Stator for electric motor incorporating a sound-absorbing or structural damping element

Abstract

The invention relates to a stator (5) for an electric motor (1) comprising: - a stator body (50) forming a crown extending along an axis (X) between a front end face (51) and a rear end face (52), said stator body (50) comprising an external peripheral face (53) and an internal peripheral face (54) provided with teeth (55), said teeth (55) delimiting two by two a plurality of notches (56) open towards the inside of the stator body (50); - a plurality of conductor segments (57) inserted at least partially into the notches (56) of the stator body (50);characterized in that the stator body (50) is provided with at least one internal cavity (60), said at least one internal cavity (60) housing at least one acoustic absorbing or structural damping element, said at least one acoustic absorbing or structural damping element being capable of attenuating the vibrations and / or mechanical and / or magnetic noises generated by the stator (5) during its operation within the electric motor (1). Figure 5;

Description

Description Title of the invention: Stator for electric motor incorporating a acoustic absorbing element or structural damping element

[0001] — The invention relates to a stator for an electric motor. The invention relates to also an electric motor comprising such a stator.

[0002] — In general, current electric motors have a fixed rotor of a shaft and a stator that surrounds the rotor. The stator is mounted in a housing that It includes bearings for mounting the shaft in rotation. The rotor includes a body formed by a stack of sheets or pole wheels (claw pole) held under packaged using a suitable fastening system. The rotor body It has internal cavities housing permanent magnets. The stator includes a body consisting of a stack of sheets forming a ring, the inner face is equipped with teeth delimiting, in pairs, a plurality of notches open towards inside the stator body and designed to receive phase windings. These en- Phase bearings pass through the slots in the stator body and form buns. protruding from either side of the stator body. The phase windings can for example, they may consist of a plurality of U-shaped conductor segments, the free ends of two adjacent segments being joined together by welding.

[0003] During their operation, electric motors often generate noises which These noises can be bothersome for people nearby. to be of a mechanical nature and result from shocks or friction between mechanical parts during rotor rotation. They can also be magnetic and be generated by the magnetic forces produced by the currents flowing in the motor electrical. Indeed, these magnetic forces can cause the motor's structure to vibrate. electrical at audible frequencies (from 20 Hz to 20 kHz), and these vibrations are transmitted to the ambient air by the structure, generating noise.

[0004] — In particular, the stator can be subjected under the effect of electromagnetic forces to high-frequency micro-displacements within the audible range of the ear human. These vibrations are then transmitted to the rest of the engine structure electric.

