Switchable Rocker Arm Stop Pin Pivot Limit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rocker arms for internal combustion engines face challenges with costly and complex travel limiters that can disassemble, making it difficult to ensure proper orientation and assembly, leading to inefficiencies in valve lift management.
Innovation Solution
A rocker arm design featuring a stop pin and stop aperture system that limits the pivot range of the inner arm relative to the outer arm, using a latching mechanism and lost motion spring, with the stop pin fixed to the inner arm and received in a bore for interference fit, preventing disassembly and ensuring proper alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex travel limiter is used to limit inner arm pivot range, then the pivot range can be limited, but the device complexity and cost increase
Solution Approach 1:
The travel limiter is segmented into separate functional elements: the stop surface is integrated into the outer arm while the stop pin is a separate component on the inner arm. This segmentation allows each component to be simpler while collectively achieving the travel limitation function.
Solution Approach 2:
The stop pin is extracted as a separate, simple component from the outer arm structure. By taking out the limiting function and implementing it through a separate pin that engages with a bore in the outer arm, the complexity is reduced compared to an integrated travel limiter.
2Reliability
If a complex travel limiter is used to limit inner arm pivot range, then the pivot range can be limited, but the manufacturing cost increases
Solution Approach 1:
By segmenting the travel limitation into a stop surface in the outer arm and a separate stop pin, each component can be manufactured independently using simpler, more cost-effective processes rather than requiring a complex integrated travel limiter.
Solution Approach 2:
The stop pin is designed as a simple, inexpensive component that can be easily manufactured and replaced if necessary. This approach uses a low-cost element to achieve the travel limitation function that would otherwise require an expensive complex mechanism.
3Reliability
If existing travel limiters are used, then pivot range can be limited, but the lost motion spring may disassemble
Solution Approach 1:
The stop pin and stop surface are positioned to prevent the inner arm from pivoting beyond a predetermined position, thereby preliminarily preventing the lost motion spring from disassembling before it can occur. This proactive limitation ensures the spring remains constrained within safe operational limits.
4Reliability
If existing travel limiters are used, then pivot range can be limited, but proper orientation and assembly become difficult to ensure
Solution Approach 1:
The stop pin and stop surface are positioned asymmetrically to provide a unique engagement geometry that naturally guides proper assembly. The asymmetric design ensures that the inner arm can only be assembled in the correct orientation, as any other orientation would prevent proper engagement of the stop pin with the stop surface.
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 provides a cost-effective and simplified method to limit inner arm pivot range, preventing disassembly of the lost motion spring and ensuring proper orientation, facilitating easier assembly and reducing manufacturing complexity.
Implementation Method 1
a lost motion spring which biases the inner arm to pivot relative to the outer arm in a second direction which is opposite from the first direction
Implementation Method 2
a stop pin which limits the extent to which the inner arm pivots relative to the outer arm in the second direction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A rocker arm (10) includes an outer arm (14) defining a stop aperture (38) with a stop surface (38a); an inner arm (12) which selectively pivots relative to the outer arm (14); a latching mechanism (36) which switches the rocker arm (10) between a coupled state in which the inner arm (12) is prevented from pivoting relative to the outer arm (14) in a first direction and a decoupled state in which the inner arm (12) pivots relative to the outer arm (14); a lost motion spring (30) which biases the inner arm (12) to pivot relative to the outer arm (14) in a second direction which is opposite from the first direction; and a stop pin (40,40') fixed to the inner arm (12) and extending into the stop aperture (38) such that the stop pin (40,40') is circumferentially surrounded by the stop surface (38a) and such that the stop pin (40,40') within the stop aperture (38) limits the extent to which the inner arm (12) pivots relative to the outer arm (14).