Four-Wheel Drive Vehicle Clutch Control Logic
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Solution Overview
Problem
Four-wheel drive vehicles inaccurately determine low friction road surfaces, leading to inappropriate release of the dog clutch and inefficient power distribution, as they may mistakenly identify low friction roads as high friction roads, causing a delay in re-engaging the dog clutch and disrupting power transmission.
Innovation Solution
The vehicle temporarily releases the electronically controlled coupling to re-evaluate the road surface before releasing the dog clutch, preventing inappropriate switching from four-wheel drive to two-wheel drive when the road is determined to be low friction, allowing the electronically controlled coupling to switch faster than the dog clutch and ensuring proper power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the vehicle switches to two-wheel drive state when drive power is not transmitted to the running road surface, then the switching response is fast, but the road surface determination becomes inaccurate
Solution Approach 1:
The control device temporarily releases the electronically controlled coupling before releasing the dog clutch to create a preliminary test condition. This preliminary action allows the system to evaluate road surface friction characteristics before committing to a two-wheel drive state, ensuring accurate determination even when no drive power is currently being transmitted to the road surface.
2Speed
If the dog clutch is released immediately upon determining high friction road, then the switching speed is fast, but the vehicle experiences power distribution delay
Solution Approach 1:
The electronically controlled coupling is temporarily released as a preliminary test before the dog clutch is released. This preliminary action serves as a verification step that prevents premature switching to two-wheel drive mode, ensuring that the dog clutch is only released when road surface conditions are confirmed to be suitable, thereby avoiding power distribution delays.
3Stability of the object's composition
If the vehicle operates in four-wheel drive state continuously, then the power distribution is stable, but the energy consumption increases
Solution Approach 1:
The control device continuously monitors wheel slip conditions and uses this feedback to dynamically determine road surface friction characteristics. Based on this feedback mechanism, the system switches between four-wheel drive and two-wheel drive states appropriately, maintaining stable power distribution when needed while reducing energy consumption by disengaging the dog clutch on suitable road surfaces.
Data Source
AI summary
A four-wheel drive vehicle comprises: a dog clutch; an electronically controlled coupling; and a control device switching a drive state to the four-wheel drive state when the control device determines that a running road surface is a low friction road and switching the drive state to the two-wheel drive state when the control device determines that the running road surface is a high friction road. In the case of switching the drive state from the four-wheel drive state to the two-wheel drive state, the control device temporarily releases the electronically controlled coupling to redetermine whether the running road surface is the low friction road or the high friction road before releasing the dog clutch and prohibits switching from the four-wheel drive state to the two-wheel drive state when it is redetermined that the running road surface is the low friction road.