JP2013079680A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent surely exfoliation of silver plating applied on a guide surface of a steel-made cage, thereby extending a usable period in which seizure does not occur in a dry-run state.SOLUTION: On a guide surface 5a of a steel-made cage 5, a nickel-plated layer 6 having a linear expansion coefficient close to that of steel being a base material is formed as a base coat. Further, a silver-plated layer 7 is formed on the nickel-plated layer. Accordingly, the exfoliation of the silver plating applied on the guide surface 5a of the steel-made cage 5 is surely prevented and thereby a usable period in which seizure does not occur in a dry-run state can be extended.

Description

  The present invention relates to a rolling bearing that can be used without being seized for a predetermined time during a dry run.

  Like rolling bearings that support the main shafts of aircraft engines such as jets and helicopters, high safety is required, and the rotating shaft is supported at a high speed with a DN value (bearing inner diameter Dmm × rotational speed Nrpm) of about 2 million. Rolling bearings using steel cages are required to be usable without being seized, for example, for 30 seconds or more during an emergency dry run when the lubrication system fails and lubricant is no longer supplied to the bearing. Yes. In such a dry run state, it is known that seizure occurs at the sliding contact surface between the raceway and the guide surface of the steel cage before the rolling surface between the raceway and the rolling element. It has been.

  Rolling bearings using steel cages that can be used without being seized for a predetermined time during a dry run are subjected to silver plating on the guide surface of the cage that is in sliding contact with the bearing ring, and self-lubricating silver plating. Depending on the nature, there is one that prevents seizure between the guide surface of the cage and the race (see, for example, Patent Document 1).

JP 2005-344852 A

The rolling bearing with the silver-plated guide surface of the cage described in Patent Document 1 is plated when the temperature of the cage rises due to frictional heat generated by sliding contact between the guide surface of the cage and the raceway in a dry run state. The linear expansion coefficient (19.7 × 10 ⁶ / ° C.) of the silver of the layer is considerably larger than the linear expansion coefficient (12.5 × 10 ⁶ / ° C.) of the base steel. Becomes easy to peel. For this reason, the self-lubricating property of silver plating cannot be fully utilized, and seizure may occur at an early stage. In general, copper plating is often applied to the base of silver plating, but the linear expansion coefficient of copper (16.5 × 10 ⁶ / ° C.) is smaller than that of silver. Since it is still much larger than this, peeling of the silver plating due to such a difference in linear expansion coefficient cannot be sufficiently prevented.

  Therefore, the problem of the present invention is to reliably prevent peeling of the silver plating applied to the guide surface of the steel cage and to extend the usable time without causing seizure in the dry run state. is there.

  In order to solve the above-described problems, the present invention is configured such that a plurality of rolling elements are held by a steel cage between inner and outer races, and a silver plating is provided on a guide surface that is in sliding contact with the race of the cage. In the rolling bearing subjected to the above, a structure was adopted in which nickel plating was applied to the silver plating base of the guide surface of the cage.

That is, by applying nickel plating having a linear expansion coefficient (13.3 × 10 ⁶ / ° C.) close to the linear expansion coefficient of steel to the base of the silver plating on the guide surface of the steel cage, the steel cage The silver plating applied to the guide surface is reliably prevented from peeling off, and the usable time can be extended without causing seizure in the dry run state.

  The above-described rolling bearing is required for high safety and is suitable for supporting the main shaft of an aircraft engine that rotates at high speed.

  In the rolling bearing of the present invention, nickel plating having a linear expansion coefficient close to that of steel is applied to the base of the silver plating on the guide surface of the steel cage, so that it is applied to the guide surface of the steel cage. It is possible to reliably prevent the silver plating from being peeled off and extend the usable time without causing seizure in the dry run state.

a is a longitudinal sectional view showing an embodiment of a rolling bearing, b is a sectional view showing an enlarged guide surface of a cage of a 1 is a schematic longitudinal sectional view showing an engine of a jet aircraft using the rolling bearing of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this rolling bearing, as shown in FIG. 1A, the inner ring 2 is divided at the center of the raceway groove 2a, the ball 3 as a rolling element is at one point with the raceway groove 4a of the outer ring 4, and the raceway groove 2a of the inner ring 2. Is a three-point contact ball bearing 1 that is in contact at two points, and a steel cage 5 that holds the ball 3 in a pocket has a guide surface 5a on its outer diameter surface and inner diameter surfaces on both sides of the raceway groove 4a of the outer ring 4. You will be guided by. One of the divided inner rings 2 is provided with a flange 2b for drawing out the bearing.

