Cylindrical roller bearing oil film thickness measuring device and measuring method

Abstract

The present invention discloses a device and method for measuring the oil film thickness of cylindrical roller bearings. This method replaces the traditional immersion focused ultrasonic probe with a non-focused ultrasonic straight probe that is easy to install and has good adaptability to coupling agents. By establishing a correction coefficient related to spatial resolution based on the effective measurement area ratio of the straight probe, the ultrasonic measurement results are corrected, reducing the impact of the sound pressure averaging effect in the echo reflection area on the measurement results, thereby maximizing the spatial resolution and accuracy of the measurement results and resolving the limitations of ultrasonic detection methods on the use of ultrasonic probes in rolling bearing film thickness measurement. The present invention enables the ultrasonic film thickness measurement method to be truly applied to rolling bearing film thickness measurement in actual industrial environments, can more accurately obtain the actual lubrication status of the bearing, and thus guide the design and application of bearing lubrication industry, avoiding machine damage, property loss, and personal injury caused by poor bearing lubrication.

Description

Technical Field

[0001] The present invention relates to the field of bearing oil film thickness measurement, and in particular to a cylindrical roller bearing oil film thickness measurement device and a measurement method. Background Art

[0002] Rolling bearings, as industrial joints, are widely used in various rotating mechanical systems. Their operational stability is closely related to the lubrication status between the rollers and the inner and outer rings. The thickness of the lubricating oil film within the contact area of ​​a rolling bearing provides a direct indicator of the bearing's lubrication contact status. Currently, ultrasonic methods based on stiffness equivalence are widely used in rolling bearing submicron oil film thickness measurement experiments. During actual testing, the echo signal received by the ultrasonic probe reflects the average sound pressure change in the acoustic wave reflection area at the contact interface, known as the probe's averaging effect. Given the extremely small contact area between the rolling element and the outer ring of a rolling bearing, existing online film thickness measurement primarily utilizes immersion-type high-frequency focused probes to minimize the impact of this averaging effect on ultrasonic measurement results. However, in practical application, immersion-type focused probes not only require focusing on the contact interface, making installation and securing difficult, but also the use of couplant water can easily lead to seal leaks, evaporation bubbles that hinder ultrasonic propagation, and environmental corrosion. Therefore, rolling bearing film thickness measurement using immersion-type focused probes is currently limited to laboratory environments and difficult to implement in real-world industrial environments.

[0003] In response to the installation requirements and environmental conditions of actual industrial sites, the present invention replaces the traditional immersion focused probe with a non-focused ultrasonic straight probe that is easy to install and well-adapted to coupling agents for online measurement of film thickness on rolling bearings. However, the divergent acoustic field characteristics of the straight probe result in insufficient spatial resolution, and the averaging effect is significantly greater than that of the focused probe, resulting in large errors in film thickness measurements, making it difficult to meet actual testing requirements. Therefore, while the straight probe can be used in actual industrial field environments, its spatial resolution is poor and the "averaging" effect is not negligible. Research and resolution of the resulting large errors in film thickness measurements are needed. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a cylindrical roller bearing oil film thickness measurement device and measurement method. This method replaces the traditional immersion focused probe with a non-focused ultrasonic straight probe that is easy to install and has good adaptability to coupling agents, meeting the installation and environmental requirements of industrial sites. By establishing a correction coefficient related to the spatial resolution based on the proportion of the effective measurement area of ​​the straight probe, the ultrasonic measurement results are corrected, the influence of the sound pressure averaging effect in the echo reflection area on the measurement results is reduced, and the spatial resolution and accuracy of the measurement results are improved, providing a technical means for the application of film thickness ultrasonic measurement technology in bearing testing in actual industrial environments.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to solve it.

[0006] (1) A cylindrical roller bearing oil film thickness measuring device, comprising: a non-focused ultrasonic sensor, a fixed bracket, and an ultrasonic pulse transmitting and receiving drive device; the non-focused ultrasonic sensor includes a straight probe;

[0007] refer to Figure 2 , Figure 2 This is a schematic diagram of the ultrasonic sensor's straight probe installation position. Reference numeral 1 represents the ultrasonic sensor's straight probe, 2 represents the bearing outer ring, 3 represents the cylindrical roller, 4 represents the retaining bracket, and 5 represents the bearing inner ring. The mounting bracket is used to vertically secure the straight probe 1 to the outer surface of the cylindrical roller bearing's outer ring 2 to be tested. A coupling agent is provided between the straight probe and the outer surface of the cylindrical roller bearing's outer ring. The straight probe is electrically connected to the ultrasonic pulse transmitter and receiver drive device.

