CVT Pulley Angle Configuration for Torque and Efficiency
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Solution Overview
Problem
Existing continuously variable transmissions experience efficiency loss in the largest speed ratio when the belt angle is increased relative to the pulley angle to maximize transmissible torque, leading to increased friction losses and reduced overall efficiency.
Innovation Solution
The pulley angle of the input pulley is set smaller than the belt angle, and the pulley angle of the output pulley is set essentially equal to the belt angle, with the belt angle being larger than the input pulley angle, to minimize friction losses while maintaining high transmissible torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the belt angle is increased relative to the pulley angle to maximize transmissible torque, then the transmissible drive torque increases, but friction losses increase and overall efficiency decreases
Solution Approach 1:
The patent applies different belt angles to different pulleys (input pulley vs output pulley) based on their specific functional requirements. The input pulley uses a larger belt angle (24-26 degrees) to maximize torque transmission, while the output pulley uses a smaller belt angle (22-24 degrees) to minimize friction losses and improve efficiency. This localized optimization resolves the contradiction by allowing each pulley to have different quality characteristics suited to its role in the power transmission system.
2Power
If the belt angle is increased relative to the pulley angle, then the transmissible drive torque increases, but the overall transmission efficiency decreases
Solution Approach 1:
The patent implements local quality by differentiating the belt angles between input and output pulleys. The input pulley employs a larger belt angle (24-26 degrees) optimized for torque transmission, while the output pulley uses a smaller belt angle (22-24 degrees) optimized for efficiency. This spatial differentiation of parameters allows the system to achieve both high power transmission capability and high productivity simultaneously.
Solution Approach 2:
The patent introduces asymmetry in the belt angle configuration between the two pulleys. Instead of using identical belt angles throughout the system, it creates an asymmetric arrangement where the input pulley has a larger belt angle than the output pulley. This asymmetric design allows optimization of different functional aspects (torque transmission vs. efficiency) at different locations in the system, resolving the contradiction between power and productivity.
3Force
If the belt angle is set larger than the pulley angle, then torque transmission is improved, but friction contact increases causing efficiency loss
Solution Approach 1:
The patent applies local quality by setting different belt angles at different locations (input vs output pulleys) to balance force transmission and friction. At the input pulley where high torque transmission is critical, a larger belt angle (24-26 degrees) is used. At the output pulley where friction losses would directly impact efficiency, a smaller belt angle (22-24 degrees) is used. This localized parameter optimization resolves the contradiction between force transmission and harmful friction 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
This configuration reduces efficiency loss in the largest transmission ratio and improves overall efficiency by optimizing the pulley and belt angles, particularly by minimizing friction contact at the output pulley and maintaining high torque at the input pulley.
Implementation Method 1
The friction contact between the contact faces of the transverse members and the pulley discs allows a force to be transmitted there between, such that the drive belt can transfer a drive torque and a rotational movement from one pulley to the other.
Data Source
AI summary
A continuously variable transmission includes two pulleys (1, 2), each with two pulley discs (4, 5) that are mutually oriented at a pulley angle (Φp-i; Φp-o), and a drive belt (3) with an endless carrier (31) and with a number of transverse members (32) that each arrive in contact with the pulley discs (4, 5) via contact faces thereof that are mutually oriented at a belt angle (Φb). The pulley angle (Φp-i) of one (1) of the transmission pulleys (1, 2) is set smaller than the pulley angle (Φp-o) of the other one (2) of the transmission pulleys (1, 2) and the belt angle (Φb) is set essentially equal to the larger pulley angle (Φp-o) of the other one pulley (2). This transmission is capable of transmitting a particularly high driving power with a particularly high efficiency.