Electric Actuator Differential Bearing Layout for Compact Rigidity
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Solution Overview
Problem
Existing electric actuators face challenges in achieving a high speed reduction ratio without increasing size, and their efficiency is compromised due to reduced rigidity and uneven radial loads, particularly in cycloid speed reducers supported by a single needle roller bearing, leading to friction-related losses.
Innovation Solution
The electric actuator employs a differential device with a planetary rotary body supported by both a needle roller bearing and a deep-groove ball bearing, which increases the rigidity of the speed reducers and prevents skew, while dimples on tooth surfaces facilitate oil film formation to reduce friction and enhance lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a cycloid speed reducer is supported by only one needle roller bearing, then the radial dimension can be minimized, but the rigidity is insufficient and radial load becomes uneven
Solution Approach 1:
The patent combines two different bearing types (needle roller bearing and deep groove ball bearing) to support the planetary rotary body. The needle roller bearing handles axial directions while the deep groove ball bearing handles radial directions, merging their functions to achieve both compact radial dimension and sufficient rigidity under radial loads
2Power
If tooth surfaces slide against each other to transmit power, then speed reduction is achieved, but friction between tooth surfaces reduces efficiency
Solution Approach 1:
The patent changes the physical state of the tooth surfaces by forming dimples that alter the lubrication parameters. This creates favorable conditions for oil film formation, changing the friction characteristics from direct sliding contact to fluid film lubrication, thereby reducing energy loss while maintaining power transmission
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
This configuration enhances the rigidity of the speed reducers, prevents efficiency reduction, and allows for a compact design by minimizing radial dimensions, thereby improving the overall performance and efficiency of the electric actuator.
Implementation Method 1
By one needle roller bearing arranged on the inner side of the eccentric member, the planetary rotary body is supported so as to be rotatable with respect to the eccentric member
Implementation Method 2
a second bearing configured to support the planetary rotary body at a position shifted in an axial direction so as to be prevented from overlapping the rotor, wherein the second bearing is a deep-groove ball bearing
Implementation Method 3
dimples on tooth surfaces facilitate oil film formation to reduce friction and enhance lubrication
Data Source
AI summary
A differential device (5) of an electric actuator (1) includes a driving rotary body (2), a driven rotary body (3), and a planetary rotary body (52). A first speed reducer (5a) is formed between the planetary rotary body (52) and the driving rotary body (2). A second speed reducer (5b) is formed between the planetary rotary body (52) and the driven rotary body (3). The electric actuator (1) includes a first bearing (53) configured to support the planetary rotary body (52) on an inner side of a rotor (42) of an electric motor (4), and a second bearing (54) configured to support the planetary rotary body (52) at a position shifted in an axial direction so as to be prevented from overlapping the rotor (42). The second bearing (54) is formed of a deep-groove ball bearing.