Rotary electric machine

Abstract

The present invention provides a rotary electric machine comprising: a motor mounted to an object to be driven and having a rotary shaft, a rotor fixed to the rotary shaft, and a stator disposed outside the rotor; and a motor case storing the motor. The motor case has a cylindrical portion which extends along the axial direction of the rotary shaft and to which the stator is fixed, a bottom portion covering one end of the cylindrical portion in the axial direction, and a flange protruding from an outer circumference surface of the bottom portion. The flange has a mounting surface which abuts against a housing of the object to be driven and which is fixed to the housing. A ratio of the thickness of the bottom portion to the thickness of the flange portion is 1 or greater.

Description

Rotating electric machines

[0001] The present disclosure relates to a rotating electric machine.

[0002] The rotating electric machine is attached to a driven object and transmits a driving force generated by a motor of the rotating electric machine to the driven object. Patent Document 1 discloses an electric power steering device that applies the driving force generated by the motor to a steering mechanism of a vehicle as a steering assist force. This electric power steering device has a gear mechanism as a driven object that transmits the driving force of the motor to the steering mechanism, and a gear housing that houses the gear mechanism. A motor case that houses the motor is fixed to the gear housing.

[0003] Patent No. 4926407

[0004] In Patent Document 1, a metal plate for vibration damping is provided between the motor case and the gear housing of the rotating electric machine to suppress transmission of vibrations of the rotating electric machine to the gear mechanism, which increases the number of parts and the labor required to assemble the rotating electric machine to the driven object.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a rotating electric machine that can suppress the transmission of vibrations of the rotating electric machine to the driven object while minimizing an increase in the number of parts.

[0006] The rotating electric machine of the present disclosure is a rotating electric machine attached to a driven object, and comprises a motor having a rotating shaft, a rotor fixed to the rotating shaft, and a stator arranged outside the rotor, and a motor case that houses the motor, wherein the motor case extends along the axial direction of the rotating shaft and has a cylindrical portion to which the stator is fixed, a bottom portion that covers one end of the cylindrical portion in the axial direction, and a flange portion that protrudes from the outer peripheral surface of the bottom portion, the flange portion having a mounting surface that abuts against a housing of the driven object and is fixed to the housing, and the ratio of the thickness of the bottom portion to the thickness of the flange portion is 1 or greater.

[0007] According to the present disclosure, it is possible to provide a rotating electric machine that can suppress transmission of vibrations of the rotating electric machine to a driven object while suppressing an increase in the number of parts.

[0008] 1 is a schematic cross-sectional view of a rotating electric machine according to a first embodiment. FIG. 2 is a graph showing the relationship between the vibration value of a driven object and the perpendicular index of the mounting surface after the motor case is assembled to the housing of the driven object. FIG. 3 is a graph showing the relationship between the perpendicular index of the mounting surface after the motor case is assembled to the housing of the driven object and the ratio of the thickness of the bottom portion to the thickness of the flange portion. FIG. 4 is a cross-sectional view showing a main part of a rotating electric machine according to a second embodiment. FIG. 5 is a cross-sectional view showing a main part of a rotating electric machine according to a third embodiment. FIG. 6 is a bottom view of a main part of a rotating electric machine according to a modification of the third embodiment. FIG. 7 is a schematic cross-sectional view of a rotating electric machine according to a fourth embodiment. FIG. 8 is a graph showing values ​​of the fractional pitch winding factor, the distributed winding factor, and the winding factor in a permanent magnet synchronous motor with 8 poles and 9 slots, 10 poles and 9 slots, 10 poles and 12 slots, and 14 poles and 12 slots. FIG. 9 is a schematic cross-sectional view of a rotating electric machine according to a fifth embodiment. FIG. 10 is a perspective view of an electric power steering device according to a sixth embodiment. FIG. 11 is a schematic cross-sectional view of a rotating electric machine according to a modification of the first embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present disclosure.

