Motor

Abstract

A motor (1) is provided with a case (10), an electrically conductive shaft (18), bearings (20, 25), a rotor core (30), a coil (15), and electrostatic shields (40, 45). Ring grooves (31a, 31b) are formed in the rotor core (30). The rotor core (30) includes a first core portion (33), a second core portion (34), and a third core portion (35). At least one of the first sore portion (33), the second core portion (34), and the third core portion (35) are formed from an insulating material. The electrostatic shields (40, 45) are disposed between the coil (15) and the electrically conductive shaft (18), and are electrically connected to an electrically conductive case portion. Part of the electrostatic shields (40, 45) is inside the ring grooves (31a, 31b).

Description

[Technical field]

[0001] The present disclosure relates to a motor. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2000-270507 (Patent Document 1) discloses a motor including a stator, a rotor having a rotating shaft, a housing, end brackets, a bearing device, and an electrostatic shielding member. The stator includes a stator core and a coil. The end brackets hold the rotating shaft via the bearing device. The electrostatic shielding member is a non-magnetic metal conductor. The electrostatic shielding member is disposed in the gap between the stator and the rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-270507 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the motor described in Patent Document 1, the electrostatic shielding member is disposed in the gap between the stator and the rotor, so that the electrostatic shielding member is disposed close to the coil. In order to prevent the electrostatic shielding member from adversely affecting the distribution of the magnetic field generated by the coil, the electrostatic shielding member needs to be formed from a non-magnetic material. Therefore, the options for the material of the electrostatic shielding member are limited.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a motor that can prevent the occurrence of electrical corrosion in bearings and can expand the options for materials for the electrostatic shield. [Means for solving the problem]

[0006] The motor of the present disclosure includes a case, a conductive shaft, a bearing, a rotor core, a stator core, a coil, and an electrostatic shield. The case includes a conductive case portion. The conductive shaft is spaced from the case. The bearing supports the conductive shaft rotatably relative to the conductive case portion. The rotor core is fixed to the conductive shaft. The stator core is disposed facing the rotor core. The coil is wound around the stator core. The electrostatic shield is fixed to the conductive case portion. The case houses the bearing, the rotor core, the stator core, the coil, and the electrostatic shield. The bearing includes a conductive outer ring, a conductive inner ring, a plurality of rolling elements, and an insulating lubricant. The conductive outer ring is fixed to the conductive case portion. The conductive inner ring is fixed to the conductive shaft. The plurality of rolling elements are disposed between the conductive outer ring and the conductive inner ring so as to be able to roll. The insulating lubricant is sealed in a bearing space between the conductive outer ring and the conductive inner ring. A ring groove is formed in the rotor core. The rotor core includes a first core portion proximal to the stator core relative to the ring groove, a second core portion proximal to the conductive shaft relative to the ring groove, and a third core portion between the first core portion and the second core portion. At least one of the first core portion, the second core portion, or the third core portion is formed of an insulating material. The electrostatic shield is disposed between the coil and the conductive shaft and is electrically connected to the conductive case portion. A portion of the electrostatic shield is within the ring groove. Effect of the Invention

[0007] The electrostatic shield can shield the conductive shaft from the coil. The electrostatic capacitance between the coil and the conductive shaft is reduced. The potential difference between the coil and the conductive shaft during operation of the motor is increased, and the potential difference between the conductive shaft and the case during operation of the motor is reduced. The insulation breakdown of the insulating lubricant during operation of the motor is prevented, and the axial current is prevented from flowing between the outer ring and the inner ring. The occurrence of electrical corrosion in the inner ring, the outer ring, and the multiple rolling elements can be prevented. In addition, since a part of the electrostatic shield is in the ring groove, the distance between the electrostatic shield and the coil can be increased. As the electrostatic shield, not only non-magnetic materials but also magnetic materials can be selected. The choice of materials for the electrostatic shield can be expanded. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view of a motor according to a first embodiment. [Diagram 2] 1 is a schematic circuit diagram of a motor according to a first embodiment connected to a current supply device. [Diagram 3] FIG. 11 is a schematic cross-sectional view of a motor according to a second embodiment. [Figure 4] FIG. 11 is a schematic cross-sectional view of a motor according to a third embodiment. [Diagram 5] FIG. 11 is a schematic cross-sectional view of a motor according to a fourth embodiment. [Figure 6] FIG. 11 is a schematic cross-sectional view of a motor according to a fifth embodiment. [Figure 7] FIG. 13 is a schematic cross-sectional view of a motor according to a sixth embodiment. [Figure 8] FIG. 13 is a schematic cross-sectional view of a motor according to a seventh embodiment. [Figure 9] FIG. 13 is a schematic cross-sectional view of a motor according to an eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that the same reference numerals are used to refer to the same components, and the description thereof will not be repeated.

[0010] Embodiment 1 A motor 1 according to a first embodiment will be described with reference to Figures 1 and 2. With reference to Figure 1, the motor 1 mainly includes a case 10, a stator core 14, a coil 15, a conductive shaft 18, bearings 20 and 25, a rotor core 30, and electrostatic shields 40 and 45.

[0011] The case 10 accommodates the stator core 14, the coil 15, the bearings 20, 25, the rotor core 30, and the electrostatic shields 40, 45. The case 10 includes a frame 11 and a bracket 12. The frame 11 includes a bottom wall and a side wall. A hole 11a is provided in the frame 11 (bottom wall). The bottom wall of the frame 11 is the bottom wall of the case 10, and the side wall of the frame 11 is the side wall of the case 10. The bracket 12 faces the bottom wall of the frame 11 and is connected to the side wall of the frame 11. The bracket 12 is the top wall of the case 10. The case 10 includes a conductive case part. In this embodiment, both the frame 11 and the bracket 12 are conductive case parts. Both the frame 11 and the bracket 12 are formed of a conductive material such as, for example, steel (for example, carbon steel such as S45C) or alloy steel (for example, stainless steel).

