Screw Shaft Support Mechanism With Hydraulic Axial Rigidity Adjustment
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Solution Overview
Problem
Existing rotation support devices, such as ball screw feeding devices and spindle devices, face challenges in maintaining axial support rigidity when the rotation shaft length changes due to heat, leading to potential bearing damage and increased size and cost due to external fluid supply systems.
Innovation Solution
A rotation support device with a pair of support mechanisms, each including a bearing unit and a housing position adjustment mechanism, utilizing a hollow member within a pressure chamber filled with a working fluid to maintain axial rigidity without external accumulators or pumps, allowing the support mechanisms to adjust to changes in shaft length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a disc spring is used to apply tension to the feed screw, then the load can be applied to maintain support rigidity, but the load weakens as the shaft extends and can only cope with temperature rise of 3 to 4 degrees
Solution Approach 1:
The patent uses a hydraulic pressure generating unit that generates hydraulic pressure within a housing, utilizing fluid pressure to apply axial load to the rotation shaft. This hydraulic mechanism provides continuous and stable support rigidity across a wide temperature range, overcoming the limitation of disc springs that only work for small temperature rises of 3-4 degrees.
2Strength
If a fluid is supplied from outside to apply load by hydraulic pressure, then sufficient load can be applied to maintain support rigidity, but an external device such as a hydraulic pump is required, increasing size and energy consumption
Solution Approach 1:
The patent extracts the hydraulic pressure generating function from external devices and integrates it directly into the housing of the support mechanism. The hydraulic pressure generating unit is self-contained within the housing, eliminating the need for external hydraulic pumps and supply systems, thereby reducing device complexity and energy consumption while maintaining sufficient support rigidity.
Solution Approach 2:
The hydraulic pressure generating unit operates autonomously within the housing, using the relative movement between the rotation shaft and housing to generate hydraulic pressure automatically. This self-service mechanism eliminates dependence on external energy sources and complex control systems, simplifying the overall device configuration.
3Strength
If excessive pretension is applied to the feed screw, then support rigidity is improved, but a large load is applied to the bearing which may result in damage
Solution Approach 1:
The patent employs a dynamic load adjustment mechanism where the hydraulic pressure generating unit automatically adjusts the axial load on the rotation shaft based on thermal expansion. As the shaft expands with temperature increase, the relative movement between the shaft and housing generates hydraulic pressure that applies appropriate tension, maintaining optimal support rigidity without subjecting bearings to excessive static pretension loads.
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 device maintains continuous and stable axial support rigidity, prevents bearing damage, reduces size and energy consumption, and simplifies the configuration by eliminating the need for external fluid supply systems.
Implementation Method 1
a working fluid filling a space other than the hollow member in the pressure chamber
Implementation Method 2
when the feed screw extends beyond the pretension due to a temperature rise
Data Source
Figure 1
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Figure 3
AI summary
A support mechanism (30) that rotatably supports both ends of a screw shaft (21) in an axial direction comprises: a bearing unit (41) having a moving-side bearing housing (51) and a pair of angular ball bearings (33) fit inside the moving-side bearing housing (51); a support base (43) that is disposed on an axial side with respect to the bearing unit (41) and through which the screw shaft (21) passes; and a housing position adjustment mechanism (44) disposed between the bearing unit (41) and the support base (43). The housing position adjustment mechanism (44) comprises: a support base-side member (61) provided on the support base (43) side; a bearing housing-side member (62) provided on the bearing housing (51) side and movable in the axial direction relative to the support base-side member (61); a hollow member (90) disposed in a pressure chamber (66) formed between the support base-side member (61) and the bearing housing-side member (62); and a working fluid (70) that fills a space other than the hollow member (90) in the pressure chamber (66). This makes it possible to continuously and stably maintain a support stiffness in the axial direction even when the length of the rotating shaft in the axial direction changes due to the influence of heat.