[0010] First Embodiment. FIG. 1 is a schematic cross-sectional view of a rotating electric machine 1. The rotating electric machine 1 includes a motor 10, a motor case 21, and an upper housing 27. The motor 10 includes a rotating shaft 11, a stator 12, and a rotor 13. The rotating electric machine 1 is attached to a driven object 100 and transmits a driving force generated by the motor 10 of the rotating electric machine 1 to the driven object 100. In the following description, the direction in which the central axis O of the rotating shaft 11 extends may be referred to as the axial direction. The rotating electric machine 1 and the driven object 100 are aligned in the axial direction. In addition, in the axial direction, the side on which the rotating electric machine 1 is located may be referred to as the upper side, and the side on which the driven object 100 is located may be referred to as the lower side or output side. The view from the axial direction may be referred to as a plan view. In the plan view, the direction intersecting the central axis O may be referred to as the radial direction, and the direction circumferential around the central axis O may be referred to as the circumferential direction.

[0011] The lower end of the rotating shaft 11 is used as an output end 11a. A boss 15 connected to the driven object 100 is attached to the output end 11a. The output of the motor 10 is transmitted to the driven object 100 via the output end 11a. When using the rotating electric machine 1, the axial direction of the rotating shaft 11 does not have to coincide with the vertical direction.

[0012] The stator 12 is disposed radially outward of the rotor 13 with a gap therebetween. The stator 12 has a stator core 12a and a coil 12b formed by winding a winding around the stator core 12a via an insulator 12c. The stator core 12a is formed, for example, by stacking a plurality of electromagnetic steel plates in the axial direction. The outer periphery of the stator core 12a is formed in a circular shape. The stator core 12a is fixed to the motor case 21.

[0013] The rotor 13 is fixed to the rotating shaft 11. The rotor 13 rotates by utilizing magnetic flux generated from the stator core 12a when current is applied to the coil 12b. The rotating shaft 11, the stator 12, and the rotor 13 are arranged coaxially.

[0014] The motor case 21 houses the motor 10. The motor case 21 is fixed to a housing 101 of the driven object 100. The motor case 21 is made of metal. A specific material for the motor case 21 is, for example, an aluminum-based alloy. The motor case 21 is produced, for example, by cutting a molded body obtained by die-casting or the like from an aluminum-based alloy.

[0015] The motor case 21 has a cylindrical portion 22, a bottom portion 23, a plurality of flange portions 24, and a positioning portion 25. The cylindrical portion 22, the bottom portion 23, the flange portions 24, and the positioning portion 25 are integrally molded.

[0016] The cylindrical portion 22 extends along the axial direction. The stator core 12a of the stator 12 is fixed in the cylindrical portion 22 by press fitting, shrink fitting, or the like.

[0017] The bottom portion 23 is disk-shaped. The bottom portion 23 covers the lower end of the cylindrical portion 22. A bearing fixing portion 23a is provided in the center of the bottom portion 23 in a plan view. The bearing fixing portion 23a is provided so as to protrude upward from the upper surface of the bottom portion 23. A through hole is formed in the bearing fixing portion 23a, through which the rotating shaft 11 passes. The first bearing 16 is attached to the through hole of the bearing fixing portion 23a.

[0018] The flange portions 24 are provided so as to protrude radially outward from the outer peripheral surface of the bottom portion 23. In the present embodiment, the number of flange portions 24 is two. The number of flange portions 24 may be three or more. The flange portions 24 are formed with bolt holes 24a through which the bolts 103 are inserted.

[0019] The positioning portion 25 is cylindrical. The positioning portion 25 is provided so as to protrude downward from the lower surface of the bottom portion 23. The positioning portion 25 is inserted into an opening 101a formed in the upper part of the housing 101 of the driven object 100. The positioning portion 25 positions the motor case 21 with respect to the housing 101.

[0020] The flange portion 24 and the portion of the bottom portion 23 located outside the positioning portion 25 form the mounting portion 21a of the motor case 21. The mounting portion 21a is attached to the housing 101. The height of the lower surface of the portion of the bottom portion 23 located outside the positioning portion 25 is equal to the height of the lower surface of the flange portion 24. In other words, the lower surface of the portion of the bottom portion 23 located outside the positioning portion 25 and the lower surface of the flange portion 24 are flush with each other and form the lower surface of the mounting portion 21a. The lower surface of the mounting portion 21a is referred to as the mounting surface 21b. The mounting surface 21b abuts against the upper surface of the housing 101 and is fixed to the housing 101.

