Ultrasonic measuring device and method for thickness of oil film of rolling bearing

Abstract

The invention discloses an ultrasonic measuring device and method for the thickness of an oil film of a rolling bearing. The ultrasonic measuring device comprises an electrically-driven main shaft rotating system, a measuring system, a radial loading system, a cooling system, a lubricating system and a positioning system, the electrically-driven main shaft rotating system comprises an electric main shaft seat box body, an electric main shaft and a main shaft; the motorized spindle is installed on the motorized spindle seat box body, the spindle is connected with the output end of the motorized spindle, and the spindle is used for being rotatably connected with the positioning system through a tested bearing; the measuring system comprises a rotating speed measuring assembly and a water immersion ultrasonic probe, the rotating speed measuring assembly is used for measuring the output rotating speed of the motorized spindle, and the water immersion ultrasonic probe is used for generating ultrasonic pulses; the radial loading system is arranged on the positioning system and is used for loading radial force to the main shaft; the cooling system is used for cooling the water immersion ultrasonic probe; the lubricating system supplies lubricating oil to the tested rolling bearing. The device is used for measuring the oil film thickness of the rolling bearing under the high-temperature working condition.

Description

Technical Field

[0001] The invention relates to an oil film thickness measuring device and method, in particular to an oil film thickness ultrasonic measuring device and method for rolling bearings, belonging to the field of lubricating oil film thickness measurement. Background Art

[0002] Rolling bearings can provide a high degree of running accuracy and positioning accuracy, which is essential for applications requiring high precision (such as machine tools, precision instruments, etc.). Under proper installation, lubrication and maintenance conditions, rolling bearings can provide very reliable performance. Rolling bearings can run at very high speeds, which makes them suitable for high-speed rotating equipment such as motors, automobiles, high-speed trains, etc.

[0003] In rolling bearings, good lubrication means that the lubricant can form a sufficient lubricating film between the rolling elements and the raceways. Although this film is relatively thin, it is sufficient to prevent metal-to-metal contact. The presence of the oil film reduces fatigue wear and extends the service life of the bearing. The oil film thickness is an important parameter that directly reflects the lubrication state of the bearing contact area and needs to be measured.

[0004] At present, the measurement of oil film thickness mainly includes electrical method, optical method and ultrasonic method. The electrical method usually determines the film thickness by measuring capacitance or resistance, and its measurement results will be affected by the electrical properties of the material and environmental factors. The optical method usually requires direct contact with the object to be measured or close-range measurement. Therefore, it has high requirements on the flatness and optical properties of the sample surface, and will also affect the reflection and absorption of light. The optical method is only advantageous in the measurement of transparent materials. The ultrasonic method is a non-contact, non-destructive measurement technology that can monitor the change of film thickness online in real time.

[0005] Under high-speed and heavy-load conditions, rolling bearings generate a lot of friction heat inside due to their high speed and heavy load. This friction not only increases the temperature of the bearing itself, but also causes the temperature of the surrounding environment to rise. High temperature will reduce the viscosity of the lubricating oil and weaken the lubrication effect, thereby exacerbating friction and wear. Long-term operation in this environment will not only accelerate the wear process of the bearing, but also cause aging or thermal decomposition of the lubricating oil, releasing more heat. Ultrasonic probes usually require the use of coupling agents to ensure the efficiency of sound wave transmission between the probe and the test object. Under the influence of high temperature, the coupling agent cannot form a stable coupling layer between the ultrasonic probe and the bearing surface, which directly affects the transmission efficiency of the ultrasonic wave and the quality of the reflected signal. An unstable or discontinuous coupling layer may cause the received ultrasonic signal to weaken or distort, which will seriously affect the accuracy and reliability of ultrasonic testing. Summary of the invention

[0006] The present invention aims to overcome the problems in the prior art that the coupling agent temperature around the water immersion ultrasonic probe is too high and the ultrasonic pulse is difficult to act on the center of the oil film contact area, resulting in poor accuracy of the film thickness measurement result in the contact area. A method and device for ultrasonic measurement of the oil film thickness of a rolling bearing are proposed.

