Hydraulic Lash Adjuster Radial Recirculation Openings
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Solution Overview
Problem
Hydraulic lash adjusters in internal combustion engines face fluid depletion during engine startup or shutdown, leading to increased wear and potential damage due to leakage, and existing solutions like oil recirculation grooves compromise structural strength.
Innovation Solution
A hollow piston with a band of radial recirculation openings that recirculates leaked hydraulic fluid from the high pressure volume back to the fluid reservoir, maintaining fluid supply and reducing wear without compromising structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oil recirculation groove is formed on the exterior of the plunger, then hydraulic fluid can be recirculated to prevent depletion during engine startup, but the structural strength of the plunger is reduced due to the reduced cross section at the groove
Solution Approach 1:
The patent transitions from a circumferential groove (one-dimensional solution) to radial recirculation openings (three-dimensional solution). The radial openings extend through the thickness of the piston wall, creating recirculation paths in the radial dimension while preserving the piston's circumferential cross-section and structural integrity.
Solution Approach 2:
The patent creates a porous-like structure by providing multiple radial recirculation openings distributed across the piston wall thickness. This allows hydraulic fluid to recirculate through the piston wall in a distributed manner similar to porous flow, while maintaining sufficient material between openings to preserve structural strength.
2Ease of operation
If small quantities of hydraulic fluid are permitted to enter or escape from the high pressure volume during operation, then the position of the piston can be adjusted to minimize lash, but the hydraulic fluid may be depleted during engine startup or shutdown before sufficient supply is provided
Solution Approach 1:
The patent ensures continuous recirculation of hydraulic fluid through the radial openings, creating a closed-loop system where fluid that leaks from the high pressure volume continuously returns to the reservoir. This continuous action prevents fluid depletion during startup/shutdown operations while maintaining the piston adjustment capability during normal operation.
Solution Approach 2:
The radial recirculation openings create a feedback mechanism where leaked hydraulic fluid is automatically returned to the reservoir. This feedback loop ensures that fluid loss during piston adjustment is compensated by recirculation, maintaining sufficient fluid volume in the system during all operational states including startup and shutdown.
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
Effectively reduces hydraulic fluid depletion during engine startup, minimizing wear and potential damage while maintaining structural strength by allowing continuous fluid recirculation without the need for a circumferential groove, thus ensuring efficient engine operation.
Implementation Method 1
recirculation openings are provided so as to define a recirculation path between the high pressure volume and the low pressure volume
Data Source
Figure 1
Figure 2~3
AI summary
A hydraulic lash adjuster (46) includes a body (60) defining an axial bore (62) and having an open end (64) and a closed end (66). A hollow piston (68) is telescopically received within the axial bore (62) and defines a fluid reservoir (70). The hollow piston (68) has a first end (72) disposed within the axial bore (62) and a second end (74) extending outwardly beyond the open end (64) of the body (60). A high pressure volume (80) is defined by the axial bore (62) and the first end (72) of the hollow piston (68). The hydraulic lash adjuster (46) also includes a valve mechanism (82) positioned through an opening (84) of the hollow piston (68) and including a valve member (86) having an open position defining a fluid path from the fluid reservoir (70) to the high pressure volume (80). The valve member (86) also has a closed position in which the fluid reservoir (70) is fluidly blocked from the high pressure volume (80) at the opening (84). The hollow piston (68) includes a band (118) of radial recirculation openings (120) defining recirculation paths from the high pressure volume (80) to the fluid reservoir (70) along an exterior (114) of the hollow piston (68). A diameter of each of the radial recirculation openings (120) is smaller than a width of the band (118).