Transfer Gearbox Torque Distribution via Shifting Unit

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Solution Overview

Problem

Existing four-wheel drive systems face challenges in efficiently managing torque distribution between front and rear axles due to rotational speed differences and wear issues, particularly with friction clutch-based systems, which limit dynamic performance and increase fuel consumption.

Innovation Solution

A vehicle with a longitudinally arranged engine and permanent rear axle drive, utilizing a transfer gearbox with a reduction gearbox and power summation gearbox, along with a shifting unit that allows for variable torque distribution between the front and rear axles, using a combination of frictionally locking and positively locking connections to manage torque and rotational speed differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If friction clutch-based transfer cases are used to enable variable torque distribution, then torque distribution flexibility is improved, but wear and rotational speed difference handling deteriorate

Engineering Contradiction:

Improvetorque distribution flexibilityVSAvoidwear resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces the friction clutch-based mechanical system with a gear-based mechanical system. The transfer gearbox uses gear mechanisms (including a friction clutchless design with gear teeth engagement) to achieve torque distribution, eliminating the wear problems associated with friction clutches while maintaining variable torque distribution capability through gear selection and engagement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediate shaft as a mediator between the input and output shafts. This intermediate shaft, equipped with gear mechanisms, serves as a torque distribution hub that can selectively engage different gears to control torque flow to front and rear axles, providing a wear-free intermediary solution for torque management.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If friction clutch is fully engaged for four-wheel drive operation, then torque distribution to secondary shaft is improved, but fuel consumption increases

Engineering Contradiction:

Improvetorque distribution capabilityVSAvoidfuel consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent implements a dynamic torque distribution system where the gear mechanisms can selectively engage or disengage based on driving conditions. The system can dynamically switch between two-wheel drive and four-wheel drive modes, and even provide partial torque distribution to the secondary shaft, optimizing power delivery and reducing energy consumption during light-load conditions while maintaining adequate torque distribution when needed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of the torque distribution system by allowing variable engagement states of the gear mechanisms. Instead of a binary fully-engaged/friction clutch state, the system can adjust torque distribution ratios by engaging different gear combinations, enabling efficient parameter optimization that reduces fuel consumption during low-demand situations while maintaining power availability when required.

Inventive Principle:

Principle #35Parameter changes

3Force

If friction plate clutch is used with high frictional coefficient, then torque transmission is improved, but torque distribution is limited due to kinematic tire slippage

Engineering Contradiction:

Improvetorque transmissionVSAvoidtorque distribution range

Core Design Contradiction:

ForceVSAdaptability or versatility

Solution Approach 1:

The patent replaces the friction-based torque transmission system with a gear-based positive engagement system. The gear teeth provide deterministic torque transmission without relying on friction coefficients, eliminating the limitation where high frictional coefficients constrained torque distribution range. The gear mechanism can transmit torque efficiently across a wide range of distribution ratios without being constrained by tire slippage kinematics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration enables precise torque distribution between the front and rear axles, reducing wear and improving vehicle dynamics while allowing for efficient operation in various driving modes, including four-wheel drive and recuperation.

Implementation Method 1

a shifting unit (50) is installed between the reduction gearbox (12) and power summation gearbox (11)... using a combination of frictionally locking and positively locking connections to manage torque and rotational speed differences

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11273707B2Vehicle comprising transfer case and method for operating said vehicle

Publication Date: 2022.03.15 MAGNA POWERTRAIN AG & CO KG

AI summary

A vehicle having a longitudinal engine and permanent rear axle drive is proposed, which vehicle has an internal combustion engine and an electric machine, a transfer gearbox distributing drive torques as required to two drive axles, the transfer gearbox having three shafts, a main shaft serving as a drive shaft of the rear axle, a secondary shaft serving as a drive shaft for the front axle, and an intermediate shaft applying a torque, a shifting unit being installed between the reduction gear-box and the power summation gearbox.