RV Reducer Backlash Design for Thermal Expansion Compensation
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Solution Overview
Problem
Domestic RV reducers in China suffer from high temperature rise, severe wear, short service life, and poor dynamic characteristics due to lack of research on rational meshing backlashes in cycloidal gears and inadequate thermal-structural coupling, leading to insufficient heat emission and backlash compensation.
Innovation Solution
A reducer design with a pin gear housing and two-stage reduction components, where cycloidal gears are modified to create a radial gap and backlash correlated with thermal expansion, using a positive equidistant-positive radial moving combination, with backlash ranging from 0.7-5 times the thermal expansion amount, and employing specific bearings for improved heat dissipation and load bearing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If modification with negative equidistant-negative radial moving combination is adopted, then manufacturing precision is improved, but backlash becomes too small to compensate for thermal expansion
Solution Approach 1:
The patent changes the modification parameters from negative equidistant-negative radial moving combination to positive equidistant-positive radial moving combination. This parameter change increases the backlash from insufficient levels (0.003-0.007mm) to an optimal range that compensates for thermal expansion, thereby improving reliability and service life while maintaining manufacturing precision
Solution Approach 2:
The patent applies preliminary anti-action by pre-setting the backlash through positive modification to counteract the harmful effect of thermal expansion during operation. The modification is designed in advance to ensure sufficient meshing backlash that will compensate for thermal effects, preventing sticking and wear before they occur
2Ease of manufacture
If conventional modification methods are used, then manufacturing simplicity is maintained, but thermal expansion compensation is insufficient leading to poor dynamic characteristics
Solution Approach 1:
The patent changes the modification approach from conventional methods to positive equidistant-positive radial moving combination with specifically optimized parameters. This maintains manufacturing simplicity while achieving the critical improvement of sufficient backlash for thermal expansion compensation, thereby improving dynamic characteristics and reliability
3Manufacturing precision
If backlash is reduced to increase precision, then manufacturing precision is improved, but thermal expansion causes parts to stick during operation
Solution Approach 1:
The patent changes the backlash parameter from insufficient levels to an optimized range through positive modification. This ensures the backlash is large enough to accommodate thermal expansion while maintaining high manufacturing precision, preventing the harmful effect of parts sticking during operation
Solution Approach 2:
The patent converts the harmful effect of thermal expansion into a beneficial design consideration by using positive modification to pre-set adequate backlash. This transforms the thermal expansion from a source of sticking and wear into a compensated factor that is already accounted for in the design, improving overall reliability
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 enhances dynamic characteristics by correlating backlash with thermal expansion, preventing overheating, and extending service life while maintaining conventional manufacture precision and low costs, allowing for mutual replacement with Japanese RV reducers.
Implementation Method 1
a rational meshing backlash is closely correlated with a thermal expansion amount of a cycloidal gear... the body expansion of a solid can be characterized by its linear expansion law in one direction... backlash Δc=(0.7-5)λ (mm), and λ denotes a thermal expansion amount of the cycloidal gear
Data Source
AI summary
A reducer for high precision control includes a pin gear housing and two-stage reduction components disposed therein: a first-stage reduction component including an input shaft, a sun gear and a planet gear; and a second-stage reduction component including 2-3 eccentric shafts distributed uniformly, cycloidal gears, a pin, a left rigid disk and a right rigid disk, and bearings, wherein the cycloidal gears are supported by bearings on two eccentric sections of the eccentric shaft, shaft extensions on two sides of the eccentric section of the eccentric shaft are supported by bearings on the left rigid disk and the right rigid disk, and the left rigid disk and the right rigid disk are supported by bearings in inner holes of two sides of the pin gear housing.