[0012] The stator core 14 is made of a magnetic material. The stator core 14 may be made of, for example, a laminate of electromagnetic steel sheets made by adding silicon to iron or carbon steel. The stator core 14 is fixed to the case 10 (frame 11). Specifically, the stator core 14 is fixed to a side wall of the case 10 (frame 11). The stator core 14 is disposed facing the rotor core 30. The stator core 14 is disposed at a distance g from the rotor core 30 in the radial direction of the rotor core 30. The distance g is the distance between the outer peripheral side surface 30c of the rotor core 30 and the inner peripheral side surface of the stator core 14. The distance g is, for example, 500 μm or less. The stator core 14 surrounds the rotor core 30.

[0013] The coil 15 is wound around the stator core 14. The coil 15 is spaced apart from the rotor core 30. The stator core 14 surrounds the rotor core 30. The coil 15 includes a first coil portion 15a and a second coil portion 15b. The first coil portion 15a is exposed from the stator core 14 and is proximate to a bearing 20 (the bottom wall of the frame 11 or the bottom wall of the case 10) in the axial direction of the conductive shaft 18. The second coil portion 15b is exposed from the stator core 14 and is proximate to a bearing 25 (the bracket 12 or the top wall of the case 10) in the axial direction of the conductive shaft 18. With reference to FIG. 2, the coil 15 includes, for example, a u-phase coil 15u, a v-phase coil 15v, and a w-phase coil 15w.

[0014] 1, the conductive shaft 18 is formed of a conductive material such as steel (e.g., carbon steel such as S45C). The conductive shaft 18 is spaced apart from the case 10. Specifically, the conductive shaft 18 passes through a hole 11a and penetrates a conductive case portion (frame 11). The conductive shaft 18 is spaced apart from the conductive case portion (frame 11, bracket 12).

[0015] The bearings 20, 25 rotatably support the conductive shaft 18 relative to the conductive case portion (the frame 11, the bracket 12). The bearings 20, 25 include outer rings 22, 27, inner rings 21, 26, a plurality of rolling elements 23, 28, and insulating lubricants 24, 29.

[0016] Specifically, the frame 11 is provided with a support wall 11b extending in the axial direction of the conductive shaft 18. The bearing 20 rotatably supports the conductive shaft 18 with respect to the conductive case portion (frame 11). The bearing 20 includes an outer ring 22, an inner ring 21, a plurality of rolling elements 23, and an insulating lubricant 24. The outer ring 22 is fixed to the support wall 11b. The conductive shaft 18 is press-fitted into the inner ring 21. The inner ring 21 and the outer ring 22 are made of a conductive material such as steel (e.g., carbon steel). The plurality of rolling elements 23 are disposed between the outer ring 22 and the inner ring 21 so as to be able to roll freely. The plurality of rolling elements 23 are made of a conductive material such as steel (e.g., carbon steel). The insulating lubricant 24 is, for example, grease or lubricating oil. The insulating lubricant 24 is filled in the bearing space between the outer ring 22 and the inner ring 21.

[0017] The bracket 12 is provided with a support wall 12b extending in the axial direction of the conductive shaft 18. The bearing 25 rotatably supports the conductive shaft 18 with respect to the conductive case portion (bracket 12). The bearing 25 includes an outer ring 27, an inner ring 26, a plurality of rolling elements 28, and an insulating lubricant 29. The outer ring 27 is fixed to the support wall 12b. The conductive shaft 18 is press-fitted into the inner ring 26. The inner ring 26 and the outer ring 27 are made of a conductive material such as steel (e.g., carbon steel). The plurality of rolling elements 28 are disposed between the outer ring 27 and the inner ring 26 so as to be able to roll freely. The plurality of rolling elements 28 are made of a conductive material such as steel (e.g., carbon steel). The insulating lubricant 29 is, for example, grease or lubricating oil. The insulating lubricant 29 is filled in the bearing space between the outer ring 27 and the inner ring 26.

[0018] The rotor core 30 is fixed to the conductive shaft 18. The rotor core 30 is formed of a magnetic material. The rotor core 30 includes a first main surface 30a proximate to the bearing 20 (the bottom wall of the frame 11 or the bottom wall of the case 10), a second main surface 30b proximate to the bearing 25 (the bracket 12 or the top wall of the case 10), and an outer peripheral side surface 30c. The second main surface 30b is opposite to the first main surface 30a. The outer peripheral side surface 30c is connected to the first main surface 30a and the second main surface 30b.

[0019] Ring grooves 31a and 31b are formed in rotor core 30. Ring groove 31a is formed between coil 15 and conductive shaft 18 in the radial direction of rotor core 30.

[0020] The ring groove 31a is formed in the first main surface 30a of the rotor core 30. The ring groove 31a is formed between the first coil portion 15a and the conductive shaft 18 in the radial direction of the rotor core 30. The width W of the ring groove 31a 1 is greater than the gap g between the stator core 14 and the rotor core 30. 1 may be 1.0 mm or more. Therefore, a part of the electrostatic shield 40 can be easily disposed in the ring groove 31a. The dimensional accuracy of the electrostatic shield 40 may be relaxed.

[0021] Distance D between the ring groove 31a and the outer peripheral side surface 30c of the rotor core 30 1 is, for example, 1.0 mm or more. Therefore, the gap between the electrostatic shield 40 and the coil 15 (first coil portion 15a) is increased. The options for the material of the electrostatic shield 40 are increased.

[0022] The ring groove 31b is formed in the second main surface 30b of the rotor core 30. The ring groove 31b is formed between the second coil portion 15b and the conductive shaft 18 in the radial direction of the rotor core 30. The width W of the ring groove 31b 2 is greater than the gap g between the stator core 14 and the rotor core 30. 2may be 1.0 mm or more. Therefore, a part of the electrostatic shield 45 can be easily disposed in the ring groove 31b. The dimensional accuracy of the electrostatic shield 45 may be relaxed.

