WO2024004294A1

WO2024004294A1 - Rotating electric machine

Info

Publication number: WO2024004294A1
Application number: PCT/JP2023/011500
Authority: WO
Inventors: 直也三津橋; 泰行齋藤
Original assignee: 日立Astemo株式会社
Priority date: 2022-06-30
Filing date: 2023-03-23
Publication date: 2024-01-04
Also published as: JP2024005950A

Abstract

This rotating electric machine comprises a rotor, an annular stator that faces the rotor with a predetermined separation distance interposed therebetween, and a housing to which the stator is held. The housing comprises: an interior wall that holds the inner surface of the housing in the radial direction; an exterior wall that faces the interior wall in the radial direction; and a connection portion that connects the interior wall and the exterior wall to each other. The interior wall, the exterior wall, and the connection portion form a refrigerant flow path through which a refrigerant can flow. The interior wall has an air gap between the stator and a surface which faces the stator and at least a part of which is overlapped with the connection portion in the radial direction.

Description

rotating electric machine

The present invention relates to a rotating electrical machine.

Reducing the radiated sound generated during the operation of rotating electric machines has been an issue for some time. One of the sources of radiated sound in a rotating electric machine is annular vibration in the radial direction of the stator, which is generated by electromagnetic excitation force generated in the space between the stator and the rotor. Among these, it is known that the radiated sound becomes louder due to annular zero-order vibration, which is a natural vibration mode in which the stator expands in the radial direction.

There are generally two ways to reduce vibration: measures using excitation force and measures using the transmission system. A countermeasure using excitation force for the motor is to reduce the electromagnetic excitation force, but it is necessary to consider the effect on the main performance of the motor, and there are limits to this measure. In addition, in the case of circular zero-order vibration, a common countermeasure for the transmission system is to increase the wall thickness or use ribs to increase the rigidity of the housing to suppress the vibration.

Here, as a method for holding the stator in the housing, for example, there is a method in which the outer circumferential surface of the stator and the inner circumferential surface of the housing are brought into close contact with each other by shrink fitting. When the stator is held in the housing by shrink fitting, since the stator and the housing are in close contact with each other, the zero-order annular vibration becomes a vibration mode in which the stator and the housing expand in the radial direction as a unit. Measures to suppress vibration by increasing the wall thickness or making the housing more rigid with ribs have little effect on such vibration modes, and many ribs and wall thicknesses are required to reach the target performance. weight may be required.

Patent Document 1 discloses a housing, a rotating shaft housed in the housing, a compression section that compresses fluid by rotating the rotating shaft, a rotor that rotates integrally with the rotating shaft, and the housing. An electric compressor comprising: an electric motor having a stator fixed to the compressor and driving the compression section; and a bearing rotatably supporting the rotating shaft with respect to the housing, the housing being an inner housing that houses the motor and to which the stator is fixed; a bearing plate that holds the bearing; an outer housing that houses the inner housing; a discharge housing fixed to the inner housing, the compression section is fixed to the inner housing, the outer housing is fixed to the discharge housing, and the inner housing and the bearing plate, An electric compressor is disclosed, which is fixed by bolts and characterized in that the inner circumferential surface of the outer housing and the outer circumferential surface of the inner housing are separated from each other.

Japanese Patent Application Publication No. 2019-173658

In the invention described in Patent Document 1, the number of parts is large and the number of assembly steps increases.

A rotating electric machine according to a first aspect of the present invention includes a rotor, an annular stator that faces the rotor at a predetermined distance, and a housing in which the stator is held, and the housing includes the an inner wall that holds an inner surface in a radial direction of the housing; an outer wall that faces the inner wall in the radial direction; and a connection portion that connects the inner wall and the outer wall, the inner wall, the outer wall, and the connection. The inner wall forms a refrigerant flow path through which a refrigerant can flow, and the inner wall defines a gap between the stator and a surface that faces the stator and at least partially overlaps with the connection portion in the radial direction. have

According to the present invention, the radiated sound of a rotating electric machine can be reduced without increasing the number of parts.

