Switchable Rocker Arm Coupling Assembly Load Reduction
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Solution Overview
Problem
Switchable valve train components in internal combustion engines face challenges in achieving quick switching times and minimizing wear, as the design attributes of rapid switching and high wear resistance are often in opposition, leading to increased contact pressures and wear due to shorter actuation strokes.
Innovation Solution
A switchable rocker arm with a hydraulically actuated coupling assembly located within the rocker arm to minimize loads and resultant wear, allowing for two discrete valve lift modes by positioning the coupling assembly to maximize the distance from the rocker arm pivot point, reducing shear loads and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the coupling assembly is positioned closer to the rocker arm pivot point, then the actuation stroke is shorter enabling faster switching times, but the contact pressure increases leading to greater wear
Solution Approach 1:
The patent positions the coupling assembly at the valve end of the rocker arm, which is the farthest point from the pivot point in the linear dimension. This maximizes the actuation stroke length, thereby reducing contact pressure and wear while still achieving acceptable switching times through optimized hydraulic actuation
2Object-affected harmful factors
If the coupling assembly is positioned farther from the rocker arm pivot point, then wear is reduced due to longer actuation stroke, but the switching time increases
Solution Approach 1:
The patent employs a hydraulic actuation system with a piston and fluid pressure to move the coupling assembly. This hydraulic mechanism enables rapid actuation of the coupling assembly despite its position at the valve end, achieving fast switching times without compromising the wear-reducing benefits of the extended actuation stroke
3Speed
If the coupling assembly uses a shorter actuation stroke, then switching speed is improved, but contact pressure increases causing greater wear
Solution Approach 1:
The patent maximizes the actuation stroke length by positioning the coupling assembly at the valve end of the rocker arm, which provides the longest possible linear distance from the pivot point. This extended stroke reduces contact pressure and wear while the hydraulic actuation system maintains fast switching speeds
4Object-affected harmful factors
If the coupling assembly is positioned to maximize distance from pivot point, then wear is minimized, but the device complexity increases
Solution Approach 1:
The coupling assembly positioned at the valve end serves multiple functions: it acts as the locking/unlocking mechanism, serves as a mounting point for the hydraulic actuator, and provides the optimal lever arm for minimizing contact pressure. This multi-functional positioning reduces the need for additional components and simplifies the overall design
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 solution enables faster switching times and reduced wear on the coupling assembly, enhancing the durability and performance of the switchable valve train component by distributing loads more evenly and reducing contact pressures.
Implementation Method 1
a hydraulic actuator 48 that uses hydraulic pressure to move a locking pin 34 between a locked position and an unlocked position
Implementation Method 2
a bias spring 40 that urges the locking pin 34 toward the locked position
Data Source
AI summary
A switchable rocker arm for valve deactivation is provided for a valve train of an internal combustion engine. The switchable rocker arm includes a valve side lever assembly, a cam side lever assembly, and a hydraulically actuated coupling assembly. The valve side lever assembly includes a first housing with a first rocker shaft bore. The cam side lever assembly includes a second housing with a first arm with a second rocker shaft bore and a second arm with a third rocker shaft bore. The first and second arms extend along opposed longitudinal sides of the cam side lever assembly such that the first, second and third rocker shaft bores are axially aligned. The coupling assembly is arranged at an end furthest away from a pivot axis for minimal loading and provides locking and unlocking of the switchable rocker arm to achieve full valve lift and no valve lift modes, respectively.