Planetary Traction Drive Preload Spring for Tolerance Variation
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Solution Overview
Problem
Driven turbochargers with planetary traction drives face challenges in maintaining consistent torque transmission due to variations in manufacturing tolerances and part dimensions, leading to potential slipping at traction interfaces.
Innovation Solution
Incorporation of a preload spring mechanism between the ring gear and the sprung traction ring, coupled with an anti-rotation mechanism, to provide a consistent preload force on the planet rollers' slanted inner traction surfaces, ensuring proper torque transmission and accounting for manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manufacturing tolerances and part dimensions vary, then assembly becomes easier and cost decreases, but torque transmission consistency deteriorates and slipping occurs at traction interfaces
Solution Approach 1:
The preload spring mechanism changes the normal force parameter at the traction interface dynamically. By applying a preload force through the spring, the system compensates for variations in manufacturing dimensions, maintaining consistent torque transmission capability despite dimensional tolerances in the planet rollers and traction surfaces.
Solution Approach 2:
The preload spring acts as an intermediary element between the ring gear and the planet rollers. It mediates the contact force at the traction interface, ensuring that variations in manufacturing tolerances do not directly translate to slipping or inconsistent torque transmission. The spring absorbs dimensional variations while maintaining reliable force transmission.
2Reliability
If a preload spring mechanism is added to maintain consistent torque transmission, then torque transmission reliability improves, but device complexity increases
Solution Approach 1:
The preload spring mechanism serves multiple functions simultaneously: it applies preload force to prevent slipping, compensates for manufacturing tolerances, and maintains consistent contact pressure at the traction interface. This multi-functionality justifies the added complexity by delivering multiple reliability benefits from a single integrated mechanism.
Solution Approach 2:
The spring mechanism introduces a controllable force parameter that can be optimized during design. By carefully selecting spring characteristics (rate, preload force, installation position), the system achieves reliable torque transmission without requiring overly complex control systems or multiple active components.
3Adaptability or versatility
If the sprung traction ring is allowed to slide axially on the anti-rotation mechanism, then preload adjustment capability improves, but friction and wear increase
Solution Approach 1:
The sprung traction ring is designed with dynamic axial movement capability on the anti-rotation mechanism. This allows the ring to adjust its position to accommodate manufacturing tolerances and maintain optimal preload conditions during operation. The dynamic adjustment capability ensures adaptability while the movement is constrained to minimize unnecessary sliding and associated wear.
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 preload spring mechanism ensures reliable torque transfer by maintaining the necessary preload force across traction interfaces, minimizing slipping and accommodating manufacturing variations, thus enhancing the operational efficiency of the planetary traction drive.
Implementation Method 1
a preload spring located between the ring gear and the sprung traction ring that provides a preload force on the slanted inner roller traction surfaces of the plurality of planet rollers
Implementation Method 2
an anti-rotation mechanism that connects the sprung traction ring and the ring gear such that the sprung traction ring can slide axially on the anti-rotation mechanism wherein the anti-rotation mechanism transmits torque between the sprung traction ring and the ring gear
Data Source
AI summary
Disclosed is a spring for preload in a planetary traction drive designed for a driven turbocharger on an engine. The ring roller of the planetary traction drive has two parts with a spring between the two parts for generating a preload force on the ring roller assembly of the planetary traction drive. The spring provides a spreading force on the ring roller, and allows for setting a desired preload force on the traction surfaces of the traction drive during assembly and operation, even with variations in manufacturing of the different parts of the traction drive.