Electric motors and / or generators for rail vehicles, associated bogies and rail cars

Abstract

To provide an electric motor and / or a power generator especially for a railway vehicle, with which a revolution speed of a shaft is increased without increasing a frequency of maintenance work and lowering reliability of an electric motor.SOLUTION: An electric motor and / or power generator (1) especially for a railway vehicle according to the present invention, comprises: a housing (10); a movable shaft (16) revolving around an axis (X-X') with respect to the housing (10); and at least two tilted bearings (18, 20) connecting the shaft (16) and the housing (10) with each other. Each of the at least two tilted bearings (18, 20) includes; an outer ring (30) attached to the housing (10); an inner ring (32) attached to the shaft (16); and a plurality of balls (34). Each of the balls (34) defines an outer contact track of the outer ring (30) and an inner contact track of the inner ring (32), with the outer contact track being offset in an axial direction with respect to the inner contact track.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates in particular to an electric motor and / or generator for a railway vehicle, a bogie for a railway vehicle, and a railway vehicle. [Background technology]

[0002] The invention applies in particular to high-speed electric motors, typically those configured to operate at a rotational speed of 5000-6000 revolutions per minute (rpm). Such motors are used in all types of railway vehicles, either low-speed vehicles (e.g. trams) or very high-speed vehicles (e.g. vehicles configured to travel at speeds above 250 km / h). It depends on the reduction ratio of the drivetrain.

[0003] These rail vehicles include power bogies each equipped with at least one electric motor, each of which includes a housing containing a stator and a rotor mounted on a shaft.

[0004] The shaft is connected to the housing by bearings that allow the shaft to rotate at high speeds, such as 5000 rpm, relative to the housing, so that the bearings rotate at high speeds.

[0005] However, such motors are not entirely satisfactory: increasing the shaft speed reduces the life of the bearings and can cause excessive noise levels and / or unstable rotor vibrations that can lead to in-service failures, especially for grease-lubricated bearings, as is common in railway traction motors, and therefore require frequent maintenance. Summary of the Invention [Problem to be solved by the invention]

[0006] One object of the present invention is to increase the shaft rotational speed without increasing the frequency of maintenance or reducing the reliability of the motor. [Means for solving the problem]

[0007] Therefore, the present invention relates to an electric motor and / or generator, particularly for railway vehicles, comprising a housing, a movable shaft that rotates about an axis relative to the housing, and at least two tilt bearings connecting the shaft and the housing, each of the two tilt bearings comprising an outer ring mounted on the housing, an inner ring mounted on the shaft, and a plurality of balls, each of which defines an outer contact raceway of the outer ring and an inner contact raceway of the inner ring, the outer contact raceway being axially offset or displaced relative to the inner contact raceway.

[0008] According to specific embodiments, the electric motor comprises any one or more of the following features, taken alone or in any technically possible combination: - the outer contact track includes a respective first contact point for each of said balls, and the inner contact track includes a respective second contact point for each of said balls, the first contact points and the second contact points defining a line that forms an angle in the range of 15 degrees to 25 degrees with a plane perpendicular to the axis. The electric motor further comprises at least one cylindrical bearing connecting the shaft and the housing, the cylindrical bearing comprising a cylindrical roller. The electric motor comprises a rotor, the tilted bearing being arranged axially between the rotor and a portion of the shaft adapted to transmit the drive torque to the transmission. At least one of the tilt bearings includes a cage comprising brass or a heat-resistant polymer. - the inner ring defines a groove including an inner contact raceway, the groove being symmetrical about a plane perpendicular to the axis; the outer ring defines a surface having, in sequence along the axis, a first portion followed by a second portion followed by a third portion, the first portion being a cylindrical surface having a first radius, the third portion being a cylindrical surface having a second radius that is significantly greater than the first radius, the second portion including an outer contact raceway. The outer ring defines a surface having, in sequence along the axis, a first portion followed by a second portion followed by a third portion, the second portion being a torus surface. Each of the balls comprises a ceramic material.

[0009] The invention also relates to a bogie for a railway vehicle, comprising at least one electric motor and / or generator as described above.

