Ultrasonic measurement method and system for lubricating oil film thickness of the guiding surface of an aviation bearing cage

Abstract

An ultrasonic measurement method and system for the lubricating oil film thickness of the guide surface of an aviation bearing cage, belonging to the technical field of bearing lubricating oil film thickness measurement. The present invention aims at the problem that the existing methods cannot accurately measure the lubricating oil film thickness of the guide surface of an aviation bearing cage. It includes emitting ultrasonic waves to the guide surface of the bearing cage through an ultrasonic transducer; collecting the initial reference signal and the measurement signal to perform a chirp Z-transform to obtain the transfer function of the cage guide surface; combining the ultrasonic transfer model of the multi-layer dielectric structure to obtain the mapping relationship between the cage coating lag phase and the transfer function; setting the estimation range of the oil film thickness; and then based on the mapping relationship, calculating the cage coating lag phase corresponding to the estimated value of the oil film thickness within the estimation range; performing linear fitting on all the cage coating lag phases, and extracting the estimated value of the oil film thickness corresponding to the minimum fitting error as the final measured value of the oil film thickness. The present invention is used for measuring the oil film thickness.

Description

Technical Field

[0001] The present invention relates to an ultrasonic measurement method and system for the lubricating oil film thickness of the guide surface of an aviation bearing cage, and belongs to the technical field of bearing lubricating oil film thickness measurement. Background Art

[0002] Rolling bearings are key components of aero-engines, and their good operating state is crucial for the safe operation of the entire mechanical equipment. When the bearing is in a conventional working condition, the cage and the ring are separated by a lubricating oil film. However, when the bearing is in harsh working conditions such as high speed, heavy load, and rapid speed change, the dynamic contact behavior between the cage and the ring is extremely complex, and it is difficult to form a complete lubricating oil film between the contact surfaces, which is likely to cause major failures such as cage fracture. Therefore, carrying out real-time monitoring of the lubrication state of the cage guide surface is of great significance for ensuring the life and reliability of aviation bearings.

[0003] Currently, the lubrication state of the aviation bearing cage is mainly monitored through parameters such as temperature and vibration. When lubrication failure occurs in the cage, the temperature and vibration of the bearing will change significantly accordingly. These change trends can reflect the degradation process of the lubrication state of the bearing cage to a certain extent, but it is difficult to predict the early stage of lubrication failure. The lubricating oil film thickness is the core criterion for the lubrication state of the bearing cage guide surface. By real-time measuring the oil film thickness, the lubrication state of the cage can be accurately judged. Among many oil film thickness measurement methods, the ultrasonic measurement method does not require electromagnetic shielding or visualization transformation of the bearing, and can overcome the limitations of traditional electrical measurement methods and optical measurement methods, and has been widely used in the field of lubrication state monitoring.

[0004] In aviation bearings, in order to improve the lubrication performance of the cage guide surface, a thin metal coating is usually prepared on the cage surface. Since the reflected echoes at both interfaces of the coating will be superimposed, the conventional three-layer structure ultrasonic model cannot be used to measure the oil film thickness. Currently, ultrasonic methods for measuring the oil film thickness of a four-layer structure include the ratio method, the echo separation method, and the continuous model method. Among them, the ratio method requires thick coating specimens to be processed in advance for signal correction, which increases the test cost, and there are certain errors in the correction process. The echo separation method uses a signal processing algorithm to eliminate the influence of the matrix-coating interface reflected echo. However, when the coating is very thin, the echo signals at both interfaces of the coating seriously overlap, and the measurement accuracy of the oil film thickness is limited. The continuous model method calculates the oil film thickness based on the impedance recurrence relationship, but the thickness information of the coating needs to be obtained in advance. For bearings in service, due to the inevitable contact between the cage and the ring, the coating on the cage surface will continuously wear, and it is impossible to obtain the transient thickness information of the coating in real time. Therefore, the application of the continuous model method is relatively difficult.

