Rotating 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

Technical Field

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

Background Art

[0002] A rotating electric machine is attached to a driven object and transmits the driving force generated from the motor of the rotating electric machine to the driven object. Patent Document 1 discloses an electric power steering device that adds the driving force generated from a motor as a steering assist force to a steering mechanism of a vehicle. 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, in order to suppress the transmission of the vibration of the rotating electric machine to the gear mechanism, a metal plate for vibration damping is provided between the motor case of the rotating electric machine and the gear housing. In this case, the number of parts increases, and the man-hours required for assembling the rotating electric machine to the driven object also increase.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a rotating electric machine capable of suppressing the transmission of the vibration of the rotating electric machine to the driven object while suppressing an increase in the number of parts.

Means for Solving the Problems

[0006] The rotating electric machine according to this disclosure is a rotating electric machine attached to a drive object, comprising a motor having a rotating shaft, a rotor fixed to the rotating shaft, and a stator disposed on the outside of the rotor, and a motor case housing the motor, wherein the motor case has a cylindrical portion extending along the axial direction of the rotating shaft to which the stator is fixed, a bottom portion covering one end of the cylindrical portion in the axial direction, and a flange portion protruding from the outer circumferential surface of the bottom portion, the flange portion having a mounting surface that abuts against the housing of the drive 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 more. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a rotating electric machine that can suppress the transmission of vibrations from the rotating electric machine to the driven object while keeping the number of parts to a minimum. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view of a rotating electric machine according to Embodiment 1. [Figure 2] This graph shows the relationship between the vibration value of the driven object and the right-angle index of the mounting surface after the motor case is assembled to the housing of the driven object. [Figure 3] This graph shows the relationship between the right-angle index of the mounting surface after the motor case is assembled to the housing of the object being driven, and the ratio of the bottom thickness to the flange thickness. [Figure 4] This is a cross-sectional view showing the main part of the rotating electric machine according to Embodiment 2. [Figure 5] This is a cross-sectional view showing the main part of the rotating electric machine according to Embodiment 3. [Figure 6] This is a view from below of the main part of the rotating electric machine according to Embodiment 3. [Figure 7] This is a view from below of the main part of a rotating electric machine according to a modified example of Embodiment 3. [Figure 8] This is a schematic cross-sectional view of a rotating electric machine according to Embodiment 4. [Figure 9] This graph shows the values ​​of the short-section winding coefficient, distributed winding coefficient, and winding coefficient for 8-pole 9-slot, 10-pole 9-slot, 10-pole 12-slot, and 14-pole 12-slot permanent magnet synchronous motors. [Figure 10] This is a schematic cross-sectional view of a rotating electric machine according to Embodiment 5. [Figure 11] This is a perspective view of the electric power steering device according to Embodiment 6. [Figure 12] This is a schematic cross-sectional view of a rotating electric machine according to a modified example of Embodiment 1. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. However, the scope of this disclosure is not limited to the embodiments described below and can be modified at will within the scope of the technical idea of ​​this disclosure.

[0010] Embodiment 1. Figure 1 is a schematic cross-sectional view of the rotating electric machine 1. The rotating electric machine 1 comprises a motor 10, a motor case 21, and an upper housing 27. The motor 10 comprises a rotating shaft 11, a stator 12, and a rotor 13. The rotating electric machine 1 is attached to the drive target 100 and transmits the driving force generated from the motor 10 of the rotating electric machine 1 to the drive target 100. In the following explanation, 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 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. Viewing from the axial direction may be referred to as a plan view. In a plan view, the direction intersecting the central axis O may be referred to as the radial direction, and the direction revolving 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 the 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 rotary 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 arranged with a gap outside the rotor 13 in the radial direction. 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 laminating a plurality of electromagnetic steel sheets 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 using the magnetic flux generated from the stator core 12a when current is passed through the coil 12b. Note that 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 the housing 101 of the driven object 100. The motor case 21 is made of metal. As a specific material of the motor case 21, for example, an aluminum-based alloy is suitable. The motor case 21 is produced, for example, by performing cutting on a molded body obtained from an aluminum-based alloy by die casting or the like.