[0007] An ultrasonic measuring device for the oil film thickness of a rolling bearing comprises an electric drive spindle rotation system, a measuring system, a radial loading system, a cooling system, a lubrication system and a positioning system;

[0008] The electric-driven spindle rotation system comprises an electric spindle housing, an electric spindle and a spindle; the electric spindle is mounted on the electric spindle housing, the spindle is connected to the output end of the electric spindle, and the spindle is used to be rotatably connected to the positioning system through the rolling bearing to be tested;

[0009] The measuring system comprises a rotation speed measuring component and a water immersion ultrasonic probe, wherein the rotation speed measuring component measures the output rotation speed of the electric spindle, and the water immersion ultrasonic probe generates ultrasonic pulses;

[0010] The radial loading system is arranged in the positioning system to load radial force on the main shaft;

[0011] The cooling system realizes cooling of the water immersion ultrasonic probe;

[0012] The lubrication system is arranged on the positioning system to supply lubrication oil to the rolling bearing to be tested.

[0013] A rolling bearing oil film thickness ultrasonic measurement method, based on the rolling bearing oil film thickness ultrasonic measurement device, the method comprises the following steps:

[0014] First, the lubrication system supplies lubricating oil to the rolling bearing under test, the cooling system cools down the water-immersed ultrasonic probe, and the electric spindle drives the inner ring and roller of the rolling bearing under test to rotate, and an oil film layer is generated between the roller and the outer ring;

[0015] Then, the water immersion ultrasonic probe of the ultrasonic transducer is adjusted so that the focused ultrasonic beam is incident vertically on the oil film layer;

[0016] At the same time, the speed measurement component measures the output speed of the electric spindle, the square wave generated by the signal generator triggers the pulse transceiver, the pulse transceiver emits sharp pulses to stimulate the water-immersed ultrasonic probe to generate a series of ultrasonic pulses acting on the oil film layer, and the digital oscilloscope records the continuously reflected time-domain ultrasonic pulses, which are then sent to the host computer to obtain the frequency domain amplitude of the ultrasonic signal at the center of the contact area, and the minimum frequency domain amplitude of the ultrasonic signal is selected to calculate the minimum reflection coefficient amplitude at the center of the contact area, and the minimum reflection coefficient amplitude is selected and corrected based on the temperature to obtain the oil film thickness in the center of the contact area.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The device of the present application fully considers the movement of rolling bearings under high temperature conditions. When used, it can simulate the movement of rolling bearings under high speed and heavy load conditions, and can then be used as a measurement of the oil film thickness, an important parameter that directly reflects the lubrication state of the bearing contact area.

[0019] 2. This application aims to solve the problem that the coupling agent temperature around the water immersion ultrasonic probe is too high and the film thickness in the contact area is affected by temperature, resulting in poor measurement accuracy. During the continuous operation of the rolling bearing, the coupling agent temperature and the working temperature of the water immersion ultrasonic probe are reduced at low temperature through a cooling system, which can be used to measure the oil film thickness of the rolling bearing under high temperature conditions.

[0020] 3. This application selects the minimum ultrasonic reflection coefficient amplitude and considers the influence of temperature rise on the oil film thickness to calculate the oil film thickness at the center of the contact area. A correction method for elastohydrodynamic film thickness considering the temperature of the contact area is proposed to correct the changes in contact area density and sound velocity caused by thermal effects, thereby more accurately evaluating the elastohydrodynamic film thickness.

[0021] 4. The cooling system designed in this application and the proposed coolant flow control method associated with the working conditions can ensure that the working environment temperature of the ultrasonic probe is stable between 20-35°C, making the ultrasonic probe oil film thickness test performance stable, accurate and reliable, overcoming the adverse effects of high temperature environment caused by high bearing speed and high-temperature lubricating oil on the test.

