Toroidal CVT Cam Plate Support for Uniform Roller Contact Pressure
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Solution Overview
Problem
In toroidal continuously variable transmissions (CVTs) 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 precise manufacturing of the cam surface taper is necessary.
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 roller separation, and a preload spring biases the cam plate to ensure consistent contact pressure without transmitting bending stress, allowing for easier manufacturing and stable torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a loading cam type pressing device is used to maintain contact pressure between discs, then sufficient contact pressure is achieved, but the cam plate deflects and concentrates load on the radially inward roller, reducing its life
Solution Approach 1:
A support structure is introduced as an intermediary element between the cam plate and the housing. This support receives the reaction force from the roller unit and transfers it to the housing, preventing the cam plate from deflecting under load. The support acts as a mediator that eliminates the harmful deflection while maintaining the necessary contact pressure transmission path.
Solution Approach 2:
The support structure is designed beforehand to anticipate and counteract the deflection of the cam plate under load. By providing this pre-positioned support, the system prevents the concentration of load on the radially inward roller before damage can occur, thereby extending roller life without compromising the pressing function.
2Duration of action of moving object
If the cam surface is formed with a taper shape to prevent radial load concentration, then roller life is improved, but manufacturing precision requirements increase
Solution Approach 1:
The function of preventing load concentration is extracted from the cam surface geometry and transferred to a separate support structure. This allows the cam surface to be manufactured with simpler, more accurate geometry while the support structure handles the load distribution function, reducing the manufacturing precision requirements for the cam surface taper angle.
3Stability of the object's composition
If the cam plate is made highly stiff to prevent deflection, then contact pressure uniformity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The system is segmented into distinct functional components: the cam plate for generating the pressing motion, the support structure for preventing deflection, and the housing for providing reaction force paths. This segmentation allows each component to be optimized independently, reducing overall device complexity while maintaining contact pressure uniformity.
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 provides a toroidal CVT with improved roller life and stable torque transmission performance by ensuring uniform contact pressure and simplifying the manufacturing process, reducing the need for a highly stiff cam plate support structure.
Implementation Method 1
a preload spring which biases the cam plate toward the roller unit in a direction of the rotational axis line
Data Source
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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.