Compact Parallel Eccentric Rotary Actuator Shock Resistance
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Solution Overview
Problem
Existing parallel eccentric rotary actuators face durability challenges under high shock levels experienced in heavy construction machinery, as they are sensitive to peak loads and shocks, and require components like involute gear teeth and rolling element bearings that are prone to deformation and low stiffness.
Innovation Solution
The Compact Parallel Eccentric (CPE) rotary actuator design features a crankshaft with eccentrics driving parallel gears, Oldham coupling with multiple tongue and groove surfaces for high contact area and stiffness, and a stator with internal support plates for rigidity, eliminating rolling element bearings from the load path to absorb torque shocks and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rolling element bearings and involute gear teeth are used in parallel eccentric rotary actuators, then the actuators can operate under normal load conditions, but they exhibit low stiffness and are prone to deformation under high shock loads
Solution Approach 1:
The patent removes rolling element bearings from the load path entirely, replacing them with a surface feature interface between the eccentric gear and crosslink. This extraction eliminates the inherent compliance and deformation issues of rolling element bearings under shock loads, directly resolving the stiffness problem while maintaining operational reliability.
Solution Approach 2:
The patent employs circular arc gear teeth instead of involute gear teeth. The circular arc geometry provides more favorable contact characteristics under shock loads, distributing forces more effectively and reducing peak stresses that cause deformation in involute gear systems.
2Reliability
If traditional parallel eccentric gear trains are designed to handle high shock loads, then durability improves, but the actuators require larger components that increase overall size and reduce torque density
Solution Approach 1:
The patent merges the bearing function with the gear interface by using surface features directly on the eccentric gear and crosslink. This eliminates the need for separate bearing components, reducing overall size while maintaining shock resistance through the rigid surface feature connection.
Solution Approach 2:
The patent changes the geometric parameters of the gear system by using circular arc teeth with specific radius ratios and optimizing the surface feature dimensions. These parameter changes allow the compact design to handle shock loads effectively without requiring oversized components.
3Force
If rolling element bearings are used in the gear train, then the actuator can support radial loads, but friction losses increase and efficiency decreases
Solution Approach 1:
The patent extracts rolling element bearings from the system and replaces them with a direct surface feature interface. This eliminates the rolling friction and associated energy losses while maintaining the ability to support radial loads through the rigid connection between the eccentric gear and crosslink.
4Reliability
If multiple components including bearings, gear teeth, and crosslinks are used to achieve shock resistance, then reliability improves, but device complexity increases
Solution Approach 1:
The patent combines the bearing support function with the gear and crosslink structure by using surface features integrated into these components. This merging reduces the total number of discrete components while maintaining durability through the rigid, deformation-resistant surface feature interface.
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 CPE rotary actuator achieves exceptional shock resistance, high torque density, and reduced friction losses, making it suitable for heavy-duty applications with improved durability and efficiency compared to previous designs.
Implementation Method 1
Oldham coupling with multiple tongue and groove surfaces for high contact area and stiffness
Implementation Method 2
eccentric gears equipped with circular arc gear teeth
Implementation Method 3
crankshaft with eccentrics driving parallel gears
Data Source
AI summary
A rotary actuator (101) is provided which includes a crankshaft (103), first and second eccentric gears (121), first and second end plates (123), a first crosslink (117) which is disposed between the first eccentric gear and the first end plate, a second crosslink which is disposed between the second eccentric gear and the second end plate, a stator (113) disposed between the first and second eccentric gears, and a rotor (109). Preferably, the rotary actuator further includes first and second support plates (115) which are disposed concentrically about the crankshaft and which are attached to first and second surfaces of the stator, respectively. The foregoing configuration allows the stator to serve as a major structural element, which may enhance the stiffness and reduce the weight of the actuator, while simplifying many of its active components.