Engine Intake Valve Timing Control for Combustion Stability
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Solution Overview
Problem
Existing engine intake valve timing control systems face challenges in stabilizing combustion due to varying fuel vaporization rates at the intake port, leading to engine stalling issues caused by abrupt changes in air-fuel ratio, especially at low coolant temperatures.
Innovation Solution
An engine intake valve timing control system that adjusts the valve timing change rate based on engine coolant temperature, using fuel injection control and valve timing change rate setting mechanisms to limit advancement or retardation rates, and incorporates a delay time to stabilize combustion by ensuring gradual changes in valve timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the valve timing change rate is adjusted in accordance with the engine speed, then the torque performance in low to medium vehicle speed regions and output power in high vehicle speed regions is improved, but the fuel vaporization rate varies depending on the operating state, causing engine stalling
Solution Approach 1:
The patent applies parameter changes by adjusting the valve timing change rate based on coolant temperature. When coolant temperature is low, the valve timing change rate is limited to prevent abrupt changes in air-fuel ratio that would cause poor fuel vaporization and engine stalling. This dynamic parameter adjustment resolves the contradiction by maintaining power performance while ensuring combustion stability across different operating conditions.
2Speed
If the valve open/close timing is changed abruptly to improve response, then the engine can adapt quickly to operating conditions, but the engine may stall due to sudden changes in air fuel ratio
Solution Approach 1:
The patent implements dynamics by making the valve timing change rate adaptive rather than fixed. The control system dynamically adjusts the maximum allowable change rate based on real-time coolant temperature measurements. This allows the system to respond quickly when conditions permit while preventing stalling when fuel vaporization is sensitive, thus resolving the contradiction between response speed and operational stability.
3Productivity
If the valve timing control angle is updated frequently to maintain optimal performance, then engine efficiency is improved, but the fuel adhered to the intake port may not vaporize properly, causing air fuel ratio variations
Solution Approach 1:
The patent applies parameter changes by modifying the valve timing update frequency and magnitude based on coolant temperature. When the engine is cold, the system reduces the frequency and magnitude of timing updates to allow proper fuel vaporization. As the engine warms up, updates become more frequent and aggressive, maintaining efficiency without compromising air-fuel ratio consistency. This resolves the contradiction between productivity and reliability.
Data Source
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AI summary
An engine intake valve timing control apparatus includes a fuel injection control section, a valve open timing control section, and a valve timing change rate setting section. The fuel injection control section is configured to control a fuel injection quantity of fuel injected from a fuel injector into an intake port of an engine in accordance with an operating condition of the engine. The valve open timing control section is configured to control an open timing (VTC) of an intake valve to a target open timing (VTCTO). The valve timing change rate setting section sets a change rate at which the open timing of the intake valve is changed from a current open timing to the target open timing (S2) when the target open timing is updated (S1), the change rate being set using a parameter relating to a vaporization rate of the fuel adhered to the intake port.