Center Pivot Rocker Arm Latching for Cylinder Deactivation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing center pivot rocker arms lack the ability to efficiently switch between activated and deactivated configurations for variable valve actuation functions, particularly for cylinder deactivation operations.
Innovation Solution
The development of latched center pivot rocker arms that can transition between activated and deactivated states through a mechanical or hydraulic latch assembly, allowing for the transfer of different valve lift profiles, including a lost motion profile for cylinder deactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a center pivot rocker arm is designed for traditional valve actuation, then it can transfer valve lift profiles effectively, but it lacks the capability to switch between different valve actuation modes for cylinder deactivation
Solution Approach 1:
The rocker arm incorporates a movable deactivatable latch mechanism that can transition between engaged and disengaged states, enabling the system to dynamically switch between activated and deactivated configurations. This dynamic element allows the same rocker arm structure to perform multiple functions without requiring separate components for each mode.
Solution Approach 2:
The rocker arm is designed with a universal structure that can perform both traditional valve actuation and cylinder deactivation functions through the addition of the latch mechanism. The same cam arm and valve arm components serve dual purposes depending on the latch state, eliminating the need for separate rocker arms for different operating modes.
2Adaptability or versatility
If a latch assembly is added to enable mode switching, then versatility improves, but stress concentrations and potential failure points increase
Solution Approach 1:
The design incorporates a lost motion spring that acts as a cushioning element between the cam arm and valve arm. This spring absorbs stress shocks and prevents direct rigid contact when the latch is disengaged, reducing stress concentrations on the latch mechanism and preventing catastrophic failure from sudden load changes.
Solution Approach 2:
The lost motion spring serves as an intermediary element between the cam arm and valve arm, mediating the force transmission when the latch is disengaged. This intermediary component protects the latch mechanism from direct stress exposure while still allowing controlled motion transfer, thereby improving reliability without sacrificing versatility.
3Reliability
If the latch assembly is positioned to optimize stress distribution, then reliability improves, but the complexity of positioning and alignment increases
Solution Approach 1:
The latch assembly is merged with the existing rocker arm structure by positioning it at the interface between the cam arm and valve arm. This integration allows the latch to utilize the existing structural framework and force paths, optimizing stress distribution without requiring separate mounting structures or complex alignment mechanisms.
Solution Approach 2:
The latch assembly is positioned at a location where the force vectors from the cam arm and valve arm naturally intersect, creating an equipotential point for force distribution. This positioning ensures that stresses are evenly distributed across the latch components during both engaged and disengaged states, improving reliability without adding complex positioning systems.
Data Source
Figure 1A~1C
Figure 2A~4
Figure 5
AI summary
A rocker arm can comprise a cam arm, a valve arm, a lost motion spring, and a pair of deactivatable latches configured to impede travel of the cam arm with respect to the lost motion spring and configured to enable the cam arm to collapse the lost motion spring. The cam arm can comprise a cam interface, a spring pressing area, a cam arm body, and a pivot axle connection. The valve arm can comprise a valve arm body, a rocker shaft bore, a latch socket, and lost motion spring mount. A pivot axle can connect the valve arm body to the cam arm body. Alternatively, a latch socket in a valve arm neck comprises a latch assembly whereby a deactivatable latch is configured to impede motion of the cam arm and to collapse so the cam arm can collapse the lost motion spring.