Oil film thickness detection method, device, equipment and medium

Abstract

The invention provides an oil film thickness detection method, device and equipment and a medium. The method comprises the following steps: arranging an ultrasonic transducer near an oil film; a pulse transceiver is adopted to emit periodic pulses to excite an ultrasonic transducer, so that the ultrasonic transducer emits an ultrasonic signal with a preset frequency, when the thickness of an oil film is far smaller than the half-wavelength of ultrasonic waves, the oil film layer is equivalent to a light spring, and then a calculation model is designed to calculate the thickness of the oil film. The oil film thickness detection method provided by the invention adopts a non-contact method to measure and calculate the thickness of the oil film, has the advantages of no damage to the oil film, good repeatability, good environmental adaptability and the like, and can effectively overcome measurement errors caused by system errors, processing errors and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of lubrication state monitoring and oil film thickness measurement, and relates to an oil film thickness detection method, device, equipment and medium. Background Art

[0002] Mechanical components such as gears and bearings rely on the isolation of contact surfaces by lubricating oil films, and have a long service life when working normally. However, once the lubricating oil film fails, the two contact surfaces will contact and rub, followed by wear of the components. Therefore, the appropriate oil film thickness will have a great impact on the performance and service life of the friction machinery. The performance of the lubricating oil, the shape of the two contact surfaces and the operating state will affect the thickness of the lubricating oil film. The contact mode of the two surfaces is divided into surface contact (such as radial bearings and thrust bearings), line contact (such as gears) and point contact (such as rolling bearings). The oil film thickness of the hydrodynamic lubrication area under surface contact is generally in the range of 1um to 100um, while the oil film thickness of the elastohydrodynamic lubrication area under point contact and line contact is less than 1um. Regardless of the contact mode, the lubricating oil film must be thick enough to isolate the two surfaces, but too thick an oil film will increase the friction of the oil film and cause excessive pump force loss. Therefore, the oil film thickness will affect the quality of liquid lubrication, and the film thickness needs to be measured to understand the lubrication status of the mechanical equipment in real time.

[0003] There are many methods used to measure the oil film thickness, such as resistance method, capacitance method, optical method, etc. The resistance method and capacitance method require electrical isolation or surface-mounted electrodes, and the measurement results are very sensitive to surface roughness; and these two methods can generally only measure the oil film thickness above 1um. The optical method requires one of the two contact surfaces to be transparent or a transparent window to be set. The setting of the transparent window makes the optical measurement method temporarily unusable in the industry. The above methods are all invasive, and the bearings need to be damaged to varying degrees during measurement, so these methods cannot currently be used to measure the actual thickness of industrial bearing oil films. The emergence of non-invasive ultrasonic measurement methods provides a possibility to solve this problem. Its principle is to perform spectrum analysis on the reflected signal of the solid-liquid interface and obtain the oil film thickness by selecting appropriate signal processing methods such as resonance models. The ultrasonic method can measure a wide range of film thickness, from tens of nanometers to hundreds of millimeters, and is fully suitable for measuring the film thickness of industrial bearings.

[0004] With the advancement of electronic computer technology and high-sensitivity digital and other machine vision technologies, machine recognition and optical detection have become research hotspots. Under different oil film thicknesses, the images collected by the CCD camera are coupled with the oil film thickness values ​​obtained by ultrasonic film thickness measurement to obtain a standard image database of different oil film thicknesses. The actual oil film thickness is then obtained by an online CCD camera, matched with the standard image database, and then the difference is obtained to obtain a difference image, and the measured oil film thickness is determined by computer interpolation.

[0005] For the calibration of ultrasonic film thickness measurement equipment, some researchers use a gasket of specific thickness laid between two surfaces for calibration, while others use a groove of specific thickness machined on the upper surface of the test block for calibration. These calibration methods have the following disadvantages: (1) The oil film thickness is a fixed value during the calibration process, and ultrasonic probes with different frequency responses require different oil film thicknesses for calibration; (2) During the calibration process, it is impossible to determine whether there is still a gap between the two surfaces and the middle gasket; most importantly, the measurement results include systematic errors and processing errors. Summary of the invention

[0006] The purpose of the present invention is to provide an oil film thickness detection method, device, equipment and medium to address the defects of the prior art. The method regards the oil film as equivalent to a lightweight spring and adopts a non-contact method to measure and calculate the oil film thickness. It has the advantages of not destroying the oil film, good repeatability, good environmental adaptability, etc., and can effectively overcome the measurement errors caused by system errors and processing errors.