[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 portion 24, and the positioning portion 25 are integrally formed.

[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 or shrink-fitting or the like.

[0017] The base portion 23 is disc-shaped. The base portion 23 covers the lower end of the cylindrical portion 22. A bearing fixing portion 23a is provided in the center of the base portion 23 in a plan view. The bearing fixing portion 23a is provided so as to protrude upward from the upper surface of the base 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 installed in the through hole of the bearing fixing portion 23a.

[0018] The flange portion 24 is provided so as to protrude radially outward from the outer circumferential surface of the bottom portion 23. In this embodiment, there are two flange portions 24. The number of flange portions 24 may be three or more. Bolt holes 24a are formed in the flange portion 24 through which 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 drive target 100. The positioning portion 25 positions the motor case 21 relative to the housing 101.

[0020] The flange portion 24 and the portion of the bottom portion 23 located outside the positioning portion 25 form a 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. That is, 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, forming the lower surface of the mounting portion 21a. The lower surface of the mounting portion 21a is called 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, let T1 be the thickness of the bottom portion 23 (i.e., the axial length of the bottom portion 23), and T2 be the thickness of the flange portion 24 (i.e., the axial length of the flange portion 24). Let R be the ratio of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24. 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 preferable that it is 2 or greater.

[0022] The upper housing 27 is disc-shaped. The upper housing 27 is provided 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. In a plan view, a through hole is formed in the center of the upper housing 27 through which the rotating shaft 11 passes. The second bearing 17 is installed in the through hole of the upper housing 27.

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

[0024] The assembly of the motor case 21 to the housing 101 will now be described. The positioning part 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 motor case 21 is attached to the housing 101 by inserting the bolt 103 through the bolt hole 24a of the flange part 24 and fastening it to the housing 101.

[0025] Here, due to manufacturing tolerances of the motor case 21, deformation of the motor case 21 during the manufacturing of the rotating electric machine 1, the flange portion 24 may deform, causing the mounting surface 21b to bend. 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 deform, causing the cylindrical portion 22 to bulge radially outward. As the cylindrical portion 22 deforms, the flange portion 24 deforms so that it bends downward as it extends radially outward, and the mounting surface 21b also bends so that it bends downward as it extends radially outward. When the mounting surface 21b is bent, 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. As a result, vibrations transmitted from the rotating electric machine 1 to the driven object 100 may increase.

[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 1 or more, the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed. The reason for this will be explained with reference to Figures 2 and 3.

[0027] Figure 2 is a graph showing the relationship between the measured vibration value of the driven object 100 and the right-angle index of the mounting surface 21b after the motor case 21 is assembled to the housing 101 of the driven object 100 (hereinafter also referred to as the right-angle index of the mounting surface 21b after assembly), which was calculated using CAE analysis. The vertical axis represents the vibration value of the driven object 100. A larger vibration value of the driven object 100 indicates a larger vibration transmitted from the rotating electric machine 1 to the driven object 100. The horizontal axis represents the right-angle index of the mounting surface 21b after assembly. The right-angle index of the mounting surface 21b after assembly is a value that expresses the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101, with respect to a virtual plane perpendicular to the axial direction. More specifically, the right-angle index of the mounting surface 21b after assembly is a value that represents the magnitude of the deviation of the mounting surface 21b from the virtual plane. The larger the right-angle index of the mounting surface 21b after assembly, the more the mounting surface 21b after assembly is curved downwards as it extends radially outward compared to the virtual plane. As shown in Figure 2, when the right-angle index of the mounting surface 21b after assembly decreases, the vibration value of the driven object 100 decreases. In other words, it can be seen that by reducing the right-angle index of the mounting surface 21b after assembly, the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed. When the right-angle index of the mounting surface 21b after assembly is small, the mounting surface 21b takes on a shape that follows a virtual plane perpendicular to the axial direction. This increases the contact area between the mounting surface 21b and the upper surface of the housing 101, and as a result, it is thought that the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed.

