Patent Description:
A gas turbine engine includes a rotating shaft that couples a compressor and a turbine. A bearing (rear bearing) that supports the rotating shaft is attached to a portion of the rotating shaft which portion is close to the turbine (see <CIT>, for example).

<CIT> discloses a bearing assembly of a gas turbine engine with a inner race that rotates with a shaft that is coupled to it, the inner race being disposed inside an outer race to which a bearing support structure is coupled. A housing is disposed around the bearing support structure, such that they form a squeeze-film damper annulus that allows relative movement between the bearing support structure and the housing.

Since a combustion gas flows through the vicinity of the rear bearing, the rear bearing tends to become high in temperature. Especially, seizure of a cage that holds rolling elements, such as balls or rollers, among components of the rear bearing tends to occur. Therefore, a cageless bearing may be adopted as the rear bearing. However, the cage of a roller bearing including the rollers as the rolling elements cannot be omitted in terms of structure, and the cageless bearing is inevitably a ball bearing.

Thermal expansion of a housing to which an outer race of the rear bearing is fixed is larger than thermal expansion of the rotating shaft to which an inner race of the rear bearing is fixed. Therefore, when the gas turbine engine starts operating, a positioning error between the outer race and the inner race in an axial direction occurs. When the ball bearing is adopted as the rear bearing, this positioning error may not be absorbed.

An object of the present invention is to provide a gas turbine engine which can adopt as a rear bearing a cageless ball bearing whose seizure hardly occurs.

The present invention solves this problem with a gas turbine engine having the features of claim <NUM>.

According to this configuration, even if the positioning error between the housing and the rotating shaft in the axial direction occurs by the thermal expansion, a large positioning error between the outer race and the inner race of the rear bearing does not occur. On this account, according to the above configuration, a cageless ball bearing is adopted as the rear bearing.

The present invention provides a gas turbine engine which adopts as a rear bearing a cageless ball bearing whose seizure hardly occurs.

Hereinafter, a gas turbine engine (hereinafter simply referred to as an "engine") <NUM> according to an embodiment will be described. <FIG> is a schematic diagram of the engine <NUM>. Hereinafter, a left side on a paper surface of <FIG> is referred to as a "front side," and a right side on the paper surface of in <FIG> is referred to as a "rear side.

The engine <NUM> of the present embodiment takes in air from the front side and discharges a combustion gas to the rear side. The engine <NUM> may be a single-shaft gas turbine engine or a two-shaft gas turbine engine. As shown in <FIG>, the engine <NUM> includes a compressor <NUM>, a combustor <NUM>, a turbine <NUM>, a rotating shaft <NUM>, a front bearing <NUM>, a rear bearing <NUM>, a housing <NUM>, a lubricator <NUM>, and a rear bearing holding member <NUM>. These components will be described in order.

The compressor <NUM> is a component that compresses air which has been taken in. The compressor <NUM> may be: an axial compressor that compresses air which has been taken in from the front side, and supplies the air to the rear side; a centrifugal compressor that supplies the compressed air outward in a radial direction; or a combination thereof. The air compressed by the compressor <NUM> is supplied to the combustor <NUM> located downstream of the compressor <NUM>.

The combustor <NUM> is a component that sprays a fuel to the air compressed by the compressor <NUM> and combusts the fuel. The fuel used in the engine <NUM> is not especially limited, and the type of the combustor <NUM> is not especially limited. In the combustor <NUM>, a high-temperature and high-pressure combustion gas is generated by combusting the fuel. The combustion gas is supplied to the turbine <NUM> located downstream of the combustor <NUM>.

The turbine <NUM> is rotated by energy of the combustion gas generated by the combustor <NUM>. The turbine <NUM> may be: an axial turbine into which the combustion gas flows from the front side and through which the combustion gas flows to the rear side; a centrifugal turbine through which the combustion gas flows outward in the radial direction; or a combination thereof.

The rotating shaft <NUM> is a member that couples the compressor <NUM> and the turbine <NUM>. The rotating shaft <NUM> extends in an axial direction (front-rear direction) of the engine <NUM>. The rotating shaft <NUM> of the present embodiment is formed integrally but may be formed by coupling shafts to each other.