[0005] In summary, the above ultrasonic methods all have certain limitations, and the accurate measurement of the lubricating oil film thickness on the guiding surface of the aviation bearing cage remains a technical bottleneck that urgently needs to be broken through. Summary of the Invention

[0006] Aiming at the problem that the existing methods cannot accurately measure the lubricating oil film thickness on the guiding surface of the aviation bearing cage, the present invention provides an ultrasonic measurement method and system for the lubricating oil film thickness on the guiding surface of the aviation bearing cage.

[0007] An ultrasonic measurement method for the lubricating oil film thickness on the guiding surface of the aviation bearing cage according to the present invention includes:

[0008] Arrange an ultrasonic transducer on the aviation bearing raceway and emit ultrasonic waves towards the guiding surface of the bearing cage;

[0009] Before the aviation bearing starts, collect the reflection signal of the aviation bearing raceway-air interface as the initial reference signal; during the operation of the aviation bearing, collect the reflection signal of the guiding surface of the bearing cage as the measurement signal;

[0010] Perform a chirp Z-transform on the initial reference signal and the measurement signal to obtain the transfer function of the cage guiding surface; then combine the ultrasonic transfer model of the multi-layer medium structure to obtain the mapping relationship between the lag phase of the cage coating and the transfer function of the cage guiding surface;

[0011] According to the operating conditions of the aviation bearing, set the estimated range of the oil film thickness between the aviation bearing raceway and the cage coating; then based on the mapping relationship, calculate the lag phase of the cage coating corresponding to different oil film thickness estimated values within the estimated range;

[0012] Perform a linear fitting on all the lag phases of the cage coating, and extract the oil film thickness estimated value corresponding to the minimum fitting error as the final measured value of the oil film thickness.

[0013] According to the ultrasonic measurement method for the lubricating oil film thickness on the guiding surface of the aviation bearing cage of the present invention, the ultrasonic wave is obtained by exciting the ultrasonic transducer through a pulse transceiver to emit ultrasonic pulses.

[0014] According to the ultrasonic measurement method for the lubricating oil film thickness on the guiding surface of the aviation bearing cage of the present invention, the transfer function of the cage guiding surface based on the ultrasonic transfer model of the multi-layer medium structure is expressed as:

[0015]

[0016] Where R is the transfer function of the cage guiding surface, R 12 is the reflection coefficient of the ultrasonic wave at the aviation bearing raceway-oil film interface, R 23 is the reflection coefficient of the oil film-cage coating interface, R 34For the reflection coefficient of the cage coating - cage interface, f is the ultrasonic frequency, d2 is the oil film thickness, c2 is the sound velocity of ultrasonic waves in the lubricating oil film, and Δβ is the lag phase of the cage coating.

[0017] According to the ultrasonic measurement method for the lubricating oil film thickness of the cage guiding surface of the aviation bearing of the present invention, the transfer function of the cage guiding surface is transformed to obtain:

[0018]

[0019] The above formula is further transformed to obtain the mapping relationship between the lag phase of the cage coating and the transfer function of the cage guiding surface:

[0020]

[0021] The present invention also provides an ultrasonic measurement system for the lubricating oil film thickness of the cage guiding surface of an aviation bearing, which is used to implement the ultrasonic measurement method for the lubricating oil film thickness of the cage guiding surface of the aviation bearing, and includes a pulse transceiver, an ultrasonic transducer, a high - speed oscilloscope, and a host computer;

[0022] Among them, the pulse transceiver is used to transmit ultrasonic pulses and receive the initial reference signal and the measurement signal;

[0023] The ultrasonic transducer is used to generate ultrasonic waves based on the received ultrasonic pulses and transmit the initial reference signal and the measurement signal to the pulse transceiver;

[0024] The high - speed oscilloscope is used to collect the initial reference signal and the measurement signal received by the pulse transceiver and upload them to the host computer;

[0025] The host computer is used to perform real - time processing on the initial reference signal and the measurement signal, and calculate the final measured value of the oil film thickness through the mapping relationship between the lag phase of the cage coating and the transfer function of the cage guiding surface.

