Cam-Driven Exhaust Valve Control for EGR
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Solution Overview
Problem
Current internal combustion engine technologies face challenges in effectively reducing nitrogen oxide (NOx) emissions through exhaust gas recirculation, as existing methods require high hydraulic pressure and complex implementations for additional exhaust valve openings.
Innovation Solution
A control arrangement and method for a cam-driven exhaust valve that utilizes a cam with a base circle and radially extending lobe, a reciprocating cam follower unit, and a hydraulic fluid chamber, allowing an additional opening for exhaust gas recirculation without high hydraulic pressure, using a portion below the base circle to prevent outflow and introduce hydraulic fluid for reopening the valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second lobe cam or movable cam lobe is used for additional exhaust valve opening, then exhaust gas recirculation is enabled, but device complexity increases
Solution Approach 1:
The cam profile is segmented into distinct functional zones: a base circle for normal operation, a lobe for primary valve opening, and a portion below the base circle for triggering secondary opening. This segmentation allows each zone to perform a specific function, enabling exhaust gas recirculation without requiring a completely separate second lobe or movable cam mechanism.
Solution Approach 2:
The invention merges the EGR function with the existing single cam structure by incorporating a portion below the base circle into the same cam body. This combines the normal exhaust valve operation and the EGR-specific additional opening into one integrated cam mechanism, avoiding the complexity of separate second lobes or movable cam lobes.
2Adaptability or versatility
If hydraulic pressure is increased for additional valve opening, then valve reopening is achieved, but energy consumption increases
Solution Approach 1:
The cam follower wheel is positioned to engage with the portion below the base circle in advance of the main lobe action. This preliminary engagement triggers the hydraulic actuation early in the cam rotation cycle, allowing the valve to be reopened before the main exhaust stroke begins, thereby achieving EGR without requiring excessive hydraulic pressure during the power stroke.
3Reliability
If a portion below the base circle is used for cam follower engagement, then outflow prevention is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The cam profile geometry itself serves the dual function of both actuating the cam follower wheel and preventing hydraulic fluid outflow. The portion below the base circle is designed such that cam follower engagement with this portion automatically creates the sealing action needed to contain hydraulic fluid, eliminating the need for separate sealing mechanisms and reducing manufacturing precision requirements for separate sealing features.
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 provides a reliable and simple method for additional exhaust valve opening, enabling effective exhaust gas recirculation with reduced NOx emissions without the need for high hydraulic pressure, and allows for adjustable valve lift and closing speed, enhancing engine efficiency.
Implementation Method 1
a hydraulic fluid chamber that is arranged between the cam and the force transmission means, means for introducing hydraulic fluid into the hydraulic fluid chamber, and means for discharging hydraulic fluid from the hydraulic fluid chamber
Data Source
Figure 1~2
Figure 3~4
AI summary
The control arrangement and method allow an additional opening of a cam-driven exhaust valve (17) of an internal combustion engine for exhaust gas recirculation. Hydraulic fluid can be introduced into a hydraulic fluid chamber (11) that is arranged between a cam (2) and force transmission means (12, 18) and delimited by a piston (5) that is engaged with the force transmission means (12, 18) at least during the opening and closing movement of the exhaust valve (17). The cam (2) comprises a portion (2c) below the base circle (2a) of the cam (2), and engagement of a cam follower wheel (3) with the portion (2c) below the base circle (2a) is arranged to prevent outflow from the hydraulic fluid chamber (11).