[0022] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A three-dimensional diagram of a rolling bearing oil film thickness measuring device of the present application;

[0024] Figure 2 A top view of the rolling bearing oil film thickness measuring device of the present application;

[0025] Figure 3 for Figure 2 Side view of

[0026] Figure 4 for Figure 2 BB direction view;

[0027] Figure 5 for Figure 2 A partial schematic diagram of the upper half of FIG.

[0028] Figure 6 for Figure 2 A partial schematic diagram of the lower half of FIG.

[0029] Figure 7 for Figure 2 A partial schematic diagram of

[0030] Figure 8 A schematic diagram of a cooling system of the present application;

[0031] Fig. 9 This is a schematic diagram of measuring the oil film thickness at the center of the contact area of ​​the rolling bearing of this application;

[0032] Fig.10 It is a schematic diagram of the cooling effect in the embodiment;

[0033] Fig.11 This is a comparison chart of the average oil film thickness in the center of the contact area of ​​six tests and the theoretical value. DETAILED DESCRIPTION

[0034] The embodiments of the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings. Unless otherwise specified, the technical terms or scientific terms used in this application are the common meanings understood by those skilled in the art to which the present invention belongs.

[0035] There are problems in the existing system, such as the high temperature of the coupling agent around the immersion ultrasonic probe and the difficulty of the ultrasonic pulse acting on the center of the oil film contact area, which makes the film thickness measurement results in the contact area less accurate. In view of this, a rolling bearing oil film thickness measurement device suitable for high temperature working conditions is developed:

[0036] Figure 1-Figure 7 An ultrasonic measuring device for the thickness of oil film of rolling bearing is shown, which comprises an electric drive spindle rotation system 11, a measuring system 12, a radial loading system 13, a cooling system 14, a lubrication system 15 and a positioning system 16;

[0037] The electric-driven spindle rotation system 11 comprises an electric spindle housing 21, an electric spindle 214 and a spindle 211; the electric spindle 214 is mounted on the electric spindle housing 21, the spindle 211 is connected to the output end of the electric spindle 214, and the spindle 211 is used to be rotatably connected to the positioning system 16 through the measured bearing 242;

[0038] The measuring system 12 comprises a rotation speed measuring component and an immersion ultrasonic probe 239, wherein the rotation speed measuring component measures the output rotation speed of the electric spindle 214, and the immersion ultrasonic probe 239 generates ultrasonic pulses;

[0039] The radial loading system 13 is arranged on the positioning system 16 to load radial force on the main shaft 211;

[0040] The cooling system 14 realizes cooling of the water immersion ultrasonic probe 239;

[0041] The lubrication system 15 is disposed on the positioning system 16 to supply lubrication oil to the bearing 242 to be tested.

[0042] The rolling bearing 242 to be tested is a roller bearing.

[0043] The electric spindle 214 designed in this embodiment provides power to the spindle 211 during operation, so that the rolling bearing 242 to be measured on the spindle 211 can rotate at high speed; the radial loading system 13 provides radial loading force, which is transmitted from the spindle 211 to the rolling bearing 242 to be measured through the inner ring roller bearing sleeve 246 to simulate the movement under high-speed and heavy-load conditions; the measuring system 12 is used to measure the relationship between the output speed of the electric spindle 214 and the oil film thickness of the rolling bearing 242 to be measured under high speed or heavy load or high-speed and heavy load conditions; the oil film thickness is preliminarily detected by means of a water-immersed ultrasonic probe 239, and the oil film thickness is calculated by using a method based on the characteristic of the minimum amplitude of the reflection coefficient at the center of the contact area, in order to solve the problem of excessively high temperature of the surrounding coupling agent when measuring with an ultrasonic probe; the cooling system 14 is designed to control the working environment temperature of the ultrasonic probe, so as to accurately measure the oil film thickness; the lubrication system 15 is used to stably provide lubricating oil during the measurement process, thereby generating an oil film layer under high speed, and providing necessary quality assurance for measurability; the positioning system 16 is used to provide a stable basic platform for the measuring device.

[0044] Usually, the electric spindle 214 uses Luoyang Hangte electric spindle.

