CVT Clutch Flyweights With Selective Mass Placement Across RPMs
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Solution Overview
Problem
CVT clutch systems with naturally aspirated engines face challenges in achieving optimal torque output across RPM ranges, particularly with turbocharged engines, where lower torque at low RPMs and reduced force at high RPMs result in tradeoffs between startup performance and mid-to-high RPM range efficiency due to traditional flyweight mass tuning limitations.
Innovation Solution
The design of flyweights with a body, pivot, and couplers that allow selective addition of mass distal and proximal to the cam surface, enabling precise adjustment of center of mass to optimize torque distribution and engagement characteristics, using couplers to position weights in a way that reduces torque at low RPMs and increases it at higher RPMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the mass of flyweights is increased to improve high RPM torque output, then force at high RPM is improved, but startup acceleration and low RPM performance deteriorate
Solution Approach 1:
The flyweight mass is segmented into two distinct components: a base mass that is fixed and a variable mass that can be selectively added or removed. This segmentation allows independent optimization - the base mass provides necessary low RPM torque for startup, while the variable mass can be added to increase high RPM force output when needed, resolving the contradiction between startup performance and high RPM performance
Solution Approach 2:
The flyweight system transitions from a static mass configuration to a dynamic one where mass can be adjusted based on operating conditions. The adjustable mass mechanism enables the system to adapt its inertia characteristics - using lower mass for startup acceleration and higher mass for high RPM torque, thus resolving the performance tradeoff across different RPM ranges
2Speed
If the mass of flyweights is decreased to improve startup acceleration, then low RPM performance is improved, but force at high RPM deteriorates
Solution Approach 1:
By dividing the total flyweight mass into a permanent base component and an optional variable component, the system can maintain a lightweight base configuration for optimal startup acceleration while allowing addition of mass when high RPM force is required, eliminating the need to compromise between the two performance requirements
Solution Approach 2:
The adjustable mass mechanism serves multiple functions: it enables the flyweight system to perform optimally across different operating conditions (startup and high RPM operation), provides adaptability to various driving conditions, and allows a single flyweight design to replace multiple fixed-mass flyweights, thus resolving the performance contradiction through multi-functionality
3Adaptability or versatility
If traditional flyweight mass tuning is used for turbocharged engines, then engine-specific performance is improved, but tradeoffs between low RPM and high RPM performance occur
Solution Approach 1:
The segmentation of mass into adjustable components enables precise tuning for different engine types (naturally aspirated vs. turbocharged) without compromising overall performance balance. Each engine type can be optimized by selecting appropriate variable mass configurations while maintaining a balanced base mass that ensures acceptable performance across the entire RPM range
Solution Approach 2:
The system enables change in the mass parameter of the flyweight based on specific engine requirements and operating conditions. By adjusting the variable mass component, the system can be tuned for different engine characteristics while maintaining performance balance, eliminating the need to accept tradeoffs between low and high RPM performance for different engine types
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 solution allows for improved torque output and engagement efficiency across RPM ranges, enabling better acceleration and performance by fine-tuning the center of mass location of flyweights, facilitating easier tuning and adjustment for specific engine conditions.
Implementation Method 1
positioned below the reference line R2, all, or substantially all, of the mass of the at least one first weight 56 contributes to reduced torque T2 about the pivot 38 related to an acceleration of the flyweight 32 in its initial, unengaged position
Implementation Method 2
the centrifugal force (i.e., inertia) acting on the flyweights 22 may be sufficient to apply a force to the spider assembly 18 via the interface between the cam surface 26 and the rollers 28 to overcome the biasing force of the spring 20
Implementation Method 3
a spring 20 is positioned on the output shaft 14 to provide a biasing force on the movable sheave 16 away from the stationary sheave 12
Data Source
AI summary
A flyweight comprises a body. The body of the flyweight comprises a pivot, a cam surface, and a first coupler. The first coupler is configured to selectively couple at least one first weight to the body distal from the cam surface. A flyweight comprises a body having at least 20% of its mass positioned to contribute negative torque about a pivot related to an acceleration of a CVT clutch from an idling condition. A method of tuning a flyweight comprises attaching at least one first weight to a first coupler of a body of the flyweight distal from a cam surface of the body. A CVT clutch comprises at least one flyweight with a first coupler configured to selectively couple at least one first weight to a body of the flyweight distal from a cam surface.