Single-Stage Planetary Gear Anti-Back Drive Mechanism
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Solution Overview
Problem
Current automotive seat adjuster drives with anti-back drive capability suffer from low mechanical efficiency, large packaging, excessive noise, high weight, and high manufacturing costs, and require multiple stages of gear reduction, which complicates the design and increases costs.
Innovation Solution
A single-stage gear reduction output mechanism with a planetary arrangement that includes an eccentric, first and second gears, and a locking plate with pins, which reduces friction and ensures anti-back drive capability, improving efficiency and compactness while maintaining anti-back drive functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worm and worm-wheel gear drives are used to achieve anti-back drive capability, then anti-back drive capability is provided, but mechanical efficiency decreases to 50% or lower
Solution Approach 1:
Instead of using conventional worm and worm-wheel gears where the worm drives the wheel, this patent inverts the approach by using a planetary gear system with a locked sun gear. The anti-back drive capability is achieved by preventing rotation in the reverse direction through a locking mechanism rather than relying on the inherent self-locking property of worm gears, thereby achieving over 90% mechanical efficiency while maintaining anti-back drive capability.
Solution Approach 2:
The patent changes the fundamental parameters of the gear system by transitioning from a worm gear mechanism to a planetary gear mechanism with a locked sun gear. This parameter change enables the system to achieve both high mechanical efficiency (>90%) and anti-back drive capability, overcoming the efficiency limitation of conventional worm gears.
2Power
If two-stage gear reduction is used to achieve high gear ratio and anti-back drive capability, then necessary output torque and speed are achieved, but device complexity increases
Solution Approach 1:
This patent merges the functions of two-stage gear reduction and anti-back drive capability into a single-stage planetary gear mechanism. By locking the sun gear and using the planetary gears with an eccentric, the system achieves both high gear ratio (300:1 to 700:1) and anti-back drive capability in one stage, eliminating the need for separate anti-back drive mechanisms and reducing overall device complexity.
Solution Approach 2:
The planetary gear mechanism serves multiple functions simultaneously: it provides high gear reduction ratio, achieves anti-back drive capability through the locked sun gear, and maintains compact packaging. This multi-functionality eliminates the need for additional components that would be required in a two-stage system, thereby reducing device complexity.
3Reliability
If conventional anti-back drive mechanisms are used, then anti-back drive capability is achieved, but packaging space increases
Solution Approach 1:
The patent employs a nested planetary gear arrangement where the planetary gears are positioned around the locked sun gear within a compact housing. The eccentric is nested within the planetary gear structure, and all components share a common centerline axis, achieving maximum space utilization and compact packaging while maintaining anti-back drive capability.
4Reliability
If multiple components are used to achieve anti-back drive capability, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
By merging the anti-back drive function into the planetary gear mechanism itself through the locked sun gear, the patent eliminates the need for separate anti-back drive components such as brakes or clutches. This integration reduces the total number of parts, simplifies manufacturing, and lowers assembly costs while maintaining reliable anti-back drive capability.
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 achieves a 7-15% improvement in mechanical efficiency, reduces noise, and lowers manufacturing costs while maintaining compactness and durability, ensuring effective anti-back drive capability in all operating conditions.
Implementation Method 1
The planetary arrangement of the first gear and the second gear reduces friction between the moving parts
Implementation Method 2
a locking plate and pins. The locking plate is disposed within the cavity of the gear housing and includes a first slot cutout, a second slot cutout, and a third slot cutout... The first pin extends through the third slot cutout in the locking plate and prevents the first gear from driving rotation of the second gear
Data Source
AI summary
A single-stage gear reduction output mechanism for an automotive seat assembly including a gear housing bracket, gear housing, axle shaft, eccentric, and first and second gears. The axle shaft extends through the eccentric with a slip fit, the first gear rotates with the axle shaft, and the second gear is carried on a first bearing surface of the eccentric and meshingly engages the first gear in a planetary arrangement. A locking plate including first, second, and third slot cutouts is disposed within the gear housing. A support pin extends from the gear housing through the first slot cutout and a second bearing surface of the eccentric extends through the second slot cutout to support the locking plate and limit its movement along a lateral axis. The second gear includes a first pin that extends through the third slot cutout to prevent the first gear from back-driving the second gear.