Cross-sectional view of rotating electrical machine Perspective view of housing Perspective view of the housing with the stator shrink-fitted Conceptual diagram explaining the structure of the cavity Diagram showing the relationship between the ratio of contact area between the inner wall of the housing and the outer peripheral surface of the stator and the magnitude of radiated sound Diagram showing the structure of a stator that forms a cavity Diagram showing the structure of the housing that forms the cavity A diagram showing the effect of the ratio of the inner and outer wall thicknesses of the housing on the magnitude of radiated sound. A diagram showing the shape of the housing in Modification 1 Diagram showing variations of voids

-First embodiment-
A first embodiment of a rotating electric machine will be described below with reference to FIGS. 1 to 7.

FIG. 1 is a cross-sectional view of a rotating electrical machine 100 according to the present invention. The rotating electric machine 100 includes a stator 1, a rotor 2 disposed inside the stator 1, a shaft 4 that rotates in synchronization with the rotor 2, and a cylindrical housing 3 that houses the stator 1, rotor 2, and shaft 4. Equipped with. The shaft 4 extends in the left-right direction in the figure, and the housing 3 has a cylindrical shape centered on the shaft 4. In this embodiment, the horizontal direction in FIG. 1 is referred to as an axial direction J, and the vertical direction in FIG. 1 is referred to as a radial direction R.

When the rotating electrical machine 100 is in operation, an electromagnetic excitation force is generated in the gap between the stator 1 and the rotor 2. This electromagnetic excitation force generates annular vibration in the radial direction R, which propagates to the housing 3 and becomes radiated sound. Among the annular vibrations of the stator 1, the radiated sound is particularly large due to the annular zero-order vibration, which is a natural vibration mode in which the stator 1 expands in the radial direction R relative to the shape before deformation. Below, a detailed configuration of the rotating electrical machine 100, particularly a configuration for reducing the radiated sound of the rotating electrical machine 100 caused by reducing the annular zero-order vibration of the stator 1, will be described.

A predetermined gap exists between the stator 1, which is a non-rotating body, and the rotor 2, which is a rotating body, so as not to inhibit rotation. There is also a gap between the housing 3 and the housing 3. Below, the latter, the gap between the stator 1 and the housing 3, that is, the gap will be explained in detail. The former, the gap between the stator 1 and the rotor 2, will not be particularly explained. In order to distinguish between the two, the gap between the stator 1 and the housing 3 is called a "gap", and the gap between the stator 1 and the rotor 2 is called a "predetermined separation distance".

FIG. 2 is a perspective view of the housing 3. The viewpoint in FIG. 2 has changed by about 90 degrees from FIG. 1, and the vertical direction in the drawing is the axial direction J. In FIG. 2, the direction passing through the central axis of the cylindrical housing 3 and perpendicular to the axial direction J is the radial direction R. Further, in FIG. 2, a circumferential direction C is defined.

The space inside the housing 3 in which the stator 1 is accommodated is called a stator accommodating section 30. The housing 3 includes an inner wall 31 that is in close contact with the outer peripheral surface of the stator 1 and holds the stator 1, and an outer wall 32 that faces the inner wall 31 in the radial direction R. Further, the housing 3 is provided with connecting portions 33 at predetermined intervals in the circumferential direction C, and the inner wall 31 and the outer wall 32 of the housing 3 are connected. A refrigerant flow path 34 is formed in the housing 3 by an inner wall 31, an outer wall 32, and a connecting portion 33. The refrigerant passage 34 is formed across the axial direction J of the housing 3, and allows the refrigerant to circulate through an axial end of the housing 3, such as a gearbox or an inverter case.

FIG. 3 is a perspective view of the housing 3 into which the stator 1 is shrink-fitted. In FIG. 3, the stator 1 is shrink-fitted to the inner peripheral side of the housing 3 shown in FIG. The outer diameter of the stator 1 is larger than the inner diameter of the inner wall 31 of the housing 3, and by shrink-fitting the stator 1 to the housing 3, the inner wall 31 and the outer peripheral surface of the stator 1 are brought into close contact and the stator 1 is held. can do. At this time, the difference between the outer diameter of the stator 1 and the inner diameter of the inner wall 31 of the housing 3 becomes the interference in shrink fitting. Although details will be described later, only a portion of the inner wall 31 is in close contact with the outer circumferential surface of the stator 1, and the entire inner wall 31 is not in close contact with the outer circumferential surface of the stator 1.

