Ball Screw Spring Assembly for Uniform Compression Stroke
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Solution Overview
Problem
The existing non-circulating ball screw devices experience uneven compression deformation of coil springs, leading to reduced lifespan and limited movement stroke due to frictional resistance and uneven distribution of force, resulting in potential misalignment and unpredictable behavior of spring end portions.
Innovation Solution
The ball screw device employs a configuration where coil springs are arrayed in a row between the end portion ball and the stopper, with varying spring end and middle portion properties, including higher rigidity at the end portions to stabilize orientation and behavior, and adjustable spring constants to achieve uniform compression deformation, thereby extending coil spring life and increasing movement stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coil spring is used between the end portion ball and the stopper, then the structure is simple, but the compression deformation is uneven and the spring life is reduced
Solution Approach 1:
The single coil spring is divided into multiple coil springs (first coil spring and second coil spring) arranged in series between the end portion ball and the stopper. This segmentation allows each spring to undergo more uniform compression deformation, preventing localized stress concentration and extending the overall spring assembly life.
Solution Approach 2:
The patent applies different spring constants to different positions by using multiple coil springs with varying properties. The first coil spring has a different spring constant than the second coil spring, allowing each to be optimized for its specific position and deformation characteristics, thereby achieving more uniform overall compression.
2Device complexity
If a single coil spring is used, then the structure is simple, but the movement stroke of the nut is limited
Solution Approach 1:
By dividing the spring system into multiple coil springs arranged in series, the total compression distance is distributed across multiple elements. This enables the nut to achieve a larger overall movement stroke while maintaining controlled deformation in each individual spring.
3Ease of manufacture
If the spring end portions have the same form as the middle portions, then the manufacturing is simple, but the spring end portions may become misaligned leading to unpredictable behavior
Solution Approach 1:
The spring end portions are given different properties from the middle portions, specifically higher rigidity. This local differentiation ensures that the end portions maintain stable orientation and predictable behavior during compression, while the middle portions provide the necessary elasticity for energy storage and release.
4Device complexity
If the coil springs have uniform spring constant, then the design is simple, but the compression deformation is not uniform across the spring assembly
Solution Approach 1:
Different coil springs are assigned different spring constants based on their positions in the assembly. This allows each spring to contribute appropriately to the overall compression deformation, achieving uniform distribution of deformation across the entire spring assembly while managing the complexity through systematic design.
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 ensures stable and uniform compression deformation of coil springs, extending their lifespan and enhancing the movement stroke of the nut by optimizing the rigidity and behavior of spring end portions, ensuring predictable performance and increased operational efficiency.
Implementation Method 1
the coil springs can be subjected to compression deformation as a whole between the end portion ball and the stopper
Implementation Method 2
due to frictional resistance between the coil spring 93 and the helical grooves 90a and 94a
Data Source
AI summary
A ball screw device includes a screw shaft that has a first helical groove on an outer circumference, a nut that has a second helical groove on an inner circumference, a plurality of balls, a stopper provided at an end portion of the second helical groove, and a spring body that is placed between an end portion ball closest to the stopper and the stopper. The spring body is configured of a plurality of coil springs arrayed along the first helical groove and the second helical groove. The coil springs that are adjacent each have a spring end portion of which rigidity is higher than rigidity of a spring middle portion.