Engine Valve Timing Control for Pumping Loss Reduction
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Solution Overview
Problem
Engines face challenges in improving fuel efficiency while preventing premature ignition, which can occur due to increased compression ratios and valve overlap periods that also increase pumping loss.
Innovation Solution
A control device and method for an engine that adjusts the timing of intake and exhaust valves using variable valve operating mechanisms, with a supercharger to boost intake air, optimizing valve overlap periods based on engine speed and load to reduce pumping loss and prevent premature ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the valve overlap period is extended to improve scavenging performance and reduce hot burnt gas, then the temperature of the mixture gas can be suppressed, but the open timing of the exhaust valve is delayed and pumping loss increases
Solution Approach 1:
The patent applies dynamics by making the valve overlap period variable rather than fixed. The controller dynamically adjusts the valve overlap period based on real-time detection of engine operating conditions (such as engine speed and load), allowing the system to optimize between scavenging performance and pumping loss depending on the current operational state.
Solution Approach 2:
The patent changes the parameter of valve overlap period duration based on different operating conditions. By detecting engine operating conditions and adjusting the valve overlap period accordingly, the system optimizes the balance between reducing hot burnt gas temperature and minimizing pumping loss across various operating points.
2Use of energy by moving object
If the compression ratio is increased to improve fuel efficiency, then fuel efficiency improves, but premature ignition occurs due to excessively high temperature during compression
Solution Approach 1:
The patent converts the harmful effect of hot burnt gas into a beneficial one by utilizing it for scavenging purposes. The extended valve overlap period allows hot burnt gas to be intentionally retained in the cylinder to pre-heat the incoming mixture gas, which prevents premature ignition while maintaining fuel efficiency. This transforms the potentially harmful heat into a useful pre-heating effect.
Solution Approach 2:
The patent adjusts the valve overlap period parameter to control the amount of hot burnt gas retained in the cylinder. By optimizing this parameter based on operating conditions, the system maintains compression ratio high enough for fuel efficiency while preventing premature ignition through controlled thermal management.
3Productivity
If the valve overlap period is extended to discharge hot burnt gas, then scavenging performance improves, but the open timing of the exhaust valve is delayed
Solution Approach 1:
The patent makes the exhaust valve timing dynamic by adjusting the valve overlap period based on detected engine operating conditions. This allows the system to optimize scavenging performance at low speeds while maintaining appropriate exhaust timing at higher speeds, preventing the delay in exhaust valve open timing from becoming excessive.
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
The solution effectively reduces pumping loss and improves fuel efficiency while preventing premature ignition by optimizing valve timing and overlap periods, ensuring appropriate combustion of mixture gases across different engine speed ranges.
Implementation Method 1
a supercharger provided to the intake passage and configured to boost intake air introduced into the cylinder
Implementation Method 2
a variable intake valve operating mechanism configured to change an open timing and a close timing of the intake valve while maintaining an open period of the intake valve constant, a variable exhaust valve operating mechanism configured to change an open timing and a close timing of the exhaust valve while maintaining an open period of the exhaust valve constant
Data Source
AI summary
A control device for an engine is provided, which includes variable intake and exhaust valve operating mechanisms, a supercharger provided to an intake passage and configured to boost intake air introduced into a cylinder, and a controller. The controller drives the supercharger when the engine operates in a boosted range. The controller controls the variable intake and exhaust valve operating mechanisms so that a valve overlap period during which intake and exhaust valves open simultaneously is formed, when the engine operates in a low-speed boosted range of the boosted range where the engine speed is less than a reference speed. The controller controls the variable exhaust valve operating mechanism so that the open timing of the exhaust valve is more advanced when the engine operates in a high-speed boosted range of the boosted range where the engine speed is greater than or equal to the reference speed.