Lost-Motion Hydraulic Lash Adjuster for Engine Brake Valve Closure
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Solution Overview
Problem
Existing engine braking systems with hydraulic lash adjusters (HLAs) cause the exhaust valve to remain open after an engine braking event, leading to potential engine damage or inoperability.
Innovation Solution
A valve train arrangement incorporating a lost-motion hydraulic lash adjuster (LMHLA) that engages with the exhaust valve and camshaft, allowing the exhaust valve to open during engine braking and close upon deactivation, with a specific geometry and spring configuration to ensure proper lash adjustment and valve closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hydraulic lash adjuster (HLA) is used in an engine braking system, then the HLA can compensate for lash during normal operation, but the exhaust valve remains open after the engine braking event causing engine damage or inoperability
Solution Approach 1:
The HLA is divided into two distinct plungers: a conventional plunger and a lost-motion plunger. Each plunger serves a specific function - the conventional plunger handles normal lash adjustment while the lost-motion plunger specifically manages the engine braking event by allowing excess stroke to be absorbed without transmitting force to the exhaust valve, preventing the valve from remaining open.
Solution Approach 2:
The lost-motion plunger is designed with a stroke greater than the exhaust valve travel during engine braking, creating a dynamic system where the plunger can extend to accommodate the valve movement during braking events. This dynamic design allows the HLA to transition between different operational states - normal operation mode and engine braking mode - ensuring proper valve closure after braking events.
2Ease of operation
If a hydraulic lash adjuster compresses during engine braking to accommodate lash, then lash is compensated, but the HLA becomes unable to compress as the exhaust valve closes causing the valve to remain open
Solution Approach 1:
By segmenting the HLA into two plungers with different stroke characteristics, the system can independently manage lash compensation and valve closure functions. The lost-motion plunger with greater stroke handles the expansion phase during engine braking, while the conventional plunger maintains the compression capability needed for proper valve closure.
Solution Approach 2:
The lost-motion plunger acts as an intermediary element between the hydraulic fluid and the exhaust valve during engine braking events. It absorbs the excess motion and prevents direct transmission of force that would keep the valve open, while still allowing the conventional plunger to maintain hydraulic pressure for proper valve closure.
3Volume of moving object
If the lost-motion plunger stroke is less than the exhaust valve travel during engine braking, then the HLA structure remains compact, but the exhaust valve cannot close properly after the braking event
Solution Approach 1:
The critical parameter change is setting the lost-motion plunger stroke to be greater than the exhaust valve travel during engine braking events. This parameter change ensures that the plunger can fully accommodate the valve movement during braking while maintaining the ability to compress for proper valve closure, resolving the contradiction between compact size and reliable operation.
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 LMHLA effectively prevents the exhaust valve from being held open after an engine braking event, ensuring timely closure and preventing engine damage or operational issues.
Implementation Method 1
a lost-motion spring engaged against the lost-motion plunger and a top surface
Implementation Method 2
a return spring engaged against the outer housing and the intermediate plunger
Implementation Method 3
a valve assembly positioned within the lost-motion plunger and separating the LMHLA into an upper chamber and a lower chamber
Data Source
AI summary
A valve train arrangement is disclosed. The arrangement includes at least one exhaust valve and a support arranged adjacent to the at least one exhaust valve 4 and configured to engage a lobe defined on a camshaft. A lost-motion hydraulic lash adjuster (LMHLA) is positioned within the support, and the LMHLA is configured to adjust lash between the support and the at least one exhaust valve. An engine brake system is configured to engage the at least one exhaust valve, such that: (i) upon activation of the engine brake system, the engine brake system engages the at least one exhaust valve to open the at least one exhaust valve; and (ii) upon deactivation of the engine brake system, the engine brake system disengages the at least one exhaust valve such that the at least one exhaust valve is closed.