The front bearing <NUM> is a bearing attached to a portion of the rotating shaft <NUM> which portion is close to the compressor <NUM>. The front bearing <NUM> of the present embodiment is located at the front side of the compressor <NUM>. However, an axial position of the front bearing <NUM> may overlap an axial position of the compressor <NUM>. To be specific, the front bearing <NUM> may be located at a radially inner side of the compressor <NUM>. Based on the flow of the air, the front bearing <NUM> is located at a portion, located upstream of the combustor <NUM>, of the rotating shaft <NUM> or its vicinity, and the air taken in by the compressor <NUM> flows around the front bearing <NUM>. Therefore, the front bearing <NUM> hardly becomes high in temperature as compared to the below-described rear bearing <NUM> around which the combustion gas flows.

<FIG> is a diagram showing the front bearing <NUM> and its vicinity when viewed in the axial direction. As shown in <FIG>, the front bearing <NUM> is a cageless ball bearing that includes an inner race <NUM>, an outer race <NUM>, and balls <NUM> but does not include a cage that holds the balls <NUM> therein. However, the front bearing <NUM> may include a cage and may be a roller bearing. Omitting the cage from the roller bearing is impossible in terms of structure, and the cageless bearing is inevitably a ball bearing.

Moreover, the front bearing <NUM> of the present embodiment is a ceramic bearing in which the inner race <NUM>, the outer race <NUM>, and the balls <NUM> are made of ceramics or a hybrid bearing in which the inner race <NUM> and the outer race <NUM> are made of metal, and the balls <NUM> are made of ceramics. However, all of the inner race <NUM>, the outer race <NUM>, and the balls <NUM> may be made of metal.

The inner race <NUM> of the front bearing <NUM> is fixed to the rotating shaft <NUM>, and the outer race <NUM> of the front bearing <NUM> is fixed to the housing <NUM> (front housing <NUM>). Therefore, the front bearing <NUM> cannot move in the axial direction relative to the rotating shaft <NUM> and the housing <NUM>. To be specific, a portion of the rotating shaft <NUM> and a portion of the housing <NUM> which portions correspond to the front bearing <NUM> serve as a reference point, and a positioning error in the axial direction does not occur at the reference point.

The rear bearing <NUM> is a bearing attached to a portion of the rotating shaft <NUM> which portion is close to the turbine <NUM>. As shown in <FIG>, the rear bearing <NUM> of the present embodiment is located at the rear side of the turbine <NUM>. However, an axial position of the rear bearing <NUM> may overlap an axial position of the turbine <NUM>. To be specific, the rear bearing <NUM> may be located at a radially inner side of the turbine <NUM>. Based on the flow of the combustion gas, the rear bearing <NUM> is located at a portion, located downstream of the combustor <NUM>, of the rotating shaft <NUM> or its vicinity, and the combustion gas flows around the rear bearing <NUM>. Therefore, the rear bearing <NUM> tends to become high in temperature.

<FIG> is a diagram showing the rear bearing <NUM> and its vicinity when viewed in the axial direction. As shown in <FIG>, the rear bearing <NUM> is a cageless ball bearing that includes an inner race <NUM>, an outer race <NUM>, and balls <NUM> but does not include a cage that holds the balls <NUM>. Since the cage is omitted, seizure of the cage does not occur, and seizure of the entire rear bearing <NUM> can be suppressed.

Moreover, the rear bearing <NUM> of the present embodiment is a ceramic bearing in which the inner race <NUM>, the outer race <NUM>, and the balls <NUM> are made of ceramics or a hybrid bearing in which the inner race <NUM> and the outer race <NUM> are made of metal, and the balls <NUM> are made of ceramics. However, all of the inner race <NUM>, the outer race <NUM>, and the balls <NUM> may be made of metal. When the rear bearing <NUM> is the ceramic bearing or the hybrid bearing, the seizure of the rear bearing <NUM> can be further suppressed.