[0021] As shown in Figure 1, the thickness of the bottom portion 23 (i.e., the length of the bottom portion 23 in the axial direction) is T1, and the thickness of the flange portion 24 (i.e., the length of the flange portion 24 in the axial direction) is T2. The ratio of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 is R. That is, R = T1 / T2. The ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 is 1 or greater. It is more preferable that the ratio R is greater than 1, and even more preferably 2 or greater.

[0022] The upper housing 27 is disk-shaped. The upper housing 27 is provided so as to close the opening at the upper end of the cylindrical portion 22. The upper housing 27 is fitted into the upper end of the cylindrical portion 22. A through-hole through which the rotary shaft 11 passes is formed in the center of the upper housing 27 in a plan view. The second bearing 17 is attached to the through-hole of the upper housing 27.

[0023] The first bearing 16 rotatably supports the output end 11 a of the rotating shaft 11. The second bearing 17 rotatably supports the end 11 b (the upper end in this embodiment) of the rotating shaft 11 opposite the output end 11 a. Therefore, the rotor 13 fixed to the rotating shaft 11 is also rotatable radially inside the stator 12.

[0024] The following describes how to assemble the motor case 21 to the housing 101. The positioning portion 25 is inserted into the opening 101a of the housing 101, and the mounting surface 21b is brought into contact with the upper surface of the housing 101. In this state, the bolts 103 are inserted into the bolt holes 24a of the flange portion 24 and fastened to the housing 101, thereby attaching the motor case 21 to the housing 101.

[0025] Here, due to manufacturing errors in the motor case 21 or deformation of the motor case 21 during manufacturing of the rotating electric machine 1, the flange portion 24 may be deformed, causing the mounting surface 21b to curve. For example, when the stator core 12a is fixed into the cylindrical portion 22 by press-fitting or shrink-fitting, the load applied to the cylindrical portion 22 may cause the cylindrical portion 22 to deform and bulge radially outward. As the cylindrical portion 22 deforms, the flange portion 24 may bend downward as it moves radially outward, causing the mounting surface 21b to bend downward as it moves radially outward. When the mounting surface 21b curves, the contact area between the mounting surface 21b and the upper surface of the housing 101 decreases, creating a gap between the mounting surface 21b and the upper surface of the housing 101. This may increase the vibration transmitted from the rotating electric machine 1 to the driven object 100.

[0026] By setting the ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 to be equal to or greater than 1, it is possible to suppress transmission of vibrations of the rotating electric machine 1 to the driven object 100. The reason for this will be explained with reference to FIGS. 2 and 3.

[0027] FIG. 2 is a graph showing the relationship between the vibration value of the driven object 100 measured by actual measurement and the perpendicularity index of the mounting surface 21b after the motor case 21 is assembled to the housing 101 of the driven object 100 (hereinafter referred to as the perpendicularity index of the assembled mounting surface 21b), calculated using CAE analysis. The vertical axis represents the vibration value of the driven object 100. The larger the vibration value of the driven object 100, the greater the vibration transmitted from the rotating electric machine 1 to the driven object 100. The horizontal axis represents the perpendicularity index of the assembled mounting surface 21b. The perpendicularity index of the assembled mounting surface 21b is a value representing the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101, based on an imaginary plane perpendicular to the axial direction. More specifically, the perpendicularity index of the assembled mounting surface 21b is a value representing the magnitude of deviation of the mounting surface 21b from the imaginary plane. The larger the perpendicularity index of the mounting surface 21b after assembly, the more the mounting surface 21b after assembly curves downward as it moves radially outward compared to the imaginary plane. As shown in FIG. 2 , the smaller the perpendicularity index of the mounting surface 21b after assembly, the smaller the vibration value of the driven object 100. In other words, it can be seen that reducing the perpendicularity index of the mounting surface 21b after assembly can suppress transmission of vibrations from the rotating electric machine 1 to the driven object 100. When the perpendicularity index of the mounting surface 21b after assembly is small, the mounting surface 21b has a shape that follows an imaginary plane perpendicular to the axial direction. This increases the contact area between the mounting surface 21b and the upper surface of the housing 101, which is thought to result in suppression of transmission of vibrations from the rotating electric machine 1 to the driven object 100.

