Reciprocating Tool Crank Balancer Support for Noise Reduction
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Solution Overview
Problem
Reciprocating tools with brushless motors experience abnormal noise and vibration due to rigidity issues and deviations in the crank mechanism when subjected to excessive loads, particularly in vertical crank configurations.
Innovation Solution
The tool design supports the balancer solely by an eccentric pin within the housing, and employs an integrally molded cylinder-type motor housing to enhance rigidity, reducing noise and vibration generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a half-split motor housing structure is used to reduce motor housing size, then the motor housing diameter is reduced, but the rigidity of the motor housing becomes insufficient
Solution Approach 1:
The motor housing is divided into two half housings that can be assembled together, allowing for easier manufacturing and assembly while maintaining adequate rigidity through the split structure design
Solution Approach 2:
The patent employs composite material construction for the motor housing, combining materials with different properties to achieve both reduced weight/volume and sufficient rigidity in the motor housing structure
2Reliability
If the balancer is supported by a bearing disposed on the housing inner surface, then the balancer is securely supported, but abnormal noise and vibration are generated when impact occurs during reciprocating member locking
Solution Approach 1:
The bearing supporting the balancer is extracted from the housing structure and relocated to the crank member itself, isolating the support function from the housing and preventing impact transmission to the housing that would cause abnormal noise and vibration
Solution Approach 2:
The crank member serves as an intermediary structure that supports the balancer through its own bearing, acting as a mediator between the balancer and the housing to prevent direct impact transmission that causes noise and vibration
3Device complexity
If the balancer is supported by the housing, then the structure is simple, but deviation in positional relationship between crank member and balancer generates abnormal noise and vibration
Solution Approach 1:
The support function for the balancer is merged with the crank member structure, combining the crank member's rotational function with the balancer support function in one integrated component, thereby maintaining simplicity while eliminating positional deviation issues
Data Source
AI summary
A reciprocating tool includes a motor, a reciprocating member, and a crank mechanism. The motor is disposed in a housing. The reciprocating member projects from the housing. The crank mechanism converts rotation of a rotation shaft of the motor into reciprocation of the reciprocating member. The crank mechanism rotates around an axis in a lateral direction by rotation transmission from the rotation shaft, and the crank mechanism includes a crank member having an eccentric pin, a connecting rod coupling the eccentric pin to the reciprocating member, and a balancer coupled to the eccentric pin, and the balancer is supported by the eccentric pin alone in the housing.