Wheel set bearing for rail vehicle and rail vehicle

Abstract

The invention relates to a wheelset bearing for a rail vehicle, and the wheelset bearing comprises a rolling bearing assembly (7) having three bearing rings (4, 8, 9), which are specifically two inner rings (4, 8) arranged to be connected to a wheelset shaft (2) and an outer ring (9) arranged to be connected to a housing (6). The rolling bearing assembly (7) is designed as a four-row angular contact ball bearing in an O-type arrangement structure, wherein two rolling element rows (16, 17) are arranged to contact a first inner ring (4) to absorb axial forces in a first direction, and two rolling element rows (18, 19) are arranged to contact a second inner ring (8) to absorb forces in an opposite axial direction. The invention also relates to a rail vehicle.

Description

Technical Field

[0001] The invention relates to a wheelset bearing for a rail vehicle according to the preamble of claim 1. The invention also relates to a rail vehicle having at least two such wheelset bearings. Background Art

[0002] Such a wheelset bearing is known, for example, from DE 10 2006 015 289 A1. The known wheelset bearing is a double-row tapered roller bearing having two inner rings and a single outer ring. In addition, in the wheelset bearing according to DE 10 2006 015 289 A1, a support ring is provided for axially supporting the inner ring.

[0003] Another wheelset bearing designed as a tapered roller bearing is known from DE 10 2017 119 249 A1. In this case, a generator unit is arranged on the wheelset bearing. The stator of the generator unit is connected to a cover covering the wheelset bearing on one end of the wheelset axle.

[0004] DE 101 28 861 A1 discloses a wheelset bearing designed as a double-row cylindrical rolling bearing. A damping element is arranged between the cylindrical rolling bearing and the wheelset axle of the rail vehicle so that vibrations emitted from the rail wheels reach the rolling bearing, ie the cylindrical rolling bearing, only in a damped form.

[0005] A measuring bearing for a wheelset bearing of a rail vehicle is known from EP 2 276 658 B1. EP 2 276 658 B1 mentions, inter alia, ball bearings, cylindrical roller bearings and needle roller bearings as conceivable types of rolling bearings.

[0006] DE 10 2017 112 338 A1 describes a double row angular contact ball bearing.

[0007] DE 10 2007 049 982 A1 discloses a rolling bearing having two angular contact ball bearings arranged obliquely in an O-arrangement.

[0008] DE 10 2013 224 545 A1 describes a wheel bearing for a vehicle having four angular contact ball bearing units.

[0009] DE 10 2006 025 551 A1 discloses a multi-row axially prestressed angular contact ball bearing and a method for producing the same. Summary of the invention

[0010] The object of the present invention is to specify a wheelset bearing for a rail vehicle which has been further developed compared to the aforementioned prior art and which features a particularly favorable ratio between possible service life and maintenance expenditure.

[0011] According to the invention, this object is achieved by a wheelset bearing having the features of claim 1. The wheelset bearing comprises a rolling bearing assembly having three bearing rings, specifically two inner rings arranged for connection to the wheelset shaft and one outer ring arranged for connection to the housing. The rolling bearing assembly is designed as a four-row angular contact ball bearing in an O-type arrangement, wherein two rolling element rows are arranged to contact the first inner ring to absorb axial forces in a first direction, and two rolling element rows are arranged to contact the second inner ring to absorb forces in the opposite axial direction. In this case, the inner ring or the outer ring has a single-shoulder rolling element raceway for receiving each rolling element row. As seen in a cross section along the center axis through the wheelset bearing, the single-shoulder rolling element raceway is defined by a radial line, which is perpendicular to the center axis and passes through the rolling element center point of each rolling element in the rolling element row. The rolling element raceway starts from the radial line and extends from the center point of the rolling element in the direction of the shoulder with a constant radius through an angle in the range of 35° to 75° to a reference point. The rolling element raceway follows, from the reference point, the tangent applied to the rolling element raceway at the reference point.

[0012] In particular, the rolling element raceway extends from a radial line and from a center point of the rolling element in the direction of the shoulder over an angle in the range of 35° to 50° to the reference point.

