Spindle Bearing Pneumatic Gap Sensing for Axial Displacement
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Solution Overview
Problem
Existing machine tool spindle systems face challenges in accurately measuring axial displacement of rotary shafts supported by rolling bearings, as prior methods are complex, prone to damage, and lack high-resolution capability, while also failing to measure axial displacement effectively.
Innovation Solution
A bearing device that uses compressed gas to measure axial displacement by injecting gas into a gap between the rotary and stationary members, with a gas collection groove to collect the gas, allowing for precise axial direction displacement measurement without contacting the rotary member, and calculates the axial load based on pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-contact type sensor is arranged in the vicinity of the measurement target to measure shaft displacement, then measurement precision is improved, but device complexity increases and the sensor is prone to damage from chips and cutting water
Solution Approach 1:
The patent introduces compressed gas as an intermediary medium to transfer displacement information from the rotary shaft to the stationary sensor. The gas is injected into the gap between the rotary shaft and stationary member, and pressure changes in the gas reflect the axial displacement of the shaft, allowing indirect measurement without placing sensors near the rotating component.
Solution Approach 2:
The patent replaces the direct mechanical contact measurement system (sensors mounted near the rotary shaft) with a pneumatic measurement system. Instead of using mechanical or electrical sensors in close proximity to the shaft, the system uses compressed gas pressure changes to convey displacement information to a stationary pressure sensor located away from the rotating component.
2Measurement precision
If high-resolution displacement sensors are used to measure shaft displacement of several μm, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive high-resolution mechanical or capacitive displacement sensors with a much simpler and cheaper pneumatic pressure sensing system. The compressed gas pressure changes, which are proportional to the axial displacement, are measured by ordinary pressure sensors, achieving the same measurement function at significantly lower cost.
Solution Approach 2:
The patent employs pneumatic principles by injecting compressed gas into the gap between the rotary shaft and stationary member. The pressure variations in the trapped gas directly reflect the axial displacement of the shaft, enabling measurement through pressure sensing rather than direct displacement sensing, thereby reducing cost while maintaining precision.
3Measurement precision
If a displacement sensor and its wiring are arranged in the vicinity of the measurement target, then measurement precision is improved, but reliability decreases due to damage from chips and cutting water
Solution Approach 1:
The patent uses compressed gas as an intermediary to transmit displacement information from the hazardous rotating shaft environment to a safe stationary location. The gas carries the measurement information through the gap without requiring physical sensors in the dangerous zone, protecting the sensing system from chips and cutting water.
Solution Approach 2:
The patent substitutes the vulnerable mechanical/electrical sensor system with a pneumatic transmission system. Instead of placing sensors and wiring near the rotating shaft where they are exposed to chips and cutting water, the system uses compressed gas pressure changes to convey displacement data to a protected stationary pressure sensor.
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
Enables simple, high-accuracy measurement of axial displacement and load on the rotary shaft, reducing complexity and potential damage, while effectively supporting rotary members with rolling bearings.
Implementation Method 1
a displacement detecting unit for measuring an axial direction displacement of the rotary member by supplying compressed gas into a gap to be measured, formed in an axial direction, between the rotary member and the stationary member
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(c)
AI summary
A purpose of the present invention is to provide a bearing device and machine tool spindle apparatus (10) that can contactlessly and precisely measure an axial direction displacement of a rotary member (21) in a configuration that supports the rotary member with rolling bearings (31, 41), without disposing a measurement unit near the rotary member. The bearing device supports the rotary member relative to a stationary member (11) with the rolling bearings interposed therebetween, and includes a displacement measurement unit (60) that supplies a compressed gas to a gap to be measured (g) between the rotary member and the stationary member in the vicinity of the rolling bearings, and measures the displacement of the rotary member in the axial direction. The gap (g) is formed by a surface of the rotary member and a surface of the stationary member, which face each other in the axial direction. In addition, a gas collection groove (85a, 85b) for collecting the compressed gas is provided on one or both sides of a nozzle (62) adapted to inject the compressed gas.