[0023] Distance D between the ring groove 31b and the outer peripheral side surface 30c of the rotor core 30 2 is, for example, 1.0 mm or more. Therefore, the gap between the electrostatic shield 45 and the coil 15 (second coil portion 15b) is increased. The options for the material of the electrostatic shield 45 are increased.

[0024] The rotor core 30 includes a first core portion 33 proximal to the stator core 14 with respect to the ring grooves 31a and 31b, a second core portion 34 proximal to the conductive shaft 18 with respect to the ring grooves 31a and 31b, and a third core portion 35 between the first core portion 33 and the second core portion 34. The first core portion 33, the second core portion 34, and the third core portion 35 define ring grooves 31a and 31b. The position of the third core portion 35 in the radial direction of the rotor core 30 corresponds to the positions of the ring grooves 31a and 31b in the radial direction of the rotor core 30. The height of the third core portion 35 (the length of the third core portion 35 in the axial direction of the conductive shaft 18) is smaller than the height of the first core portion 33 (the length of the first core portion 33 in the axial direction of the conductive shaft 18) and is smaller than the height of the second core portion 34 (the length of the second core portion 34 in the axial direction of the conductive shaft 18).

[0025] The first core portion 33 is located between the coil 15 and the electrostatic shields 40, 45 in the radial direction of the rotor core 30. Specifically, the first core portion 33 is located between the first coil portion 15a and the electrostatic shield 40 in the radial direction of the rotor core 30. The first core portion 33 is located between the second coil portion 15b and the electrostatic shield 45 in the radial direction of the rotor core 30.

[0026] The rotor core 30 is formed of a magnetic material. At least one of the first core portion 33, the second core portion 34, and the third core portion 35 is formed of an insulating material. In this embodiment, the first core portion 33, the second core portion 34, and the third core portion 35 are formed of a magnetic and insulating material containing a resin. That is, the entire rotor core 30 is formed of a magnetic and insulating material containing a resin. Specifically, the rotor core 30 (the first core portion 33, the second core portion 34, and the third core portion 35) may be formed of a magnetic and insulating material in which an insulating resin material such as nylon, elastomer, or polyphenylene sulfide (PPS) is mixed with a magnetic material such as ferrite, neodymium, or samarium-cobalt alloy. The rotor core 30 can be manufactured, for example, by integrally molding a mixture of an insulating resin material and a magnetic material with the conductive shaft 18.

[0027] The electrostatic shields 40, 45 are formed of a conductive material such as an aluminum alloy, copper, steel (e.g., carbon steel such as S45C) or alloy steel (e.g., stainless steel). The electrostatic shields 40, 45 may be formed of a magnetic and conductive metal material such as steel (e.g., carbon steel such as S45C) or alloy steel (e.g., stainless steel). The electrostatic shields 40, 45 may be formed of a non-magnetic and conductive metal material such as an aluminum alloy or copper.

[0028] The electrostatic shields 40 and 45 are fixed to the conductive case part (frame 11, bracket 12). The electrostatic shields 40 and 45 are electrically connected to the conductive case part (frame 11, bracket 12). Specifically, the electrostatic shield 40 is fixed to the conductive case part (frame 11). The electrostatic shield 40 extends from the conductive case part (frame 11) toward the rotor core 30 along the axial direction of the conductive shaft 18. The electrostatic shield 40 is electrically connected to the conductive case part (frame 11). The electrostatic shield 45 is fixed to the conductive case part (bracket 12). The electrostatic shield 45 extends from the conductive case part (bracket 12) toward the rotor core 30 along the axial direction of the conductive shaft 18. The electrostatic shield 45 is electrically connected to the conductive case part (bracket 12).

[0029] The electrostatic shields 40, 45 have, for example, a cylindrical shape. The electrostatic shields 40, 45 are disposed between the coil 15 and the conductive shaft 18. A portion of the electrostatic shields 40, 45 is located within the ring grooves 31a, 31b. In the radial direction of the rotor core 30, the electrostatic shields 40, 45 face at least a portion of the coil 15 via the first core portion 33. The electrostatic shields 40, 45 shield the conductive shaft 18 from at least a portion of the coil 15.

[0030] Specifically, the electrostatic shield 40 is disposed between the first coil portion 15a and the conductive shaft 18. A portion of the electrostatic shield 40 is located within the ring groove 31a. In the radial direction of the rotor core 30, the electrostatic shield 40 faces at least a portion of the first coil portion 15a via the first core portion 33. The electrostatic shield 40 shields the conductive shaft 18 from at least a portion of the first coil portion 15a.

[0031] The electrostatic shield 45 is disposed between the second coil portion 15b and the conductive shaft 18. A portion of the electrostatic shield 45 is within the ring groove 31b. In the radial direction of the rotor core 30, the electrostatic shield 45 faces at least a portion of the second coil portion 15b via the first core portion 33. The electrostatic shield 45 shields the conductive shaft 18 from at least a portion of the second coil portion 15b.

[0032] Referring to FIG. 2, in order to operate the motor 1, the motor 1 is connected to a power supply device 50. The power supply device 50 supplies AC power, such as three-phase AC power, to the motor 1. The power supply device 50 includes, for example, a power source 51, a smoothing capacitor 52, an inverter circuit 53, a positive electrode line 54, a negative electrode line 55, and a control circuit 60. The power source 51 is connected to the positive electrode line 54 and the negative electrode line 55. The power source 51 is, for example, a DC power source. The smoothing capacitor 52 is connected to the positive electrode line 54 and the negative electrode line 55. The smoothing capacitor 52 stabilizes the DC power between the positive electrode line 54 and the negative electrode line 55.

[0033] The inverter circuit 53 includes a positive input terminal 53a, a negative input terminal 53b, legs 56u, 56v, and 56w, a u-phase output terminal 53u, a v-phase output terminal 53v, and a w-phase output terminal 53w. The positive input terminal 53a is connected to a positive line 54. The negative input terminal 53b is connected to a negative line 55. The legs 56u, 56v, and 56w are connected to the positive input terminal 53a and the negative input terminal 53b, respectively. The legs 56u, 56v, and 56w each include an upper arm and a lower arm. The upper arm and the lower arm each include a semiconductor switching element 57 such as an insulated gate bipolar transistor (IGBT), and a free wheel diode 58 connected in reverse parallel to the semiconductor switching element 57.

