Hydraulic Lash Adjuster External Body Positioning
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Solution Overview
Problem
Conventional hydraulic lash adjusters (HLAs) occupy significant space in engine designs, limiting compactness due to their size and the requirement for minimum distance between moving parts and static components, and are constrained by maximum oil pressure limits.
Innovation Solution
A compact hydraulic lash adjuster design where the outer body is located entirely outside the rocker arm, with a plunger having a second end that slides within the outer body and a first end fixedly connected to the rocker arm, allowing for reduced size without compromising load capacity, and featuring a ball valve mechanism for fluid flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the HLA is positioned between two valve train components with the outer body extending into the rocker arm cavity, then the HLA can maintain sufficient load capacity and oil pressure, but the space consumed limits engine compactness and increases distance requirements from static components
Solution Approach 1:
The patent repositions the outer body from extending into the rocker arm cavity (internal positioning) to being located entirely outside the rocker arm (external positioning). This dimensional reconfiguration reduces the space consumed within the confined rocker arm cavity while maintaining the HLA's load capacity and oil pressure characteristics through proper external mounting arrangement.
2Volume of moving object
If the diameter of the plunger assembly is reduced to decrease HLA size, then the HLA occupies less space, but the maximum oil pressure exceeds specified limits
Solution Approach 1:
The patent changes the positioning parameter of the outer body from internal to external location, which alters the spatial relationships and allows for optimized plunger dimensions. This parameter change enables the use of larger plunger diameters that maintain oil pressure within specified limits while the external positioning compensates for the increased dimensions, achieving a balance between size and pressure constraints.
3Force
If the HLA is designed with larger dimensions to maintain load capacity, then the load bearing capability is sufficient, but the engine layout becomes less compact and requires greater clearance from static components
Solution Approach 1:
The patent moves the outer body to an external position on the rocker arm, which redistributes the spatial footprint of the HLA. This allows the plunger assembly to maintain sufficient diameter for load capacity while the external positioning reduces the radial profile extension into the engine's confined space, enabling closer proximity to static components like fuel injectors.
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 design achieves a more compact engine layout by reducing the radial profile of the HLA, enabling closer proximity to static components like fuel injectors while maintaining suitable load capacity and ensuring efficient operation by optimizing fluid flow and storage.
Implementation Method 1
a resulting oil pressure differential across the ball P8a moves it against the bias of the spring P8c, opening the aperture P7 and enabling oil to flow from the second oil chamber P6 into the first oil chamber P2
Implementation Method 2
The one way valve P8 comprises a ball P8a captured by a cage P8b and biased by a spring P8c to a position closing the aperture P8
Implementation Method 3
the incompressible oil in the first chamber P2 provides sufficient rigid support for the HLA P1 to open a valve when, for example, a rocker arm pivots under the control of a cam
Implementation Method 4
a spring P5 arranged to enlarge the first chamber P2 by pushing the plunger assembly P4 outwardly relative to the outer body P3 to extend the HLA P1 to take up slack in a valve train assembly
Implementation Method 5
The oil can escape the first chamber P2 only slowly, for example, via a small annular 'leak-down' gap P9 defined by closely spaced leak down surfaces of the outer body P3 and the plunger assembly P4. This oil leakage down the leak down surfaces from the first chamber P2 allows the HLP P1 to retract again.
Data Source
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AI summary
A hydraulic lash adjuster (HLA) and an arrangement for a valve train assembly comprising an HLA are presented. A valve train component comprises a first body that defines a first bore. The HLA comprises a second body that defines a second bore and a plunger. In use, a first end of the plunger is mounted within the first bore, and a second end of the plunger is mounted within the second bore for reciprocal sliding movement with respect to the second body. The second body and the plunger define a first chamber for containing a hydraulic fluid and the plunger defines a second chamber for supplying hydraulic fluid to the first chamber through a valve located between the first and second chambers in response to movement of the plunger increasing the volume of the first chamber. In use, all of the second body is located outside of the first body.