Disconnect Clutch Pressure Control for Faster Hybrid Engine Starts
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Solution Overview
Problem
Existing hybrid vehicle powertrain control systems face challenges in efficiently starting the engine while transferring power from an electric machine, due to delays in torque and hydraulic pressure application, which affect the reliability and efficiency of the engine start process.
Innovation Solution
A controller is programmed to close the disconnect clutch by increasing hydraulic pressure based on a model that compensates for delays between torque commands and measured torques, and adjusts the model based on differences between expected and measured hydraulic pressures during engine start, ensuring precise torque control and efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydraulic pressure is increased to transfer torque during engine start, then power transfer capability is improved, but delay between torque command and measured torque increases
Solution Approach 1:
The system pre-charges the hydraulic clutch actuator with pressure before torque transfer is needed. During engine start, the disconnect clutch can engage more quickly because the hydraulic pressure is already available, eliminating the delay between torque command and actual torque transfer while maintaining the required power transfer capability.
Solution Approach 2:
The control system dynamically adjusts hydraulic pressure based on real-time feedback from torque sensors and engine parameters. During engine start, the system optimizes pressure application rates to achieve rapid engagement while preventing excessive pressure buildup that would cause delays, adapting the pressure profile to the specific operating conditions.
2Speed
If hydraulic pressure is increased rapidly to start the engine, then engine start speed is improved, but control precision of torque decreases
Solution Approach 1:
The system uses feedback from torque sensors, hydraulic pressure sensors, and engine speed sensors to continuously monitor the engine start process. The controller adjusts hydraulic pressure in real-time based on this feedback, ensuring that rapid pressure application for quick engine start does not compromise torque control precision. The feedback loop allows the system to correct deviations and maintain precise control throughout the engagement process.
Solution Approach 2:
The control system maintains continuous monitoring and adjustment of hydraulic pressure during the entire engine start sequence. Rather than applying pressure in discrete steps, the system provides continuous pressure modulation that ensures both rapid engine start and precise torque control throughout the transition, eliminating gaps in control that would reduce precision.
3Measurement precision
If model adjustments are made during engine start based on pressure differences, then control accuracy is improved, but system complexity increases
Solution Approach 1:
The system implements feedback by continuously comparing expected hydraulic pressure (based on the model) with actual measured pressure during engine start. When deviations are detected, the controller automatically adjusts the model parameters or pressure commands to correct the discrepancy. This feedback mechanism improves control accuracy without requiring complex additional hardware, using primarily software-based model adaptation.
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 enables smoother and more efficient engine starts by accurately controlling torque and hydraulic pressure, improving the reliability and efficiency of the powertrain operation.
Implementation Method 1
The controller is further programmed to control the torque of the disconnect clutch during the engine start via increasing a hydraulic pressure applied to the disconnect clutch
Data Source
AI summary
A vehicle includes an engine, an electric machine, a disconnect clutch, and a controller. The engine and the electric machine are each configured to generate power. The disconnect clutch is disposed between the engine and the electric machine. The controller is programmed to, in response to a command to start the engine, close the disconnect clutch to transfer power from the electric machine to the engine. The controller is further programmed to control the torque of the disconnect clutch via increasing a pressure applied to the disconnect clutch based on a first-order model of the pressure applied to the disconnect clutch. The controller is further programmed to adjust the model based on a difference between an expected pressure to the disconnect clutch and a measured pressure of the disconnect clutch during a time period prior to transferring torque through the disconnect clutch.