[0007] A first aspect of the present invention provides an oil film thickness detection method, comprising: The ultrasonic transducer is arranged near the oil film; a pulse transceiver is used to send periodic pulses to excite the ultrasonic transducer, so that the ultrasonic transducer sends an ultrasonic signal with a preset frequency; When the oil film thickness is much smaller than the half wavelength of the ultrasonic wave, the oil film layer is equivalent to a light spring, and the equivalent spring stiffness K of the oil film layer is expressed as: ; Where: B is the bulk modulus of the oil film; h is the thickness of the oil film; Calculate the reflection coefficient R(f) under the spring model:

[0008] ; Where: Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film; K is the equivalent spring stiffness of the oil film layer; ω is the angular frequency of the ultrasonic wave, ω = 2πf, f is the ultrasonic wave frequency; After conversion, the spring model oil film thickness h is calculated according to the following formula:

[0009] ; Where: ρ is the density of the lubricating medium; c is the sound velocity of the lubricating medium; Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film respectively.

[0010] Preferably, when the media on both sides of the oil film are air and cast iron respectively, the corresponding Z1=0.41 and Z3=41.50.

[0011] Preferably, it also includes: A CCD camera is used to collect images of different oil film thicknesses; The image collected by the CCD camera is coupled with the oil film thickness value obtained by measurement to obtain a standard image database of different oil film thicknesses; The actual oil film image is then obtained through an online CCD camera, matched with the standard image database, and then a difference image is obtained. The oil film thickness is then determined through computer interpolation.

[0012] According to a second aspect of the present invention, there is provided an apparatus for implementing an oil film thickness detection method as described in any one of the above items, comprising: an ultrasonic transducer, a CCD camera and a computer, wherein the ultrasonic transducer and the CCD camera are both connected to the computer, the ultrasonic transducer is used to emit an ultrasonic signal with a preset frequency, the computer stores a standard image database of different oil film thicknesses, the CCD camera is used to collect images and send them to the computer, after the computer obtains the actual oil film image, it matches it with the standard image database and performs subtraction to obtain a difference image, and then determines the oil film thickness through computer interpolation.

[0013] According to a third aspect of the present invention, there is provided an electronic device comprising a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor, and the processor is prompted by the machine-executable instructions to implement the steps of an oil film thickness detection method as described above.

[0014] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the oil film thickness detection method described in any one of the above items is implemented.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an oil film thickness detection method, which uses a non-contact method to measure and calculate the oil film thickness, has the advantages of not destroying the oil film, good repeatability, good environmental adaptability, etc., and can effectively overcome measurement errors caused by system errors and processing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the propagation of ultrasonic waves in the invention.

[0017] Figure 2 Graph showing acoustic parameters of different materials used in the present invention.

[0018] Figure 3 It is a structural schematic diagram of the present invention.

[0019] In the figure: 1. Ultrasonic transducer; 2. CCD camera; 3. Computer; a. Substrate; b. Oil film. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments. However, it should be understood that the drawings are only used for exemplary descriptions and cannot be understood as limitations on this patent; in order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted; the positional relationship described in the drawings is only used for exemplary descriptions and cannot be understood as limitations on this patent.

[0021] The thickness of the lubricating oil film between mechanical components is equivalent to the liquid layer between two solid media. When the sound wave propagates to the interface between the two different media, part of the energy will be reflected and the other part will be projected.

[0022] Ultrasonic wave propagation process Figure 1 As shown, the oil film b is attached to the substrate a. When the thickness of the oil film b is much smaller than the half wavelength of the ultrasonic wave, the intermediate oil film b can be regarded as a reflection layer. At this time, the metal-air-oil film-metal 4-layer medium structure is simplified. IK is the incident wave at vertical incidence, when I IK When it reaches the cast iron-oil film surface, reflection and transmission will occur, R IK is the reflection part, T IK For the transmission part.

[0023] As an embodiment of the present invention, see Figure 3 , this embodiment provides an oil film thickness detection method, comprising: The ultrasonic transducer is arranged near the oil film; a pulse transceiver is used to send periodic pulses to excite the ultrasonic transducer, so that the ultrasonic transducer sends an ultrasonic signal with a preset frequency; When the oil film thickness is much smaller than the half wavelength of the ultrasonic wave, the oil film layer is equivalent to a light spring, and the equivalent spring stiffness K of the oil film layer is expressed as: ; Where: B is the bulk modulus of the oil film; h is the thickness of the oil film; Calculate the reflection coefficient R(f) under the spring model:

[0024] ; Where: Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film; K is the equivalent spring stiffness of the oil film layer; ω is the angular frequency of the ultrasonic wave, ω = 2πf, f is the ultrasonic wave frequency; After conversion, the spring model oil film thickness h is calculated according to the following formula:

[0025] ; Where: ρ is the density of the lubricating medium; c is the sound velocity of the lubricating medium; Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film respectively.