[0013] Thus, as seen in a cross section along the central axis through the wheelset bearing, the rolling element raceway is formed by a reference point of a tangent applied to the rolling element track at the reference point. Thus, the rolling element raceway guiding the rolling element has a constant radius in the region between the radial line and the reference point, and does not have a constant radius in the outer region in the direction of the shoulder, but rather extends tangentially following the applied tangent. This ensures that edge stresses are avoided under higher axial loads such as may occur in railway applications; for example, due to rail joints, since the contact ellipse does not "extend upwards" over a sharp edge transition, but can expand in an elliptical manner along the tangential extension. Edge stresses can thus be avoided. This improves the friction behavior and prolongs the service life of the wheelset bearing. In particular, the tangential exit of the reference point is at least 2 mm long, in particular 2 mm to 10 mm.

[0014] A general feature of multi-row angular contact ball bearings in an O-arrangement is that the pressure lines as a whole describe a geometric shape similar to the letter "O"; more precisely, a geometric shape in the form of a rhombus. Multi-row bearings in an X-arrangement must also be distinguished from multi-row bearings in an O-arrangement, in which the pressure lines intersect - like the letter "X". In the present case, i.e. in a four-row rolling bearing assembly, two nested rhombuses are formed by the pressure lines of the bearing.

[0015] This is based on the following considerations: Wheel bearings for rail vehicles require long maintenance intervals; for example more than three million kilometers of maintenance-free operation. In addition, the service life of the grease is noteworthy, especially in view of the long-term trend towards increasing speed limits in rail vehicles. The service life of the grease depends in particular on the temperature in the wheelset bearing, which is significantly influenced by the friction in the bearing.

[0016] Starting from these considerations, the four-row angular contact ball bearing of the wheelset bearing according to claim 1 provides a type of rolling bearing which is characterized by particularly low friction compared to cylindrical and tapered rolling bearings. Surprisingly, it has been shown that despite the lack of line contact as is the case with tapered and cylindrical rolling bearings due to the design, a load capacity sufficient for rail vehicles can be achieved using the available space. In a preferred embodiment, there are no intermediate rings between the inner rings of the wheelset bearing. Instead, the inner rings preferably abut directly against each other.

[0017] Technical background on four-row angular contact ball bearings in an O-arrangement, also known as double tandem bearings, can be found in DE 84 05 082 U1, DE 103 31 936 B4, DE 198 39 481 A1 and DE 10 2017 112 338 A1. However, all of the cases mentioned are related to bearings for motor vehicles.

[0018] The two rows of rolling elements are formed with particularly little axial play, in particular the two rows of rolling elements form no axial play. This means that the outer row of rolling elements is preferably formed by rolling elements, i.e. balls, whose diameter is at least 5% and at most 25%, preferably 12% to 17% larger than the diameter of the rolling elements in the two inner rows of rolling elements. These dimensional ratios contribute to uniform compression at low levels, wherein a uniform contact pattern is provided in normal operation, i.e. when used in a rail vehicle.

[0019] The wheelset bearing customized for rail vehicles according to the present invention is designed mainly for absorbing radial forces and to a lesser extent for absorbing axial forces. Here, radial forces and axial forces can be absorbed by all rolling element rows. In a preferred embodiment, the contact angle of the two outer rolling element rows deviates from the contact angle of the two inner rolling element rows by no more than 6°. This means that each rolling element row can provide support in the radial direction and support in the axial direction in approximately the same proportion. The contact angle of each rolling element row is preferably at least 24° and at most 36°, for example uniformly 30°.