[0028] Figure 3 is a graph showing the relationship between the right-angle 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 right-angle 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 Figure 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 effect of reducing the right-angle index of the mounting surface 21b after assembly becomes greater. When the ratio R is 1 or greater, the thickness T1 of the bottom portion 23 becomes larger or the thickness T2 of the flange portion 24 becomes smaller compared to when the ratio R is less than 1. When the thickness T1 of the bottom portion 23 becomes larger, the rigidity of the bottom portion 23 improves. By improving the rigidity of the bottom portion 23, deformation of the flange portion 24 can be suppressed when the stator core 12a is fixed into the cylindrical portion 22 by press-fitting or shrink-fitting. Therefore, it is thought that the curvature of the mounting surface 21b can be suppressed in the pre-assembly stage, and as a result, the right-angle index of the mounting surface 21b after assembly can be reduced. Also, when the thickness T2 of the flange portion 24 becomes smaller, the rigidity of the flange portion 24 decreases. By reducing the rigidity of the flange portion 24, even if the flange portion 24 is deformed before assembly, the fastening force applied to fasten the bolt 103 to the housing 101 can deform the flange portion 24 to conform to the upper surface of the housing 101. Therefore, it is considered that the curvature of the mounting surface 21b can be corrected, and the right-angle index of the mounting surface 21b after assembly can be reduced.

[0029] From the 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 right-angle index of the mounting surface 21b after assembly increases, and therefore the transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed. Furthermore, when the ratio R is greater than 1, the effect of reducing the right-angle index of the mounting surface 21b after assembly increases even more, and therefore the transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed more effectively. When the ratio R is 2 or greater, the effect of reducing the right-angle index of the mounting surface 21b after assembly increases even further, and therefore the transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed even more effectively.

[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 arranged on the outside of the rotor 13, and a motor case 21 housing the motor 10. The motor case 21 has a cylindrical portion 22 extending along the axial direction to which the stator 12 is fixed, a bottom portion 23 covering one end of the cylindrical portion 22 in the axial direction, and a flange portion 24 protruding from the outer circumferential surface of the bottom portion 23. The flange portion 24 has a mounting surface 21b that abuts against the housing 101 of the drive object 100 and is fixed to the housing 101. The ratio R of the thickness T1 of the bottom portion 23 to the thickness T2 of the flange portion 24 is 1 or more.

[0031] With such a rotating electric machine 1, by setting the ratio R to 1 or greater, the transmission of vibrations from 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 becomes smaller, or the thickness T1 of the bottom portion 23 becomes larger, compared to when the ratio R is less than 1. When the thickness T1 of the bottom portion 23 becomes larger, the rigidity of the bottom portion 23 is improved. By improving the rigidity of the bottom portion 23, deformation of the flange portion 24 during the manufacturing of the rotating electric machine 1 can be suppressed. Also, when the thickness T2 of the flange portion 24 becomes smaller, the rigidity of the flange portion 24 decreases. 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 the flange portion 24 is fixed to the housing 101. This makes it possible to 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, and the contact area between the mounting surface 21b and the housing 101 can be increased. Therefore, the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed. Furthermore, the mounting surface 21b is in contact with the housing 101. In other words, vibrations from the rotating electric machine 1 can be suppressed from being transmitted to the driven object 100 without the need to provide damping members or the like between the motor case 21 and the housing 101. Therefore, an increase in the number of parts and an increase in the man-hours required to assemble the rotating electric machine 1 to the driven object 100 can be suppressed. Therefore, it is possible to suppress the transmission of vibrations from the rotating electric machine 1 to the driven object 100 while keeping the number of parts to a minimum.

