Tripod CVJ Spherical Trunnion Friction Reduction
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Solution Overview
Problem
Conventional tripod type constant velocity joints experience significant frictional losses and shudder issues due to elliptical contact patterns and inadequate lubrication, leading to increased rolling resistance and potential quality control challenges during manufacturing and operation.
Innovation Solution
A tripod type constant velocity joint design featuring trunnions with partially spherical surfaces and cylindrical protrusions for improved lubrication and reduced contact area, along with a method of assembling the roller assembly that includes tapered surfaces and grooves to facilitate smooth rolling and grease penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional tripod type constant velocity joints use cylindrical trunnions with linear contact, then the structure is simple, but frictional losses increase and shudder problems occur due to elliptical contact patterns
Solution Approach 1:
The patent applies spheroidality by replacing the conventional cylindrical trunnion with a spherical trunnion that has a curved surface. This spherical geometry transforms the elliptical contact pattern into a more uniform circular contact pattern, reducing frictional losses and preventing shudder problems while maintaining structural simplicity. The curved surface of the spherical trunnion ensures consistent contact with the roller throughout the rotation cycle.
2Ease of manufacture
If conventional joints have inadequate lubrication access, then manufacturing is easier, but rolling resistance increases and durability decreases
Solution Approach 1:
The patent implements preliminary action by pre-configuring grease passages and lubrication channels that guide lubricant to the contact surfaces before operation begins. The spherical trunnion design includes integrated lubrication pathways that ensure proper grease distribution to the critical contact areas between the trunnion and roller, eliminating inadequate lubrication issues while maintaining manufacturing feasibility through integrated design.
3Force
If the contact area between trunnion and roller is large, then load capacity increases, but frictional spinning moments increase and shudder occurs
Solution Approach 1:
The patent applies parameter changes by modifying the contact geometry from an elliptical pattern to a circular pattern through the spherical trunnion design. This geometric parameter change optimizes the contact area distribution, maintaining sufficient load capacity while reducing the frictional spinning moments that cause shudder. The spherical geometry ensures uniform pressure distribution across the contact surface.
4Device complexity
If conventional joints lack proper lubrication channels, then device complexity is reduced, but initial lubrication is ineffective and rolling resistance increases
Solution Approach 1:
The patent implements universality by integrating multiple functions into the spherical trunnion component. The spherical trunnion simultaneously serves as the load-bearing element, the geometric solution for reducing frictional spinning moments, and the conduit for lubrication delivery. This multi-functional design ensures effective initial lubrication and reduced rolling resistance without significantly increasing overall 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 design significantly reduces frictional spinning moments, enhances lubrication, and minimizes shudder problems, resulting in stable rolling and lower axial forces, while ensuring effective initial lubrication and reduced manufacturing complexities.
Implementation Method 1
needle rollers engaged between the inner and outer rollers, and allowing the outer face of each outer roller to roll and move in the corresponding one of the guide grooves
Implementation Method 2
The cylindrical protrusion has a cross section of circular shape, or alternatively, of elliptical shape... allowing a lubricant to introduce in the gap for lubrication
Data Source
AI summary
A constant velocity joint for a drive system having a first rotating shaft and a second rotating shaft, wherein the constant velocity joint comprises: a hollow housing fixed to an end of the first rotating shaft, an inner face of the housing including a plurality of guide grooves extending in an axial direction of the housing, each groove having a pair of opposing side faces; and a tripod disposed at an end of the second rotating shaft, having a plurality of trunnions each positioned in a corresponding one of the guide grooves; and, an inner roller mounted to an outer end portion of each of the trunnions, an outer roller mounted on an outer face of each inner roller with needle rollers engaged between the inner and outer rollers for transmitting a load between the first and second rotating shafts to drive the driving system. Each trunnion includes an at least partially spherical surface in a circumferential area subjecting to the load, and a cylindrical protrusion disposed at the at least partially spherical surface and protruded to a distance from the at least partially spherical surface in a direction normal to the axis of the respective trunnion for surface-to-surface contact with an at least partially spherical inner face of the respective inner roller while defining a gap around the cylindrical protrusion and between the at least partially spherical surface of the respective trunnion and the at least partially spherical inner face of the respective inner roller.