[0005] — To reduce the noise generated by electric motors, one of the The solutions currently being considered involve partially or completely encapsulating the stator. However, this solution has the disadvantage of increasing the volume and the mass of the electric motor. Another possible solution is to reinforce acoustic insulation between the engine compartment and the passenger compartment of the vehicle. However, this solution has the drawback of not reducing the noise emitted. the exterior of the vehicle. One of the aims of the invention is therefore to propose a solution to the problem of noise generated by electric motors as described above, and, in particular, to propose a solution to reduce the noise generated by the stator. To this end, the invention relates to a stator for an electric motor comprising: - a stator body forming a ring extending along an axis between a front end face and a rear end face, said stator body comprising an external peripheral face and an internal peripheral face provided with teeth, said teeth delimiting two by two a plurality of notches open towards the inside of the stator body; - a plurality of conductor segments inserted at least partially into the notches of the stator body; characterized by the fact that the stator body is provided with at least one internal cavity, said at least one internal cavity housing at least one acoustic absorbing or structural damping element, said at least one acoustic absorbing or structural damping element being capable of attenuating the vibrations and / or mechanical and / or magnetic noise generated by the stator during its operation within the electric motor. Thus configured, the stator of the invention makes it possible to reduce the noise generated during its operation due to the presence of an element capable of absorbing mechanical and / or magnetic noise and / or damping vibrations inside an internal cavity of the stator body. The stator of the invention may also include one or more of the following characteristics: - said at least one internal cavity comprises a main segment forming a ring around the axis of the stator body, a first plurality of secondary segments called front extending from the main segment towards the front end face of the stator body and a second plurality of secondary segments called rear extending from the main segment towards the rear end face of the stator body. - each secondary front and rear segment is straight and is oriented obliquely with respect to the main segment. - each secondary front and rear segment is straight and is oriented perpendicular to the main segment. - the front and rear secondary segments form tubular holes having a parallelepiped base. - each secondary segment being defined by a width B, measured according to a orthoradial direction, and a length D, measured along a radial direction. The width B is proportional to the width A of a section formed of a tooth and a notch, as measured along an orthoradial direction, the ratio between the width B and the width A being preferably between 0.25 and 0.75, and the length D is proportional to the distance C separating an inner end edge of a notch from the outer peripheral face of the stator body, as measured along a radial direction, the ratio between the length D and the distance C being preferably between 0.25 and 0.75. - the stator body includes at least one radial opening leading, on one side, to the central segment of said at least one internal cavity and, on the other side, at the level of the external peripheral face of the stator body, said at least one radial opening allowing the injection of a filling material into said at least one internal cavity. - the stator comprises a plurality of through orifices opening, on one side, onto one of the front secondary segments, respectively rear, and, on the other side, at the level of the front end face, respectively rear, said through orifices being configured to allow the passage of air but not the filling material. - the through holes are cylindrical in shape and have a diameter between 0.02 mm and 0.2 mm. - said at least one acoustic absorbing or structural damping element has a shape complementary to that of said at least one internal cavity. - said at least one acoustic absorbing or structural damping element is made of a material chosen from a silicone material, a thermo-plastic elastomer, and a heavy mass. The invention also relates to an electric motor comprising a stator as defined above. The invention will be better understood upon reading the following non-limiting description, made with reference to the figures attached hereto. [Fig.1] is a perspective view of an electric motor incorporating a stator according to the invention. [Fig.2] is a cross-sectional view of the engine shown in [Fig.1]. [Fig.3] is a perspective view of the stator equipping the engine of [Fig.1]. [Fig.4] is a front axial view of the stator of [Fig.3]. [Fig.5] is a cross-sectional view of the stator body of [Fig.3] according to the section plane P. [Fig.6] is a perspective view of the stator body of [Fig.3] according to a first variant embodiment, an external peripheral layer of the body having been removed so as to reveal the internal cavity. [Fig.7] is a top view of the stator shown in [Fig.6]. [Fig.8] is a perspective view of the stator body of [Fig.3] according to a second embodiment variant, an external peripheral layer of the body having been removed so as to reveal the internal cavity. [Fig.9] is a top view of the stator shown in [Fig.8]. [Fig.10] is a front