Noise-reducing electric motor, especially for railway vehicles

Abstract

Noise-reducing electric motor, in particular for a railway vehicle. The electric motor (10) comprises a stator (16) and a rotor (12), a fan (17) driven in rotation by the rotor (12), and a fixed flange (18) defining at least one air inlet opening (24). Closing means (28) are movable between a first position for releasing each opening (24) and a second position for closing each opening (24). Elastic return means (34) return the closing means (28) to the release position, the closing means (28) being driven to the closing position under the effect of a centrifugal force induced by the moving rotor (12). Figure for the abstract: Figure 2

Description

Title of the invention: Noise-reducing electric motor, particularly for railway vehicles

[0001] The present invention relates to an electric motor, in particular for a railway vehicle.

[0002] An electric motor comprising a rotor and a stator is already known in the state of the art. For reasons of cooling the electric motor, an air passage is usually defined between the rotor and the stator, and the rotor carries a fan driving the air circulating in the air passage.

[0003] The present invention aims in particular to improve such an electric motor, in particular by reducing the noise emitted by this electric motor at high speed.

[0004] For this purpose, the invention relates in particular to an electric motor comprising a stator and a rotor rotatable about an axis of rotation, at least one air passage being defined between the rotor and the stator, and comprising a fan driven in rotation by the rotor, and a fixed flange defining at least one air inlet opening communicating with the air passage, characterized in that the electric motor comprises means for closing each air inlet opening, movable between a first position for releasing each opening and a second position for closing each opening, and means for elastically returning the closing means to the release position, the closing means being driven to the closing position under the effect of a centrifugal force induced by the moving rotor.

[0005] The inventors have found that the noise level at high speed is mainly due to ventilation. The present invention therefore proposes to close the air inlet opening supplying the rotor at high speed.

[0006] Due to the use of the traction motor, this reduction in airflow is not harmful at high speeds, because the torque density at this speed is low.

[0007] The invention provides for a closure of the air inlet opening under the effect of centrifugal force, in order to ensure automatic closure at high speed.

[0008] An electric motor according to the invention may further comprise one or more of the following characteristics, taken alone or in any technically conceivable combination.

[0009] - The sealing means comprise at least one flap sized to cover at least one of the air inlet openings in the closed position.

[0010] - Each flap has a shape extending in an arc of a circle defined around the axis of rotation.

[0011] - The elastic return means comprise, for each flap, at least one spring, extending radially between a hub connected to the rotor and the corresponding flap.

[0012] - The stiffness of each spring is chosen so that the corresponding flap covers the or the corresponding openings when the rotor rotation speed exceeds a predefined threshold.

[0013] - The predefined threshold is substantially equal to half the maximum rotor speed.

[0014] - The electric motor has end stops limiting the movement shutters, each shutter coming into contact with a corresponding one of the stops in the closed position.

[0015] - The closure position is defined by the maximum length of the return means elastics.

[0016] The invention also relates to a railway vehicle, characterized in that it comprises an electric motor as defined previously.

[0017] Various aspects and advantages of the invention will be highlighted in the following description, given solely by way of example and with reference to the appended figures, among which:

[0018] [Fig-1] [Fig. 1] is a partial longitudinal sectional view of an electric motor according to an exemplary embodiment of the invention, in a first configuration;

[0019] [Fig.2] [Fig.2] is a view, in a sectional plane of [Fig.l], of the engine electric of [Fig.l];

[0020] [Fig.3] [Fig.3] is a view similar to [Fig.l] of the electric motor in a second configuration;

[0021] [Fig.4] [Fig.4] is a view similar to [Fig.2] of the engine of [Fig.3];

[0022] [Fig.5] [Fig.5] is a view similar to [Fig.l] of the electric motor in a third configuration;

[0023] [Fig.6] [Fig.6] is a view similar to [Fig.2] of the engine of [Fig.5].

[0024] The figures show an electric motor 10, for example intended to equip a railway vehicle.

