DE102006055028A1 - Radial rolling bearings, in particular for the storage of shafts in wind power transmissions - Google Patents

Abstract

The invention relates to a radial roller bearing, which consists essentially of an outer bearing ring (2) with an inner raceway (3) and an inner bearing ring (4) with an outer raceway (5) and a plurality between the bearing rings (2, 4) whose raceways (3, 5) rolling rolling elements (6), which are held by a bearing cage (7) in the circumferential direction at regular intervals to each other. To avoid slippage between the rolling elements (6) and the bearing rings (2, 4) several uniformly distributed on the circumference rolling elements (6) are replaced by hollow rollers (8) having a slightly larger diameter and a lower modulus of elasticity than the other rolling elements ( 6) in order to ensure a constant contact with the bearing rings (2, 4) and thus a continuous drive of the bearing cage (7) with kinematic speed in the load-free state of the radial roller bearing (1). According to the hollow rollers (8) of an application-specific bearing steel and treated by a heat treatment process, by the one in the inner and outer circumferential surfaces (9, 10) of the hollow rollers (8) near-surface residual compressive stresses are inducible and by the other the hollow rollers (8 ) with a hardness> 58 HRC on the inner lateral surfaces (9) on the one hand a high rollover resistance and on the other hand such a toughness have such that their outer lateral surfaces (10) have an increased bending fatigue strength> 650 Mpa.

Description

Field of the invention

The The invention relates to a radial rolling bearing the preamble-forming features of claim 1, and they is particularly advantageous at least temporarily under very low Load ongoing storage, such as the storage of waves in wind power transmissions, feasible.

Background of the invention

the Specialist in rolling bearing technology It is well known that radial rolling bearings with sufficient load have an optimal kinematic operating state, in which the rolling elements without to slide on the raceways of the inner and outer bearing ring roll. Furthermore, it is at least temporarily low burdened radial bearings known to be from the rolling elements and their camp cage existing rolling element set due to the friction in the bearing or due to the high inertia force of the rolling element set and the temporarily low contact force between the rolling elements and does not rotate the raceways at kinematic speed. The speed of the rolling element set thus stays opposite the kinematic speed back, so that the rolling elements in a kinematic not optimal state by the between these rolling elements and at least one career slip is present. It can be at the contact surfaces between the rolling elements and the runway build up a lubricating film, but at a sudden Speed or load change destroyed so that at the slip-contact points within shortest time there is no longer sufficient lubricating film. As a consequence, that there is a metallic contact of the raceway with the Rolling elements comes and These slide on the raceway until the rolling elements reach the kinematic speed are accelerated. This size Differential speed between the raceway and the rolling elements as well The lack of a separating lubricating film is thus the reason that it in the surfaces the raceway and the rolling elements to high tangential tensions comes with the strongest signs of wear, Such as roughening of the tracks, Materialaufreißungen and lubrication mostly associated with micropittings and premature Failure of the radial rolling bearing to lead.

By the FR 2 479 369 Therefore, a generic Radial roller bearing has been proposed, which consists essentially of an outer bearing ring with an inner raceway and a coaxial therewith arranged inner bearing ring with an outer race and from a plurality between the bearing rings on their careers rolling and by a bearing cage in the circumferential direction in uniform Intervals held to each other rolling elements, in which to avoid the described slip effect and the resulting disadvantages between the rolling elements and the bearing rings several evenly distributed on the circumference rolling elements are replaced by hollow rollers. These also axially slightly shorter than the other rolling elements formed hollow rollers have a slightly larger diameter and a lower modulus than the other Wälzkör by, so that they have a non-load state of the radial roller bearing permanent contact with the bearing rings and thus a steady drive of the bearing cage and thus ensure the other rolling elements with kinematic speed.