[0028] FIG. 3 is a graph showing the relationship between the squareness index of the mounting surface 21b after assembly and the ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24. The vertical axis represents the squareness index of the mounting surface 21b after assembly. The horizontal axis represents the ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24. As shown in FIG. 3 , when the ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 is 1 or greater, the squareness index of the mounting surface 21b after assembly is reduced significantly. When the ratio R is 1 or greater, the thickness T1 of the bottom portion 23 is larger or the thickness T2 of the flange portion 24 is smaller than when the ratio R is less than 1. Increasing the thickness T1 of the bottom portion 23 improves the rigidity of the bottom portion 23. The improved rigidity of the bottom portion 23 can suppress deformation of the flange portion 24 when the stator core 12a is fixed into the cylindrical portion 22 by press-fitting or shrink-fitting. Therefore, it is possible to suppress the curvature of the mounting surface 21b before assembly, and as a result, it is thought that the perpendicularity index of the mounting surface 21b after assembly can be reduced. Furthermore, when the thickness T2 of the flange portion 24 is reduced, the rigidity of the flange portion 24 is reduced. Because the rigidity of the flange portion 24 is reduced, even if the flange portion 24 is deformed before assembly, the fastening force used to fasten the bolts 103 to the housing 101 can deform the flange portion 24 so that it conforms to the upper surface of the housing 101. Therefore, it is possible to correct the curvature of the mounting surface 21b, and it is thought that the perpendicularity index of the mounting surface 21b after assembly can be reduced.

[0029] As described above, when the ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 is 1 or greater, the effect of reducing the perpendicular index of the mounting surface 21b after assembly is greater, thereby suppressing the transmission of vibrations of the rotating electric machine 1 to the driven object 100. Furthermore, when the ratio R is greater than 1, the effect of reducing the perpendicular index of the mounting surface 21b after assembly is greater, thereby more effectively suppressing the transmission of vibrations of the rotating electric machine 1 to the driven object 100. When the ratio R is 2 or greater, the effect of reducing the perpendicular index of the mounting surface 21b after assembly is even greater, thereby more effectively suppressing the transmission of vibrations of the rotating electric machine 1 to the driven object 100.

[0030] As described above, the rotating electric machine 1 according to this embodiment includes a motor 10 having a rotating shaft 11, a rotor 13 fixed to the rotating shaft 11, and a stator 12 disposed outside the rotor 13, and a motor case 21 that houses the motor 10. The motor case 21 extends axially and has a cylindrical portion 22 to which the stator 12 is fixed, a bottom portion 23 that covers one axial end of the cylindrical portion 22, and a flange portion 24 that protrudes from the outer peripheral surface of the bottom portion 23. The flange portion 24 has a mounting surface 21b that abuts against and is fixed to a housing 101 of a driven object 100. A ratio R of a thickness T1 of the bottom portion 23 to a thickness T2 of the flange portion 24 is 1 or greater.

[0031] According to this rotating electric machine 1, by setting the ratio R to 1 or greater, transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed. Specifically, when the ratio R is 1 or greater, the thickness T2 of the flange portion 24 is smaller or the thickness T1 of the bottom portion 23 is larger than when the ratio R is less than 1. Increasing the thickness T1 of the bottom portion 23 improves the rigidity of the bottom portion 23. Improving the rigidity of the bottom portion 23 can suppress deformation of the flange portion 24 during manufacturing of the rotating electric machine 1, for example. Furthermore, decreasing the thickness T2 of the flange portion 24 reduces the rigidity of the flange portion 24. By reducing the rigidity of the flange portion 24, even if the flange portion 24 is deformed in the motor case 21 before being fixed to the housing 101, the flange portion 24 can be deformed to conform to the housing 101 when fixed to the housing 101. This can correct the curvature of the mounting surface 21b. As described above, by setting the ratio R to 1 or greater, the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101 can be reduced, thereby increasing the contact area between the mounting surface 21b and the housing 101. This reduces the transmission of vibrations from the rotating electric machine 1 to the driven object 100. Furthermore, the mounting surface 21b abuts against the housing 101. This means that the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be reduced without providing a damping member or the like between the motor case 21 and the housing 101. This reduces the number of components and the number of steps required to assemble the rotating electric machine 1 to the driven object 100. As described above, the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be reduced while minimizing the increase in the number of components.

