CVT-DGT Powertrain Gear Synchronization Method
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicles with large transmission ratio differences between gears, operators must stop the vehicle to engage gears, leading to an inconvenient driving experience due to the significant difference in rotation speeds and torque between high and low gears.
Innovation Solution
A method for changing gear configurations in a vehicle powertrain using a continuously variable transmission (CVT) and discrete gear transmission (DGT), where the engine control unit (ECU) synchronizes the input and output shafts by adjusting engine speed to smoothly transition between gear configurations without stopping the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the transmission ratio changes by a factor of two or more when the gear is changed, then the torque provided to the wheels increases in low gear, but the operator has to stop the vehicle momentarily before engaging a desired gear
Solution Approach 1:
The system dynamically changes the engine speed parameter to match the target driven pulley speed calculated for the desired gear ratio. This parameter adjustment enables smooth transition between gears with large ratio differences without requiring vehicle stoppage, while maintaining the torque benefits of low gear.
Solution Approach 2:
The control unit calculates the target driven pulley speed in advance based on the desired gear driving configuration before actually engaging the gear. This preliminary calculation of the required speed parameter allows the system to prepare for smooth gear engagement without interrupting vehicle motion.
2Ease of operation
If the operator stops the vehicle momentarily to engage a different gear, then the gear engagement becomes smoother, but the driving experience becomes inconvenient and productivity decreases
Solution Approach 1:
The system maintains continuous vehicle operation by dynamically adjusting engine speed to match the requirements of the desired gear configuration. The control unit continuously monitors current engine speed, driven pulley speed, and desired gear ratio to maintain uninterrupted power transmission and vehicle motion throughout the gear change process.
3Reliability
If the engine speed is not synchronized with the driven pulley speed during gear change, then the gear engagement becomes difficult or impossible, but the vehicle operation is interrupted
Solution Approach 1:
The control unit continuously monitors the current engine speed and driven pulley speed, comparing them against the target driven pulley speed calculated for the desired gear configuration. This feedback mechanism allows real-time adjustment of engine speed to achieve synchronization, ensuring reliable gear engagement without interrupting vehicle operation.
Data Source
AI summary
A method for changing a gear driving configuration of a discrete gear transmission (DGT) in a powertrain including an engine operatively connected to a continuously variable transmission (CVT). The DGT has a DGT input shaft operatively connected to a CVT driven pulley, a plurality of gears having a plurality of gear driving configurations and a DGT output shaft selectively operatively connected to the DGT input shaft based on the gear driving configuration. Responsive to a gear shift request, a target driven pulley speed is determined for synchronizing the DGT input shaft with the DGT output shaft for the desired gear driving configuration. The engine is controlled to change an engine speed to the target engine speed corresponding to the determined target driven pulley speed. Responsive to the DGT input shaft being synchronized with the DGT output shaft, the current gear driving configuration is changed to the desired gear driving configuration.