Stator for electric motor

Abstract

The invention relates to a stator (5) for an electric motor (1), comprising: - a stator body (50) forming a ring extending along an axis (X) between a front end face (51) and a rear end face (52), the stator body (50) comprising an outer peripheral face (53) and an inner peripheral face (54) provided with teeth (55), the teeth (55) defining, in pairs, 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); characterised in that the stator body (50) is provided with at least one internal cavity (60), the at least one internal cavity (60) housing at least one sound-absorbing or structural damping element, the at least one sound-absorbing or structural damping element being able to attenuate the vibrations and / or mechanical and / or magnetic noises generated by the stator (5) during its operation within the electric motor (1).

Description

[0001] STATOR FOR ELECTRIC MOTOR

[0002] The invention relates to a stator for an electric motor. The invention also relates to an electric motor comprising such a stator.

[0003] Generally speaking, current electric motors comprise a rotor secured to a shaft and a stator which surrounds the rotor. The stator is mounted in a casing which comprises bearings for the rotational mounting of the shaft. The rotor comprises a body formed by a stack of laminations or claw poles held in the form of a packet by means of a suitable fastening system. The rotor body comprises internal cavities housing permanent magnets. The stator comprises a body constituted by a stack of laminations forming a crown, the inner face of which is provided with teeth delimiting two by two a plurality of notches open towards the interior of the stator body and intended to receive phase windings. These phase windings pass through the notches of the stator body and form buns projecting on either side of the stator body.The phase windings may, for example, consist of a plurality of U-shaped conductor segments, the free ends of two adjacent segments being connected together by welding.

[0004] During operation, electric motors often generate noise that can be annoying to people nearby. These noises can be mechanical and result from shocks or friction between mechanical parts during the rotation of the rotor. They can also be magnetic and be generated by the magnetic forces produced by the currents flowing in the electric motor. Indeed, these magnetic forces can cause the structure of the electric motor to vibrate at audible frequencies (from 20 Hz to 20 kHz), and these vibrations are transmitted to the ambient air by the structure, generating noise.

[0005] In particular, the stator can be subjected to high-frequency micro-displacements in the audible range of the human ear under the effect of electromagnetic forces. These vibrations are then transmitted to the rest of the structure of the electric motor.

[0006] To reduce the noise generated by electric motors, one of the solutions currently being considered is to partially or completely encapsulate the stator. However, this solution has the disadvantage of increasing the volume and mass of the electric motor. Another possible solution is to improve the sound insulation between the engine compartment and the vehicle's interior. However, this solution has the disadvantage of not reducing the noise transmitted outside the vehicle.

[0007] One of the aims of the invention is therefore to propose a solution to the problem of noise pollution generated by electric motors as described above, and, in particular, to propose a solution making it possible to reduce the noise generated by the stator. To this end, the invention relates to a stator for an electric motor comprising:

[0008] - a stator body forming a crown 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;

[0009] - a plurality of conductor segments inserted at least partially into the notches of the stator body; characterized in 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.

[0010] 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.

[0011] The stator of the invention may also include one or more of the following characteristics:

[0012] - 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 segments extending from the main segment towards the front end face of the stator body and a second plurality of secondary segments called rear segments extending from the main segment towards the rear end face of the stator body.

[0013] - each front and rear secondary segment is straight and is oriented obliquely relative to the main segment.

[0014] - each front and rear secondary segment is straight and is oriented perpendicular to the main segment.

[0015] - the front and rear secondary segments form tubular holes with a parallelepiped base.

[0016] - each secondary segment 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 by a tooth and a notch, 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 internal end edge of a notch from the external peripheral face of the stator body, as measured in a radial direction, the ratio between the length D and the distance C being preferably between 0.25 and 0.75.

[0017] - the stator body comprises at least one radial opening opening, on one side, onto 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 inside said at least one internal cavity.

[0018] - the stator comprises a plurality of through-orifices opening, on one side, onto one of the front, respectively rear, secondary segments, and, on the other side, at the level of the front, respectively rear, end face, said through-orifices being configured to allow air to pass through but not the filling material.

[0019] - the through holes are cylindrical in shape and have a diameter between 0.02 mm and 0.2 mm.