[0010] Finally, the invention relates to a railway vehicle comprising at least one bogie as described above.

[0011] The invention will be better understood on reading the following description, given by way of example only and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of an electric motor and / or generator for a rail vehicle. [Figure 2] 2 is a cross-sectional view of a portion of the electric motor and / or generator shown in FIG. 1, including a bearing. DETAILED DESCRIPTION OF THE INVENTION

[0013] With reference to FIG. 1, a portion of a bogie of a railway vehicle comprising an electric motor 1 and a transmission 6 will be described.

[0014] The electric motor 1 is configured to convert electrical energy into mechanical energy.

[0015] Alternatively, or in addition, the electric motor 1 may be configured to convert mechanical energy into electrical energy in the opposite way. An electric motor 1 having such a function is called a generator. In the following description, for ease of reading, the term "electric motor" refers simultaneously to both electric motors and generators.

[0016] The electric motor 1 is, for example, a permanent magnet motor or an induction motor. The electric motor 1 is, in particular, a high-power electric motor, for example, a motor of more than 100 kW.

[0017] The electric motor 1 includes a housing 10, and a stator 12 and a rotor 14 housed within the housing 10. The electric motor 1 further includes a shaft 16, a first tilt bearing 18, a second tilt bearing 20, and a cylindrical bearing 22. The first tilt bearing 18, the second tilt bearing 20, and the cylindrical bearing 22 connect the housing 10 and the shaft 16.

[0018] In particular, the housing 10 comprises a first flange 24 to which the first tilt bearing 18 and the second tilt bearing 20 are preferably directly mounted. The housing 10 further comprises a second flange 26 to which the cylindrical bearing 22 is preferably directly mounted.

[0019] In a variant not shown, the first tilt bearing 18 and the second tilt bearing 20 are mounted to the first flange 24 via a bearing housing. Similarly, the cylindrical bearing 22 is mounted to the second flange 26, for example, via a bearing housing. In this embodiment, the flanges 24, 26 are made, for example, of an aluminum alloy.

[0020] The rotor 14 is mounted on a shaft 16 of the electric motor 1 within the housing 10. The rotor 14 is mounted for rotation relative to the stator 12 about an axis X-X', also referred to as the axis of rotation. The stator 12 surrounds the rotor 14 within the housing 10 parallel to the axis X-X' and is coaxial with the rotor 14. As is conventional, the rotor 14 and the stator 12 are capable of converting electrical energy into mechanical energy transmitted by the shaft 16, or vice versa.

[0021] The shaft 16 defines a first section 28 located axially on one side of the rotor 14, adapted to transmit mechanical torque between the rotor 14 and the transmission 6, and a second section 29 opposite the first section 28 with respect to the rotor 14. In particular, the first tilt bearing 18 and the second tilt bearing 20 are arranged at the level of the first section 28, and the cylindrical bearing 22 is arranged at the level of the second section 29. In particular, the first tilt bearing 18 and the second tilt bearing 20 are arranged between the rotor 14 and the transmission 6 along the axis X-X'.

[0022] The shaft 16 has a first diameter 27A at the level of the first tilt bearing 18 and the second tilt bearing 20. The first diameter 27A is selected so that the shaft 16 with its parameters can transfer mechanical torque between the rotor 14 and the transmission 6. In particular, the first diameter 27A is the minimum diameter required to allow the transmission of mechanical torque.

[0023] The first diameter 27A of the shaft 16 in the first section 28 (visible in particular in FIG. 1) is, for example, 40 to 100 mm.

[0024] The shaft 16 has a second diameter 27B at the level of the cylindrical bearing 22. The second diameter 27B is, for example, definitely smaller than the first diameter 27A. In particular, the second diameter 27B of the second section 29 is definitely smaller than the first diameter 27A of the first section 28, since there is no torque transfer in the second section 29 of the shaft 16.

[0025] In an alternative embodiment, the second section 29 of the shaft 16 may also transfer mechanical torque, albeit at a disadvantage in terms of the maximum torque that can be transmitted.