[0034] When the semiconductor switching element 57 is an IGBT, the collector terminal of the IGBT of the upper arm is connected to the positive input terminal 53a, and the emitter terminal of the IGBT of the lower arm is connected to the negative input terminal 53b. The u-phase output terminal 53u is connected to the leg 56u. The v-phase output terminal 53v is connected to the leg 56v. The w-phase output terminal 53w is connected to the leg 56w. The u-phase coil 15u is connected to the u-phase output terminal 53u. The v-phase coil 15v is connected to the v-phase output terminal 53v. The w-phase coil 15w is connected to the w-phase output terminal 53w.

[0035] The control circuit 60 is connected to each gate terminal of the semiconductor switching elements 57. The inverter circuit 53 is controlled by the control circuit 60, for example, by a pulse width modulation (PWM) method. The inverter circuit 53 converts DC power input to the inverter circuit 53 from the power source 51 into three-phase AC power (u-phase AC power, v-phase AC power, and w-phase AC power). The inverter circuit 53 outputs the three-phase AC power to the coil 15. Specifically, the inverter circuit 53 outputs u-phase AC power to the u-phase coil 15u. The inverter circuit 53 outputs v-phase AC power to the v-phase coil 15v. The inverter circuit 53 outputs w-phase AC power to the w-phase coil 15w. By supplying the three-phase AC power to the coil 15, the rotor core 30 and the conductive shaft 18 to which the rotor core 30 is fixed rotate. In this manner, the motor 1 operates.

[0036] 1 and 2, the neutral point potential V n is the voltage of three-phase AC power (u-phase voltage V u , v-phase voltage V of v-phase AC power v , w-phase voltage V of w-phase AC power w ) The case 10 is connected to the earth 61. Therefore, the potential difference between the coil 15 and the case 10 when the motor 1 is in operation is the neutral point potential.

[0037] In the motor 1, the coil 15 and the conductive shaft 18 are capacitively coupled to each other. The conductive shaft 18 and the case 10 are capacitively coupled to each other. Between the neutral point potential and the earth 61, there are a first capacitor formed between the coil 15 and the conductive shaft 18 and a second capacitor formed between the conductive shaft 18 and the case 10, and the first capacitor and the second capacitor can be considered to be connected in series to each other. Depending on the capacitance between the coil 15 and the conductive shaft 18 and the capacitance between the conductive shaft 18 and the case 10, the potential difference between the coil 15 and the case 10 is divided into a potential difference between the coil 15 and the conductive shaft 18 and a potential difference between the conductive shaft 18 and the case 10.

[0038] The outer rings 22, 27 of the bearings 20, 25 are electrically connected to the conductive case parts (e.g., the frame 11, the bracket 12), and the inner rings 21, 26 of the bearings 20, 25 are electrically connected to the conductive shaft 18. Therefore, the potential difference between the outer rings 22, 27 and the inner rings 21, 26 is equal to the potential difference between the conductive shaft 18 and the case 10. When the motor 1 is in operation, when the shaft rotates at high speed, a lubricating film, which is a part of the insulating lubricant 24, 29, is formed between the outer rings 22, 27 and the multiple rolling elements 23, 28, and between the multiple rolling elements 23, 28 and the inner rings 21, 26. The outer rings 22, 27 and the inner rings 21, 26 are electrically insulated by the insulating lubricant 24, 29.

[0039] When the potential difference between the conductive shaft 18 and the case 10 exceeds the dielectric breakdown voltage of the insulating lubricant 24, 29, a high-frequency current called an axial current flows between the outer ring 22, 27 and the inner ring 21, 26. When an axial current flows between the outer ring 22, 27 and the inner ring 21, 26, electrical corrosion occurs in at least one of the inner ring 21, 26, the outer ring 22, 27, or the rolling elements 23, 28. The life of the bearings 20, 25 is shortened. The life of the motor 1 is shortened.

[0040] In this embodiment, at least one of the first core portion 33, the second core portion 34, and the third core portion 35 is formed of an insulating material. The electrostatic shields 40, 45 are disposed between the coil 15 and the conductive shaft 18. The electrostatic shields 40, 45 are electrically connected to the case 10. Therefore, the electrostatic shields 40, 45 can shield the conductive shaft 18 from the coil 15. The electrostatic capacitance between the coil 15 and the conductive shaft 18 is reduced. The potential difference between the coil 15 and the conductive shaft 18 during the operation of the motor 1 is increased, and the potential difference between the conductive shaft 18 and the case 10 during the operation of the motor 1 is reduced. The potential difference between the conductive shaft 18 and the case 10 during the operation of the motor 1 is smaller than the breakdown voltage of the insulating lubricants 24, 29. The breakdown of the insulating lubricants 24, 29 during the operation of the motor 1 is prevented. The flow of an axial current between the outer rings 22, 27 and the inner rings 21, 26 is prevented. It is possible to prevent electrical corrosion from occurring in the inner rings 21, 26, the outer rings 22, 27, and the plurality of rolling elements 23, 28. It is possible to extend the life of the bearings 20, 25. It is possible to extend the life of the motor 1.

[0041] In a modification of this embodiment, one of the frame 11 and the bracket 12 may be formed of a conductive material, and the other of the frame 11 and the bracket 12 may be formed of an insulating material (e.g., an insulating resin material such as polybutylene terephthalate (PBT)). That is, one of the frame 11 and the bracket 12 is a conductive case part, but the other of the frame 11 and the bracket 12 does not have to be a conductive case part.

