Asymmetric gear teeth

Patent metadata

Field	Value
Publication number	US-11156285-B2
Application number	US-201716325371-A
Country	US
Kind code	B2
Filing date	Aug 16, 2017
Priority date	Aug 16, 2016
Publication date	Oct 26, 2021
Grant date	Oct 26, 2021

Abstract

A gear train includes a first gear having teeth meshed with teeth of a second gear. Each tooth of the first gear includes a coast side and a drive side opposed to the coast side. The drive side has a pressure angle that is greater than that of the coast side. The gear train can be part of a powertrain system for a rotorcraft, and can replace a traditional gear train in a retrofit or new build. The first gear is a planet gear and the second gear is a ring gear wherein the planet gear and ring gear are in a planetary gear train configuration.

First claim

What is claimed is:

1. A gear train comprising:
a first gear having teeth meshed with teeth of a second gear, wherein each tooth of the first gear includes a coast side and a drive side opposed to the coast side, wherein the drive side has a pressure angle that is greater than that of the coast side, and
further wherein the first gear is a planet gear and the second gear is a ring gear wherein the planet gear and ring gear are in a planetary gear train configuration such that the first gear is engaged radially inside the second gear and at a location where the teeth mesh is radially between the first and second gears;
wherein the pressure angle is an angle defined by a first line tangent to a pitch circle, and a second line normal to a tooth profile at the pitch circle;
wherein a ratio of the drive side pressure angle to the coast side pressure angle is 1.8.

2. The gear train as recited in claim 1 , wherein the pressure angle of the drive side is 36°.

3. The gear train as recited in claim 1 , wherein the coast side has a pressure angle of 20°.

4. The gear train as recited in claim 1 , wherein each tooth of the second gear includes a coast side and a drive side oppose to the coast side, wherein the drive side has a pressure angle that is greater than that of the coast side.

5. The gear train as recited in claim 1 , a rotation axis of the first gear is parallel to a rotation axis of the second gear.

6. The gear train as recited in claim 1 , wherein the first gear is one of a plurality of similar planet gears engaged radially inside the second gear.

7. The gear train as recited in claim 6 , wherein each of the planet gears is a compound gear with first and second sets of coaxial gear teeth, wherein the first set of coaxial gear teeth is meshed with the ring gear.

8. The gear train as recited in claim 7 , further comprising a sun gear, wherein the second set of coaxial gear teeth of each planet gear is meshed with teeth of the sun gear.

9. The gear train as recited in claim 8 , wherein there are twelve planet gears evenly spaced circumferentially around the ring gear and the sun gear.

10. A powertrain system for a rotorcraft comprising:
an input module for receiving power from a powerplant system, the input module including first stage reduction gearing;
a main transmission assembly including second stage reduction gearing mechanically coupled to the first stage reduction gearing for receiving power therefrom and a drive shaft mechanically coupled to the second stage reduction for providing power therefrom;
a sun gear mechanically coupled to the drive shaft to be driven thereby;
a set of N primary planetary pinions meshed with the sun gear, wherein N/2 of the primary planetary pinions are upper primary planetary pinions and N/2 of the primary planetary pinions are lower primary planetary pinions, wherein the upper and lower primary planetary pinions are disposed in a staggered, biplanar relationship;
a plurality of N secondary planetary pinions;
a compound drive shaft supporting each respective primary planetary pinion and a respective secondary planetary pinion;
a fixed ring gear meshed with the plurality of secondary planetary pinions wherein the secondary planetary pinions are engaged radially inward of the ring gear; and
a planetary carrier assembly disposed in rotatable combination with the compound drive shafts and operative to provide output power to a main rotor shaft of the rotorcraft,
wherein each tooth of each of the secondary pinions includes a coast side and a drive side opposed to the coast side, wherein the drive side has a pressure angle that is greater than that of the coast side;
wherein the pressure angle is an angle defined by a first line tangent to a pitch circle, and a second line normal to a tooth profile at the pitch circle;
wherein a ratio of the drive side pressure angle to the coast side pressure angle is 1.8.

11. The system as recited in claim 10 , wherein the pressure angle of the drive side is 36°.

12. The system as recited in claim 10 , wherein the coast side has a pressure angle of 20°.

13. The system as recited in claim 10 , wherein each tooth of the ring gear includes a coast side and a drive side oppose to the coast side, wherein the drive side has a pressure angle that is greater than that of the coast side.

14. The system as recited in claim 10 , wherein N=12.

15. The system as recited in claim 10 , wherein the main transmission assembly is mounted to an airframe of a helicopter, wherein the transmission is operatively connected to be driven by an engine of the helicopter, wherein a set of main rotor blades are operatively connected to be driven by the main transmission assembly, and further comprising a tail rotor operatively connected to be driven by the engine.

16. A method of retrofitting a rotorcraft powertrain, the powertrain including a first planetary gear engaged radially inside a second internal gear, the method comprising:
removing the first planetary gear from a rotorcraft powertrain, wherein each tooth of the first planetary gear includes a coast side and a drive side opposed to the coast side, wherein the drive side has a pressure angle that is equal to that of the coast side; and
installing a replacement planetary gear into the rotorcraft powertrain, wherein each tooth of the replacement planetary gear includes a coast side and a drive side opposed to the coast side, wherein the drive side has a pressure angle that is greater than that of the coast side;
wherein the pressure angles of the first planetary gear and the replacement planetary gear are defined by a first line tangent to a pitch circle, and a second line normal to a tooth profile at the pitch circle;
wherein a ratio of the drive side pressure angle to the coast side pressure angle of the replacement planetary gear is 1.8.

Assignees

• Sikorsky Aircraft Corp

Inventors

• Binney David A
• Gmirya Yuriy
• Mucci Joseph A
• Frost Jonathan
• Taylor Adam

Classifications

• B64C27/06

  with single rotor · CPC title

• F16H55/08 Primary

  Profiling · CPC title

• B64C27/14

  Direct drive between power plant and rotor hub · CPC title

• F16H57/08

  of gearings with members having orbital motion · CPC title

• F16H1/28

  with gears having orbital motion · CPC title