Rotary electric machine

Abstract

This rotary electric machine comprises: a stator around which a winding is wound; a rotor rotatably arranged further on the inner diameter side than the stator; and a cylindrical housing for housing the stator and the rotor. The housing is formed so as to be separated by a predetermined distance from a position in which the stator is provided in the axial direction, and the housing has, on an inner wall thereof, a protrusion protruding radially inward.

Description

rotating electrical machines

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

[0002] To be environmentally conscious, electric vehicles require drive units to be smaller and lighter in terms of mountability and efficiency, and quieter in terms of comfort. As a method for quieting the motor, for example, Patent Document 1 discloses a technology in which a motor has a structure in which a protrusion that protrudes in the circumferential direction of an inner housing and a groove that is provided in an outer housing and into which the protrusion fits in the circumferential direction, thereby changing the direction of propagating vibration from the radial direction to the circumferential direction and reducing the effect of radial vibration in the outer housing, thereby reducing vibration and noise in the outer housing.

[0003] Japanese Patent Application Laid-Open No. 2022-180062

[0004] In the configuration described in Patent Document 1, the fitting portion changes the vibration from the radial direction to the circumferential direction, thereby reducing the radial vibration, but there is a possibility that the circumferential vibration due to torque ripple will increase. In addition, when suppressing such circumferential vibration, it is desirable that the fitting portion of the parts inside the inner housing be formed in the circumferential direction, but this creates the problem of radial vibration being more likely to propagate.

[0005] The rotating electric machine comprises a stator having a winding wound thereon, a rotor rotatably arranged radially inward of the stator, and a cylindrical housing that accommodates the stator and the rotor, the housing being formed at a predetermined distance in the axial direction from the position where the stator is provided, and having a protrusion that protrudes radially inward on the inner wall of the housing.

[0006] According to the present invention, it is possible to provide a rotating electrical machine that achieves a reduction in radiated sound.

[0007] FIG. 6 is a diagram showing an example of a drive unit. FIG. 6 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 6 is a cross-sectional view of a drive unit according to one embodiment of the present invention. FIG. 7 is a diagram explaining the configuration of an inner housing according to one embodiment of the present invention. FIG. 8 is a diagram showing vibration modes at a protruding portion of an inner housing according to one embodiment of the present invention. FIG. 9 is a diagram showing the magnitude of vibration of a drive unit caused by the zeroth-order circular vibration of a stator according to one embodiment of the present invention. FIG. 10 is a diagram showing the natural frequencies of each vibration mode in FIG. 6. FIG. 11 is a diagram showing higher-order vibration modes at a protruding portion according to one embodiment of the present invention. FIG. 12 is a diagram showing the installation range of a protruding portion according to one embodiment of the present invention. FIG. 13 is a first modified example. FIG. 14 is a second modified example.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0009] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0010] (One embodiment and overall configuration) (FIGS. 1 and 2) The drive unit 1 is used as a drive source for an electric vehicle such as an electric car or a hybrid vehicle, and is mounted on the vehicle. The drive unit 1 includes, for example, an inverter 2 as an electronic device, a motor 3, and a reducer 4. The motor 3 and the reducer 4 are connected to each other. The reducer 4 has a gear case 40, from which an output shaft 41 protrudes. A drive shaft (not shown) that drives a tire (not shown) is connected to the outer end of the output shaft 41. The reducer 4 is a mechanism that converts and transmits the rotational speed and torque associated with the driving force, and converts the rotational speed and torque of the motor 3 and transmits them to the drive shaft via the output shaft 41.

[0011] An inverter 2 is connected to the motor 3. The inverter 2 has an inverter case 21 and an inverter cover 22. An electric circuit 20 is provided inside the inverter case 21. The inverter 2 converts DC power from a battery or the like (not shown) into AC power and supplies it to the motor 3, and controls the power supply to the motor 3. The drive unit 1 generates a driving torque or a braking torque according to a command from the inverter 2.

[0012] The motor 3 has a stator 32, a rotor 33, an inner housing 31, and an outer housing 30. A winding (not shown) is wound around the stator 32, and the rotor 33 is rotatably disposed radially inward of the stator 32. The stator 32 and the rotor 33 are fixed and housed within the inner periphery of the cylindrical inner housing 31 by, for example, shrink fitting. The inner housing 31 is housed within the outer housing 30 by fastening and fixing the fixing portions 36a to the outer housing 30 with bolts or the like. Thus, the motor 3 is composed of the inner housing 31 that holds the stator 32, and the outer housing 30 that holds the inner housing 31.

[0013] A refrigerant flow path 34 for flowing a refrigerant such as cooling water is provided between the inner housing 31 and the outer housing 30. A seal material 35 for sealing the refrigerant in the flow path is provided in the refrigerant flow path 34. This ensures heat dissipation.

[0014] The motor 3 vibrates due to electromagnetic excitation forces generated in the gap between the rotor 33 and the stator 32 when driven, and is therefore a vibration source for the drive unit 1. Within the motor 3, the vibration of the stator 32 is propagated to the inner housing 31, and then to the outer housing 30 via the inner housing 31 and the fixed portion 36a of the outer housing 30. As a result, radiated sound is generated from the vibration of the outer housing 30.