[0042] The effects of the motor 1 of this embodiment will be described. The motor 1 of this embodiment includes a case 10, a conductive shaft 18, a bearing (bearing 20, bearing 25, or both bearing 20 and bearing 25), a rotor core 30, a stator core 14, a coil 15, and an electrostatic shield (for example, electrostatic shield 40, electrostatic shield 45, or both electrostatic shield 40 and electrostatic shield 45). The case 10 includes a conductive case portion (for example, a frame 11, a bracket 12, or both frame 11 and bracket 12). The conductive shaft 18 is spaced apart from the case 10. The bearings 20 and 25 support the conductive shaft 18 rotatably relative to the conductive case portion. The rotor core 30 is fixed to the conductive shaft 18. The stator core 14 is disposed facing the rotor core 30. The coil 15 is wound around the stator core 14. The electrostatic shield is fixed to the conductive case portion. The case 10 houses the bearing, the rotor core 30, the stator core 14, the coil 15, and the electrostatic shield. The bearing includes a conductive outer ring (e.g., the outer ring 22, the outer ring 27, or both the outer ring 22 and the outer ring 27), a conductive inner ring (e.g., the inner ring 21, the inner ring 26, or both the inner ring 21 and the inner ring 26), a plurality of rolling elements (e.g., a plurality of rolling elements 23, a plurality of rolling elements 28, or both the plurality of rolling elements 23 and the plurality of rolling elements 28), and an insulating lubricant (an insulating lubricant 24, an insulating lubricant 29, or both the insulating lubricant 24 and the insulating lubricant 29). The conductive outer ring is fixed to the conductive case part. The conductive inner ring is fixed to the conductive shaft 18. The plurality of rolling elements are arranged between the conductive outer ring and the conductive inner ring so as to be freely rollable. The insulating lubricant is filled in the bearing space between the conductive outer ring and the conductive inner ring. A ring groove (ring groove 31a, ring groove 31b, or both ring groove 31a and ring groove 31b) is formed in the rotor core 30. The rotor core 30 includes a first core portion 33 proximal to the stator core 14 with respect to the ring groove, a second core portion 34 proximal to the conductive shaft 18 with respect to the ring groove (ring groove 31a, ring groove 31b, or both ring groove 31a and ring groove 31b), and a third core portion 35 between the first core portion 33 and the second core portion 34.At least one of the first core portion 33, the second core portion 34, or the third core portion 35 is formed of an insulating material. The electrostatic shield is disposed between the coil 15 and the conductive shaft 18 and is electrically connected to the conductive case portion. A portion of the electrostatic shield is within the ring groove.

[0043] The electrostatic shield (e.g., the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) can shield the conductive shaft 18 from the coil 15. The electrostatic capacitance between the coil 15 and the conductive shaft 18 is reduced. The potential difference between the coil 15 and the conductive shaft 18 during operation of the motor 1 is increased, and the potential difference between the conductive shaft 18 and the case 10 during operation of the motor 1 is reduced. The insulation breakdown of the insulating lubricant (the insulating lubricant 24, the insulating lubricant 29, or both the insulating lubricant 24 and the insulating lubricant 29) during operation of the motor 1 is prevented. The axial current is prevented from flowing between the outer ring (e.g., the outer ring 22, the outer ring 27, or both the outer ring 22 and the outer ring 27) and the inner ring (e.g., the inner ring 21, the inner ring 26, or both the inner ring 21 and the inner ring 26). The occurrence of electrical corrosion in the inner ring, the outer ring, and the plurality of rolling elements (for example, the plurality of rolling elements 23, the plurality of rolling elements 28, or both the plurality of rolling elements 23 and the plurality of rolling elements 28) can be prevented.

[0044] In addition, a part of the electrostatic shield (e.g., the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) is in the ring groove (the ring groove 31a, the ring groove 31b, or both the ring groove 31a and the ring groove 31b), so that the distance between the electrostatic shield and the coil 15 can be increased. As the electrostatic shield, not only a nonmagnetic material but also a magnetic material can be selected. This can expand the selection of materials for the electrostatic shield.

[0045] In the motor 1 of the present embodiment, the electrostatic shield (for example, the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) is made of a magnetic and conductive metal material, which allows for a wider range of options for the material of the electrostatic shield.

[0046] In the motor 1 of the present embodiment, the electrostatic shield (for example, the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) is made of a non-magnetic and conductive metal material.

[0047] Therefore, it is possible to prevent the electrostatic shield from adversely affecting the distribution of the magnetic field generated by coil 15. It is possible to prevent a decrease in the electromagnetic force acting on rotor core 30. It is also possible to prevent eddy currents from being generated in the electrostatic shield due to the magnetic field generated by coil 15. It is possible to avoid the occurrence of eddy current loss in motor 1. In this way, it is possible to prevent a decrease in the efficiency of motor 1.

[0048] In the motor 1 of this embodiment, the width of the ring groove (the ring groove 31a, the ring groove 31b, or both the ring groove 31a and the ring groove 31b) is greater than the first gap (g) between the stator core 14 and the rotor core 30.

[0049] Therefore, the dimensional accuracy and alignment accuracy of the electrostatic shields (e.g., the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) may be relaxed. The productivity of the motor 1 is improved, and the cost of the motor 1 can be reduced.

[0050] In the motor 1 of this embodiment, the width of the ring groove (the ring groove 31a, the ring groove 31b, or both the ring groove 31a and the ring groove 31b) is 1.0 mm or more.

[0051] Therefore, the dimensional accuracy and alignment accuracy of the electrostatic shields (e.g., the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) may be relaxed. The productivity of the motor 1 is improved, and the cost of the motor 1 can be reduced.

[0052] In the motor 1 of the present embodiment, the first core portion 33, the second core portion 34, and the third core portion 35 are made of a magnetic and insulating material that contains resin.

[0053] The first core portion 33, the second core portion 34, and the third core portion 35 are all formed of a magnetic and insulating material containing resin. Therefore, the first core portion 33, the second core portion 34, and the third core portion 35 can be formed together. This allows the cost of the motor 1 to be reduced.

