Ultrasonic measurement method and system for thickness of lubricating oil film on guide surface of aircraft bearing retainer

Abstract

The invention discloses an aircraft bearing retainer guide surface lubricating oil film thickness ultrasonic measurement method and system, and belongs to the technical field of bearing lubricating oil film thickness measurement. The invention aims to solve the problem that the existing method cannot accurately measure the thickness of the aircraft bearing retainer guide surface lubricating oil film. Comprising the following steps: transmitting ultrasonic waves to a bearing retainer guide surface through an ultrasonic transducer; initial reference signals and measurement signals are collected for linear frequency modulation Z transformation, and a retainer guide surface transfer function is obtained; obtaining a mapping relation between a lagging phase of the retainer coating and a transfer function by combining a multi-layer medium structure ultrasonic transfer model; setting an estimation range of the oil film thickness; on the basis of the mapping relation, the lagging phase of the cage coating corresponding to the oil film thickness estimation value in the estimation range is calculated; and linear fitting is carried out on all the cage coating lagging phases, and an oil film thickness estimation value corresponding to a minimum fitting error value is extracted as a final oil film thickness measurement value. The method is used for oil film thickness measurement.

Description

Technical Field

[0001] The invention relates to an ultrasonic measurement method and system for the thickness of lubricating oil film on a 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 aircraft engines, and their good operating condition is the key to the safe operation of the entire mechanical equipment. When the bearing is in normal working conditions, 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 can easily cause major faults such as cage breakage. Therefore, real-time monitoring of the lubrication status of the cage guide surface is of great significance to ensure the life and reliability of aircraft bearings.

[0003] At present, the lubrication status of aviation bearing cages is mainly monitored by temperature, vibration and other parameters. When the cage fails to be lubricated, the temperature and vibration of the bearing will change significantly. These changing trends can reflect the degradation process of the bearing cage lubrication status to a certain extent, but early prediction of lubrication failure is more difficult. The thickness of the lubricating oil film is the core criterion for the lubrication status of the bearing cage guide surface. The real-time measurement of the oil film thickness can accurately determine the lubrication status of the cage. Among the many oil film thickness measurement methods, the ultrasonic measurement method does not require electromagnetic shielding or visualization of the bearing, and can overcome the limitations of traditional electrical and optical measurement methods. It has been widely used in the field of lubrication status monitoring.

[0004] In aviation bearings, in order to improve the lubrication performance of the cage guide surface, a thinner metal coating is usually prepared on the cage surface. Since the reflected echoes on both sides of the coating interface will be superimposed, the conventional three-layer structure ultrasonic model cannot be used to measure the oil film thickness. At present, the ultrasonic methods for measuring the oil film thickness of the four-layer structure include the ratio method, the echo separation method and the continuous model method. Among them, the ratio method requires the thick coating specimen to be processed in advance for signal correction, which increases the test cost, and there is a certain error in the correction process. The echo separation method uses a signal processing algorithm to eliminate the influence of the substrate-coating interface reflection echo, but when the coating is very thin, the interface echo signals on both sides of the coating overlap seriously, and the oil film thickness measurement accuracy is limited. The continuous model method calculates the oil film thickness based on the impedance recursion relationship, but it is necessary to obtain the coating thickness information in advance. For bearings in service, since the cage and the ring will inevitably contact, the cage surface coating will continue to wear, and the transient thickness information of the coating cannot be obtained in real time, so the application of the continuous model method is more difficult.

[0005] In summary, the above-mentioned ultrasonic methods all have certain limitations, and the accurate measurement of the lubricating oil film thickness on the guide surface of the aviation bearing cage is still a technical bottleneck that needs to be broken through. Summary of the invention

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

[0007] The present invention provides an ultrasonic measurement method for the thickness of lubricating oil film on the guide surface of an aviation bearing cage, comprising:

[0008] The ultrasonic transducer is arranged on the aviation bearing ring to emit ultrasonic waves to the guide surface of the bearing cage;

[0009] Before the aviation bearing is started, the reflection signal of the aviation bearing ring-air interface is collected as the initial reference signal; during the operation of the aviation bearing, the reflection signal of the bearing cage guide surface is collected as the measurement signal;

[0010] Performing a linear frequency modulation Z transform on the initial reference signal and the measurement signal to obtain a cage guide surface transfer function; and then combining a multi-layer dielectric structure ultrasonic transmission model to obtain a mapping relationship between the cage coating hysteresis phase and the cage guide surface transfer function;

[0011] According to the operating conditions of the aviation bearing, an estimated range of the oil film thickness between the aviation bearing ring and the cage coating is set; and based on the mapping relationship, the cage coating hysteresis phase corresponding to different oil film thickness estimation values ​​within the estimated range is calculated;

[0012] Linear fitting is performed on the hysteresis phases of all cage coatings, and the estimated value of oil film thickness corresponding to the minimum fitting error is extracted as the final measured value of oil film thickness.

