JP2012215257A - Three-point contact ball bearing and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a three-point contact ball bearing from hardly being damaged, even if fun blade off occurs when the three-point contact ball bearing is used for a gas turbine as an industrial machine or an aircraft and so on.SOLUTION: Stiffness near a groove bottom of a raceway surface 4 of an inner and outer ring is made to be lower than regions other than the groove bottom. Stiffness of regions with which the ball 3 of the raceway surface 4 contacts is reduced to easily deform in the fun blade off. When the stiffness at the regions other than the groove bottom of the raceway surface 4 of the inner and outer ring is set to approximately HRC60-HRC65, the stiffness near the groove bottom is set to HRC60 or lower.

Description

  The present invention relates to a three-point contact ball bearing, and more particularly to a three-point contact ball bearing used for gas turbines such as industrial machines and aircraft, and a manufacturing method thereof.

  A bearing used for a main shaft of a jet engine such as an aircraft mainly receives an axial load.

  Three-point contact ball bearings are suitable for use under conditions with a large axial load, but in the case of a fan blade off (hereinafter referred to as “FBO”) in a jet engine, compared to the axial load. Receive very large radial loads.

  When FBO occurs, it is necessary for the aircraft to land safely at the nearest airport. However, if the spindle stops rotating, the fan will become air resistance and hinder flight. Even if it happens, it is required to rotate at least.

  However, since the radial load during FBO is very large, there is a risk that the rolling elements will be damaged and the rotation of the bearing will be hindered.

  For this reason, in the invention of Patent Document 1, an excessive force is not applied to the rolling elements even when an elastic member and a vibration damping portion are provided on the outer ring of the bearing used for the main shaft of the jet engine and a large radial load is applied. I am doing so.

JP 2008-138704 A

  However, the method described in Patent Document 1 has problems that the effect of reducing the load applied to the rolling element during FBO is not sufficient, the structure is complicated, the manufacturing cost is high, and a large space is required.

  Accordingly, the present invention is intended to reduce the risk of rolling element breakage during FBO without complicating the structure of the bearing.

  In order to solve the above-described problems, the present invention reduces the hardness of a portion of the raceway surface that contacts the rolling element during FBO to facilitate deformation, and reduces the risk of damage to the rolling element when FBO occurs. It is a thing.

  That is, according to the present invention, the hardness in the vicinity of the groove bottom of the raceway surface of the inner and outer rings is made lower than the hardness other than the bottom of the groove, and the hardness of the portion where the rolling elements of the raceway surface contact during FBO is reduced. It is easy to do.

  In the present invention, when the hardness of the raceway surface of the inner and outer rings other than the groove bottom is about HRC60 to HRC65, the hardness near the groove bottom is set to HRC60 or less.

  When the inner and outer rings of the three-point contact ball bearing for the jet engine main shaft are formed of heat-resistant carburized steel M50NiL, the raceway surface near the groove bottom is set to about HRC45 of the base material hardness, and the hardness of the other portions is as usual. , HRC about 60-65. In the case of a three-point contact ball bearing for a jet engine main shaft, during normal operation where the axial load is mainly used, the raceway surface and the rolling element come into contact with each other with a relatively large contact angle, and the rolling element has a hardness of about 60 to 65 HRC. Therefore, it has the same life as a conventional three-point contact ball bearing for a jet engine main shaft.

At the time of FBO, the contact angle is close to 0 ° due to the effect of increasing radial load, and the raceway and the rolling element come into contact with each other near the bottom of the groove having a hardness of about HRC45. Since it is easy to deform | transform and the stress which generate | occur | produces on a contact surface is relieve | moderated, the failure risk of a rolling element is reduced.
The ease of deformation near the groove bottom of the raceway surface depends on the yield strength of the material. Table 1 shows the relationship between hardness and yield strength. As shown in Table 1, when the hardness is lowered from HRC60 to HRC45, the yield strength is reduced by about 35%, so reducing the hardness has an effect sufficient to reduce the risk of breakage of the rolling elements. Have.

  According to the present invention, even when the FBO occurs in the jet engine, the bearing can continue to rotate without being damaged, and the aircraft can safely navigate to and land at the nearest airport.

It is the schematic which shows the state of the load added to the three-point contact ball bearing at the time of normal driving | operation. It is the schematic which shows the state of the load added to a three-point contact ball bearing when FBO occurs. It is the schematic which shows an example of the formation method of the raceway surface of the three-point contact ball bearing which concerns on this invention. It is the schematic which shows the other example of the formation method of the raceway surface of the three-point contact ball bearing which concerns on this invention. It is the schematic which shows the other example of the formation method of the raceway surface of the three-point contact ball bearing which concerns on this invention.

  Embodiments of the present invention will be described below.

As shown in FIG. 1, the three-point contact ball bearing for the jet engine main shaft is mainly subjected to an axial load (Fa) during normal operation, and the raceway surface 4 of the inner ring 1 and the outer ring 2 and the rolling element 3 are in relatively large contact. Contact with angle α ₁ .

When FBO occurs, as shown in FIG. 2, the contact angle (α ₂ ) becomes close to 0 ° due to the effect of increasing the radial load (Fr).

For this reason, in the present invention, during normal operation, the raceway surfaces 4 of the inner ring 1 and the outer ring 2 in the range of the arrow a including the contact angle α ₁ that receives a large axial load are made to have a hardness of about HRC 60 to 65, It has the same life as a three-point contact ball bearing for a jet engine main shaft, and when FBO occurs, the hardness near the groove bottom in the range of arrow b including the contact angle (α ₂ ) that increases the radial load (Fr). The stress is reduced to about HRC45, the stress generated on the contact surface is relaxed, and the risk of breakage of the rolling element 3 is reduced.

