Four-Wheel Drive Clutch Synchronization Control
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Solution Overview
Problem
In vehicular four-wheel drive systems, switching from two-wheel-drive to four-wheel-drive mode during turning causes shock due to differences in rotational speed between wheels, particularly when clutches without synchro mechanisms are engaged.
Innovation Solution
A control device with an electronic control unit synchronizes the rotation of meshing clutches using a synchro mechanism and adjusts coupling torque to match the rotational speed of secondary drive wheels, ensuring synchronized engagement of both clutches during mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the first meshing clutch and the second meshing clutch are disengaged during two-wheel driving, then fuel efficiency is improved by eliminating dragging of the propeller shaft, but shock occurs when switching to four-wheel drive during turning due to rotational speed difference
Solution Approach 1:
The synchro mechanism synchronizes the rotational speeds of the first and second meshing clutches before engagement during the transition from two-wheel drive to four-wheel drive. By preliminarily equalizing the rotational speeds, the system prevents shock during clutch engagement while maintaining the ability to disengage clutches during two-wheel drive for fuel efficiency
Solution Approach 2:
The synchro mechanism acts as an intermediary device between the first and second meshing clutches, mediating the rotational speed difference that would otherwise cause shock during engagement. It temporarily couples the clutches to equalize their speeds before full engagement occurs
2Adaptability or versatility
If the first meshing clutch and the second meshing clutch are engaged during four-wheel drive, then power transmission to all wheels is achieved, but rotational speed difference during turning causes shock at clutch engagement
Solution Approach 1:
Before engaging the meshing clutches during the transition to four-wheel drive, the synchro mechanism preliminarily synchronizes the rotational speeds of the clutches. This preliminary speed equalization eliminates the shock that would occur during engagement due to rotational speed differences caused by turning
Solution Approach 2:
The system changes the rotational speed parameter of the meshing clutches by using the synchro mechanism to equalize their speeds before engagement. This parameter adjustment ensures that both clutches engage simultaneously without shock, maintaining four-wheel drive capability while eliminating harmful vibrations
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
This approach reduces or suppresses shock during the engagement of clutches, maintaining smooth operation and reducing noise and vibration when switching from two-wheel-drive to four-wheel-drive mode during turning.
Implementation Method 1
one of the first meshing clutch and the second meshing clutch includes a synchro mechanism. The control device includes an electronic control unit configured to synchronize rotation of the above-indicated one of the first meshing clutch and the second meshing clutch including the synchro mechanism
Data Source
AI summary
When a vehicle is switched from a two-wheel-drive mode to a four-wheel-drive mode during turning, rotation of a Rr dog clutch is synchronized by a synchro mechanism. Rotation of a Fr dog clutch is synchronized, by controlling coupling torque of a control coupling that transmits power to a rear wheel that provides an outer wheel during turning. Thus, rotation of the Fr dog clutch is also synchronized, so that shock at the time of engagement of the Fr dog clutch can be suppressed.