[0032] The cylindrical portion 22, the bottom portion 23, and the flange portion 24 are integrally molded, which makes it easy to manufacture the rotating electrical machine 1.

[0033] The stator 12 is fixed to the cylindrical portion 22 by press fitting or shrink fitting. This allows the stator 12 to be firmly fixed to the cylindrical portion 22. When the stator 12 is fixed into the cylindrical portion 22 by press fitting or shrink fitting, a load is applied to the cylindrical portion 22, which may cause deformation of the cylindrical portion 22. Even in such a case, by setting the ratio R to the above value, deformation of the flange portion 24 can be suppressed, and the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101 can be reduced. Therefore, transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed.

[0034] Second Embodiment Next, a rotating electric machine 1 according to a second embodiment will be described. The rotating electric machine 1 according to this embodiment has the same basic configuration as the first embodiment, and therefore the following description will focus on the differences.

[0035] 4 is a cross-sectional view showing a main portion of a rotating electric machine 1 according to embodiment 2. As shown in FIG. 4, in this embodiment, a first reinforcing portion 31 (reinforcing portion) is formed at a corner where the bottom portion 23 and the cylindrical portion 22 intersect, and a second reinforcing portion 32 is formed at a corner where the bottom portion 23 and the bearing fixing portion 23 a intersect. The first reinforcing portion 31 and the second reinforcing portion 32 improve the rigidity of the bottom portion 23.

[0036] The first reinforcing portion 31 is a connecting portion that connects the upper surface of the bottom portion 23 and the inner circumferential surface of the cylindrical portion 22. In a cross-sectional view taken along the central axis O, the first reinforcing portion 31 has a linear shape that extends radially inward as it approaches the lower side. The inner surface of the first reinforcing portion 31 may have a concave curved surface shape. The second reinforcing portion 32 is a connecting portion that connects the upper surface of the bottom portion 23 and the radial side surface of the bearing fixing portion 23a. In a cross-sectional view taken along the central axis O, the second reinforcing portion 32 has a linear shape that extends radially outward as it approaches the lower side. The inner surface of the second reinforcing portion 32 may have a concave curved surface shape.

[0037] As described above, in the rotating electric machine 1 according to this embodiment, the first reinforcing portion 31 is formed at the corner where the bottom portion 23 and the cylindrical portion 22 intersect. This improves the rigidity of the bottom portion 23 and more effectively suppresses deformation of the flange portion 24 during, for example, the manufacturing of the rotating electric machine 1. This reduces the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101, and more effectively suppresses transmission of vibrations of the rotating electric machine 1 to the driven object 100.

[0038] Third Embodiment Next, a rotating electric machine 1 according to a third embodiment will be described. The rotating electric machine 1 according to this embodiment has the same basic configuration as the first embodiment, and therefore the following description will focus on the differences.

[0039] FIG. 5 is a cross-sectional view showing a main portion of a rotating electric machine 1 according to a third embodiment. FIG. 6 is a view of the main portion of the rotating electric machine 1 according to the third embodiment, as viewed from below. As shown in FIGS. 5 and 6 , in this embodiment, a groove 34 is formed in the mounting portion 21 a. The groove 34 is disposed between the bolt hole 24 a of the flange portion 24 and the positioning portion 25. The groove 34 is recessed upward from the mounting surface 21 b. That is, the groove 34 opens toward the housing 101. The groove 34 is disposed at a position radially overlapping with the flange portion 24. By providing the groove 34, the rigidity of the mounting portion 21 a can be reduced, making it easier to deform the flange portion 24 to fit the housing 101 when fixing the flange portion 24 to the housing 101.

[0040] As described above, in the rotating electric machine 1 according to this embodiment, the groove 34 that opens toward the housing 101 is formed in the portion between the positioning portion 25 of the motor case 21 and the bolt hole 24a. This makes it easier to deform the flange portion 24 to fit the housing 101 when fixing the flange portion 24 to the housing 101, and more effectively corrects the curvature of the mounting surface 21b. Therefore, the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101 can be reduced, and transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be more effectively suppressed.