In the engine <NUM> according to the present embodiment, the rotating shaft <NUM> is supported by the front bearing <NUM> and the rear bearing <NUM>. However, in addition to these bearings, the engine <NUM> may include another bearing that supports the rotating shaft <NUM>. To be specific, the engine <NUM> may include three or more bearings.

As shown in <FIG>, the housing <NUM> includes an outer housing <NUM> and an inner housing <NUM>. The outer housing <NUM> forms an outer shell of the engine <NUM>, and the inner housing <NUM> is located inside the outer housing <NUM>. The outer housing <NUM> and the inner housing <NUM> form a passage of the air and the combustion gas. Moreover, the inner housing <NUM> includes a hollow front housing <NUM> and a hollow rear housing <NUM>. The front housing <NUM> is located at the front side of the compressor <NUM>, and the rear housing <NUM> is located at the rear side of the turbine <NUM>. The outer housing <NUM> and the inner housing <NUM> are coupled to each other by a post or a stationary blade extending in a radial direction between the outer housing <NUM> and the inner housing <NUM>.

Moreover, a material of the housing <NUM> and a material of the rotating shaft <NUM> are different from each other. Therefore, the housing <NUM> and the rotating shaft <NUM> are different in the coefficient of thermal expansion from each other, and the housing <NUM> and the rotating shaft <NUM> are different in the amount of change of an axial dimension by the thermal expansion from each other. Therefore, when the engine <NUM> starts, the positioning error in the axial direction is generated between the rotating shaft <NUM> and the housing <NUM>. To be specific, a portion of the rotating shaft <NUM> and a portion of the housing <NUM> which have been located at the same axial position before the operation of the engine <NUM> are located at different axial positions from each other after the operation of the engine <NUM>. The above positioning error increases in a direction away from the portion corresponding to the front bearing <NUM> as the reference point. When the housing <NUM> and the rotating shaft <NUM> are different in temperature from each other although the material of the housing <NUM> and the material of the rotating shaft <NUM> are the same as each other, the positioning error in the axial direction by the thermal expansion occurs.

The lubricator <NUM> is a device that supplies lubricating oil to the front bearing <NUM> and the rear bearing <NUM>. The lubricator <NUM> of the present embodiment is a non-circulation lubricator that injects disposable lubricating oil to the front bearing <NUM> and the rear bearing <NUM>. Specifically, the lubricator <NUM> mixes the lubricating oil with the compressed air extracted from the compressor <NUM>, and injects a mixture of the oil and the air to the front bearing <NUM> and the rear bearing <NUM>. The lubricator <NUM> may inject the lubricating oil without mixing the lubricating oil with the compressed air and may be a circulation lubricator that collects and reuses the used lubricating oil.

The lubricator <NUM> of the present embodiment can be manufactured at low cost since the lubricator <NUM> does not have to include a mechanism that circulates the lubricating oil. On the other hand, the amount of lubricating oil supplied to the bearings <NUM> and <NUM> by the lubricator <NUM> is smaller than that by a circulation lubricator. Therefore, in the present embodiment, coolability of cooling the bearings <NUM> and <NUM> by the lubricating oil is limited. Especially, the seizure of the rear bearing <NUM> that becomes high in temperature tends to occur. However, as described above, since a bearing that is a hybrid bearing and is a cageless ball bearing is adopted as the rear bearing <NUM> of the present embodiment, the seizure of the rear bearing <NUM> is suppressed. However, there is a problem that due to the positioning error between the inner race and the outer race in the axial direction, the ball bearing breaks more easily than the roller bearing.

Moreover, there is another problem that when the amount of lubricating oil supplied to the rear bearing <NUM> is small, a vibration damping effect of the rear bearing <NUM> in the radial direction cannot be obtained. To be specific, when an adequate amount of lubricating oil is supplied to the rear bearing <NUM>, the lubricating oil flows into between the rear bearing <NUM> and the housing <NUM> and serves as a squeeze film damper. However, when the amount of lubricating oil supplied to the rear bearing <NUM> is small, the effect of the squeeze film damper cannot be expected. To solve these problems, the engine <NUM> according to the present embodiment includes the rear bearing holding member <NUM>.

