Wastegate Torque Limiting for Cold Engine Startup
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Solution Overview
Problem
Cold engine startup leads to increased viscosity of lubricating oil, reducing oil flow and limiting turbocharger turbine speed, which in turn restricts engine torque due to the bypassing of exhaust gas energy, necessitating a time delay in wastegate operation to prevent engine stalling.
Innovation Solution
A control system that compares engine speed and oil pressure data to thresholds, limiting engine torque by managing wastegate operation based on engine temperature and oil pressure data, ensuring adequate lubrication and preventing excessive shaft speed during engine warm-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a time delay is imposed to keep the wastegate open during cold startup, then engine torque is limited to prevent excessive shaft speed, but engine productivity is reduced due to delayed torque availability
Solution Approach 1:
The control system dynamically adjusts the wastegate opening strategy based on real-time monitoring of engine oil temperature and pressure. During cold startup, the wastegate remains open to limit torque and prevent stalling. As oil temperature and pressure increase, the system automatically transitions to normal wastegate operation, allowing full torque availability. This dynamic adaptation resolves the contradiction by making the torque limitation temporary and condition-dependent rather than fixed.
Solution Approach 2:
The control system continuously monitors engine oil temperature and pressure feedback to determine when to transition from torque-limiting mode to normal operation. When oil temperature exceeds a first threshold and oil pressure exceeds a second threshold, the system receives feedback that lubrication is adequate, and consequently closes the wastegate to restore full engine torque. This feedback mechanism ensures the contradiction is resolved based on actual engine conditions rather than fixed timing.
2Reliability
If the wastegate is kept open during cold startup, then shaft speed is minimized to protect bearings, but engine torque is limited reducing vehicle performance
Solution Approach 1:
The system dynamically transitions the wastegate from an open position during cold startup to a closed position when oil conditions improve. During the cold phase, the open wastegate limits exhaust gas energy to the turbine, minimizing shaft speed and protecting bearings. When oil temperature and pressure reach thresholds indicating adequate lubrication, the wastegate closes to maximize torque output. This dynamic position change resolves the contradiction between bearing protection and power output.
Solution Approach 2:
The control system changes the operational parameters of the wastegate based on oil temperature and pressure parameters. When oil temperature is below the first threshold or oil pressure is below the second threshold, the wastegate maintains an open state with specific opening degrees to limit torque. When both thresholds are exceeded, the wastegate parameter changes to a closed state, allowing maximum torque. This parameter-based control resolves the contradiction by linking wastegate position to lubrication conditions.
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
Effectively manages engine torque during cold starts by adjusting wastegate operation based on oil pressure and temperature, ensuring proper lubrication and preventing engine stalling, thereby improving engine start-up and reducing the need for restarts.
Implementation Method 1
a turbine through which exhaust gas exiting through the exhaust system passes and a compressor operated by the turbine
Implementation Method 2
a compressor operated by the turbine through which air that has entered the intake system passes to create the charge air
Data Source
Figure 1
Figure 2
AI summary
A control system (36) for comparing engine speed to engine speed threshold above which the engine is considered to be running (40), for comparing engine temperature to an engine temperature threshold (60), and once engine speed has become greater than the engine speed threshold, for causing engine torque to be limited to an torque limit until the first to occur of: engine temperature exceeding the engine temperature threshold, a first timer (44), started upon engine speed having become greater than the engine speed threshold, having timed to a time that is a function of engine temperature, and a second timer (54), started upon engine speed having become greater than the engine speed threshold and engine oil pressure having become greater than an engine oil pressure threshold, having timed to a time that is also a function of engine temperature.