JP2015059645A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage of a rolling body caused by edge stress while avoiding that the rolling body rides on a shoulder even if a large radial load by FBO acts, as a rolling bearing for jet engine main shaft of an aircraft.SOLUTION: A raceway face 13 of an inner ring 11, or a raceway face 14 of an outer ring 12, or both of them are formed at two different groove curvature ratios, inflection points of the raceway faces are located at both sides at the outside of a contact ellipse E at a normal operation, and the groove curvature ratios at the outside 14b of the raceway faces at both the sides are the same, and smaller than the groove curvature ratios at the inside 14a of the raceway faces.

Description

  The present invention relates to a rolling bearing used for a main shaft of an aircraft jet engine, particularly a front fan support.

  The rolling bearing that supports the front fan may be damaged by receiving an excessive radial load due to FBO (Fan Blade Off) due to disturbance such as inhaling birds during flight. After the FBO, the aircraft needs to land safely at the nearest airport, but if the main shaft of the jet engine stops rotating, the fan will become air resistance and hinder the flight. It is required to do.

  In order to cope with such a situation, as a rolling bearing for the main shaft of a jet engine, an elastic member and a vibration damping part are interposed between the bearing outer ring and the casing, and an excessive load is applied to the rolling element even when a large radial load is applied. There is known a structure that does not act (Patent Document 1).

JP 2008-138704 A

  However, the rolling bearing disclosed in Patent Document 1 is not sufficient in reducing the load applied to the rolling element during FBO, and has a complicated structure, high manufacturing cost, and a large space. There is. In addition, when an excessive radial load is applied to the rolling elements, the contact surface pressure between the rolling elements and the raceway surface increases, and the rolling elements may be deformed. Furthermore, the deformed rolling element rides on the shoulder portion of the race and may be damaged by the edge stress generated at that time.

  Accordingly, the present invention has an object to prevent the rolling element from being deformed or riding on the shoulder when an excessive radial load due to FBO or the like is applied, and to eliminate the risk of the rolling element being damaged. To do.

In order to solve the above problems, the present invention comprises an inner ring, an outer ring, a large number of rolling elements interposed between the raceway surfaces of these raceways, and a cage that holds the rolling bodies at a constant interval, Each bearing ring is a rolling bearing having a shoulder of a constant width along the raceway surface, and the raceway surface of either the inner ring or the outer ring or both of them is two different grooves when viewed from the axial direction of the bearing. The inflection point is on both sides outside the contact ellipse with the center of the contact ellipse during normal operation, and the groove curvature ratio of both raceway surfaces outside the inflection points on both sides is the same. The groove curvature ratio of both raceway surfaces outside the inflection points on both sides is smaller than the groove curvature ratio of the raceway surface inside the raceway both inflection points including the contact ellipse.
The groove curvature ratio is defined as groove radius of curvature / ball radius.

  When the rolling bearing having the above configuration is used for a front fan support bearing of an aircraft jet engine main shaft and receives an excessive radial load by FBO or the like, the groove curvature ratio on the outer surface of the raceway is changed to the groove on the inner side of the raceway surface. By making it smaller than the curvature ratio, the rolling element can be received outside the raceway surface, the deformation of the rolling element can be reduced, and the risk of breakage of the rolling element can be reduced. Further, since the generated contact ellipse does not reach the shoulder, it is possible to avoid the rolling element from riding on the shoulder, and the risk of damage to the rolling element due to edge stress can be reduced.

  As described above, when the rolling bearing of the present invention is used as a front fan support bearing for an aircraft jet engine main shaft, even if FBO occurs, the rotation can continue without causing damage to the bearing. You can navigate safely and land at the nearest airport.

FIG. 1 is a partially enlarged cross-sectional view of the rolling bearing of the first embodiment. FIG. 2 is a partially enlarged cross-sectional view of FIG. FIG. 3 is a partially enlarged cross-sectional view of a rolling bearing of a comparative example.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Embodiment 1]

  The rolling bearing according to the first embodiment shown in FIG. 1 includes an inner ring 11, an outer ring 12, a plurality of balls 15 as a rolling element interposed between the opposed raceway surfaces 13 and 14, and each ball 15. It is a ball bearing constituted by a cage 16 held at regular intervals. The inner ring 11 is a combination of split inner rings 11a and 11b divided in the axial direction. The inner ring 11 is combined with the outer ring 12, and the ball 15 is a three-point contact ball bearing supported by these three members. The reason for using a three-point contact ball bearing is that if the fan stops due to an engine failure or the like, an axial load in the direction opposite to that of normal operation may be applied to the bearing.

  The inner ring 11 is used as a rotating side and the outer ring 12 is used as a stationary side, and the cage 16 is guided in sliding contact with the outer ring 12.

  On the both sides in the axial direction of the raceway surfaces 13 and 14 of the inner ring 11 and the outer ring 12, shoulder portions 17 and 18 having a certain width are provided.

The raceway surface 14 of the outer ring 12 has a raceway surface 14a (referred to as a raceway inner surface 14a) required for normal operation in a range from the bottom surface to the contact ellipse in normal operation, and continuously from the contact ellipse outside in normal operation. The raceway outer surface 14b is formed on both sides of the track surface, and the raceway inner surface 14a and the raceway outer surface 14b have different groove curvature ratios.
Here, “normal operation” means a state in which the jet engine is operating normally.

  The positions of the inflection points on the raceway inner surface 14a and the raceway outer surface 14b are symmetrical with respect to the axial center of the bearing.

Groove curvature ratio _{X 1} of the raceway surface inner 14a is provided between the groove curvature ratio _{X 2} of track surface outer 14b, relationship 1.00 ≦ _X 2 _{<X 1} ≦ 1.12 must be established. The reason is as follows.

