Toroidal CVT Loading Cam Support for Uniform Roller Pressure
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Solution Overview
Problem
In toroidal continuously variable transmissions (CVT) with a loading cam type pressing device, the contact pressure between the cam plate and rollers is uneven, leading to reduced roller life and torque transmission performance, and requires precise manufacturing of the cam surface taper angle.
Innovation Solution
A toroidal CVT configuration with a cam plate support that receives the reaction force from the roller unit, maintaining uniform contact pressure and preventing local abrasion, allowing for easy manufacturing and stable torque transmission, and optionally including a preload spring to bias the cam plate and suppress tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cam plate is deflected and warped back by a reaction force from the roller while high torque is generated, then the cam plate is concentratively pressed against the roller located radially inward, but the life of this roller is reduced and torque transmission performance is degraded
Solution Approach 1:
A reaction force receiving portion is provided on the cam plate to receive the reaction force from the roller. This intermediary structure distributes the reaction force away from the concentrated contact point, preventing the cam plate from warping back and being concentratively pressed against a single roller, thereby reducing local abrasion and extending roller life
2Reliability
If the cam surface of the cam plate or disc is formed to have a taper shape, then a situation in which the roller located radially inward bears more load all the time is prevented, but it is necessary to precisely manage a taper angle of the cam surface when manufactured
Solution Approach 1:
The taper shape function is extracted from the cam surface and transferred to the reaction force receiving portion of the cam plate. By providing a tapered reaction force receiving portion, the load distribution function is achieved without requiring precise taper angle management on the cam surfaces of the cam plate or disc, thereby reducing manufacturing precision requirements
3Reliability
If a stiff cam plate support structure is used to prevent deflection, then contact pressure uniformity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
A reaction force receiving portion is provided on the cam plate itself to receive the reaction force from the roller. This intermediary structure on the cam plate directly addresses the deflection issue without requiring a complex external support structure, thereby maintaining contact pressure uniformity while reducing device complexity
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 ensures a long-lasting and stable torque transmission performance with uniform contact pressure, simplifying the manufacturing process and reducing the need for a highly stiff cam plate support structure, while maintaining weight reduction.
Implementation Method 1
the cam plate support properly receives a reaction force from the roller unit, and the deflection (flexure) of the cam plate is suppressed
Implementation Method 2
optionally including a preload spring to bias the cam plate and suppress tilting
Data Source
AI summary
A toroidal continuously variable transmission includes a first disc and a second disc disposed so that the first disc and the second disc are rotatable around a common rotational axis line, the first disc and the second disc facing each other; a power roller which is tiltably disposed between the first disc and the second disc; a pressing device of a loading cam type, the pressing device including a cam plate which is rotatable around the rotational axis line, and a roller unit including at least one roller sandwiched between a cam surface of the second disc and a cam surface of the cam plate; and a cam plate support supporting a back surface of the cam plate, the back surface being opposite to the cam surface of the cam plate, at a radial position conforming to a radial position of at least a portion of the roller unit.