Through Axle Switching Rocker Arm for Variable Valve Timing
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Solution Overview
Problem
Existing switching rocker arm systems for internal combustion engines face challenges in efficiently implementing variable valve timing and actuation strategies, particularly in maintaining rocker arm travel constraints to accommodate different cam profiles for early and late intake valve closing strategies, which limits their operational flexibility and efficiency.
Innovation Solution
A through axle switching rocker arm design featuring an outer and inner arm with a roller axle, where the inner bushing and roller axle diameters create a travel constraint, allowing for selective operation in early intake valve closing (EIVC) and late intake valve closing (LIVC) strategies by modifying cam profiles, and enabling concurrent use on four-valve engines to achieve multiple valve opening durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If switching rocker arm systems use multiple arms to engage different cam lobes for variable valve timing, then fuel economy and emissions are improved, but device complexity increases due to the need for multiple arms and switching mechanisms
Solution Approach 1:
The rocker arm is segmented into an outer arm and an inner arm that can pivot relative to each other about a pivot axle. The inner arm can be selectively positioned in different angular positions to engage different cam lobes (low-lift, high-lift, no-lift), allowing the system to achieve variable valve timing functionality while maintaining a more compact and integrated structure compared to completely separate rocker arm systems
Solution Approach 2:
The switching rocker arm system is designed to perform multiple functions through a single integrated mechanism. The same rocker arm assembly can engage different cam lobes to provide low-lift, high-lift, and no-lift valve actuation modes, enabling the system to optimize fuel economy and emissions across different operating conditions without requiring multiple separate rocker arm systems
2Manufacturing precision
If rocker arm travel constraint is imposed by inner bushing and roller axle diameter engagement, then manufacturing precision is improved, but adaptability decreases due to limited ability to accommodate different cam profiles
Solution Approach 1:
The system accommodates different cam profiles (early intake valve closing and late intake valve closing) by changing the operational parameters within the fixed rocker arm travel constraint. The cam profiles are specifically designed to work within the constrained travel defined by the inner bushing and roller axle diameter engagement, allowing the system to achieve different valve actuation strategies while maintaining manufacturing precision
Solution Approach 2:
The inner arm is designed to pivot dynamically relative to the outer arm about a pivot axle, allowing the system to adapt its configuration during operation. This dynamic capability enables the switching rocker arm to engage different cam lobes and achieve different valve lift profiles while maintaining the travel constraint imposed by the inner bushing and roller axle engagement
3Ease of manufacture
If through axle switching rocker arm design is used to reduce cost, then ease of manufacture is improved, but operational flexibility is reduced due to travel constraints
Solution Approach 1:
The rocker arm is divided into outer arm and inner arm segments that can pivot relative to each other, providing operational flexibility within the travel constraint. This segmentation allows the system to achieve multiple valve actuation modes (early intake valve closing, late intake valve closing) while maintaining a manufacturable design using standard through-axle construction methods
Solution Approach 2:
The dynamic pivoting capability of the inner arm relative to the outer arm provides operational flexibility despite the fixed travel constraint. This dynamic mechanism allows the system to adapt to different cam profiles and valve actuation strategies while maintaining the cost-effective through-axle construction approach
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 allows for cost-effective implementation of various valve actuation strategies within the rocker arm travel constraint, enhancing operational flexibility and efficiency by enabling the same rocker arm to perform multiple valve events and durations, thus improving engine performance and reducing emissions.
Implementation Method 1
The inner diameter of the inner bushing engages the outer diameter of the roller axle thereby inhibiting further pivoting of the inner arm relative to the outer arm defining a rocker arm travel constraint
Data Source
AI summary
A method of using a through axle switching rocker arm according to one example of the present disclosure is provided. The switching rocker arm comprises an outer and inner arm and a roller axle. The inner arm is pivotally coupled to the outer arm about a pivot axle and has an inner bushing that supports an inner roller. The inner bushing defines an inner diameter. The roller axle extends through the inner bushing and defines an outer diameter. The inner diameter of the inner bushing engages the outer diameter of the roller axle thereby inhibiting further pivoting of the inner arm relative to the outer arm defining a rocker arm travel constraint. The method includes designing first and second cam profiles based on the through axle switching rocker arm such that a difference in lift between the first and second cam profiles is held within the rocker arm travel constraint.