Split Ring Planetary Drive with Eccentric Pin for Backlash Control
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Solution Overview
Problem
Current electric phasers in variable cam timing systems face challenges with backlash noise and friction losses at low rotational speeds, which are costly to mitigate with precise gears and reduced carrier center distances, and inefficiencies persist due to fixed force biasing of planet gears.
Innovation Solution
A split ring planetary drive with a planet gear adjuster and load generator that biases planet gears at low speeds to take up backlash, using an eccentric pin and extension arm to reduce friction and noise, and as speed increases, inertia opposes the load generator to reduce force on the planet gears, allowing increased actuation speed and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fixed force biasing is used to take up backlash between planet gears and ring gears, then backlash noise is reduced at low speeds, but friction losses increase and actuation speed decreases
Solution Approach 1:
The patent applies dynamics by making the biasing force on planet gears variable rather than fixed. A spring mechanism provides adjustable preload force that can be modulated based on operating conditions. The spring allows the system to dynamically adapt the gear mesh force, providing sufficient preload to eliminate backlash noise at low speeds while reducing the force at higher speeds to minimize friction losses and improve actuation speed.
Solution Approach 2:
The patent changes the parameter of biasing force from a fixed value to a variable parameter that can be adjusted according to rotational speed and operating conditions. By using a spring-based preload mechanism, the force parameter becomes adaptable, allowing optimization of the balance between backlash elimination and friction reduction across different operating ranges.
2Object-affected harmful factors
If precise gears and reduced carrier center distances are used to mitigate backlash noise, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by preloading the planet gears against the ring gears using a spring mechanism before operation. This preliminary biasing force ensures that the gears remain in constant mesh contact, eliminating backlash without requiring extremely precise gear manufacturing or reduced center distances. The preload is applied in advance to compensate for any manufacturing tolerances.
Solution Approach 2:
The patent converts the potentially harmful effect of gear clearance (backlash) into a beneficial feature by using a spring-based preload system. Instead of trying to eliminate clearance through tighter tolerances, the system uses controlled elastic deformation of the spring to maintain optimal gear contact, transforming the clearance issue into a mechanism for adaptive force application.
3Reliability
If high biasing force is applied to planet gears to eliminate backlash, then gear mesh contact is improved, but actuation speed and efficiency decrease
Solution Approach 1:
The patent applies dynamics by implementing a speed-adaptive biasing force mechanism. The spring-based system automatically adjusts the preload force on planet gears based on the rotational speed and inertial forces present. At low speeds, higher preload ensures reliable gear mesh contact, while at high speeds, the reduced preload minimizes friction and allows faster actuation, thus adapting the reliability-productivity balance dynamically.
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 NVH issues at low speeds, decreases friction drag, and increases actuation speed by dynamically adjusting the planet gear position, providing a cost-effective and efficient solution for backlash reduction.
Implementation Method 1
A spring forces the planet gear adjuster to apply a force on the planet gear to take up the backlash between the planet gear and the ring gears
Implementation Method 2
As the rotational speed increases, the inertia of a mass forces the planet gear adjuster to move the planet gear to a position where the planet gear no longer takes up the backlash
Implementation Method 3
The planet gear adjuster includes an eccentric pin and an extension arm
Data Source
AI summary
A split ring planetary drive of an electric phaser includes at least one planet gear adjuster and at least one load generator. The load generator biases the planet gear adjuster, such that at a low rotational speed, the planet gear adjuster applies a force on the planet gear to take up the backlash between the planet gear and the ring gears. As the rotational speed increases, the inertia of a mass of the planet gear adjuster generates an increasing force opposing the force of the load generator, causing the planet gear adjuster to move at least one planet gear to a position where the at least one planet gear no longer takes up the backlash. In some embodiments, the planet gear adjuster includes an eccentric pin and an extension arm. In other embodiments, the planet gear adjuster includes a pivot support for a pair of inner and outer planet gears.