Hydraulic Clutch Priority Control for Four-Wheel Drive Responsiveness
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Solution Overview
Problem
Existing four-wheel drive vehicles face a trade-off between reducing drag torque and maintaining responsiveness when switching from a two-wheel drive state to a four-wheel drive state, with current technologies either increasing drag torque or degrading clutch responsiveness.
Innovation Solution
A four-wheel drive vehicle system that prioritizes hydraulic oil supply to the first hydraulic clutch over the second clutch during state switching, using a propeller shaft, hydraulic clutches, and a control apparatus to manage the oil supply and ensure efficient torque transmission, thereby enhancing responsiveness while minimizing drag torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the gap between clutch discs is increased to reduce drag torque, then fuel efficiency is improved, but clutch coupling and uncoupling responsiveness is degraded
Solution Approach 1:
The hydraulic unit pre-pressurizes the clutch discs before actual engagement is needed. When switching from two-wheel drive to four-wheel drive, the clutch discs are already in a pressurized state, enabling rapid engagement without requiring a large gap for responsiveness, thus maintaining both low drag torque and high responsiveness
Solution Approach 2:
The system dynamically adjusts the hydraulic pressure to the clutch discs based on driving conditions. The control unit monitors wheel speed differences and automatically adjusts clutch pressure, allowing the gap between clutch discs to be optimized for both low drag torque during cruising and rapid engagement when four-wheel drive is needed
2Speed
If hydraulic pressure is increased to improve clutch responsiveness, then switching speed is improved, but drag torque increases
Solution Approach 1:
The hydraulic unit applies pressure periodically and intermittently to the clutch discs rather than maintaining constant high pressure. Pressure is applied only when clutch engagement or disengagement is detected as necessary, reducing overall drag torque while maintaining responsiveness when needed
Solution Approach 2:
The system changes the hydraulic pressure parameter dynamically based on driving conditions. The control unit adjusts pressure levels according to wheel speed differential, vehicle speed, and acceleration demands, optimizing the balance between responsiveness and drag torque reduction
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 system effectively enhances responsiveness during state switching while suppressing an increase in drag torque, stabilizing the vehicle's traveling state and maintaining efficient torque transmission.
Implementation Method 1
a pair of hydraulic clutches each disposed between the driving shaft and a corresponding one of the auxiliary driving wheels and having a plurality of clutch plates that enable the driving force to be frictionally transmitted
Implementation Method 2
a hydraulic unit that supplies hydraulic oil to the hydraulic clutches and that brings the clutch plates into frictional contact with one another using the hydraulic oil
Data Source
AI summary
A four-wheel drive vehicle are provided which enable enhancement of responsiveness to switching from a two-wheel drive state to a four-wheel drive state. A four-wheel drive vehicle includes a driving force transmission and cut-off apparatus that enables cut-off of transmission of a driving force from an engine to a propeller shaft, a driving shaft that rotates under a tuning force of the propeller shaft, a pair of hydraulic clutches and each disposed between the driving shaft and a corresponding one of rear wheels, and a control apparatus that controls a hydraulic unit that supplies hydraulic oil to the hydraulic clutches. In shifting the two-wheel drive state to the four-wheel drive state, the control apparatus controls the hydraulic unit such that a higher priority is given to supply of the hydraulic oil to first hydraulic clutch than to supply of the hydraulic oil to second hydraulic clutch.