[0041] Modification of Embodiment 3. Figure 7 is a view of the main parts of a rotating electric machine 1 according to a modification of Embodiment 3, viewed from below. As shown in Figure 7, the groove 34 may be provided around the entire circumferential circumference of the motor case 21. In this case, when the flange 24 is fixed to the housing 101, it becomes easier to deform the flange 24 so that it conforms to the housing 101. Therefore, it is possible to more effectively suppress transmission of vibrations of the rotating electric machine 1 to the driven object 100.

[0042] Fourth Embodiment Next, a rotating electric machine 1A according to a fourth embodiment will be described. The rotating electric machine 1A according to this embodiment has the same basic configuration as that of the first embodiment, and therefore the following description will focus on the differences.

[0043] FIG. 8 is a schematic cross-sectional view of a rotating electric machine 1A according to a fourth embodiment. In this embodiment, the motor 10 of the rotating electric machine 1A is a permanent magnet synchronous motor. That is, in this embodiment, the rotor 13 includes a rotor core 13a and a plurality of permanent magnets 13b. The rotor core 13a is cylindrical. The rotor core 13a is provided around the rotating shaft 11 and fixed to the rotating shaft 11. The plurality of permanent magnets 13b are provided on the outer circumferential surface of the rotor core 13a. The plurality of permanent magnets 13b are arranged so that the polarities (south poles and north poles) on the outer circumferential surface of the rotor 13 alternate along the circumferential direction. The stator core 12a of the stator 12 has a core back formed in an annular shape and a plurality of teeth protruding radially inward from the core back. The plurality of coils 12b are formed by winding a wire around each of the plurality of teeth in a concentrated winding manner. The multiple coils 12b may be formed by winding a wire around multiple teeth in a distributed manner.

[0044] FIG. 9 is a graph showing the values ​​of the fractional-pitch winding factor, distributed winding factor, and winding factor for 8-pole, 9-slot, 10-pole, 9-slot, 10-pole, 12-slot, and 14-pole, 12-slot permanent magnet synchronous motors. Here, an 8-pole, 9-slot permanent magnet synchronous motor is a permanent magnet synchronous motor in which the permanent magnet 13b has eight poles and the stator core 12a has nine teeth. Furthermore, a permanent magnet synchronous motor in which the number of poles of the permanent magnet 13b and the number of teeth of the stator core 12a are set to an integer multiple of the number of poles and teeth of an 8-pole, 9-slot motor is called an 8-pole, 9-slot series permanent magnet synchronous motor. The winding factor of an 8-pole, 9-slot series permanent magnet synchronous motor is the same as that of an 8-pole, 9-slot permanent magnet synchronous motor. The same applies to the 10-pole, 9-slot, 10-pole, 12-slot, and 14-pole, 12-slot motors.

[0045] As shown in FIG. 9 , when the motor 10 of the rotating electric machine 1A is a permanent magnet synchronous motor with an 8-pole, 9-slot, 10-pole, 9-slot, 10-pole, 12-slot, or 14-pole, 12-slot configuration, the winding factor for the fundamental harmonic is high, allowing for increased output torque of the rotating electric machine 1A. Therefore, a low-cost, high-performance rotating electric machine 1A can be provided. However, in this case, electromagnetic forces that deform the rotor core 13a into an ellipse may be generated, potentially increasing vibrations of the rotating electric machine 1A. However, even in such cases, setting the ratio R to the above value can suppress transmission of vibrations of the rotating electric machine 1A to the driven object 100.

[0046] Fifth Embodiment Next, a rotating electric machine 1B according to a fifth embodiment will be described. The rotating electric machine 1B according to this embodiment has the same basic configuration as the fourth embodiment, and therefore the following description will focus on the differences.

[0047] Fig. 10 is a schematic cross-sectional view of a rotating electric machine 1B according to embodiment 5. As shown in Fig. 10, in this embodiment, rotating electric machine 1B further includes a control device 41 and a connector 44. Also, similar to embodiment 4, motor 10 of rotating electric machine 1B is a permanent magnet synchronous motor.

