Split Ring Planetary Drive Backlash Reduction
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Solution Overview
Problem
Existing variable cam timing systems in internal combustion engines face challenges in reducing backlash and noise-vibration-harshness (NVH) while maintaining precise control over the angular relationship between the camshaft and crankshaft, which affects engine efficiency and power delivery.
Innovation Solution
A split ring planetary drive system with a sun gear, planet gears, sprocket ring gear, and camshaft ring gear, where springs are used to bias the planet gears into meshing engagement with the ring gears, reducing backlash and NVH, and an electric phaser dynamically adjusts the rotational relationship using a brushless DC motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If springs are used to bias planet gears into meshing engagement, then backlash and NVH are reduced, but device complexity increases
Solution Approach 1:
A spring mechanism is introduced as an intermediary element between the planet gears and the ring gears. The spring applies continuous biasing force to maintain positive meshing engagement, eliminating backlash without requiring precision ground gears or complex control systems.
Solution Approach 2:
The system changes the mechanical engagement parameter from loose clearance (backlash) to continuous contact through spring biasing. This parameter change transforms the gear mesh from a clearance-based system to a positive engagement system, reducing NVH and backlash.
2Ease of manufacture
If less precisely ground gears are used, then manufacturing cost is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The requirement for high manufacturing precision is extracted from the gear teeth themselves and transferred to the spring mechanism. The springs compensate for dimensional variations in the gears, allowing the use of less precisely ground gears while maintaining reliable meshing engagement.
Solution Approach 2:
The spring mechanism provides beforehand cushioning by pre-loading the gear mesh. This pre-compression accommodates manufacturing tolerances and ensures continuous contact between gear teeth, compensating for imprecise gear grinding.
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 reduces backlash and NVH, allowing for precise control of the camshaft's phase relative to the crankshaft, improving engine efficiency and fuel efficiency by minimizing frictional losses and requiring lower driving torque, while using less expensive, less precisely ground gears.
Implementation Method 1
The spring biases the plurality of planet teeth into meshing engagement with the sprocket ring gear teeth and the camshaft ring gear teeth
Data Source
AI summary
A split ring planetary drive for an engine or use with an electric phaser. The split ring planetary drive includes a sun gear, a plurality of planet gears, a spring ring gear, a camshaft ring gear, and at least one spring. The sun gear has teeth and is driven to rotate around a sun axis. The plurality of planet gears are arranged around the sun gear with each planet gear comprised of planet teeth maintaining the planet gear in meshing engagement with the sun gear teeth. The sprocket ring gear has teeth and is driven by a crankshaft. The camshaft ring gear has teeth is rotatable with a camshaft. The teeth of the sprocket and camshaft ring gears maintain the ring gears in meshing engagement with each of the planet gears. The spring biases the planet gear teeth into meshing engagement with the sprocket and camshaft ring gear teeth.