Planetary VCT Phaser Assembly With Spring-Biased Backlash Control
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Solution Overview
Problem
Variable camshaft timing (VCT) phaser systems in internal combustion engines often experience backlash conditions due to demanding gear teeth tolerances, leading to noise, vibration, and harshness (NVH) issues.
Innovation Solution
Incorporating a planetary gear set with a clearance between planet gears and pins, and using springs to bias the gears into engagement, minimizing backlash and introducing damping to reduce NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If demanding gear teeth tolerances are used in the planetary gear set, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the clearance parameter from zero (tight tolerance) to a specific non-zero value (0.004 to 0.012 inches) between planet gears and pins. This parameter change allows standard manufacturing tolerances to be used while achieving the desired backlash minimization through the controlled clearance and spring biasing mechanism, thereby reducing device complexity and manufacturing cost.
2Object-generated harmful factors
If clearance is added between planet gears and pins, then backlash is reduced and damping is introduced, but manufacturing precision requirements worsen
Solution Approach 1:
The patent introduces a spring as an intermediary element between the planet gears and the carrier pins. This spring mediates the interaction by providing a biasing force that maintains optimal contact between gears while allowing controlled clearance. The spring absorbs variations and maintains consistent performance despite manufacturing tolerances, reducing the stringency of precision requirements.
3Reliability
If springs are used to bias planet gears into engagement, then reliability is improved by minimizing backlash, but device complexity increases
Solution Approach 1:
The spring component serves multiple functions simultaneously: it biases the planet gears into engagement to minimize backlash, provides damping to reduce NVH, and compensates for manufacturing tolerances. By making the spring multi-functional, the patent achieves improved reliability without proportionally increasing device complexity, as one component performs several critical functions.
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 solution effectively minimizes unwanted backlash and noise, vibration, and harshness by ensuring closer teeth-to-teeth meshing and introducing a damping effect within the gear set.
Implementation Method 1
The planetary gear set may further include one or more springs. The spring(s) urges the planet gears radially outboard and displace the planet gears radially outboard via the clearance. The planet gears are urged into engagement with the ring gears.
Implementation Method 2
Incorporating a planetary gear set with a clearance between planet gears and pins, and using springs to bias the gears into engagement, minimizing backlash and introducing damping to reduce NVH.
Data Source
AI summary
An engine variable camshaft timing (VCT) phaser assembly is equipped in an internal combustion engine (ICE) to adjust the rotation of the engine's camshaft relative to the engine's crankshaft. The adjustments advance and retard the opening and closing movements of the engine's intake and exhaust valves. An electric motor and a planetary gear set work together amid use of the VCT phaser assembly. The planetary gear set can include two or more ring gears, planet gears, and a sun gear. A backlash condition sometimes experienced in previous VCTs is minimized in the VCT phaser assembly by one or more springs that urge the planet gears into engagement with the ring gears.