element is positioned in the center of the width direction of the second phase busbar in a plan view along the detection axis of the β-axis magnetic detection element. As a result, the detection axis of the β-axis magnetic detection element is perpendicular to the magnetic field formed concentrically around it by the current flowing through the second phase busbar on the β-axis element arrangement plane, so that the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the second phase busbar can be set to 0. If the current flows uniformly along the width direction inside the second phase busbar, then if the detection center of the β-axis magnetic detection element is offset from the center of the second phase busbar in the width direction in a plan view, the magnetic sensitivity coefficient of the β-axis magnetic detection element with respect to the second phase busbar will also deviate from zero. In contrast, the present invention forms a slit extending along the width direction in relation to the second phase busbar, and further positions the detection center of the β-axis magnetic detection element at a position offset from the slit along the extending direction of the second phase busbar in a plan view. As a result, as will be explained later with reference to Figures 6A and 6B, the amount of deviation from zero in the magnetic sensitivity coefficient with respect to the positional displacement of the detection center of the β-axis magnetic detection element along the width direction can be reduced. Therefore, according to the present invention, the positional displacement toughness of the β-axis magnetic detection element with respect to the second phase busbar along the width direction can be improved, and this can contribute to the improvement of energy efficiency.

[0013] (2) In the present invention, the first, second, and third phase busbars are arranged at equal intervals on a straight line centered on the second phase busbar and along the width direction of the second phase busbar on the β-axis element arrangement plane. Therefore, according to the present invention, the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element for the first phase busbar and the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element for the third phase busbar are made equal, while the magnetic sensitivity coefficient of the β-axis magnetic detection element for the second phase busbar can be set to 0. Thus, the output value of the β-axis magnetic detection element can be made proportional to the β-phase current value obtained by combining the currents flowing through the first, second, and third phase busbars in a ratio determined by the Clarke transform.

[0014] (3) In the present invention, the phase of the output value of the α-axis magnetic detection element is shifted by 90° relative to the phase of the output value of the β-axis magnetic detection element. Therefore, according to the present invention, the output values ​​of the α-axis magnetic detection element and the β-axis magnetic detection element can be made proportional to the α-phase current value and the β-phase current value obtained by combining the currents flowing through the first phase, second phase, and third phase busbars in a ratio determined by the Clarke transform, respectively. [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 diagram schematically shows the configuration of the sensor unit. [Figure 3] This diagram schematically shows an example of the arrangement of three busbars and an α-axis magnetic detection element on the α-axis element arrangement plane. [Figure 4] This diagram schematically shows an example of the arrangement of three busbars and a β-axis magnetic detection element on the β-axis element arrangement plane. [Figure 5] This diagram shows the V-phase busbar and the β-axis magnetic detection element viewed along the detection axis of the β-axis magnetic detection element. [Figure 6A] This figure shows the distribution of the component of magnetic flux density along the detection axis of the β-axis magnetic detection element on a plane located a predetermined height away from the surface of the portion of the V-phase busbar where no slits are formed. [Figure 6B]This figure shows the distribution of the component of the magnetic flux density along the detection axis of the β-axis magnetic detection element on a plane located at a predetermined height away from the surface of the portion where the slit of the V-phase busbar is formed. [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 an α-axis magnetic detection element 8α and a β-axis magnetic detection element 8β, which are 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 8α and 8β each generate a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each busbar 6u, 6v, and 6w along their respective detection axes. Specific examples of the arrangement layout of these α-axis and β-axis magnetic detection elements 8α and 8β, as well as the three busbars 6u, 6v, and 6w, will be explained later with reference to Figures 2 to 5.

[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 two magnetic detection elements 8α and 8β and the resolver 4.

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

[0023] The AD conversion unit 21 performs AD conversion on the detection signals of the α-axis and β-axis magnetic detection elements 8α and 8β, and thereby obtains the output values (S α , S β ) of these α-axis and β-axis magnetic detection elements 8α and 8β.