In In practice, however, it has been shown that by their permanent Deformation undergoing a continuous bending cycle stress Hollow rollers of such radial roller bearings in terms of their resilience and fatigue potential vulnerabilities of the rolling bearing represent that for a reduced load capacity and a shortened one Life of the rolling bearing causal are. For example, it was determined that, especially on the inner surface of the Hollow rollers local Voltage peaks occur during continuous operation of the rolling bearing to cracks and finally led to the breakage of the hollow rollers. This was in particular due to the use of standard bearing steel for the Hollow rolls and their standard heat treatment to lead back at the hollow rollers by hardening at a temperature of 860 ° C, a quenching in the oil or Salt bath and a tempering at 190 ± 10 ° C throughout a martensitic structure obtained by its high hardness though for a high rollover resistance The hollow rollers but ensures by its low toughness and the absence of Residual compressive stresses, especially for the constant bending cycle stress on the inner circumferential surfaces is unsuitable. An obvious measure to avoid such Durability defects it would be, to dimension both the hollow rollers and the other rolling elements stronger, this would, however inevitably an enlargement of the entire storage space and an increase in production costs for the roller bearing have as a consequence.

Object of the invention

Based on the stated disadvantages of the known prior art, the invention is therefore based on the object to design a radial rolling bearing, in particular for the storage of waves in wind power transmissions, which while largely retaining its original performance characteristics, such as load capacity, space and life, to avoid Slip between the rolling elements and the bearing rings with hollow rollers equipped, which withstand the constant bending stress at any time and thus characterized by a high fatigue strength by increased fatigue strength and service life.

Description of the invention

According to the invention this Task at a radial rolling bearing solved according to the preamble of claim 1 such that the hollow rollers an application-specific bearing steel exist and through a heat treatment process are treated by the one in the inner and outer circumferential surfaces of the Hollow rollers their maximum load voltage superimposed, near-surface residual compressive stresses Inducible and by the other, the hollow rollers with a Hardness> 58 HRC on the inner shell surfaces on the one hand a high rollover resistance and on the other hand have such a continuous toughness that their outer circumferential surfaces a increased Bending fatigue strength> 650 Mpa have.

Of the The invention is therefore based on the finding that it is targeted Selection of the starting material for the hollow rollers and by a sophisticated heat treatment of the same is already possible, the to crack and finally to break the hollow rollers leading local To avoid voltage peaks in the inner circumferential surfaces of the hollow rollers and thus the bending fatigue and fatigue strength the hollow rollers and the load capacity and to significantly increase the life of such radial rolling bearings.

preferred Embodiments and developments of the invention formed radial roller bearing are in the subclaims described.

After that it is according to claim 2 a particularly advantageous way the required properties for the hollow rollers of the invention formed radial roller bearing easy and inexpensive to achieve when the hollow rollers of a through-hardening Bearing steel, For example, 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8 exist and treated by bainitizing. This also called intermediate level tempering Heat treatment method has proven to be particularly useful because it is an excellent combination for the steel materials mentioned the material properties hardness and toughness generated. In this heat treatment the hollow rollers are first austenitized in the same way as during standard hardening, this means, it is done first a heat treatment between 830 ° C and 885 ° C. The further treatment of the hollow rollers is then preferably such that quenched in a salt bath to a temperature between 220 ° C and 270 ° C and then at constant temperature for at least Stay for 4 hours until the microstructure transformation completed from austenite to bainite without formation of martensite is. Finally the hollow rollers are still cooled in the air. The resulting bainite structure then has a lot special properties; which is characterized by a high hardness between 54 and 62 HRC, through a maximum tensile strength between 1900 and 2300 MPa and a bending fatigue strength> 700 MPa, by an elongation at break> 5% and by relative small delays compared to standard hardening characterized in that at the same time a compressive residual stress up to -200 MPa acts. Bainitizing is a hardening heat treatment This method is particularly well suited for thin-walled hollow rollers.

