Planet gearbox with cylindrical roller bearing with high density roller packing

Patent metadata

Field	Value
Publication number	US-10415429-B2
Application number	US-201514865265-A
Country	US
Kind code	B2
Filing date	Sep 25, 2015
Priority date	Sep 25, 2015
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A planet gearbox is provided for connection to a carrier of an epicyclic gearing arrangement with a single input and single output and including a sun gear, a ring gear and at least one double helix planet gear rotatable on a cylindrical roller bearing with a cage having a cross-web thickness of 15% to 25% of the diameter of the cylindrical rollers and an L/D ratio exceeding 1.0. A gas turbine engine includes a fan and LP shaft, which couples a compressor to a turbine. An epicyclic gearing arrangement has a single input from the LP shaft coupled to a sun gear, a single output coupled to the fan's shaft, and a planet bearing cage having a cross-web thickness measuring 15% to 25% of the roller's diameter.

First claim

What is claimed is:

1. A planet gearbox for connection to a carrier of an epicyclic gearing arrangement that has only a single input and a single output and that includes a sun gear and a ring gear surrounding the planet gearbox and the sun gear, the planet gearbox comprising:
a support pin configured to be fixed to the carrier and defining a cylindrical outer surface that is radially equidistant from a central axis that extends in an axial direction;
an inner race defining a cylindrical inner surface that is non-rotatably connected to the cylindrical outer surface of the support pin, the inner race defining an outer surface that defines at least one track, each track defined in the outer surface being configured to receive and rotatably guide therein a respective plurality of cylindrical rollers;
a respective plurality of cylindrical rollers rotatably disposed within each respective track of the inner race;
wherein each roller defines a cylindrical outer surface that is disposed with an axis of rotation that extends in a direction parallel to the axial direction, and the cylindrical outer surface of each roller is defined by a diameter that extends through the axis of rotation along a direction that is normal to the axis of rotation, wherein the outer cylindrical surface of each roller defines a length in the direction parallel to the axis of rotation of the roller, and the ratio of each roller's length to each roller's diameter is within the range from 1.3 to 1.8, inclusive;
an outer race defining an inner cylindrical surface contacting each respective plurality of cylindrical rollers, the outer race defining an outer cylindrical surface that defines a gearing surface that is configured to mesh with both the sun gear and the ring gear; and
for each respective track, a respective roller cage disposed between the inner race and the outer race, wherein there is a small clearance between each roller cage and the inner race, each respective roller cage being configured to maintain in each respective track a respective separation between each respective roller in each pair of adjacent rollers in that respective track, each roller cage defining a first plurality of generally cylindrical openings, each generally cylindrical opening defining a major axis in the axial direction and a minor axis in the circumferential direction, each of the openings being spaced equidistantly apart circumferentially around the respective roller cage by a plurality of equidistantly spaced apart webs, wherein:
each web has a trapezoidal cross-sectional perimeter outline with non-parallel sides,
each web extends in the axial direction,
each web defines a cross-web thickness in the circumferential direction,
each web is bisected radially by a pitch circle of a planet bearing,
the cross-web thickness increases above the pitch circle of the planet bearing, and
wherein the diameter of one of the rollers establishes a cross-web thickness along the pitch circle of the planet bearing for each web of each roller cage so that each cross-web thickness is 15% to 25% of the diameter of one of the rollers.

2. The planet gearbox of claim 1 , wherein each web of each roller cage has a cross-web thickness that measures 15% to 20% of the diameter of one of the rollers.

3. The planet gearbox of claim 1 , wherein the small clearance between the roller cage and each inner race is on the order of 0.005 to 0.050 inches inclusive.

4. The planet gearbox of claim 3 , wherein each track defines a pair of guiderails, which extend continuously in the circumferential direction around the outer surface of the inner race and radially outwardly from an annular raceway defined in the outer surface of the inner race, wherein the small clearance between each roller cage and the inner race is defined between the respective roller cage and the respective guiderails of the respective track of the inner race.

5. The planet gearbox of claim 1 , wherein the generally cylindrical openings in each respective roller cage are aligned in a circumferential row disposed above a respective track of the inner race, each generally cylindrical opening of the respective roller cage is bounded in the circumferential direction by a pair of opposing and spaced apart shoulder elements, wherein each respective roller is disposed with its cylindrical outer surface extending through a respective opening defined by the respective roller cage, wherein the small clearance between each respective roller cage and the respective track of the inner race is defined between the respective shoulder elements of the respective roller cage and the respective guiderails of the respective track of the inner race.

6. The planet gearbox of claim 1 , wherein at least one of the webs of at least one roller cage is a split web.

7. The planet gearbox of claim 1 , wherein the gearing surface of each cylindrical outer race is a double helical gearing surface with the bias of each one of the two double helical gearing surfaces of the outer race being disposed nonparallel with the other one of the two double helical gearing surfaces of the outer race.

8. The planet gearbox of claim 1 , wherein each track extends circumferentially around the outer surface of the inner race, each track defining a raceway surface extending circumferentially and concentrically with respect to the inner cylindrical surface of the inner race and contacting a portion of each of the cylindrical outer surfaces of the rollers disposed in the respective track, each track defining a pair of radially extending sidewalls that are spaced apart in the axial direction from each other.

9. The planet gearbox of claim 1 , wherein the inner cylindrical surface of the inner race is press-fitted to the cylindrical outer surface of the support pin.

10. The planet gearbox of claim 1 , wherein each of the rollers is formed of ceramic material.

11. The planet gearbox of claim 1 , wherein each side of the pair of sides contacts the outer cylindrical surface of an adjacent cylindrical roller at a single roller contact diameter of the web, and the single roller contact diameter is greater than a diameter of the pitch circle of the planet bearing.

12. The planet gearbox of claim 1 , wherein the outer race is engaged with the ring gear.

13. A gas turbine engine comprising:
a fan including a plurality of blades extending radially from a hub and rotatable about a first axis of rotation defined centrally through the hub;
a compressor disposed downstream from the fan;
a turbine disposed downstream of the compressor;
a rotatable input shaft mechanically coupling the compressor to rotate in unison with the turbine;
an epicyclic gearing arrangement that has only a single input and that includes a carrier, a sun gear rotatable about a second axis of rotation that is parallel to the first axis of rotation, a ring gear disposed circumferentially around the sun gear, at least one planet gearbox that is carried by the carrier and houses a planet gear rotatable with respect to the carrier about a third axis of rotation that is parallel to the second axis of rotation, wherein the at least one planet gear meshes with both the sun gear and the ring gear; and
an engine envelope surrounding the fan, the compressor, the turbine and the epicyclic gearing arrangement, wherein one of the ring gear and the carrier is non-rotatably coupled to the engine envelope; and
the planet gearbox further including:
a support pin fixed to the carrier and defining a cylindrical outer surface that is equidistant from a central axis that extends in an axial direction,
an inner race defining an inner cylindrical surface that is non-rotatably conn

Assignees

• Gen Electric

Inventors

• Hasting William Howard
• Bradley Donald Albert
• Dickman Joseph Robert

Classifications

• F16C2361/61

  Toothed gear systems, e.g. support of pinion shafts · CPC title

• F16C2240/60

  Thickness, e.g. thickness of coatings · CPC title

• F16C2240/46

  Gap sizes or clearances · CPC title

• F16C2206/40

  Ceramics, e.g. carbides, nitrides, oxides, borides of a metal · CPC title

• F16C33/485

  with two or more juxtaposed cages joined together or interacting with each other · CPC title