Intersecting-Axes Gear Chamfer Geometry for Better Tooth Lubrication
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Solution Overview
Problem
Hypoid gears face a decrease in transmission efficiency due to insufficient lubricant supply at the tooth face interface, especially as transmission torque increases, leading to high friction coefficients and reduced film thickness in mixed and boundary lubrication regimes.
Innovation Solution
The intersecting-axes type gear mechanism incorporates R-chamfered portions on the ring gear where radially inner end faces and drive-side tooth faces meet, extending over the entire length, forming curved surfaces to facilitate continuous lubricant supply to the tooth face interface, preventing divergent flow and ensuring sufficient lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If C-chamfered portions are formed on both drive side and coast side tooth faces, then stress concentration at corners is avoided, but lubricant supply to tooth face interface becomes insufficient
Solution Approach 1:
The patent applies different chamfer configurations to different locations: R-chamfered portions are formed only on drive-side tooth faces where lubricant supply is critical, while coast-side tooth faces maintain conventional C-chamfered portions. This local differentiation optimizes both stress resistance and lubrication based on the specific functional requirements of each tooth face.
Solution Approach 2:
The patent replaces the conventional C-chamfered portions (flat angled surfaces) with R-chamfered portions having curved surfaces on drive-side tooth faces. This curvature facilitates lubricant flow along the tooth face by eliminating sharp corners that cause flow divergence, thereby improving lubricant supply to the tooth face interface while maintaining stress resistance.
2Power
If transmission torque increases, then power transmission capability is improved, but friction coefficient increases and film thickness decreases
Solution Approach 1:
The R-chamfered portions are pre-formed on the drive-side tooth faces to ensure optimal lubricant flow paths are established before high-torque operation begins. This preliminary geometric configuration ensures that under high transmission torque conditions, lubricant can continuously reach the tooth face interface, preventing transition to mixed or boundary lubrication regimes.
Solution Approach 2:
The patent changes the geometric parameters of the tooth face by replacing C-chamfered portions with R-chamfered portions having different curvature radii. This parameter change optimizes the lubricant flow characteristics, allowing sufficient film thickness to be maintained even under high transmission torque conditions where friction coefficients would otherwise increase.
3Productivity
If mesh point moves in tooth trace direction, then sliding of tooth faces occurs, but lubricant supply at interface becomes insufficient
Solution Approach 1:
The R-chamfered portions with curved surfaces are specifically designed to accommodate the sliding motion of the mesh point in the tooth trace direction. The curvature radius is optimized to maintain continuous contact with the lubricant film, preventing lubricant supply insufficiency even during the sliding phase of tooth face engagement.
Solution Approach 2:
The patent designs the R-chamfered portions to dynamically adapt to the changing contact conditions as the mesh point moves along the tooth trace. The curved geometry allows the chamfered portion to maintain effective lubricant supply throughout the entire sliding motion, ensuring continuous lubrication despite the dynamic nature of the mesh point movement.
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 enhances transmission efficiency by maintaining a sufficient lubricant film thickness, reducing friction, and improving lubricant distribution, especially under high-load and high-rotation conditions, making it suitable for modern vehicles.
Implementation Method 1
hypoid gears have a characteristic in which the mesh point of the gears moves in the tooth trace direction (typically called 'sliding of tooth faces')... decrease in transmission efficiency due to insufficient lubricant supply at the tooth face interface... maintaining a sufficient lubricant film thickness, reducing friction
Data Source
AI summary
An intersecting-axes gear type mechanism includes two gears configured to rotate in mesh with each other. Respective axes of rotation of the two gears being disposed in an intersecting-axes manner, and at least one of the gears has teeth each of which includes a tooth trace extending substantially in a radial direction and a radially inner end face. A chamfered portion is formed on a meeting portion where the radially inner end face and a tooth face of the each of the teeth meet, so as to extend over an overall length of the meeting portion. At least an entirety of an area where the chamfered portion and the radially inner end face meet and an entirety of an area where the chamfered portion and the tooth face meet are each composed of a curved surface in overall length.