Crankshaft Needle Layout in Speed Reducers for Rigidity and 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 increase in rigidity and damping capacity.
Innovation Solution
A speed reducer design featuring 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 diameter of the crank journal is increased to improve rigidity and damping capability, then the rigidity and damping capability are improved, but the filling of the reducer is reduced and the overall size increases
Solution Approach 1:
The crankshaft is divided into multiple crank journals instead of using a single large-diameter crank journal. This segmentation allows the load to be distributed across multiple smaller bearing surfaces, achieving the required rigidity and damping capability without increasing the overall crankshaft diameter, thereby maintaining the filling of the reducer.
Solution Approach 2:
Multiple crank journals are arranged concentrically or in a compact configuration within the limited space of the reducer. This nesting approach maximizes the use of available space, allowing the crankshaft to achieve high rigidity and damping capability while maintaining a compact overall size and high filling factor.
2Strength
If the number of needles arranged around the crank journal 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 rows of needles arranged around different crank journals. This segmentation distributes the load across multiple needle rows, improving damping capability while maintaining a systematic and manageable structure that does not excessively increase complexity.
Solution Approach 2:
Needles are arranged in multiple rows and at different angular positions around the crank journals, utilizing the three-dimensional space efficiently. This multi-dimensional arrangement increases the number of contact points and damping capability while keeping the structural complexity manageable through systematic positioning.
Data Source
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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.