[0026] Therefore, when the shaft 16 rotates, the cylindrical bearing 22 rotates slower than the first tilt bearing 18 and the second tilt bearing 20. In particular, the peripheral speed of the bearings 18 and 20 is lower. The rotational speed (e.g., rpm) of the shaft 16 is the same in the first section 28 and the second section 29. The peripheral speed obviously depends on the radii of the bearings 18, 20, 22 and the rotational speed of the shaft 16. For example, the allowable peripheral speed for roller bearings is lower than for ball bearings.

[0027] The first tilt bearing 18 and the second tilt bearing 20 form an axial stop for the shaft 16. That is, the first tilt bearing 18 and the second tilt bearing 20 are configured to limit the axial movement of the shaft 16.

[0028] The first tilt bearing 18 and the second tilt bearing 20 are spindle bearing types, and each of the first tilt bearing 18 and the second tilt bearing 20 includes an outer ring 30, an inner ring 32, a plurality of balls 34, and a cage 36 (particularly visible in FIG. 2).

[0029] The inner race 32 is attached to the shaft 16, and the outer race 30 is attached to the housing 10, specifically to the first flange 24. The balls 34 are sandwiched between the outer race 30 and the inner race 32.

[0030] The outer ring 30 defines a surface S comprising, in sequence along the axis XX', a first portion S1 followed by a second portion S2 followed by a third portion S3.

[0031] The first portion S1 is a cylindrical surface having a first radius R1 relative to the axis XX'.

[0032] The second portion S2 is a torus surface. The third portion S3 is a cylindrical surface having a second radius R2 that is significantly greater than the first radius R1. The second portion S2 is disposed between the first portion S1 and the third portion S3.

[0033] As can be seen particularly in Figure 2, the first portion S1 defines a line of intersection S1' with a radial plane II containing the axis X-X', and the third portion S3 defines a line of intersection S3' with the radial plane II containing the axis X-X'. The line of intersection S1' is equidistant from the axis X-X' with the first radius R1, and the line of intersection S3' is equidistant from the axis X-X' with the second radius R2.

[0034] The second portion S2 forms a curve S2' in the radial plane II. The curve S2' connects to the intersection line S1' at a first end E1 and to the intersection line S3' at a second end E2. The curve S2' is, for example, a portion of a circle.

[0035] The inner ring 32 defines a groove S4 symmetrical with respect to a plane AA perpendicular to the axis X-X'. The groove S4 forms a curved line like a segment of a circle (particularly visible in Figure 2) along a radial surface II.

[0036] Each ball 34 defines an outer contact raceway C1 on the outer ring 30 and an inner contact raceway C2 on the inner ring 32. The outer contact raceway C1 is axially offset relative to the inner contact raceway C2.

[0037] The outer contact track C1 has a first contact point P1 with each ball 34. The inner contact track C2 has a second contact point P2 with each ball 34.

[0038] In particular, the first contact points P1 form contact points with the outer ring 30 of each of the balls 34, and the second contact points P2 form contact points with the inner ring 32 of each of the balls 34.

[0039] In particular, the second portion S2 of the surface S has an outer contact track C1 and the groove S4 has an inner contact track C2.

[0040] That is, each ball 34 forms an inclined contact point between the outer ring 30 and the inner ring 32. The term "inclined bearing" refers specifically to an inclined contact type bearing. As can be seen particularly in Figure 2, the first contact point P1 and the second contact point P2 define a straight line DR that forms an angle α with a plane AA perpendicular to the axis X-X'. The angle α is, for example, in the range of 10 to 25 degrees, and is preferably 25 degrees.

[0041] For example, each ball 34 comprises a ceramic material. Preferably, each ball comprises at least 50% by weight of ceramic material. More preferably, each ball is formed of a single material. For example, each ball is formed of ceramic material.

[0042] The retainer 36 is configured to hold the balls 34 in place relative to one another.

[0043] According to one embodiment, the cage 36 is made of 50% by weight or more, preferably 80% by weight or more, and more preferably 95% by weight or more of brass. In particular, the cage 36 is made of a single material. For example, the cage 36 is made of brass.