[0020] In a stress-appropriate and assembly-friendly manner, the groove-shaped rolling element raceway is preferably formed by the inner ring, while the rolling element raceway of the outer ring is designed with a shoulder and therefore provides support only in a single axial direction. On the other hand, in the opposite axial direction, the raceway of the outer ring merges into the cylindrical inner peripheral surface of the outer ring, which means that the rolling element raceway extends tangentially. However, the following embodiment is also possible: in this embodiment, the outer ring forms the groove-shaped rolling element raceway, while the rolling element raceway of the inner ring is designed as a single shoulder. Similarly, the following embodiments can be realized: in these embodiments, the outlet of the rolling element raceway, i.e. the surface portion opposite the shoulder of the raceway, describes a conical surface, wherein the corresponding tapered portion widens in the direction of the end face of the outer ring close to the rolling element raceway.

[0021] With regard to maximizing the service life, it has been found to be advantageous if the axial play of the two outer rolling element rows of the double tandem bearing is less than the axial play of the two inner rolling element rows. In particular, there is no axial play on the two outer rolling element rows, while the axial play on the two inner rolling element rows is greater than 10 μm, assuming a wheelset bearing temperature of 20°C and that the wheelset bearing has not yet been mounted on the wheelset axle in the position of use. Since the axial play decreases from the inner rolling element row to the outer rolling element row, the arrangement of the rolling elements is also particularly suitable for absorbing tilting loads.

[0022] When the wheelset bearing is at operating temperature, i.e. a temperature above 50°C, which usually occurs when the wheelset bearing is in operation when mounted on the wheelset axle, the axial clearance between the outer and inner rolling element rows is 0, resulting in a uniform load on all rolling element rows.

[0023] The rolling elements of each rolling element row can be guided through the cage in a manner known per se. Likewise, the entire rolling bearing assembly can be sealed in a manner known per se, wherein preferably low-friction seals are used. Grease is preferably used as lubricant. Due to the point contact between the rolling elements and the bearing rings, the temperature rises only moderately when the wheelset bearing is in operation, which means that the grease is subjected to little stress.

[0024] An important role is also played by the reduced shear stress on the lubricant due to point contact compared to line contact, which also benefits the service life of the grease. In this context, reference can also be made to the standard DIN 51825 "Lubricants – Lubricating greases K – Classification and requirements", which applies to greases for lubricating rolling bearings, plain bearings and sliding surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following, exemplary embodiments of the present invention are described in more detail with the aid of the accompanying drawings. In the accompanying drawings:

[0026] Figure 1 A wheelset bearing is shown in cross section.

[0027] Figure 2 Details of the wheelset bearings are shown. DETAILED DESCRIPTION

[0028] The wheelset bearing, generally indicated at 1, serves to support a wheelset axle 2 in a support structure 3 of a rail vehicle (not shown separately). The wheelset bearing 1 comprises a rolling bearing assembly 7 having two inner rings 4, 8 and a single outer ring 9. The entire rolling bearing assembly 7 is supported in the axial direction by an end cap 11, which is screwed to the front end of the wheelset axle 2 using screws 12. The screws 12 are inserted through holes 14 in the end cap 11. Seals for sealing the rolling bearing assembly 7 on both sides are indicated at 13. The rolling bearing assembly 7 is lubricated with grease as lubricant.

[0029] The rolling bearing assembly 7 is constructed as a four-row angular contact ball bearing in the form of a double tandem bearing. The individual rolling element rows are denoted by 16, 17, 18, 19. Figure 1 In the arrangement of , rolling element rows 16, 17 roll on the inner ring 4 on the left, and rolling element rows 18, 19 roll on the bearing channel ring 8 on the right. The rolling element raceways of the inner rings 4, 8 are denoted by 21, and the four rolling element raceways of the outer ring 9 are denoted by 22. The rolling elements 10, 23 of each rolling element row 16, 17, 18, 19 are guided in a cage 20.

[0030] The rolling element rows 16, 17 support the wheelset shaft 2 in a first axial direction relative to the bearing housing 6. The rolling element rows 18, 19 are used to support in the opposite axial direction. The entire rolling bearing assembly 7 is mirror-symmetrical about the plane located between the bearing races 4, 8. In particular, Figure 2It can be seen that the diameter of the rolling elements 10 of the two inner rolling element rows 17, 18, indicated by D1, is smaller than the diameter of the rolling elements 23 of the two outer rolling element rows 16, 19, indicated by D2. By definition, a circle drawn through the centers WM of all rolling elements of the rolling element rows 16, 17, 18, 19 represents the pitch circle of the relevant rolling element row 16, 17, 18, 19. The pitch circle diameter of the inner rolling element rows 17, 18 is smaller than the pitch circle diameter of the outer rolling element rows 16, 19.