axial view of a structural detail of the stator body of [Fig.3]. Throughout the description and in the claims, the terms "axial" and "radial" and their derivatives are defined with respect to the longitudinal axis along which the stator extends and which passes through the center of the stator. Thus, an axial orientation refers to an orientation parallel to the longitudinal axis of the stator, and a radial orientation refers to an orientation perpendicular to the longitudinal axis of the stator. Furthermore, by convention, the terms "front" and "rear" refer to separate positions along the longitudinal axis of the stator. In particular, the term "front" corresponds to the parts of the stator adjacent to the end of the rotor shaft on which a pulley, pinion, or spline can be fixed for transmitting the rotational motion of the rotor to any other similar motion transmission device.The term "rear" therefore refers to the parts of the stator that are adjacent to the other end of the rotor shaft. With reference to [Fig. 1], an electric motor is shown incorporating a stator according to the invention. This electric motor 1 comprises, in particular, a two-part housing 2 containing the rotor 3, which is fixed to a shaft 4 rotatably mounted about an axis X, and an annular stator 5 that surrounds the rotor 3 coaxially with the shaft 4. The housing 2 consists, in particular, of a front bearing 24 and a rear bearing 25 connected to each other by means of fixing screws 23. The bearings 24 and 25 are hollow and each centrally carries a ball bearing 21 and 22, respectively, for the rotational mounting of the shaft 4. The rear bearing 25 consists of a bell-shaped cover which, in the mounted position of the engine shown in [Fig.2], completely covers a cylindrical part 242 of the front bearing 24 which extends axially from an end face 241 of said front bearing 24, said face 241 having the form of a disk aligned in a plane perpendicular to the axis X of the shaft 4. The rear bearing 25 rests at an end edge 251 on a shoulder 243 defined by the end face 241. The rear bearing 25 has a shape substantially complementary to that of the cylindrical portion 242 of the front bearing 24, so that, in the mounted position of the engine, this portion 242 is in a sealed contact with the inner wall 252 of the rear bearing 25. The seal is ensured by two annular seals 8 housed within two annular grooves 7 formed on the periphery of the portion 242. The grooves 7 are arranged on either side of a smaller area 244. The thickness of part 242. Zone 244 forms an internal fluid circulation channel 9 with the inner wall 252 of the rear bearing 25. This channel 9 allows the circulation of a coolant, such as water, glycol, or oil, around the cylindrical part 242 of the front bearing 24. Thus, during the operation of the motor 1, the heat released by the stator 5 and transmitted to the front bearing 24 can be directly transferred to the coolant circulating in the internal channel 9. This results in faster cooling of the stator 5. The heat transfer to the coolant is further improved if the front bearing 24 is made of a material with high thermal conductivity, such as aluminum, and the rear bearing 25 is made of a material with low thermal conductivity, such as plastic.The coolant supply will be via a liquid inlet tube 26 formed at the periphery of the rear bearing 25, said inlet tube 26 opening into the internal channel 9. The coolant outlet will be via a liquid outlet tube 27 formed at the periphery of the rear bearing 25, said outlet tube 27 also opening into the internal channel 9. With reference to Figures 3 and 4, the stator 5 equipping the motor of Figures 1 and 2 is shown. This stator 5 comprises a ring-shaped body 50 extending along the X-axis between a front end face 51 and a rear end face 52. The body 50 is made up of a stack of laminations held together by means of a suitable fastening system. The body 50 has a substantially cylindrical outer peripheral face 53 and an inner peripheral face 54 provided with teeth 55 extending parallel to the axial direction X and regularly spaced around the circumference of the body 50. The teeth 55 define, in pairs, a plurality of notches 56 intended to house at least partially a plurality of U-shaped conductor segments 57. Thus, two successive notches 56 are separated by a tooth 55 as shown in [Fig. 5].The notches 56 open axially onto the front and rear end faces 51, 52 of the stator body 50 and radially onto the inner peripheral face 54 of the body 50. As shown in [Fig. 5], the body 50 is also provided with several radial openings 58 on its outer peripheral face 53. These radial openings 58 lead into an internal cavity 60 formed inside the stator body 50. These radial openings 58 will thus allow the injection of a filler material (not shown) into the internal cavity 60. The filler material will have specific characteristics that make it particularly suitable for attenuating the vibrations and / or mechanical and / or magnetic noise generated by the stator during its operation within the electric motor. It can therefore be advantageously chosen from a silicone material, a thermoplastic elastomer (for example) example of the Hytrel® type or the PP / EPDM type), and a heavy mass. Once the injection operation is complete, this filling material will form a sound-absorbing or structural damping element that will completely fill the internal cavity 60. This sound-absorbing or structural damping element will therefore have a shape complementary to that of the internal cavity 