[0044] According to another embodiment, the retainer 36 is made of a heat-resistant polymer. For example, the retainer 36 is made of 50% by weight or more, preferably 80% by weight or more, and more preferably 95% by weight or more of polyetheretherketone (PEEK). More preferably, according to one embodiment, the retainer 36 is made of PEEK.

[0045] A cage 36 formed from PEEK provides sufficient mechanical robustness while remaining lightweight, thereby increasing the peripheral rotational speeds possible, particularly in each of the tilt bearings 18,20.

[0046] Advantageously, the tilt bearings 18, 20 are characterized by a factor N x Dm, where N is the revolutions per minute of the shaft 16, x is the multiplication symbol and Dm is the mean diameter (in millimeters) of each of the tilt bearings 18, 20. The mean diameter Dm is defined as follows (as can be seen in particular in FIG. 2): Dm=(D+d) / 2 where: D is the outer diameter of the first and second bearings, d is the inner diameter of each of the first and second bearings.

[0047] The coefficient N×Dm of each of the first and second bearings is in the range of 500,000 to 850,000. For example, when the average diameter of bearing 18 or 20 is 102.5 mm and the maximum speed is 7,500 rpm, N×Dm is 768,750.

[0048] In particular, the factor N×Dm is proportional to the peripheral velocity as defined above.

[0049] The cylindrical bearing 22 forms a sliding pivot, i.e., the cylindrical bearing 22 is configured to support only radial forces acting on the shaft 16.

[0050] The cylindrical bearing 22 includes cylindrical rollers 40, an outer ring 42, and an inner ring 44. The cylindrical bearing 22 further includes a cage 46 configured to maintain a predetermined distance between the cylindrical rollers 40.

[0051] The outer ring 42 is attached to, for example, the second flange 26 and the inner ring 44 is attached to the shaft 16 .

[0052] The cylindrical roller 40 is made of, for example, a ceramic material.

[0053] The cylindrical bearing 22 is characterized by a smaller coefficient N*Dm than the tilt bearings 18, 20. The coefficient N*Dm is, for example, approximately 600,000.

[0054] The above features allow for increased rotational speeds of shaft 16 without increasing maintenance frequency or reducing motor reliability.

[0055] The electric motor 1 according to the invention has several advantages.

[0056] The provision of two tilt bearings 18, 20 allows for higher rotational speeds of the shaft 16 while still requiring less frequent maintenance.

[0057] The inclined bearings 18, 20 allow for minimizing play of the shaft 16 relative to the fixed parts of the structure of the electric motor 1 (in particular the first flange 24 and the second flange 26, the stator 12 and the housing 10), thereby reducing vibrations of the shaft 16 at high speeds, which are detrimental to the reliability of the machine.

[0058] Furthermore, by mounting the first tilt bearing 18 and the second tilt bearing 20 on the shaft 16 in a first section 28 having a first diameter 27A, and providing the shaft 16 with a cylindrical bearing 22 in a second section 29 having a second diameter 27B, the motor 1 is configured to rotate faster without significant wear on the bearings 18, 20, 22. Indeed, because the diameter 27B is smaller than the diameter 27A, the peripheral speed of the cylindrical bearing 22 is lower than the peripheral speed of the tilt bearings 18, 20. Because the geometry of the tilt bearings 18, 20 is optimized for the cylindrical bearing 22, the tilt bearings 18, 20 are particularly adapted for rotation at higher speeds than prior art solutions.

[0059] In particular, the tilt bearings 18, 20 allow for rotation of the shaft 16 at least 10,000 rpm, including, for example, embodiments in which the bearings are lubricated with grease (and even more so if the bearings are lubricated with oil).

[0060] In particular, according to the present invention, for a given diameter bearing, the number of balls 34 is optimized to allow for stiffening of the cage 36 to accommodate the constraints of the railway environment, such as high rotational speeds.

