AWD Engagement Control via Preliminary Engine Power Increase

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Solution Overview

Problem

Existing All-Wheel Drive (AWD) systems experience deceleration and unsafe conversion conditions during the transition from Two-Wheel Drive (2WD) to AWD, leading to suboptimal performance and potential safety issues.

Innovation Solution

A computer program product and vehicle driveline system that uses an Electronic Control Unit (ECU) to manage torque transfer by increasing engine power stepwise and sequentially engaging the AWD coupling, minimizing the use of vehicle kinetic energy and avoiding harsh locking conditions, ensuring smooth and safe conversion without deceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the auxiliary drive axle is connected directly to the main drive shaft without preliminary acceleration, then the AWD engagement is simpler and faster, but deceleration occurs during conversion which the driver can notice and which may create unsafe conditions

Engineering Contradiction:

Improvevehicle travelling speedVSAvoidsafety of conversion

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system preliminarily accelerates the auxiliary drive axle by engaging it with the main drive shaft through the power transfer unit before full AWD engagement. This preliminary action brings the auxiliary axle up to speed, preventing deceleration during conversion and eliminating the harsh sensations noticed by the driver, thereby maintaining safety and comfort.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If engine power is increased significantly to accelerate the auxiliary drive axle, then the conversion to AWD is smoother and safer, but fuel efficiency decreases and drag losses increase

Engineering Contradiction:

Improvesafety of conversionVSAvoidfuel efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system applies partial engine power increase rather than full power, just enough to accelerate the auxiliary drive axle to the necessary speed for smooth engagement. This partial action achieves the safety and smoothness of conversion without the excessive energy consumption and fuel efficiency losses that would result from applying full engine power.

Inventive Principle:

Principle #16Partial or excessive action

3Loss of time

If the AWD coupling is engaged harshly to ensure quick conversion, then the engagement time is reduced, but component wear increases and unsafe conditions may arise

Engineering Contradiction:

Improveconversion timeVSAvoidcomponent wear

Core Design Contradiction:

Loss of timeVSObject-generated harmful factors

Solution Approach 1:

The system performs preliminary acceleration of the auxiliary drive axle before full coupling engagement. This preliminary action reduces the speed differential at the moment of engagement, allowing for a gentler coupling process that minimizes component wear while still achieving relatively quick conversion to AWD mode.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2849977B1Control strategy for AWD connection and disconnection

Publication Date: 2021.01.06 EATON INTELLIGENT POWER LTD

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AI summary

The invention relates to swichting between 2WD and 4WD of a vehicle. It is suggested to increase output power of an engine (106) when changing to 4WD. An AWD coupling (120) is opened, if not already open. To provide 4WD, a PTU clutch (108) is engaged once engine power has increased. The other couplers are sequentially engaged.