[0015] Among the vibrations of the stator 32, the circular zero-order vibration, which is a vibration mode in which the stator 32 uniformly expands and contracts in the radial direction, is a vibration that is difficult to suppress with the rigidity of the inner housing 31. Therefore, the circular zero-order vibration of the stator 32 tends to increase the noise radiated from the drive unit 1 and the frequency, and higher-order vibration modes are excited in the outer housing 30 that radiates the sound. Therefore, to address this, it is necessary to increase the rigidity of the entire outer housing 30. As a result, even if measures are taken to reduce the radiated noise, the drive unit 1 still becomes heavy, which is a problem. The drive unit 1 is required to reduce noise to improve vehicle comfort, while also being lightweight to increase cruising range. Therefore, noise reduction without increasing weight is necessary.

[0016] (Figs. 3 and 4) In consideration of the issues with the above basic configuration, the present invention achieves a reduction in radiated sound from the drive unit 1 caused by the zeroth-order circular vibration of the stator 32 while suppressing an increase in the weight of the drive unit 1. Fig. 4(a) is a cross-sectional view of the inner housing as seen from the axial direction, and Fig. 4(b) is a cross-sectional view of the inner housing as seen from the radial direction.

[0017] The inner housing 31 is formed at a predetermined distance in the axial direction from the position where the stator 32 is provided, and has a protrusion 31a that protrudes radially inward from the inner wall of the inner housing 31. Note that in Figure 4(b), the thickness h of the protrusion 31a and the length L that protrudes from the inner housing 31 are shown.

[0018] (FIG. 5) In the inner housing 31, a vibration mode 37a appears in which the protrusion 31a vibrates in the axial direction (up and down in the drawing) due to the zero-order circular vibration of the stator 32. At this time, the protrusion 31a vibrates in the axial direction, and at the same time, the portion of the inner housing 31 that holds the stator 32 vibrates in the radial direction, as shown by vibration 39.

[0019] The protrusion 31a provided on the inner housing 31 axially away from the position of the stator 32 excites a vibration mode 37a when the circular zeroth-order vibration of the stator 32 is excited, and furthermore, the natural frequency of the vibration mode 37a is made to match the natural frequency of the circular zeroth-order vibration of the stator 32. As a result, the vibration mode 37a of the protrusion 31a acts as a dynamic vibration absorber for the circular zeroth-order vibration of the stator 32, thereby reducing the circular zeroth-order vibration of the stator 32. In this way, the noise radiated from the drive unit 1 can be reduced.

[0020] In order to match the natural frequency of vibration mode 37a in protrusion 31a with the natural frequency of the circular zeroth vibration of stator 32, the natural frequency may be adjusted by changing the values ​​of length L and thickness H of protrusion 31a shown in Figure 4.

[0021] (Fig. 6 and Fig. 7) Fig. 6 is a diagram showing the magnitude of vibration of the drive unit caused by the zeroth-order circular vibration of the stator when the natural frequency of the vibration mode of the protrusion is changed. In Fig. 6, the vertical axis shows the ratio of the vibration level of each of the configurations (1) to (4) to the peak vibration level of a conventional structure in which no protrusion is provided on the inner housing.

[0022] Fig. 7 is a table showing the ratio of the natural frequency of the vibration mode of the protrusion to the circular zero-order vibration of the stator for the configurations (1) to (4) shown in Fig. 6. Note that, in verifying the magnitude of the vibration, the natural frequency of the vibration mode 37a of the protrusion 31a was changed by changing only the length L of the protrusion 31a without changing the thickness H of the protrusion 31a.

[0023] 6 and 7, when the inner housing 31 is configured as shown in (2) of the configurations (1) to (4) with the protrusion 31a, the natural frequency of the protrusion 31a is the same as the natural frequency of the zeroth-order circular vibration of the stator (the ratio of natural frequencies is 1.0), and the greatest vibration reduction effect is achieved, compared to the vibration level of a conventional structure without the protrusion 31a. Thus, it can be seen that at a predetermined vibration level, the vibration mode 37a of the protrusion 31a functions as a dynamic vibration absorber for the zeroth-order circular vibration of the stator 32.

[0024] 6 and 7 (3) and (4) show a higher-order vibration mode 37b in the protruding portion 31a, and as shown in Fig. 8, has the characteristic that the phase is opposite at the boundary of the circumferential half of the inner housing 31. Because the circular zeroth-order vibration of the stator 32 is a vibration mode in which the stator 32 vibrates uniformly in the radial direction, the higher-order vibration mode 37b in which a phase difference occurs is able to suppress the circular zeroth-order vibration of the stator 32, although its effect is smaller than that of the vibration mode 37a (Fig. 5).

[0025] (FIG. 9) Protruding portion 31a of the inner housing is provided within the ranges shown in installation ranges 38a and 38b, so that the vibration mode of protruding portion 31a is excited to suppress the circular zero-order vibration of stator 32. If protruding portion 31a were provided in a position that overlaps with fixed portion 36a in the axial direction, the rigidity of fixed portion 36a would suppress the vibration of protruding portion 31a, reducing its effectiveness as a dynamic vibration absorber for suppressing the circular zero-order vibration of stator 32.

