Variable Valve Timing for Engine Intake Control
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Solution Overview
Problem
Existing engine intake controllers with fixed valve timing suffer from reduced actual compression ratios and combustion efficiency due to early closure of intake valves, leading to decreased fuel economy and potential knocking issues when using heat insulating materials at high engine loads.
Innovation Solution
A variable valve operating mechanism that adjusts valve closing timing and lift to reduce the actual compression ratio at low loads and minimize heat transfer at high loads, using a combination of variable lift and phase mechanisms to control intake valve operation, and applying heat insulating coatings to manage cooling losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the timing for closing the intake valves is advanced significantly ahead of bottom dead center to reduce pumping loss, then the pumping loss is reduced, but the actual compression ratio drops significantly causing deteriorated combustion state and reduced fuel economy
Solution Approach 1:
The patent applies variable valve timing and variable valve lift mechanisms to dynamically adjust the intake valve closing timing and lift amount based on engine operating conditions. At low loads, the valve closes significantly ahead of BDC with reduced lift to minimize pumping loss. At high loads, the valve timing and lift are optimized to maintain adequate compression ratio and combustion efficiency, thus resolving the contradiction between pumping loss reduction and fuel economy across different operating ranges.
Solution Approach 2:
The patent changes the parameters of valve timing and valve lift amount according to engine load conditions. By varying these parameters dynamically, the system achieves optimal balance between pumping loss reduction and compression ratio maintenance - advancing valve closing timing and reducing lift at low loads while maintaining more conventional settings at high loads.
2Loss of energy
If heat insulating materials are used on the wall surfaces of the combustion chambers to improve thermal efficiency, then the pumping loss reduction effect is improved, but at high engine load the temperature of the intake air inside the combustion chambers increases causing knocking
Solution Approach 1:
The patent uses dynamic valve timing and lift control to manage the interaction between heat insulating materials and intake air temperature. At high loads, the variable valve mechanism optimizes the timing and duration of valve opening to allow adequate cooling of intake air, preventing excessive temperature rise that would cause knocking, while still benefiting from the thermal efficiency improvements of heat insulating materials during combustion.
Solution Approach 2:
The variable valve timing and lift mechanism acts as an intermediary between the heat insulating materials and the intake air. It controls the exposure of hot intake air to the insulated combustion chamber walls, limiting heat transfer to prevent knocking while allowing the insulation to benefit combustion temperatures, thus mediating the conflicting thermal effects.
3Loss of energy
If the valve lift amount is reduced at low load conditions, then the pumping loss is reduced, but the intake air filling efficiency at high load must be maintained
Solution Approach 1:
The patent implements dynamic adjustment of valve lift amount based on engine load. At low loads, the valve lift is reduced to decrease the effective intake stroke and minimize pumping loss. At high loads, the valve lift amount is increased to ensure adequate intake air filling efficiency, thus dynamically resolving the contradiction between pumping loss reduction and air filling efficiency across different operating 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
This approach enhances fuel economy by maintaining combustion efficiency while reducing pumping losses and preventing knocking, by optimizing intake air temperature and compression ratios through adaptive valve control and heat management.
Implementation Method 1
adhering a heat insulating material on the wall surfaces of the combustion chambers, partially or entirely, to prevent the pumping loss reduction effect from being lost
Implementation Method 2
the intake air in the cylinders expands adiabatically to bottom dead center BDC despite the suction stroke, so that the temperature inside the cylinders also drops as the pressure inside the cylinders drops
Implementation Method 3
the actual compression begins from the point at which the in-cylinder pressure is restored. Thus, the actual compression ratio drops significantly as the timing for closing the intake valves comes further ahead of bottom dead center BDC. Because this drop in the actual compression ratio results in a significant drop in the temperature of the air-fuel mixture inside the cylinders at compression top dead center TDC
Data Source
AI summary
An engine intake control apparatus for an engine that comprises at least one combustion chamber operatively connected to an intake port and an intake valve associated with each intake port, wherein the intake valve is adapted to open and close the intake port is disclosed herein. The intake control apparatus comprises a variable valve operating mechanism and a controller. The variable valve operating mechanism is configured and arranged to selectively change a valve closing timing and a valve lift amount of the intake valve. The controller is configured and arranged to control the variable valve operating mechanism when the engine is in a low load condition. The valve closing timing is determined such that an actual compression ratio of the engine is reduced relative to the actual compression ratio when the engine is operating in a high load condition. The valve lift amount is smaller when the engine is in the low load condition relative to the valve lift amount when the engine is in the high load condition. A method for controller an engine is also disclosed.