[0026] For details, see the attached Figure 2 The figure shows the acoustic parameter diagram of different materials. When the media on both sides of the oil film are air and cast iron respectively, the corresponding Z1=0.41 and Z3=41.50.

[0027] In some preferred embodiments, see the attached Figure 3 , also includes: CCD camera 2 is used to collect images of different oil film thicknesses; The image collected by the CCD camera 2 is coupled with the oil film thickness value obtained by measurement to obtain a standard image database of different oil film thicknesses; Then, the actual oil film image is obtained by an online CCD camera 2, matched with the standard image database, and then a difference image is obtained, which is then interpolated by a computer 3 to determine the oil film thickness.

[0028] As another preferred embodiment of the present invention, this embodiment provides a device for implementing the above-mentioned oil film thickness detection method. Figure 3 , including: an ultrasonic transducer 1, a CCD camera 2 and a computer 3, wherein the ultrasonic transducer 1 and the CCD camera 2 are both connected to the computer 3, the ultrasonic transducer 1 is used to emit an ultrasonic signal with a preset frequency, the computer 3 stores a standard image database of different oil film thicknesses, the CCD camera 2 is used to collect images and send them to the computer 3, after the computer 3 obtains the actual oil film image, it matches it with the standard image database and performs subtraction to obtain a difference image, and then judges the oil film thickness through computer interpolation.

[0029] The present invention also provides an electronic device, including a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor, and the processor is prompted by the machine-executable instructions to implement the steps of an oil film thickness detection method described in any of the above embodiments.

[0030] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0031] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0032] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0033] These computer program instructions may also be loaded onto a computer or other programmable data processing device, so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process.

[0034] The present invention also provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by a processor, an oil film thickness detection method described in any of the above embodiments is implemented. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk (HDD) or a solid-state drive (SSD), etc.; the storage medium may also include a combination of the above-mentioned types of memory.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for detecting oil film thickness, characterized in that: include: The ultrasonic transducer is arranged near the oil film; a pulse transceiver is used to send periodic pulses to excite the ultrasonic transducer, so that the ultrasonic transducer sends an ultrasonic signal with a preset frequency; When the oil film thickness is much smaller than the half wavelength of the ultrasonic wave, the oil film layer is equivalent to a light spring, and the equivalent spring stiffness K of the oil film layer is expressed as: ； Where: B is the bulk modulus of the oil film; h is the thickness of the oil film; Calculate the reflection coefficient R(f) under the spring model: ； Where: Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film; K is the equivalent spring stiffness of the oil film layer; ω is the angular frequency of the ultrasonic wave, ω = 2πf, f is the ultrasonic wave frequency; After conversion, the spring model oil film thickness h is calculated according to the following formula: ； Where: ρ is the density of the lubricating medium; c is the sound velocity of the lubricating medium; Z1 and Z3 are the acoustic impedances of the media on both sides of the oil film respectively.

2. The oil film thickness detection method according to claim 1, characterized in that: When the media on both sides of the oil film are air and cast iron respectively, the corresponding Z1=0.41 and Z3=41.

50.

3. The oil film thickness detection method according to claim 1, characterized in that: Also includes: A CCD camera is used to collect images of different oil film thicknesses; The image collected by the CCD camera is coupled with the oil film thickness value obtained by measurement to obtain a standard image database of different oil film thicknesses; The actual oil film image is then obtained through an online CCD camera, matched with the standard image database, and then a difference image is obtained. The oil film thickness is then determined through computer interpolation.

4. A device for implementing the oil film thickness detection method according to claim 3, characterized in that: include: An ultrasonic transducer, a CCD camera and a computer, wherein the ultrasonic transducer and the CCD camera are both connected to the computer, the ultrasonic transducer is used to emit an ultrasonic signal with a preset frequency, the computer stores a standard image database of different oil film thicknesses, the CCD camera is used to collect images and send them to the computer, after the computer obtains the actual oil film image, it matches it with the standard image database and performs subtraction to obtain a difference image, and then judges the oil film thickness through computer interpolation.

5. An electronic device, characterized in that: It comprises a processor and a machine-readable storage medium, wherein the machine-readable storage medium stores machine-executable instructions that can be executed by the processor, and the processor is prompted by the machine-executable instructions to implement the steps of an oil film thickness detection method according to any one of claims 1 to 3.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, an oil film thickness detection method according to any one of claims 1 to 3 is implemented.

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