[0020] - said at least one acoustic absorbing or structural damping element has a shape complementary to that of said at least one internal cavity.

[0021] - said at least one acoustic absorbing or structural damping element is made of a material chosen from a silicone material, a thermoplastic elastomer, and a heavy mass.

[0022] The invention also relates to an electric motor comprising a stator as defined above.

[0023] The invention will be better understood upon reading the non-limiting description which follows, given with reference to the attached figures.

[0024] [Fig. 1] is a perspective view of an electric motor incorporating a stator according to the invention.

[0025] [Fig. 2] is a cross-sectional view of the engine shown in Fig. 1.

[0026] [Fig. 3] is a perspective view of the stator equipping the motor of Figure 1.

[0027] [Fig. 4] is a front axial view of the stator of Figure 3.

[0028] [Fig. 5] is a sectional view of the stator body of Figure 3 along the section plane P.

[0029] [Fig. 6] is a perspective view of the stator body of Figure 3 according to a first variant embodiment, an external peripheral layer of the body having been removed so as to reveal the internal cavity.

[0030] [Fig. 7] is a top view of the stator shown in Fig. 6.

[0031] [Fig. 8] is a perspective view of the stator body of Figure 3 according to a second alternative embodiment, 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 Figure 8.

[0032] [Fig. 10] is a front axial view of a structural detail of the stator body of Figure 3.

[0033] 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 which adjoin the end of the rotor shaft on which a pulley, a pinion, a spline intended to transmit the rotational movement of the rotor to any other similar motion transmission device can be fixed.The term "rear" therefore refers to the parts of the stator which adjoin the other end of the rotor shaft.

[0034] With reference to Figure 1, there is shown an electric motor 1 implementing a stator according to the invention. This electric motor 1 comprises in particular a casing 2 in two parts housing the rotor 3 integral in rotation with a shaft 4 mounted rotatably around an axis X and an annular stator 5 which surrounds the rotor 3 coaxially with the shaft 4. The casing 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, 25 are hollow in shape and each centrally carry a ball bearing respectively 21 and 22 for the rotational mounting of the shaft 4.

[0035] The rear bearing 25 consists of a bell-shaped cover which, in the mounted position of the engine shown in Figure 2, completely covers a cylindrical portion

[0036] 242 of the front bearing 24 which extends axially from an end face 241 of said front bearing 24, said face 241 having the shape of a disc 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

[0037] 243 defined by the end face 241.

[0038] The rear bearing 25 has a shape substantially complementary to that of the cylindrical part 242 of the front bearing 24 so that, in the mounted position of the engine, this part 242 is in sealed contact with the internal wall 252 of the rear bearing 25, the seal being ensured by two annular-shaped seals 8 which are housed inside two annular grooves 7 formed at the periphery of the part 242. The grooves 7 are arranged on either side of a zone 244 of smaller thickness of the part 242. The zone 244 forms with the internal wall 252 of the rear bearing 25 an internal channel 9 for the circulation of liquid. The channel 9 thus allows the circulation of a cooling liquid, such as for example water, glycol or an oil, around the cylindrical part 242 of the front bearing 24.Thus, during operation of the engine 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. Faster cooling of the stator 5 can thus be obtained. The heat transfer to the coolant is further improved in the case where the front bearing 24 is made of a material having high thermal conductivity, such as aluminum for example, and the rear bearing 25 is made of a material with low thermal conductivity, such as a plastic material for example. The coolant will be supplied through a liquid inlet pipe 26 formed at the periphery of the rear bearing 25, said inlet pipe 26 opening into the internal channel 9.The coolant will exit through a liquid outlet pipe 27 formed at the periphery of the rear bearing 25, said outlet pipe 27 also opening into the internal channel 9.

[0039] 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 crown-shaped body 50 extending along the axis X between a front end face 51 and a rear end face 52. The body 50 is constituted by a stack of sheets held in the form of a packet by means of a suitable fastening system. The body 50 comprises a substantially cylindrical external peripheral face 53 and an internal 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 delimit two by two a plurality of notches 56 intended to at least partially house a plurality of U-shaped conductor segments 57. Thus, two successive notches 56 are separated by a tooth 55 as shown in Figure 5.The notches 56 open axially onto the front and rear end faces 51, 52 of the stator body 50 and radially onto the internal peripheral face 54 of the body 50.