[0032] Furthermore, the cylindrical portion 22, the bottom portion 23, and the flange portion 24 are integrally molded. This makes it easier to manufacture the rotating electric machine 1.

[0033] Furthermore, 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. Furthermore, 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 deform. Even in such cases, 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, the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed.

[0034] Embodiment 2. Next, the rotating electric machine 1 according to Embodiment 2 will be described. Since the basic configuration of the rotating electric machine 1 according to this embodiment is the same as that of Embodiment 1, the differences will be the main points to be explained.

[0035] Figure 4 is a cross-sectional view showing the main part of the rotating electric machine 1 according to Embodiment 2. As shown in Figure 4, in this embodiment, a first reinforcing portion 31 (reinforcing portion) is formed at the corner where the bottom portion 23 and the cylindrical portion 22 intersect, and a second reinforcing portion 32 is formed at the corner where the bottom portion 23 and the bearing fixing portion 23a 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 along the central axis O, the first reinforcing portion 31 is a straight line that extends radially inward as it is directed downward. The inner surface of the first reinforcing portion 31 may be a concave curved surface. The second reinforcing portion 32 is a connecting portion that connects the upper surface of the bottom portion 23 to the radial side surface of the bearing fixing portion 23a. In a cross-sectional view along the central axis O, the second reinforcing portion 32 is a straight line that extends radially outward as it is directed downward. The inner surface of the second reinforcing portion 32 may be a concave curved surface.

[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 the manufacturing of the rotating electric machine 1. Consequently, the degree of curvature of the mounting surface 21b after the motor case 21 is assembled to the housing 101 can be reduced, and the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be more effectively suppressed.

[0038] Embodiment 3. Next, the rotating electric machine 1 according to Embodiment 3 will be described. Since the basic configuration of the rotating electric machine 1 according to this embodiment is the same as that of Embodiment 1, the differences will be explained in detail.

[0039] Figure 5 is a cross-sectional view showing the main part of the rotating electric machine 1 according to Embodiment 3. Figure 6 is a view of the main part of the rotating electric machine 1 according to Embodiment 3 from below. As shown in Figures 5 and 6, in this embodiment, a groove 34 is formed in the mounting portion 21a. The groove 34 is located between the bolt hole 24a of the flange portion 24 and the positioning portion 25. The groove 34 is recessed upward from the mounting surface 21b. That is, the groove 34 opens toward the housing 101. The groove 34 is located in a position that overlaps radially with the flange portion 24. By providing the groove 34, the rigidity of the mounting portion 21a can be reduced, making it easier to deform the flange portion 24 to conform to 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, a groove 34 is formed in the portion between the positioning portion 25 and the bolt hole 24a of the motor case 21, opening toward the housing 101. This makes it easier to deform the flange portion 24 to conform to the housing 101 when fixing the flange portion 24 to the housing 101, and the curvature of the mounting surface 21b can be corrected more effectively. 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 the transmission of vibrations from the rotating electric machine 1 to the driven object 100 can be suppressed more effectively.

[0041] A modified example of Embodiment 3. Figure 7 is a view from below of the main part of the rotating electric machine 1 according to a modified embodiment of the third embodiment. As shown in Figure 7, the groove 34 may be provided on the motor case 21 over the entire circumference in the circumferential direction. In this case, when fixing the flange portion 24 to the housing 101, it becomes easier to deform the flange portion 24 to conform to the housing 101. Therefore, the transmission of vibrations of the rotating electric machine 1 to the driven object 100 can be suppressed more effectively.

[0042] Embodiment 4. Next, we will describe the rotating electric machine 1A according to Embodiment 4. Since the basic configuration of the rotating electric machine 1A according to this embodiment is the same as that of Embodiment 1, we will focus on describing the differences.

[0043] Figure 8 is a schematic cross-sectional view of a rotating electric machine 1A according to Embodiment 4. 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 comprises 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 is 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 such that the polarity (S pole and N pole) on the outer circumferential surface of the rotor 13 alternates along the circumferential direction. Furthermore, 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 in a concentrated winding manner around each of the plurality of teeth. The plurality of coils 12b may also be formed by winding a wire in a distributed winding manner around the plurality of teeth.