[0054] Embodiment 2 A motor 1b according to the second embodiment will be described with reference to Fig. 3. The motor 1b according to the present embodiment has a similar configuration to the motor 1 according to the first embodiment and achieves the same effects, but differs mainly in the following respects.

[0055] In the motor 1b, through holes 41, 46 are formed in the electrostatic shields 40, 45. The axial direction of the through holes 41, 46 may be the radial direction of the rotor core 30. The through holes 41, 46 are formed in the electrostatic shields 40, 45. The axial direction of the through holes 41, 46 may be the radial direction of the rotor core 30. The coolant (e.g., air, water, oil, etc.) in the case 10 can pass through the through holes 41, 46. The through holes 41, 46 allow the coolant to flow smoothly inside the case 10. The coil 15, the rotor core 30, and the stator core 14 can be efficiently cooled by the coolant.

[0056] In addition to the effects of motor 1 of the first embodiment, motor 1b of the present embodiment has the following effects.

[0057] In the motor 1b of this embodiment, a through hole (e.g., through hole 41, through hole 46, or both through hole 41 and through hole 46) is formed in the electrostatic shield (e.g., electrostatic shield 40, electrostatic shield 45, or both electrostatic shield 40 and electrostatic shield 45).

[0058] Therefore, the coolant (e.g., air, water, oil, etc.) in the case 10 can pass through the through holes (e.g., the through holes 41, the through holes 46, or both the through holes 41 and the through holes 46). The coil 15, the rotor core 30, and the stator core 14 can be efficiently cooled by the coolant. Deterioration of the coil 15 and changes in the magnetic properties of the stator core 14 and the rotor core 30 caused by heat generated in the coil 15 can be suppressed. A decrease in the performance of the motor 1b can be prevented, and the life of the motor 1b can be extended.

[0059] Embodiment 3 A motor 1c according to a third embodiment will be described with reference to Fig. 4. The motor 1c according to the present embodiment has a similar configuration to the motor 1 according to the first embodiment, but differs mainly in the following respects.

[0060] In the motor 1c, the height H of the electrostatic shield 40 from the conductive case part (frame 11) is 1 is the distance G between the conductive case part (frame 11) and the stator core 14. 1 Equal to or in the interval G 1 Therefore, the electrostatic shield 40 can shield the conductive shaft 18 from the entire first coil portion 15a. 2 is the distance G between the conductive case part (bracket 12) and the stator core 14. 2 Equal to or in the interval G 2 Therefore, electrostatic shield 45 can shield conductive shaft 18 from the entire second coil portion 15b.

[0061] The motor 1c of the present embodiment provides the following advantages in addition to the advantages of the motor 1 of the first embodiment.

[0062] In the motor 1c of the present embodiment, the stator core 14 is made of a magnetic and insulating material. The height (height H 1 , height H 2 ) is the second gap (gap G) between the conductive case portion and the stator core 14 1 , interval G 2 )That's all.

[0063] Therefore, the electrostatic shield (electrostatic shield 40, electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45) can shield the conductive shaft 18 from the entire portion (first core portion 33, second core portion 34) of the coil 15 exposed from the stator core 14. The electrostatic capacitance between the coil 15 and the conductive shaft 18 is further reduced. The potential difference between the conductive shaft 18 and the case 10 during operation of the motor 1c is further reduced. The flow of axial current between the outer ring (the outer ring 22, the outer ring 27, or both the outer ring 22 and the outer ring 27) and the inner ring (the inner ring 21, the inner ring 26, or both the inner ring 21 and the inner ring 26) is further prevented. The occurrence of electrical corrosion in the inner ring, the outer ring, and the multiple rolling elements (the multiple rolling elements 23, the multiple rolling elements 28, or both the multiple rolling elements 23 and the multiple rolling elements 28) can be further prevented.

[0064] Embodiment 4 A motor 1d according to the fourth embodiment will be described with reference to Fig. 5. The motor 1d according to the present embodiment has a similar configuration to the motor 1c according to the third embodiment, but differs mainly in the following respects.

[0065] In the motor 1d, the distance r between the coil 15 (the first coil portion 15a) and the electrostatic shield 40 is 1 is the spacing R between the electrostatic shield 40 and the conductive shaft 18 1 Greater than r 1 For example, the interval R 1 The interval R 1The interval R 1 2.0 times or more, so that the capacitance between coil 15 and conductive shaft 18 is further reduced.

[0066] The distance r between the coil 15 (the second coil portion 15b) and the electrostatic shield 45 2 is the distance R between the electrostatic shield 45 and the conductive shaft 18 2 Greater than r 2 For example, the interval R 2 The interval R 2 The interval R 2 2.0 times or more, so that the capacitance between coil 15 and conductive shaft 18 is further reduced.

[0067] In a modification of this embodiment, the interval r between the coil 15 (first coil portion 15a) and the electrostatic shield 40 in the motor of another embodiment (for example, the motor 1 of the first embodiment) is 1 is the distance R between the electrostatic shield 40 and the conductive shaft 18. 1 The spacing r between the coil 15 (second coil portion 15b) and the electrostatic shield 45 may be larger than 1. 2 is the distance R between the electrostatic shield 45 and the conductive shaft 18. 2 It may be made larger.

[0068] The motor 1d of this embodiment achieves the following effects in addition to the effects of the motor 1c of the third embodiment.

[0069] In the motor 1d of the present embodiment, the third interval (interval r 1 , interval r 2 or interval r 1 and interval r 2 ) is the fourth spacing (spacing R 1 , interval R 2 or interval R 1and interval R 2 is greater than both.

[0070] Therefore, the electrostatic capacitance between the coil 15 and the conductive shaft 18 is further reduced. The potential difference between the conductive shaft 18 and the case 10 during operation of the motor 1d is further reduced. The flow of axial current between the outer ring (the outer ring 22, the outer ring 27, or both the outer ring 22 and the outer ring 27) and the inner ring (the inner ring 21, the inner ring 26, or both the inner ring 21 and the inner ring 26) is further prevented. The occurrence of electrical corrosion in the inner ring, the outer ring, and the multiple rolling elements (the multiple rolling elements 23, the multiple rolling elements 28, or both the multiple rolling elements 23 and the multiple rolling elements 28) can be further prevented.