[0008] (2) A method for measuring the oil film thickness of a cylindrical roller bearing, based on a cylindrical roller bearing oil film thickness measuring device, comprises the following steps:

[0009] Step 1: Determine the geometric dimensions and operating parameters of the unfocused ultrasonic sensor, the repetition frequency of the ultrasonic pulse transmitter and receiver drive device, and the operating temperature of the coupling agent based on the model of the cylindrical roller bearing to be tested and the operating conditions of the cylindrical roller bearing;

[0010] The geometric dimensions of the non-focused ultrasonic sensor include the straight probe diameter, wherein the straight probe diameter is less than the bearing outer ring width;

[0011] The operating parameters of the non-focused ultrasonic sensor include: center frequency, operating temperature, wherein the center frequency is ≥10 MHz, and the operating temperature is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under specified working conditions;

[0012] The driving pulse transmission repetition frequency of the ultrasonic pulse transmitting and receiving driving device should satisfy the following requirement: when the cylindrical roller bearing is at the maximum speed, the relative movement distance of the straight probe during the interval between two pulse transmissions is less than the width of the reflection area actually received by the straight probe;

[0013] The operating temperature of the coupling agent is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under the set working conditions;

[0014] Step 2: Apply coupling agent to the straight probe and vertically install it to the outer surface of the bearing outer ring through a fixing bracket; electrically connect the straight probe to the ultrasonic pulse transmitting and receiving drive device;

[0015] Step 3, calculating the uncorrected measured center oil film thickness h under the first working condition;

[0016] Step 4: Calculate the theoretical oil film thickness h under the first working condition c ', as the comparison value of the uncorrected measured central oil film thickness;

[0017] Step 5: Repeat step 3 to obtain the uncorrected measured central oil film thickness under the second and third operating conditions at the same speed and repetition frequency, forming an uncorrected measured central oil film thickness matrix M; repeat step 4 to obtain the theoretical oil film thickness under the second and third operating conditions, forming a theoretical oil film thickness matrix T;

[0018] Step 6: Determine the average effect correction factor X based on the effective measurement area ratio of the straight probe s ;

[0019] Step 7: Correct the coefficient X by the average effect s , obtain the corrected measured center oil film thickness hc under any working condition, the calculation formula is:

[0020] h c =X s ·h

[0021] Where h c is the corrected measured center oil film thickness, h is the uncorrected measured center oil film thickness, X s is the average effect correction factor.

[0022] Furthermore, the calculation of the uncorrected measured center oil film thickness includes the following sub-steps:

[0023] Sub-step 4.1, the ultrasonic pulse transmitting and receiving driving device outputs an excitation pulse to drive the ultrasonic transducer and receive a reflected echo from the contact interface; the reflected echo is amplified by an amplifier and the reflected signal is collected, displayed, and stored by an oscilloscope or an acquisition card;

[0024] In sub-step 4.2, extract the peak value of the reflected echo signal and combine it with the steel-oil interface reference signal to obtain the reflectivity of the contact interface. Based on the spring stiffness equivalent model formula, calculate the uncorrected measured center oil film thickness h. The calculation formula is:

[0025]

[0026] Among them, ρ0 is the density of lubricating oil, c0 is the speed of sound in lubricating oil, ρ is the density of bearing steel, c is the speed of sound in bearing steel, z is the acoustic impedance of bearing steel, where z = ρc; R is the reflection coefficient of ultrasonic signal.

[0027] Furthermore, in step 5, the theoretical oil film thickness is obtained by using the Dowson fitting center film thickness formula:

[0028] h c '=3.533α 0.54 (η0u)0.7 E' -0.03 R x 0.43 (Q / l) -0.13

[0029] Or Yang Peiran's fitting formula for the central film thickness:

[0030] h c '=11.9α 0.4 (η0u) 0.74 E' -0.14 R x 0.46 (Q / l) -0.2

[0031] Where α is the viscosity-pressure coefficient of the lubricating oil; η0 is the dynamic viscosity of the lubricating oil at atmospheric pressure; u is the entrainment velocity; E' is the comprehensive elastic modulus of the material; R x is the equivalent curvature radius of the outer raceway; Q is the contact stress; l is the effective length of the roller.

