Face Gear Pinion Design for Tail Rotor Power Transfer

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Solution Overview

Problem

In helicopter transmissions using face gears, the shaft setting and ratio of a power take-off pinion required for the tail rotor and accessories often differ from those of the input pinion, leading to increased part count, weight, noise, and costs due to the need for adapter gears.

Innovation Solution

A new pinion is designed to mesh with the face gear at a different shaft angle, offset, and/or rotation ratio than the original pinion, maintaining tangency contact and allowing true conjugate action, which reduces the need for adapter gears by optimizing the design parameters of the new pinion relative to the face gear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If adapter gears are used to match different shaft settings and ratios, then power transfer between pinions with different parameters is enabled, but part count increases

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidpart count

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The face gear is designed with a universal tooth surface geometry that can mesh with multiple pinions having different shaft settings, offsets, and rotation ratios. The new pinion tooth surface is generated to maintain tangency contact with the original pinion's meshing area, allowing the same face gear to work with different pinions directly without adapter gears, thus reducing part count while maintaining adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention changes the design parameters of the pinion (shaft angle, shaft offset, rotation ratio) while regenerating the tooth surface geometry to maintain proper meshing. By altering the pinion parameters and corresponding tooth surface generation, the system achieves different power transfer configurations directly, eliminating the need for adapter gears

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If adapter gears are used to accommodate different shaft settings and ratios, then power transfer is enabled, but weight increases

Engineering Contradiction:

Improveshaft setting flexibilityVSAvoidgear set weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The adapter gears are extracted/removed from the system by directly designing the new pinion to mesh with the face gear. The tooth surface of the new pinion is generated to maintain tangency contact with the original pinion's meshing area, allowing direct power transfer without intermediate adapter components, thus reducing overall weight

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The face gear serves multiple functions by being able to mesh with pinions having different shaft settings and ratios directly. This multi-functionality eliminates the need for separate adapter gear sets for different configurations, reducing the total weight of moving components

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If adapter gears are used to match different pinion parameters, then power transfer is enabled, but noise increases

Engineering Contradiction:

Improvedesign parameter flexibilityVSAvoidnoise

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The new pinion tooth surface is generated to maintain continuous tangency contact with the original pinion's meshing area throughout the meshing process. This continuous contact ensures smooth power transfer and conjugate action, reducing impact and noise compared to adapter gear arrangements which may have discontinuous or less optimal contact

Inventive Principle:

Principle #20Continuity of useful action

4Adaptability or versatility

If adapter gears are used to accommodate different shaft settings and ratios, then power transfer is enabled, but costs increase

Engineering Contradiction:

Improvepower take-off capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The face gear is designed with universal meshing capability that allows it to work with multiple pinions having different shaft settings, offsets, and ratios directly. This eliminates the need for separate adapter gear sets for different power take-off configurations, reducing manufacturing costs through fewer parts and simplified production

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The expensive and complex adapter gear sets are removed from the system. Instead, the face gear and pinion are directly designed with compatible tooth surface geometries that maintain tangency contact, simplifying the manufacturing process and reducing costs

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8205518B2Pinion meshing with a given face gear in accordance with altered design parameters

Publication Date: 2012.06.26 THE BOEING CO

AI summary

A face gear set having a face gear and an original pinion. The original pinion may mesh with the face gear. The face gear set may have a new pinion, different from the original pinion, which meshes with the face gear in accordance with at least one design parameter different from a corresponding design parameter of the original pinion. The new pinion may have a tooth surface defined by a theoretical plane. The tooth surface of the new pinion may maintain tangency contact with the original pinion during rotation and translation of the plane over a meshing area of the original pinion with the face gear, and also during rotation of each of the face gear, the original pinion and the new pinion at constant speed about the new pinion's axis of rotation.