JP2010001190A - Roller bearing for gas turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing for a gas turbine, the rolling body of which can be made lightweight and improved in heat resistance while restraining a track member from being damaged due to vibration or impact. <P>SOLUTION: A ball 13, which constitutes a three-point contact ball bearing 1 for supporting a main shaft of the gas turbine or a rotating member to be rotated by the rotation of the main shaft while being rotated freely together with the main shaft or a member arranged to be opposed to the rotating member, consists of a sintered compact containing the β sialon being a main component, which is shown by compositional formula: Si<SB>6-z</SB>Al<SB>z</SB>O<SB>z</SB>N<SB>8-z</SB>and satisfies 0.1≤z≤3.5, and impurities of the remainder. The ball 13 has 180-270 GPa Young's modulus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolling bearing for a gas turbine, and more specifically, to a rolling bearing for a gas turbine provided with a component made of a sintered body containing β sialon as a main component.

  The gas turbine apparatus has a mechanism for rotating a turbine having a main shaft by expansion energy of combustion gas generated by combustion of fuel. And the main shaft of the turbine is rotatably supported by a main shaft bearing which is a rolling bearing for a gas turbine with respect to a member arranged to face the main shaft. Moreover, the rotational energy of the main shaft of the turbine is extracted to the outside through a reduction gear included in the gas turbine device. Inside the speed reducer, rotating members such as various gears rotate, and the rotating member is a gas turbine rolling bearing with respect to a member arranged to face the rotating member. It is supported rotatably by.

  Here, the main shaft and the rotating member inside the speed reducer rotate at an extremely high speed. Therefore, high durability is required for a gas turbine rolling bearing in a high-speed rotation environment. On the other hand, for example, a rolling bearing capable of maintaining rotation for a predetermined time even when the supply of lubricant is stopped has been proposed (see, for example, Patent Document 1).

  Further, in a rolling bearing for a gas turbine used in a high-speed rotating environment, the rolling element is required to be light in weight in order to reduce the centrifugal force acting on the rolling element constituting the rolling bearing for the gas turbine. Further, the main shaft bearing is used in a high temperature environment due to the combustion of fuel in the gas turbine. Therefore, improvement in heat resistance is also required.

On the other hand, a rolling element made of silicon nitride may be employed as a rolling element for a gas turbine rolling bearing. Since silicon nitride has a smaller specific gravity than steel generally used as a material for the rolling elements, it can contribute to weight reduction of the rolling elements. In addition, since silicon nitride is excellent in heat resistance, such as a decrease in hardness at a high temperature compared with steel, it can contribute to improvement in heat resistance. Therefore, by adopting silicon nitride as the material for the rolling element of the gas turbine rolling bearing, the above-described rolling element can be reduced in weight and improved in heat resistance.
JP 2007-292117 A

  On the other hand, vibration and impact act on the rolling bearing for the gas turbine due to fuel combustion and turbine rotation. Here, silicon nitride has a characteristic that it has a Young's modulus greater than that of steel and is difficult to elastically deform. For this reason, the contact area between the rolling element made of silicon nitride and the raceway member is smaller than the rolling element made of steel, and the contact surface pressure tends to increase. Therefore, when a rolling element made of silicon nitride is employed as the rolling element of the gas turbine rolling bearing, damage such as indentation is likely to occur in the race member due to the vibration and impact. If damage such as indentation occurs on the raceway member, it may cause premature seizure. That is, when a silicon nitride rolling element is used as a rolling element for a gas turbine rolling bearing, there is a problem that the raceway member is easily damaged due to vibration or impact.

  Therefore, an object of the present invention is to provide a rolling bearing for a gas turbine that can achieve reduction in the weight of the rolling element and improvement in heat resistance while suppressing damage to the raceway member due to vibration or impact. is there.

  A rolling bearing for a gas turbine according to the present invention rotates a main shaft of a gas turbine or a rotating member that rotates by receiving the rotation of the main shaft with respect to a member arranged to face the main shaft or the rotating member. It is a rolling bearing for a gas turbine that is freely supported. This gas turbine rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And the rolling element consists of ceramics which can suppress the impact with respect to a track member compared with the case where it consists of silicon nitride. More specifically, for example, the rolling element is made of ceramics having a Young's modulus smaller than that of silicon nitride.

  According to the rolling bearing for a gas turbine of the present invention, since damage to the race member is suppressed even when an impact is applied, the rolling element is reduced in weight and heat resistance while suppressing damage to the race member due to vibration or impact. It is possible to provide a rolling bearing for a gas turbine capable of achieving improvement in performance.

  A rolling bearing for a gas turbine according to an aspect of the present invention is directed to a main shaft of a gas turbine or a rotating member that is a member that rotates in response to the rotation of the main shaft with respect to a member that is disposed so as to face the main shaft or the rotating member. It is a rolling bearing for a gas turbine that is rotatably supported. This gas turbine rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And a rolling element is comprised from the sintered compact which has (beta) sialon as a main component and consists of remainder impurities.

  A rolling bearing for a gas turbine according to another aspect of the present invention relates to a main shaft of a gas turbine or a rotating member that is a member that rotates in response to the rotation of the main shaft with respect to a member that is disposed so as to face the main shaft or the rotating member. It is a rolling bearing for a gas turbine that is rotatably supported. This gas turbine rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And a rolling element is comprised from the sintered compact which has (beta) sialon as a main component and consists of a remainder sintering auxiliary agent and an impurity.

In a rolling bearing for a gas turbine according to one aspect of the present invention, a β sialon sintered body (sintered body containing β sialon as a main component), which is a lightweight ceramic with excellent heat resistance, is employed as a rolling element. Yes. Therefore, weight reduction and heat resistance improvement of the rolling elements are achieved. Further, the β sialon sintered body has a Young's modulus smaller than a sintered body made of a general ceramic such as silicon nitride (Si ₃ N ₄ ) or alumina (Al ₂ O ₃ ). Therefore, it is possible to suppress damage to the track member due to vibration and impact caused by the high Young's modulus. As described above, according to the rolling bearing for a gas turbine in one aspect of the present invention, it is possible to reduce the weight of the rolling element and improve the heat resistance while suppressing damage to the raceway member due to vibration or impact. Therefore, it is possible to provide a rolling bearing for a gas turbine capable of achieving the above.

  A gas turbine rolling bearing according to another aspect of the present invention basically has the same configuration as that of the gas turbine rolling bearing according to one aspect of the present invention, and exhibits the same effects. However, the gas turbine rolling bearing according to another aspect of the present invention is different from the gas turbine rolling bearing according to one aspect of the present invention in that the sintered body contains a sintering aid. According to the rolling bearing for a gas turbine in another aspect of the present invention, the adoption of the sintering aid makes it easy to lower the porosity of the sintered body, and can ensure sufficient durability stably. A rolling bearing for a gas turbine can be easily provided.

  As the sintering aid, at least one of magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), rare earth element oxide, nitride, and oxynitride is employed. be able to. In order to achieve the same effect as that of the rolling bearing for gas turbine according to one aspect of the present invention, the sintering aid is desirably 20% by mass or less in the sintered body.

