Spiral Cam CVT Geometry for Slippage-Free Ratio Variation
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Solution Overview
Problem
Continuously variable transmissions suffer from slippage issues due to friction losses, affecting their efficiency and usage characteristics.
Innovation Solution
The use of spiral-shaped cam disks with planar outer contours allows for a variable transmission ratio without slippage, utilizing a force-transmitting means like belts or toothed-gear transmissions, enabling efficient and slippage-free force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If balls are used as force-transmitting means in continuously variable planetary transmissions, then the transmission can achieve continuously variable adjustment of transmission ratio, but slippage occurs causing friction losses and reduced efficiency
Solution Approach 1:
The invention uses spherical cam disks with specifically curved outer contours instead of traditional balls. The spherical shape maintains point contact for continuous variability, while the controlled curvature of the outer contours prevents slippage by ensuring proper engagement geometry during rotation.
Solution Approach 2:
The invention changes the geometric parameters of the cam disks by defining specific outer contours with mathematical functions. These parameter changes in the contour geometry enable the cam disks to transmit force without slippage while maintaining continuous variability in transmission ratio.
2Device complexity
If circular cam disks are used, then the structure is simple, but the ratio of arc length and rotational angle remains constant preventing continuous variable adjustment
Solution Approach 1:
The invention introduces asymmetry in the cam disk design by using non-circular outer contours. The asymmetric geometry of the cam disks allows the ratio of arc length to rotational angle to vary, enabling continuous variable adjustment of transmission ratio while maintaining rotational motion.
Solution Approach 2:
The spherical shape of the cam disks is maintained for simplicity and rotational capability, but the outer contours are modified with specific curvatures. This combination preserves structural simplicity while enabling continuous variable adjustment through controlled geometric curvature.
3Adaptability or versatility
If non-planar outer contours are used on cam disks, then variable transmission ratio is achieved, but force transmission becomes less efficient due to belt slippage
Solution Approach 1:
The spherical cam disks with specifically controlled outer contour curvatures ensure that force-transmitting belts or chains maintain proper engagement. The curvature geometry prevents lateral deviation and slippage during force transmission, ensuring reliable power transfer.
Solution Approach 2:
The outer contours are designed with specific mathematical parameter definitions that control the geometry. These parameter changes in the contour design ensure that the cam disks can vary transmission ratio while maintaining stable force transmission without belt slippage.
Data Source
AI summary
A continuously variable transmission (1) having the cams (9, 10, 11, 12) that are not circular as usual, but have the form of a spiral. The outer contours (15, 16, 7, 18) of the two cams (9, 10, 11, 12) are each situated in a plane which is perpendicular to the direction of rotation of the respective cams (9, 10, 11, 12).