[0026] The beneficial effects of the present invention: The present invention fully considers the influence law of the cage coating on the ultrasonic propagation process, and realizes the accurate measurement of the lubricating oil film thickness of the cage guiding surface of the aviation bearing through the mapping relationship between the transfer function of the guiding surface and the lag phase of the coating. Compared with the existing methods, the present invention does not need to process thick - coating specimens in advance for signal correction, does not need to use relatively complex signal - processing algorithms to eliminate the influence of the matrix - coating interface echo, and can accurately measure the oil film thickness when the coating thickness is unknown, reducing the test cost, improving the test accuracy, and being able to meet the on - line monitoring requirements of the lubrication state of the cage guiding surface of the aviation bearing, and has important engineering application value. Description of the Drawings

[0027] Figure 1It is a schematic structural diagram of the ultrasonic measurement system for the lubricating oil film thickness of the guide surface of the cage of the aviation bearing described in the present invention; in the figure, 1 is an ultrasonic transducer, 2 is a pulse transceiver, 3 is a high-speed oscilloscope, 4 is a host computer, 5 is an aviation bearing ring, 6 is a lubricating oil film, 7 is a cage coating, and 8 is a bearing cage;

[0028] Figure 2 It is a schematic diagram of the time-domain waveforms of the initial reference signal and the reflection signal of the guide surface;

[0029] Figure 3 It is a schematic diagram of the lag phase of the cage coating corresponding to different estimated oil film thicknesses;

[0030] Figure 4 It is a schematic diagram of the change of the linear fitting error of the lag phase of the cage coating with the estimated oil film thickness;

[0031] Figure 5 It is a comparison chart of the final measured value (actual measured oil film thickness) of the oil film thickness obtained by the method of the present invention before and after the wear of the cage coating and the actually set oil film thickness. Specific embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0033] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0034] Next, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments, but it is not a limitation of the present invention.

[0035] Specific embodiment one, combination Figure 1 As shown, this embodiment provides an ultrasonic measurement method for the lubricating oil film thickness of the guide surface of the cage of an aviation bearing, including,

[0036] Arrange the ultrasonic transducer on the aviation bearing ring and emit ultrasonic waves to the guide surface of the bearing cage;

[0037] Before the aviation bearing starts, collect the reflection signal of the aviation bearing ring-air interface as the initial reference signal; during the operation of the aviation bearing, collect the reflection signal of the guide surface of the bearing cage as the measurement signal;

[0038] Perform a chirp Z - transform on the initial reference signal and the measurement signal to obtain the cage guiding surface transfer function; then combine it with the ultrasonic transfer model of the multi - layer dielectric structure to obtain the mapping relationship between the cage coating lag phase and the cage guiding surface transfer function;

[0039] According to the operating conditions of the aviation bearing, set the estimated range of the oil film thickness between the aviation bearing raceway and the cage coating; then based on the mapping relationship, calculate the cage coating lag phase corresponding to different oil film thickness estimated values within the estimated range;

[0040] Perform a linear fitting on all cage coating lag phases, and extract the oil film thickness estimated value corresponding to the minimum fitting error as the final measured value of the oil film thickness.

[0041] Furthermore, the ultrasonic wave is obtained by exciting an ultrasonic transducer by transmitting an ultrasonic pulse through a pulse transceiver.

[0042] In this embodiment, when the ultrasonic wave propagates in the aviation bearing, reflection and transmission occur at the interface of different media. According to the ultrasonic transfer model of the multi - layer dielectric structure, when the incident wave has a unit amplitude, the cage guiding surface transfer function based on the ultrasonic transfer model of the multi - layer dielectric structure is expressed as:

[0043]

[0044] In the formula, R is the cage guiding surface transfer function, R 12 is the reflection coefficient of the ultrasonic wave at the aviation bearing raceway - oil film interface, R 23 is the reflection coefficient of the oil film - cage coating interface, R 34 is the reflection coefficient of the cage coating - cage interface, f is the ultrasonic wave frequency, d2 is the oil film thickness, c2 is the sound speed of the ultrasonic wave in the lubricating oil film, and Δβ is the cage coating lag phase.

