Shaft monitoring system

Patent metadata

Field	Value
Publication number	US-11313245-B2
Application number	US-202016747745-A
Country	US
Kind code	B2
Filing date	Jan 21, 2020
Priority date	Jan 28, 2019
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

A monitoring system for monitoring one or more properties associated with a rotating shaft is provided. The system includes a first phonic wheel which is mounted coaxially to the shaft for rotation therewith, the first phonic wheel comprising a circumferential row of teeth. The system further includes a first sensor configured to detect the passage of the row of teeth of the first phonic wheel by generating a first alternating measurement signal. The system further includes a processor unit configured to determine the durations of successive first speed samples. Each first speed sample is a block of n successive cycles of the first alternating measurement signal, where n is an integer, and in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle. At least one axial location of the first phonic wheel every mth tooth of the row of teeth of the first phonic wheel has a circumferential thickness which is different from that of the other teeth of the first phonic wheel, where m is an integer, m≠n, and m is neither a factor nor a multiple of n. When the first sensor is positioned at said axial location of the first phonic wheel and at any given rotational speed of the first phonic wheel, the durations of the successive first speed samples display a characteristic repeating pattern of longer and shorter sample durations relative to the average duration of the successive first speed samples. The amount by which the longer and shorter sample durations differ from the average duration is in proportion to the amount by which the circumferential thickness of the mth teeth differs from that of the other teeth at said axial location of the first phonic wheel. The processor unit monitors the properties associated with the rotating shaft from the characteristic repeating pattern.

First claim

I claim:

1. A monitoring system for monitoring one or more properties associated with a rotating shaft, the system comprising:
a first phonic wheel which is mounted coaxially to the shaft for rotation therewith, the first phonic wheel comprising a circumferential row of teeth;
a first sensor configured to detect the passage of the row of teeth of the first phonic wheel by generating a first alternating measurement signal; and,
a processor unit configured to determine the durations of successive first speed samples, each first speed sample being a block of n successive cycles of the first alternating measurement signal, where n is an integer, and in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle; wherein,
at at least one axial location of the first phonic wheel every m th tooth of the row of teeth of the first phonic wheel has a circumferential thickness which is different from that of the other teeth of the first phonic wheel, where m is an integer, m≠n, and m is neither a factor nor a multiple of n, whereby when the first sensor is positioned at said axial location of the first phonic wheel and at any given rotational speed of the first phonic wheel, the durations of the successive first speed samples display a characteristic repeating pattern of longer and shorter sample durations relative to the average duration of the successive first speed samples, the amount by which the longer and shorter sample durations differ from the average duration being in proportion to the amount by which the circumferential thickness of the m th teeth differs from that of the other teeth at said axial location of the first phonic wheel; and,
the processor unit monitors the properties associated with the rotating shaft from the characteristic repeating pattern.

2. The monitoring system as claimed in claim 1 , wherein the other teeth of the first phonic wheel are identical to each other.

3. The monitoring system as claimed in claim 1 , wherein the other teeth of the first phonic wheel comprise a constant circumferential thickness with distance in the axial direction of the shaft.

4. The monitoring system as claimed in claim 1 , wherein the m th teeth of the first phonic wheel vary in circumferential thickness with distance in the axial direction of the shaft.

5. The monitoring system as claimed in claim 4 , wherein at at least one axial position the circumferential thickness of the m th teeth of the first phonic wheel is the same as the circumferential thickness of the other teeth of the first phonic wheel at that axial position.

6. The monitoring system as claimed in claim 4 , wherein the m th teeth of the first phonic wheel comprise a step change in circumferential thickness at a given axial position.

7. The monitoring system as claimed in claim 4 , wherein the m th teeth of the first phonic wheel vary continuously in circumferential thickness with distance in the axial direction of the shaft.

8. The monitoring system as claimed in claim 1 , wherein the monitored properties associated with the rotating shaft include the axial position of the shaft.

9. The monitoring system as claimed in claim 1 , wherein the monitored properties associated with the rotating shaft include bowing of the shaft.

10. The monitoring system as claimed in claim 1 , wherein the monitored properties associated with the rotating shaft include the rotational speed of the shaft.

11. The monitoring system as claimed in claim 1 , further comprising:
a second sensor configured to detect the passage of the row of teeth of the first phonic wheel by generating a second alternating measurement signal; wherein,
the processor unit is further configured to determine the durations of successive second speed samples, each second speed sample being a block of n successive cycles of the second alternating measurement signal in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle, whereby when the second sensor is positioned at said axial location of the first phonic wheel and at any given rotational speed of the first phonic wheel, the durations of the successive second speed samples also display the characteristic repeating pattern; and,
the processor unit monitors the properties associated with the rotating shaft from the characteristic repeating patterns displayed by the durations of the successive first speed samples and the durations of the successive second speed samples.

12. The monitoring system as claimed in claim 1 , further comprising:
a second phonic wheel which is mounted coaxially to the shaft for rotation therewith, the second phonic wheel comprising a circumferential row of teeth, and the second phonic wheel being axially spaced along the shaft from the first phonic wheel; and,
a third sensor configured to detect the passage of the row of teeth of the second phonic wheel by generating a third alternating measurement signal; wherein,
the processor unit is further configured to determine the durations of successive third speed samples from the third sensor, each third speed sample being a block of n successive cycles of the third alternating measurement signal in which the beginning of each cycle is a zero-crossing point from the previous cycle and the end of each cycle is the corresponding zero-crossing point to the next cycle;
at at least one axial location every m th tooth of the row of teeth of the second phonic wheel has a circumferential thickness which is different from that of the other teeth the second phonic wheel, whereby when the third sensor is positioned at said axial location of the second phonic wheel and at any given rotational speed of the second phonic wheel, the durations of the successive third speed samples also display the characteristic repeating pattern; and,
the processor unit is further configured to determine the relative phase between the characteristic repeating pattern of the first speed samples and the characteristic repeating pattern of the third speed samples, whereby the monitored properties associated with the rotating shaft include twist of the shaft as determined from the relative phase.

13. A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a compressor and a core shaft connecting the turbine to the compressor; and,
a monitoring system as claimed in claim 1 for monitoring the core shaft, the or each phonic wheel being mounted coaxially to the core shaft for rotation therewith.

14. A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and,
a gearbox that receives an input from the core shaft and outputs drive to the fan via an output shaft so as to drive the fan at a lower rotational speed than the core shaft;
a thrust shaft that extends through the gearbox to connect the fan to an axial location bearing mounted on the core shaft, thereby relieving the output shaft of responsibility for axially locating the fan relative to the core shaft; and,
a monitoring system as claimed in claim 8 for monitoring the axial position of the thrust shaft, the first phonic wheel being mounted coaxially to the thrust shaft for rotation therewith.

Assignees

• Rolls Royce Plc

Inventors

• Hill Ralph W

Classifications

• B64U50/12

  using turbine engines, e.g. turbojets or turbofans · CPC title

• G01B7/003

  for measuring position, not involving coordinate determination (coordinate measuring G01B7/004) · CPC title

• G01M13/00 Primary

  Testing of machine parts · CPC title

• G01M13/025

  Test-benches with rotational drive means and loading means; Load or drive simulation · CPC title

• G01P3/489

  Digital circuits therefor · CPC title