  As shown in an enlarged view in FIG. 1B, a nickel plating layer 6 having a linear expansion coefficient close to that of the base steel is formed on the guide surface 5a of the steel cage 5 as a base. A silver plating layer 7 is formed thereon. The nickel plating layer 6 has a thickness of 5 μm or less, and the silver plating layer 7 has a thickness of about 25 to 50 μm.

  FIG. 2 shows a jet engine using the above-described three-point contact ball bearing 1. This engine is a turbofan engine, and includes a fan 11 that sucks air, a compressor 12 that compresses part of the sucked air, a combustion chamber 13 that injects fuel into the compressed air and burns, and a combustion The rotor 14 and the turbine 14 of the compressor 12 are attached to a main shaft 15 that is basically constituted by a turbine 14 that rotates at high speed with gas and is supported at two locations by the three-point contact ball bearing 1.

  As an example, a three-point contact ball bearing was prepared in which the guide surface of the steel cage was nickel-plated as a base and silver-plated thereon. As a comparative example, a three-point contact ball bearing was also prepared in which the guide surface of a steel cage was subjected to copper plating as a base and silver plating thereon. In both Examples and Comparative Examples, the thickness of the silver plating layer was 40 μm, and the thicknesses of the nickel plating layer and the copper plating layer as the respective bases were 4 μm. These bearing dimensions are an outer diameter of 200 mm, an inner diameter of 100 mm, and a width of 40 mm.

  Attach the three-point contact ball bearing of the above example and comparative example to the rotating shaft of the rotary tester, perform a dry run test that rotates at high speed for 30 seconds in a dry run state where the lubricating oil is shut off, and peel off the silver plating on the guide surface of the cage The presence or absence of was investigated. In addition, the dry run test was performed by changing the rotational speed in three stages according to the DN value.

  Table 1 shows the results of the dry run test. Table 1 also shows the peripheral speed of the cage guide surface at each DN value. In the comparative example in which the copper plating was applied to the base, no peeling was observed in the silver plating when the DN value was 1.6 million. However, when the DN value reached 1.85 million, peeling was observed in part of the silver plating. However, at 2.2 million, most of the silver plating was peeled off. On the other hand, in the example in which the nickel plating is applied to the base, the DN value is completely silver-plated until it reaches 2.2 million which exceeds the normal use range of 2 million although it supports the main shaft of the aircraft engine. No peeling was observed. From the above results, it was confirmed that the example with nickel plating on the base can reliably prevent the peeling of the silver plating even in a dry run state with a high DN value like the one supporting the main shaft of an aircraft engine. It was done.

  In the above-described embodiment, silver plating and nickel plating as a base are applied only to the guide surface of the cage, but these silver plating and nickel plating are also applied to other parts such as a pocket surface that holds the ball. Alternatively, it may be applied to the entire surface of the cage.

  In the above-described embodiment, the rolling bearing is a three-point contact ball bearing. However, the rolling bearing according to the present invention can be applied to other rolling bearings such as other ball bearings and roller bearings. It can also be applied to rolling bearings.

DESCRIPTION OF SYMBOLS 1 3 point | piece contact ball bearing 2 Inner ring 2a Track groove 2b 鍔 part 3 Ball 4 Outer ring 4a Track groove 5 Cage 5a Guide surface 6 Nickel plating layer 7 Silver plating layer 11 Fan 12 Compressor 13 Combustion chamber 14 Turbine 15 Main shaft

Claims (2)

  In a rolling bearing in which a plurality of rolling elements are held by a steel cage between the inner ring and outer ring raceway, and the guide surface in sliding contact with the raceway of the cage is silver-plated, the guide surface of the cage Rolling bearings characterized by nickel plating on the base of silver plating.   The rolling bearing according to claim 1, wherein the rolling bearing supports a main shaft of an aircraft engine.

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