Segmented Pulley Assembly for Smooth Ratio Shifts Under Load
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Solution Overview
Problem
Clutchless multi-ratio transmissions face challenges in functioning effectively at high speeds or under significant loads due to issues like ratcheting, slippage, and tensioning, which limit their commercial viability and reliability.
Innovation Solution
A pulley assembly with transition segments that are independently movable between engaged and disengaged regions, allowing for smooth transition of an endless member between pulleys using an actuator system driven by electromotive force, enabling continuous operation and adjustment of gear ratios while under load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If clutchless multi-ratio transmissions operate under significant loads, then power transmission capability is improved, but mechanical reliability deteriorates due to ratcheting, slippage, and tensioning problems
Solution Approach 1:
The pulley system is divided into multiple independently controllable pulley segments that can be selectively engaged or disengaged. This segmentation allows the transmission to maintain continuous power flow while distributing mechanical stresses across multiple segments, preventing ratcheting and slippage that occur in traditional single-unit clutchless transmissions.
Solution Approach 2:
The pulley segments are designed to be dynamically reconfigurable, allowing the system to adapt its engagement state based on load conditions. This dynamic adjustment capability enables the transmission to maintain optimal mechanical engagement under varying loads, eliminating the ratcheting and tensioning problems that plague static clutchless transmissions.
2Adaptability or versatility
If gear shifts are performed in clutchless transmissions, then ratio change capability is improved, but operational smoothness deteriorates due to intermittent forces and disruptions
Solution Approach 1:
The system prepares for gear shifts by pre-positioning pulley segments in their target engagement states before the actual shift occurs. This preliminary preparation allows ratio changes to happen smoothly without sudden force disruptions, as the mechanical path is already established before power transfer begins.
Solution Approach 2:
The pulley segments are designed to maintain continuous engagement with the belt throughout the gear shift process. By ensuring that at least one segment remains engaged at all times during ratio changes, the system eliminates interruptions and intermittent forces, providing smooth operational transitions while maintaining full power transmission.
3Ease of operation
If transition segments are added to enable smooth gear shifts, then operational smoothness is improved, but device complexity increases
Solution Approach 1:
Each pulley segment is designed as a universal component that can function both as a power-transmitting element and as a transition element during gear shifts. This multi-functionality reduces the need for specialized transition components, thereby limiting the increase in device complexity while still achieving smooth operational transitions.
Solution Approach 2:
The pulley segments are arranged in a nested or concentric configuration where multiple segments share the same radial space. This nesting approach allows the system to incorporate multiple functional segments without proportionally increasing the overall device footprint or complexity, as the segments are space-efficiently organized around the central axis.
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 enhances the reliability and efficiency of transmissions by reducing intermittent forces during gear shifts and maintaining continuous operation, even under load, thereby improving the commercial viability of synchronized segmentally interchanging pulley transmission systems.
Implementation Method 1
an actuator system driven by electromotive force, enabling continuous operation and adjustment of gear ratios
Data Source
AI summary
A pulley assembly (120) for engaging an endless member (118) includes a first pulley (124), a second pulley (126) and at least one transition segment set (128, 130) comprising one or more transition segments (152, 162a, 162b) that are independently movable between an engaged region and a disengaged region to transition the endless member (118) between the first pulley (124) and the second pulley (126). An actuator system (122) includes a support structure (220), an actuator subassembly (222, 226) secured to the support structure (220) and a stator (224, 228). The actuator subassembly (222, 226) includes a follower (250) and a sled (248), which is movable in a circumferential direction between an advanced position and a retreated position, in response to an electromotive force generated on the sled (248) by the stator (224, 228). The follower engages the cam surface (262) of the sled (248) to move in an axial direction between an extended position and a retracted position as the sled (248) moves between the advanced and retreated positions.