Toroidal CVT Pressing Mechanism With Intermediate Sliding Member
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Solution Overview
Problem
The existing loading cam type pressing devices for toroidal continuously variable transmissions suffer from significant hysteresis between torque and pressing force due to frictional forces, leading to non-linear relationships and increased weight and size requirements to maintain necessary pressing forces.
Innovation Solution
The introduction of an intermediate sliding member with a smaller contact area, separate from the rollers, reduces frictional torque by altering the sliding contact geometry and material hardness, allowing for point contact and lower frictional forces, thereby minimizing hysteresis and achieving a more linear torque-to-pressing force relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct sliding contact is used between roller end surfaces and pocket surfaces, then the structure is simple, but frictional force is large causing significant hysteresis between torque and pressing force
Solution Approach 1:
An intermediate sliding member is introduced between the roller end surface and the pocket surface to serve as a mediator. This intermediate member has a smaller contact area than the roller end surface, which reduces the frictional force while still maintaining the sliding contact function. The intermediate sliding member transfers the load from the roller to the pocket through a reduced contact interface, thereby reducing hysteresis loss while keeping the overall structure relatively simple.
2Reliability
If larger contact area is used between rollers and pockets, then pressing force is reliably maintained, but frictional torque increases causing non-linear torque-to-pressing force relationship
Solution Approach 1:
The intermediate sliding member is designed with a localized small contact area at its tip that contacts the roller end surface. This local quality change means that only a small portion of the roller end surface is used for contact, rather than the entire surface. This localized contact reduces the frictional torque while still maintaining sufficient pressing force through the concentrated contact point, thereby improving the linearity of the torque-to-pressing force relationship.
3Strength
If steel rollers with steel pockets are used, then strength and durability are high, but frictional force is large due to similar material hardness
Solution Approach 1:
The system uses a composite material approach by introducing an intermediate sliding member made of a different material than the steel rollers and steel pockets. This intermediate member could be made of a material with different frictional properties, such as a polymer or coated material, which reduces the coefficient of friction compared to steel-on-steel contact. This composite material strategy maintains the structural strength of the steel components while reducing frictional force through the intermediate layer.
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 solution effectively reduces hysteresis between torque and pressing force, improving the linearity of the torque-to-pressing force relationship and reducing the weight and size of the pressing device, while maintaining the necessary pressing force, and allows for more precise processing of the rolling surfaces.
Implementation Method 1
a contact area of a sliding contact portion between the intermediate sliding member and the inside surface of the respective pockets or the end surface of the roller is smaller than a contact area of a sliding contact portion in a case where the intermediate sliding member is not provided and there is direct sliding contact between the end surface of the roller and the inside surface of the pocket
Implementation Method 2
hysteresis based on the frictional force is generated, so the relationship between the torque and the generated pressing force is no longer linear
Implementation Method 3
the rollers ride up on convex portions of the first cam surface and the second cam surface, whereby the space in the axial direction between the first cam surface and the second cam surface increases. As a result, the first disk on which the second cam surface is provided is pressed toward the second disk
Implementation Method 4
an oil film of traction oil is formed on traction portions that are portions of rolling contact between a side surface in the axial direction of the input-side disk and a peripheral surface of the respective power rollers and between a side surface in the axial direction of the output-side disk and the peripheral surface of the respective power rollers. Power is transmitted from the input-side disk to the output-side disk via this oil film
Data Source
AI summary
Provided is a pressing device for toroidal continuously variable transmission capable of reducing hysteresis that occurs between torque and pressing force. An intermediate sliding member 27 is provided in at least one location of a portion between an end surface on the outside in the radial direction of the retainer 13 of the roller 14 arranged on the outermost side in the radial direction and an inside surface of the pocket 25 on the outside in the radial direction, and a portion between an end surface on the outside in the radial direction of the retainer 13 of one roller 14 of adjoining rollers 14 in the radial direction and an end surface on the inside in the radial direction of the retainer 13 of another roller 14. As a result, the contact area of a sliding contact portion 32 is made smaller than in a case where an intermediate sliding member 27 is not provided.