A second option to achieve the required properties for the hollow rollers of the invention designed radial roller bearing consists according to claim 3 is that the hollow rollers of a through hardening Bearing steel, For example, from 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8 best and treated by induction hardening are. Induction hardening is known to the Surface hardening process, where it is in the near-surface Edge zone of the hollow rollers by a controlled sequence of heating and Quenching to a martensitic hardening and thus to a hardness increase comes in this area while the structure and the hardness in the core of Hohlrollenwandung remains unaffected. Serve with alternating applied copper coils, which geometrically the Hollow rollers are adapted to heat the hollow rollers by the copper coils generate a magnetic field that causes local heating eddy currents induced in the surface layer of the hollow rollers. The process then becomes controlled so that the surfaces of the hollow rollers up on one in dependence the depth of hardness to be achieved and toughness hardening temperature to be determined heat and immediately afterwards through a shower with water, oil or polymer solution be deterred. Finally are the hollow rollers to increase toughness again for Tempered for 1.5 to 2 hours at a temperature in the range between 160 ° C and 220 ° C, so that a fine hardening structure is created as a result a tensile strength between 2200 MPa and 2300 MPa, a bending fatigue strength> 650 MPa and a residual elongation at break between 5% and 25% depending on of the chosen basic structure and thus the strength and toughness having the untreated core material. Especially advantageous is during induction hardening the achievable compressive residual stress of -200 MPa to -400 MPa and the high achievable hardness between 60 HRC and 64 HRC at the functional surfaces of the hollow rollers.

Two further cost-effective Alternatives to achieve the required properties for the hollow rollers of the inventively designed radial roller bearing exist according to the claims 4 and 5 above In addition, that as a material for the hollow rollers either a by curing Bearing steel, For example, 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8, or a Case steel for Bearing applications, for example 17MnCr5, 20NiCrMo7, 18CrNiMo7-6 or 18NiCrMo14-6, chosen and the hollow rollers by carburizing in a furnace atmosphere with or be treated without nitrogen content.

at as case hardening known carburizing workpieces without nitrogen in the furnace atmosphere, the interior and outer surfaces of the Hollow rollers enriched with carbon by diffusion, a soft and tough Core to achieve at the same time hard surfaces. The case after austenitization and thermochemical surface treatment resulting martensite formation leads to an increase in volume, which in the carbon-rich surface layers higher than is in the low carbon core, so that on the surfaces of the Hollow roll build up advantageous compressive residual stresses, the on act against the hollow rollers acting tensile stresses. The diffusion treatment for the mentioned application steel grades takes place preferably at a temperature of 950 ° C, after which in polymer solution, Salt bath or oil quenched and then in the oven at 600 ° C up to 680 ° C for 3 to Annealed for 5 hours becomes. After a cool down At room temperature, the hollow rollers are then austenitizing again at 780 ° C up to 850 ° C heated, then quenched again in polymer solution, salt bath or oil and at 160 ° C up to 250 ° C to be tempered. The resulting structure of the hollow rollers then points a hardness on the functional surfaces between 58 HRC and 64 HRC, a tensile strength> 2100 MPa and a maximum bending fatigue strength> 700 MPa as well as a maximum Residual breaking elongation of 5% to 15% depending on the selected material on while on the surfaces the hollow rollers at the same time compressive stresses between -200 MPa and -400 MPa act.

at the carburizing known as carbonitriding of workpieces with Nitrogen content in the furnace atmosphere are considered a special kind case hardening In addition to carbon simultaneously small amounts of nitrogen in the Interior and exterior surfaces of the Hollow rollers diffused to the Reibverschleißwiderstand and the emergency running properties to improve the enriched surface layer and a higher tempering resistance across from case hardening to reach. The nitrogen acts as an alloying element in this process in the surface layers or surfaces the hollow rollers, through which their edge hardenability is improved. By carbonitriding by hardening Rolling bearing steels are included appropriate combination of material and heat treatment parameters in the boundary layers as well Compressive stresses up to -100 Generates MPa and defined retained austenite contents between 8% and 25%, which are stabilized by the nitrogen introduced and as Plasticity carrier at the same time an increased tolerance against rolling over hard particles. Austenitization and diffusion takes place preferably at temperatures of 840 ° C to 900 ° C while maintaining workpiece and hardening depth-dependent holding times of up to 6 hours, after which at hardening temperatures between 840 ° C and 870 ° C either martensitic or at 180 ° C up to 260 ° C bainitic quenched for about 4 hours. The resulting structure the hollow rollers then looks similar as in case hardening one Hardness the functional surfaces between 58 HRC and 64 HRC, a tensile strength> 2100 MPa and a maximum bending fatigue strength> 700 MPa as well as a maximum residual breaking strain of> 3 % dependent on of the chosen Material on.

