Variable Lift Fuel Injection Valve Dynamics
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Solution Overview
Problem
In direct-injection engines, high engine speeds reduce the time for fuel vaporization and air-fuel mixing, leading to increased smoke generation and poor formation of air-fuel and heat-insulating gas layers due to early fuel injection timing, which results in fuel spray reaching the combustion chamber walls.
Innovation Solution
A fuel injection control device that adjusts the lift amount of the fuel injection valve to increase the effective opening area initially, then decreases it to maintain high injection speed, allowing for efficient atomization and vaporization of fuel, thereby delaying the start of fuel injection and ensuring the air-fuel mixture forms a heat-insulating gas layer without excessive concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If fuel injection timing is advanced to ensure sufficient vaporization and mixing time at high engine speeds, then fuel vaporization and air-fuel mixing are improved, but fuel spray reaches the combustion chamber walls causing increased cooling loss
Solution Approach 1:
The patent applies dynamics by making the injection valve lift amount variable during the injection period. The lift amount is set to a larger value in the earlier period and a smaller value in the later period, creating a dynamic injection profile that adapts to different phases of fuel injection. This dynamic control allows the fuel spray characteristics to change over time, enabling sufficient vaporization and mixing while preventing wall impingement.
Solution Approach 2:
The patent changes the lift amount parameter during the injection period to optimize fuel injection performance. By varying the lift amount from larger to smaller values, the injection pressure and spray pattern are dynamically adjusted, ensuring proper fuel atomization and distribution without allowing the spray to reach the combustion chamber walls.
2Quantity of substance
If lift amount is increased to increase effective opening area and reduce injection pressure, then fuel flow rate increases, but injection speed decreases reducing atomization quality
Solution Approach 1:
The patent uses dynamic lift amount control where the lift is larger in the earlier injection period to maximize fuel flow rate, then reduces the lift in the later period to maintain high injection speed for proper atomization. This dynamic adjustment resolves the contradiction between flow rate and injection speed.
Solution Approach 2:
The injection process is divided into periodic phases with different lift amount characteristics. The earlier period uses larger lift for high flow rate, while the later period uses smaller lift for high injection speed, creating a periodic variation in injection parameters that optimizes both fuel delivery and atomization.
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 reduces smoke generation by ensuring efficient fuel vaporization and air-fuel mixing, forming a reliable air-fuel mixture layer and heat-insulating gas layer in the combustion chamber, even at high engine speeds, while preventing fuel spray from reaching the chamber walls.
Implementation Method 1
an effective opening area of an injection port through which the fuel is injected increases as a lift amount of the fuel injection valve increases... This approach reduces smoke generation by ensuring efficient fuel vaporization and air-fuel mixing
Implementation Method 2
efficient atomization and vaporization of fuel, thereby delaying the start of fuel injection and ensuring the air-fuel mixture forms a heat-insulating gas layer
Implementation Method 3
forming, in the combustion chamber, an air-fuel mixture layer and a gas layer around the air-fuel mixture layer. The engine disclosed in Patent Document 3 reduces cooling loss by allowing the gas layer around the air-fuel mixture layer to serve as a heat-insulating layer
Implementation Method 4
Fuel is injected into the cylinder in the second half of a compression stroke... the fuel is injected into the cylinder having a high pressure. As a result, this reduces the risk of the fuel spray reaching the wall surface of the combustion chamber
Data Source
AI summary
A fuel injection valve (6) is configured such that the effective opening area of an injection port (61) increases as its lift amount increases. A fuel injection control unit (an engine control unit 100) injects fuel in a lift amount changing mode wherein, when fuel is injected into a combustion chamber (17) in the terminal period of the compression stroke, the lift amount of the fuel injection valve is set to a predetermined large lift amount in the earlier period of the injection period, and in the later period of the injection period following the earlier period of the injection period, the lift amount is set to a small lift amount smaller than the large lift amount and is in a range where the fuel injection speed increases.