Planetary Gear Train Pin Retention With Axial Play

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing planetary gear trains face challenges in achieving a robust construction and efficient assembly, particularly in preventing planetary gear pins from falling out and rotating excessively, which can lead to structural distortion due to thermal expansion.

Innovation Solution

A planetary gear train design featuring a planet carrier with radial pin bores, seated planetary gear pins, and an annular disk attached to the radial wall that stands radially above the pin bores, axially fixed to an annular collar, providing secure engagement and preventing pin rotation through a contact geometry that allows for axial play to prevent over-determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If planetary gear pins are tightly fitted in pin bores to prevent falling out, then reliability is improved, but manufacturing precision is worsened due to thermal expansion causing over-determination

Engineering Contradiction:

Improveprevention of pin falling outVSAvoidstructural distortion from thermal expansion

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The pin bore is designed with different local qualities: the upper portion has a tighter fit to prevent pin dropping, while the lower portion has a larger clearance to accommodate thermal expansion. This local differentiation resolves the contradiction between preventing pin falling out and allowing for thermal expansion without structural distortion.

Inventive Principle:

Principle #3Local quality

2Reliability

If locator ring is used to ensure axial and rotational positioning, then reliability is improved, but device complexity is worsened

Engineering Contradiction:

Improveaxial and rotational positioningVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The planet carrier is designed to integrate multiple functions: it provides the pin bores for axial positioning, the radial wall geometry provides rotational positioning, and the overall structure supports the planetary gears. By merging these positioning functions into the planet carrier itself rather than using a separate locator ring, the design achieves reliable positioning while reducing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If annular disk is axially fixed to radial collar to prevent pin rotation, then reliability is improved, but ease of manufacture is worsened

Engineering Contradiction:

Improveprevention of pin rotationVSAvoidassembly complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The annular collar is pre-formed as an integral part of the planet carrier structure, with the annular disk already axially fixed to it during planet carrier manufacturing. This preliminary action ensures that the pin rotation prevention mechanism is already in place before planetary gear pin assembly, simplifying the overall manufacturing process while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11248697B2Planetary gear train

Publication Date: 2022.02.15 SCHAEFFLER TECHNOLOGIES AG & CO KG

AI summary

A planetary gear train which includes a planet carrier having at least one radial wall with pin bores formed therein, planetary gear pins that are seated in said pin bores on at least one end, planetary gears that are arranged on the planetary gear pins, and a ring gear that is attached to the radial wall and dimensioned such as to rise radially above an inner enveloping circle of the pin bores. The radial wall carrying an annular collar and the ring gear is axially secured to the annular collar.