[0032] Furthermore, in step 6, the average effect correction coefficient X is calculated s The calculation formula is:

[0033]

[0034] Among them, d p is the actual measurement area diameter of the ultrasonic straight probe; d r is the distance between adjacent measurement areas; v r is the orbital speed of the rolling element of the cylindrical roller bearing; f r is the ultrasonic repetition frequency; d j is the width or diameter of the straight probe crystal; m is the proportional coefficient, m = d j / d p .

[0035] Furthermore, based on the uncorrected measured center oil film thickness matrix M and the theoretical oil film thickness matrix T obtained in step 5, the following formula is used to obtain the relative error Δ between the corrected measured center oil film thickness and the theoretical oil film thickness:

[0036]

[0037] When Δ is minimum, the corresponding m is the actual proportional coefficient.

[0038] Furthermore, in step 7, the corrected measured center oil film thickness h under any working condition is obtained. c , the calculation formula is:

[0039]

[0040] The beneficial effects of the present invention are as follows: the present invention provides a practical experimental means for detecting the oil film thickness of rolling bearings in industrial field environments, effectively improves the limitations of ultrasonic detection methods on the use of ultrasonic probes in rolling bearing film thickness measurements, minimizes the impact of the average effect on the measurement results, and improves the spatial resolution of the measurement results. While achieving the functions, the present invention also has the following characteristics: First, there are no special requirements for the working environment of the target rolling bearing to be measured; second, during the measurement of the present invention, no damaging processing will be performed on the rolling bearing, which is a non-destructive test and will not affect the operating performance of the bearing; third, the correction coefficient based on the proportion of the effective measurement area of ​​the probe proposed in the present invention can be used not only for the average effect correction and spatial resolution improvement in the film thickness measurement of the straight probe, but also for the average effect correction and spatial resolution improvement in the measurement of other parameters of the straight probe. Fourth, the correction coefficient based on the effective measurement area of ​​the probe proposed in the present invention can be used not only for the average effect correction of the straight probe, but also for the average effect correction of the focused probe. Fifth, the present invention enables the ultrasonic film thickness measurement method to be applied to the film thickness measurement of various rolling bearings in actual industrial environments, which can more accurately obtain the actual lubrication status of the bearings, and then guide the industrial design and application of bearing lubrication, avoiding machine damage, property loss and personal injury caused by poor bearing lubrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0042] Figure 1 This is a schematic diagram of the principle of the "averaging" effect of the straight probe in the present invention.

[0043] Figure 2 It is a schematic diagram of the installation position of the straight probe of the ultrasonic sensor in the present invention.

[0044] Figure 3 This is a diagram of the straight probe ultrasonic measurement model in the present invention.

[0045] Figure 4 This is a diagram showing the oil film thickness measurement results under constant speed and variable load before correction in the present invention.

[0046] Figure 5 This is a diagram showing the oil film thickness measurement results under constant speed and variable load after correction in the present invention.

[0047] Figure 6 This is a diagram showing the oil film thickness measurement results under constant load and variable speed after correction in the present invention.

[0048] In the above figure: 1 straight probe, 2 bearing outer ring, 3 cylindrical roller, 4 cage, 5 bearing inner ring. DETAILED DESCRIPTION

[0049] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0050] The following description sets forth specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art will be able to make similar generalizations without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0051] (1) Please refer to Figure 1 and Figure 2 A cylindrical roller bearing oil film thickness measuring device comprises: a non-focused ultrasonic sensor 1, a fixed bracket, and an ultrasonic pulse transmitting and receiving drive device; the non-focused ultrasonic sensor includes a straight probe; the cylindrical roller bearing to be measured includes an outer ring 2, a cylindrical roller 3, a retaining frame 4, and an inner ring 5. The fixed bracket is used to vertically fix the straight probe to the outer surface of the outer ring of the cylindrical roller bearing to be measured, a coupling agent is filled between the straight probe and the outer surface of the outer ring of the cylindrical roller bearing, and the straight probe is electrically connected to the ultrasonic pulse transmitting and receiving drive device. Reference Figure 1 , Figure 1 Schematic diagram of the principle of the "averaging" effect of a straight probe.