The rear bearing holding member <NUM> is a member that is interposed between the rear bearing <NUM> and the housing <NUM> and holds the rear bearing <NUM>. The rear bearing holding member <NUM> of the present embodiment is formed by a metal plate. As shown in <FIG>, the rear bearing holding member <NUM> has a tubular shape that is polygonal when viewed in the axial direction. The rear bearing holding member <NUM> is inscribed in the housing <NUM> and circumscribed about the rear bearing <NUM>. To be specific, portions of the rear bearing holding member <NUM> which portions correspond to vertexes of the polygon are in contact with the housing <NUM>, and intermediate portions each between the adjacent vertexes are in contact with the outer race <NUM> of the rear bearing <NUM>.

The rear bearing holding member <NUM> is fixed to the housing <NUM>. The rear bearing holding member <NUM> holds the outer race <NUM> of the rear bearing such that the outer race <NUM> is slidable in the axial direction. Therefore, even if the positioning error between the housing <NUM> and the rotating shaft <NUM> in the axial direction occurs by the thermal expansion, the outer race <NUM> of the rear bearing <NUM> moves in the axial direction relative to the housing <NUM>, and therefore, a large positioning error does not occur between the outer race <NUM> and the inner race <NUM> of the rear bearing <NUM>. With this, the breakage of the rear bearing <NUM> can be avoided.

Moreover, the rear bearing holding member <NUM> elastically deforms, and for example, by friction between the rear bearing holding member <NUM> and the housing <NUM>, portions of the rear bearing holding member <NUM> which portions hold the rear bearing <NUM> (i.e., portions of the rear bearing holding member <NUM> which portions are in contact with the rear bearing <NUM>) move in the radial direction relative to the housing <NUM> while attenuating vibration of the rear bearing <NUM>. To be specific, the rear bearing holding member <NUM> holds the rear bearing <NUM> such that the rear bearing <NUM> is movable in the radial direction relative to the housing <NUM> while being attenuated. Therefore, the rear bearing holding member <NUM> serves as a damper that attenuates the vibration of the rear bearing <NUM> in the radial direction.

The rear bearing holding member <NUM> is not limited to the configuration shown in <FIG>. For example, the rear bearing holding member <NUM> may have the configuration shown in <FIG> is a diagram showing the rear bearing holding member <NUM> of a modified example and its vicinity when viewed in the axial direction. The rear bearing holding member <NUM> of the modified example includes elastic members <NUM>. The elastic members <NUM> are so-called coil springs and are arranged at intervals in the circumferential direction of the rear bearing <NUM>. Each elastic member <NUM> is located between the rear bearing <NUM> and the housing <NUM>, and both end portions of the elastic member <NUM> are respectively fixed to the outer race <NUM> of the rear bearing <NUM> and the housing <NUM>. To be specific, each elastic member <NUM> couples the outer race <NUM> of the rear bearing <NUM> and the housing <NUM>.

The elastic member <NUM> is elastically deformable in the axial direction and the radial direction of the rear bearing <NUM>. Therefore, a portion of the elastic member <NUM> which portion is coupled to the rear bearing <NUM> is movable in the axial direction relative to the housing <NUM>. However, since the vibration damping effect of this configuration in the radial direction is smaller than that of the configuration shown in <FIG>, the configuration shown in <FIG> is more desirable from the viewpoint of the vibration damping effect. Moreover, the rear bearing holding member <NUM> may have a configuration other than the configurations shown in <FIG> and <FIG>. For example, the rear bearing holding member <NUM> may be configured by combining a member that elastically deforms in the axial direction of the rear bearing <NUM> and a member that elastically deforms in the radial direction of the rear bearing <NUM>.

As above, a gas turbine engine according to the present embodiment includes: a compressor that compresses air which has been taken in; a combustor that sprays a fuel to the air compressed by the compressor and combusts the fuel; a turbine that is rotated by energy of a combustion gas generated by the combustor; a rotating shaft that couples the compressor and the turbine; a rear bearing that is a cageless ball bearing including an inner race, an outer race, and a ball, the inner race being fixed to a portion of the rotating shaft which portion is close to the turbine; a housing to which the rear bearing is attached; and a rear bearing holding member that is interposed between the rear bearing and the housing and holds the outer race of the rear bearing such that the outer race of the rear bearing is movable in an axial direction relative to the housing.