In the gas turbine rolling bearing, preferably, the β sialon is represented by a composition formula of Si _6-Z Al _Z O _Z N _8-Z and satisfies 0.1 ≦ z ≦ 3.5.

  The inventor has investigated in detail the relationship between the rolling fatigue life of a rolling element made of a β sialon sintered body and the composition of β sialon. As a result, the following knowledge was obtained. By adopting a production process including combustion synthesis, β sialon can be produced inexpensively with various compositions having a value of z (hereinafter referred to as z value) of 0.1 or more. In general, the hardness that greatly affects the rolling fatigue life hardly changes in the range of the z value of 4.0 or less that is easy to manufacture. However, when the relationship between the rolling fatigue life of the rolling element made of β sialon sintered body and the z value is investigated in detail, when the z value exceeds 3.5, the rolling fatigue life of the rolling element may decrease. I understood.

  More specifically, when the z value is in the range of 0.1 or more and 3.5 or less, the rolling fatigue life is substantially the same, and if the operation time of the rolling bearing exceeds a predetermined time, the surface of the rolling element is peeled off. Occurs and breaks. On the other hand, if the z value exceeds 3.5, the rolling elements are likely to be worn, resulting in a decrease in the rolling fatigue life. That is, it becomes clear that the failure mode of the rolling element made of β sialon changes with the composition having the z value of 3.5 as a boundary, and the rolling fatigue life decreases when the z value exceeds 3.5. It was. Therefore, in the rolling element made of β sialon sintered body, the z value is preferably set to 3.5 or less in order to ensure a stable and sufficient life. As described above, by making the β sialon satisfy 0.1 ≦ z ≦ 3.5, it is possible to provide a rolling bearing for a gas turbine that is inexpensive and excellent in durability.

In the gas turbine rolling bearing, preferably, the β sialon is represented by a composition formula of Si _6-Z Al _Z O _Z N _8-Z and satisfies 0.5 ≦ z ≦ 3.0.

  Thereby, the durability of the rolling bearing for gas turbine when vibration or impact is applied can be further improved.

  In the gas turbine rolling bearing, the Young's modulus of the rolling element is preferably 180 GPa or more and 270 GPa or less.

  When the Young's modulus of the rolling element increases, the strength of the material (β sialon sintered body) constituting the rolling element tends to increase. However, when the Young's modulus of the rolling element is increased, the rolling element is less likely to be elastically deformed, so that the contact area with the raceway member is reduced and the contact surface pressure is increased. As a result, the track member is likely to be damaged. On the other hand, when the Young's modulus of the rolling element becomes low, the rolling element is easily elastically deformed, so that the contact area with the raceway member increases and the contact surface pressure decreases. However, on the other hand, when the Young's modulus of the rolling element becomes low, the strength of the material constituting the rolling element tends to decrease. For this reason, the Young's modulus of the rolling element needs to be within a range in which a balance between the strength of the material constituting the rolling element and the reduction of the contact surface pressure between the race members can be secured.

  More specifically, when the Young's modulus of the rolling element made of β sialon sintered body is less than 180 GPa, the influence of the strength reduction of the material constituting the rolling element exceeds the effect of reducing the contact surface pressure, and the rolling element rolling Dynamic fatigue life is reduced. In addition, as the contact area with the raceway member increases, the frictional force acting between the raceway member and the bearing torque increases. Therefore, the Young's modulus of the rolling element made of the β sialon sintered body is preferably 180 GPa or more, and more preferably 220 GPa or more.

  On the other hand, if the Young's modulus of the rolling element made of β sialon sintered body exceeds 270 GPa, the effect of increasing the contact surface pressure exceeds the effect of increasing the strength of the material constituting the rolling element, and the indentation is formed on the rolling surface of the race member. Damage is likely to occur. Therefore, the Young's modulus of the rolling element made of the β sialon sintered body is preferably 270 GPa or less, and preferably 260 GPa or less.

  In the gas turbine rolling bearing, the race member may be made of steel. In this case, the surface hardness of the track member is preferably HV680 or more. Thereby, damage to the track member when vibration or impact is applied can be suppressed.

  In the above-described rolling bearing for gas turbine, preferably, the rolling element has a dense layer that is a denser layer than the inside in a region including a rolling surface that is a surface in contact with the race member.

  In the rolling element made of the above-described β sialon sintered body, the denseness greatly affects the rolling fatigue life. On the other hand, according to the said structure, a rolling fatigue life improves because the dense layer which is a layer denser than the inside is formed in the area | region containing a rolling surface. As a result, it is possible to provide a gas turbine rolling bearing capable of stably ensuring sufficient durability.

  Here, the high-density layer is a layer having a low porosity (high density) in the sintered body, and can be investigated as follows, for example. First, the rolling element is cut in a cross section perpendicular to the surface of the rolling element made of β sialon sintered body, and the cross section is mirror-wrapped. Thereafter, the mirror-wrapped cross section is photographed with oblique light (dark field) of an optical microscope at, for example, about 50 to 100 times and recorded as an image of 300 DPI (Dot Per Inch) or more. At this time, the white region observed as a white region corresponds to a region with high porosity (low density). Therefore, a region where the area ratio of the white region is low is denser than a region where the area ratio is high. The recorded image is binarized using a luminance threshold using an image processing apparatus, and then the area ratio of the white area is measured, and the density of the photographed area can be known from the area ratio. .

  That is, in the rolling bearing for a gas turbine, preferably, the sintered body is formed with a dense layer that is a layer having a lower area ratio of the white region than the inside in the region including the rolling surface. In addition, it is preferable to perform the said imaging | photography at 5 or more places at random, and to evaluate the said area ratio by the average value. Moreover, the area ratio of the said white area | region inside the said sintered compact is 15% or more, for example. In order to further improve the rolling fatigue life of the rolling element made of β sialon sintered body, the dense layer preferably has a thickness of 100 μm or more.

  In the rolling bearing for a gas turbine, preferably, when the cross section of the dense layer is observed with oblique light of an optical microscope, the area ratio of the white region observed as a white region is 7% or less.

  By improving the denseness of the dense layer to such an extent that the area ratio of the white region is 7% or less, the rolling fatigue life of the rolling element made of the β sialon sintered body is further improved. Therefore, the durability of the rolling bearing for a gas turbine of the present invention can be further improved by the above configuration.

  Preferably, in the rolling bearing for a gas turbine, a highly dense layer that is a denser layer than the other regions in the dense layer is formed in the region including the surface of the dense layer.

  By forming a highly dense layer with higher density in the region including the surface of the dense layer, the durability against rolling fatigue of the rolling element made of β sialon sintered body is further improved, and the rolling bearing for gas turbine is improved. The lifetime can be further improved.

  In the rolling bearing for a gas turbine, preferably, when the cross section of the highly dense layer is observed with oblique light of an optical microscope, the area ratio of the white region observed as a white region is 3.5% or less.

  By improving the denseness of the highly dense layer to such an extent that the area ratio of the white region is 3.5% or less, the rolling fatigue life of the rolling element made of the β sialon sintered body is further improved. Therefore, the durability of the rolling bearing for a gas turbine of the present invention can be further improved by the above configuration.

