Motor drive system

Abstract

This motor drive system comprises: a motor that includes a rotor and a stator; an inverter circuit that includes a plurality of switching elements and adjusts a drive current to be supplied to the motor by using the switching operations of the plurality of switching elements; a control circuit that controls the switching operations of the plurality of switching elements; an auxiliary circuit that includes an inductor; and a housing that accommodates the motor, the inverter circuit, the control circuit, and the auxiliary circuit. The inductor comprises: a coil through which the drive current flows; and a magnetic body attached to the coil. Each of the magnetic body and the coil extends toroidally along the circumferential direction of a rotary shaft of the rotor.

Description

Motor Drive System

[0001] The present specification relates to a motor drive system.

[0002] Japanese Patent Application Laid-Open Publication No. 2016-158425 discloses a motor drive system including a motor including a rotor and a stator, an inverter circuit including a plurality of switching elements and adjusting a drive current supplied to the motor by the switching operation of the plurality of switching elements, a control circuit controlling the switching operation of the plurality of switching elements, an auxiliary circuit including an inductor, and a housing that accommodates the motor, the inverter circuit, the control circuit, and the auxiliary circuit.

[0003] In the field of motor drive systems, there is a demand for reducing the size of housings. This is because reducing the size of motor drive systems has the advantage of enabling the size of devices that use the motor drive systems as their drive sources to be reduced. This specification provides technology that enables the size of housings to be reduced.

[0004] The motor drive system disclosed in this specification includes a motor including a rotor and a stator, an inverter circuit including a plurality of switching elements that adjusts a drive current supplied to the motor by switching operations of the plurality of switching elements, a control circuit that controls the switching operations of the plurality of switching elements, an auxiliary circuit including an inductor, and a housing that accommodates the motor, the inverter circuit, the control circuit, and the auxiliary circuit. The inductor includes a coil through which the drive current flows and a magnetic body attached to the coil. The magnetic body and the coil each extend in a toroidal shape circumferentially around the rotation axis of the rotor.

[0005] Conventional motor drive systems use inductors that do not contain magnetic material (so-called air-core inductors). In contrast, the above configuration uses an inductor that contains magnetic material in the motor drive system. An inductor that contains magnetic material requires a smaller coil size than an air-core inductor with a similar inductance. Therefore, the above configuration allows the inductor to be smaller than conventional inductors, which in turn allows the housing to be smaller.

[0006] 3. A circuit diagram showing the electrical configuration of the motor drive system 2. A perspective view of the motor drive system 2. A partial cross-sectional view of the motor drive system 2. A cross-sectional view of the motor drive system 2 taken along the IV-IV section in FIG. 3. A cross-sectional view of the motor drive system 2 taken along the V-V section in FIG. 3. A cross-sectional view of the motor drive system 2 taken along the VI-VI section in FIG. 3. A diagram schematically showing examples of inductors 32, 36, 48a, 48b, and 48c provided in the motor drive system 2. A circuit diagram showing the electrical configuration of the motor drive system 202. A diagram schematically showing another example of inductors 32, 36, 48a, 48b, and 48c provided in the motor drive systems 2 and 202. A cross-sectional view of a motor drive system 2 according to a modified example taken along the VI-VI section in FIG. 3.

[0007] In one or more embodiments, the magnetic body may have a cylindrical shape that is aligned in a circumferential direction of the rotation axis, and the coil may have a linear shape and be wound around the magnetic body so as to pass alternately on the radially outer side and the radially inner side of the magnetic body.

[0008] The inductor provided in the motor drive system disclosed in JP 2016-158425 A has a coil wound around the rotor's rotational axis. Therefore, when a current flows through the coil, a relatively large magnetic flux is generated along the rotor's rotational axis. As a result, eddy currents are generated in the output shaft, etc., fixed to the rotor, which may result in unintended eddy current loss. In contrast, with the above configuration, the inductor is formed by winding a linear coil around a cylindrical magnetic body that is aligned along the rotor's rotational axis, with the coil passing alternately radially outside and inside the magnetic body. Therefore, even if a current flows through the coil, the magnetic flux generated by the current is primarily aligned along the rotor's rotational axis. This prevents large magnetic flux from being generated along the rotor's rotational axis, thereby preventing eddy currents from being generated in the output shaft, etc., fixed to the rotor. Therefore, unintended eddy current loss can be prevented.