[0040] As shown in Figure 5, the body 50 is also provided with several radial openings 58 on its external peripheral face 53. These radial openings 58 open into an internal cavity 60 formed inside the stator body 50. These radial openings 58 will thus make it possible to inject a filling material (not shown) inside the internal cavity 60. The filling material will in particular have specific characteristics making 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 may thus be advantageously chosen from a silicone material, a thermoplastic elastomer (for example of the Hytrel® type or of the PP / EPDM type), and a heavy mass.

[0041] Once the injection operation is complete, this filling material will form a sound-absorbing or structural damping element which 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-attenuating effect obtained by means of this sound-absorbing or structural damping element will therefore depend on the shape of the internal cavity 60.

[0042] Two preferred forms of internal cavity have been shown respectively in Figures 6-7 and 8-9. These preferred forms are obviously not limiting for the invention. Any other form of internal cavity making it possible to effectively reduce the noise generated by the stator may be envisaged at this level. In particular, it may be possible to provide the stator with several internal cavities separated from each other, each internal cavity housing a specific acoustic absorbing or structural damping element.

[0043] 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 axis X 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, called front, extending from the main segment 61 towards the front end face 51 and secondary segments 62b, called rear, extending from the main segment 61 towards the rear end face 52. Each front and rear secondary segment 62a, 62b is rectilinear and is oriented obliquely relative to the main segment 61.In the configuration shown in Figure 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 a with the direction D2. This angle a will preferably be between 30° and 120°.

[0044] In the configuration shown in Figure 6, the front and rear secondary segments 62a, 62b have a tubular shape with a parallelepiped base. As illustrated in Figure 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 a radial direction. In particular, the ratio between the length D and the distance C may be between 0.25 and 0.75.

[0045] 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-orifices 59a opens, on one side, onto one of the front secondary segments 62a and, on the other side, at the front end face 51 and each of the second through-orifices 59b opens, on one side, onto one of the rear secondary segments 62b and, on the other side, at the rear end face 52. Said first and second through-orifices 59a, 59b will serve as vents during the operation of injecting the filling material inside the internal cavity 60, thus preventing the formation of an air pocket 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 filling material from passing through.

[0046] Referring 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 perpendicular to the main segment 61.

[0047] In the configuration shown in Figure 8, the front and rear secondary segments 62a, 62b have a tubular shape with a parallelepiped base. As illustrated in Figure 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 a radial direction. In particular, the ratio between the length D and the distance C may be between 0.25 and 0.75.

[0048] According to other configurations of the invention (not shown), the secondary segments may also have a tubular shape with a circular base.

[0049] As shown in Figure 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, at the front end face 51 and each of the second through-holes 59b opens, on one side, onto one of the rear secondary segments 62b and, on the other side, at the rear end face 52. Said first and second through-holes 59a, 59b will serve as degassing vents during the operation of injecting the filling material inside the internal cavity 60, thus preventing the formation of an air pocket 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 filling material from passing through.In particular, the through-orifices 59a, 59b may be cylindrical in shape and have a diameter of 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 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).

2. Stator (5) according to claim 1, characterized in that said at least one 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 called rear segments (62b) extending from the main segment (61) towards the rear end face (52) of the stator body (50).

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

4. Stator (5) according to claim 2, characterized in that each front and rear secondary segment (62a, 62b) is rectilinear and is oriented perpendicular 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 tubular holes having 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 by 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 internal end edge of a notch (56) from the external peripheral face (53) of the stator body (50), as measured in a radial direction, the ratio between the length D and the distance C being preferably 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) opening, on one side, onto the central segment (61) of said at least one internal cavity (60) and, on the other side, at the level of the external peripheral face (53) of the stator body (50), said at least one radial opening (58) allowing the injection of a filling material inside 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 of the front (62a), respectively rear (62b) secondary segments, and, on the other side, at the level of the front (51), respectively rear (52) end face, said through-orifices (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 through-orifices (59a, 59b) are cylindrical in shape and have a diameter of between 0.02 mm and 0.2 mm.

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

11. Stator (5) according to one of the preceding claims, characterized in that said at least one acoustic absorbing or structural damping element 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 preceding claims.

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