[0026] The installation ranges 38a and 38b of the protrusion 31a are located so as not to overlap in the axial direction with the fixing portions 36a of the inner housing 31 and the outer housing 30 and the holding portion 32a of the stator 32. As shown in Fig. 9, the installation range 38a of the protrusion 31a is located between the fixing portions 36a that fix the inner housing 31 to the outer housing 30 and the end of the stator 32. The installation range 38b is located between the other end of the stator 32 and the end of the inner housing 31. The protrusion 31a may be located only in the installation range 38a, only in the installation range 38b, or in both the installation ranges 38a and 38b.

[0027] (First Modification) (FIG. 10) The inner housing 31 is fixed to the outer housing 30 at both axial ends by fixing portions 36a and 36b. For example, fixing portions 36a are fixed by bolts and fixing portions 36b are press-fitted. Even with this configuration, it is possible to suppress the zeroth-order circular vibration of the stator 32 caused by the vibration mode excitation of the protrusions 31a.

[0028] 10, the installation range 38a of the protrusion 31a is a position in the axial direction between the fixing portion 36a that fixes the inner housing 31 to the outer housing 30 and the end of the stator 32, and the protrusion 31a is in a position where it does not overlap with the fixing portion 36a in the axial direction. Also, the installation range 38b of the protrusion 31a is a position in the axial direction between the other end of the stator 32 and the fixing portion 36b, and the protrusion 31a is in a position where it does not overlap with the fixing portion 36b in the axial direction.

[0029] (Second Modification) (FIG. 11) FIG. 11(a) is a cross-sectional view of the inner housing as viewed from the axial direction, and FIG. 11(b) is a cross-sectional view of the inner housing as viewed from the radial direction. The protrusions 31a may not be uniformly formed in the circumferential direction. The protrusions 31a in FIG. 11 are formed in the circumferential direction, but have cutouts 31b in some parts. Even with this configuration, the natural frequency of the protrusions 31a can be adjusted to match the natural frequency of the zeroth-order circular vibration of the stator 32, allowing the protrusions 31a to function as a dynamic vibration absorber. Note that the number of divisions of the protrusions 31a in the circumferential direction is not limited to two as shown in FIG. 11, and they may be divided into multiple parts.

[0030] The configuration of the present invention has been described above, but the housing configuration is not limited to a double structure of inner housing 31 and outer housing 30, and can also be realized with a structure of only one housing, and a structure in which stator 32 is attached to the inner wall of that housing.

[0031] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0032] (1) A rotating electric machine includes a stator 32 wound with a winding, a rotor 33 rotatably disposed radially inward of the stator 32, and a cylindrical housing that accommodates the stator 32 and the rotor 33. The housing is formed at a predetermined distance in the axial direction from the position where the stator 32 is provided, and has a protrusion 31a that protrudes radially inward on the inner wall of the housing. This configuration makes it possible to provide a rotating electric machine that achieves reduced radiated sound.

[0033] (2) The housing includes an inner housing 31 that houses the stator 32 and an outer housing 30 that houses the inner housing 31. A refrigerant flow path 34 through which a refrigerant flows is formed between the inner housing 31 and the outer housing 30. This configuration ensures cooling performance while reducing radiated noise.

[0034] (3) The protruding portion 31a is provided axially between the fixing portion 36a (36b) that fixes the inner housing 31 to the outer housing 30 and the end of the stator 32, and does not overlap with the fixing portion 36a (36b) in the axial direction. This reduces radiated noise.

[0035] The present invention is not limited to the above-described embodiments, and various modifications and combinations of other configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted.

[0036] REFERENCE SIGNS LIST 1 Drive device 2 Inverter 3 Motor 4 Reducer 20 Electric circuit 21 Inverter case 22 Inverter cover 30 Outer housing 31 Inner housing 31a Protrusion 31b Cutout 32 Stator 32a Stator holding portion 33 Rotor 34 Refrigerant flow path 35 Sealing material 36a Fixing portion 36b Fixing portion 37a Vibration mode of protrusion 37b Higher vibration mode of protrusion 38a Installation range of protrusion 38b Installation range of protrusion 39 Radial vibration of inner housing 40 Gear case 41 Output shaft

Claims

1. A rotating electric machine comprising: a stator having a winding wound thereon; a rotor rotatably arranged radially inward of the stator; and a cylindrical housing that accommodates the stator and the rotor, the housing being formed at a predetermined distance in the axial direction from a position at which the stator is provided, and having a protrusion that protrudes radially inward on the inner wall of the housing.

2. A rotating electric machine according to claim 1, wherein the housing comprises an inner housing that houses the stator, and an outer housing that houses the inner housing, and a refrigerant flow path for flowing a refrigerant is formed between the inner housing and the outer housing.

3. A rotating electric machine according to claim 2, wherein the protrusion is provided axially between a fixing portion that fixes the inner housing to the outer housing and an end of the stator, and does not overlap with the fixing portion in the axial direction.

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