  As is apparent from the above description, according to the rolling bearing for a gas turbine of the present invention, it is possible to reduce the weight of the rolling element and improve the heat resistance while suppressing damage to the raceway member due to vibration or impact. Therefore, it is possible to provide a rolling bearing for a gas turbine capable of achieving the above.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a configuration of a turbofan engine (aircraft gas turbine engine) that is a gas turbine provided with a rolling bearing for gas turbine according to the first embodiment of the present invention. With reference to FIG. 1, the structure of the turbofan engine in the present embodiment will be described.

  With reference to FIG. 1, a turbofan engine 70 includes a compression unit 71, a combustion unit 72, and a turbine unit 73. The turbofan engine 70 is disposed so as to surround the outer peripheral surface of the low-pressure main shaft 74 and the low-pressure main shaft 74 disposed from the compression section 71 through the combustion section 72 to the turbine section 73. 77.

  The compression unit 71 is connected to the low pressure main shaft 74 and surrounds the fan 75 having a plurality of fan blades 75A formed so as to protrude radially outward from the low pressure main shaft 74, and the combustion unit 72. A fan nacelle 76 extending toward the end and a compressor 81 arranged on the combustion portion 72 side when viewed from the fan 75 are included. The compressor 81 includes a low-pressure compressor 81A and a high-pressure compressor 81B disposed on the combustion unit 72 side when viewed from the low-pressure compressor 81A. The low pressure compressor 81A has a plurality of compressor blades 88 connected to the low pressure main shaft 74, projecting radially outward from the low pressure main shaft 74 side, and arranged side by side in a direction approaching the combustion unit 72 from the fan 75 side. Yes. The high pressure compressor 81B has a plurality of compressor blades 88 connected to the high pressure main shaft 77, projecting radially outward from the high pressure main shaft 77 side, and arranged side by side in a direction approaching the combustion unit 72 from the fan 75 side. is doing. Further, a core cowl 78 is disposed so as to surround the outer peripheral side of the low-pressure compressor 81A. The annular space between the core cowl 78 and the fan nacelle 76 constitutes a bypass channel 79.

  The combustion section 72 is connected to the high-pressure compressor 81B of the compression section 71, and includes a combustion chamber 82 having a fuel supply member and an ignition member (not shown). The turbine unit 73 includes a turbine 83 having a high-pressure turbine 83B and a low-pressure turbine 83A disposed on the opposite side of the combustion unit 72 when viewed from the high-pressure turbine 83B. Further, a turbine nozzle 84 for discharging the combustion gas in the turbine 83 to the outside is disposed on the opposite side of the low pressure turbine 83A from the high pressure turbine 83B. The low-pressure turbine 83A is connected to the low-pressure main shaft 74, has a plurality of turbine blades 87 that protrude radially outward from the low-pressure main shaft 74 side and are arranged side by side in a direction approaching the turbine nozzle 84 from the combustion chamber 82 side. ing. The high-pressure turbine 83B is connected to the high-pressure main shaft 77, protrudes radially outward from the high-pressure main shaft 77 side, and has a plurality of turbine blades 87 arranged side by side in a direction approaching the turbine nozzle 84 from the combustion chamber 82 side. Have.

  The low-pressure main shaft 74 and the high-pressure main shaft 77 that are main shafts of the turbofan engine 70 are rotatably supported by members that are opposed to the low-pressure main shaft 74 and the high-pressure main shaft 77 by rolling bearings 89. That is, the rolling bearing 89 is a gas turbine rolling bearing (main shaft bearing) that rotatably supports the main shaft of the gas turbine with respect to a member disposed so as to face the main shaft.

  Next, the operation of the turbofan engine 70 in the present embodiment will be described. Referring to FIG. 1, air on the side opposite to the combustion portion 72 as viewed from the fan 75, that is, on the front side of the turbofan engine 70 is surrounded by the fan nacelle 76 by the fan 75 rotating around the axis of the low-pressure main shaft 74. (Arrow α). A part of the taken-in air flows in the direction along the arrow β and is discharged to the outside through the bypass channel 79 as an air jet. This air jet becomes part of the thrust generated by the turbofan engine 70.

  On the other hand, the remaining portion of the air taken into the space surrounded by the fan nacelle 76 flows into the compressor 81 along the arrow γ. The air that has flowed into the compressor 81 is compressed by flowing inside the low-pressure compressor 81A having a plurality of compressor blades 88 rotating around the low-pressure main shaft 74 toward the high-pressure compressor 81B, and flows into the high-pressure compressor 81B. . Further, the air that has flowed into the high-pressure compressor 81B is further compressed by flowing toward the combustion chamber 82 through the inside of the high-pressure compressor 81B having a plurality of compressor blades 88 that rotate about the axis of the high-pressure main shaft 77, and enters the combustion chamber 82. Inflow (arrow δ).

  The air compressed in the compressor 81 and flowing into the combustion chamber 82 is mixed with fuel supplied into the combustion chamber by a fuel supply member (not shown) and then ignited by an ignition member (not shown). Thereby, combustion gas is generated in the combustion chamber 82. This combustion gas flows out of the combustion chamber 82 and flows into the turbine 83 (arrow ε).

  The combustion gas flowing into the turbine 83 collides with the turbine blade 87 connected to the high-pressure main shaft 77 in the high-pressure turbine 83B, thereby rotating the high-pressure main shaft 77 around the axis. As a result, the high-pressure compressor 81B having the compressor blade 88 connected to the high-pressure main shaft 77 is driven. Further, the combustion gas that has passed through the high-pressure turbine 83B collides with the turbine blade 87 connected to the low-pressure main shaft 74 in the low-pressure turbine 83A, thereby rotating the low-pressure main shaft 74 around the axis. As a result, the low pressure compressor 81A having the compressor blade 88 connected to the low pressure main shaft 74 and the fan 75 having the fan blade 75A connected to the low pressure main shaft 74 are driven.

  The combustion gas that has passed through the low-pressure turbine 83A is discharged from the turbine nozzle 84 to the outside. This jet of exhausted combustion gas becomes part of the thrust generated by the turbofan engine 70.

  Here, in the turbofan engine 70, a rolling bearing 89 that rotatably supports the low-pressure main shaft 74 or the high-pressure main shaft 77 with respect to a member disposed opposite to the low-pressure main shaft 74 or the high-pressure main shaft 77 is a turbofan. Under the influence of heat generated in the engine 70, it is used in a high temperature environment. Further, in order to support the high-speed rotation of the low-pressure main shaft 74 or the high-pressure main shaft 77, it is required to reduce the weight of the rolling elements. Furthermore, vibrations and impacts act on the rolling bearing 89 due to fuel combustion and turbine rotation. Therefore, in the rolling bearing 89 that is a rolling bearing for a gas turbine (main shaft bearing), it is possible to reduce the weight of the rolling element and improve the heat resistance while suppressing damage to the raceway member due to vibration or impact. Desired.

  On the other hand, when the rolling bearing 89 is a rolling bearing for a gas turbine in the first embodiment described below, the above requirement can be satisfied.

  FIG. 2 is a schematic cross-sectional view showing a configuration of a three-point contact ball bearing as a gas turbine rolling bearing in the first embodiment. FIG. 3 is a schematic partial cross-sectional view showing an enlarged main part of FIG. With reference to FIG. 2 and FIG. 3, the three-point contact ball bearing as a rolling bearing for gas turbines in Embodiment 1 is demonstrated.

