Screw Shaft Support Mechanism for Thermal Expansion Preload Control
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Solution Overview
Problem
Existing rotation support devices, such as ball screw feeding devices and spindle devices, face issues with maintaining axial support rigidity when the rotation shaft extends due to thermal expansion, leading to potential bearing damage and increased costs from external hydraulic 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 working fluid in a pressure chamber with an elastic member and a hollow member to maintain axial rigidity and damp vibrations, without requiring external pumps or accumulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large pre-tension load is applied to the feed screw to maintain axial rigidity, then support rigidity is improved, but the bearing may be damaged due to excessive load
Solution Approach 1:
The patent employs a dynamic load adjustment mechanism where the preload on the feed screw can be automatically adjusted based on thermal expansion. The elastic member (spring) and fluid pressure system work together to maintain optimal preload levels - when the feed screw expands due to heat, the system reduces the preload accordingly, preventing excessive bearing loads while maintaining rigidity during normal operation
Solution Approach 2:
The system changes the preload parameter dynamically in response to temperature changes. By using the elastic member and fluid pressure chamber, the preload force is adjusted as a function of thermal expansion, transforming from a static high preload to a dynamic variable preload that adapts to thermal conditions, thus protecting bearings while maintaining rigidity
2Strength
If a disc spring is used to apply pre-tension load, then axial rigidity is maintained for small temperature rises (3-4 degrees), but the load becomes weaker as the shaft extends and is insufficient for larger temperature rises
Solution Approach 1:
The patent introduces a fluid pressure system as an intermediary between the elastic member and the bearing unit. The fluid (oil or gas) in the pressure chamber transmits and amplifies the force from the elastic member, providing a more effective and controllable preload application mechanism that can handle larger temperature excursions beyond what a disc spring alone could achieve
Solution Approach 2:
The system uses hydraulic or pneumatic principles with a fluid-filled pressure chamber to transmit and regulate the preload force. This fluid pressure mechanism provides smooth, continuous force application and better adaptability to thermal expansion compared to mechanical spring elements alone, enabling the system to maintain rigidity across a wider temperature range
3Strength
If a hydraulic pressure system with external fluid supply is used to apply load, then axial rigidity can be maintained, but external devices such as hydraulic pumps are required, increasing device size, cost, and energy consumption
Solution Approach 1:
The system is self-contained, using an elastic member (spring) that is pre-loaded within the device to provide the necessary preload force. The fluid pressure chamber works with this internal elastic member to automatically adjust and maintain preload without requiring external hydraulic pumps, fluid reservoirs, or control systems, thereby simplifying the overall device structure while maintaining rigidity
Solution Approach 2:
The elastic member is pre-compressed during assembly to store potential energy and provide the initial preload force. This preliminary action eliminates the need for external active systems during operation - the pre-loaded spring automatically compensates for thermal expansion through the fluid pressure mechanism, removing the need for external pumps and control systems
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 stabilizes axial support rigidity and damps vibrations in both axial and radial directions, even with thermal expansion, preventing bearing damage and reducing energy consumption.
Implementation Method 1
an elastic member disposed in a compressed state between opposite end surfaces in the axial direction of the support base side member and the bearing housing side member in the pressure chamber
Implementation Method 2
a hollow member accommodated in the storage chamber
Implementation Method 3
an orifice allowing the pressure chamber to communicate with the storage chamber
Data Source
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AI summary
A support mechanism (30) for rotatably supporting both axial end portions of a screw shaft (21) comprises: a bearing unit (41) having a moving-side bearing housing (51) and a pair of angular ball bearings (33B); a support base (43); 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 capable of relative movement in the axial direction with respect to the support-base-side member (61); a working fluid accommodated in a pressure chamber (66) formed between the support-base-side member (61) and the bearing-housing-side member (62), in a storage chamber (71) formed in either the support-base-side member or the bearing-housing-side member, and in an orifice (72) establishing communication between the pressure chamber (66) and the storage chamber (71); a disc spring (80) disposed inside the pressure chamber (66) in a state compressed between the opposing axial end surfaces of the support-base-side member (61) and the bearing-housing-side member (62); and a hollow member (90) accommodated in the storage chamber (71). Consequently, the support rigidity in the axial direction can be continuously and stably maintained, even if the axial length of a screw shaft or a rotary shaft changes owing to the effect of heat.