60. The sound attenuation effect obtained by means of this sound-absorbing or structural damping element will therefore depend on the shape of the internal cavity 60. Two preferred internal cavity shapes are shown in Figures 6-7 and 8-9, respectively. These preferred shapes are not limiting to the invention. Any other internal cavity shape that effectively reduces the noise generated by the stator may be considered. In particular, it may be possible to equip the stator with several separate internal cavities, each cavity housing a specific acoustic absorbing or structural damping element. With reference to Figures 6 and 7, a first embodiment of a stator body according to the invention is shown. In this embodiment, the internal cavity 60 comprises a main segment 61, forming a ring around the X axis of the stator body 50, and several secondary segments 62a, 62b extending from said main segment 61 towards the end faces 51, 52 of the stator body 50, respectively secondary segments 62a, referred to as front, extending from the main segment 61 towards the front end face 51 and secondary segments 62b, referred to as rear, extending from the main segment 61 towards the rear end face 52. Each front and rear secondary segment 62a, 62b is straight and is oriented obliquely with respect to the main segment 61. In the configuration shown in [Fig.7], the front secondary segments 62a are parallel to the same direction D1 and the rear secondary segments 62b are parallel to the same direction D2, the direction D1 forming an angle α with the direction D2. This angle α will preferably be between 30° and 120°. In the configuration shown in [Fig. 6], the front and rear secondary segments 62a, 62b have a tubular shape with a parallelepiped base. As illustrated in [Fig. 10], these secondary segments 62a, 62b will be defined by a width B, measured in an orthoradial direction, and a length D, measured in a radial direction. The width B may be proportional to the width A of a section formed by a tooth 55 and a notch 56, as measured in an orthoradial direction. In particular, the ratio between the width B and the width A may be between 0.25 and 0.75. Similarly, the length D may be proportional to the distance C separating the inner end edge of a notch 56 from the outer peripheral wall 53 of the stator body 50, as measured in an orthoradial direction. radial direction. In particular, the ratio between the length D and the distance C may be between 0.25 and 0.75. According to other configurations of the invention (not shown), the secondary segments may also have a tubular shape with a circular base. As shown in [Fig. 6], the stator body 50 is also provided with a plurality of first and second through-holes 59a and 59b. Each of the first through-holes 59a opens, on one side, into one of the front secondary segments 62a and, on the other side, into the front end face 51 and each of the second through-holes 59b opens, on one side, into one of the rear secondary segments 62b and, on the other side, into the rear end face 52. Said first and second through-holes 59a, 59b will serve as vents during the operation of injecting the filling material into the internal cavity 60, thus preventing the formation of air pockets inside the stator body. The through-holes 59a, 59b must therefore be wide enough to allow air to pass through but narrow enough to prevent the passage of the filling material. With reference to Figures 8 and 9, a second embodiment of a stator body according to the invention is shown. This embodiment differs from that of Figures 6 and 7 in that each front and rear secondary segment 62a, 62b is oriented perpendicularly to the main segment 61. In the configuration shown in [Fig. 8], the front and rear secondary segments 62a, 62b have a tubular shape with a parallelepiped base. As illustrated in [Fig. 10], these secondary segments 62a, 62b are defined by a width B, measured in an orthoradial direction, and a length D, measured in a radial direction. The width B can be proportional to the width A of a section formed by a tooth 55 and a notch 56, as measured in an orthoradial direction. In particular, the ratio between the width B and the width A can be between 0.25 and 0.75. Similarly, the length D can be proportional to the distance C separating the inner end edge of a notch 56 from the outer peripheral wall 53 of the stator body 50, as measured in a radial direction. In particular, the ratio between length D and distance C may be between 0.25 and 0.75. According to other configurations of the invention (not shown), the secondary segments may also have a tubular shape with a circular base. As shown in [Fig. 8], the stator body 50 is also provided with a plurality of first and second through-holes 59a and 59b. Each of the first through-holes 59a opens, on one side, onto one of the front secondary segments 62a and, on the other side, onto the front end face 51, and each of the second through-holes 59b opens, on one side, onto one of the se- secondary rear ports 62b and, on the other side, at the rear end face 52. These first and second through-holes 59a, 59b will serve as degassing vents during the injection of the filler material into the internal cavity 60, thus preventing the formation of air pockets inside the stator body. The through-holes 59a, 59b must therefore be wide enough to allow air to pass through but narrow enough to prevent the passage of the filler material. In particular, the through-holes 59a, 59b may be cylindrical in shape and have a diameter between 0.02 mm and 0.2 mm.