[0045] For example, refer to Figure 4 and Figure 7 The speed measurement component includes an inner ring speed sensor bracket 22 and a photoelectric sensor 213 ; the photoelectric sensor 213 is arranged below the output end of the electric spindle 214 and is fixed by the inner ring speed sensor bracket 22 .

[0046] In addition, refer to Figure 8 The measurement process also includes a pulse transceiver, a digital oscilloscope and a host computer; the water immersion ultrasonic probe 239 is connected to the pulse transceiver for communication, the pulse transceiver is connected to the digital oscilloscope for communication, and the digital oscilloscope is connected to the host computer for communication.

[0047] Optionally, the photoelectric sensor 213 is installed 10 cm below the Luoyang Hangte electric spindle 214, and the photoelectric sensor 213 is fixed by the inner ring speed sensor bracket 22. The water immersion ultrasonic probe 239 is fixed at the left end of the probe fixture. The pulse transceiver is connected to the water immersion ultrasonic probe 239 to trigger the ultrasonic signal and receive the echo signal, and the echo signal is then transmitted to the host computer through the data digital oscilloscope.

[0048] Reference Figure 4 and Figure 6In order to ensure that the measuring device is reliable and stable, a positioning system is designed. The positioning system 16 includes a box cover 225, a box body 23, a box body positioning groove 24, a disassembly fixing rod 25 and a positioning locking block 256. The box cover 225 is covered on the box body 23, the box body positioning groove 24 is connected to the box body 23, the positioning locking block 256 and the disassembly fixing rod 25 are arranged on the box body 23, and the radial loading system 13 is positioned.

[0049] Reference Figure 4-Figure 7 The electric drive spindle rotation system 11 also includes an electric spindle seat cover 218, an electric spindle coupling 215, a drive end spindle nut 216, a bearing left end cover 217, a supporting ball bearing 221, a bearing outer ring sleeve 222, a radially loaded bearing preload spring 223, a drive end bearing preload washer B224, a test bearing sleeve 235, an axially loaded end cover 237, an outer ring roller bearing sleeve 243, a roller bearing locking nut 245, an inner ring roller bearing sleeve 246, a test end spindle nut 247, a radially loaded bearing preload spring 223, a radially loaded bearing inner spacer 252, a radially loaded bearing spring washer 254, an axial baffle 255, a loaded ball bearing 253, a drive end bearing preload washer A28 and a sleeve 210;

[0050] The electric spindle 214 is installed between the electric spindle housing 21 and the electric spindle upper cover 218. The output end of the electric spindle 214 is connected to the spindle 211 through the electric spindle coupling 215. The left step section of the spindle 211 is provided with a supporting ball bearing 221, a loading ball bearing 253, a radial loading bearing inner spacer 252, a radial loading bearing spring washer 254 and a sleeve 210. The two loading ball bearings 253 are separated by the radial loading bearing inner spacer 252. The radial loading bearing spring washer 254 is arranged on the outer side of the radial loading bearing inner spacer 252. The radial loading bearing preload spring 250 is arranged in the radial loading bearing spring washer 254. The outer rings of the two loading ball bearings 253 are provided with radial loading bearing sleeves 26. The axial baffle 255 is installed on the positioning locking block 256. The sleeve 210 is arranged between the supporting ball bearing 221 and the two loading ball bearings 253. The outer side of the sleeve 210 is provided with a drive end bearing preload washer The radially loaded bearing preload spring 223 is sleeved on the sleeve 210 and is located between the drive end bearing preload washer A28 and the drive end bearing preload washer B224. The supporting ball bearing 221 is arranged at the shaft end of the main shaft 211 and is fixed in the axial direction by the drive end main shaft nut 216 and in the radial direction by the bearing outer ring sleeve 222. The left end cover 217 of the bearing is connected to the bearing outer ring sleeve 222. The main shaft 2 An inner ring roller bearing sleeve 246 and two test end spindle nuts 247 are provided on the right side stepped shaft section 11. The inner ring of the tested bearing 242 is mounted on the inner ring roller bearing sleeve 246 and fixed by a locking nut 245. The inner ring roller bearing sleeve 246 is fixed by two test end spindle nuts 247. The outer ring roller bearing sleeve 243 is mounted on the outer ring of the tested bearing 242 and is installed on the positioning system 16 through the test bearing sleeve 235 and the axial loading end cover 237.