[0024] Based on the output values (S α , S β ) of the α-axis and β-axis magnetic detection elements 8α and 8β obtained by the AD conversion unit 21, the current value acquisition unit 22 obtains the α-phase current value I α and the β-phase current value I β corresponding to the two-phase current obtained by performing Clark transformation on the three-phase currents (Iu, Iv, Iw) as shown in the following formula (1-1). In this embodiment, the current value acquisition unit 22 obtains the output values (S α , S β ) of the α-axis and β-axis magnetic detection elements 8α and 8β as the α-phase and β-phase current values (I α , I β ) as they are, and the present invention is not limited to this. For example, as described in Japanese Patent Application No. 2024-017417 filed by the applicant of the present application, the current value acquisition unit 22 multiplies the output values (S α , S β ) of the α-axis and β-axis magnetic detection elements 8α and 8β respectively by a predetermined α-phase gain G α and a β-phase gain G β to obtain the α-phase current value I α and the β-phase current value I β . In this case, the values of these α-phase and β-phase gains (G α , G β ) are set so that the amplitudes of the α-phase and β-phase current values (I α , I β ) are equal. Therefore, in this embodiment, the current detection device 3 that detects the current flowing through the three-phase busbars 6u, 6v, and 6w of the motor M is composed of two magnetic detection elements 8α and 8β, an AD conversion unit 21, and a current value acquisition unit 22.

Equation

[0025] 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.

[0026] 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.

[0027] Figure 2 is a schematic diagram showing the configuration of the sensor unit 7. The sensor unit 7 comprises an α-axis magnetic detection element 8α and a β-axis magnetic detection element 8β provided around three busbars 6u, 6v, and 6w, and a substrate 80 to which these magnetic detection elements 8α and 8β are fixed. That is, the two magnetic detection elements 8α and 8β are arranged around the three busbars 6u, 6v, and 6w in an integrated state by the substrate 80. As shown in Figure 2, the following description will explain the case in which the detection center of the α-axis magnetic detection element 8α is placed in a virtual α-axis element arrangement plane Pα that is orthogonal to the three busbars 6u, 6v, and 6w, and the detection center of the β-axis magnetic detection element 8β is placed in a virtual β-axis element arrangement plane Pβ that is orthogonal to the three busbars 6u, 6v, and 6w and different from the α-axis element arrangement plane Pα, but the present invention is not limited to this. The α-axis element arrangement plane Pα and the β-axis element arrangement plane Pβ may be a common virtual plane. In other words, the detection centers of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β may be located within a common element arrangement plane that is orthogonal to the three busbars 6u, 6v, and 6w.

[0028] Figure 3 schematically shows an example of the arrangement of three busbars 6u, 6v, and 6w and the α-axis magnetic detection element 8α on the α-axis element arrangement plane Pα. In Figure 3, the three busbars 6u, 6v, and 6w are arranged linearly at equal intervals in the order of U-phase busbar 6u, V-phase busbar 6v, and W-phase busbar 6w on the α-axis element arrangement plane Pα, but the present invention is not limited to this. When the three busbars 6u, 6v, and 6w are arranged in this way, the detection axis Oα of the α-axis magnetic detection element 8α is arranged parallel to the imaginary line passing through the three busbars 6u, 6v, and 6w, as shown in Figure 3. Furthermore, the detection center of the α-axis magnetic detection element 8α is positioned at a predetermined location on an imaginary line that is perpendicular to the imaginary line passing through the three busbars 6u, 6v, and 6w and also passes through the central V-phase busbar 6v, as shown in Figure 3. In the following explanation, we will describe the case where the three busbars 6u, 6v, and 6w are rectangular in cross-sectional view and are plate-like in shape extending along the direction of extension, as shown in Figures 2 and 3.

[0029] Here, the output value S of the α-axis magnetic detection element 8α is given. α This is the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the α-axis magnetic detection element 8α. αu ,k αv ,k αw Using ), it can be expressed by the following equation (2-1). These magnetic sensitivity coefficients (k αu ,k αv ,k αw ) are values ​​determined by the relative position of the α-axis magnetic detection element 8α with respect to the three busbars 6u, 6v, and 6w, and the orientation of the detection axis, respectively. More specifically, for example, the magnetic sensitivity coefficient k of the α-axis magnetic detection element 8α with respect to the W-phase busbar 6w. αw It is defined by the following equation (2-2) according to Ampère's law. In the following equation (2-2), μ is the permeability. Also, in the following equation (2-2), θ wα is the angle between the magnetic field vector of the W-phase busbar 6w and the detection axis of the α-axis magnetic detection element 8α, and (x α ,z α ) is the coordinate value of the α-axis magnetic detection element 8α on the α-axis element arrangement plane, and (x w ,z w) is the coordinate value of the W-phase busbar 6w on the α-axis element arrangement plane. Note that other magnetic sensitivity coefficients (k αu ,k αw ) is also defined based on Ampere's law, similar to equation (2-2) below, so a detailed explanation is omitted. As described above, the magnetic sensitivity coefficient (k αu ,k αv ,k αw The position of the α-axis magnetic detection element 8α is determined by its relative position to the three busbars 6u, 6v, and 6w, and the orientation of the detection axis.