[0052] (2) A method for measuring the oil film thickness of a cylindrical roller bearing, comprising the following steps:

[0053] Step 1: Determine the geometric dimensions and operating parameters of the unfocused ultrasonic sensor, the repetition frequency of the ultrasonic pulse transmitter and receiver drive device, and the operating temperature of the coupling agent based on the model of the cylindrical roller bearing to be tested and the operating conditions of the cylindrical roller bearing;

[0054] The geometric dimensions of the non-focused ultrasonic sensor include the straight probe diameter, wherein the straight probe diameter is less than the bearing outer ring width;

[0055] The operating parameters of the non-focused ultrasonic sensor include: center frequency, operating temperature, wherein the center frequency is ≥10 MHz, and the operating temperature is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under specified working conditions;

[0056] The driving pulse transmission repetition frequency of the ultrasonic pulse transmitting and receiving driving device should satisfy the following requirement: when the cylindrical roller bearing is at the maximum speed, the relative movement distance of the straight probe during the interval between two pulse transmissions is less than the width of the reflection area actually received by the straight probe;

[0057] The operating temperature of the coupling agent is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under the set working conditions;

[0058] Step 2: Apply coupling agent to the straight probe and vertically install it to the outer surface of the bearing outer ring through a fixing bracket; electrically connect the straight probe to the ultrasonic pulse transmitting and receiving drive device;

[0059] Step 3: Calculate the uncorrected measured center oil film thickness h under the first working condition. Specifically, step 3 includes the following two sub-steps:

[0060] Sub-step 3.1, the ultrasonic pulse transmitting and receiving driving device outputs an excitation pulse to drive the ultrasonic transducer and receive a reflected echo from the contact interface; the reflected echo is amplified by an amplifier and the reflected signal is collected, displayed, and stored by an oscilloscope or an acquisition card;

[0061] In sub-step 3.2, extract the peak value of the reflected echo signal and combine it with the steel-oil interface reference signal to obtain the reflectivity of the contact interface. Based on the spring stiffness equivalent model formula, calculate the uncorrected measured center oil film thickness h. The calculation formula is:

[0062]

[0063] Among them, ρ0 is the density of lubricating oil, c0 is the speed of sound in lubricating oil, ρ is the density of bearing steel, c is the speed of sound in bearing steel, z is the acoustic impedance of bearing steel, where z = ρc; R is the reflection coefficient of ultrasonic signal.

[0064] Step 4: Calculate the theoretical oil film thickness h under the first working condition c ', as the comparison value of the uncorrected measured center oil film thickness; specifically, calculate the theoretical oil film thickness h c 'You can use the Dowson fitting center film thickness formula:

[0065] h c '=3.533α 0.54 (η0u) 0.7 E' -0.03 R x 0.43 (Q / l) -0.13

[0066] Or Yang Peiran's fitting formula for the central film thickness:

[0067] h c '=11.9α 0.4 (η0u) 0.74 E' -0.14 R x 0.46 (Q / l) -0.2

[0068] Where α is the viscosity-pressure coefficient of the lubricating oil; η0 is the dynamic viscosity of the lubricating oil at atmospheric pressure; u is the entrainment velocity; E' is the comprehensive elastic modulus of the material; R x is the equivalent curvature radius of the outer raceway; Q is the contact stress; l is the effective length of the roller.

[0069] Step 5: Repeat step 3 to obtain the uncorrected measured central oil film thickness under the second and third operating conditions at the same speed and repetition frequency, forming an uncorrected measured central oil film thickness matrix M; repeat step 4 to obtain the theoretical oil film thickness under the second and third operating conditions, forming a theoretical oil film thickness matrix T;

[0070] Step 6: Determine the average effect correction factor X based on the effective measurement area ratio of the straight probe s ; Calculate the average effect correction factor X s The calculation formula is:

[0071]

[0072] Among them, d p is the actual measurement area diameter of the ultrasonic straight probe; d r is the distance between adjacent measurement areas; v r is the orbital speed of the rolling element of the cylindrical roller bearing; f r is the ultrasonic repetition frequency; d j is the width or diameter of the straight probe crystal; m is the proportional coefficient,