  Referring to FIG. 2, a three-point contact ball bearing 1 includes an annular outer ring 11 that is a race member, an annular inner ring 12 that is a race member disposed inside the outer ring 11, and an outer ring 11 and an inner ring 12. And a plurality of balls 13 as rolling elements that are disposed between and held by an annular retainer 14. An outer ring rolling surface 11 </ b> A is formed on the inner circumferential surface of the outer ring 11, and an inner ring rolling surface 12 </ b> A is formed on the outer circumferential surface of the inner ring 12. And the outer ring | wheel 11 and the inner ring | wheel 12 are arrange | positioned so that 12A of inner ring | wheel rolling surfaces and 11A of outer ring | wheels may mutually oppose.

  The inner ring 12 includes a first inner ring 121 and a second inner ring 122, and has a structure divided at the axially central portion. A first inner ring rolling surface 121A and a second inner ring rolling surface 122A are formed on the outer peripheral surfaces of the first inner ring 121 and the second inner ring 122, respectively. The first inner ring rolling surface 121A and the second inner ring rolling surface 122A constitute an inner ring rolling surface 12A. Further, the plurality of balls 13 can contact and hold the first inner ring rolling surface 121A, the second inner ring rolling surface 122A, and the outer ring rolling surface 11A on the ball rolling surface 13A that is the outer peripheral surface. By being arranged at a predetermined pitch in the circumferential direction by the vessel 14, it is held so as to roll on an annular track. With the above configuration, the outer ring 11 and the inner ring 12 of the three-point contact ball bearing 1 can rotate relative to each other.

Then, balls 13 serving as rolling elements in this embodiment _is represented by a composition formula of _{Si 6-Z Al Z O Z} N 8-Z, composed mainly of β-sialon satisfying 0.1 ≦ z ≦ 3.5 And the Young's modulus is 180 GPa or more and 270 GPa or less.

  Furthermore, with reference to FIG. 3, a ball dense layer 13 </ b> B that is a layer having a higher density than the inside 13 </ b> C is formed in a region including the ball rolling surface 13 </ b> A that is a rolling surface of the ball 13. When the cross section of the dense ball layer 13B is observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 7% or less. With the above configuration, the three-point contact ball bearing 1 in the present embodiment can achieve reduction in the weight of the rolling element and improvement in heat resistance while suppressing damage to the raceway member due to vibration or impact. It is a rolling bearing for gas turbines. The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  Further, referring to FIG. 3, the region including the ball rolling surface 13 </ b> A that is the surface of the ball dense layer 13 </ b> B has a high ball density that is a layer having a higher density than the other regions in the ball dense layer 13 </ b> B. Layer 13D is formed. When the cross section of the ball height dense layer 13D is observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 3.5% or less. Thereby, the durability with respect to rolling fatigue of the ball 13 is further improved, and the durability of the three-point contact ball bearing 1 is further improved.

  In the present embodiment, the balls 13 constituting the three-point contact ball bearing 1 may be composed of a sintered body mainly composed of β sialon and composed of the remaining sintering aid and impurities. By including a sintering aid, the porosity of the sintered body can be easily lowered, and the three-point contact ball bearing 1 that can stably ensure sufficient durability can be easily provided. . The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  FIG. 4 is a schematic cross-sectional view showing a configuration of a cylindrical roller bearing as a rolling bearing for a gas turbine which is a modification of the present embodiment. FIG. 5 is a schematic partial cross-sectional view showing an enlarged main part of FIG. With reference to FIG. 4 and FIG. 5, the cylindrical roller bearing which is a modification of this Embodiment is demonstrated.

  Referring to FIG. 4, the cylindrical roller bearing 2 is disposed between an annular outer ring 21, an annular inner ring 22 disposed inside the outer ring 21, and the outer ring 21 and the inner ring 22. And a plurality of rollers 23 as rolling elements held by 24. The roller 23 has a cylindrical shape. An outer ring rolling surface 21 </ b> A is formed on the inner circumferential surface of the outer ring 21, and an inner ring rolling surface 22 </ b> A is formed on the outer circumferential surface of the inner ring 22. The outer ring 21 and the inner ring 22 are arranged so that the inner ring rolling surface 22A and the outer ring rolling surface 21A face each other. Further, the plurality of rollers 23 come into contact with the inner ring rolling surface 22A and the outer ring rolling surface 21A on the roller rolling surface 23A, which is the outer circumferential surface, and are arranged at a predetermined pitch in the circumferential direction by the cage 24. It is held on an annular track so as to be freely rollable. With the above configuration, the outer ring 21 and the inner ring 22 of the cylindrical roller bearing 2 can rotate relative to each other.

Here, with reference to FIG. 5, the roller 23 of the cylindrical roller bearing 2 in this modification corresponds to the ball 13 and has the same configuration. In other words, the roller 23 is a sintered body that is mainly composed of β sialon that is expressed by a composition formula of Si _6-Z Al _Z O _Z N _8-Z and satisfies 0.1 ≦ z ≦ 3.5, and is composed of the remaining impurities. The Young's modulus is 180 GPa or more and 270 GPa or less. The roller 23 has an inner portion 23C similar to the inner portion 13C of the ball 13, and also includes a roller dense layer 23B and a roller high dense layer 23D similar to the ball dense layer 13B and the ball high dense layer 13D.

  Therefore, the cylindrical roller bearing 2 in the present modification is a rolling bearing for a gas turbine that can achieve reduction in the weight of the rolling element and improvement in heat resistance while suppressing damage to the raceway member due to vibration or impact. It has become.

  Next, the manufacturing method of the rolling bearing for gas turbines in this Embodiment is demonstrated. FIG. 6 is a diagram showing an outline of a method for manufacturing a rolling bearing for a gas turbine in one embodiment of the present invention. Moreover, FIG. 7 is a figure which shows the outline of the manufacturing method of the rolling element which consists of (beta) sialon sintered compact in one embodiment of this invention.

  Referring to FIG. 6, in the method for manufacturing a rolling bearing for a gas turbine in the present embodiment, first, a race member manufacturing process for manufacturing a race member and a rolling element manufacturing process for manufacturing a rolling element are performed. . Specifically, in the race member manufacturing process, the outer rings 11, 21 and the inner rings 12, 22 are manufactured. On the other hand, in the rolling element manufacturing process, balls 13, rollers 23, and the like are manufactured.

  And the assembly process which assembles the rolling bearing for gas turbines is implemented by combining the track member manufactured in the track member manufacturing process, and the rolling element manufactured in the rolling element manufacturing process. Specifically, the three-point contact ball bearing 1 is assembled by combining the outer ring 11 and the inner ring 12 and the ball 13, for example. And a rolling element manufacturing process is implemented using the manufacturing method of the rolling element which consists of the following (beta) sialon sintered compact, for example.

  Referring to FIG. 7, in the method for manufacturing a rolling element made of a β sialon sintered body in the present embodiment, first, a β sialon powder preparation step of preparing β sialon powder is performed. In the β sialon powder preparation step, β sialon powder can be produced at low cost by, for example, a production step employing a combustion synthesis method.