number

[0030] Furthermore, the detection center of the α-axis magnetic detection element 8α is located on the α-axis element arrangement surface Pα, where the magnetic sensitivity coefficient (k αu ,k αv ,k αw The α-axis magnetic detection element 8α is positioned such that the following equation (3) holds true. α α-phase current value I α It can be made proportional to that.

number

[0031] Figure 4 schematically shows an example of the arrangement of three busbars 6u, 6v, and 6w and a β-axis magnetic detection element 8β on the β-axis element arrangement surface Pβ.

[0032] As shown in Figure 4, the U-phase busbar 6u, V-phase busbar 6v, and W-phase busbar 6w are arranged at equal intervals on a straight line along the width direction of the plate-shaped V-phase busbar, with the V-phase busbar 6v as the center, on the β-axis element arrangement plane Pβ. More specifically, the three busbars 6u, 6v, and 6w are arranged at equal intervals in the order of U-phase busbar 6u, V-phase busbar 6v, and W-phase busbar 6w on a first imaginary line L1 that is parallel to the width direction of these three busbars 6u, 6v, and 6w and passes through the center of each of them, within the β-axis element arrangement plane Pβ.

[0033] As shown in Figure 4, the detection axis Oβ of the β-axis magnetic detection element 8β is positioned perpendicular to the width direction of the V-phase busbar 6v on the β-axis element arrangement plane Pβ. More specifically, the detection center of the β-axis magnetic detection element 8β is positioned on a second virtual line L2 that is perpendicular to the first virtual line L1 described above and passes through the center of the width direction of the central V-phase busbar 6v within the β-axis element arrangement plane Pβ. Furthermore, the detection axis Oβ of the β-axis magnetic detection element 8β is positioned parallel to the second virtual line L2. This makes it possible to make the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the U-phase busbar 6u equal to the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the W-phase busbar 6w, while making the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the V-phase busbar 6v 0. Thus, as shown in equation (4) below, the output value S of the β-axis magnetic detection element 8β β The α-phase current value I α The β-phase current value I is 90° different in phase from the above. β It can be made proportional to this. In the following, the distance along the second virtual line L2 between the detection center of the β-axis magnetic detection element 8β and the center of the V-phase busbar 6v on the β-axis element arrangement plane Pβ will be referred to as the height of the β-axis magnetic detection element 8β relative to the V-phase busbar 6v and will be denoted as "Hz".

number

[0034] Figure 5 shows the V-phase busbar 6v and the β-axis magnetic detection element 8β as viewed along the detection axis Oβ of the β-axis magnetic detection element 8β.

[0035] A slit S is formed in the center of the width direction of the V-phase busbar 6v, extending along the width direction. Here, as shown in Figure 5, the slit S is rectangular when viewed along the detection axis Oβ of the β-axis magnetic detection element 8β. The detection center of the β-axis magnetic detection element 8β is located at the center of the width direction of the V-phase busbar 6v (position x=0 in Figure 5) when viewed along the detection axis Oβ of the β-axis magnetic detection element 8β, as shown in Figure 5, and is offset by a predetermined distance a from the end of the slit S (position y=0 in Figure 5) along the extending direction of the V-phase busbar 6v. Here, the length Ls of the slit S along the width direction is determined based on, for example, the allowable installation error Δx along the width direction of the β-axis magnetic detection element 8β, as will be explained later with reference to Figures 6A and 6B.

