CVT Pulley Engineered Surface for Torque Transfer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing continuously variable transmissions (CVT) face challenges in achieving high torque capacity while maintaining adequate wear resistance and consistent frictional engagement between pulley surfaces, as micro-slippage and mixed boundary lubrication conditions lead to surface texture changes and inconsistent surface roughness.

Innovation Solution

The method involves creating an engineered surface on CVT pulleys using laser-etched microgrooves to achieve a precise and consistent actual roughness (Rpk) for enhanced friction and wear resistance, combined with physical vapor deposition (PVD) for improved wear characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mechanical methods (shot peening, grinding, polishing) are used to create surface roughness, then the average roughness (Ra) meets the overall requirement, but the peak to valley height is inconsistent throughout the surface area

Engineering Contradiction:

Improvesurface roughness consistencyVSAvoidfriction carrying capability consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent replaces mechanical surface treatment methods (shot peening, grinding, polishing) with a chemical etching process using ferric nitrate solution. This chemical method provides more uniform and consistent surface roughness across the entire pulley surface, eliminating the peak-to-valley height inconsistencies that occur with mechanical methods while maintaining the required average roughness for friction carrying capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Force

If high surface roughness is created to increase friction carrying capability, then slippage is minimized, but wear resistance may be compromised over time

Engineering Contradiction:

Improvefriction carrying capabilityVSAvoidwear resistance

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The patent optimizes the etching parameters including ferric nitrate concentration (0.5-5%), etching time (1-10 minutes), and temperature (20-80°C) to achieve the precise surface roughness range of 0.5-5.0 µm Ra. This controlled parameter approach creates sufficient surface roughness for high friction carrying capability while maintaining surface integrity and wear resistance by avoiding excessive roughness that would compromise durability.

Inventive Principle:

Principle #35Parameter changes

3Power

If the pulley surface is treated to have high average roughness (Ra) to maintain friction, then torque transfer is improved, but the surface texture depth reduces over time due to micro-slippage and lubrication conditions

Engineering Contradiction:

Improvetorque transfer capabilityVSAvoidsurface texture durability

Core Design Contradiction:

PowerVSDuration of action of stationary object

Solution Approach 1:

The patent applies a preliminary chemical etching treatment to the pulley surface before operation to establish an optimized surface roughness profile. This pre-treatment creates a consistent surface texture that is more resistant to degradation from micro-slippage and lubrication effects during operation, thereby maintaining torque transfer capability over the long term.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a composite surface structure through chemical etching that combines peaks and valleys in a controlled pattern. This composite surface morphology provides both the friction necessary for torque transfer and the durability to resist wear from operational conditions, effectively combining the benefits of high roughness with wear resistance.

Inventive Principle:

Principle #40Composite materials

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 approach ensures consistent surface roughness, reduces wear, and enhances torque transfer capability by improving oil retention and hydrodynamic film characteristics, meeting torque demands while maintaining long-term durability.

Implementation Method 1

employing a laser to etch the microgrooves

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

The micro-machined slots created in the surface by the femto-pulsed laser can enhance oil retention

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 3

combined with physical vapor deposition (PVD) for improved wear characteristics

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS9714700B2CVT pulley with engineered surface

Publication Date: 2017.07.25 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A pulley for a continuously variable transmission and a method of creating an engineered surface on an outer surface of a pulley of a continuously variable transmission, with the engineered surface engaging with a belt or chain of the continuously variable transmission. The method comprising the steps of: determining an actual engineered roughness (Rpk) on the outer surface needed to obtain a predetermined friction between the engineered surface and the belt or chain; and etching microgrooves in at least a portion of the outer surface to create the engineered surface by employing a laser to etch the microgrooves, the microgrooves being formed to a depth that produces the actual engineered roughness (Rpk).