[0061] The electric motor 1 according to the invention is also particularly compact thanks to the inclined bearings 18, 20 with cages 36 which allow higher rotational speeds. [Explanation of symbols]

[0062] 1 electric motor 6 Transmission 10. Housing 12 Stator 14 rotor 16 shaft 18 First tilt bearing 20 Second tilt bearing 22 Cylindrical bearings 24 First flange 26 Second flange 27A First Diameter 27B Second diameter 28 First Section 29 Second Section 30 outer ring 32 Inner circle 34 balls 35 Retainer 40 Cylindrical roller 42 outer ring 44 Inner Circle 46 Cage C1 outer contact track C2 inner contact track E1 First end E2 Second end P1 First contact point P2 Second contact point R1 First radius R2 Second radius S surface S1 First part S2 Second part S3 Third part S1' Intersecting line S2' curve S3' tangent line S4 groove XX' axis

Claims

1. An electric motor and / or generator (1) for a railway vehicle, comprising: a housing (10); a movable shaft (16) that rotates about an axis (X-X') relative to the housing (10); and at least two tilt bearings (18, 20) that connect the movable shaft (16) and the housing (10), Each of the two inclined bearings (18, 20) comprises an outer ring (30) attached to the housing (10), an inner ring (32) attached to the movable shaft (16), and a plurality of balls (34), each of which defines an outer contact raceway (C1) of the outer ring (30) and an inner contact raceway (C2) of the inner ring (32), the outer contact raceway (C1) being axially offset with respect to the inner contact raceway (C2); The electric motor (1) further comprises at least one cylindrical bearing (22) connecting the movable shaft (16) and the housing (10), the cylindrical bearing (22) comprising a cylindrical roller (40); The movable shaft (16) has a first diameter (27A) at the level of the first inclined bearing (18) and the second inclined bearing (20), and the movable shaft (16) has a second diameter (27B) at the level of the cylindrical bearing (22), the second diameter (27B) being substantially smaller than the first diameter (27A); The electric motor (1) is a high-power electric motor exceeding 100 kW, and is an electric motor and / or generator (1).

2. 2. The electric motor and / or generator (1) according to claim 1, wherein the outer contact track (C1) comprises a first contact point (P1) for each of the balls (34), and the inner contact track (C2) comprises a second contact point (P2) for each of the balls (34), and the first contact point (P1) and the second contact point (P2) define a straight line (DR) that forms an angle (α) in the range of 15 degrees to 25 degrees with a plane (AA) perpendicular to the axis (X-X').

3. 3. An electric motor and / or generator (1) according to any one of claims 1 to 2, wherein the electric motor (1) comprises a rotor (14), and the inclined bearings (18, 20) are arranged axially between the rotor (14) and a portion of the movable shaft (16) adapted to transmit a drive torque to a transmission device (6).

4. 4. An electric motor and / or generator (1) according to any one of claims 1 to 3, wherein at least one of the tilt bearings (18, 20) comprises a cage (36) comprising brass or a heat-resistant polymer.

5. 5. An electric motor and / or generator (1) according to any one of claims 1 to 4, wherein the inner ring (32) defines a groove (S4) including the inner contact raceway (C2), the groove (S4) being symmetrical about a plane (AA) perpendicular to the axis (X-X'), and the outer ring (30) defines a surface (S) having, in order along the axis (X-X'), a first portion (S1), followed by a second portion (S2), followed by a third portion (S3), the first portion (S1) being a cylindrical surface with a first radius (R1), the third portion (S3) being a cylindrical surface with a second radius (R2) that is significantly greater than the first radius (R1), and the second portion (S2) including the outer contact raceway (C1).

6. 6. An electric motor and / or generator (1) according to any one of claims 1 to 5, wherein the outer ring (30) defines a surface (S) having, in sequence along the axis (X-X'), a first portion (S1), followed by a second portion (S2), followed by a third portion (S3), the second portion (S2) being a toroidal surface.

7. 7. An electric motor and / or generator (1) according to any one of claims 1 to 6, wherein each of said balls (34) comprises a ceramic material.

8. A bogie for a railway vehicle comprising at least one electric motor and / or generator (1) according to any one of claims 1 to 7.

9. A railway vehicle comprising at least one bogie according to claim 8.

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