[0009] In one or more embodiments, the coil may have a roll shape in which a conductive material is wound in a roll shape along a circumferential direction of the rotation shaft, and the magnetic material may have a linear shape and be wound around the coil so as to pass alternately on the radially outer side and the radially inner side of the coil.

[0010] The inductor provided in the motor drive system disclosed in JP 2016-158425 A has a coil wound around the rotor's rotational axis. Therefore, when a current flows through the coil, a relatively large magnetic flux is generated along the rotor's rotational axis. As a result, eddy currents are generated in the output shaft, etc., fixed to the rotor, which may result in unintended eddy current loss. In contrast, with the above configuration, the inductor has a roll-shaped coil that is circumferentially aligned with the rotational axis, and a linear magnetic body is wound around the coil so that the magnetic body passes alternately on the radially outer and inner sides of the coil. Therefore, even if a current flows through the coil, the magnetic flux generated by the current is absorbed by the magnetic body and does not reach the rotor. This prevents a large magnetic flux from being generated along the rotor's rotational axis, thereby preventing eddy currents from being generated in the output shaft, etc., fixed to the rotor. Therefore, unintended eddy current loss can be prevented.

[0011] In one or more embodiments, the plurality of switching elements may be disposed on an interior surface of the housing.

[0012] The multiple switching elements of the inverter circuit generate a large amount of heat, and if the heat generated by the multiple switching elements accumulates within the housing, the temperature inside the housing may become excessively high. With the above configuration, the multiple switching elements are arranged on the inner surface of the housing, so the heat generated by the multiple switching elements is easily dissipated to the outside of the housing. This prevents the heat generated by the multiple switching elements from being accumulated within the housing, and prevents the temperature inside the housing from becoming excessively high.

[0013] In one or more embodiments, the inner surface of the housing may have at least one curved region that curves along a circumferential direction of the rotation axis, and at least one of the plurality of switching elements may be disposed on the at least one curved region.

[0014] According to the above configuration, the efficiency of dissipating heat generated by the switching elements to the outside of the housing can be improved compared to when the switching elements are arranged on a flat area of ​​the housing.

[0015] In one or more embodiments, the inductor may be disposed radially outward of the rotor and the stator relative to the rotational axis.

[0016] When increasing the rotation speed of a motor, the rotor diameter may be reduced to reduce the load (centrifugal force) on the rotor, and the axial length of the rotor may be increased instead. Therefore, if other components are positioned axially offset from the rotor, the housing size may become excessively large in the axial direction. With the above configuration, the inductor is positioned radially outward of the rotor and stator, rather than being axially offset from the rotor. This allows the housing size to be reduced in the axial direction.

[0017] In one or more embodiments, the control circuit may be disposed radially outward of the rotor and the stator with respect to the axis of rotation.

[0018] According to the above configuration, the control circuit is disposed radially outward of the rotor and stator rather than at a position axially offset from the rotor, which allows the size of the housing to be reduced in the axial direction.

[0019] In one or more embodiments, the plurality of switching elements may be arranged radially outward of the rotor and the stator.

[0020] According to the above configuration, the switching elements are arranged radially outward of the rotor and the stator rather than at positions offset from the rotor in the axial direction, which allows the housing to be made smaller in size in the axial direction.

[0021] In one or more embodiments, the auxiliary circuit may further include a capacitor, which may extend toroidally around the rotation axis.

[0022] According to the above configuration, the capacitor extends toroidally along the circumferential direction of the rotating shaft, which allows the capacitor to be disposed along the inductor, thereby making effective use of the space within the housing.

[0023] In one or more embodiments, the capacitor may be disposed radially outward of the rotor and the stator relative to the rotational axis.