The ball 3 can be formed of heat resistant steel or ceramic. When the balls 3 are formed of ceramic, the ceramic is mainly composed of one of silicon nitride, alumina, zirconia, and silicon carbide.
Next, as a method of forming the inner ring 1 and the outer ring 2 in which the hardness near the groove bottom of the raceway surface 4 is lower than the hardness other than the groove bottom, there are the following methods.

Example 1
As shown in FIG. 3 (a), heat-resistant carburized steel M50NiL is used as the material A for the inner and outer rings, leaving a lot of margin near the groove bottom as shown in FIG. 3 (b). Then, the raceway surface 4 is turned by using a turning tool 5, and thereafter, as shown in FIG. 3 (c), the material A having a lot of margin in the vicinity of the groove bottom is heat-treated, so that the carburized hardened layer 6 is formed. After the formation, as shown in FIG. 3 (d), when the carburized hardened layer 6 near the groove bottom is removed using a turning or grinding tool 7 near the groove bottom, as shown in FIG. A base material having an HRC of about 45 is exposed in the vicinity of the bottom, and a carburized hardened layer 6 having a hardness of about HRC 60 to 65 remains in a portion other than the vicinity of the groove.

  In this way, it is possible to form the inner ring 1 and the outer ring 2 in which the hardness near the groove bottom of the raceway surface 4 is lower than the hardness other than the groove bottom.

(Example 2)
As shown in FIG. 4 (a), heat-resistant carburized steel M50NiL is used as the material A for the inner and outer rings as in Example 1, and the raceway surface 4 is used as the turning tool 5 as shown in FIG. 4 (b). After the turning, when the heat treatment is performed, as shown in FIG. 4C, the vicinity of the groove bottom of the raceway surface 4 is masked by the masking agent 8 and then the orbit is performed by the heat treatment as shown in FIG. After forming the carburized hardened layer 6 on the surface 4 and then removing the masking agent 8 near the groove bottom using a turning or grinding tool 7 as shown in FIG. The base material of about HRC45 in the vicinity of the groove bottom that remains without being carburized is exposed.
In this way, it is possible to form the inner ring 1 and the outer ring 2 in which the hardness near the groove bottom of the raceway surface 4 is lower than the hardness other than the groove bottom.

(Example 3)
As shown in FIG. 5 (a), as material A of the outer ring, heat resistant carburized steel M50NiL or heat resistant steel M50 is used as in Example 1, and the raceway surface 4 is turned as shown in FIG. 5 (b). After turning with the tool 5, heat treatment is performed, and the entire raceway surface 4 is made to have a hardness of about HRC 60 to 65 as shown in FIG. 5C, and then a soft metal plating 9 is applied in the vicinity of the groove bottom. The hardness near the groove bottom can be made equal to the hardness of the soft metal. FIG. 5 is a process diagram for the case where heat-resistant carburized steel M50NiL is used.

  As the soft metal plating 9, silver plating can be used. Since the hardness of silver is 130 HV, the yield strength is reduced by about 81% from the raceway surface having a hardness of 694 HV (HRC 60), so that the method according to Example 3 has a sufficient effect. In addition, as the plating 9, copper plating can be used in addition to silver plating.

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Ball 4 Raceway 5 Turning tool 6 Carburizing hardening layer 7 Turning and grinding tool 8 Masking agent 9 Plating

Claims (13)

  In a three-point contact ball bearing consisting of inner and outer rings and a plurality of balls that roll between the inner and outer rings, the hardness near the groove bottom of the raceway surface of the inner and outer rings is lower than the hardness other than the groove bottom A three-point contact ball bearing.   The three-point contact ball bearing according to claim 1, wherein the hardness of the inner and outer ring raceways other than the groove bottom is about HRC60 to HRC65, and the hardness near the groove bottom is HRC60 or less.   The three-point contact ball bearing according to claim 1 or 2, wherein a carburized hardened layer by heat treatment is provided in a portion other than the groove bottom of the raceway surface of the inner and outer rings.   The three-point contact ball bearing according to claim 1, wherein the inner and outer rings are plated with a soft metal in the vicinity of the groove bottom of the raceway surface.   The three-point contact ball bearing according to claim 4, wherein the soft metal is silver or copper.   The three-point contact ball bearing according to any one of claims 1 to 4, wherein the inner and outer rings are formed of carburized steel.   The three-point contact ball bearing according to claim 6, wherein the carburized steel is heat-resistant carburized steel.   The three-point contact ball bearing according to any one of claims 1 to 7, wherein the ball is made of heat-resistant steel.   The three-point contact ball bearing according to any one of claims 1 to 7, wherein a material of the ball is one of silicon nitride, alumina, zirconia, and silicon carbide as a main component.   The three-point contact ball bearing according to any one of claims 1 to 9, which is used for a main shaft of a jet engine.   When forming the raceway surface of the inner and outer rings, turning to leave a lot of margin near the groove bottom, and then heat treating the material leaving a lot of margin near the groove bottom to form a carburized hardened layer, A method for manufacturing a three-point contact ball bearing, wherein an inner ring and an outer ring are formed by removing a carburized hardened layer near the groove bottom.   After turning the raceway surfaces of the inner and outer rings, when heat treatment is performed, the vicinity of the groove bottom of the raceway surface is masked by masking, and then a carburized hardened layer is formed on the raceway surface by heat treatment, and then the masking agent near the groove bottom is removed. A method for manufacturing a three-point contact ball bearing, characterized in that an inner ring and an outer ring are formed. After turning the raceway surface of the inner and outer rings, heat treatment is performed to form a carburized hardened layer on the entire raceway surface, and then the inner ring and the outer ring are formed by applying a soft metal plating near the groove bottom. A manufacturing method of a three-point contact ball bearing.

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