Rocker Arm Latch Pin Alignment for Full-Lift Switching
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Solution Overview
Problem
Existing rocker arm assemblies face challenges in achieving precise alignment for selective activation and deactivation due to variations between mating parts, making it difficult to switch between full lift and no lift modes efficiently.
Innovation Solution
A rocker arm assembly with a latch pin assembly featuring a frustoconical-shaped latch pin and bores, along with a ramp or step configuration, allows for precise alignment and smooth transition between activated and deactivated states, reducing stress through increased surface contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional cylindrical latch pin and bores are used, then manufacturing is simpler, but precise alignment between mating parts is difficult to achieve due to variations
Solution Approach 1:
The latch pin and bore surfaces are given a frustoconical shape with a specific taper angle (0.4-3.0 degrees). This curved/tapered geometry self-aligns the latch pin with the bore during insertion, compensating for manufacturing variations and ensuring precise alignment between the cam side and valve side rocker arm portions without requiring extremely tight manufacturing tolerances.
2Manufacturing precision
If a tapered latch pin design is implemented, then alignment precision and surface contact area improve, but manufacturing complexity increases
Solution Approach 1:
The frustoconical taper provides a gradual transition that guides the latch pin into proper alignment with the bore. This geometric feature, while adding some complexity to the latch pin design, significantly improves alignment precision and distributes contact stresses over a larger surface area, enhancing both functionality and durability.
3Reliability
If precise alignment is achieved through tight tolerances, then switching reliability improves, but manufacturing cost and complexity increase
Solution Approach 1:
The tapered geometry of the latch pin and bore creates a self-aligning mechanism that ensures reliable engagement between the cam side and valve side rocker arm portions. This design achieves consistent switching reliability through geometric guidance rather than relying on tight manufacturing tolerances, thereby reducing manufacturing complexity and cost while maintaining high reliability.
4Strength
If a frustoconical-shaped latch pin is used, then stress is reduced through increased surface contact, but manufacturing precision requirements increase
Solution Approach 1:
The frustoconical shape with a moderate taper angle (0.4-3.0 degrees) provides an optimal balance between stress distribution and manufacturability. The tapered surfaces increase the contact area between the latch pin and bore, distributing stresses more evenly. The relatively gentle taper angle allows for practical manufacturing while still achieving the stress reduction benefits of increased surface contact.
Data Source
AI summary
A rocker arm assembly including a cam side rocker arm portion configured to selectively rotate about a pivot location. A latch pin assembly is provided for selectively latching and deactivating rotation of the cam side rocker arm portion relative to the valve side rocker arm portion about the pivot location. The latch pin assembly includes a latch pin moveable within a cam side bore and a valve side bore. The latch pin includes an outer peripheral surface having a first portion and a second portion. The first portion has a first diameter that is less than a second diameter of the second portion. At least one of the outer peripheral surface of the latch pin or inner surfaces of the cam side bore and the valve side bore is frustoconical-shaped.