[0024] According to the above configuration, the capacitor is disposed radially outward of the rotor and the stator, rather than at a position offset from the rotor in the axial direction, which allows the size of the housing to be reduced in the axial direction.

[0025] In one or more embodiments, the inductor and the capacitor may lie in the same plane perpendicular to the axis of rotation.

[0026] If the inductor and capacitor are offset from each other in the axial direction of the rotating shaft, the space available for arranging other components within the housing may be reduced in the axial direction. According to the above configuration, the inductor and capacitor are not offset from each other in the axial direction of the rotating shaft, and instead overlap each other in the radial direction of the rotating shaft. This allows the space available for arranging other components within the housing to be expanded in the axial direction.

[0027] In one or more embodiments, the inductor may be positioned radially outward of the capacitor in the same plane.

[0028] Inductors generate more heat than capacitors. If the heat generated by the inductor is trapped inside the housing, the temperature inside the housing may become excessively high. With the above configuration, the inductor is positioned closer to the outside of the housing than the capacitor (i.e., radially outward from the rotating shaft), making it easier for the heat generated by the inductor to dissipate to the outside of the housing. This prevents the heat generated by the inductor from being trapped inside the housing, and prevents the temperature inside the housing from becoming excessively high.

[0029] In one or more embodiments, the auxiliary circuit may include a first auxiliary circuit including a first inductor and a first capacitor, and a second auxiliary circuit including a second inductor and a second capacitor, and the first inductor, the second inductor, the first capacitor, and the second capacitor may be located on the same plane perpendicular to the axis of rotation.

[0030] If the first inductor, the first capacitor, the second inductor, and the second capacitor were offset from one another in the axial direction of the rotating shaft, the space available for arranging other components within the housing could be reduced in the axial direction. According to the above configuration, the first inductor, the first capacitor, the second inductor, and the second capacitor are not offset from one another in the axial direction of the rotating shaft, and the first inductor, the first capacitor, the second inductor, and the second capacitor overlap with one another in the radial direction of the rotating shaft. This allows the space available for arranging other components within the housing to be expanded in the axial direction.

[0031] In one or more embodiments, the first inductor and the second inductor may be disposed radially outward of the first capacitor and the second capacitor in the same plane.

[0032] The first inductor and the second inductor generate more heat than the first capacitor and the second capacitor. If the heat generated by the first inductor and the second inductor is trapped inside the housing, the temperature inside the housing may become excessively high. With the above configuration, the first inductor and the second inductor are disposed closer to the outside of the housing than the first capacitor and the second capacitor (i.e., radially outward from the rotating shaft). This makes it easier for the heat generated by the first inductor and the second inductor to be dissipated to the outside of the housing. This prevents the heat generated by the first inductor and the second inductor from being trapped inside the housing, thereby preventing the temperature inside the housing from becoming excessively high.

[0033] In one or more embodiments, the first auxiliary circuit may be a filter circuit that filters the drive current, and the second auxiliary circuit may be a boost circuit that boosts the drive current.

[0034] According to the above configuration, the drive current supplied to the motor can be filtered and the drive current can be boosted.

[0035] In one or more embodiments, the housing may have a cylindrical shape extending along the axial direction of the rotation shaft.

[0036] According to the above configuration, the housing has a simple shape, so that the motor drive system can be easily mounted on an external device.

[0037] First Embodiment As shown in FIG. 1 , a motor drive system 2 includes a motor 4 and an inverter device 5. The inverter device 5 includes a first filter circuit 6, a boost circuit 8, an inverter circuit 10, a second filter circuit 12, and a control circuit 14. The motor 4, the first filter circuit 6, the boost circuit 8, the inverter circuit 10, the second filter circuit 12, and the control circuit 14 are housed in a housing 16 shown in FIG. 2 . The motor drive system 2 drives the motor 4 using power supplied from a power source 18 to generate power. The power source 18 may be an external power source (e.g., a commercial power source) located outside the housing 16, or may be a battery pack built into the housing 16. The motor drive system 2 is mounted on a device that performs mechanical operations (e.g., a robot arm) to operate the device.