[0048] The control device 41 is disposed above the motor 10. That is, the control device 41 is disposed on the axially opposite side of the motor 10 from the bottom portion 23. The control device 41 includes a circuit board 42 and an electronic circuit 43 provided on the circuit board 42. The circuit board 42 is, for example, a multilayer printed circuit board formed by stacking multiple insulating layers and multiple conductor layers. The electronic circuit 43 includes an inverter circuit that drives the motor 10, a control circuit that controls the inverter circuit, and the like. Electronic components such as power semiconductor elements that form the inverter circuit and a CPU that performs arithmetic processing are mounted on the circuit board 42. These electronic components and the circuit pattern formed on the circuit board 42 form the electronic circuit 43. The circuit board 42 is covered from above by a cover 46.

[0049] In this embodiment, motor case 21 further has a protrusion 29 that protrudes radially outward from the upper end of cylindrical portion 22. Circuit board 42 is supported by upper housing 27 and protrusion 29. Circuit board 42 is fixed to upper housing 27 and protrusion 29 with screws (not shown).

[0050] The connector 44 is provided on the underside of the protrusion 29. The connector 44 is used to connect the rotating electric machine 1 to an external power supply, an external sensor, and the like. The connector 44 is electrically connected to the electronic circuit 43. Power from the external power supply and signals from the external sensors are transmitted to the electronic circuit 43 via the connector 44.

[0051] As described above, the rotating electric machine 1B according to this embodiment further includes a control device 41 that controls the motor 10. The control device 41 is disposed on the axial side of the motor 10 opposite the bottom portion 23. This allows the motor 10 and the control device 41 to be provided integrally in the rotating electric machine 1B. Furthermore, because the control device 41 is disposed on the axial side of the motor 10 opposite the bottom portion 23, transmission of vibrations from the motor 10 to the control device 41 can be suppressed compared to when the control device 41 is disposed on the bottom portion 23 side (i.e., on the output side of the motor 10).

[0052] Sixth Embodiment The rotating electric machines 1, 1A, and 1B according to the above-described embodiments are suitable for use in an electric power steering device mounted on a vehicle. As the sixth embodiment, an electric power steering device 200 having the rotating electric machine 1 will be described.

[0053] Fig. 11 is a perspective view of an electric power steering device 200 according to embodiment 6. As shown in Fig. 11 , the electric power steering device 200 according to this embodiment includes a rotating electric machine 1, a gear mechanism 201, a steering mechanism 202, wheels 203, a steering wheel 204, a steering shaft 205, and a torque sensor 206.

[0054] The motor 10 of the rotating electric machine 1 is used as an auxiliary motor that transmits the driving force generated by the motor 10 to a steering mechanism 202 as a steering assist force. The gear mechanism 201 connects the rotating shaft 11 of the rotating electric machine 1 to a steering shaft 205. The gear mechanism 201 transmits the driving force generated by the motor 10 to a steering mechanism 202 of the vehicle. The gear mechanism 201 corresponds to the driven object 100 in the above embodiment. The steering wheel 204 is operated by a driver who drives the vehicle and can be rotated left or right. The steering shaft 205 is connected to the steering wheel 204. The steering shaft 205 transmits the steering torque generated by the steering wheel 204 to the steering mechanism 202 connected to the wheels 203. The torque sensor 206 is attached to the steering shaft 205. The torque sensor 206 detects the steering torque generated by the steering wheel 204.

[0055] When vibrations of the rotating electric machine 1 are transmitted to the gear mechanism 201 as the driven object 100, causing the gear mechanism 201 to vibrate, abnormal noise is generated. However, by using the rotating electric machine 1 according to the above embodiment, it is possible to suppress the vibrations of the rotating electric machine 1 from being transmitted to the gear mechanism 201, thereby suppressing the vibrations of the gear mechanism 201 and the generation of abnormal noise.

[0056] It is possible to combine the embodiments, or to modify or omit any of the embodiments as appropriate.