[0073] refer to Figure 3 The straight probe is mainly circular or square. In this embodiment, the straight probe is square, and its actual measurement area, that is, the received contact interface echo reflection area is also square. The width of the actual measurement area along the roller movement direction is defined as d p . The straight probe emits ultrasonic pulses at a certain repetition frequency and receives the reflected echo from the measurement area. When the cylindrical roller passes under the straight probe at a certain speed, according to the principle of relative motion, it can be assumed that the cylindrical roller is stationary and the straight probe rotates over the contact area at a certain speed. In actual measurements, since the straight probe has a large range of sound field emission, its actual measurement area is also larger than that of the focused probe. Therefore, at a certain repetition frequency and rotation speed, the actual two echo reflection areas may overlap. At this time, the distance between adjacent measurement areas is the relative movement distance d of the straight probe. r The distance is determined by the rolling element revolution speed v of the rolling bearing. r and ultrasonic repetition frequency f r Have jointly decided as follows:

[0074]

[0075] In the above overlapping case, the amplitude of the echo sound pressure reflects the average value of the entire reflection area, but the change in the amplitude of the two adjacent echo sound pressures is related to the relative movement distance d. r Therefore, this embodiment will move the distance d r The corresponding area is defined as the effective measurement area of ​​the probe. For a straight probe, the actual measurement area diameter dp, that is, the effective received contact interface echo reflection area, is proportional to the width or diameter dj of the straight probe crystal oscillator. Assume that its proportional coefficient is In actual bearing test environments, the proportional coefficient m is directly related to factors such as the curvature, thickness, and surface roughness of the bearing outer ring. At this time, based on the effective measurement area ratio of the probe, the correction coefficient for improving spatial resolution and thus reducing the influence of the averaging effect can be written as

[0076]

[0077] The correction factor d j 、v r and f r It can be quickly determined according to the probe parameters and test condition parameters. When the straight probe and the cylindrical roller bearing to be tested are determined, d j and d p are all constants, so m is also a constant.

[0078] In actual measurement, d j Can be measured directly by the probe, but d p It is difficult to obtain directly, which makes it difficult to obtain m directly. At this time, based on the uncorrected measured center oil film thickness matrix M and the theoretical oil film thickness matrix T obtained in step 5, the following formula is used to obtain the relative error Δ between the corrected measured center oil film thickness and the theoretical oil film thickness:

[0079]

[0080] When Δ is minimum, the corresponding m is the actual proportional coefficient. In this embodiment, m is rounded to 8.

[0081] Step 7: Substitute the average effect correction factor X in step 6 s , and obtain the corrected measured central oil film thickness h under any working condition c , the calculation formula is:

[0082]

[0083] refer to Figure 4 、 Figure 5 and Figure 6 , Figure 4 This is the oil film thickness measurement result diagram under constant speed and variable load before correction in the present invention. Figure 5This is the oil film thickness measurement result diagram under constant speed and variable load after correction in the present invention. Figure 6 This is a diagram showing the oil film thickness measurement results under constant load and variable speed after correction in the present invention.

[0084] Although the present invention has been described in detail in this specification using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the present invention, are intended to fall within the scope of protection claimed herein.