[0071] Embodiment 5. A motor 1e according to a fifth embodiment will be described with reference to Fig. 6. The motor 1e according to the present embodiment has a similar configuration to the motor 1 according to the first embodiment, but differs mainly in the following respects.

[0072] In the motor 1e, the bearing 20 is fixed to the conductive case portion (frame 11) via the electrostatic shield 40. Specifically, the outer ring 22 is fixed to the electrostatic shield 40. The support wall 11b (see FIG. 1) is omitted.

[0073] The bearing 25 is fixed to the conductive case portion (bracket 12) via the electrostatic shield 45. Specifically, the outer ring 27 is fixed to the electrostatic shield 45. The support wall 12b (see FIG. 1) is omitted.

[0074] The motor 1e of the present embodiment provides the following advantages in addition to the advantages of the motor 1 of the first embodiment.

[0075] In the motor 1e of this embodiment, the bearings (the bearing 20, the bearing 25, or both the bearing 20 and the bearing 25) are fixed to the conductive case portion (the frame 11, the bracket 12, or both the frame 11 and the bracket 12) via an electrostatic shield (the electrostatic shield 40, the electrostatic shield 45, or both the electrostatic shield 40 and the electrostatic shield 45). Therefore, the motor 1e can be made compact.

[0076] Embodiment 6 A motor 1f of the sixth embodiment will be described with reference to Fig. 7. The motor 1f of the present embodiment has a similar configuration to the motor 1 of the first embodiment, but differs mainly in the following respects.

[0077] In the motor 1f, the second core portion 34 is formed of a magnetic and conductive metal material such as steel (e.g., carbon steel such as S45C) or alloy steel (e.g., stainless steel). The third core portion 35 is formed of a magnetic and insulating material containing resin. The third core portion 35 may be formed of a magnetic and insulating material that is a mixture of an insulating resin material such as nylon, elastomer, or polyphenylene sulfide (PPS) and a magnetic material such as ferrite, neodymium, or samarium-cobalt alloy.

[0078] In the present embodiment, the rotor core 30 can be formed, for example, by the following steps. The second core portion 34 is press-fitted onto the conductive shaft 18. Then, the shaft and the second core portion 34 are placed in a mold (not shown). A mixture of an insulating resin material and a magnetic material is injected into the mold. The mixture of the insulating resin material and the magnetic material is integrally molded with the second core portion 34 to form the first core portion 33 and the third core portion 35.

[0079] The motor 1f of this embodiment has the following advantages in addition to the advantages of the motor 1 of the first embodiment.

[0080] In the motor 1f of the present embodiment, the second core portion 34 is made of a magnetic and conductive metal material, and the first core portion 33 and the third core portion 35 are made of a magnetic and insulating material containing resin.

[0081] The second core portion 34 can protect the conductive shaft 18 from heat shock that occurs when the first core portion 33 and the third core portion 35, which are made of a magnetic and insulating material containing resin, are integrally molded with the second core portion 34. This can prevent the conductive shaft 18 from being damaged during use of the motor 1f. This can extend the life of the motor 1f.

[0082] Embodiment 7 A motor 1g according to the seventh embodiment will be described with reference to Fig. 8. Motor 1g according to the present embodiment has a similar configuration to motor 1 according to the first embodiment, but differs mainly in the following respects.

[0083] In the motor 1g, the second core portion 34 is formed of a magnetic and insulating material containing resin. The second core portion 34 may be formed of a magnetic and insulating material that is a mixture of an insulating resin material such as nylon, elastomer, or polyphenylene sulfide (PPS) and a magnetic material such as ferrite, neodymium, or samarium-cobalt alloy. The third core portion 35 is formed of a magnetic and conductive metal material such as steel (e.g., carbon steel such as S45C) or alloy steel (e.g., stainless steel).

[0084] The height of the third core portion 35 (the length of the third core portion 35 in the axial direction of the conductive shaft 18) is smaller than the height of the first core portion 33 (the length of the first core portion 33 in the axial direction of the conductive shaft 18) and is smaller than the height of the second core portion 34 (the length of the second core portion 34 in the axial direction of the conductive shaft 18). Therefore, the third core portion 35 is more likely to be damaged than the first core portion 33 and the second core portion 34 by the centrifugal force acting on the rotor core 30 during operation of the motor 1g. However, the first core portion 33 and the second core portion 34 are formed of a magnetic and insulating material containing resin, whereas the third core portion 35 is formed of a magnetic and conductive metal material. The third core portion 35 is formed of a material having a higher mechanical strength than the first core portion 33 and the second core portion 34. Therefore, the third core portion 35 can be prevented from being damaged by the centrifugal force acting on the rotor core 30 during operation of the motor 1g.

[0085] In this embodiment, the rotor core 30 can be formed, for example, by the following process. The conductive shaft 18 and the third core portion 35 are placed in a mold (not shown). Then, a mixture of an insulating resin material and a magnetic material is injected into the mold. The mixture of the insulating resin material and the magnetic material is integrally molded with the shaft and the third core portion 35 to form the first core portion 33 and the second core portion 34.

[0086] In addition to the effects of the motor 1 of the first embodiment, the motor 1g of the present embodiment has the following effects.

[0087] In the motor 1g of the present embodiment, the first core portion 33 and the second core portion 34 are made of a magnetic and insulating material containing resin, and the third core portion 35 is made of a magnetic and conductive metal material.

[0088] This can prevent damage to the third core portion 35. The life of the motor 1g can be extended.

[0089] Embodiment 8 A motor 1h according to an eighth embodiment will be described with reference to Fig. 9. The motor 1h according to the present embodiment has a similar configuration to the motor 1 according to the first embodiment, but differs mainly in the following respects.

