Variable-Speed Belt Drive With Radial Force Actuation
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Solution Overview
Problem
Existing belt drive systems with fixed pulley radii limit speed ratio variability, making them inefficient for applications requiring dynamic speed adjustments, such as matching fan speed with cooling demands.
Innovation Solution
A variable-speed belt drive assembly utilizing radial force to create friction between a poly-rib belt and pulley segments with radially movable pulley segments, actuated by a mechanism that adjusts pulley diameter to change speed ratios, eliminating the need for a belt tensioner and potentially reducing vibration harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed radius pulleys are used in a belt drive system, then the structure is simple and reliable, but the speed ratio cannot be adjusted dynamically
Solution Approach 1:
The pulley is divided into multiple segments that can move independently relative to each other. Each segment can be positioned at different radial distances from the rotation axis, allowing the effective pulley radius to be adjusted by changing the segment positions, thereby enabling variable speed ratio without requiring a completely different pulley structure
Solution Approach 2:
The pulley structure transitions from a static fixed-radius design to a dynamic variable-radius design. The pulley segments are made movable along the radial direction, allowing the pulley radius to be adjusted dynamically during operation to match changing speed requirements
2Adaptability or versatility
If axial force is used to pinch the belt in variable sheave drives, then speed ratio adjustment is achieved, but the belt must be physically pulled out from the sheave drive pair
Solution Approach 1:
Instead of using axial force to pinch the belt as in conventional variable sheave drives, this invention uses radial force to press the belt segments against the pulley rim. The belt segments extend radially outward and are pressed against the pulley by spring-loaded arms, inverting the conventional approach of applying force axially
3Power
If radial force is used to create friction between belt and pulley, then force transmission efficiency is improved, but additional mechanisms are needed to maintain belt contact
Solution Approach 1:
The spring-loaded arms automatically maintain contact with the belt segments through their inherent spring force. When the pulley rotates, the centrifugal force and spring force work together to keep the belt segments pressed against the pulley rim, eliminating the need for external actuators or complex control mechanisms to maintain belt contact
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
Enables efficient transmission of force as shaft torque with adjustable speed ratios, enhancing system efficiency and reducing the need for additional dampening mechanisms, suitable for various drive applications including fan drives.
Implementation Method 1
Each coil spring 30 is biased to urge one of the pulley segments 26 radially outwardly with respect to the hub 16
Implementation Method 2
This design relies on predominantly radial force to create the friction required between the drive belt and the pulley to be able to transmit force which is turned into shaft torque
Data Source
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AI summary
A variable-speed belt drive assembly (10) comprises a rotatable hub (16) and a plurality of pulley segments (26), wherein each pulley segment (26) has a curved outer surface (28) adapted to engage a drive belt. A plurality of slider devices (23) is provided, wherein each slider device (23) has an outer end attached to a corresponding one of the pulley segments (26), and wherein each slider device (23) has an inner end slidably received by the hub (16). Moreover, an actuator device (40) is provided for moving the pulley segments (26) inwardly and outwardly with respect to the hub (26).