[0051] In the above scheme, by designing various bearings, various sleeves and springs, on the one hand, the main shaft 211 is reliably positioned and high-speed rotation is achieved, and on the other hand, it is also beneficial to the design, assembly and use of the radial loading system 13.

[0052] During actual installation and use, the Luoyang Hangte electric spindle 214 is installed between the electric spindle housing 21 and the electric spindle cover 218. The rotation is transmitted to the spindle 211 by the round head ordinary flat key 212 on the electric spindle coupling 215. The loaded ball bearing 253 is first installed on the stepped part on the left side of the spindle, followed by the radially loaded bearing inner spacer 252, the radially loaded bearing spring washer 254, the radially loaded bearing preload spring 223, and the other loaded ball bearing 253. The outer ring of this pair of ball bearings has a radially loaded bearing sleeve 26, and an axial baffle 255 at the bottom to ensure the fixation of the pair of ball bearings. Then the sleeve 210, the drive end bearing preload washer A28, the radially loaded bearing preload spring 223, the drive end The moving end bearing preload washer B224, the supporting ball bearing 27, the driving end spindle nut 216, the bearing outer ring sleeve 222, the bearing left end cover 217, and finally the bearing left end cover 217 and the bearing outer ring sleeve 222 are fixed to the housing by means of hexagon socket cylindrical head screws; the inner ring roller bearing sleeve 246 is first installed on the stepped shaft part on the right side of the spindle, and then the tested roller bearing 242 is installed, and the inner ring of the roller bearing is fixed by two locking nuts 245, and then the two test end spindle nuts 247 are installed to fix the inner ring roller bearing sleeve 246, and finally the outer ring roller bearing sleeve 243 is installed, and fixed by the test bearing sleeve 235 and the axial loading end cover 237 by means of hexagon socket cylindrical head screws.

[0053] For example, Figure 4 and Figure 5 As shown, the radial loading system 13 includes a loading connector 226, a tension sensor connector 228, a tension sensor 229, a hydraulic loading cylinder 230, a hydraulic cylinder connecting rod 231, a hydraulic cylinder and box connector 232, a tension connector 233, a connecting bolt 238 and two disc springs 227; the hydraulic loading cylinder 230 and the hydraulic cylinder connecting rod 231 are installed on the hydraulic cylinder and box connector 232, the lower part of the hydraulic loading cylinder 230 is connected to the tension sensor 229 through the tension connector 233, the tension sensor 229 is connected to the loading connector 226 through the tension sensor connector 228 and a disc spring 227, and the loading connector 226 is connected to the radial loading bearing sleeve 26 through the connecting bolt 238 and another disc spring 227.

[0054] When this embodiment is used, the lower part of the hydraulic loading cylinder 230 is connected to the tension sensor 229 through the tension connector 233 and the connecting bolt 234, and is connected to the loading connector 226 through the tension sensor connector 228 and a butterfly spring 227 below the tension sensor 229. A butterfly spring 227 is sleeved on the tension sensor connector 228. The loading connector 226 is connected to the radial loading bearing sleeve 26 through the connecting bolt 238 and another butterfly spring 227. The other butterfly spring 227 is sleeved on the connecting bolt 238. The above connection can realize radial loading of the intermediate loading ball bearing 253 of the main shaft, and then the radial force is transmitted to the measured bearing 242 installed on the main shaft through the ball bearing.

[0055] For example, the shaft speed varies between 0 and 10,000 r / min through a 45 kW electric spindle, and the hydraulic loading cylinder 230 applies tension to the shaft, and is controlled by:

[0056] The sensor measures the load F on the roller bearing based on the lever principle. r It is expressed as:

[0057]

[0058] Where F a is the total load of the hydraulic cylinder on the shaft, F r is the load on the test roller bearing, and L1 and L2 are the distances from the loading center of the hydraulic loading cylinder to the center of the tested rolling bearing 242 and the supporting ball bearing 221, respectively.

