Single mode optical fiber and detection device for bearing wear measurement

Abstract

The application discloses a single-mode optical fiber and a detection device for bearing wear measurement, wherein first and second chirped fiber gratings are spaced apart inside the single-mode optical fiber, the first and second chirped fiber gratings have the same parameters and are cascaded in the same chirp direction, the first / second chirped fiber grating end is the light source signal incident end, and the second / first chirped fiber grating end is the light source signal emission end. The FP cavity formed by the chirped fiber gratings with the same parameters can generate fine and large numbers of interference fringes, so that high-precision measurement of the bearing wear amount can be realized according to the relationship between the number of interference fringes and the grating length.

Description

Technical Field

[0001] This invention relates to the field of bearing wear measurement technology, and more specifically to a single-mode optical fiber and detection device for bearing wear measurement. Background Technology

[0002] Sliding bearings play a crucial role as an important component of marine propulsion systems. However, they are prone to wear during use, and if not detected in time, can lead to mechanical failures or even major accidents.

[0003] Currently, monitoring methods are mainly based on indirect measurement, including oil vibration noise method, acoustic emission method and strain method. Although the above methods can measure wear in real time, their accuracy is low.

[0004] Therefore, how to provide a new wear measurement method to improve measurement accuracy is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a single-mode optical fiber and detection device for measuring bearing wear, the main purpose of which is to achieve high-precision measurement of bearing wear.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A single-mode optical fiber for measuring bearing wear is characterized in that it has a first chirped fiber grating and a second chirped fiber grating etched internally at intervals. The first chirped fiber grating and the second chirped fiber grating have the same parameters and are cascaded in the same chirping direction. The end of the first chirped fiber grating is the light source signal input end, and the end of the second chirped fiber grating is the light source signal output end; or the end of the second chirped fiber grating is the light source signal input end, and the end of the first chirped fiber grating is the light source signal output end.

[0008] Preferably, the parameters include gate length, chirp coefficient, and chirp direction.

[0009] Preferably, the other end of the first / second chirped fiber Bragg grating is also engraved with a Bragg fiber Bragg grating, so that the Bragg fiber Bragg grating end is always located on the side closer to the light source, serving as the light source signal incident end.

[0010] A detection device for measuring bearing wear, characterized in that it comprises a bearing wear detection sensor, a scanning laser, and a signal demodulation system connected in sequence.

[0011] The bearing wear detection sensor includes a ferrite bolt and an armored housing. The ferrite bolt has a single-mode optical fiber embedded inside, as described above, for measuring bearing wear. The armored housing is used to fix the ferrite bolt to the optical fiber patch cord.

[0012] The scanning laser is connected to the bearing wear detection sensor via the fiber optic jumper. The scanning laser is a four-channel scanning laser, used to simultaneously measure wear at multiple points on the bearing.

[0013] Preferably, the output light source of the scanning laser is broadband light with a resolution of 20 pm.

[0014] Preferably, the parameters and spacing of the first chirped fiber grating and the second chirped fiber grating are determined according to the resolution of the laser scanner.

[0015] A bearing wear measurement device is characterized in that the scanning channel of the scanning laser is equipped with a switch to enable single-channel measurement at different positions.

[0016] As can be seen from the above technical solution, the present invention discloses a single-mode optical fiber and detection device for measuring bearing wear. By simultaneously writing a pair of chirped fiber gratings with identical parameters on the same single-mode optical fiber to form a chirped fiber grating-FP, and using the number of interference fringes of the chirped fiber grating-FP to perform high-precision demodulation of the wear amount of the sliding bearing, the present invention uses the linear relationship between the number of interference fringes of the chirped fiber grating-FP and the grating area length to complete the measurement of the wear amount of the sliding bearing. This technology is not easily affected by the environment and can realize early monitoring of bearing wear, effectively improving the measurement accuracy of wear amount on the basis of existing technology.

[0017] Simultaneously, leveraging the temperature sensitivity of Bragg fiber gratings, the sensor's measurement location is monitored for temperature. This invention utilizes a chirped fiber grating-FP sensor to perform real-time detection of the wear condition of sliding bearings in a ship's propulsion system, enabling health monitoring of the bearings and preventing major accidents caused by bearing failure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a single-mode optical fiber core.

[0020] Figure 2 This is a schematic diagram of the detection device of the present invention;

[0021] Figure 3 This is a schematic diagram of a bearing wear detection sensor.

[0022] Figure 4 The reflection spectrum of a sliding bearing wear detection sensor based on a chirped fiber Bragg grating (FP);

[0023] Figure 5 The diagram shows the changes in the reflection spectrum of the sliding bearing wear detection sensor. (a) shows the change in the reflection spectrum with temperature; (b) shows the change in the reflection spectrum with wear amount; and (c) is a magnified view of the number of interference fringes in (b).