  Next, a mixing step is performed in which a sintering aid is added to and mixed with the β sialon powder prepared in the β sialon powder preparation step. This mixing step can be omitted if no sintering aid is added.

  Next, referring to FIG. 7, a forming step of forming the β sialon powder or a mixture of β sialon powder and a sintering aid into a schematic shape of a rolling element is performed. Specifically, by applying a molding technique such as press molding, cast molding, extrusion molding, rolling granulation, or the like to the above β sialon powder or a mixture of β sialon powder and a sintering aid, the ball 13 A molded body formed into a schematic shape such as the roller 23 is produced.

  Next, a pre-sintering processing step is performed in which the surface of the molded body is processed so that the molded body is shaped to be closer to the shape of the desired rolling element after sintering. Specifically, by applying a processing method such as green body processing, the molded body is processed so as to have a shape closer to the shape of the balls 13 and rollers 23 after sintering. This pre-sintering processing step can be omitted if the shape is sufficiently close to the shape of the desired rolling element after sintering at the stage where the molded body is formed in the forming step.

  Next, referring to FIG. 7, a sintering step is performed in which the molded body is sintered. Specifically, the molded body is heated and sintered under a pressure of 1 MPa or less, for example, heating with a heater, electromagnetic wave heating with microwaves or millimeter waves, and the like, such as balls 13 and rollers 23. A sintered body having a schematic shape is produced. Sintering is performed by heating the molded body to a temperature range of 1550 ° C. or higher and 1800 ° C. or lower in an inert gas atmosphere or a mixed gas atmosphere of nitrogen and oxygen. As the inert gas, helium, neon, argon, nitrogen, or the like can be employed, but nitrogen is preferably employed from the viewpoint of reducing manufacturing costs.

  Next, a finishing process for completing the rolling elements is performed by performing a finishing process in which the surface of the sintered body produced in the sintering process is processed and a region including the surface is removed. Specifically, by polishing the surface of the sintered body produced in the sintering step, the balls 13, rollers 23, etc. as rolling elements are completed. Through the above steps, the rolling element made of the β sialon sintered body in the present embodiment is completed.

  Here, as a result of sintering in the above-described sintering step, a region having a thickness of about 500 μm from the surface of the sintered body is denser than the inside, and when the cross section is observed with oblique light of an optical microscope, a white region is obtained. A dense layer in which the area ratio of the observed white region is 7% or less is formed. Furthermore, the region having a thickness of about 150 μm from the surface of the sintered body has a higher density than the other regions in the dense layer, and is observed as a white region when the cross section is observed with an oblique light of an optical microscope. A highly dense layer in which the area ratio of the white region is 3.5% or less is formed. Therefore, in the finishing step, it is preferable that the thickness of the sintered body to be removed is 150 μm or less particularly in a region to be a rolling surface. Thereby, a highly dense layer can remain in the region including the ball rolling surface 13A and the roller rolling surface 23A, and the rolling fatigue life of the ball 13 and the roller 23 can be improved.

  The sintering step is preferably performed under a pressure of 0.01 MPa or higher in order to suppress the decomposition of β sialon, and more preferably performed under a pressure of atmospheric pressure or higher in consideration of cost reduction. Moreover, in order to form a dense layer while suppressing manufacturing costs, the sintering process is preferably performed under a pressure of 1 MPa or less. Further, in order to adjust the Young's modulus of the rolling element made of the β sialon sintered body to a desired value of 180 GPa or more and 270 GPa or less, for example, the z value of the β sialon powder prepared in the β sialon powder preparation step is set to 0. What is necessary is just to adjust in the range of 1 <= z <= 3.5. More specifically, the Young's modulus of the β sialon sintered body can be decreased by increasing the z value.

  Further, as materials of the outer rings 11 and 21 and the inner rings 12 and 22 in the above embodiment, for example, heat-resistant bearing steels such as AISI standards M50 and M50NiL, high carbon chromium bearing steels such as JIS standards SUJ2, and mechanical structures such as SCM420 Steel such as alloy steel for use and carbon steel for machine structure such as S53C can be employed.

(Embodiment 2)
Next, Embodiment 2 which is another embodiment of the present invention will be described. FIG. 8 is a schematic diagram illustrating a configuration of an external gear box that is a reduction gear of the gas turbine including the gas turbine rolling bearing according to the second embodiment.

  Referring to FIG. 8, an external gear box 60 is a gear box for taking out the rotation of a low-pressure main shaft 74 (see FIG. 1) of a turbofan engine that is an aircraft gas turbine engine. The external gear box 60 has a plurality of gears 61A meshing with a gear 74A disposed on the outer peripheral surface of the low-pressure main shaft 74, a gear shaft 61 connected to the gear 61A, and the gear shaft 61 so as to face the gear shaft 61. Are provided with a ball bearing 68 and a roller bearing 69 which are rotatably supported with respect to a member (housing) disposed in the housing. The external gear box 60 also includes a gear shaft 61 that rotates in response to the rotation of the gear shaft 61 connected to the gear 61A that meshes with the gear 74A. The gear shaft 61 also includes a ball bearing 68 and / or a roller bearing. By 69, it is rotatably supported with respect to the member facing this. Thereby, it can take out as rotation of the gear shaft 61, decelerating rotation of the low-pressure main axis | shaft 74 of a gas turbine. The gear shaft 61 is connected to an accessory gear box (not shown). In this accessory gear box, the rotation of the gear shaft 61 is further decelerated, and drives auxiliary equipment such as a hydraulic pump, a water pump, a generator, and an air compressor.

  Here, the rolling for a gas turbine that rotatably supports a gear shaft 61 that is a rotating member that rotates in response to the rotation of the main shaft of the gas turbine with respect to a member (housing) disposed so as to face the gear shaft 61. A ball bearing 68 and a roller bearing 69 that are bearings (reduction gear bearings) are a gear shaft 61 that rotates in response to the rotation of the low-pressure main shaft 74 that rotates at high speed, or a gear shaft 61 that rotates in response to the rotation of the gear shaft 61. Therefore, it is required to reduce the weight of the rolling element. Further, vibration and impact are applied to the ball bearing 68 and the roller bearing 69 due to fuel combustion and turbine rotation. Therefore, in the ball bearing 68 and the roller bearing 69 which are gas turbine rolling bearings (reduction gear bearings), it is possible to reduce the weight of the rolling element while suppressing damage to the raceway member due to vibration or impact. Desired.

  On the other hand, the ball bearing 68 and the roller bearing 69 in the present embodiment have the same configurations as the three-point contact ball bearing 1 and the cylindrical roller bearing 2 in the first embodiment, respectively. Therefore, the ball bearing 68 and the roller bearing 69 are rolling bearings for a gas turbine that can achieve a reduction in the weight of the rolling element while suppressing damage to the raceway member due to vibration or impact. In addition, the ball bearing 68 and the roller bearing 69 in the present embodiment can be manufactured in the same manner as the three-point contact ball bearing 1 in the first embodiment.

  In the above embodiment, the three-point contact ball bearing and the cylindrical roller bearing have been described as examples of the gas turbine rolling bearing of the present invention. However, the rolling bearing of the present invention is not limited to this, and a deep groove ball bearing or an angular ball bearing. It can be employed for various types of rolling bearings. In the above embodiment, the case where the outer ring and the inner ring are employed as the race members of the rolling bearing of the present invention has been described. However, the race member is a shaft used so that the rolling elements roll on the surface. Or a member such as a housing. That is, the raceway member should just be a member in which the rolling surface for a rolling element to roll was formed.