[0059] Optionally, the cooling system 14 comprises an oil mist isolation plate 236, a cooling circulation copper tube 240 and a glass wool insulation plate 241, the cooling circulation copper tube 240 and the glass wool insulation plate 241 are installed in a water tank provided in the outer ring roller bearing sleeve 243, and the oil mist isolation plate 236 is provided between the test bearing sleeve 235 and the outer ring roller bearing sleeve 243. The cooling circulation copper tube 240 is connected to the water pipe of the cooling water circulation machine, and the oil mist isolation plate 236 can separate the lubricating oil from the water tank to avoid contaminating the coupling agent and affecting its properties.

[0060] Furthermore, if Figure 4 As shown, the designed lubrication system 15 is arranged on the axial loading end cover 251, and the axial loading end cover 251 is connected to the box body 23. The lubrication system 15 includes an oil injection pipe 244, a lubricating oil inlet pipe 248 and a loading oil injection ring 249; the lubricating oil inlet pipe 248 and the oil injection pipe 244 are fixed on the loading oil injection ring 249, and are used for oil injection lubrication of the rolling bearing 242 under test.

[0061] Some embodiments are provided below to further illustrate the present application for easier understanding:

[0062] Example 1, reference Figure 1 and Fig. 9 , based on the electric drive spindle rotation system 11, radial loading system 13, cooling system 14, lubrication system 15 and positioning system 16 of the above-mentioned measuring device; in the oil film thickness measurement, the measuring system also includes an ultrasonic sensor with an immersion ultrasonic probe 239, a pulse receiver with a bandwidth of 300MHz, a digital oscilloscope with a sampling rate of 2.5Gs / s and a host computer. The center frequency of the immersion ultrasonic transducer is 25MHz, the focal length in water is 37.5mm, and the diameter of the piezoelectric element is 6mm. The pulse transceiver is connected to the immersion ultrasonic probe 239 to trigger the ultrasonic signal and receive the echo signal, and the echo signal is then transmitted to the host computer through the digital oscilloscope.

[0063] Example 2, reference Figure 1 and Figure 8 The cooling system includes a cooling circulation copper pipe 41 and a glass wool insulation board 42, which are installed in the water tank above the outer ring roller bearing sleeve 243, and the glass wool insulation board 42 is sealed with the inner wall of the water tank. The water pipe of the cooling water circulation machine is connected to the cooling circulation copper pipe, and the oil mist isolation plate 236 can separate the lubricating oil from the water tank to avoid contamination of the coupling agent affecting its properties.

[0064] Example 3, see Fig.10 The coupling agent temperature changes with time were measured under radial load of 8000N, different speed conditions, and whether a cooling device was set. The condensed water flow rate used under 10000r / min condition was 0.5L / min, the condensed water flow rate used under 8000r / min condition was 0.3L / min, and the condensed water flow rate used under 6000r / min condition was 0.2L / min. The final water temperature was maintained at around 30°C, and the influence of water temperature on the ultrasonic probe was negligible.

[0065] Reference Figure 1-Figure 10 Based on the rolling bearing oil film thickness measuring device of the above embodiment, a rolling bearing oil film thickness measuring method is also provided.

[0066] First, the lubrication system 15 supplies lubricating oil to the rolling bearing 242 to be tested, the cooling system 14 cools down the water-immersed ultrasonic probe 239, and the electric spindle 214 drives the inner ring and roller of the rolling bearing 242 to be tested to rotate, and an oil film layer is generated between the roller and the outer ring of the rolling bearing 242 to be tested;

[0067] Then, the water immersion ultrasonic probe 239 of the ultrasonic transducer is adjusted using the existing five-degree-of-freedom displacement platform, and the focused ultrasonic beam is vertically incident on the oil film layer;

[0068] At the same time, the speed measurement component measures the output speed of the electric spindle 214, the square wave generated by the signal generator triggers the pulse transceiver, and the pulse transceiver transmits a sharp pulse to stimulate the water-immersed ultrasonic probe 239 to generate a series of ultrasonic pulses acting on the oil film layer. The digital oscilloscope records the continuous reflected time domain ultrasonic pulses, and then sends them to the host computer to obtain the frequency domain amplitude of the ultrasonic signal at the center of the contact area, and selects the minimum frequency domain amplitude of the ultrasonic signal to calculate the minimum reflection coefficient amplitude at the center of the contact area. The minimum reflection coefficient amplitude is selected and corrected based on the temperature to obtain the oil film thickness in the center of the contact area.