[0090] In the motor 1h, the second core portion 34 and the third core portion 35 are formed of a magnetic and conductive metal material such as steel (e.g., carbon steel such as S45C), alloy steel (e.g., stainless steel), or electromagnetic steel plate. As in the seventh embodiment, in the present embodiment, the third core portion 35 is also formed of a magnetic and conductive metal material. Therefore, the third core portion 35 can be prevented from being damaged by the centrifugal force acting on the rotor core 30 during operation of the motor 1h.

[0091] In this embodiment, the rotor core 30 can be formed, for example, by the following steps. The second core portion 34 and the third core portion 35 are press-fitted into the conductive shaft 18. Then, the shaft, the second core portion 34, and the third core portion 35 are placed in a mold (not shown). A mixture of an insulating resin material and a magnetic material is injected into the mold. The mixture of the insulating resin material and the magnetic material is integrally molded with the third core portion 35 to form the first core portion 33.

[0092] The motor 1h of this embodiment has the following advantages in addition to the advantages of the motor 1 of the first embodiment.

[0093] In the motor 1h of the present embodiment, the first core portion 33 is made of a magnetic and insulating material containing resin, and the second core portion 34 and the third core portion 35 are made of a magnetic and conductive metal material.

[0094] Therefore, the third core portion 35 can be prevented from being damaged. The life of the motor 1h can be extended. In addition, the second core portion 34 and the third core portion 35 can protect the conductive shaft 18 from heat shock that occurs when the first core portion 33, which is made of a magnetic and insulating material containing resin, is integrally molded with the third core portion 35. The conductive shaft 18 can be prevented from being damaged during use of the motor 1h. The life of the motor 1h can be extended.

[0095] The first to eighth embodiments and their modifications disclosed herein should be considered as illustrative and not restrictive in all respects. At least two of the first to eighth embodiments and their modifications disclosed herein may be combined unless there is a contradiction. The scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0096] 1,1b,1c,1d,1e,1f,1g,1h motor, 10 case, 11 frame, 11a hole, 11b,12b support wall, 12 bracket, 14 stator core, 15 coil, 15u u-phase coil, 15v v-phase coil, 15w w-phase coil, 15a first coil portion, 15b second coil portion, 15n neutral point, 18 conductive shaft, 20,25 bearing, 21,26 inner ring, 22,27 outer ring, 23,28 rolling element, 24,29 insulating lubricant, 30 rotor core, 30a first main surface, 30b second main surface, 30c outer peripheral side surface, 31a,31b ring groove, 33 first core portion, 34 second core portion, 35 third core portion, 40,45 electrostatic shield, 41,46 Through hole, 50 power supply device, 51 power supply, 52 smoothing capacitor, 53 inverter circuit, 53a positive input terminal, 53b negative input terminal, 53u u-phase output terminal, 53v v-phase output terminal, 53w w-phase output terminal, 54 positive line, 55 negative line, 56u, 56v, 56w legs, 57 semiconductor switching element, 58 freewheel diode, 60 control circuit, 61 earth.

Claims

1. a case including a conductive case portion; a conductive shaft spaced from the case; a bearing that rotatably supports the conductive shaft relative to the conductive case portion; A rotor core fixed to the conductive shaft; a stator core disposed opposite the rotor core; A coil wound around the stator core; an electrostatic shield secured to the conductive case portion; the case accommodates the bearing, the rotor core, the stator core, the coil, and the electrostatic shield; the bearing includes a conductive outer ring, a conductive inner ring, a plurality of rolling elements, and an insulating lubricant, the conductive outer ring is fixed to the conductive case portion, the conductive inner ring is fixed to the conductive shaft, the plurality of rolling elements are arranged to roll freely between the conductive outer ring and the conductive inner ring, the insulating lubricant is sealed in a bearing space between the conductive outer ring and the conductive inner ring, and a lubricating film, which is a part of the insulating lubricant, is formed between the conductive outer ring and the plurality of rolling elements, and between the plurality of rolling elements and the conductive inner ring, A ring groove is formed in the rotor core, the rotor core includes a first core portion proximate to the stator core with respect to the ring groove, a second core portion proximate to the conductive shaft with respect to the ring groove, and a third core portion between the first core portion and the second core portion; At least one of the first core portion, the second core portion, and the third core portion is made of an insulating material, the electrostatic shield is disposed between the coil and the conductive shaft and is electrically connected to the conductive case portion; A portion of the electrostatic shield is within the ring groove.

2. The motor of claim 1 , wherein the electrostatic shield is formed from a magnetic and conductive metallic material.

3. The motor of claim 1 , wherein the electrostatic shield is formed of a non-magnetic, electrically conductive metallic material.

4. The motor according to claim 1 , wherein a width of the ring groove is greater than a first distance between the stator core and the rotor core.

5. The motor of claim 4 , wherein the width of the ring groove is greater than or equal to 1.0 mm.

6. The motor according to claim 1 , wherein the electrostatic shield is formed with a through hole.

7. The stator core is made of a magnetic and insulating material. The motor of claim 1 , wherein a height of the electrostatic shield from the conductive case portion is greater than or equal to a second spacing between the conductive case portion and the stator core.

8. The motor of claim 1 , wherein a third spacing between the coil and the electrostatic shield is greater than a fourth spacing between the electrostatic shield and the conductive shaft.

9. The motor according to claim 1 , wherein the bearing is fixed to the conductive case portion via the electrostatic shield.

10. The motor according to claim 1 , wherein the first core portion, the second core portion, and the third core portion are made of a magnetic and insulating material containing a resin.

11. The second core portion is formed of a magnetic and conductive metal material, The motor according to claim 1 , wherein the first core portion and the third core portion are made of a magnetic and insulating material containing a resin.

12. the first core portion and the second core portion are formed of a magnetic and insulating material containing a resin, The motor according to claim 1 , wherein the third core portion is formed of a magnetic and conductive metal material.

13. The first core portion is formed of a magnetic and insulating material containing a resin, The motor according to claim 1 , wherein the second core portion and the third core portion are formed of a magnetic and conductive metal material.

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