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

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

[0015]

[0016] Where R is the cage guide surface transfer function, R 12 is the reflection coefficient of ultrasonic wave at the aviation bearing ring-oil film interface, R 23 is the reflection coefficient of the oil film-cage coating interface, R 34is 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 the ultrasonic wave in the lubricating oil film, and Δβ is the lag phase of the cage coating.

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

[0018]

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

[0020]

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

[0022] The pulse transceiver is used to transmit ultrasonic pulses and receive initial reference signals and measurement signals;

[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 measurement signal received by the pulse transceiver and upload them to the host computer;

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

[0026] Beneficial effects of the present invention: The present invention fully considers the influence of the cage coating on the ultrasonic propagation process, and realizes accurate measurement of the lubricating oil film thickness on the guide surface of the aviation bearing cage through the mapping relationship between the guide surface transfer function and the coating lag phase. Compared with the existing methods, the present invention does not need to process the thick coating test piece in advance for signal correction, does not need to use a more complex signal processing algorithm to eliminate the influence of the substrate-coating interface echo, and can realize accurate measurement of the oil film thickness when the coating thickness is unknown, which reduces the test cost and improves the test accuracy. It can meet the online monitoring requirements of the lubrication status of the guide surface of the aviation bearing cage and has important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 11 is a schematic diagram of the structure of the ultrasonic measurement system for the thickness of the lubricating oil film on the guide surface of the aviation bearing cage of 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 is a schematic diagram of the time domain waveforms of the initial reference signal and the reflected signal from the guiding surface;

[0029] Figure 3 is a schematic diagram of the cage coating hysteresis phase corresponding to different oil film thickness estimates;

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

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

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0035] Specific implementation method 1. Combination Figure 1 As shown, this embodiment provides an ultrasonic measurement method for the lubricating oil film thickness on the guide surface of an aviation bearing cage, comprising:

[0036] The ultrasonic transducer is arranged on the aviation bearing ring to emit ultrasonic waves to the guide surface of the bearing cage;

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

[0038] Performing a linear frequency modulation Z transform on the initial reference signal and the measurement signal to obtain a cage guide surface transfer function; and then combining a multi-layer dielectric structure ultrasonic transmission model to obtain a mapping relationship between the cage coating hysteresis phase and the cage guide surface transfer function;

[0039] According to the operating conditions of the aviation bearing, an estimated range of the oil film thickness between the aviation bearing ring and the cage coating is set; and based on the mapping relationship, the cage coating hysteresis phase corresponding to different oil film thickness estimation values ​​within the estimated range is calculated;

[0040] Linear fitting is performed on the hysteresis phases of all cage coatings, and the estimated value of oil film thickness corresponding to the minimum fitting error is extracted as the final measured value of oil film thickness.

[0041] Furthermore, the ultrasonic wave is obtained by emitting ultrasonic pulses through a pulse transceiver to excite an ultrasonic transducer.

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

[0043]

[0044] Where R is the cage guide surface transfer function, R 12 is the reflection coefficient of ultrasonic wave at the aviation bearing ring-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 frequency, d2 is the oil film thickness, c2 is the sound velocity of the ultrasonic wave in the lubricating oil film, and Δβ is the lag phase of the cage coating.

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

[0046]

[0047] The above formula is further transformed to obtain the mapping relationship between the cage coating lag phase and the cage guide surface transfer function:

[0048]

[0049] Based on the above mapping relationship, the coating hysteresis phase corresponding to different oil film thicknesses can be calculated. Since the coating hysteresis phase Δβ is linearly related to the ultrasonic frequency, the smaller the deviation between the estimated value and the actual value of the oil film thickness, the smaller the linear fitting error of the coating hysteresis phase. Using this feature, the optimal estimation of the oil film thickness can be achieved.

[0050] In actual measurement, firstly, a series of estimated values ​​of oil film thickness are set according to the operating conditions of the bearing. Then, according to the mapping relationship between the coating hysteresis phase and the guide surface transfer function, the coating hysteresis phase corresponding to different estimated values ​​of oil film thickness is calculated and linear fitting is performed. By extracting the oil film thickness with the minimum fitting error, the oil film thickness of the guide surface of the aviation bearing cage can be accurately measured.

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

[0052] The pulse transceiver is used to transmit ultrasonic pulses and receive initial reference signals and measurement signals;

[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 stimulated by the excitation pulse, the ultrasonic transducer emits ultrasonic waves of a certain frequency range to the guide surface of the bearing cage, and transmits the received reflected echo from the guide surface to the pulse transceiver;

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

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

[0056] The effect of the present invention is verified by specific experiments below:

[0057] Establish as Figure 1 The guide surface lubricating oil film thickness calibration platform and ultrasonic measurement system are shown 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 to the guide surface. The incident wave will generate a reflected wave at the interface between different media. After being received by the ultrasonic transducer, the reflected wave is limited, filtered, and amplified by the pulse transceiver, and recorded in real time by a high-speed oscilloscope. During measurement, the reflected signal of the ultrasonic wave at the bearing ring-air interface is first recorded as the initial reference signal. After obtaining the initial reference signal, lubricating oil is added between the bearing ring and the retainer coating to form a lubricating oil film between the two. The oil film thickness is adjusted by changing the distance between the ring and the retainer coating, and the reflected signal of the guide surface before the coating wears is recorded.

