The disclosure relates to a cage for a roller bearing for rotationally mounting a high-speed shaft. The disclosure also relates to a roller bearing with the aforementioned cage. In particular, the cage is provided to be used in a roller bearing of a turbocharger. A high-speed shaft involves a shaft that has at least a speed of 30,000 revolutions per minute. In particular, a high-speed shaft involves a spindle shaft or a rotor shaft of a turbocharger.
Roller bearings comprise rolling bodies, as well as an outer ring and, if necessary, an inner ring, on each of which a roller track is formed. The rolling bodies roll between the outer and inner rings on the roller tracks and are spaced apart by means of a cage with rolling body cavities distributed over its circumference. The cage can be guided on the rolling bodies or on one of the rings, wherein in turbochargers the cage is usually guided on the outer ring, but it can also be guided on the inner ring. The special operating conditions of a turbocharger pose special challenges on the design of the bearings. The rotor shaft rotates at a speed which, due to its absolute height and its fluctuations, transfers high loads into the bearing. Turbochargers are operated at a constantly changing speed, which can reach up to 300,000 revolutions per minute at peak times. In addition, high operating temperatures of up to 400° C. prevail, especially near the turbine wheel, which affect the lubricant and the materials used.
DE 10 2014 213 256 B3 discloses a double row angular contact ball bearing of a turbocharger comprising an angular contact ball bearing with an outer ring and a cage. Rolling body cavities are arranged along the circumference of the cage. Furthermore, along only one end of the outer ring, a cage guide surface is extending, which forms a pair of sliding surfaces with a surface on the inner circumference of the outer ring. The contour of the cage is produced by means of a cutting process, for example by rotation. In this way, a wide range of different contours can be implemented, to avoid unnecessary wear and tear.
It is one objective of the present disclosure to further develop a cage for a roller bearing for rotatably supporting a high-speed shaft, in particular by reducing the production costs of the cage and shortening the production time of the cage.
An inventive cage for a roller bearing for rotatably supporting a high-speed shaft, in particular a shaft for a turbocharger, comprises two cage rings and a plurality of connecting elements and cavities for rolling bodies, the connecting elements extending axially between the cage rings, and the cavities being arranged tangentially (or circumferentially) between the connecting elements. Furthermore, the cage consists of a metal material and is essentially configured by using metal forming technology, two tangentially adjacent ends of the cage being joined together. Thus, the cage is configured in the form of a weld-bending cage. The cage is made of profiled material by forming, in particular by rolling, the cavities being produced by punching. In particular, it is possible to produce different profiles of a cage cross section. It is also possible to use different rolling bodies, in particular balls, needles or rollers. Furthermore, the cavities can be punched out as required, wherein the contact surface between the rolling body and the cage can be embossed, which results in strain hardening. Preferably, the connecting elements can be configured in asymmetric manner. Finally, tangentially adjacent ends of the cage are joined by welding, thus forming the ring-shaped cage. A possible imbalance caused by the welding seam can be compensated by a specific adjustment of the formation of the cavities.
In an embodiment, the respective connecting element has at least one contact surface for guiding the respective rolling body of the roller bearing. In particular, the respective connecting element has multiple contact surfaces for guiding the respective rolling body. In particular, the respective contact surface is configured in the form of a tangential embossing.
In an embodiment, an outer circumferential surface of the cage is partially attached with an outer ring of the roller bearing. Together with the outer ring of the roller bearing, the outer circumference of the cage forms a sliding surface, which is used to guide the cage.
Alternatively, or in addition, an inner circumferential surface of the cage is attached at least partially with an inner ring of the roller bearing. If, in addition to the outer circumferential surface of the cage, the inner circumferential surface of the cage is attached at least partially with a respective ring of the roller bearing, the stability of the cage is increased, but this also increases the frictional forces. However, it is also possible that the cage is attached neither with the inner ring nor with the outer ring of the cage but is guided only by the rolling body.
In an embodiment, a friction-minimizing and/or corrosion-resistant coating is at least partially formed on the surface of the cage. Preferably, the coating is configured as a silver coating, CVD or PVD coating. In particular, the silver coating is configured for dry-running properties when the cage starts on the respective ring. In particular, the friction-minimizing coating is only formed on the contact surfaces of the cage in relation to the respective ring of the roller bearing.
The disclosure includes the technical teaching that heat treatment is provided to adjust the structure and/or hardness of the cage. Advantageously, the cage is nitrocarburized or case-hardened. In particular, the cage is made of a weldable metal material, for example, C 15 or DC 03.
Subsequently, further description is provided in more detail together with the description of embodiments, using the figures in which identical or similar elements are provided with the same reference numerals. It is shown
According to
An outer circumferential surface of the cage 1 is partially attached with the outer ring 6 of roller bearing 2. The outer circumferential surface of the cage 1 is partially configured in spherical fashion to minimize a contact surface between the outer ring 6 and the cage 1.
All five embodiments of the inventive cage 1 were subjected to heat treatment to adjust the structure and hardness of cage 1. Furthermore, all five embodiments of the inventive cage 1 also show a friction-minimizing and corrosion-resistant coating 8 on the entire surface.
Number | Date | Country | Kind |
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10 2016 206 697.8 | Apr 2016 | DE | national |
This application is the U.S. National Phase of PCT/DE2017/100291 filed Apr. 11, 2017, which claims priority to DE 102016206697.8 filed Apr. 20, 2016, the entire disclosures of which are incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
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PCT/DE2017/100291 | 4/11/2017 | WO | 00 |