[0044] Figure 9 is a graph showing the values ​​of the short-pitch winding coefficient, distributed winding coefficient, and winding coefficient 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 one in which the number of poles of the permanent magnet 13b is 8 and the number of teeth of the stator core 12a is 9. 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 integer multiples of the number of poles and teeth of the 8-pole 9-slot motor is called an 8-pole 9-slot series permanent magnet synchronous motor. The winding coefficient in an 8-pole 9-slot series permanent magnet synchronous motor is the same as the winding coefficient of an 8-pole 9-slot permanent magnet synchronous motor. The same applies to 10-pole 9-slot, 10-pole 12-slot, and 14-pole 12-slot motors.

[0045] As shown in Figure 9, when the motor 10 of the rotating electric machine 1A is a permanent magnet synchronous motor of the 8-pole 9-slot series, 10-pole 9-slot series, 10-pole 12-slot series, or 14-pole 12-slot series, the winding coefficient with respect to the fundamental wave is high, and the output torque of the rotating electric machine 1A can be increased. Therefore, a low-cost, high-performance rotating electric machine 1A can be provided. On the other hand, in this case, an electromagnetic force is generated that deforms the rotor core 13a into an ellipse, which may increase the vibration of the rotating electric machine 1A. However, even in such a case, by setting the ratio R to the above value, it is possible to suppress the transmission of vibrations from the rotating electric machine 1A to the driven object 100.

[0046] Embodiment 5. Next, the rotating electric machine 1B according to Embodiment 5 will be described. Since the basic configuration of the rotating electric machine 1B according to this embodiment is the same as that of Embodiment 4, the differences will be explained in detail.

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

[0048] The control device 41 is positioned above the motor 10. That is, the control device 41 is positioned on the side of the motor 10 opposite to the bottom 23 in the axial direction. The control device 41 comprises 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 in which multiple insulating layers and multiple conductive layers are laminated. The electronic circuit 43 includes an inverter circuit for driving the motor 10, a control circuit for controlling the inverter circuit, and so on. Electronic components such as power semiconductor elements that form the inverter circuit and a CPU that performs calculation processing are mounted on the circuit board 42. The electronic circuit 43 is composed of these electronic components and circuit patterns formed on the circuit board 42. The circuit board 42 is covered from above by a cover 46.

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

[0050] The connector 44 is located on the lower surface of the protrusion 29. The connector 44 is used to connect the rotating electric machine 1 to an external power supply and an external sensor. The connector 44 is electrically connected to the electronic circuit 43. Power from the external power supply and signals from the external sensor 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 for controlling the motor 10. The control device 41 is positioned on the side of the motor 10 opposite to the bottom portion 23 in the axial direction. This allows the motor 10 and the control device 41 to be integrated into the rotating electric machine 1B. Furthermore, since the control device 41 is positioned on the opposite side of the motor 10 from the bottom 23 in the axial direction, the transmission of vibrations from the motor 10 to the control device 41 can be suppressed compared to the case where the control device 41 is positioned on the bottom 23 side (i.e., the output side of the motor 10).

[0052] Embodiment 6. The rotating electric machines 1, 1A, and 1B according to the above embodiment are suitably used in electric power steering systems mounted on vehicles. Embodiment 6 describes an electric power steering system 200 having the rotating electric machine 1.

[0053] Figure 11 is a perspective view of the electric power steering device 200 according to Embodiment 6. As shown in Figure 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, a wheel 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 to transmit the driving force generated by the motor 10 to the steering mechanism 202 as steering assist force. The gear mechanism 201 connects the rotating shaft 11 of the rotating electric machine 1 to the steering shaft 205. The gear mechanism 201 transmits the driving force generated from the motor 10 to the vehicle's steering mechanism 202. The gear mechanism 201 corresponds to the driven object 100 in the above embodiment. The steering wheel 204 is operated by the driver of 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 from the steering wheel 204 to the steering mechanism 202, which is connected to the wheel 203. The torque sensor 206 is attached to the steering shaft 205. The torque sensor 206 detects the steering torque from the steering wheel 204.

