Needle-Bearing Speed Reducer for Rigidity and Vibration Damping
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Solution Overview
Problem
Conventional speed reducers face challenges in achieving high torsional rigidity and damping capability due to limitations in crank journal diameter and filling, which restricts the enhancement of rigidity and damping performance.
Innovation Solution
The design includes a case with internal teeth, multiple crankshafts arranged on an imaginary circle, eccentric members, and a carrier that supports the crankshafts, with specific diameter ratios and needle arrangements to increase the cross-sectional area and number of contacts, thereby enhancing rigidity and damping capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the crank journal diameter is increased to improve rigidity and damping capability, then the rigidity and damping capability are improved, but the filling of the reducer increases and the design space is constrained
Solution Approach 1:
The crankshaft is divided into multiple crank journals instead of using a single large crank journal. This segmentation allows the total load-bearing area to be distributed across multiple smaller journals, achieving the required rigidity and damping capability without increasing the overall crankshaft diameter excessively, thus maintaining better filling ratios in the reducer.
Solution Approach 2:
Multiple crank journals are arranged concentrically or in a compact configuration, allowing them to occupy space more efficiently. This nested arrangement enables the crankshaft to achieve high rigidity through multiple contact points while minimizing the overall volume occupied by the crankshaft assembly.
2Strength
If the number of needles arranged around the eccentric member is increased to improve damping capability, then the damping capability is improved, but the complexity of the bearing structure increases
Solution Approach 1:
The bearing structure is segmented into multiple needle rows arranged around the eccentric member. Each row of needles independently contributes to load distribution and damping. This segmentation allows the system to achieve high damping capability through multiple contact points while maintaining modular construction that simplifies manufacturing and assembly compared to a single complex bearing structure.
Data Source
AI summary
A speed reduce according to an embodiment of the present invention includes a case having an outer diameter D, a plurality of crankshafts, and a carrier supporting the crankshafts in a rotatable manner. The carrier is rotatable by the crankshafts relative to the case. Each of the plurality of crankshafts includes a plurality of eccentric members each of which has a diameter dc1 and a crank journal that has a diameter dc2. The crankshaft further includes n1 needles that are arranged around each of the plurality of eccentric members and each of which has a diameter size dr1, and n2 needles that are arranged around the crank journal and each of which has a diameter size dr2. In the speed reducer, relational expression 5.5≤D/dc1≤7.0 is satisfied.