[0038] As shown in FIG. 3 , the motor 4 includes a rotor 22 including a permanent magnet (not shown) and a stator 24 including three-phase (U-phase, V-phase, and W-phase) coils (not shown). The motor 4 of this embodiment is an inner-rotor DC brushless motor in which the rotor 22 is disposed inside the stator 24. An output shaft 26 is fixed to the rotor 22. The output shaft 26 is supported by the housing 16 via bearings 28 and 30. The housing 16 has a cylindrical shape extending along the axial direction of the rotation axis A of the rotor 22 and the output shaft 26. Power generated by the motor 4 is transmitted to a mechanism (not shown) outside the housing 16 via the output shaft 26.

[0039] 1, the first filter circuit 6, the boost circuit 8, the inverter circuit 10, and the second filter circuit 12 are each provided on a conduction path from a power supply 18 to the motor 4. Power from the power supply 18 is output to the motor 4 via the first filter circuit 6, the boost circuit 8, the inverter circuit 10, and the second filter circuit 12 in this order.

[0040] The first filter circuit 6 includes an inductor 32 and a capacitor 34. The inductor 32 is a so-called choke coil. The first filter circuit 6 is provided in the conductive path between the power supply 18 and the boost circuit 8, and filters the current flowing through the conductive path.

[0041] The boost circuit 8 includes an inductor 36, a switching element 38, a diode 40, and a capacitor 42. The switching element 38 is, for example, a GaN field effect transistor (GaNFET). The boost circuit 8 boosts the DC power input from the power supply 18 via the first filter circuit 6, and outputs the DC power to the inverter circuit 10. The boost ratio of the boost circuit 8 is adjusted by changing the duty ratio (ratio of ON period to OFF period) of the switching element 38.

[0042] The inverter circuit 10 includes six switching elements 44 and three current sensors 46u, 46v, and 46w. Each of the six switching elements 44 is, for example, a metal oxide semiconductor field effect transistor (MOSFET). Each of the six switching elements 44 performs a switching operation in response to instructions from the control circuit 14 to convert DC power input from the boost circuit 8 into AC power and output the AC power to the motor 4 via the second filter circuit 12. The three current sensors 46u, 46v, and 46w are provided corresponding to the coils of each phase of the motor 4. Each of the three current sensors 46u, 46v, and 46w detects the magnitude (current value) of the current Iu, Iv, and Iw supplied to the coil of the corresponding phase and outputs the detected current value Iu, Iv, and Iw to the control circuit 14.

[0043] The second filter circuit 12 includes three inductors 48a, 48b, and 48c and three capacitors 50a, 50b, and 50c. The second filter circuit 12 filters the current supplied to the coils of each phase of the motor 4.

[0044] The motor drive system 2 further includes a rotation detection sensor 52 that detects the rotation of the rotor 22 (see FIG. 3 ). The rotation detection sensor 52 detects the rotation speed Vr of the rotor 22, for example, by observing the displacement of the magnetic poles of the permanent magnets included in the rotor 22. The rotation detection sensor 52 outputs the detected rotation speed Vr of the rotor 22 to the control circuit 14.

[0045] The control circuit 14 includes a processor 54 and a memory 56. The processor 54 controls each component of the motor drive system 2 by executing processing in accordance with a computer program stored in the memory 56. For example, when a command value C (e.g., a torque command value, a speed command value) related to the output of the motor 4 is externally provided, the processor 54 controls each component of the motor drive system 2 so that the output of the motor 4 matches the command value C. In this case, the processor 54 of the present embodiment can perform so-called vector control, which controls the boost circuit 8 and the inverter circuit 10 based on the command value C, the rotation speed Vr of the rotor 22 output from the rotation detection sensor 52, and the current values ​​Iu, Iv, and Iw output from the three current sensors 46u, 46v, and 46w, respectively.