That is, when it is less than 1.00, when a predetermined load is applied to the bearing during normal operation, there is a problem that the raceway outer surface 14b and the ball 15 interfere with each other. Further, when X ₂ > X ₁ , there is no interference with the ball 15, but there is a problem that the deformation amount of the ball 15 becomes large when an excessive radial load is applied. Further, when X ₁ > 1.12, the contact surface pressure becomes excessive and the bearing life is shortened. Eventually, when the relationship of 1.00 ≦ X ₂ <X ₁ ≦ 1.12 is satisfied, there is no interference between the ball 15 and the outer raceway surface 14b, and the deformation of the ball 15 is suppressed.

  Since the raceway inner surface 14a is a portion where the balls 15 roll in a normal operation, super polishing is performed as usual. On the other hand, the raceway outer surface 14b is a portion that the ball 15 contacts only when an excessive radial load is applied, and is not a surface that rolls during normal operation, so it is rougher than the raceway inner surface 14a. Well, therefore, there is no need for super polishing.

  In order to facilitate the super polishing of the raceway inner surface 14a, it is desirable to provide a groove-like Nusumi shape 22 at the boundary between the raceway inner surface 14a and the raceway outer surface 14b. The Nusumi shape 22 acts as a relief when polishing.

  Further, it is desirable that the corner portion 23 formed by the raceway outer surface 14b and the shoulder portion 18 is subjected to R chamfering. This is to eliminate the risk of edge stress occurring between the shoulder 18 and the ball 15 when an excessive radial load is applied.

  The retainer 16 may be made of a metal material such as SAE 4340 and subjected to silver plating on the surface.

  Further, the inner ring 11 and the outer ring 12 can use M50 which is heat-resistant bearing steel and M50NiL which is surface hardened steel.

  The ball 15 can use M50 or ceramics. As the ceramic, one containing silicon nitride, alumina, zirconia, or silicon carbide as a main component can be used.

  Here, FIG. 2 shows a three-point contact ball bearing conventionally known as a comparison target. In the same manner as described above, this ball bearing has a plurality of single-row balls 15 as rolling elements interposed between the inner ring 11 and the outer ring 12, and the raceway surfaces 13 and 14 opposed to each other, and each ball 15. It is a ball bearing comprised by the holder | retainer 16 arranged in this. The inner ring 11 is a combination of split inner rings 11a and 11b divided in the axial direction. The inner ring 11 is combined with the outer ring 12, and the ball 15 is a three-point contact ball bearing supported by these three members.

  The structure is the same as that of the first embodiment up to the point where shoulder portions 17 having a constant width are provided on both sides of the raceway surface 13 of the inner ring 11. However, the three-point contact ball bearing to be compared is different in that the raceway surface 14 of the outer ring 12 is formed with two different groove curvature ratios.

As is clear from the comparison with the comparison object, in the case of the first embodiment, the track surface outer side 14b is provided continuously to the track surface inner side 14a. Furthermore has set groove curvature ratio _{X 2} of track surface outer 14b to _{1.00 ≦ X 2 <X 1 ≦} 1.12. For this reason, since the ball 15 is received by the outer raceway surface 14b when it is used for the front fan support portion of the jet engine main shaft of an aircraft and receives an excessive radial load due to FBO, the contact surface pressure is excessive. Is suppressed, and deformation is prevented. Further, it is possible to prevent the ball 15 from climbing onto the shoulder 18 and to prevent the ball 15 from being damaged by the edge stress.

  In the above-described first embodiment, the case where two different groove curvature ratios are provided in the outer ring 12 has been described. However, the present invention may be applied only to the inner ring 11 or both the outer ring 12 and the inner ring 11.

11 Inner rings 11a, 11b Split inner ring 12 Outer ring 13 Race surface 14 Race surface 14a Race surface inside 14b Track surface outside 15 Ball 16 Cage 17 Shoulder 18 Shoulder 21 Guided surface 22 Nusumi shape 23 Corner E E Contact ellipse in normal operation

Claims (6)

  An inner ring, an outer ring, a large number of rolling elements interposed between the raceway surfaces of these raceways, and a cage that holds the rolling bodies at regular intervals, each raceway having a constant width along the raceway surface. In a rolling bearing having a shoulder, the raceway surface of either the inner ring or the outer ring or both of them has two different groove curvature ratios as viewed from the axial direction of the bearing, and the inflection point is usually Centering on the contact ellipse during operation, the groove curvature ratios of both raceway surfaces outside the inflection points on both sides of the contact ellipse are the same, and outside the inflection points on both sides. A rolling bearing characterized in that the groove curvature ratio of both raceway surfaces is smaller than the groove curvature ratio of the raceway surface inside the raceway both inflection points including the contact ellipse.   The rolling bearing according to claim 1, wherein the position of the inflection point is symmetric when viewed from the axial center of the bearing. Claims, characterized in that between the groove curvature ratio X ₂ of the raceway surface outside the groove curvature ratio X ₁ of the inner said track surface, the relationship of 1.00 ≦ X _{2 <X 1} ≦ 1.12 is satisfied The rolling bearing according to 1 or 2.   The rolling bearing according to any one of claims 1 to 3, wherein an R chamfering process is performed on a corner portion formed by the shoulder portion and the outer raceway surface.   5. The rolling bearing according to claim 1, wherein the rolling element is a three-point contact ball bearing that is contact-supported by three members, an inner ring divided in the axial direction and an outer ring. . The rolling bearing according to claim 1, wherein the rolling bearing is used as a support portion of a front fan in an aircraft jet engine main shaft.

Images