Segmented Pulley Transmission for High-Speed Ratio Variation
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Solution Overview
Problem
Existing multi-ratio transmission systems face challenges in functioning effectively at high speeds and under significant loads due to issues like ratcheting, slippage, and tensioning, which limit their commercial viability and reliability.
Innovation Solution
A segmented pulley transmission system with a core pulley and interchangeable pulley segments, where key pulley segments enable simultaneous engagement of the endless drive member with pulley segments of different radii, allowing for seamless ratio variation without introducing slack or interference, and utilizing a synchronization system to coordinate pulley segment movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional multi-ratio transmission systems are used, then gear ratio variation is achieved, but ratcheting, slippage, and tensioning problems occur under load and at high speeds
Solution Approach 1:
The transmission system divides the pulley into multiple discrete segments that can be independently positioned. These segments are arranged in sets at different radii from the axis of rotation, allowing the belt to engage with specific segments to achieve different gear ratios. The segmentation enables precise control over power transmission paths, eliminating ratcheting and slippage by ensuring continuous engagement without gaps.
Solution Approach 2:
The system pre-positions multiple pulley segment sets at different radii before operation begins. During gear ratio changes, the belt transitions between pre-positioned segments rather than creating new engagement points under load. This preliminary arrangement of segments eliminates tensioning problems by maintaining continuous belt engagement throughout the transition process.
2Adaptability or versatility
If pulley segments are actuated during contact zone, then ratio variation is achieved, but power transmission is disrupted
Solution Approach 1:
The system performs pulley segment actuation in advance, before the belt enters the contact zone with the pulley. Actuators move segments into their final positions while the belt is still approaching, ensuring that by the time the belt engages, all segments are already in their correct positions. This eliminates power transmission disruption by avoiding mid-contact actuation.
Solution Approach 2:
The system uses an intermediary transition mechanism where the belt temporarily engages with multiple segments simultaneously during ratio changes. This intermediary state allows smooth transfer of power from one set of segments to another without abrupt disengagement or disruption, maintaining continuous power transmission throughout the transition.
3Adaptability or versatility
If pulley segments are moved into engaging position, then gear ratio range is expanded, but slack or interference is introduced in the endless member
Solution Approach 1:
The system applies different engagement characteristics to different segments based on their radial position. Outer segments are designed with engagement features optimized for their specific radius, ensuring that each segment set maintains proper belt tension and alignment. This local optimization prevents slack and interference by tailoring the engagement geometry to each specific gear ratio configuration.
Solution Approach 2:
The system changes geometric parameters of the pulley segments, specifically the radial distance from the axis, to achieve different gear ratios. By precisely controlling the radial position of each segment set and designing corresponding engagement features, the system expands the gear ratio range while maintaining proper belt tension and preventing slack or interference through parameter optimization.
Data Source
AI summary
A segmented pulley transmission [20] is provided. A pulley assembly [36] is rotationally mounted on an axle [32]. The pulley assembly [36] includes a core pulley [45] having a first set of mating features on a peripheral surface thereof. A pulley segment set comprises a number of pulley segments [48] slidably mounted in the pulley assembly and arranged in a ring concentric with the core pulley [45]. The pulley segments [48] are individually actuatable out of the pulley assembly into an engaging position and into the pulley assembly into a non-engaging position. The pulley segments [48] have a second set of mating features [52] on an peripheral surface matching the first set of mating features. An endless drive member [47] has corresponding mating features on an inside surface for engaging the first and second sets of mating features of the core pulley [45] and the pulley segments [48] in an engaging position. Contact between the endless drive member [47] and a core pulley defines a contact zone [CZ]. An actuator [80] actuates the pulley segments [48] between the engaging and non-engaging positions when the pulley segments [48] are outside of the contact zone [CZ]. One of the pulley segments [48] in the pulley segment set is a key pulley segment [48a] that is positioned relative to the care pulley [45] such that when the key pulley segment [48a] is actuated to the engaging position and rotated into the contact zone [CZ], the corresponding mating features of the endless drive member [47] engage the first set of mating features of the core pulley [45] and the second set of mating features [52] of the key pulley segment [48a] without the introduction of significant slack or tension.