Claims

1. A method for measuring the oil film thickness of a cylindrical roller bearing, characterized in that: Based on a cylindrical roller bearing oil film thickness measuring device, the cylindrical roller bearing oil film thickness measuring device includes a non-focused ultrasonic sensor, a fixed bracket and an ultrasonic pulse transmitting and receiving driving device; the non-focused ultrasonic sensor includes a straight probe; The fixing bracket is used to vertically fix the straight probe on the outer surface of the outer ring of the cylindrical roller bearing to be tested, a coupling agent is provided between the straight probe and the outer surface of the outer ring of the cylindrical roller bearing, and the straight probe is electrically connected to the ultrasonic pulse transmitting and receiving driving device; The measuring method comprises the following steps: Step 1: Determine the geometric dimensions and operating parameters of the unfocused ultrasonic sensor, the repetition frequency of the ultrasonic pulse transmitter and receiver drive device, and the operating temperature of the coupling agent based on the model of the cylindrical roller bearing to be tested and the operating conditions of the cylindrical roller bearing; The geometric dimensions of the non-focused ultrasonic sensor include the straight probe diameter, wherein the straight probe diameter is less than the bearing outer ring width; The operating parameters of the non-focused ultrasonic sensor include: center frequency, operating temperature, wherein the center frequency is ≥10 MHz, and the operating temperature is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under specified working conditions; The driving pulse transmission repetition frequency of the ultrasonic pulse transmitting and receiving driving device should satisfy the following requirement: when the cylindrical roller bearing is at the maximum speed, the relative movement distance of the straight probe during the interval between two pulse transmissions is less than the width of the reflection area actually received by the straight probe; The operating temperature of the coupling agent is greater than the maximum temperature of the outer ring of the cylindrical roller bearing under the set working conditions; Step 2: Apply coupling agent to the straight probe and vertically install it to the outer surface of the bearing outer ring through a fixing bracket; electrically connect the straight probe to the ultrasonic pulse transmitting and receiving drive device; Step 3, calculating the uncorrected measured center oil film thickness h under the first working condition, specifically includes the following sub-steps: Sub-step 3.1, the ultrasonic pulse transmitting and receiving driving device outputs an excitation pulse to drive the ultrasonic transducer and receive a reflected echo from the contact interface; the reflected echo is amplified by an amplifier and the reflected signal is collected, displayed, and stored by an oscilloscope or an acquisition card; In sub-step 3.2, extract the peak value of the reflected echo signal and combine it with the steel-oil interface reference signal to obtain the reflectivity of the contact interface. Based on the spring stiffness equivalent model formula, calculate the uncorrected measured center oil film thickness h. The calculation formula is: Wherein, ρ0 is the density of lubricating oil, c0 is the speed of sound in lubricating oil, ρ is the density of bearing steel, c is the speed of sound in bearing steel, z is the acoustic impedance of bearing steel, where z = ρc; R is the reflection coefficient of ultrasonic signal; Step 4: Calculate the theoretical oil film thickness h under the first working condition c ', as the comparison value of the uncorrected measured central oil film thickness h; Step 5: Repeat step 3 to obtain the uncorrected measured central oil film thickness under the second and third operating conditions at the same speed and repetition frequency, forming an uncorrected measured central oil film thickness matrix M; repeat step 4 to obtain the theoretical oil film thickness under the second and third operating conditions, forming a theoretical oil film thickness matrix T; Based on the obtained uncorrected measured center oil film thickness matrix M and the theoretical oil film thickness matrix T, the following formula is used to obtain the relative error △ between the corrected measured center oil film thickness and the theoretical oil film thickness: Among them, v r is the orbital speed of the rolling element of the cylindrical roller bearing; d j f is the width or diameter of the straight probe crystal oscillator; r is the ultrasonic repetition frequency; when △ is the smallest, the corresponding m is the actual proportional coefficient; Step 6: Determine the average effect correction factor X based on the effective measurement area ratio of the straight probe s ; Calculate the average effect correction factor X s The calculation formula is: Among them, d p is the actual measurement area diameter of the ultrasonic straight probe; d r is the distance between adjacent measurement areas; Step 7: Correct the coefficient X by the average effect s , obtain the corrected measured center oil film thickness hc under any working condition, the calculation formula is: Where h c is the corrected measured center oil film thickness, h is the uncorrected measured center oil film thickness, X s is the average effect correction factor.

2. The method for measuring the oil film thickness of a cylindrical roller bearing according to claim 1, wherein: In step 4, obtain the theoretical oil film thickness h c 'Use Dowson fitting center film thickness formula: h c '=3.533α 0.54 (η0u) 0.7 E '-0.03 R x 0.43 (Q / l) -0.13 Or Yang Peiran's fitting formula for the central film thickness: h c '=11.9α 0.4 (η0u) 0.74 E '-0.14 R x 0.46 (Q / l) -0.2 Where, α is the viscosity-pressure coefficient of lubricating oil; η0 is the dynamic viscosity of the lubricating oil at atmospheric pressure; u is the entrainment velocity; E' is the comprehensive elastic modulus of the material; R x is the equivalent curvature radius of the outer raceway; Q is the contact stress; l is the effective length of the roller.

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