  Embodiment 1 of the present invention will be described below. Rolling bearings having rolling elements made of β sialon sintered bodies having various z values were produced, and tests for investigating the relationship between the z value and the rolling fatigue life (durability) were conducted. The test procedure is as follows.

  First, a method for producing a test bearing to be tested will be described. First, β sialon powder prepared by a combustion synthesis method with a z value in the range of 0.1 to 4 is prepared, and is basically the same as the rolling element manufacturing method described in the above embodiment based on FIG. The rolling element whose z value is 0.1-4 by the method was produced. A specific manufacturing method is as follows. First, β sialon powder refined to submicron, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., AKP30) and yttrium oxide (manufactured by HC Starck Co., Ltd., Yttrium oxide grade C) as a ball mill Were mixed by wet mixing. Then, granulation was performed with a spray dryer to produce granulated powder. The granulated powder was molded into a sphere with a mold and further pressurized by cold isostatic pressing (CIP) to obtain a spherical molded body.

  Subsequently, after performing atmospheric pressure sintering as primary sintering for the molded body, the sintered spheres are obtained by performing HIP (Hot Isostatic Press) in a nitrogen atmosphere at a pressure of 200 MPa. Manufactured. Next, lapping was performed on the sintered spheres to obtain 3/8 inch ceramic spheres (JIS grade G5). And the bearing of the JIS standard 6206 model number was produced in combination with the bearing ring made from bearing steel (JIS standard SUJ2) prepared separately (Example AJ). For comparison, a rolling element made of silicon nitride, that is, a rolling element having a z value of 0 was also produced in the same manner as the rolling element made of β sialon, and similarly assembled to a bearing (Comparative Example A).

Next, test conditions will be described. Maximum contact surface pressure P _max : 3.2 GPa, bearing rotational speed: 2000 rpm, lubrication: circulating oil supply of turbine oil VG68 (clean oil), test temperature: room temperature for the JIS standard 6206 model bearing manufactured as described above A fatigue test was performed under the conditions of The vibration of the bearing during operation is monitored by the vibration detection device, and the test is stopped when the rolling element is damaged and the vibration of the bearing exceeds a predetermined value. Recorded as bearing life. In addition, after the test was stopped, the bearing was disassembled to confirm the damaged state of the rolling elements.

  Table 1 shows the test results of this example. In Table 1, the life in each Example and Comparative Example is expressed as a life ratio with the life in Comparative Example A (silicon nitride) as 1. The damage form is described as “peeling” when peeling occurs on the surface of the rolling element, and “wearing” when the surface is worn without peeling and the test is stopped.

  Referring to Table 1, Examples A to H of the present invention in which the z value is 0.1 or more and 3.5 or less have a life comparable to that of silicon nitride (Comparative Example A). Yes. Further, the form of breakage is “peeling” as in the case of silicon nitride. On the other hand, in Example I in which the z value exceeds 3.5, the life is shortened and wear is observed on the rolling elements. That is, in Example I in which the z value is 3.8, it is considered that although the rolling element finally peeled off, the life of the rolling element was affected by the wear of the rolling element. Furthermore, in Example J in which the z value is 4, the wear of the rolling elements proceeds in a short time, and the durability of the rolling bearing is further reduced.

  As described above, when the z value is in the range of 0.1 to 3.5, the rolling bearing provided with the rolling element made of β sialon sintered body has the durability of the rolling element made of the silicon nitride sintered body. It is almost equivalent to a rolling bearing with On the other hand, if the z value exceeds 3.5, the rolling elements are likely to be worn, resulting in a decrease in the rolling fatigue life. Furthermore, it has been clarified that when the z value increases, the cause of breakage of the rolling element made of β sialon changes from “peeling” to “wear”, and the rolling fatigue life is further reduced. Thus, it was confirmed that a rolling element made of a β sialon sintered body that is inexpensive and excellent in durability can be obtained by setting the z value to 0.1 or more and 3.5 or less.

  In addition, with reference to Table 1, in Example H in which the z value exceeds 3.5, a slight amount of wear has occurred in the rolling elements, and the service life has also decreased compared to Examples A to G. ing. From this, it can be said that the z value is desirably 3 or less in order to ensure sufficient durability more stably.

  From the above experimental results, the z value is preferably 2 or less, and more preferably 1.5 or less, in order to obtain durability (life) equal to or greater than that of a rolling element made of silicon nitride. On the other hand, in view of the ease of production of β sialon powder by a production process employing combustion synthesis, it is preferable to employ a z value of 0.5 or more at which a reaction due to self-heating can be sufficiently expected.

  Embodiment 2 of the present invention will be described below. A test for producing a rolling bearing having rolling elements made of β-sialon sintered bodies having various z values and investigating the relationship between the z value and the rolling fatigue life in an environment in which an impact is applied to the rolling bearing. Was done. The test procedure is as follows.

  First, a method for producing a test bearing to be tested will be described. First, β sialon powder prepared by a combustion synthesis method with a z value in the range of 0.1 to 3.5 is prepared, and the z value is 0.1 to 3.5 by the same method as in Example 1 above. A rolling element was produced. And the bearing of the JIS standard 6206 model number was produced in combination with the bearing ring produced using the various steel materials prepared separately as a raw material (Examples AJ). As steel constituting the race, JIS standards SUJ2, SCM420, SCr420, S53C, S45C, S40C and AISI standard M50 were adopted. For comparison, a rolling element made of silicon nitride, that is, a rolling element having a z value of 0 was also produced in the same manner as the rolling element made of β sialon, and similarly assembled to a bearing (Comparative Example A).

Next, test conditions will be described. For the bearing of the JIS standard 6206 model number manufactured as described above, the maximum contact surface pressure P _max : 2.5 GPa, the bearing rotation speed: 500 rpm, lubrication: turbine oil VG68 circulating oil supply, vibration conditions: 2500 N (50 Hz), Test temperature: An excitation shock fatigue test was performed under the condition of room temperature. The vibration of the bearing during operation is monitored by the vibration detection device, and the test is stopped when the bearing is damaged and the vibration of the bearing exceeds a predetermined value. Recorded as the lifetime of. In addition, after the test was stopped, the bearing was disassembled to confirm the damaged state of the bearing.

  Table 2 shows the test results of this example. In Table 2, the life in each example and comparative example is shown in the upper part of each column as a life ratio with the life of Comparative Example A (silicon nitride) as 1 when the material of the bearing ring is SUJ2. Yes. Moreover, the damaged part (bearing ring or ball) of the bearing is described in the lower part of each column.

  Referring to Table 2, Examples C to H of the present invention having a z value of 0.5 or more and 3.0 or less clearly have a longer life than silicon nitride (Comparative Example A). Yes. Here, as shown in Table 2, the damaged part was a track member (track ring) as in the case of silicon nitride, and the damaged form was delamination. On the other hand, in Examples I and J in which the z value exceeds 3.0, the life is shortened and the rolling element (ball) is damaged (peeled) first. That is, in Example I in which the z value is 3.25, it is considered that the bearing part (ball) made of the β sialon sintered body is damaged due to the impact and the life is shortened. Furthermore, in Example J in which the z value is 3.5, the rolling elements are peeled off in a shorter time, and the durability of the rolling bearing is further reduced.