[0024] In the diagram: 1-Bearing wear detection sensor; 2-Four-channel scanning laser; 3-Signal demodulation system; 4-Armored housing; 5-Salon bolt; 6-Single-mode optical fiber with engraved fiber grating; 7-Brag fiber grating engraved inside the fiber core; 8-First chirped fiber grating; 9-Second chirped fiber grating. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0026] This invention discloses a single-mode optical fiber for measuring bearing wear. It mainly utilizes the temperature sensitivity of the center wavelength of a Bragg fiber grating and the relationship between the number of FP cavity interference fringes and the grating length of a chirped fiber grating Fabry-Perot cavity to achieve high-precision measurement of temperature and bearing wear.

[0027] Specifically, such as Figure 1 The single-mode fiber used in this invention for bearing wear measurement has a first chirped fiber grating 8 and a second chirped fiber grating 9 etched inside to form an FP cavity, so that signals of different wavelengths are reflected at different positions along the chirped fiber gratings, thereby causing the wavelengths to be reflected and resonate to form FP interference fringes.

[0028] One method is to use a phase mask to record the image inside a single-mode fiber.

[0029] The first chirped fiber grating 8 and the second chirped fiber grating 9 have the same parameters. To ensure that the free spectral range of the interference fringes is consistent, they need to be cascaded in the same chirped direction, that is, with the same positive chirped coefficient or the same negative chirped coefficient. In use, the end of the first chirped fiber grating 8 is the light source signal input end, and the end of the second chirped fiber grating 9 is the light source signal output end; or the end of the second chirped fiber grating 9 is the light source signal input end, and the end of the first chirped fiber grating 8 is the light source signal output end.

[0030] The parameters of the first chirped fiber grating 8 and the second chirped fiber grating 9, including grating length, spacing, and chirp coefficient, can be selected and set according to the resolution of the scanning laser, with the goal of clearly displaying complete basic fringes. It should be noted that, to ensure the wear measurement range, the grating length or spacing should not be reduced excessively.

[0031] In one embodiment, the first chirped fiber grating and the second chirped fiber grating are spaced 1 mm apart, and their center wavelengths can be set to 1550 nm, the chirp factor is 10 nm / cm, and the grating length is 7 mm. The resulting FP cavity has a free spectral range of 100 pm.

[0032] To further optimize the above technical solution, in this invention, when the first chirped fiber grating 8 is the light source signal input end and the second chirped fiber grating 9 is the light source signal output end, the other end of the first chirped fiber grating 8 is engraved with a Bragg fiber grating 7, that is, the Bragg fiber grating 7 is always located on the side closer to the light source. To avoid overlap between the spectrum of the chirped fiber grating FP and the spectrum of the Bragg fiber grating, the center wavelength of the Bragg fiber grating should avoid this range. Furthermore, to ensure more accurate temperature measurement of the wear location by the Bragg fiber grating, it should be as close as possible to the wear location, and the grating length and spacing should be as small as possible.

[0033] In this embodiment, the Bragg fiber grating 7 and the first chirped fiber grating 8 are spaced 1 mm apart, and their center wavelength is set to 1520 nm, with a grating length of 5 mm. Example 2

[0034] To facilitate understanding of the use of the single-mode optical fiber of this invention by those skilled in the art, this application further discloses a detection device for measuring bearing wear, such as... Figure 2 As shown,

[0035] The device includes a bearing wear detection sensor, a scanning laser, and a signal demodulation system connected in sequence. In one embodiment, the bearing wear detection sensor 1 is connected to the four-channel scanning laser 2 via an optical fiber patch cord, and the signal demodulation system 3 is connected to the four-channel scanning laser 2 via a data line to receive and process the output signal from the scanning laser 2.

[0036] Bearing wear detection sensor, such as Figure 3 This includes the Sailon bolt 5 and the armored housing 4, used to encapsulate and solidify the single-mode optical fiber 6, structurally ensuring protection against temperature and stress changes during the optical fiber isolation installation process. It also ensures that the encapsulation structure wears synchronously with the bearing.

[0037] The single-mode optical fiber used for bearing wear measurement, as described above, is embedded inside the Sailon bolt. Specifically, the fiber optic cable with the Bragg fiber grating 7 as the incident end and the chirped fiber grating 9 as the output end is inserted into the Sailon bolt 5 and bonded using 353ND fiber adhesive. During bonding, the device needs to be heated on a heating table at 80°C for 24 hours. Finally, the cured optical fiber is installed into the armored housing 4, completing the fabrication of the bearing wear detection sensor 1.

[0038] In one embodiment, the Sailon bolt is made of Sailon material and has a through hole for placing optical fiber; preferably, the Sailon bolt is sized as follows: the external thread is M20 and the thread length is 30mm to facilitate connection with the armor shell, and the internal through hole is M3.5.

