Dual Throttle Control for Balanced Fresh Air and EGR Gas Supply
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Solution Overview
Problem
Existing naturally aspirated gasoline engines face challenges in accurately controlling the balance of fresh air and EGR gas supply across a wide load range, leading to difficulties in achieving the required EGR rate and fuel economy, especially during low and high load operations.
Innovation Solution
The implementation of a control apparatus with two throttles in the intake passage, where the EGR gas recirculation site is downstream of the upstream throttle, and an EGR valve, allowing for precise control of fresh air and EGR gas supply by adjusting the degree of opening of each throttle and valve based on the engine's load state, ensuring a balanced mixture across various load ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the EGR gas recirculation site is located downstream of the throttle, then the throttle can control the quantity of fresh air supplied into the cylinder, but the throttle also affects the quantity of EGR gas introduced into the intake passage, making it difficult to control the EGR gas quantity accurately when negative pressure is high
Solution Approach 1:
The patent divides the single throttle control function into two separate throttles: an upstream throttle for controlling fresh air quantity and a downstream throttle for controlling EGR gas quantity. This segmentation allows independent control of each gas flow, resolving the interference between fresh air and EGR gas quantity control that occurs with a single throttle downstream of the EGR recirculation site.
2Use of energy by moving object
If the degree of opening of the throttle is made small to reduce the quantity of fresh air supplied into the cylinder during low load operation, then fuel economy is improved, but the negative pressure in the intake passage increases, making it difficult to control the quantity of recirculated EGR gas accurately
Solution Approach 1:
By placing the EGR recirculation site upstream of the downstream throttle and providing independent control of the downstream throttle, the system can maintain small upstream throttle opening for fuel economy while using the downstream throttle to regulate EGR gas flow independently, preventing the negative pressure effect from interfering with EGR control.
3Productivity
If a relatively large volume of space in the intake passage downstream of the throttle is provided to utilize the intake pulsation effect for high load operation, then fresh air supply is improved, but the EGR gas mixing with fresh air becomes more difficult
Solution Approach 1:
The patent introduces a spatial dimension by providing a separate EGR passage that merges with the intake passage upstream of the downstream throttle. This allows EGR gas to enter the large-volume intake passage from a different location and direction, improving mixing efficiency despite the large space volume required for intake pulsation effects.
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 solution enables well-balanced supply of fresh air and EGR gas according to the engine's load, improving fuel economy, reducing emissions, and enhancing engine response and efficiency across low, middle, and high load ranges.
Implementation Method 1
the exhaust gas is recirculated by the EGR apparatus under the influence of a negative pressure created in the intake passage due to closing-down of the throttle
Implementation Method 2
it is necessary to supply into the cylinder a large quantity of fresh air corresponding to the required load. It is known to utilize the intake pulsation effect for this purpose
Data Source
AI summary
An object is to supply fresh air and EGR gas into a cylinder in good balance according to the required load in a naturally aspirated gasoline engine. When the operation state of the engine falls in a low load range, a control apparatus adjusts the degree of opening of the second throttle while keeping the first throttle fully open and controls EGR gas quantity by adjusting the degree of opening of the EGR valve. When the operation state falls in a middle load range, the apparatus controls EGR gas quantity by adjusting the degree of opening of the first throttle while keeping the EGR valve fully open. When the operation state falls in a high load range, the apparatus adjusts the degree of opening of the first throttle while keeping the second throttle fully open and controls EGR gas quantity by adjusting the degree of opening of the EGR valve.