  On the other hand, in Examples A and B in which the z value is smaller than 0.5, the lifetime is reduced to substantially the same level as in Comparative Example A, and the raceway member is preceded by breakage (peeling). That is, in Example B in which the z value is 0.25, the difference in physical properties from Comparative Example A in which the z value is 0 (silicon nitride) is reduced. Therefore, the collision between the ball made of the β sialon sintered body and the race member facing the ball unilaterally causes damage on the race member side, and the same as Comparative Example A employing the ball made of the silicon nitride sintered body. It is thought that the lifetime was reduced to

  Furthermore, referring to Table 2, even when the z value is 0.5 or more and 3.0 or less, when the hardness (surface hardness) of the opposite bearing ring is less than HV680, The life tends to be shorter than when the hardness is HV680 or higher. This is thought to be because when the hardness of the raceway is low, damage to the raceway member is likely to occur due to the collision between the ball made of β sialon sintered body and the raceway member facing the ball.

  As described above, when the z value exceeds 3.0, the bearing part itself made of the β sialon sintered body is easily damaged, whereas when the z value is less than 0.5, the contact surface pressure between the mating member is low. It increases, and damage to the mating member is likely to occur. And by making z value 0.5 or more and 3.0 or less, the balance of the intensity | strength of the raw material which comprises a rolling element and the reduction of the contact surface pressure between track members is ensured. As a result, it was confirmed that the life of a rolling bearing including a rolling element made of a β sialon sintered body is improved in an environment in which an impact is applied to the bearing. In particular, when the race member is made of steel, the physical properties of the race member and the physical properties of the rolling elements are well matched, and the occurrence of damage due to impact, vibration, or the like can be suppressed. Thus, it was confirmed that the durability of the rolling bearing when vibration or impact is applied can be improved by setting the z value of β sialon constituting the rolling element to 0.5 or more and 3.0 or less. It was.

  In addition, when the race member is made of steel, it was confirmed that the surface hardness of the race member is preferably HV680 or more in order to suppress damage to the race member.

  Embodiment 3 of the present invention will be described below. A test was conducted to investigate the formation state of the dense layer and the highly dense layer of the rolling elements made of β sialon constituting the rolling bearing for gas turbine of the present invention. The test procedure is as follows.

First, a β sialon powder (product name: Melamix, manufactured by Isman Jay Co., Ltd.) having a composition of Si ₅ AlON ₇ prepared by a combustion synthesis method is prepared, and the rolling element described in the above embodiment based on FIG. A cubic test piece having a side of about 10 mm was produced in the same manner as in the manufacturing method. A specific manufacturing method is as follows. First, a β sialon powder refined to submicron, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., AKP30) and yttrium oxide (manufactured by HC Starck Co., Ltd., Yttrium oxide grade C) as a ball mill Were mixed by wet mixing. Then, granulation was performed with a spray dryer to produce granulated powder. The granulated powder was molded into a predetermined shape with a mold and further pressed by cold isostatic pressing (CIP) to obtain a molded body. Subsequently, the cube test piece was manufactured by heating and sintering the molded body at 1650 ° C. in a nitrogen atmosphere having a pressure of 0.4 MPa (atmospheric pressure sintering).

  Thereafter, the test piece was cut, and the cut surface was lapped with a diamond lapping machine, and then mirror lapping with a chromium oxide lapping machine was performed to form a cross section for observation including the center of the cube. And the said cross section was observed with the oblique light of the optical microscope (the Nikon Corporation make, Microphoto-FXA), and the 50-times-magnification instant photograph (Fujifilm Corporation FP-100B) was image | photographed. Thereafter, the obtained photographic image was taken into a personal computer using a scanner (resolution: 300 DPI). And the binarization process by a brightness | luminance threshold value was performed using the image processing software (Mitani Corporation WinROOF) (binarization separation threshold value in a present Example: 140), and the area ratio of the white area | region was measured.

  Next, test results will be described. FIG. 9 is a photograph of the observation cross section of the test piece taken with an oblique light of an optical microscope. FIG. 10 is an example showing a state in which the image of the photograph in FIG. 9 is binarized by a luminance threshold using image processing software. Further, FIG. 11 shows a region (evaluation region) where image processing is performed when the image of the photograph of FIG. 9 is binarized by the luminance threshold using image processing software and the area ratio of the white region is measured. FIG. In FIG. 9, the upper side of the photograph is the surface side of the test piece, and the upper end is the surface.

  Referring to FIGS. 9 and 10, the test piece in this example manufactured by the same manufacturing method as that of the above embodiment has a layer with less white area than the inside in the area including the surface. I understand. And, as shown in FIG. 11, the photographed photograph image is divided into three regions according to the distance from the outermost surface of the test piece (region within 150 μm distance from the outermost surface, region within 150 μm and within 500 μm, When the area ratio of the white area was calculated by performing image analysis for each area and obtaining the area ratio of the white area, the results shown in Table 3 were obtained. In Table 3, the average value and the maximum value of the area ratio of the white area in five fields obtained from five photographs taken at random are shown with each field shown in FIG. 11 as one field of view. Yes.

  Referring to Table 3, the area ratio of the white region in the present example was 18.5% inside, whereas it was 3.7% in the region having a depth of 500 μm or less from the surface. It was 1.2% in the region where the depth from the region was 150 μm or less. From this, in the test piece in the present example produced by the above manufacturing method similar to the above embodiment, a dense layer and a highly dense layer having a white region less than the inside are formed in the region including the surface. It was confirmed.

  Embodiment 4 of the present invention will be described below. A test was conducted to confirm the rolling fatigue life of the rolling element made of the β sialon sintered body constituting the rolling bearing for gas turbine of the present invention. The test procedure is as follows.

First, a method for producing a test bearing to be tested will be described. First, a β sialon powder (product name: Melamix, manufactured by Isman Jay Co., Ltd.) having a composition of Si ₅ AlON ₇ prepared by a combustion synthesis method is prepared, and the rolling element described in the above embodiment based on FIG. A 3/8 inch ceramic sphere having a diameter of 9.525 mm was produced in the same manner as the production method described above. A specific manufacturing method is as follows. First, a β sialon powder refined to submicron, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., AKP30) and yttrium oxide (manufactured by HC Starck Co., Ltd., Yttrium oxide grade C) as a ball mill Were mixed by wet mixing. Then, granulation was performed with a spray dryer to produce granulated powder. The granulated powder was molded into a sphere with a mold, and further pressurized by cold isostatic pressing (CIP) to obtain a spherical molded body.