[0031] The four raceways 21 provided by the bearing inner rings 4, 8 are each designed in the form of a groove. In contrast, the rolling element raceways 22 of the outer ring 9 are each designed as a single-shoulder raceway having the shape of half a groove. Figure 2 In the embodiment of the present invention, different tangents T1, T2 are applied to the rolling element raceway 22, which are each placed through the reference points BP1, BP2. In any case, the reference point BP2 is located on the radial line RL, which passes through the rolling element center point WM and is located in the plane where the center axis 5 of the rolling bearing assembly 7 represents the surface normal of the plane. The tangent T2 on which the reference point BP2 is located is aligned parallel to the axis of rotation of the rolling bearing assembly 7, i.e. to the center axis 5 of the wheelset shaft 2. The single-shoulder shape of the rolling element raceway 22 is indicated by the fact that all tangents that can be applied to the raceway 22 are inclined in the same direction relative to the center axis 5, or in the extreme case, i.e. in the case of the tangent T2, are spaced parallel to the center axis 5. The tangent T1 on which the reference point BP1 is located is close to the shoulder. Starting from the radial line RL and the rolling element center point WM, the reference point BP1 is located here on a line that encloses an angle β1, β2 of approximately 48° with the radial line RL.

[0032] Starting from the reference point BP1 , the rolling element raceway 22 follows a tangent line T1 applied to the rolling element raceway 22 at the reference point BP1 .

[0033] The rolling element raceway 22 guiding the rolling elements 10, 23 does not have a constant radius in the outer region in the direction of the shoulder, but has a tangential extension that follows the tangent T1. This ensures that edge stresses are avoided under higher axial loads, such as may occur in railway applications; for example, due to rail joints, since the contact ellipse does not "extend upwards" over a sharp edge transition, but can expand in an elliptical manner along the tangential extension. A tangent T2 is arranged on the other side of the rolling element track 22, which tangent indicates the course of the rolling element track 22 and is also intended to enable the contact ellipse to expand unhindered. Edge stresses can thus be avoided. This improves the friction behavior and increases the service life of the wheelset bearing.

[0034] The rolling bearing rows 17, 18 are also located in the region of the inner rings 4, 8 in the single-shoulder rolling bearing raceway 21. A tangent T3 is generated at the reference point BP3, which defines the course of the rolling element raceway 21 and is also intended to enable the contact ellipse to expand unhindered. Only the rolling bearing rows 16, 19 are located in the region of the inner rings 4, 8 in the double-shoulder rolling bearing raceway 24.

[0035] According to the usual definition, the pressure line represented by DL passes through the rolling element center WM and the contact point on the bearing rings 4, 8, 9. In the exemplary embodiment, the contact angles represented by α1, α2 given on the outer rolling element rows 16, 19 and on the inner rolling element rows 17, 18 are consistent with 30°. The assembly direction indicated as MR indicates the direction in which the outer ring 9 is to be displaced relative to the inner ring 8 when assembling the rolling bearing assembly 7. After assembly, the rolling elements 23 of the outer rolling element rows 16, 19 are arranged between the inner rings 4, 8 and the outer ring 9 in a clearance-free manner in the axial direction. On the other hand, the inner rolling element rows 17, 18 have a clearance of more than 10 μm, which is also related to the axial direction.