[0025] The electric motor 10 comprises, in a conventional manner, a rotor 12 secured to a shaft 14 movable in rotation around a longitudinal axis X. The electric motor 10 also comprises, in a conventional manner, a stator 16.

[0026] The electric motor 10 also comprises a fan 17, kinetically connected to the rotor 12 so as to be driven in rotation by the latter.

[0027] The fan 17 is intended to drive an air flow, in particular in a first circumferential air passage 20 defined between the stator 16 and the rotor 12. Optionally, the rotor 12 also comprises at least one second air passage 22.

[0028] The electric motor 10 comprises a fixed flange 18. The flange 18 defines at least an air inlet opening 24 communicating with the first air passage 20 and each second air passage 22. In the example described, the flange 18 defines a plurality of openings 24 (in particular eight openings 24). Thus, in the remainder of the description, the at least one opening 24 will be designated by the terms “the openings 24”. However, the case where the flange 18 would only have a single opening 24 is not excluded.

[0029] It will be noted that the stator 16 also advantageously comprises at least one third air passage 26.

[0030] It appears that part of the noise generated by the electric motor 10 is due to the air entering through the air inlet openings 24. This part of the noise is predominant at high engine speed.

[0031] Figures 1 and 2 show the electric motor 10 at a standstill, Figures 3 and 4 show the electric motor at medium speed, and Figures 5 and 6 show the electric motor at high speed.

[0032] In the present description, the electric motor is considered to be at high speed when the rotational speed of the rotor 12 is greater than half of its maximum speed. The motor is at low speed or medium speed when the rotational speed of the rotor 12 is less than half of its maximum rotational speed.

[0033] In order to reduce the noise linked to the air entering the air inlet openings 24, the electric motor 10 comprises means 28 for closing the air inlet openings 24. The closing means 28 are shown in more detail in FIGS. 2, 4 and 6.

[0034] The closing means 28 comprise at least one flap 30, movable between a first position for clearing the openings 24, and a second position for closing at least one of the openings 24.

[0035] Each flap 30 is sized to cover at least one of the openings 24 in the closed position.

[0036] In the example described, the closure means 28 comprise four flaps 30, each being sized to cover two openings 24 in the closure position. Thus, in the description which follows, corresponding to a particular embodiment, the flaps 30 will be designated in the plural, without this excluding the embodiments with a single flap.

[0037] Each flap 30 has, for example, a shape in an arc of a circle defined around the axis of rotation X. Each flap 30 has a dimension, in a radial direction perpendicular to the axis of rotation X, greater than or equal to the dimension, in the same direction, of each opening 24 that it is intended to cover.

[0038] Optionally, the fan 17 comprises rails 32 for guiding the flaps 30. These rails 32 ensure the correct alignment of the flaps 30 when they are removed. placements between the release and closure positions. The rails 32 preferably extend radially from the axis of rotation X.

[0039] Advantageously, the rails 32 are formed from materials with a low coefficient of friction, so as not to oppose significant resistance to the movement of the flaps 30.

[0040] The closure means 28 also comprise means 34 for elastically returning the flaps 30 to their disengaged position. The elastic return means 34 comprise, for example, a spring 36 for each flap 30. Each spring 36 thus extends radially from the axis of rotation X, between a hub 38 connected to the shaft 14 and the corresponding flap 30.

[0041] The closing means 28 are driven towards the closing position under the effect of the centrifugal force induced by the moving shaft 14.

[0042] The stiffness of the springs 36 is chosen so that the centrifugal force is sufficiently high relative to the restoring force of the springs so that the flaps 30 cover the corresponding openings 24 when the rotational speed of the shaft 14 is greater than a predetermined threshold. The predetermined threshold corresponds, for example, to half the maximum speed of the rotor 12. Those skilled in the art will easily be able to determine the desired spring stiffness using simple force calculations.

[0043] Figures 3 and 4 show an intermediate position of the flaps 30, when the engine is operating at medium speed, with a rotor rotation speed lower than said threshold. It can thus be seen that the openings 24 are progressively covered as a function of the centrifugal force, and therefore the rotation speed of the rotor 12.

