4WD Drive Force Distribution Switching for Traction and Handling
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Solution Overview
Problem
Conventional driving force control apparatuses for four-wheel drive vehicles struggle to achieve both excellent traction performance and handling performance simultaneously, especially on low-friction surfaces like snow.
Innovation Solution
The apparatus determines a front and rear wheel drive distribution ratio based on standard driving acceleration, switching between dynamic load ratio distribution control and rear wheel-biased distribution control. This allows for optimal traction performance during high acceleration/deceleration and improved handling performance during low acceleration/deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the front and rear wheel drive distribution is set to approximately half front and half rear for optimal traction performance on low-friction surfaces, then traction performance is improved, but handling performance deteriorates due to non-constant steering characteristics requiring fine correction
Solution Approach 1:
The patent applies dynamics by making the front and rear wheel drive distribution ratio changeable based on driving conditions. The control apparatus dynamically adjusts the drive force distribution between front and rear wheels according to detected acceleration and steering angle, transitioning between a 50:50 distribution for traction and a rear-wheel-biased distribution for handling, thereby resolving the contradiction between fixed traction optimization and variable handling requirements
Solution Approach 2:
The patent changes the parameter of drive force distribution ratio based on driving conditions. By detecting acceleration and steering angle, the system adjusts the front and rear wheel drive distribution from approximately 50:50 to a rear-wheel-biased ratio, optimizing both traction and handling performance through parameter adaptation rather than fixed configuration
2Ease of operation
If the front and rear wheel drive distribution is biased to front or rear for improved handling characteristics, then steering characteristics become more predictable, but traction performance deteriorates on low-friction surfaces
Solution Approach 1:
The system dynamically switches between drive distribution modes based on detected driving conditions. During low-acceleration steering maneuvers, it adopts a rear-wheel-biased distribution for improved handling. During high-acceleration conditions, it transitions to a 50:50 distribution to maximize traction, thereby adapting to different performance requirements in real-time
Solution Approach 2:
The control apparatus performs preliminary assessment of driving conditions through acceleration and steering angle detection before adjusting the drive force distribution. This allows the system to proactively optimize the drive ratio for upcoming maneuvers, ensuring both traction and handling performance are maintained before the actual driving demand occurs
Data Source
AI summary
A driving force control apparatus (1) is configured to determine a front and rear wheel drive distribution which is a ratio of driving force between front wheels (21) and rear wheels (22) in a four-wheel drive vehicle, and configured to calculate positive or negative standard driving acceleration (XG) obtained based on an input amount from a driving force instruction device (42) of the vehicle and a vehicle speed, and based on the standard driving acceleration (XG), switch between and perform dynamic load ratio distribution control that determines the front and rear wheel drive distribution in accordance with a dynamic load ratio distribution curve (L1) which is a curve of a dynamic load ratio applied to the front wheels and the rear wheels with respect to the standard driving acceleration (XG), and rear wheel-biased distribution control that determines the front and rear wheel drive distribution in accordance with a rear wheel-biased distribution curve (L2) which increases a rear wheel drive distribution compared to the dynamic load ratio distribution curve.