Connecting Rod Eccentric Adjustment Spherical Joint
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Solution Overview
Problem
The existing connecting rods for internal combustion engines with adjustable compression ratios require complex and costly attachment mechanisms for eccentric rods to pistons, which are prone to manufacturing and assembly tolerances, leading to inefficiencies in force transmission and assembly processes.
Innovation Solution
The second ends of the eccentric rods are designed as spherical heads that engage in recesses on the pistons, with a retention element like a slotted retention ring providing a spherical-seat connection, allowing for freedom in all directions and compensating for tolerances, and enabling simple assembly without the need for welded or adhesive joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If complex attachment mechanisms (welded or adhesive joints) are used to connect eccentric rods to pistons, then the connection strength is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies spheroidality by designing the connection interface between the eccentric rod and piston as a spherical joint. The spherical head of the eccentric rod engages with a spherical recess in the piston, allowing for multi-directional movement and tolerance compensation. This curved surface connection replaces complex welded or adhesive joints, achieving both high connection strength and simplified device complexity.
2Productivity
If precise manufacturing and assembly tolerances are maintained for attachment mechanisms, then the force transmission efficiency is improved, but the manufacturing precision requirements and cost increase
Solution Approach 1:
The patent changes the geometric parameters of the connection interface by using a spherical joint design with specific radius ratios between the spherical head and recess. This parameter change allows the connection to accommodate a range of tolerances while maintaining effective force transmission, thereby reducing manufacturing precision requirements without sacrificing productivity.
Solution Approach 2:
The spherical geometry of the connection interface inherently compensates for manufacturing and assembly tolerances through its multi-directional movement capability. The curved surfaces allow for self-alignment and tolerance absorption, maintaining force transmission efficiency without requiring tight tolerance control.
3Reliability
If retained elements (retention rings) are added to the spherical-seat connection, then the reliability of the connection is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the retention function into a separate retention ring component that is distinct from the spherical head and piston. This retention ring can be independently manufactured and installed, providing reliable retention while allowing the main spherical connection components to remain simple in design. The segmented approach actually reduces overall device complexity by separating functions into standardized components.
Data Source
AI summary
A connecting rod has a big end bearing eye for attachment to a crankshaft, a small end bearing eye for attachment to a piston of a cylinder, and an eccentric adjusting device for adjusting an effective connecting rod length. The eccentric adjusting device has eccentric rods (15, 16) with first ends that engage on an eccentric lever of the eccentric adjusting device and second ends that engage on pistons (20, 21) guided in hydraulic chambers of the connecting rod. The second ends of the eccentric rods (15, 16) are spherical heads that engage in a corresponding recess (40) in the respective piston (20, 21), and the respective piston (20, 21) further accommodates a retention element (41), one segment of which rests on the spherical-headed end of the respective eccentric rods (15, 16).