[0045] Transform the cage guiding surface transfer function to obtain:

[0046]

[0047] Further transform the above formula to obtain the mapping relationship between the cage coating lag phase and the cage guiding surface transfer function:

[0048]

[0049] Based on the above mapping relationship, the coating lag phase corresponding to different oil film thicknesses can be calculated. Since the coating lag phase Δβ has a linear relationship with the ultrasonic frequency, when the deviation between the estimated value and the actual value of the oil film thickness is smaller, the linear fitting error of the coating lag phase is smaller. Utilizing this characteristic, the optimal estimation of the oil film thickness can be achieved.

[0050] During actual measurement, a series of estimated values of the oil film thickness are first set according to the operating conditions of the bearing. Then, based on the mapping relationship between the coating lag phase and the transfer function of the guiding surface, the coating lag phases corresponding to different estimated values of the oil film thickness are calculated and linearly fitted. The oil film thickness when the fitting error is minimized is extracted, and thus the accurate measurement of the oil film thickness of the guiding surface of the aviation bearing cage can be achieved.

[0051] Specific Embodiment 2, in combination with Figure 1 As shown, this embodiment provides an ultrasonic measurement system for the lubricating oil film thickness of the guiding surface of an aviation bearing cage, which is used to implement the ultrasonic measurement method for the lubricating oil film thickness of the guiding surface of the aviation bearing cage described in Specific Embodiment 1, and includes a pulse transceiver, an ultrasonic transducer, a high-speed oscilloscope, and a host computer;

[0052] Among them, the pulse transceiver is used to transmit ultrasonic pulses and receive the initial reference signal and the measurement signal;

[0053] The ultrasonic transducer is used to generate ultrasonic waves based on the received ultrasonic pulses and transmit the initial reference signal and the measurement signal to the pulse transceiver; after being excited by the excitation pulse, the ultrasonic transducer emits ultrasonic waves within a certain frequency range to the guiding surface of the bearing cage and transmits the received reflected echo from the guiding surface to the pulse transceiver;

[0054] The high-speed oscilloscope is used to collect the initial reference signal and the measurement signal received by the pulse transceiver and upload them to the host computer;

[0055] The host computer is used to perform real-time processing on the initial reference signal and the measurement signal, and calculate the final measured value of the oil film thickness through the mapping relationship between the cage coating lag phase and the transfer function of the cage guiding surface.

[0056] The following verifies the effect of the present invention through specific experiments:

[0057] Establish a calibration platform for the lubricating oil film thickness of the guiding surface and an ultrasonic measurement system as shown in Figure 1 to verify the effectiveness of the present invention.

[0058] An excitation pulse is sent to the ultrasonic transducer through a pulse transceiver. After being excited, the ultrasonic transducer emits an incident wave with a certain frequency range towards the guiding surface. The incident wave will generate a reflected wave at the interface of different media. After the reflected wave is received by the ultrasonic transducer, it is limited, filtered, and amplified by the pulse transceiver, and is recorded in real time by a high-speed oscilloscope. During the measurement, first record the reflection signal of the ultrasonic wave at the bearing ring-air interface as the initial reference signal. After obtaining the initial reference signal, lubricating oil is added between the bearing ring and the cage coating to form a lubricating oil film therebetween. The thickness of the oil film is adjusted by changing the distance between the ring and the cage coating, and the reflection signal of the guiding surface before the coating wears is recorded.

[0059] Figure 2 is the time-domain waveform diagram of the initial reference signal and the reflection signal of the guiding surface. The linear frequency modulation Z-transform is performed on it by the upper computer to obtain the transfer function at the guiding surface. According to the mapping relationship between the transfer function of the guiding surface and the coating lag phase, the coating lag phases corresponding to different estimated oil film thickness values are further calculated, as Figure 3 shown. Subsequently, a linear fitting is performed on the coating lag phases corresponding to different estimated oil film thickness values to obtain a graph of the change of the linear fitting error with the estimated oil film thickness value, as Figure 4 shown. Extract the estimated oil film thickness value corresponding to the minimum fitting error as the measurement result of the oil film thickness before the coating wears.

