Auxiliary Cam Assembly for Engine Brake Valve Timing
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Solution Overview
Problem
Existing decompression engine brake systems face difficulties in avoiding interference between valves and pistons during cam shifting, particularly when using hydraulic lash adjustment, which is costly and space-intensive, and require complex synchronization.
Innovation Solution
An auxiliary command assembly that activates an auxiliary cam profile by moving the reference point of the rocker arm or finger follower, allowing partial overrunning of the normal cam's commanding action without shifting the camshaft, using a hydraulic or mechanical actuator to maintain constant loading of hydraulic lash adjustment (HLA) and prevent unwanted extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If axial shifting of the cam shaft is used to enable different profiles for engine braking, then decompression engine brake operation is achieved, but interference between valve and pistons occurs during cam shifting
Solution Approach 1:
The camshaft system is segmented into a normal cam profile and an auxiliary cam profile. The auxiliary cam is independently positioned and activated only when needed for engine braking, allowing it to operate separately from the normal cam without interfering with piston motion. This segmentation enables the system to achieve decompression braking while avoiding valve-piston interference.
Solution Approach 2:
The auxiliary cam is pre-positioned and pre-configured in a retracted state during normal operation. When engine braking is required, the reference point is shifted to activate the auxiliary cam profile in advance, ensuring that the valve timing is adjusted before any potential interference could occur with piston motion.
2Adaptability or versatility
If axial shifting of the cam shaft is used for decompression engine brake, then different cam profiles are enabled, but costs and space requirements increase
Solution Approach 1:
The auxiliary cam profile is extracted as a separate, independent component from the main camshaft. Instead of shifting the entire camshaft axially to change profiles, the auxiliary cam is positioned separately and activated only when needed. This extraction simplifies the overall mechanism, reducing both cost and space requirements while maintaining the ability to switch between normal and braking profiles.
Solution Approach 2:
The auxiliary cam serves multiple functions: it enables decompression engine braking, allows internal EGR strategy, and can be used for other operational modes. This multi-functionality is achieved through a single auxiliary cam component that can be activated for various purposes, reducing the need for multiple separate mechanisms and thereby lowering overall system complexity and cost.
3Ease of operation
If hydraulic lash adjustment (HLA) is used for valve lash control, then valve lash can be adjusted, but HLA increases its natural extension when compressed, forcing valve opening and causing interference
Solution Approach 1:
The reference point is shifted in advance to activate the auxiliary cam profile before the HLA is compressed. This preliminary action ensures that the auxiliary cam begins commanding valve opening earlier, allowing the HLA to remain constantly loaded and compressed without experiencing unwanted extension that would force premature valve opening and cause interference with piston motion.
Solution Approach 2:
The system dynamically adjusts the reference point position based on operational requirements. During engine braking or internal EGR modes, the reference point is shifted to maintain constant HLA loading. This dynamic positioning ensures that the HLA operates in a controlled manner, preventing unwanted extension and maintaining reliable valve timing control throughout different engine modes.
4Adaptability or versatility
If cam shaft is shifted for decompression engine brake, then auxiliary cam profile is activated, but synchronization issues arise
Solution Approach 1:
The camshaft system is segmented into independent normal cam and auxiliary cam components. The auxiliary cam is positioned separately and activated independently through reference point shifting, eliminating the need for complex synchronization control between camshaft positions. This segmentation allows each cam profile to operate autonomously without requiring precise coordination, thereby reducing device complexity.
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 prevents interference between valves and pistons, reduces costs and space requirements, and allows for decompression engine braking without synchronizing camshaft shifts, while maintaining constant HLA loading, enabling efficient engine operation.
Implementation Method 1
using a hydraulic or mechanical actuator to maintain constant loading of hydraulic lash adjustment (HLA)
Implementation Method 2
maintain constant loading of hydraulic lash adjustment (HLA) and prevent unwanted extension
Data Source
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AI summary
Auxiliary command assembly for commanding the opening/closing of the head valves (IV, EV) of a combustion engine, in particular for a decompression engine brake operation comprising an oscillating arm (FF, RA) having a second end (2) in contact with a valve stem, for pushing it axially during an opening procedure of the same, a normal cam (C) commanding said oscillation, a reference point (RP) defining a fulcrum of said oscillation of the oscillating arm (FF, RA), the auxiliary command assembly comprising an auxiliary cam (AC) suitable to be driven by the combustion engine crankshaft, an auxiliary roller, suitable to follow the profile of said auxiliary cam (AC) an actuator assembly (A) suitable to lift/lower said reference point (RP), means for interconnecting said actuator (A) and said auxiliary roller (AR) during an auxiliary engine operating condition, by at least partially overrunning of the commanding action of said normal cam (C).