[0044] When the rotation speed of the shaft 14 is greater than said predetermined threshold, the flaps 30, due to the centrifugal force, completely cover the openings 24 as shown in FIGS. 5 and 6. More particularly, the flaps 30 being in rotation around the axis of rotation X, the flaps 30 are dimensioned so that the openings 24 are closed substantially at each instant by the flaps 30 which come to cover them one after the other.

[0045] Advantageously, the motor 10 comprises end-of-travel stops 40, against which the flaps 30 come into contact in the closed position, as shown in [Fig. 6]. Alternatively, the movement of the flaps 30 is limited by the maximum length of the springs 36.

[0046] In this case, the air no longer rushes into the openings 24, thus eliminating the noise linked to this rush of air. This allows, in the example shown, a noise reduction of approximately 5 dB.

[0047] Due to the use of the traction motor, this does not involve problems of overheating of the motor. Indeed, the traction motor, at high speed, is not thermally stressed due to the low torque density required at this operating speed. operation and high level of ventilation.

[0048] Due to the elastic return force, when the rotation speed of the shaft 14 decreases, and therefore the centrifugal force decreases, the flaps 30 are returned to the release position, progressively uncovering the openings 24 as a function of the speed.

[0049] It thus appears that the openings 24 are cleared, partially closed or completely closed, automatically, depending on the speed of rotation of the shaft 14.

[0050] Thus, the electric motor 10 operates as an open motor at low or medium speed (from zero speed up to said predetermined threshold, in particular up to a speed substantially equal to half the maximum speed), and as a closed motor at high speed (for a speed greater than said predefined threshold, for example a speed greater than half the maximum speed).

[0051] It will be noted that operation with a closed engine also makes it possible to reduce pollution on the rotor since the air, carrying pollution, no longer circulates around the rotor when the flaps 30 are in the closed position.

[0052] It should be noted that the invention is not limited to the embodiment previously described, but could have various variants without departing from the scope of the claims.

Claims

Claims

1. Electric motor (10), comprising a stator (16) and a rotor (12) rotatable about an axis of rotation (X), at least one air passage (20) being defined between the rotor (12) and the stator (16), and comprising a fan (17) driven in rotation by the rotor (12), and a fixed flange (18) defining at least one air inlet opening (24) communicating with the air passage (20), characterized in that the electric motor (10) comprises means (28) for closing each air inlet opening (24), movable between a first position for releasing each opening (24) and a second position for closing each opening (24), and means (34) for elastically returning the closing means (28) to the release position, the closing means (28) being driven to the position of obturation under the effect of a centrifugal force induced by the rotor (12) in motion.

2. An electric motor (10) according to claim 1, wherein the closure means (28) comprises at least one flap (30) sized to cover at least one of the air inlet openings (24) in the closure position.

3. An electric motor (10) according to claim 2, wherein each flap (30) has a shape extending in an arc of a circle defined around the axis of rotation (X).

4. Electric motor (10) according to claim 2 or 3, in which the elastic return means (34) comprise, for each flap (30), at least one spring (36), extending radially between a hub (38) linked to the rotor (12) and the corresponding flap (30).

5. Electric motor (10) according to claim 4, wherein the stiffness of each spring (36) is chosen so that the corresponding flap (30) covers the corresponding opening(s) (24) when the rotational speed of the rotor (12) exceeds a predefined threshold.

6. An electric motor (10) according to claim 5, wherein the predefined threshold is substantially equal to half the maximum speed of the rotor (12).

7. Electric motor (10) according to any one of claims 2 to 6, comprising end-of-travel stops (40) limiting the movement of the flaps (30), each flap (30) coming into contact with a corresponding one of the stops (40) in the closed position.

8. An electric motor (10) according to any one of claims 1 to 6,

9. in which the closure position is defined by the maximum length of the elastic return means. Railway vehicle, characterized in that it comprises an electric motor according to any one of the preceding claims.

Images