[0036] Figures 6A and 6B show the distribution of the component of magnetic flux density along the detection axis Oβ (hereinafter simply referred to as magnetic flux density Bz) on a plane located at a predetermined height Hz away from the surface of the V-phase busbar 6v. More specifically, Figure 6A shows the distribution of magnetic flux density Bz generated around the portion of the V-phase busbar 6v where the slit S is not formed, and Figure 6B shows the distribution of magnetic flux density generated around the portion of the V-phase busbar 6v where the slit S is formed. In Figures 6A and 6B, darker colors are used to indicate increasing absolute values ​​of magnetic flux density Bz.

[0037] As shown in Figure 6A, in the portion of the plate-shaped V-phase busbar 6v where the slit S is not formed, the magnitude and direction of the current density are generally uniform along the width direction of the V-phase busbar 6v. Therefore, the absolute value of the magnetic flux density Bz on the plane located at a height Hz away from the V-phase busbar 6v where the β-axis magnetic detection element 8β is positioned is 0 at the center of the V-phase busbar 6v in the width direction (position x=0 in Figure 6A), and increases as it moves away from this center in the width direction. Therefore, the further the detection center of the β-axis magnetic detection element 8β moves away from the center of the V-phase busbar 6v in the width direction, the greater the magnetic flux density Bz due to the V-phase busbar 6v becomes compared to the output value S of the β-axis magnetic detection element 8β. β The impact will be significant.

[0038] In contrast, as shown in Figure 6B, in the vicinity of the portion where the slit S is formed in the plate-shaped V-phase busbar 6v, the magnitude and direction of the current density are not uniform along the width direction of the V-phase busbar 6v. Therefore, the distribution of magnetic flux density Bz on a surface located a height Hz away from the V-phase busbar 6v differs between the portion near the slit S and the portion further away from the slit S. More specifically, the length along the width direction of the region where the absolute value of the magnetic flux density Bz is approximately 0 (in other words, the region where the absolute value of the magnetic flux density Bz is below a threshold set to a value slightly greater than 0, and which is shown in white in Figures 6A and 6B) (hereinafter also referred to as the "dead zone width") differs between the portion near the slit S and the portion further away from the slit S. More specifically, as shown in Figures 6A and 6B, the dead zone width increases in the following order: Wc directly above the slit S, Wb at a position sufficiently far from the slit S, and Wa at a position offset by a predetermined distance a from the end of the slit S along the extending direction of the V-phase busbar 6v (Wa > Wb > Wc). By forming the slit S in the V-phase busbar 6v in this way, and by positioning the detection center of the β-axis magnetic detection element 8β at a position offset by a distance a determined according to the shape of the slit S, viewed along the detection axis Oβ, from the end of the slit S along the extending direction of the V-phase busbar 6v, the positional displacement toughness of the β-axis magnetic detection element 8β in the width direction relative to the V-phase busbar 6v can be improved compared to when the detection center of the β-axis magnetic detection element 8β is positioned directly above the slit S or sufficiently far from the slit S.

[0039] As shown in Figure 6B, it is thought that increasing the length Ls along the width direction of the slit S will also increase the dead zone width. Therefore, the length Ls along the width direction of the slit S is set to a length corresponding to the allowable installation error Δx along the width direction of the β-axis magnetic detection element 8β. More specifically, the length Ls along the width direction of the slit S is set to a length of at least twice the allowable installation error Δx (i.e., Ls > 2Δx).

[0040] Furthermore, as shown in Figure 6B, the position where the dead zone width is maximum is thought to correlate with the length Ls along the width direction of the slit S. Therefore, the distance a from the position of the detection center of the β-axis magnetic detection element 8β is determined, for example, based on the length Ls along the width direction of the slit S.