When More options to achieve the required properties for the hollow rollers of the invention designed radial roller bearing it will be through the claims 6 and 7 finally nor suggested that as a material for the hollow rollers a vacuum melted or an electroslag remelted bearing steel of high purity or also a powder-metallurgical or spray-compacted bearing steel selected and the hollow rollers either by a standard heat treatment or as already described by bainitizing or induction hardening or by case hardening or carbonitriding are treated. The use of such high quality Rolling steel causes that already with a standard heat treatment otherwise achievable only with the special heat treatment process increase the bending fatigue strength of the hollow rollers occurs or when using this special heat treatment process is increased again.

The inventively embodied radial roller bearing thus has the advantage over the known from the prior art radial rolling bearings that it is equipped with largely retaining its original performance characteristics, such as load capacity, space and life, to prevent slippage between the rolling elements and the bearing rings with hollow rollers which are characterized by a targeted selection of their starting material and by a mature heat treatment of the same by a high rollover resistance and high tensile strength with high toughness and thus by increased fatigue strength and service life. These advantages also occur when the rolling elements not be guided by a bearing cage, but lead yourself as in full complement bearings.

Brief description of the drawings

A preferred embodiment of the inventively designed radial roller bearing will be explained in more detail with reference to the accompanying drawings. there demonstrate:

1 a side view of an inventively designed Ra dialwälzlagers;

2 the cross section AA by the inventively embodied radial roller bearing after 1 ;

3 a graphic representation of the lifetime increase of the inventively designed radial roller bearing after 1 ,

Detailed description of the drawings

From the representations of 1 and 2 is clearly a suitable for the storage of waves in wind power transmissions radial rolling bearings 1 which in known manner from an outer bearing ring 2 with an inner career 3 and an inner bearing ring arranged coaxially therewith 4 with an outer career 5 as well as a variety between the bearing rings 2 . 4 on their careers 3 . 5 rolling rolling elements 6 which passes through a bearing cage 7 be held in the circumferential direction at regular intervals to each other. It is also clear from the drawings that in the illustrated radial roller bearing 1 to prevent slippage between the rolling elements 6 and the bearing rings 2 . 4 three evenly distributed on the circumference rolling elements 6 by hollow rollers 8th are replaced, which have a slightly larger diameter and a lower modulus of elasticity than the other rolling elements 6 have to in the load-free state of the radial roller bearing 1 a constant contact with the bearing rings 2 . 4 and thus a steady drive of the bearing cage 7 and thus the remaining rolling elements 6 ensure with kinematic speed.

So that the hollow rollers 8th in the bearing operation withstand the constant Biegewechselbeanspruchungen at any time and are characterized at the same time high rollover resistance by increased fatigue strength and service life, these consist in accordance with the invention on the one hand from an application-specific bearing steel and on the other hand treated by a heat treatment process by the one hand in the inner and outer circumferential surfaces 9 . 10 the hollow rollers 8th whose maximum load voltage superimposed, near-surface residual compressive stresses are inducible and by the other hand, the hollow rollers 8th with a hardness> 58 HRC on their inner circumferential surfaces 9 have a high rollover resistance and such a toughness that their outer circumferential surfaces 10 have an increased bending fatigue strength> 650 Mpa.