Here, a method for holding the stator 1 in the housing 3 by shrink fitting will be explained. First, the housing 3 is heated to a predetermined temperature. As a result, the housing 3 thermally expands, and the inner diameter of the stator accommodating portion 30, that is, the inner wall 31, increases. Next, the stator 1 is inserted into the stator accommodating portion 30 of the thermally expanded housing 3. Finally, by cooling the housing 3, the housing 3 contracts and the outer circumferential surface of the stator 1 comes into close contact with the inner wall 31 of the housing 3, so that the stator 1 is held in the housing 3.

The rotating electrical machine 100 includes a holding portion 51 that holds the stator 1 by bringing the outer circumferential surface of the stator 1 into close contact with the inner wall 31 of the housing 3, and a gap portion 52 where the outer circumferential surface of the stator 1 and the inner wall 31 do not come into contact with each other. The cavity 52 is provided on a surface where the inner wall 31 of the housing 3 overlaps the connecting portion 33 in the radial direction R, and the holding portion 51 is provided on a surface where the inner wall 31 of the housing 3 does not overlap with the connecting portion 33 in the radial direction R.

FIG. 4 is a conceptual diagram illustrating the configuration of the cavity 52. In FIG. 4, the area indicated by diagonal hatching is the housing 3, and the area indicated by dotted hatching is the stator 1. However, in FIG. 4, the circumferential direction C, which is originally a curve, is shown as a straight line for convenience of drawing. The upper part of FIG. 4 is the outside of the rotating electric machine 100, and the shaft 4 is arranged at the lower part of FIG. A connecting portion 33 or a refrigerant flow path 34 is disposed in the center portion of the housing 3 in the thickness direction. In the holding portion 51, the stator 1 and the housing 3 are in close contact with each other, and in the gap portion 52, the stator 1 and the housing 3 are not in contact with each other.

Although the cavity 52 is shown in FIG. 4 as spanning both the stator 1 and the housing 3, it may exist only in the stator 1 or housing 3 region. For example, the cavity 52 may be formed by recessing only the inner wall 31 of the housing 3, the cavity 52 may be formed by recessing only the outer periphery of the stator 1, or the inner wall 31 of the housing 3 and The void portion 52 may be formed by recessing both outer peripheral portions of the stator 1 .

When the inner wall 31 of the housing 3 is recessed to form the cavity 52, it can be said that the inner wall 31 is larger than the outer diameter of the stator 1 at least in a portion of the position where it overlaps the connecting portion 33 in the radial direction R. When the outer circumference of the stator 1 is recessed to form the cavity 52, it can be said that the outer diameter of the stator 1 is smaller than the inner diameter of the inner wall 31 at least in a portion of the position overlapping the connecting portion 33 in the radial direction R.

The housing 3 includes a plurality of connection parts 33 as shown in FIG. Although it is desirable that the void portions 52 be provided so as to correspond to each of the plurality of connection portions 33, they may be provided only for some of the connection portions 33. Furthermore, each of the plurality of voids 52 may have a different configuration. For example, one cavity 52 may be formed by recessing the inner wall 31 of the housing 3, and another cavity 52 may be formed by recessing the outer periphery of the stator 1.

The effect of providing the gap 52 between the outer circumferential surface of the stator 1 and the inner wall 31 on the surface where the inner wall 31 of the housing 3 and the connecting portion 33 overlap in the radial direction R will be explained. By providing a gap 52 between the inner wall 31 of the housing 3 and the outer circumferential surface of the stator 1, the propagation path of vibrations originating from the stator 1 can be transmitted through the stator 1, the inner wall 31 of the housing 3, the connecting portion 33, and the outer wall 32. Therefore, a phase difference occurs between the vibrations of the inner wall 31 and the outer wall 32 of the housing 3. Since there is a phase difference between the two, the excitation efficiency of the outer wall 32 deteriorates, and the vibration of the outer wall 32, which is a sound radiation surface, is reduced, so that the radiated sound can be reduced.

If the inner wall 31 of the housing 3 and the outer circumferential surface of the stator 1 are in close contact with each other over the entire circumference, the housing 3 can be considered to be a single-layer wall at the connection part 33, and the vibrations of the stator 1 will be directly transmitted to the outer wall 32. , the stator 1 and the housing 3 vibrate together in the same phase. In this case, vibrations and radiated sound are larger than in the configuration of this embodiment.

