Engine Brake Valve Sequencing for Intake Counterflow Control
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Solution Overview
Problem
State-of-the-art engine braking systems experience excessive loading on the intake valve train due to premature intake valve lift against high combustion chamber pressures, leading to undesirable consequences like counter flow in the intake manifold and surge of the upstream turbocharger.
Innovation Solution
Implement systems and methods for managing intake flow path pressure and counter flow by controlling valve motion sequencing, using components like an intake throttle, EGR valve, intake manifold blow-off valve, and turbocharger geometry to prevent excessive intake valve train forces through proactive brake motion activation and delayed main event deactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If brake motion activation occurs before main event deactivation in enhanced engine braking systems, then engine braking effectiveness is improved, but excessive loading occurs on the intake valve train due to premature intake valve lift against high combustion chamber pressures
Solution Approach 1:
The system performs preliminary action by activating brake motion before main event deactivation to ensure proper valve sequencing. The lost motion device is pre-positioned and the braking piston is activated in advance, allowing the intake valve to remain closed during compression stroke while exhaust valve opens for braking, preventing premature intake valve lift and excessive loading on the intake valve train.
2Manufacturing precision
If main event exhaust motion is deactivated prematurely before braking piston reaches steady state position, then valve timing control is improved, but high-pressure pulses occur in the intake manifold causing counter flow and turbocharger surge
Solution Approach 1:
The lost motion device serves as an intermediary mechanism between the cam-driven valve train and the hydraulic braking piston. It decouples the timing of main event deactivation from brake activation, allowing precise control of valve timing while preventing harmful counter flow by ensuring the braking piston reaches steady state before intake valve lift occurs.
3Adaptability or versatility
If lost motion devices are used to facilitate auxiliary event valve movement, then valve motion flexibility is improved, but device complexity increases due to additional hydraulic components and sequencing mechanisms
Solution Approach 1:
The lost motion device performs multiple functions: it enables main event valve operation, facilitates auxiliary braking events, and provides transient pressure management. By integrating these functions into a single mechanism with hydraulic actuation, the system achieves valve motion flexibility without proportionally increasing complexity, as the same hydraulic circuit serves multiple valve control purposes.
Data Source
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AI summary
Systems and methods for managing excessive intake flow path pressure and counter flow are implemented to support enhanced engine braking applications, such as 2-stroke or 1.5-stroke engine braking implementations where the intake flow path may be exposed to excessive transient pressures in the combustion chamber during activation or deactivation of an engine brake. Intake throttle, exhaust gas recirculation (EGR) valve, intake manifold blow-off valve, compressor bypass valve, exhaust throttle, turbocharger geometry or turbocharger waste gate may be controlled to effectuate counter flow management separately or in combination. Excessive transient conditions may also be prevented or managed by sequential valve motion in which brake motion activation occurs first and then exhaust valve main event deactivation occurs second. Delay between brake activation and main event deactivation may be facilitated using mechanical and/or hydraulic implements as well as electronically.