Cardan Shaft Tooth Geometry Concave Bottom Curvature Wear Reduction
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Solution Overview
Problem
Cardan shafts used in hydraulic machines experience significant wear when transmitting large torques, particularly due to the convex bottom curvature design that lacks effective lubrication and leads to increased contact pressure.
Innovation Solution
The cardan shaft features a concave bottom curvature section between the positive and negative slopes, reducing contact pressure and improving tribological performance by allowing better lubrication, with a design that includes a reduced tooth thickness and increased distance between tooth bottoms in the axial middle, facilitating machining and reducing contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a convex bottom curvature design is used in the cardan shaft tooth geometry, then the structure is simpler and easier to manufacture, but wear increases significantly when transmitting large torques due to poor lubrication and high contact pressure
Solution Approach 1:
The patent applies local quality by modifying only the bottom curvature region of the tooth geometry while keeping other parts unchanged. The concave bottom curvature is introduced specifically in the contact area where lubrication is critical, creating a localized structural change that improves tribological performance without requiring complete redesign of the entire tooth geometry.
Solution Approach 2:
The patent directly applies the curvature principle by changing the bottom curve from convex to concave. This curvature modification creates a geometric form that naturally retains lubricant in the contact zone, improving the tribological conditions. The concave curvature acts as a lubricant reservoir, ensuring continuous lubrication during operation and reducing wear.
2Device complexity
If the bottom curve has a convex curvature between the positive and negative slopes, then the design is conventional and structurally simple, but the contact pressure is concentrated and lubrication is insufficient leading to increased wear
Solution Approach 1:
The patent applies parameter changes by inverting the curvature parameter of the bottom curve from positive (convex) to negative (concave). This single parameter change fundamentally alters the pressure distribution and lubrication characteristics in the contact zone, reducing contact pressure concentration and improving wear resistance without adding structural complexity.
3Reliability
If a concave bottom curvature is introduced to improve lubrication and reduce wear, then tribological performance improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the tooth geometry into distinct functional zones: the modified concave bottom curvature zone for tribological improvement, and the unchanged tooth profile zones for maintaining structural integrity. This segmentation allows the complex curvature to be manufactured as a localized feature rather than requiring complete redesign of the entire component.
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 concave bottom curvature design significantly reduces wear by enhancing lubrication and distributing contact pressure, resulting in improved tribological performance and reduced wear when transmitting large torques.
Implementation Method 1
The concave bottom curvature improves the tribological performance. It allows for a better lubrication in this area.
Implementation Method 2
The concave bottom curvature forms a kind of indentation of said bottom curve... reduces contact pressure in the axial middle of the tooth geometry
Data Source
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AI summary
A shaft (1) is shown comprising a shaft section (2) having an axis (3), a tooth geometry (4) at least at one end of said shaft section, said tooth geometry (4) having a first end (5) opposite said shaft section (2) and a second end (6) adjacent said shaft section (2), a number of teeth (7) distributed in circumferential direction around said axis (3), a bottom curve(9) between adjacent teeth (7), and an outer tooth curve (12), said bottom curve (9) having a positive slope from said first end (5) towards said shaft section (2) and a negative slope (14) at said second end (6). In such a shaft wear should be made as small as possible. To this end said bottom curve (9) comprises a section having a concave bottom curvature (15) between said positive slope and said negative slope.