[0041] The current detection device 3 according to this embodiment provides the following effects. (1) The current detection device 3 is equipped with an α-axis magnetic detection element 8α and a β-axis magnetic detection element 8β provided around the three busbars 6u, 6v, and 6w, and the output values ​​S of these two magnetic detection elements 8α and 8β α ,S β Based on this, the current I flowing through the three busbars 6u, 6v, and 6w α ,I βThis is detected. In the current detection device 3, the detection axis Oβ of the β-axis magnetic detection element 8β is positioned perpendicular to the width direction of the V-phase busbar 6v on the β-axis element arrangement plane Pβ which is perpendicular to the V-phase busbar 6v and includes the detection center of the β-axis magnetic detection element 8β. The detection center of the β-axis magnetic detection element 8β is positioned in the center of the width direction of the V-phase busbar 6v in a plan view along the detection axis Oβ of the β-axis magnetic detection element 8β. As a result, the detection axis Oβ of the β-axis magnetic detection element 8β is perpendicular to the magnetic field formed concentrically around it by the current flowing through the V-phase busbar 6v on the β-axis element arrangement plane Pβ, so that the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β with respect to the V-phase busbar can be set to 0. However, if the current flows uniformly along the width direction inside the V-phase busbar 6v, and the detection center of the β-axis magnetic detection element 8β is shifted from the center of the width direction of the V-phase busbar 6v in a plan view, the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β with respect to the V-phase busbar 6v will also deviate from 0. In contrast, the current detection device 3 forms a slit S extending along the width direction relative to the V-phase busbar 6v, and further positions the detection center of the β-axis magnetic detection element 8β at a position offset from the slit S along the extending direction of the V-phase busbar 6v in a plan view. This makes it possible to reduce the amount of variation from zero in the magnetic sensitivity coefficient with respect to the positional displacement of the detection center of the β-axis magnetic detection element 8β along the width direction. Therefore, the current detection device 3 can improve the positional displacement toughness of the β-axis magnetic detection element 8β along the width direction relative to the V-phase busbar 6v, and consequently contribute to improving energy efficiency.

[0042] (2) The three busbars 6u, 6v, and 6w are arranged at equal intervals on the β-axis element arrangement plane Pβ, with the V-phase busbar 6v as the center and along a straight line parallel to the width direction of the V-phase busbar 6v. Therefore, the current detection device 3 makes it possible to make the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the u-phase busbar 6u equal to the absolute value of the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the W-phase busbar 6w, while making the magnetic sensitivity coefficient of the β-axis magnetic detection element 8β for the V-phase busbar 6v 0. Thus, the output value of the β-axis magnetic detection element 8β is obtained by combining the currents flowing through the busbars 6u, 6v, and 6w in a ratio determined by the Clarke transform to obtain the β-phase current value I βIt can be made proportional to that.

[0043] (3) In the current detection device 3, the output value S of the α-axis magnetic detection element 8β β The phase is shifted by 90° relative to the phase of the output value of the β-axis magnetic detection element 8. Therefore, according to the current detection device 3, the output values ​​S of the α-axis magnetic detection element 8α and the β-axis magnetic detection element 8β are shifted. α ,S β The α-phase current value I is obtained by combining the currents flowing through the busbars 6u, 6v, and 6w in a ratio determined by the Clark transform. α and β-phase current value I β It can be made proportional to that.

[0044] 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]

[0045] V...vehicle W…Drive wheels M...Motor (three-phase motor) 6u…U-phase busbar (first-phase busbar) 6V...V-phase busbar (second phase busbar) S...Slit 6w...W-phase busbar (third-phase busbar) 1…Inverter (power supply) 2…Motor control device 21…AD conversion unit 22...Current value acquisition unit 23...dq conversion section 24... Duty Calculation Unit 3…Current detection device 8α...α-axis magnetic detection element Oα...Detection axis Pα…α-axis element arrangement surface 8β…β-axis magnetic detection element Oβ...Detection axis Pβ…β-axis element 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, The system comprises α-axis magnetic detection elements and β-axis magnetic detection elements provided around the first, second, and third phase busbars, The second phase busbar has a slit that extends in the width direction. The detection axis of the β-axis magnetic detection element is orthogonal to the second phase busbar and is arranged orthogonal to the width direction of the second phase busbar in the β-axis element arrangement plane that includes the detection center of the β-axis magnetic detection element. The current detection device is characterized in that the detection center of the β-axis magnetic detection element is located at the center in the width direction of the second phase busbar and offset from the slit along the extending direction of the second phase busbar when viewed along the detection axis of the β-axis magnetic detection element.

2. The current detection device according to claim 1, characterized in that the first phase, second phase, and third phase busbars are arranged at equal intervals on a straight line centered on the second phase busbar and along the width direction of the second phase busbar on the β-axis element arrangement surface.

3. The current detection device according to claim 2, characterized in that the output value of the α-axis magnetic detection element is 90° out of phase with respect to the output value of the β-axis magnetic detection element.

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