EV Axle Gearbox Range Shifting While Vehicle Is Moving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for shifting gear ranges in electric vehicles require the vehicle to be stopped, which is time-consuming and inefficient, and can lead to gearbox degradation due to significant speed differences between shafts during gear changes.
Innovation Solution
The method involves adjusting the speed of the electric machine coupled to the axle gearbox such that the speed of the first shaft multiplied by the gear ratio exceeds the speed of the output shaft, allowing the electric machine to free-wheel and reducing the speed difference absorbed by synchronizers or sliding engagement mechanisms, thereby minimizing gearbox degradation, and adjusting the shift fork position to facilitate gear changes while the vehicle is moving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle is stopped to change gearbox ranges, then the gear shifting can be performed safely, but the time consumption increases and operational efficiency decreases
Solution Approach 1:
The electric machine speed is adjusted in advance to create a threshold speed difference between the input shaft and output shaft before the actual gear engagement occurs. This preliminary speed adjustment prepares the gearbox for smooth engagement without requiring vehicle stoppage, thereby resolving the contradiction between safe shifting and time efficiency.
Solution Approach 2:
The patent changes the speed parameter of the electric machine dynamically during the gear shifting process. By controlling the speed difference to exceed a threshold value before engagement and then reducing it during engagement, the system enables safe gear changes while maintaining vehicle motion, thus eliminating the time loss associated with stopping the vehicle.
2Ease of operation
If the speed difference between shafts is large during gear changes, then the gear engagement can be achieved, but the gearbox degradation increases
Solution Approach 1:
The patent applies preliminary anti-action by creating a controlled threshold speed difference that actually protects the gearbox. The speed difference is maintained above a threshold during the approach phase to prevent premature engagement, then reduced below the threshold at the moment of engagement to minimize wear, thus preventing gearbox degradation while maintaining engagement capability.
Solution Approach 2:
The electric machine speed control follows a periodic pattern: increasing speed difference to exceed the threshold, maintaining it during approach, then reducing it below the threshold for engagement. This periodic modulation of speed difference enables reliable gear engagement while protecting the gearbox from excessive wear during the shifting cycle.
3Productivity
If the electric machine speed is adjusted to exceed threshold speed difference, then gear shifting can occur without stopping, but the control complexity increases
Solution Approach 1:
The control system continuously monitors the speed difference between the input shaft and output shaft, and adjusts the electric machine speed accordingly. This feedback mechanism automatically maintains the threshold speed difference requirement without complex manual intervention, enabling rapid gear shifting while managing control complexity through automated closed-loop control.
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 enables seamless gear shifting from high to low range or vice versa without stopping the vehicle, reducing the risk of gearbox degradation by minimizing speed differences and allowing for continuous operation while shifting gears.
Implementation Method 1
the electric machine may be allowed to free-wheel so that the shaft may be coupled to the output shaft via synchronizers or a sliding engagement mechanism without degrading the synchronizers or the sliding engagement mechanism. Allowing the electric machine to free wheel may allow the gearbox shaft speed to be reduced to the gearbox output shaft speed
Data Source
AI summary
Methods and system are described for changing a gear ratio of an axle gearbox that does not include friction clutches and that may or may not include synchronizers. The axle gearbox may receive propulsive force via an electric machine. The methods and systems permit the axle gearbox to be shifted from a high gear range to a low gear range while a vehicle that includes the axle gearbox is moving.