[0055] When vibrations from the rotating electric machine 1 are transmitted to the gear mechanism 201, which is the driven object 100, and the gear mechanism 201 vibrates, abnormal noise is generated. However, by using the rotating electric machine 1 according to the above embodiment, the transmission of vibrations from the rotating electric machine 1 to the gear mechanism 201 can be suppressed, thereby suppressing vibrations of the gear mechanism 201 and the generation of abnormal noise.

[0056] Furthermore, it is possible to combine the various embodiments, or to modify or omit the embodiments as appropriate.

[0057] Figure 12 is a schematic cross-sectional view of a modified rotating electric machine 1 according to Embodiment 1. As shown in Figure 12, the motor case 21 may have a first frame portion 51 that forms a cylindrical portion 22, and a second frame portion 52 that forms a bottom portion 23, a plurality of flange portions 24, and a 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 from separate members. A fitting recess 51a is formed in the first frame portion 51. The fitting recess 51a is formed on the inner circumferential surface of the lower end of the cylindrical portion 22. A fitting projection 52a is formed in the second frame portion 52. The fitting projection 52a is formed to protrude upward from the upper surface of the outer circumference of the bottom portion 23. By fitting the fitting projection 52a into the fitting recess 51a, the first frame portion 51 and the second frame portion 52 are assembled to form 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 projection 52a is press-fitted into the fitting recess 51a. The first frame portion 51 and the second frame portion 52 may also be fixed by screw fastening.

[0058] In the electric power steering device 200 according to Embodiment 6, any of the rotating electric machine 1 according to Embodiments 1 to 3, the rotating electric machine 1A according to Embodiment 4, or the rotating electric machine 1B according to Embodiment 5 may be used. [Explanation of symbols]

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

Claims

1. A rotating electric machine that is attached to a drive object, A motor having a rotating shaft, a rotor fixed to the rotating shaft, and a stator positioned outside the rotor, A motor case housing the aforementioned motor, Equipped with, The motor case is A cylindrical portion extending along the axial direction of the rotating shaft, to which the stator is fixed, The bottom portion covers one end of the cylindrical portion in the axial direction, A flange portion protruding from the outer circumferential surface of the bottom, It has, The flange portion has a mounting surface that contacts the housing of the object to be driven and is fixed to the housing. The ratio of the thickness of the bottom portion to the thickness of the flange portion is greater than 1. The motor case further comprises a positioning portion that protrudes from the bottom toward one side in the axial direction and is inserted into an opening formed in the housing of the object to be driven, The flange portion has bolt holes through which bolts that fasten to the housing are inserted. A rotating electric machine, wherein a groove is formed in the portion of the motor case between the positioning portion and the bolt hole, opening toward the housing.

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

3. The rotating electric machine according to claim 1 or 2, wherein the stator is fixed to the cylindrical portion by press-fitting or shrink-fitting.

4. The rotating electric machine according to claim 1 or 2, wherein a reinforcing portion is formed at the corner where the bottom portion and the cylindrical portion intersect.

5. The rotating electric machine according to claim 1, wherein the groove portion is provided on the motor case over the entire circumference in the circumferential direction of the rotating shaft.

6. The rotating electric machine according to claim 1 or 2, 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 the outer circumferential surface of the rotor core.

7. The rotating electric machine according to claim 6, 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.

8. The motor further comprises a control device for controlling the motor, The control device is positioned relative to the motor on the side opposite to the bottom in the axial direction, The rotating electric machine according to claim 1 or 2.

9. The rotating electric machine according to claim 1 or 2, wherein the motor is used as an auxiliary motor for an electric power steering system.

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