Electric Machine Speed Control for Transmission Clutch Engagement
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Solution Overview
Problem
In hybrid and electric vehicles with automatic step-ratio transmissions, the delay in engaging clutches when shifting from Park or Neutral to Drive or Reverse is significant due to insufficient line pressure from auxiliary oil pumps, leading to delayed wheel torque delivery.
Innovation Solution
A controller manages an electric machine to operate in a higher gain speed control mode until reaching a first speed threshold, then transitions to a lower gain mode, and uses an auxiliary pump to ensure timely clutch engagement, reducing delay and maintaining smooth torque delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric machine is stopped when the transmission is in Park or Neutral to conserve energy, then energy consumption is reduced, but line pressure from the auxiliary oil pump is insufficient to quickly engage the shifting clutches
Solution Approach 1:
The controller operates the electric machine in advance to build up line pressure in the transmission system before clutch engagement is needed. When a gear selection change is detected, the controller activates the electric machine to rotate the transmission pump and generate sufficient line pressure before the actual clutch engagement occurs, thereby reducing engagement delay while maintaining energy conservation during idle periods
Solution Approach 2:
The controller dynamically adjusts the operation of the electric machine based on real-time driving conditions and gear selection state. The system transitions between stopped and running states of the electric machine, and adjusts controller gain dynamically (higher gain during pressure buildup, lower gain during normal operation) to optimize both energy consumption and response time
2Loss of time
If the electric machine operates with higher controller gain to quickly build line pressure, then clutch engagement delay is reduced, but torque disturbances may be introduced
Solution Approach 1:
The controller changes the control parameter (controller gain) dynamically based on the operating phase. Higher controller gain is applied during the initial pressure buildup phase to reduce engagement delay, while lower controller gain is used during normal operation to prevent torque disturbances. This parameter adjustment allows the system to optimize performance at different stages of operation
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 significantly reduces gear engagement delay and ensures fast, intuitive wheel torque delivery without introducing torque disturbances, leveraging the electric machine's aggressive control to quickly spin up and engage clutches efficiently.
Implementation Method 1
an electric machine selectively coupled to the transmission
Implementation Method 2
a main pump powered by the electric machine and supplying oil to actuate selected ones of the plurality of hydraulically actuatable transmission clutches
Data Source
AI summary
A vehicle includes a step-ratio automatic transmission having clutches engageable to provide forward and reverse gears, an electric machine selectively coupled to the transmission, a main pump powered by the electric machine and supplying oil to actuate selected transmission clutches, a gear selector configured for selecting a transmission gear, and a controller configured to stop the electric machine when the gear selector selects park or neutral, to operate the electric machine in a speed control mode using a higher controller gain in response to the gear selector selecting forward or reverse while the electric machine is stopped until the electric machine and the main pump reach a first speed threshold to reduce engagement delay of at least one of the transmission clutches, and to operate the electric machine using a lower controller gain when the electric machine and the main pump exceed the first speed threshold.