Epicyclic Gear Carrier Segments With Cam-Loaded Backlash Compensation
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Solution Overview
Problem
Epicyclic gear assemblies experience backlash due to wear, leading to inefficiencies and inaccuracies, particularly between planetary gears and outer fixed rings, which is a concern in safety-critical applications.
Innovation Solution
A backlash reduction mechanism using a planetary gear carrier with arcuate segments, a mechanical cam, and a spring to adjust the radial position of planetary gears, ensuring frictional engagement under normal loads and closing gaps when induced loads exceed friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guiding rings are used to compensate radial loads on planetary gears, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the backlash compensation function from the complex guiding ring structure and implements it through a simpler mechanism involving a movable carrier segment and spring assembly. The carrier segment can move radially to maintain gear meshing contact, while the spring provides the necessary radial force, eliminating the need for separate guiding rings.
Solution Approach 2:
Instead of using guiding rings to actively control radial loads, the patent inverts the approach by allowing the carrier itself to move radially in response to load variations. The spring mechanism provides passive compensation by automatically adjusting the carrier's radial position based on operating conditions.
2Reliability
If radial springs are used to urge planetary gears towards rings, then backlash is reduced, but gear tooth loading increases
Solution Approach 1:
The patent employs a dynamic carrier segment that can move radially to accommodate varying operational loads. Rather than applying constant spring force directly to the gears, the system dynamically adjusts the radial position of the carrier, allowing gear teeth to engage at optimal contact points that distribute loads more evenly.
Solution Approach 2:
The movable carrier segment acts as an intermediary between the spring mechanism and the planetary gears. It translates spring force into controlled radial positioning of the gears, mediating the interaction to achieve backlash reduction while managing gear tooth loading through controlled engagement.
3Manufacturing precision
If gear teeth are made smaller to reduce initial backlash, then manufacturing precision is improved, but wear resistance deteriorates
Solution Approach 1:
The patent implements preliminary action by pre-positioning the planetary gears radially outward from the sun gear using the spring-loaded carrier mechanism. This preliminary positioning ensures optimal initial meshing contact between gear teeth, establishing proper engagement before operational loads are applied, thereby reducing initial backlash without compromising tooth strength.
Solution Approach 2:
The system changes the radial position parameter of the planetary gears dynamically through carrier movement. By adjusting the radial distance between sun gear and planetary gears based on operational conditions, the system maintains optimal tooth engagement parameters throughout the gear assembly's service life, compensating for wear effects.
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 mechanism effectively reduces backlash by maintaining optimal gear engagement, enhancing efficiency and accuracy, even as gears wear, by adjusting the planetary gears' position in response to radial loads.
Implementation Method 1
a spring biasing the mechanical cam relative to the carrier in the bore
Implementation Method 2
the cam is designed to have a cam angle such that the cam is held in frictional engagement with the carrier when the induced load from the planetary gears is less than the friction at the interface between the carrier and the cam
Data Source
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AI summary
An epicyclic gear assembly comprising: a sun gear rotatable about an axis (A); a plurality of planetary gears (200) arranged around and in meshing engagement with the sun gear such that rotation of the sun gear about its axis causes corresponding rotation of each of the planetary gears about their own axes; and an outer ring gear (300), located axially between two fixed outer rings (400), the outer ring gear (300) arranged around and in meshing engagement with the plurality of planetary gears such that rotation of the planetary gears causes rotation of the outer ring gear about the axis A and relative to the fixed outer rings; the assembly further comprising: a backlash reduction mechanism between the planetary gears and the outer ring gear, the backlash reduction mechanism comprising: a planetary gear carrier (500) comprising a plurality of carrier segments (500a) each carrying a respective one of the planetary gears (200), the segments together defining an annular carrier having a bore therethrough; a mechanical cam (600) supported within the bore and having a cam profile interfacing with the carrier; and a spring (700) biasing the mechanical cam relative to the carrier in the bore; wherein the cam is designed to have a cam angle such that the cam is held in frictional engagement with the carrier when the induced load from the planetary gears is less than the friction at the interface between the carrier and the cam, and wherein the cam moves relative to the carrier under the force of the spring when the induced load between the carrier and the cam exceeds the friction.