Transfer Case Dual Planetary Gearsets On-the-Fly Low Ratio

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Solution Overview

Problem

Existing transfer cases used in rock crawling vehicles face challenges in quickly engaging and disengaging low gear ratios without gear binding, which limits maneuverability and incurs penalties in competitions due to the limitations of traditional gear-based systems.

Innovation Solution

A transfer case design utilizing dual planetary gear sets with idler gears and holding members, such as brake bands, allows for on-the-fly engagement and disengagement of low gear ratios without binding, enabling independent control of front and rear wheels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If traditional gear-based transfer cases are used to achieve low gear ratios, then gear reduction capability is improved, but gear binding occurs during engagement and disengagement

Engineering Contradiction:

Improvegear reduction capabilityVSAvoidgear engagement smoothness

Core Design Contradiction:

PowerVSEase of operation

Solution Approach 1:

The patent replaces the traditional mechanical gear shifting system with a planetary gear set system that uses friction-based holding members (brake bands) to control gear engagement. This substitution eliminates the binding problem associated with traditional gear slides and forks by using continuous friction contact instead of discrete mechanical gear teeth engagement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces holding members (brake bands) as intermediaries between the planetary gear sets and the output shafts. These holding members act as mediators that smoothly engage and disengage the low gear ratio by applying friction-based holding force to the ring gears, preventing direct mechanical binding between gear components.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If shift fork slides are used for gear engagement, then gear ratio changing is achieved, but vehicle movement must stop or reverse to shift

Engineering Contradiction:

Improvegear ratio variabilityVSAvoidshifting time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent replaces the stop-dependent shift fork slide mechanism with a planetary gear set system using friction-based holding members. This allows gear ratio changes to occur continuously during vehicle motion by applying or releasing friction-based holding force on the ring gears, eliminating the need to stop or reverse the vehicle for shifting.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent makes the gear engagement system dynamic by allowing continuous adjustment of the holding member engagement force during vehicle operation. This dynamic control enables smooth transitions between high and low gear ratios without requiring the vehicle to be stationary, thereby reducing shifting time and maintaining operational continuity.

Inventive Principle:

Principle #15Dynamics

3Reliability

If existing transfer cases are used, then basic functionality is provided, but low gear ratio engagement causes gear binding

Engineering Contradiction:

Improvetransfer case functionalityVSAvoidgear binding

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the traditional mechanical gear engagement system with a planetary gear set system that uses friction-based holding members. This substitution eliminates the harmful binding effect by using continuous friction contact between the holding members and ring gears, preventing the mechanical interference and binding that occurs in traditional gear-based transfer cases.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the potential harm of friction-based holding into a benefit by using controlled friction engagement to prevent gear binding. The friction between the holding members and ring gears, which could be considered a source of energy loss, is instead utilized to smoothly control engagement and disengagement, eliminating the more harmful binding effect in traditional gear systems.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design enhances maneuverability and control during rock crawling by preventing gear binding, allowing for seamless transitions between wheel engagements and reducing the risk of penalties associated with stopping or reversing to shift gears.

Implementation Method 1

a first planetary gearset having a sun gear, a carrier having a plurality of planetary gears, and a ring gear

Methodology Applied

Scientific EffectGear meshing: Gear

Implementation Method 2

provide a low gear ratio that can be engaged and disengaged on the fly

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Implementation Method 3

a first holding member adapted to selectively hold the ring gear of the first planetary gear set to cause the first output shaft to rotate in an underdrive condition

Methodology Applied

Scientific EffectFriction braking: Friction

Data Source

PatentUS7632204B2Transfer case with low gear ratio

Publication Date: 2009.12.15 LOVELL ENG

AI summary

A transfer case is provided utilizing dual planetary gearsets to provide a low gear ratio that can be engaged and disengaged on the fly without binding of gears. The transfer case provides an option for engaging the front, rear, both front and rear, or none of the wheels of a vehicle and is especially suited for off road vehicles such as rock crawlers.