Variable Length Connecting Rod With Single Piston Mechanism
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Solution Overview
Problem
Existing variable length connecting rods for internal combustion engines require two piston mechanisms to change the effective length, leading to increased weight and reduced strength due to the presence of cylinders, making it difficult to reduce the total weight while maintaining mechanical compression ratio adjustments.
Innovation Solution
A variable length connecting rod design featuring a single piston mechanism with a flow direction switching mechanism that uses hydraulic fluid to change the effective length by switching between two states, allowing the eccentric member to swivel and adjust the compression ratio without the need for additional piston mechanisms, thereby reducing weight and maintaining strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two piston mechanisms are provided to maintain the eccentric member at both first and second positions, then the compression ratio can be adjusted, but the total weight of the connecting rod increases and the connecting rod body strength decreases
Solution Approach 1:
The patent combines two separate piston mechanisms into a single piston mechanism. The first piston mechanism maintains the eccentric member at the first position, while the second piston mechanism is eliminated by using the flow direction switching mechanism to redirect hydraulic fluid flow. This merging reduces the total weight of the connecting rod while maintaining the ability to adjust compression ratio between two stages.
Solution Approach 2:
The flow direction switching mechanism acts as an intermediary device that controls the direction of hydraulic fluid flow. By switching the flow direction, it enables a single piston mechanism to achieve the functionality previously requiring two piston mechanisms, thereby reducing weight while maintaining adaptability for compression ratio adjustment.
2Adaptability or versatility
If two piston mechanisms are provided to maintain the eccentric member at both first and second positions, then the compression ratio can be adjusted, but the connecting rod body strength decreases due to additional cylinders
Solution Approach 1:
The patent merges two piston mechanisms into one, thereby reducing the number of cylinders formed in the connecting rod body. This reduction in cylinder quantity maintains the compression ratio adjustment capability while preserving the structural integrity and strength of the connecting rod body.
Solution Approach 2:
The flow direction switching mechanism serves as an intermediary that enables a single piston mechanism to control the eccentric member at both first and second positions. This eliminates the need for additional cylinders in the connecting rod body, thereby maintaining strength while achieving adaptability for compression ratio adjustment.
3Strength
If the thickness of the connecting rod body is increased to make up for the fall in strength, then the connecting rod body strength is restored, but the total weight of the connecting rod increases
Solution Approach 1:
The patent resolves this contradiction by merging two piston mechanisms into one, which eliminates the need to increase the thickness of the connecting rod body. The single piston mechanism with flow direction switching provides sufficient strength while maintaining lower weight, avoiding the need for compensatory thickening.
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
The design effectively reduces the total weight of the connecting rod while enabling efficient adjustment of the mechanical compression ratio by utilizing a single piston mechanism and hydraulic fluid management, enhancing engine performance and efficiency.
Implementation Method 1
the hydraulic cylinder is supplied with hydraulic fluid, the eccentric member swivels in one direction while if the hydraulic cylinder discharges hydraulic fluid, the eccentric member swivels in the other direction
Data Source
AI summary
A variable length connecting rod which can change the effective length comprises a connecting rod body, an eccentric member which is attached at the small end to the connecting rod body to be able to swivel and which changes the effective length of a variable length connecting rod when swiveled, one piston mechanism which has one hydraulic cylinder which is provided in the connecting rod body and one hydraulic piston which slides in the hydraulic cylinder, a direction switching mechanism which switches between supply and discharge of hydraulic fluid to the hydraulic cylinder, and a hydraulic fluid supply source which supplies the hydraulic cylinder with hydraulic fluid. The piston mechanism is configured so that the eccentric member swivels in one direction if hydraulic fluid is supplied to the hydraulic cylinder and so that the eccentric member swivels in the other direction if hydraulic fluid is discharged from the hydraulic cylinder.