Latch Pin Geometry for Valve Lifter Oil Flow
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Solution Overview
Problem
Existing hydraulic lash adjusters with latch pins in push rod engines face long response times and variations due to the latch pin 'nesting' in the latch pin groove, hindering oil flow and preventing the inner body from rotating, which is exacerbated by the geometry of the latch pin nose.
Innovation Solution
The latch pin is redesigned with a spherical crown shape, featuring stepped flats and beveled reliefs to facilitate improved oil flow and prevent the pin from entering the oil supply hole, allowing for quicker disengagement and valve deactivation by altering the pin's geometry to reduce nesting and enhance fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spherical radius is used on the latch pin nose, then the pin can engage with the groove, but it dives into the oil supply hole and blocks oil flow
Solution Approach 1:
The latch pin nose is designed with non-uniform geometry: a spherical radius on one side for engagement, but a beveled relief on the opposite side to prevent oil blockage. This local differentiation allows the pin to fulfill its latching function while maintaining proper oil flow through the supply hole.
Solution Approach 2:
The latch pin nose is segmented into distinct functional zones: an engagement surface with spherical radius for contacting the groove, a beveled relief zone for oil flow clearance, and a flat zone for lateral engagement. This segmentation allows each zone to perform its specific function without interfering with others.
2Reliability
If the latch pin geometry is similar to the groove geometry, then engagement is achieved, but the pin nests in the groove causing long response time
Solution Approach 1:
The latch pin geometry is made asymmetric relative to the groove: while the groove has a uniform circular cross-section, the pin nose features a spherical radius on one side, a beveled relief on another, and a flat surface on the third side. This asymmetry prevents the pin from nesting deeply in the groove, reducing response time for deactivation.
Solution Approach 2:
Different regions of the latch pin nose have different geometries optimized for specific functions: the spherical radius provides point contact for engagement, the beveled relief creates an oil flow channel and prevents nesting, and the flat surface provides lateral engagement. This local quality differentiation solves the nesting problem while maintaining reliable engagement.
3Loss of time
If the latch pin geometry is modified to improve oil flow, then response time improves, but manufacturing complexity increases
Solution Approach 1:
The latch pin geometry is modified by changing specific dimensional parameters: adding a beveled relief at a specific angle, defining a spherical radius of a specific size, and positioning a flat surface at a specific orientation. These parameter changes can be achieved through standard machining operations, balancing performance improvement with manufacturing feasibility.
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 improves the switch response time of the latch pin, ensuring efficient valve deactivation by preventing oil flow obstruction and allowing the inner body to rotate relative to the outer body, thus enhancing the engine's fuel efficiency and reducing pollutant emissions.
Implementation Method 1
improves the oil flow around the end of the latch pin by changing the geometric shape of the end of the latch pin
Data Source
AI summary
Shown is a latch pin for use in a valve lifter and a valve lifter including the same. The latch pin for selectively latching within a pin chamber provided in the valve lifter is configured as a whole as a cylindrical pin with one end in the shape of a spherical crown, wherein a stepped flat is formed on radially one side of said one end and is dimensioned to be received within the pin chamber to engage with an axial latching surface thereof. On the top side of said one end, a first relief is formed by beveling the spherical crown, and on the radially other side opposite to the stepped flat across said first relief, a second relief is formed by beveling the spherical crown, wherein the second relief radially adjoins the first relief and circumferentially adjoins a remaining pin face in the shape of the spherical crown.