[0036] Description of Reference Numerals

[0037] 1 Wheel bearing

[0038] 2 wheel set axle

[0039] 3 Support structure

[0040] 4 Bearing inner ring

[0041] 5 Central axis

[0042] 6 Bearing housing

[0043] 7 Rolling bearing assemblies, four-row angular contact ball bearings

[0044] 8 Bearing inner ring

[0045] 9 Bearing outer ring

[0046] 10 Rolling elements

[0047] 11 End cap

[0048] 12 Screws

[0049] 13 Seals

[0050] 14 Hole in end cap 15

[0052] 16 Rolling element columns

[0053] 17 Rolling element columns

[0054] 18 Rolling element columns

[0055] 19 Rolling element columns

[0056] 20 Cage

[0057] 21 Inner raceway

[0058] 22 Outer ring raceway

[0059] 23 Rolling elements

[0060] 24 Inner Loop

[0061] α1, α2 contact angle

[0062] β1, β2 angles

[0063] BP2, BP1, BP3 reference points

[0064] D1, D2 rolling element diameter

[0065] DL pressure line

[0066] MR assembly direction

[0067] RL Radial Line

[0068] T1, T2, T3 tangent

[0069] WM Rolling element center.

Claims

1. A wheelset bearing (1) for a rail vehicle, the wheelset bearing comprising a rolling bearing assembly (7) having three bearing rings (4, 8, 9), the bearing rings being specifically two inner rings (4, 8) arranged to be connected to a wheelset shaft (2) and an outer ring (9) arranged to be connected to a housing (6), wherein: The rolling bearing assembly (7) is designed as a four-row angular contact ball bearing in an O-type arrangement structure, wherein two rolling element rows (16, 17) are arranged to contact the first inner ring (4) to absorb axial forces in a first direction, and the other two rolling element rows (18, 19) are arranged to contact the second inner ring (8) to absorb forces in an opposite axial direction, characterized in that the inner ring (4, 8) or the outer ring (9) for accommodating each rolling element row (16, 17, 18, 19) is formed with a single-shoulder rolling element raceway (22), wherein, as observed in a cross section along a center axis (5) passing through the wheelset bearing (1), the single-shoulder rolling element raceway (22) is defined by a radial line (RL) which is perpendicular to the radial line. The central axis (5) extends through the rolling element center (WM) of each rolling element (10, 23) of the rolling element row (16, 17, 18, 19), wherein the single-shoulder rolling element raceway (22) extends from the radial line (RL) and from the rolling element center (WM) in the shoulder direction at a constant radius through an angle (β1, β2) in the range of 35° to 75° to a reference point (BP1), and the single-shoulder rolling element raceway (22) is formed by the reference point (BP1) following a tangent (T1) applied to the single-shoulder rolling element raceway (22) at the reference point (BP1), and the axial clearance of the two outer rolling element rows (16, 19) is smaller than the axial clearance of the two inner rolling element rows (17, 18).

2. The wheelset bearing (1) according to claim 1, characterized in that: The diameter (D2) of the rolling elements (23) of the two outer rolling element rows (16, 19) is at least 5% and at most 25% larger than the diameter (D1) of the rolling elements (10) of the two inner rolling element rows (17, 18).

3. The wheelset bearing (1) according to claim 1, characterized in that: The contact angle (α2) of the two outer rolling element rows (16, 19) deviates from the contact angle (α1) of the two inner rolling element rows (17, 18) by no more than 6°.

4. The wheelset bearing (1) according to claim 3, characterized in that: The contact angle (α1, α2) of each rolling element row (16, 17, 18, 19) is at least 24° and at most 36°.

5. The wheelset bearing (1) according to claim 4, characterized in that: All rolling element rows (16, 17, 18, 19) of the rolling bearing assembly (7) have a uniform contact angle (α1, α2) of 30°.

6. The wheelset bearing (1) according to any one of claims 1 to 5, characterized in that: The outer ring (9) has the single-shoulder rolling element raceway (22) on each rolling element row (16, 17, 18, 19).

7. The wheelset bearing (1) according to claim 1, characterized in that: There is no axial play in the two outer rolling element rows (16, 19).

8. The wheelset bearing according to claim 1, characterized in that: The axial play on the two inner rolling element rows (17, 18) is greater than 10 µm.

9. A rail vehicle comprising at least one wheelset axle (2), on which at least one wheelset bearing (1) according to any one of claims 1 to 8 is arranged.

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