[0059] Figure 2 is the time domain waveform of the initial reference signal and the reflected signal of the guide surface. The upper computer performs a linear frequency modulation Z transform on it to obtain the transfer function at the guide surface. According to the mapping relationship between the transfer function of the guide surface and the coating lag phase, the coating lag phase corresponding to different oil film thickness estimation values ​​is further calculated, such as Figure 3 Then, a linear fitting is performed on the coating hysteresis phase corresponding to different oil film thickness estimation values ​​to obtain a graph showing the variation of the linear fitting error with the oil film thickness estimation value, as shown in Figure 4 The estimated value of the oil film thickness corresponding to the minimum fitting error is extracted as the oil film thickness measurement result before the coating wears.

[0060] After completing the above steps, the cage coating is polished to simulate the cage coating wear when the bearing is in service. The same steps are used to record and process the guide surface reflection signal after the coating is worn, and the oil film thickness measurement result after the coating is worn is obtained. Figure 5 The figure is a comparison of the measured oil film thickness and the set oil film thickness before and after coating wear. It can be seen that regardless of whether the cage coating is worn, the method of the present invention can accurately measure the oil film thickness of the bearing cage guide surface, effectively overcome the limitations of the existing ultrasonic measurement method in the field of aviation bearing cage guide surface lubrication status monitoring, meet the requirements of online monitoring of the bearing cage lubrication status, and fully demonstrate the advantages of the present invention.

[0061] Although the present invention is 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. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. An ultrasonic measurement method for the thickness of lubricating oil film on the guide surface of an aviation bearing cage, characterized in that include, The ultrasonic transducer is arranged on the aviation bearing ring to emit ultrasonic waves to the guide surface of the bearing cage; Before the aviation bearing is started, the reflection signal of the aviation bearing ring-air interface is collected as the initial reference signal; during the operation of the aviation bearing, the reflection signal of the bearing cage guide surface is collected as the measurement signal; Performing a linear frequency modulation Z transform on the initial reference signal and the measurement signal to obtain a cage guide surface transfer function; and then combining a multi-layer dielectric structure ultrasonic transmission model to obtain a mapping relationship between the cage coating hysteresis phase and the cage guide surface transfer function; According to the operating conditions of the aviation bearing, an estimated range of the oil film thickness between the aviation bearing ring and the cage coating is set; and based on the mapping relationship, the cage coating hysteresis phase corresponding to different oil film thickness estimation values ​​within the estimated range is calculated; Linear fitting is performed on the hysteresis phases of all cage coatings, and the estimated value of oil film thickness corresponding to the minimum fitting error is extracted as the final measured value of oil film thickness.

2. The ultrasonic measurement method for lubricating oil film thickness on the guide surface of an aviation bearing cage according to claim 1 is characterized in that: The ultrasonic wave is obtained by emitting ultrasonic pulses by a pulse transceiver to excite an ultrasonic transducer.

3. The ultrasonic measurement method for lubricating oil film thickness on the guide surface of an aviation bearing cage according to claim 1, characterized in that: The transfer function of the cage guide surface based on the ultrasonic transmission model of the multi-layer dielectric structure is expressed as: Where R is the cage guide surface transfer function, R 12 is the reflection coefficient of ultrasonic wave at the aviation bearing ring-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 frequency, d2 is the oil film thickness, c2 is the sound velocity of the ultrasonic wave in the lubricating oil film, and Δβ is the lag phase of the cage coating.

4. The ultrasonic measurement method for lubricating oil film thickness on the guide surface of an aviation bearing cage according to claim 3 is characterized in that: Transform the transfer function of the cage guide surface to obtain: The above formula is further transformed to obtain the mapping relationship between the cage coating lag phase and the cage guide surface transfer function:

5. An ultrasonic measurement system for lubricating oil film thickness on the guide surface of an aircraft bearing cage, used to implement the ultrasonic measurement method for lubricating oil film thickness on the guide surface of an aircraft bearing cage according to any one of claims 1 to 4, characterized in that: Including pulse transceiver, ultrasonic transducer, high-speed oscilloscope and host computer; The pulse transceiver is used to transmit ultrasonic pulses and receive initial reference signals and measurement signals; 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; The high-speed oscilloscope is used to collect the initial reference signal and measurement signal received by the pulse transceiver and upload them to the host computer; The host computer is used to process the initial reference signal and the measurement signal in real time, and calculate the final measurement value of the oil film thickness through the mapping relationship between the cage coating lag phase and the cage guide surface transfer function.

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