Claims

Claims

1. Stator (5) for electric motor (1) comprising: - a stator body (50) forming a crown extending along a axis (X) between a front end face (51) and an end face rear (52), said stator body (50) having a peripheral face external (53) and an internal peripheral face (54) provided with teeth (55), said teeth (55) delimiting two by two a plurality of notches (56) open towards the inside of the stator body (50); - a plurality of conductor segments (57) inserted at least par- partially in the notches (56) of the stator body (50); characterized in that the stator body (50) is provided with at least one internal cavity (60), said at least one internal cavity (60) housing at least at least one acoustic absorbing or structural damping element, said at least one sound-absorbing or damping element structural being able to attenuate vibrations and / or mechanical noise and / or magnetic generated by the stator (5) during its operation within the electric motor (1).

2. Stator (5) according to claim 1, characterized in that said at least an internal cavity (60) comprises a main segment (61) forming a ring around the axis (X) of the stator body (50), a first plurality of secondary segments called front segments (62a) extending from the main segment (61) towards the front end face (51) of the stator body (50) and a second plurality of secondary segments said rear (62b) extending from the main segment (61) in direction of the rear end face (52) of the stator body (50).

3. Stator (5) according to claim 2, characterized in that each segment front and rear secondary (62a, 62b) is straight and is oriented obliquely to the main segment (61).

4. Stator (5) according to claim 2, characterized in that each segment secondary front and rear (62a, 62b) is rectilinear and is oriented perpen- dicularly to the main segment (61).

5. Stator (5) according to one of claims 2 to 4, characterized in that the front and rear secondary segments (62a, 62b) form tu- holes bulbous with a parallelepiped base.

6. Stator (5) according to claim 5, characterized in that, each secondary segment (62a, 62b) being defined by a width B, measured in an orthoradial direction, and a length D, measured in a radial direction. the width B is proportional to the width A of a section formed of a tooth (55) and a notch (56), as measured in an orthoradial direction, the ratio between the width B and the width A being preferably between 0.25 and 0.75, and the length D is proportional to the distance C separating an edge internal end of a notch (56) of the external peripheral face (53) of the stator body (50), as measured in one direction radial, the ratio between the length D and the distance C being preferentially- typically between 0.25 and 0.

75.

7. Stator (5) according to one of claims 2 to 6, characterized in that the stator body (50) comprises at least one radial opening (58) de- closing, on one side, on the central segment (61) of said at least one internal cavity (60) and, on the other side, at the level of the peripheral face external (53) of the stator body (50), said at least one opening radial (58) allowing the injection of a filling material to the interior of said at least one internal cavity (60).

8. Stator (5) according to claim 7, characterized in that it comprises a plurality of through orifices (59a, 59b) opening, on one side, onto one secondary segments front (62a), respectively rear (62b), and, on the other side, at the level of the front end face (51), resp- tively rear (52), said through holes (59a, 59b) being configured to allow air to pass through but not the filling material.

9. Stator (5) according to claim 8, characterized in that the orifices tra- slopes (59a, 59b) are cylindrical in shape and have a diameter between 0.02 mm and 0.2 mm.

10. Stator (5) according to one of the preceding claims, characterized in that that said at least one sound-absorbing or damping element structural has a shape complementary to that of said at least one an internal cavity (60).

11. Stator (5) according to one of the preceding claims, characterized in that that said at least one sound-absorbing or damping element structural is made of a material chosen from a silicone material, a thermoplastic elastomer, and a heavy mass.

12. Electric motor (1) comprising a stator (5) according to one of the claims- previous instructions.