[0069] The method for calculating the thickness of the oil film at the center of the oil film contact area includes calculating the reflection coefficient. The reflection coefficient is calculated according to the frequency domain amplitude of the center frequency of the ultrasonic probe corresponding to the target ultrasonic reflection wave signal. The minimum reflection coefficient amplitude |R(f c )|:

[0070]

[0071] Where f c is the center frequency of the sensor, A min is the minimum frequency domain amplitude, A ref is the mean amplitude of the non-rolling element area of ​​the rolling bearing, r ref is the reflection constant of the steel-oil interface, and its value is 0.944;

[0072] Since high-temperature lubricating oil causes a large temperature rise in the contact area and its vicinity, it seriously affects its acoustic characteristics and causes measurement errors. Therefore, it is necessary to perform temperature compensation correction on the test results. According to formula (1), the minimum reflection coefficient amplitude is selected and the method of obtaining the oil film thickness in the center of the contact area based on temperature correction is as follows:

[0073]

[0074] Where ρ s and c s They are the density and longitudinal sound velocity of the outer ring of the rolling bearing under test;

[0075] Where B = B(x,y) and is calculated by the following formula:

[0076]

[0077] Where η is the dynamic viscosity of the lubricating oil, P(x,y) is the oil film pressure, and B 00 is the product of the density of the lubricating oil and the square of the speed of sound at room temperature, β k is the viscosity-temperature coefficient of the lubricating oil, and B(x, y) represents the coordinate position of the center of the contact area.

[0078] In the process of realizing the above-mentioned oil film thickness measurement, the coupling agent around the probe needs to be cooled down. The following is the general deduction process of designing the cooling method:

[0079] The cooling circulation copper tube and the glass wool insulation board are installed in the water tank above the outer ring roller bearing sleeve, and the glass wool insulation board is sealed with the inner wall of the water tank; the copper tube has a high thermal conductivity, and the glass wool can still maintain stable performance and shape after being exposed to high temperature environment for a long time, has low thermal conductivity and is not easy to absorb moisture; the water pipe of the cooling water circulation machine is connected to the cooling circulation copper tube, and the oil mist isolation plate can separate the lubricating oil from the water tank to avoid contaminating the coupling agent and affecting its properties.

[0080] The friction torque of a cylindrical roller bearing is:

[0081] M=f1F r d m (4)

[0082] f1 is a coefficient related to the bearing size and the load it bears. For cylindrical roller bearings, f1 is between 0.0002 and 0.0004. Take f1 = 0.0003, F r is the radial load in N.

[0083] The power of the bearing is equal to the load multiplied by the speed or the friction torque multiplied by the speed, so the power loss caused by the bearing friction torque can be calculated as follows:

[0084] H=0.001M·ω (5)

[0085] Where: H is the power loss of the bearing, in W, M is the friction torque of the bearing, in N·mm, ω is the angular velocity of the bearing, in rad / s. If the bearing speed is in r / min, the above formula becomes:

[0086] H=1.047×10 -4 M·n (6)

[0087] Since the cooling area is approximately 1 / 10 of the entire bearing, a coefficient K = 0.1 is introduced before power loss.

[0088] H1=K·H (7)

[0089] A large amount of heat is generated during the operation of rolling bearings under high-speed and heavy-load conditions, and then the heat is transferred to the coupling agent through the outer ring, causing the coupling agent water temperature to rise. The heat generated in this area after the bearing runs for time t is:

[0090] Q=H1·t (8)

[0091] For cooling water to take away heat, the following conditions must be met:

[0092]

[0093] Where c is the specific heat of water, in J / (kg·℃), Q w is the flow rate, unit L / min, ρ w is the water density, in kg / m 3 , ΔT is the cooling water temperature difference, unit is ℃.

