All-Wheel Drive Clutch Control for NVH Reduction
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Solution Overview
Problem
All-wheel drive vehicle systems face challenges in efficiently reconnecting drivetrain components to optimize power transfer and reduce parasitic losses, leading to increased fuel economy and decreased driver discomfort.
Innovation Solution
The system includes a driveshaft selectively coupled to first and second axles via clutches, with a controller that adjusts slip speeds and closes clutches to transfer loads and optimize power transfer, minimizing engagement time and noise, vibration, and harshness (NVH) by maintaining slip speeds within a target range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the clutch is quickly engaged to reconnect the driveshaft to the axle, then the power transfer efficiency is improved and parasitic losses are reduced, but noise, vibration, and harshness (NVH) increase due to high slip speeds
Solution Approach 1:
The system performs preliminary actions by adjusting the slip speed to a target range before fully engaging the clutch. The controller monitors slip speed and makes preliminary adjustments to minimize NVH before the final connection, ensuring a smooth engagement process that reduces harmful vibrations and noises while maintaining efficient power transfer.
Solution Approach 2:
The system dynamically adjusts the clutch engagement process by continuously monitoring slip speed and modifying engagement characteristics in real-time. The controller dynamically controls the clutch actuator to maintain slip speed within a target range during engagement, optimizing the balance between power transfer efficiency and NVH reduction throughout the engagement process.
2Object-affected harmful factors
If the clutch engagement time is extended to reduce NVH, then noise and vibration decrease, but the parasitic losses increase and fuel economy deteriorates
Solution Approach 1:
The system changes the slip speed parameter during clutch engagement by actively controlling it within a target range. This parameter change allows the clutch to engage in a controlled manner that reduces NVH without excessively extending engagement time, thereby minimizing parasitic losses while achieving smooth power transfer and improved fuel economy.
3Loss of time
If high slip speeds are used during clutch engagement, then the engagement time is reduced and power transfer is faster, but NVH increases significantly
Solution Approach 1:
The system employs feedback control by continuously monitoring the actual slip speed during clutch engagement and comparing it to the target range. The controller uses this feedback information to adjust the clutch actuator in real-time, ensuring slip speed remains within the optimal range that minimizes NVH while maintaining acceptable engagement time for efficient power transfer.
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 solution enhances the efficiency of power transfer in all-wheel drive vehicles, reducing parasitic losses, improving fuel economy, and minimizing NVH, thereby enhancing vehicle performance and driver comfort.
Implementation Method 1
adjust the slip speed of the first clutch to within a target range
Implementation Method 2
close the second clutch to transfer loads from the second axle to the driveshaft
Data Source
AI summary
A vehicle includes a driveshaft, first axle, second axle, first clutch, second clutch, and controller. The driveshaft is selectively coupled to outputs of the first and second axles by the first and second clutches, respectively. The controller is programmed to, in response to a command to reconnect the driveshaft to the outputs of the first and second axles, close the second clutch to transfer loads from the second axle to the driveshaft, adjust the slip speed of the first clutch to within a target range, and close the first clutch.