FIG. 5 is a diagram showing the relationship between the ratio of the contact area between the inner wall 31 of the housing 3 and the outer peripheral surface of the stator 1 and the magnitude of radiated sound. The horizontal axis in FIG. 5 is the ratio of the contact area between the inner wall 31 and the outer peripheral surface of the stator 1 to the area of the inner wall 31 of the housing 3 or the outer peripheral surface of the stator 1. The vertical axis represents the magnitude of the radiated sound when the contact area ratio is 100%, that is, the ratio based on the acoustic power.

When the contact area between the inner wall 31 of the housing 3 and the outer peripheral surface of the stator 1 is reduced from 100% to 80% to 60%, the proportion of acoustic power decreases. However, the lower limit is 40%, and in the case of 25%, which is even smaller, the proportion of acoustic power increases. This phenomenon can be explained as follows. That is, by reducing the contact area, the path difference between the inner wall 31 and the outer wall 32 becomes larger, and the phase difference between the vibration of the inner wall 31 and the vibration of the outer wall 32 becomes larger. When the phase difference between the vibration of the inner wall 31 and the vibration of the outer wall 32 of the housing 3 is 180 degrees, that is, the phase difference is opposite, the vibration of the outer wall 32 that radiates sound is minimized, and the radiated sound is minimized. However, if the phase difference becomes even larger, it exceeds 180 degrees, so it is thought that the vibration will start to increase.

In order to reduce the radiated sound, the inner wall 31 and outer wall 32 of the housing 3 should vibrate in opposite phases, and the path difference between the inner wall 31 and the outer wall 32 is caused by the bending of the housing 3 due to the annular zero-order vibration of the stator 1. It should be half the wavelength of the wave. That is, the connecting portion 33 is provided so that the length from the starting position of the cavity 52 in the inner wall 31 of the housing 3, passing through the connecting portion 33, and reaching the outer wall 32 is half the wavelength of the bending wave. It is preferable to set the interval, the length of the connecting portion 33, and the contact area between the inner wall 31 and the outer peripheral surface of the stator 1.

In FIG. 5, when the contact area between the inner wall 31 of the housing 3 and the outer circumferential surface of the stator 1 is about 40%, the path difference between the inner wall 31 and the outer wall 32 causes a bending wave of the housing 3 due to the annular zero-order vibration of the stator 1. Since it is half the wavelength, the radiated sound is minimized. On the other hand, if the contact area between the inner wall 31 of the housing 3 and the outer circumferential surface of the stator 1 is reduced, the force for suppressing the vibrations of the stator 1 will be weakened, and the vibrations of the stator 1 will tend to increase. In combination with the vibration reduction effect due to the phase difference between the inner wall 31 and outer wall 32 of the housing 3 and the vibration suppressing force of the stator 1, the radiated sound reduction effect due to the contact area between the inner wall 31 and the outer peripheral surface of the stator 1 appears. ing.

6 and 7 are diagrams showing a specific example of forming the cavity 52. FIG. 6 is a diagram showing the structure of the stator 1 that forms the cavity 52. FIG. 7 is a diagram showing the structure of the housing 3 that forms the cavity 52.

The stator 1 shown in FIG. 6 includes a holding forming portion 11 having a larger diameter than the inner diameter of the inner wall 31 of the housing 3, and a gap forming portion 12 having a smaller diameter than the inner diameter of the inner wall 31. When shrink-fitting the stator 1 to the housing 3, the gap 52 in FIG. Can be formed.

The housing 3 shown in FIG. 7 includes a holding forming portion 35 having a smaller diameter than the outer diameter of the stator 1 and a gap forming portion 36 having a larger diameter than the outer diameter of the stator 1. By shrink-fitting the stator 1 to the housing 3 shown in FIG. 7, a gap 52 can be formed. As described above, the void 52 may be formed in either the stator 1 or the housing 3, or may be formed in both the stator 1 and the housing 3. Furthermore, the method for forming the void portion 52 is not limited to the above method, and may have a shape like a notch, or any other shape may be used.