  Next, the green body is processed so that the processing allowance after sintering becomes a predetermined dimension, and the green body is subsequently heated to 1650 ° C. in a nitrogen atmosphere at a pressure of 0.4 MPa. By sintering, sintered spheres were produced. Next, lapping was performed on the sintered spheres to obtain 3/8 inch ceramic spheres (rolling elements; JIS grade G5). And the bearing of the JIS standard 6206 model number was produced in combination with the bearing ring made from bearing steel (JIS standard SUJ2) prepared separately. Here, the thickness (processing allowance) of the sintered sphere removed by the lapping process on the sintered sphere was changed in eight stages, and eight types of bearings were produced (Examples A to H). On the other hand, for comparison, lapping is performed on sintered spheres (EC 141 manufactured by Nippon Special Ceramics Co., Ltd.) sintered by pressure sintering using raw material powders composed of silicon nitride and a sintering aid in the same manner as described above. Processing was performed, and a bearing of JIS standard 6206 model number was manufactured in combination with a bearing ring (JIS standard SUJ2) prepared separately (Comparative Example A). The machining allowance for lapping was 0.25 mm.

Next, test conditions will be described. Maximum contact surface pressure P _max : 3.2 GPa, bearing rotational speed: 2000 rpm, lubrication: circulating oil supply of turbine oil VG68 (clean oil), test temperature: room temperature for the JIS standard 6206 model bearing manufactured as described above A fatigue test was performed under the conditions of The vibration of the bearing during operation is monitored by the vibration detection device, and the test is stopped when the rolling element is damaged and the vibration of the bearing exceeds a predetermined value. Recorded as bearing life. The number of tests was 15 in each of the examples and the comparative examples, and after calculating the L ₁₀ life, the durability was evaluated by the life ratio with respect to Comparative Example A.

  Table 4 shows the test results of this example. Referring to Table 4, it can be said that the life of the bearings of the examples is all good considering the manufacturing cost and the like. The life of the bearings of Examples D to G in which the dense layer remains on the surface of the rolling element by setting the machining allowance to 0.5 mm or less is about 1.5 to 2 times the life of Comparative Example A. It was. Furthermore, the life of the bearings of Examples A to C in which the high-density layer remained on the surface of the rolling element by setting the machining allowance to 0.15 mm or less was about three times the life of Comparative Example A. From this, it was confirmed that the rolling bearing for gas turbine of the present invention is excellent in durability. In the rolling bearing for a gas turbine of the present invention, the machining cost of the rolling element made of β sialon sintered body is set to 0.5 mm or less, and the life is improved by leaving the dense layer on the surface. It was found that the lifetime was further improved by leaving the highly dense layer on the surface at 15 mm or less.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rolling bearing for a gas turbine of the present invention can be applied particularly advantageously to a rolling bearing for a gas turbine that is required to suppress damage to the raceway member due to vibration or impact.

1 is a schematic cross-sectional view illustrating a configuration of a turbofan engine including a gas turbine rolling bearing according to Embodiment 1. FIG. 3 is a schematic cross-sectional view showing a configuration of a three-point contact ball bearing in the first embodiment. FIG. FIG. 3 is a schematic partial cross-sectional view showing an enlarged main part of FIG. 2. FIG. 6 is a schematic cross-sectional view showing the configuration of a cylindrical roller bearing that is a modification of the first embodiment. FIG. 5 is a schematic partial cross-sectional view showing an enlarged main part of FIG. 4. It is a figure which shows the outline of the manufacturing method of the rolling bearing for gas turbines in one embodiment of this invention. It is a figure which shows the outline of the manufacturing method of the rolling element which consists of (beta) sialon sintered compact in one embodiment of this invention. FIG. 6 is a schematic diagram showing a configuration of an external gear box in a second embodiment. It is the photograph which image | photographed the cross section for observation of a test piece with the oblique light of the optical microscope. It is an example which shows the state which carried out the binarization process with the brightness | luminance threshold value using the image processing software for the photograph image of FIG. It is a figure which shows the area | region (evaluation area | region) which performs image processing.

Explanation of symbols

  1 3-point contact ball bearing, 2 cylindrical roller bearing, 11, 21 outer ring, 11A, 21A outer ring rolling surface, 12, 22 inner ring, 12A, 22A, inner ring rolling surface, 13 balls, 13A ball rolling surface, 13B ball Dense layer, 13C, 23C inside, 13D ball high density layer, 14, 24 cage, 23A roller rolling surface, 23B roller dense layer, 23D roller high density layer, 60 external gearbox, 61 gear shaft, 61A gear, 68 Ball bearing, 69 Roller bearing, 70 Turbo fan engine, 71 Compression section, 72 Combustion section, 73 Turbine section, 74 Low pressure main shaft, 74A gear, 75 fan, 75A fan blade, 76 fan nacelle, 77 High pressure main shaft, 78 Core cowl, 79 Bypass channel, 81 compressor, 81A low pressure compressor, 81B high pressure compressor, 8 2 Combustion chamber, 83 turbine, 83A low pressure turbine, 83B high pressure turbine, 84 turbine nozzle, 87 turbine blade, 88 compressor blade, 89 rolling bearing, 121 first inner ring, 122 second inner ring, 121A first inner ring rolling surface, 122A Second inner ring rolling surface.

Claims (12)

A rolling bearing for a gas turbine that rotatably supports a main shaft of a gas turbine or a rotating member that is a member that rotates in response to the rotation of the main shaft with respect to a member that is disposed so as to face the main shaft or the rotating member. Because
A track member;
A rolling element that contacts the raceway member and is disposed on an annular raceway,
The rolling element for a gas turbine, wherein the rolling element is made of ceramics capable of suppressing an impact on the race member as compared with a case of silicon nitride.   2. The rolling bearing for a gas turbine according to claim 1, wherein the rolling element is composed of a sintered body mainly composed of β sialon and made of remaining impurities.   2. The rolling bearing for a gas turbine according to claim 1, wherein the rolling element is composed of a sintered body containing β sialon as a main component and the remaining sintering aid and impurities. The β-sialon _is represented by the composition formula of _{Si 6-Z Al Z O Z} N 8-Z, satisfy 0.1 ≦ z ≦ 3.5, the rolling bearing for a gas turbine according to claim 2 or 3. The β-sialon _is represented by the composition formula of _{Si 6-Z Al Z O Z} N 8-Z, satisfy 0.5 ≦ z ≦ 3.0, the rolling bearing for a gas turbine according to claim 2 or 3.   The rolling bearing for a gas turbine according to claim 1, wherein a Young's modulus of the rolling element is 180 GPa or more and 270 GPa or less.   The rolling bearing for a gas turbine according to claim 1, wherein a Young's modulus of the rolling element is 220 GPa or more and 260 GPa or less. The track member is made of steel,
The rolling bearing for a gas turbine according to any one of claims 1 to 7, wherein the raceway member has a surface hardness of HV680 or more.   9. The rolling element according to claim 1, wherein the rolling element has a dense layer, which is a dense layer than the inside, in a region including a rolling surface that is a surface in contact with the raceway member. The rolling bearing for gas turbines described in 1.   The rolling bearing for a gas turbine according to claim 9, wherein when the cross section of the dense layer is observed with oblique light of an optical microscope, the area ratio of the white region observed as a white region is 7% or less.   The rolling for a gas turbine according to claim 9 or 10, wherein a high-density layer that is a layer having a higher density than other areas in the dense layer is formed in a region including the surface of the dense layer. bearing.   The rolling bearing for a gas turbine according to claim 11, wherein when the cross section of the highly dense layer is observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 3.5% or less.