[0057] FIG. 12 is a schematic cross-sectional view of a rotating electric machine 1 according to a modified example of the first embodiment. As shown in FIG. 12 , the motor case 21 may include a first frame portion 51 that forms the cylindrical portion 22 and a second frame portion 52 that forms the bottom portion 23, the plurality of flange portions 24, and the positioning portion 25. That is, the cylindrical portion 22, the bottom portion 23, the plurality of flange portions 24, and the positioning portion 25 may be formed as separate members. The first frame portion 51 has a fitting recess 51a. The fitting recess 51a is formed on the inner circumferential surface at the lower end of the cylindrical portion 22. The second frame portion 52 has a fitting protrusion 52a. The fitting protrusion 52a is formed so as to protrude upward from the upper surface of the outer periphery of the bottom portion 23. The first frame portion 51 and the second frame portion 52 are assembled by fitting the fitting protrusion 52a into the fitting recess 51a, thereby forming the motor case 21. In order to firmly fix the first frame portion 51 and the second frame portion 52, it is preferable that the fitting protrusion 52a be press-fitted into the fitting recess 51a. The first frame portion 51 and the second frame portion 52 may also be fixed by screwing.

[0058] In the electric power steering device 200 of embodiment 6, any of the rotating electric machines 1 of embodiments 1 to 3, the rotating electric machine 1A of embodiment 4, and the rotating electric machine 1B of embodiment 5 may be used.

[0059] DESCRIPTION OF SYMBOLS 1, 1A, 1B... Rotating electric machine, 10... Motor, 11... Rotating shaft, 12... Stator, 13... Rotor, 13a... Rotor core, 13b... Permanent magnet, 21... Motor case, 21a... Mounting portion, 21b... Mounting surface, 22... Cylindrical portion, 23... Bottom, 24... Flange portion, 24a... Bolt hole, 25... Positioning portion, 31... First reinforcing portion (reinforcing portion), 34... Groove portion, 41... Control device, 44... Connector, 100... Driven object, 200... Electric power steering device

Claims

1. A rotating electric machine attached to a drive target, A motor having a rotating shaft, a rotor fixed to the rotating shaft, and a stator disposed outside the rotor; a motor case that houses the motor; Equipped with The motor case includes: a cylindrical portion extending along an axial direction of the rotating shaft and to which the stator is fixed; a bottom portion covering one end portion of the cylindrical portion in the axial direction; A flange portion protruding from an outer peripheral surface of the bottom portion; having the flange portion has a mounting surface that comes into contact with a housing of the driven object and is fixed to the housing, The ratio of the thickness of the bottom portion to the thickness of the flange portion is 1 or more. Rotating electric motor.

2. The rotating electric machine according to claim 1 , wherein the cylindrical portion, the bottom portion, and the flange portion are integrally formed.

3. 3. The rotating electric machine according to claim 1, wherein the stator is fixed to the cylindrical portion by press fitting or shrink fitting.

4. The rotating electric machine according to claim 1 , further comprising a reinforcing portion formed at a corner where said bottom portion and said cylindrical portion intersect.

5. the motor case further includes a positioning portion that protrudes from the bottom portion toward one side in the axial direction and is inserted into an opening formed in the housing of the driven object, The flange portion has a bolt hole through which a bolt to be fastened to the housing is inserted, a groove portion that opens toward the housing is formed in a portion of the motor case between the positioning portion and the bolt hole; 3. A rotating electric machine according to claim 1 or 2.

6. The rotating electric machine according to claim 5 , wherein the groove is provided in the motor case over an entire circumference in a circumferential direction of the rotating shaft.

7. 3. The rotating electric machine according to claim 1, wherein the motor is a permanent magnet synchronous motor, the rotor comprising a rotor core fixed to the rotating shaft and a plurality of permanent magnets provided on an outer circumferential surface of the rotor core.

8. 8. The rotating electric machine according to claim 7, wherein the motor is a permanent magnet synchronous motor of an 8-pole, 9-slot series, a 10-pole, 9-slot series, a 10-pole, 12-slot series, or a 14-pole, 12-slot series.

9. A control device for controlling the motor is further provided. The control device is disposed on the opposite side of the motor from the bottom in the axial direction.

3. A rotating electric machine according to claim 1 or 2.

10. 3. The rotating electric machine according to claim 1, wherein the motor is used as an auxiliary motor for an electric power steering device.