[0060] After completing the above steps, the cage coating is polished to simulate the wear of the cage coating during the service of the bearing. The same steps are used to record and process the reflection signal of the guiding surface after the coating wears to obtain the measurement result of the oil film thickness after the coating wears. Figure 5 is a comparison graph of the measured oil film thickness before and after the coating wear and the set oil film thickness. It can be seen that regardless of whether the cage coating wears or not, the method of the present invention can accurately measure the oil film thickness of the bearing cage guiding surface, effectively overcomes the limitations of the existing ultrasonic measurement method in the field of monitoring the lubrication state of the bearing cage guiding surface of aviation bearings, meets the requirements of on-line monitoring of the lubrication state of the bearing cage, and fully reflects the advantages of the present invention.

[0061] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not deviate from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. An ultrasonic measurement method for the lubricating oil film thickness of the guiding surface of an aviation bearing cage, characterized in that including arranging an ultrasonic transducer on an aero-bearing raceway, and emitting ultrasonic waves to a cage guiding surface of the bearing before starting the aero-bearing, collecting a reflection signal of the aero-bearing raceway-air interface as an initial reference signal; during the operation of the aero-bearing, collecting a reflection signal of the cage guiding surface as a measurement signal performing a chirp Z-transform on the initial reference signal and the measurement signal to obtain a cage guiding surface transfer function; and then obtaining a mapping relationship between the cage coating lag phase and the cage guiding surface transfer function in combination with a multi-layered medium structure ultrasonic transmission model setting an estimation range of the oil film thickness between the aero-bearing raceway and the cage coating according to the operating conditions of the aero-bearing; and then calculating the cage coating lag phases corresponding to different oil film thickness estimation values within the estimation range based on the mapping relationship performing linear fitting on all the cage coating lag phases, and extracting the oil film thickness estimation value corresponding to the minimum fitting error as the final measured value of the oil film thickness The cage guiding surface transfer function based on the multi-layered medium structure ultrasonic transmission model is expressed as where R is the cage guiding surface transfer function, R 12 is the reflection coefficient of ultrasonic waves at the raceway - oil film interface of the aviation bearing, R 23 is the reflection coefficient of the oil film - cage coating interface, R 34 is the reflection coefficient of the cage coating - cage interface, f is the ultrasonic frequency, d2 is the oil film thickness, c2 is the sound velocity of ultrasonic waves in the lubricating oil film, and Δβ is the cage coating lag phase.

2. The ultrasonic measurement method for the lubricating oil film thickness of the guiding surface of the aviation bearing cage according to claim 1, wherein The ultrasonic waves are obtained by exciting the ultrasonic transducer by the pulse transceiver to emit ultrasonic pulses 3. The ultrasonic measurement method for the lubricating oil film thickness of the guiding surface of the aviation bearing cage according to claim 1, wherein Performing a transformation on the cage guiding surface transfer function, and obtaining Performing a further transformation on the above formula to obtain a mapping relationship between the cage coating lag phase and the cage guiding surface transfer function 4. An ultrasonic measurement system for the oil film thickness of a cage guiding surface of an aero-bearing, which is used to implement the ultrasonic measurement method for the oil film thickness of the cage guiding surface of an aero-bearing according to any one of claims 1 to 3, and is characterized in that it includes a pulse transceiver, an ultrasonic transducer, a high-speed oscilloscope and a host computer wherein the pulse transceiver is used to emit ultrasonic pulses and receive the initial reference signal and the measurement signal the ultrasonic transducer is used to generate ultrasonic waves based on the received ultrasonic pulses, and transfer the initial reference signal and the measurement signal to the pulse transceiver the high-speed oscilloscope is used to collect the initial reference signal and the measurement signal received by the pulse transceiver, and upload them to the host computer the host computer is used to perform real-time processing on the initial reference signal and the measurement signal, and calculate the final measured value of the oil film thickness through the mapping relationship between the cage coating lag phase and the cage guiding surface transfer function

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