According to the first embodiment described above, the following effects can be obtained.
(1) The rotating electric machine 100 includes a rotor 2, an annular stator 1 facing the rotor 2 with a predetermined gap therebetween, and a housing 3 in which the stator 1 is held. The housing 3 includes an inner wall 31 that holds the inner surface of the housing 3 in the radial direction R, an outer wall 32 that faces the inner wall 31 in the radial direction R, and a connecting portion 33 that connects the inner wall 31 and the outer wall 32. The inner wall 31, the outer wall 32, and the connecting portion 33 form a refrigerant flow path 34 through which a refrigerant can flow. The inner wall 31 has a gap 52 between the stator 1 and a surface that faces the stator 1 and at least partially overlaps the connecting portion 33 in the radial direction. Therefore, a phase difference occurs between the vibrations of the inner wall 31 and the outer wall 32 of the housing 3, which deteriorates the excitation efficiency of the outer wall 32, reducing the vibration of the outer wall 32, which is the sound radiation surface, and reducing the radiated sound. can be reduced. Therefore, the radiated sound of the rotating electric machine can be reduced without increasing the number of parts.

(2) The void portion 52 is provided at a position that overlaps the opening of the plurality of connecting portions 33 of the housing 3 with respect to the opening. Therefore, it is possible to reliably generate a phase difference between the inner wall 31 and the outer wall 32.

(3) The stator 1 is held in the housing 3 by shrink fitting.

(4) The outer diameter of the stator 1 is smaller than the inner diameter of the inner wall 31 at least in a portion of the position overlapping the connecting portion 33 in the radial direction R.

(5) The inner wall 31 is larger than the outer shape of the stator 1 at least in a portion of the position where it overlaps the connecting portion 33 in the radial direction R.

(Modification 1)
In the embodiment described above, the thicknesses of the inner wall 31 and the outer wall 32 were not specified. However, the ratio of the thicknesses of the inner wall 31 and the outer wall 32 may be defined as shown below. Here, the weight of the housing 3 is assumed to be constant, and the relationship between the thickness of the outer wall 32 and the inner wall 31 of the housing 3 will be considered.

First, consider the thickness of the inner wall 31 of the housing 3. The inner wall 31 is in close contact with the outer peripheral surface of the stator 1 at the holding portion 51, and vibrates as one with the stator 1. Generally, aluminum is often used as the material for the housing 3, and its Young's modulus is about three times larger than that of the electromagnetic steel plate used for the stator 1. Therefore, the thickness of the inner wall 31 of the housing 3 has a small effect on vibration when the stator 1 and the inner wall 31 are integrated.

Next, the thickness of the outer wall 32 of the housing 3 will be considered. The outer wall 32 vibrates separately from the stator 1 and the inner wall 31. Therefore, the rotating electric machine 100 has two vibration modes: a vibration mode in which the stator 1 and the inner wall 31 are integrated, and a vibration mode in which the outer wall 32 is vibration mode. In other words, in the graph of frequency and energy intensity, rotating electric machine 100 has two peaks. In this modification, the peak intensity of the vibration mode in which the stator 1 and the inner wall 31 are integrated is called P1, and the peak intensity in the vibration mode of the outer wall 32 is called P2.

Regarding these two peak intensities, when the thickness of the outer wall 32 of the housing 3 is thinner than the thickness of the inner wall 31, the peak P2 of the outer wall 32 is larger than the peak P1 of the stator 1 and the inner wall 31. On the other hand, when the outer wall 32 of the housing 3 is made thicker than the inner wall 31, the outer wall 32 becomes more rigid, the peak P2 of the outer wall 32 becomes smaller, and the vibration of the outer wall 32 that radiates sound becomes smaller. Become. Therefore, the peak P1 of the stator 1 and the inner wall 31 is also reduced, and the radiated sound can be reduced as a whole. Therefore, it is advantageous to make the outer wall 32 thicker than the inner wall 31 in reducing radiated sound.

FIG. 8 is a diagram showing the influence of the ratio of the thickness of the inner wall 31 and the outer wall 32 of the housing 3 on the magnitude of radiated sound. In FIG. 8, the horizontal axis represents the frequency, and the vertical axis represents the radiated sound, that is, the ratio of the magnitude of the acoustic power, which is based on the peak value of the acoustic power in the housing 3 without a gap. Further, the ratio between the thickness of the inner wall 31 and the thickness of the outer wall 32 of the housing 3 shown in the legend of FIG. 8 is expressed as (thickness of the outer wall 32)/(thickness of the inner wall 31). That is, when the ratio is greater than 1, the outer wall 32 is thicker than the inner wall 31. Further, in FIG. 8, conditions other than the thickness of the inner wall 31 and the outer wall 32, such as the radial dimension of the refrigerant flow path 34, are constant.