[0046] 3 , in the radial direction of the rotation axis A, the inductor 32 and capacitor 34 of the first filter circuit 6, the inductor 36 and capacitor 42 of the boost circuit 8, the inductors 48a, 48b, 48c and capacitors 50a, 50b, 50c of the second filter circuit 12, the inverter circuit 10, and the control circuit 14 are disposed outside the rotor 22 and the stator 24. The inductors 48a, 48b, 48c and capacitors 50a, 50b, 50c of the second filter circuit 12 are offset in the axial direction of the rotation axis A from the inductor 32 and capacitor 34 of the first filter circuit 6 and the inductor 36 and capacitor 42 of the boost circuit 8. The inverter circuit 10 and the control circuit 14 are offset in the axial direction of the rotation axis A with respect to the inductor 32 and capacitor 34 of the first filter circuit 6, the inductor 36 and capacitor 42 of the boost circuit 8, and the inductors 48a, 48b, 48c and capacitors 50a, 50b, 50c of the second filter circuit 12.

[0047] As shown in FIG. 4 , the inductor 32 and capacitor 34 of the first filter circuit 6, and the inductor 36 and capacitor 42 of the boost circuit 8 are located on the same plane (IV-IV cross section) perpendicular to the rotation axis A. The inductor 32 and capacitor 34 of the first filter circuit 6, and the inductor 36 and capacitor 42 of the boost circuit 8 each extend toroidally along the circumferential direction of the rotation axis A. In the IV-IV cross section, the inductors 32 and 36 are located radially outward of the capacitors 34 and 42. Because the inductors 32 and 36 generate more heat than the capacitors 34 and 42, arranging the inductors 32 and 36 closer to the outside of the housing 16 than the capacitors 34 and 42 (i.e., radially outward of the rotation axis A) can prevent heat from building up inside the housing 16.

[0048] As shown in FIG. 5 , the inductor 48a and capacitor 50a of the second filter circuit 12 are located on the same plane (V-V cross section) perpendicular to the rotation axis A. The inductor 48a and capacitor 50a of the second filter circuit 12 each extend toroidally along the circumferential direction of the rotation axis A. In the V-V cross section, the inductor 48a is located radially outward of the capacitor 50a. Because the inductor 48a generates more heat than the capacitor 50a, locating the inductor 48a closer to the outside of the housing 16 than the capacitor 50a (i.e., radially outward from the rotation axis A) can prevent heat from building up inside the housing 16. Although not shown, the same can be said for the inductors 48b and 48c and capacitors 50b and 50c of the second filter circuit 12.

[0049] As shown in FIG. 6 , the six switching elements 44 of the inverter circuit 10 are mounted on substrates 58a, 58b, and 58c. Two switching elements 44 are mounted on each of the substrates 58a, 58b, and 58c. The substrates 58a, 58b, and 58c have a curved shape that conforms to the inner circumferential surface of the housing 16 and are disposed on the inner circumferential surface of the housing 16. In a cross section perpendicular to the rotation axis A (cross section VI-VI), the substrates 58a, 58b, and 58c are disposed in an arc shape centered on the rotation axis A. By disposing the substrates 58a, 58b, and 58c, on which the six switching elements 44 are mounted, on the inner circumferential surface of the housing 16, heat generated by the six switching elements 44 is more easily dissipated to the outside of the housing 16.

[0050] As shown in FIG. 7 , the inductor 32 of the first filter circuit 6, the inductor 36 of the boost circuit 8, and the inductors 48a, 48b, and 48c of the second filter circuit 12 each include a cylindrical magnetic body 62 extending along the rotation axis A and a linear coil 64 wound around the cylindrical magnetic body 62. The cylindrical magnetic body 62 is formed by winding a plate 66 made of a magnetic material (e.g., steel) having a thickness of 1 μm to 4 μm into a cylindrical shape. That is, the cylindrical magnetic body 62 has a cylindrical shape that extends circumferentially around the rotation axis A. The dimensions (e.g., diameter, height) of the cylindrical magnetic body 62 differ between the inductor 32, the inductor 36, and the inductors 48a, 48b, and 48c. The linear coil 64 is a wire made of a conductive material (e.g., copper) and is wound around the cylindrical magnetic body 62 so as to alternately pass through the radially outer and inner sides of the cylindrical magnetic body 62.

