Conical Jam Nut Geometry for Aluminum Cylinder Head Wear
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Solution Overview
Problem
In internal combustion engines with aluminum cylinder heads, the jam nut to head interface can slip and wear due to insufficient strength, leading to changes in valve lash and potential disintegration of the valve train structure, especially when using softer materials like aluminum without steel inserts or hydraulic lash adjustors.
Innovation Solution
A jam nut with a conical first surface, having an included angle determined as a function of the angle between the central axis of the stud and the force exerted by the rocker arm, is used to reduce wear by aligning the contact surfaces in a way that minimizes abrasive motion, allowing the jam nut to lock the ball stud firmly in place without the need for steel inserts or hydraulic lash adjustors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a jam nut is used to retain the ball stud in aluminum cylinder heads, then the device complexity is reduced and cost is lowered, but wear at the jam nut to head interface occurs leading to degradation of positional accuracy
Solution Approach 1:
The jam nut contact surface is designed with an asymmetric conical geometry where the contact surface normal is angled relative to the ball stud central axis. This asymmetric arrangement causes the contact force to be directed at an angle that reduces sliding motion between the jam nut and head interface, thereby reducing wear while maintaining the simple mechanical structure without steel inserts or hydraulic components
Solution Approach 2:
The invention changes the geometric parameter of the jam nut contact surface from a conventional flat or perpendicular orientation to a conical orientation with a specific included angle. This parameter change optimizes the force distribution and contact mechanics at the jam nut to head interface, reducing relative motion and wear while maintaining positional accuracy in aluminum cylinder heads
2Manufacturing precision
If steel inserts or hydraulic lash adjustors are used to prevent wear and maintain positional accuracy, then the positional accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for steel inserts or hydraulic lash adjustors by redesigning the jam nut geometry itself. The conical contact surface design inherently prevents wear and maintains positional accuracy through optimized force distribution, removing the need for additional complex components while maintaining the same level of precision
Solution Approach 2:
The invention replaces expensive, complex, or durable components (steel inserts, hydraulic lash adjustors) with a simpler, cheaper jam nut design that achieves comparable or superior performance through geometric optimization. The conical contact surface design extends the service life of the aluminum jam nut by reducing wear, making the cheaper component as reliable as more expensive alternatives
Data Source
AI summary
A valve actuating system determines a shape of its jam nut surface as a function of a resultant force on a ball stud exerted by a rocker arm on the ball stud during operation of the valve train. The contact surface of the jam nut, which is pressed against an associated surface of the head of an engine, is a conical surface with an included angle that is generally twice the magnitude of an angle between a resultant force on the ball stud and a central axis of the ball stud and its associated jam nut. Certain accommodations can be made in order to reduce the cost of the system that would occur if perfect mathematical preciseness with a most preferred embodiment of the present invention is employed.