In the case of the ratio "0.5" shown by the broken line in FIG. 8, the peak P2 of the outer wall 32 appears at the position 62, and the peak P1 of the stator 1 and the inner wall 31 appears at the position 61. In this case, there is a peak around 5350 [Hz] that is larger than that without a gap, and it can be seen that it is not preferable to reduce the thickness of the outer wall 32 as explained above. On the other hand, in the characteristics shown by the dashed-dotted line and the dashed-double-dotted line, the peak is smaller than that without voids. In particular, when the ratio is "2", that is, when the outer wall 32 is twice as thick as the inner wall 31, the peak intensity is less than 0.5, so it is less than half that of the case without voids.

FIG. 9 is a diagram showing the shape of the housing 3 in this modification. In the housing 3 shown in FIG. 9, the outer wall 32 is thicker than the inner wall 31. Since the housing 3 has the shape shown in FIG. 9, the radiated sound emitted by the rotating electric machine 100 can be reduced.

According to this modification 1, the following effects can be obtained.
(6) The outer wall 32 is thicker than the inner wall 31. Therefore, the radiated sound emitted by the rotating electric machine 100 can be further reduced.

(Modification 2)
In the embodiment described above, the gap 52 has the same width as the connection part 33 in the circumferential direction C, and the gap 52 and the connection part 33 entirely overlap in the radial direction R. However, the cavity 52 does not have to be the same as the connection part 33 in the circumferential direction C, and the cavity 52 and the connection part 33 may at least partially overlap in the radial direction R.

FIG. 10 is a diagram showing variations of the cavity 52. In FIG. 10, illustrations of symbols other than the cavity 52 and the connecting portion 33 are omitted for convenience of drawing. As shown in FIG. 10(a), even if the gap 52 has the same width as the connection part 33 in the circumferential direction C, and a part of the gap 52 overlaps a part of the connection part 33 in the radial direction R, good. As shown in FIG. 10(b), the width of the gap 52 in the circumferential direction C may be narrower than that of the connection part 33, and the entire gap 52 may overlap with a part of the connection part 33 in the radial direction R. As shown in FIG. 10C, the width of the gap 52 in the circumferential direction C may be wider than the connection part 33, and a part of the gap 52 may overlap with the entire connection part 33 in the radial direction R.

Each of the embodiments and modifications described above may be combined. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments considered within the technical spirit of the present invention are also included within the scope of the present invention.

1 : Stator 2 : Rotor 3 : Housing 31 : Inner wall 32 : Outer wall 33 : Connection part 34 : Refrigerant flow path 51 : Holding part 52 : Gap part 100 : Rotating electric machine

Claims

rotor and
an annular stator that faces the rotor at a predetermined distance;
a housing in which the stator is held;
The housing includes:
an inner wall that holds the inner surface of the housing in the radial direction;
an outer wall facing the inner wall in the radial direction;
a connection part connecting the inner wall and the outer wall,
The inner wall, the outer wall, and the connection portion form a refrigerant flow path through which a refrigerant can flow;
The inner wall may have a gap between the stator and a surface that faces the stator and that at least partially overlaps with the connection portion in the radial direction.
The rotating electric machine according to claim 1,
The housing includes a plurality of the connection parts,
In the rotating electrical machine, the gap is provided at a position overlapping in the radial direction with respect to all of the plurality of connection parts.
The rotating electric machine according to claim 1,
The stator is a rotating electrical machine in which the stator is held in the housing by shrink fitting.
The rotating electric machine according to claim 1,
In the rotating electric machine, the outer diameter of the stator is smaller than the inner diameter of the inner wall at least in a portion of the position overlapping the connection portion in the radial direction.
The rotating electric machine according to claim 1,
In the rotating electric machine, the inner wall has a larger outer diameter than the stator at least in a portion of the position where the inner wall overlaps with the connecting portion in the radial direction.
The rotating electric machine according to any one of claims 1 to 5,
A rotating electrical machine in which the outer wall is thicker than the inner wall.