[0051] Although not shown, the linear coil 64 is covered with an insulating film (for example, a resin film or a paper film). The insulating film insulates the cylindrical magnetic body 62 from the linear coil 64.

[0052] Second Embodiment A motor drive system 202 shown in Fig. 8 includes substantially the same components as the motor drive system 2 of the first embodiment. The motor drive system 202 differs from the motor drive system 2 of the first embodiment in that it includes a motor 204 instead of the motor 4 and an inverter circuit 210 instead of the inverter circuit 10. For simplification, Fig. 8 does not include illustrations of a filter circuit corresponding to the second filter circuit 12, current sensors corresponding to the current sensors 46u, 46v, and 46w, and a rotation detection sensor corresponding to the rotation detection sensor 52.

[0053] The motor 204 is an inner rotor type DC brushless motor similar to that of the first embodiment. However, the motor 204 is a motor in which the coils of each phase are not connected, and does not have a neutral point. The inverter circuit 210 includes four switching elements 244u that adjust the current supplied to the U-phase coil of the motor 204, four switching elements 244v that adjust the current supplied to the V-phase coil of the motor 204, and four switching elements 244w that adjust the current supplied to the W-phase coil of the motor 204.

[0054] In a configuration in which the motor has a neutral point, when the voltages applied to each phase of the motor become unbalanced, a current (also called a zero-phase current) may flow through the neutral point. The zero-phase current may lead to a decrease in the energy efficiency of the motor and a decrease in the motor torque. In contrast, in the motor drive system 202 of this embodiment, the motor 204 does not have a neutral point, so no zero-phase current occurs. This makes it possible to avoid problems caused by the zero-phase current.

[0055] (Example 3) As shown in Figure 9, this example differs from Examples 1 and 2 in that each of the inductors 32, 36, 48a, 48b, and 48c has a linear magnetic body 362 instead of the cylindrical magnetic body 62 and a roll-shaped coil 364 instead of the linear coil 64.

[0056] The roll-shaped coil 364 is formed by winding a plate 366 made of a conductive material (e.g., copper) having a thickness of 1 μm to 4 μm in a roll shape along the circumferential direction of the rotation axis A. That is, the roll-shaped coil 364 has a roll shape along the circumferential direction of the rotation axis A. The dimensions (e.g., diameter, height) of the roll-shaped coil 364 differ among the inductors 32, 36, 48a, 48b, and 48c. The linear magnetic body 362 is a wire made of a magnetic material (e.g., steel) and is wound around the roll-shaped coil 364 so as to alternately pass through the radially outer and radially inner sides of the roll-shaped coil 364.

[0057] Although not shown, insulating layers (e.g., resin layers, paper layers) are arranged between the plates 366 stacked in the radial direction of the rotation axis A. The insulating layers insulate the stacked plates 366 from each other. The linear magnetic material 362 is also coated with an insulating film (e.g., resin film, paper film). The insulating film insulates the linear magnetic material 362 from the roll-shaped coil 364.

