Toroidal CVT Disc and Bearing Layout for Fretting Wear Control
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Solution Overview
Problem
In toroidal continuously variable transmissions, minute elastic deformation of discs due to rotational pressure leads to minute vibration and fretting wear between disc surfaces and adjacent bearings, causing reciprocating sliding and wear.
Innovation Solution
The design incorporates a cylindrical portion projecting from the disc main body between the bearing and rotating shaft, which reduces elastic deformation and minimizes contact with the disc's end surface, thereby reducing reciprocating sliding and fretting wear by integrating the cylindrical portion, inner ring, and gear through press-fitting, thus canceling loads and suppressing vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the disc is pressed by the loading cam press to increase transmission torque, then adequate contact pressure between discs and power roller is achieved, but minute elastic deformation of the disc occurs causing fretting wear
Solution Approach 1:
The disc is segmented into two functional parts: the disc main body that contacts the power roller and transmits torque, and the cylindrical portion that serves as a bearing support. This segmentation allows the disc main body to undergo elastic deformation for torque transmission while the cylindrical portion remains relatively stable and positioned far from the deformation zone, preventing fretting wear at the bearing interface.
Solution Approach 2:
The cylindrical portion acts as an intermediary element between the disc main body and the bearing. It transmits the rotational force from the disc to the bearing while isolating the bearing from the elastic deformation of the disc main body. The cylindrical portion's end surface is positioned far from the concave surface, creating a buffer zone that prevents deformation-induced fretting wear.
2Object-affected harmful factors
If the cylindrical portion is made longer to reduce deformation impact on bearing, then fretting wear is suppressed, but the transmission size increases in the rotation axis direction
Solution Approach 1:
The invention optimizes the length parameter of the cylindrical portion to achieve the minimum required length that positions the end surface far enough from the concave surface to suppress fretting wear, without unnecessarily increasing the overall transmission size. This parameter optimization balances wear protection with compact dimensions.
3Power
If the disc main body undergoes elastic deformation to transmit reaction force, then torque transmission is achieved, but minute vibration occurs causing reciprocating sliding
Solution Approach 1:
By segmenting the disc into the disc main body and cylindrical portion, the invention allows the disc main body to undergo necessary elastic deformation for torque transmission while the cylindrical portion serves as a stable support that minimizes vibration transmission to the bearing, reducing reciprocating sliding.
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 effectively suppresses fretting wear on the disc's back end surface and reduces minute reciprocating sliding, enhancing the transmission's durability and reducing vibration.
Implementation Method 1
when the disc rotates while being pressed by the press in a direction along the rotation axis, the disc repeats minute elastic deformation
Implementation Method 2
a loading cam press (axial force generator) including: a cam plate that rotates coaxially with the discs; and a roller group including rollers that are sandwiched between the disc and the cam plate
Data Source
AI summary
A toroidal continuously variable transmission includes a rotating shaft, a pair of discs, at least one power roller, and at least one bearing arranged between the rotating shaft and a casing. At least one of the pair of discs includes: a disc main body including a concave surface opposed to the power roller; and a cylindrical portion projecting from the disc main body along the rotation axis toward an opposite side of the power roller. The cylindrical portion is inserted between the bearing and the rotating shaft.