As above, in the gas turbine engine according to the present embodiment, the outer race of the rear bearing is held so as to be movable in the axial direction relative to the housing. Therefore, even if the positioning error between the housing and the rotating shaft in the axial direction occurs by the thermal expansion, a large positioning error between the outer race and the inner race of the rear bearing does not occur, and therefore, the breakage of the rear bearing can be avoided. On this account, in the gas turbine engine according to the present embodiment, a cageless ball bearing whose seizure hardly occurs can be adopted as the rear bearing.

Moreover, the gas turbine engine according to the present embodiment further includes a front bearing including an inner race, an outer race, and a ball, the inner race being fixed to a portion of the rotating shaft which portion is close to the compressor, the outer race being fixed to the housing so as not to be movable in the axial direction relative to the housing.

As above, in the gas turbine engine according to the present embodiment, the rear bearing is movable in the axial direction relative to the housing, and the front bearing is fixed so as not to be movable in the axial direction relative to the housing. With this, the rotating shaft can be stably held.

Moreover, in the gas turbine engine according to the present embodiment, the rear bearing holding member holds the outer race of the rear bearing such that the rear bearing is movable in a radial direction relative to the housing.

Therefore, even if the rear bearing moves in the radial direction by vibration or the like, the rear bearing holding member can hold the rear bearing.

Moreover, in the gas turbine engine according to the present embodiment, a portion of the rear bearing holding member which portion holds the outer race of the rear bearing is movable in the radial direction relative to the housing while attenuating vibration of the rear bearing.

According to this configuration, the rear bearing holding member can hold the rear bearing such that the rear bearing is movable in both the axial direction and the radial direction relative to the housing. As a result, the breakage of the rear bearing during the operation of the gas turbine engine can be prevented, and the vibration of the rear bearing in the radial direction can be attenuated.

Moreover, in the gas turbine engine according to the modified example of the present embodiment, the rear bearing holding member includes an elastic member that is elastically deformable in the axial direction and the radial direction relative to the housing, and the rear bearing holding member holds the rear bearing through the elastic member.

According to this configuration, the rear bearing holding member can hold the rear bearing such that the rear bearing is movable in both the axial direction and the radial direction relative to the housing. As a result, the breakage of the rear bearing during the operation of the gas turbine engine can be prevented.

Moreover, in the gas turbine engine according to the present embodiment, the rear bearing is a ceramic bearing in which the inner race, the outer race, and the ball are made of ceramics or a hybrid bearing in which the inner race and the outer race are made of metal, and the ball is made of ceramics.

Since the rear bearing is the ceramic bearing or the hybrid bearing, the seizure of the rear bearing can be further suppressed.

Moreover, the gas turbine engine according to the present embodiment further includes a non-circulation lubricator that injects lubricating oil to the rear bearing.

Claim 1:
A gas turbine engine comprising:
a compressor (<NUM>) that compresses air which has been taken in:
a combustor (<NUM>) that sprays a fuel to the air compressed by the compressor and combusts the fuel;
a turbine (<NUM>) that is rotated by energy of a combustion gas generated by the combustor;
a rotating shaft (<NUM>) that couples the compressor and the turbine;
a rear bearing (<NUM>) that is a cageless ball bearing including an inner race (<NUM>), an outer race (<NUM>), and a ball (<NUM>), the inner race being fixed to a portion of the rotating shaft which portion is close to the turbine;
a housing (<NUM>) to which the rear bearing is attached; and
a rear bearing holding member (<NUM>) that is interposed between the rear bearing and the housing, characterised in that the rear bearing holding member is fixed to the housing, holds the outer race of the rear bearing such that the outer race of the rear bearing is movable in an axial direction relative to the rear bearing holding member, and therefore holds the outer race of the rear bearing such that the outer race of the rear bearing is movable in the axial direction relative to the housing.