Interaxle Differential Friction Clutch for Slip-Tolerant Locking

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Solution Overview

Problem

Vehicle drivetrains experience drive axle slip in tandem axles due to limitations in interaxle differential (IAD) locking and lubrication systems, leading to wear, improper engagement, and torque spikes that can cause component degradation.

Innovation Solution

An interaxle differential with a friction clutch actuated by an electric motor and a planetary gearset for efficient locking and unlocking, along with a lubrication system that uses splash lubrication to efficiently route lubricant to critical components, reducing system complexity and losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a dog clutch locking device is used in the IAD, then traction is improved under certain conditions, but the locking and unlocking window is limited due to constraints on the locking device

Engineering Contradiction:

ImprovetractionVSAvoidlocking window

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the operating parameters of the locking mechanism by using a friction clutch with variable friction characteristics instead of a fixed engagement dog clutch. The friction clutch allows for progressive engagement and disengagement based on torque conditions, expanding the window of operation from a narrow locked/unlocked binary state to a continuous range of friction-based torque transfer states.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If complex lubricant passages are integrated into shafts for IAD lubrication, then component wear is reduced, but system complexity increases and flow losses occur

Engineering Contradiction:

Improvecomponent wearVSAvoidlubrication system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the lubrication function from the complex integrated shaft passages and implements it as a separate, simplified lubrication system. The lubricant is delivered through a dedicated supply passage that is easily accessible and can be serviced independently, reducing the overall system complexity while maintaining effective lubrication of the friction clutch and other components.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If separate lubricant passages are used for each component, then targeted lubrication is achieved, but system complexity and flow losses increase

Engineering Contradiction:

Improvetargeted lubricationVSAvoidflow losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent merges the lubrication delivery for multiple components into a single integrated supply passage system. The lubricant is supplied to a common accessible location where it can naturally reach the friction clutch and other components through gravity and pressure, eliminating the need for multiple separate passages and reducing flow losses while maintaining targeted lubrication effectiveness.

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If dog clutch locking is implemented, then IAD locking functionality is achieved, but torque spikes occur that can cause component degradation

Engineering Contradiction:

ImproveIAD locking functionalityVSAvoidcomponent degradation

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies beforehand cushioning by using a friction clutch that progressively engages and disengages based on torque conditions, rather than sudden dog clutch engagement. The friction plates and discs create a cushioning effect that absorbs torque shocks and prevents sudden torque spikes, protecting components from degradation while maintaining effective locking functionality when needed.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The solution enhances vehicle traction, increases IAD efficiency and longevity, and reduces the likelihood of component degradation by expanding the locking window and improving lubrication distribution.

Implementation Method 1

the bevel gear may generate splash lubrication. The splash lubricant serves a dual purpose: the first being the lubrication of the axle differential and the second being the delivery of lubricant to the supply passage inlet

Methodology Applied

Scientific EffectSplash lubrication: Fluid Spray

Implementation Method 2

A plurality of plates in the clutch are configured to disengage and engage to inhibit and permit speed differentiation between a first axle differential and a second axle differential

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11885409B2Vehicle drivetrain with interaxle differential and method for drivetrain operation

Publication Date: 2024.01.30 DANA HEAVY VEHICLE SYSTEMS GROUP LLC

AI summary

Systems and methods for an interaxle differential (IAD). In one example, the IAD comprises a locking assembly that includes a friction clutch, the friction clutch includes a clutch pack that comprises plurality of plates configured to engage and disengage to inhibit and permit speed differentiation between a first axle differential and a second axle differential. The IAD further includes a supply lubrication passage that comprises an inlet that receives a lubricant from an enclosure surrounding an input gear of an axle differential and a first outlet flowing the lubricant to a gear coupled to the clutch pack.