[0058] (Correspondence) In Examples 1 and 2, the motor drive system 2 is an example of a "motor drive system." The motor 4 is an example of a "motor." The first filter circuit 6 is an example of an "accessory circuit," a "first accessory circuit," and a "filter circuit." The boost circuit 8 is an example of an "accessory circuit," a "second accessory circuit," and a "boost circuit." The inverter circuit 10 is an example of an "inverter circuit." The second filter circuit 12 is an example of an "accessory circuit." The control circuit 14 is an example of a "control circuit." The housing 16 is an example of a "housing." The rotor 22 is an example of a "rotor." The stator 24 is an example of a "stator." The inductor 32 is an example of an "inductor" and a "first inductor." The capacitor 34 is an example of a "capacitor" and a "first capacitor." The inductor 36 is an example of an "inductor" and a "second inductor." The capacitor 42 is an example of a "capacitor" and a "second capacitor." The switching element 44 is an example of a "plurality of switching elements." The inductors 48a, 48b, and 48c are examples of "inductors." The capacitors 50a, 50b, and 50c are examples of "capacitors." The cylindrical magnetic body 62 is an example of a "magnetic body." The linear coil 64 is an example of a "coil." The motor drive system 202 is an example of a "motor drive system." The motor 204 is an example of a "motor." The inverter circuit 210 is an example of an "inverter circuit." The switching elements 244u, 244v, and 244w are examples of "plurality of switching elements." The linear magnetic body 362 is an example of a "magnetic body." The linear coil 64 is an example of a "coil."

[0059] (Modifications) The motor drive system 2, 202 may not include the first filter circuit 6. Alternatively, the motor drive system 2, 202 may not include the boost circuit 8. Alternatively, the motor drive system 2, 202 may not include the second filter circuit 12.

[0060] The first filter circuit 6 does not necessarily have to include the capacitor 34 .

[0061] The second filter circuit 12 does not necessarily have to include the capacitors 50a, 50b, and 50c.

[0062] The substrates 58a, 58b, and 58c on which the six switching elements 44 are mounted do not have to be disposed on the inner circumferential surface of the housing 16. For example, the substrates 58a, 58b, and 58c may be disposed at positions spaced apart from the inner circumferential surface of the housing 16.

[0063] 10, the housing 16 may include a flat portion 16f. At least one of the substrates 58a, 58b, and 58c (substrate 58b in the example of FIG. 10) may be disposed on the inner surface of the flat portion 16f.

[0064] The inductor 32 of the first filter circuit 6 may be arranged at a position offset in the axial direction from the rotor 22 and the stator 24 instead of being arranged radially outside the rotor 22 and the stator 24 .

[0065] The capacitor 34 of the first filter circuit 6 may be arranged at a position offset in the axial direction from the rotor 22 and the stator 24 instead of being arranged radially outside the rotor 22 and the stator 24 .

[0066] The inductor 36 of the boost circuit 8 may be arranged at a position offset in the axial direction from the rotor 22 and the stator 24 instead of being arranged radially outside the rotor 22 and the stator 24 .

[0067] The capacitor 42 of the boost circuit 8 may be arranged at a position offset in the axial direction from the rotor 22 and the stator 24 instead of being arranged radially outside the rotor 22 and the stator 24 .

[0068] The inductors 48 a , 48 b , 48 c of the second filter circuit 12 may be arranged at positions axially offset from the rotor 22 and the stator 24 instead of being arranged radially outward from the rotor 22 and the stator 24 .

[0069] The capacitors 50 a , 50 b , 50 c of the second filter circuit 12 may be arranged at positions axially offset from the rotor 22 and the stator 24 instead of being arranged radially outside the rotor 22 and the stator 24 .

[0070] Instead of being disposed radially outside the rotor 22 and the stator 24 , the inverter circuit 10 may be disposed at a position offset in the axial direction from the rotor 22 and the stator 24 .

[0071] Instead of being disposed radially outward from the rotor 22 and the stator 24 , the control circuit 14 may be disposed at a position axially offset from the rotor 22 and the stator 24 .

[0072] The inductors 32, 36 may be disposed radially inward of the capacitors 34, 42.

[0073] The inductors 32, 36 and the capacitors 34, 42 may be offset from each other in the axial direction of the rotation axis A. That is, the inductors 32, 36 and the capacitors 34, 42 do not have to be located on the same plane perpendicular to the rotation axis A.

[0074] The inductor 48a (or the inductor 48b or the inductor 48c) may be disposed radially inside the capacitor 50a (or the capacitor 50b or the capacitor 50c).