In a particularly cost effective manner, the hollow rollers 8th This consists of a hardening bearing steel such as 100Cr6 and are heat treated by Bainitisieren. In this heat treatment, the hollow rollers are first austenitized by a heat treatment at temperatures between 830 ° C and 885 ° C and then quenched in a salt bath to a temperature between 220 ° C and 270 ° C, in which they at least 4 hours to the structural transformation of Staying austenite after bainite. Finally, the hollow rolls are cooled in the air, so that the resulting bainite structure by a high hardness between 54 and 62 HRC, by a maximum tensile strength between 1900 and 2300 MPa and a bending fatigue strength> 700 MPa, by an elongation at break> 5% and by relatively low delays compared to the standard hardnesses and in the hollow rollers 8th at the same time a compressive residual stress up to -200 MPa acts. Through the graphic representation in 3 it is clear that the hollow rollers according to the invention shown by a dash-dotted curve 8th By targeted selection of their starting material and by the special heat treatment with a dashed line limit load C / P of 3.33 can be permanently operated, which is about 30% higher than the also shown in dashed lines limit load C / P of 4.3 by a continuous curve shown hollow rollers with standard heat treatment.

1

radial bearings

2

outer bearing ring

3

inner career

4

internal bearing ring

5

outer career

6

rolling elements

7

bearing cage

8th

hollow rollers

9

Inner lateral surfaces

10

Outer shell surfaces

C / P

relative burden

Claims (7)

Radial rolling bearing, in particular for supporting shafts in wind power transmissions, which essentially consists of an outer bearing ring ( 2 ) with an inner raceway ( 3 ) and a coaxial with this inner bearing ring ( 4 ) with a äuße career ( 5 ) and a plurality between the bearing rings ( 2 . 4 ) on their careers ( 3 . 5 ) rolling rolling elements ( 6 ) passing through a bearing cage ( 7 ) are held in the circumferential direction at equal distances from each other, wherein to avoid slippage between the rolling elements ( 6 ) and the bearing rings ( 2 . 4 ) a plurality of evenly distributed on the circumference of rolling elements ( 6 ) by hollow rollers ( 8th ), which have a slightly larger diameter and a lower modulus of elasticity than the other rolling elements ( 6 ) in order, in the load-free state of the radial rolling bearing ( 1 ) a permanent contact with the bearing rings ( 2 . 4 ) and thus a steady drive of the bearing cage ( 7 ) and thus the other rolling elements ( 6 ) with kinematic speed, characterized in that the hollow rollers ( 8th ) are made of an application-specific bearing steel and are treated by a heat treatment process, by the one hand in the inner and outer circumferential surfaces ( 9 . 10 ) of the hollow rollers ( 8th ) whose maximum load voltage superimposed, near-surface residual compressive stresses are inducible and by the other the hollow rollers ( 8th ) with a hardness> 58 HRC at their inner circumferential surfaces ( 9 ) on the one hand have a high rollover resistance and, on the other hand, have such a continuous toughness that their outer circumferential surfaces ( 10 ) have an increased bending fatigue strength> 650 Mpa. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) are preferably made of a hardening bearing steel, for example of 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8, and are treated by Bainitisieren. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) are preferably made of a hardening bearing steel, for example 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8, and are treated by induction hardening. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) preferably consist of a hardening bearing steel, for example of 80Cr2, 100Cr6, 100CrMn6 or 100CrMnMo8, and are treated by carburizing in an oven atmosphere with or without nitrogen. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) preferably consist of a case hardening steel for rolling bearing applications, for example of 17MnCr5, 20NiCrMo7, 18CrNiMo7-6 or 18NiCrMo14-6, and are treated by carburizing in an oven atmosphere with or without nitrogen content. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) are made of a vacuum-melted or electroslag remelted high-purity bearing steel treated by standard heat treatment or by bainitizing or induction hardening or case hardening or carbonitriding. Radial rolling bearing according to claim 1, characterized in that the hollow rollers ( 8th ) are made of a powder metallurgy or spray-compacted bearing steel and are treated by a standard heat treatment or by bainitizing or induction hardening or case hardening or carbonitriding.