[0039] The armored outer shell serves to resist tension, compression, and bending, and is used to fix the Sailong bolts and fiber optic patch cords, as well as to protect the internal optical fibers.

[0040] The bearing wear detection sensor of this invention wears synchronously with the sliding bearing at its end, and is used to simultaneously detect the wear amount and temperature of the sliding bearing.

[0041] The scanning laser in this application is a four-channel scanning laser, used to simultaneously measure wear at multiple points on the bearing; at the same time, the scanning channels of the scanning laser are equipped with switches to enable single-channel measurement at different positions.

[0042] In one embodiment, the output light source of the scanning laser is broadband light with a resolution of 20 pm.

[0043] Furthermore, the signal demodulation system 3 demodulates the spectrum acquired from the four-channel scanning laser to obtain the number of interference fringes of the chirped fiber grating-FP cavity and the center wavelength offset of the Bragg fiber grating, thereby achieving high-precision demodulation of temperature and center wavelength.

[0044] In one embodiment, the signal demodulation system 3 is completed by a LabVIEW program on a PC. It demodulates the spectrum acquired from the four-channel scanning laser 2 to obtain the wear amount and temperature parameters, and sets a warning value to promptly remind the user to replace the sliding bearing.

[0045] Among them, the original reflection spectrum curve of the sensor is as follows: Figure 4 As shown. The demodulation of the bearing wear detection sensor is as follows. Figure 5 As shown, according toFigure 5 (a) The temperature at which the fiber Bragg grating wears out can be determined by the offset of its center wavelength. Figure 5 (b) When calculating the number of interference fringes, the temperature can be considered known, according to Figure 5 (b) The number of interference fringes at each wear time can be obtained. Figure 5 (c) is Figure 5 (b) is a magnified view of the number of interference fringes. The wear of the bearing is calculated based on the linear relationship between the number of interference fringes and the length of the grating area.

[0046] The chirped fiber grating-FP formed by this invention has extremely fine interference fringes, with 9 interference fringes per nm in the spectral range at a resolution of 20 pm. The accuracy can reach 0.03 mm within the effective spectral width of 20 nm. The number of fringes has a linear relationship with the grating length of the chirped fiber grating. As the sensor wears, the grating length decreases, and the number of interference fringes also decreases. Figure 5 As shown in (b), when the grid length is 4 mm, the number of corresponding fringes is the smallest. Based on the linear relationship between the two, the wear amount can be demodulated using the interference fringe counting method.

[0047] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single-mode optical fiber for measuring bearing wear, characterized in that, The internal space is etched with a first chirped fiber grating and a second chirped fiber grating to form an FP cavity, allowing signals of different wavelengths to be reflected at different positions along the chirped fiber gratings, thereby causing the wavelengths to be reflected and resonate to form FP interference fringes; the first chirped fiber grating and the second chirped fiber grating have the same parameters and are cascaded in the same chirping direction, the parameters including grating length, chirping coefficient and chirping direction, the first chirped fiber grating end is the light source signal input end and the second chirped fiber grating end is the light source signal output end; or the second chirped fiber grating end is the light source signal input end and the first chirped fiber grating end is the light source signal output end.

2. The single-mode optical fiber for bearing wear measurement according to claim 1, characterized in that, The other end of the first / second chirped fiber grating is also engraved with a Bragg fiber grating, and the Bragg fiber grating is located on the side closer to the light source.

3. A detection device for measuring bearing wear, characterized in that, It includes a bearing wear detection sensor, a scanning laser, and a signal demodulation system connected in sequence. The bearing wear detection sensor includes a ferrule bolt and an armored housing. The ferrule bolt is embedded with a single-mode optical fiber for bearing wear measurement as described in any one of claims 1-2. The armored housing is used to fix the ferrule bolt to the transmission optical fiber. The scanning laser is connected to the bearing wear detection sensor via the transmission fiber optic jumper. The scanning laser is a four-channel scanning laser, used to simultaneously measure wear at multiple points on the bearing. The signal demodulation system utilizes the linear relationship between the number of interference fringes and the grating length of the chirped fiber grating (FP) to perform high-precision demodulation of the wear amount of the sliding bearing, thereby completing the measurement of the wear amount of the sliding bearing.

4. The detection device for measuring bearing wear according to claim 3, characterized in that, The output light source of the scanning laser is broadband light with a resolution of 20 pm.

5. The detection device for measuring bearing wear according to claim 3, characterized in that, The parameters and spacing of the first chirped fiber grating and the second chirped fiber grating are determined based on the resolution of the scanning laser.

6. The detection device for measuring bearing wear according to claim 3, characterized in that, The scanning channel of the scanning laser is equipped with a switch to enable single-channel measurement at different positions.

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