[0075] The inductor 48a (or the inductor 48b or the inductor 48c) and the capacitor 50a (or the capacitor 50b or the capacitor 50c) may be offset from each other in the axial direction of the rotation axis A. That is, the inductor 48a (or the inductor 48b or the inductor 48c) and the capacitor 50a (or the capacitor 50b or the capacitor 50c) do not have to be located on the same plane perpendicular to the rotation axis A.

[0076] Some of the inductors 32, 36, 48a, 48b, and 48c may have the configuration shown in FIG. 7, and the remaining inductors 32, 36, 48a, 48b, and 48c may have the configuration shown in FIG.

[0077] The motor drive system 2 may include a plurality of components (also referred to as drive units) each including a motor 4, a first filter circuit 6, a boost circuit 8, an inverter circuit 10, a second filter circuit 12, and a control circuit 14. In this example, the plurality of drive units may be housed in a single housing 16. Alternatively, the plurality of drive units may each be housed in a separate housing 16.

[0078] The technical elements described in this specification or drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations set forth in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. A motor drive system comprising: a motor including a rotor and a stator; an inverter circuit including a plurality of switching elements that adjusts a drive current supplied to the motor by switching operations of the plurality of switching elements; a control circuit that controls the switching operations of the plurality of switching elements; an auxiliary circuit including an inductor; and a housing that contains the motor, the inverter circuit, the control circuit, and the auxiliary circuit, wherein the inductor has a coil through which the drive current flows, and a magnetic body attached to the coil, each of the magnetic body and the coil extending in a toroidal shape circumferentially around the rotation axis of the rotor.

2. The motor drive system of claim 1, wherein the magnetic body has a cylindrical shape that follows the circumferential direction of the rotating shaft, and the coil has a linear shape and is wound around the magnetic body so as to pass alternately on the radially outer side and the radially inner side of the magnetic body.

3. The motor drive system of claim 1, wherein the coil has a roll shape in which a conductive material is wound in a roll shape around the circumferential direction of the rotating shaft, and the magnetic material has a linear shape and is wound around the coil so as to pass alternately on the radially outer side and the radially inner side of the coil.

4. The motor drive system according to claim 1, wherein the plurality of switching elements are disposed on an inner surface of the housing.

5. The motor drive system according to claim 4, wherein the inner surface of the housing has at least one curved region that curves along the circumferential direction of the rotation shaft, and at least one of the plurality of switching elements is disposed on the at least one curved region.

6. The motor drive system according to claim 1, wherein the inductor is disposed outside the rotor and the stator in the radial direction of the rotation shaft.

7. The motor drive system according to claim 1, wherein the control circuit is disposed outside the rotor and the stator in the radial direction of the rotation shaft.

8. The motor drive system according to claim 1, wherein the plurality of switching elements are arranged outside the rotor and the stator in the radial direction of the rotating shaft.

9. The motor drive system according to claim 1, wherein the auxiliary circuit further includes a capacitor, and the capacitor extends in a toroidal shape along the circumferential direction of the rotating shaft.

10. The motor drive system according to claim 9, wherein the capacitor is disposed outside the rotor and the stator in the radial direction of the rotating shaft.

11. The motor drive system according to claim 9, wherein the inductor and the capacitor are located on the same plane perpendicular to the rotation axis.

12. The motor drive system according to claim 11, wherein the inductor is disposed radially outward of the capacitor in the same plane.

13. The motor drive system of claim 9, wherein the auxiliary circuit comprises a first auxiliary circuit including a first inductor and a first capacitor, and a second auxiliary circuit including a second inductor and a second capacitor, and the first inductor, the second inductor, the first capacitor, and the second capacitor are located on the same plane perpendicular to the rotation axis.

14. The motor drive system according to claim 13, wherein the first inductor and the second inductor are arranged radially outward of the first capacitor and the second capacitor in the same plane.

15. The motor drive system according to claim 13, wherein the first auxiliary circuit is a filter circuit that filters the drive current, and the second auxiliary circuit is a boost circuit that boosts the drive current.

16. The motor drive system according to claim 1, wherein the housing has a cylindrical shape extending along the axial direction of the rotating shaft.

Images