[0094] The flow rate should meet the following requirements:

[0095]

[0096] The immersion ultrasonic probe 239 is affected. The cooling system 14 is designed as follows: a heat-insulating material glass wool 241 is arranged in the middle of the coupling agent area, a copper tube with an inner diameter of 3 mm and a thickness of 1 mm is installed, and a flow rate Q of 5°C related to high temperature conditions is passed. w The circulating water is used for cooling. It is finally found that as the running time of the rolling bearing 242 under test increases, the upper water temperature finally reaches equilibrium, which can meet the requirement of 20-35°C of the water temperature around the water immersion ultrasonic probe 239.

[0097] Reference Figure 1 and Fig. 9 , further explain the use process of this measurement method: first install the glass wool insulation board 241 and the cooling circulation copper tube 240 of the cooling system 14, connect the external cooling water circulation machine, inject an appropriate amount of distilled water into the water tank until the ultrasonic probe is immersed, and then adjust the probe position through the five-dimensional translation stage to align the center circular hole position of the insulation board. Turn on the lubrication system 15 so that the oil injection pipe 244 lubricates the measured bearing 242, start the electric spindle 214 and set the speed to make the measured bearing 242 rotate, load the measured bearing 242 through the hydraulic loading cylinder 230, and turn on the cooling water circulation machine at the same time. Finally, turn on the pulse transceiver and digital oscilloscope and save the measurement data. After the test is completed, first turn off the electric spindle power supply, then the oil injection control switch, turn off the cooling water circulation machine, use a straw, paper towel, etc. to clean the distilled water in the water tank, and finally, the above algorithm can be used to achieve real-time measurement of oil film thickness. An implementation example of the test is given. Fig.11 In summary, this test bench can realize ultrasonic measurement of film thickness in the center of the contact zone of rolling bearings under high temperature conditions.

[0098] The present invention has been disclosed as above with preferred implementation cases, but it is not used to limit the present invention. Any technician familiar with the profession can make slight changes or modifications to equivalent implementation cases with equivalent changes by using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention, which still fall within the scope of the technical solution of the present invention.

Claims

1. An ultrasonic measuring device for the oil film thickness of a rolling bearing, characterized in that: It comprises an electric drive spindle rotation system (11), a measuring system (12), a radial loading system (13), a cooling system (14), a lubrication system (15) and a positioning system (16); The electric-driven spindle rotation system (11) comprises an electric spindle housing (21), an electric spindle (214) and a spindle (211); the electric spindle (214) is mounted on the electric spindle housing (21), the spindle (211) is connected to the output end of the electric spindle (214), and the spindle (211) is used to be rotatably connected to the positioning system (16) through a measured rolling bearing (242); The measuring system (12) comprises a rotation speed measuring component and an immersion ultrasonic probe (239), wherein the rotation speed measuring component measures the output rotation speed of the electric spindle (214), and the immersion ultrasonic probe (239) generates ultrasonic pulses; The radial loading system (13) is arranged on the positioning system (16) to load radial force on the main shaft (211); The cooling system (14) realizes cooling of the water immersion ultrasonic probe (239); The lubrication system (15) is arranged on the positioning system (16) to supply lubrication oil to the rolling bearing (242) to be tested.

2. The ultrasonic measuring device for rolling bearing oil film thickness according to claim 1, characterized in that: The rotation speed measurement component comprises an inner ring rotation speed sensor bracket (22) and a photoelectric sensor (213); the photoelectric sensor (213) is arranged below the output end of the electric spindle (214) and is fixed by the inner ring rotation speed sensor bracket (22).

3. The ultrasonic measuring device for the oil film thickness of a rolling bearing according to claim 1, characterized in that: The positioning system (16) comprises a box cover (225), a box body (23), a box body positioning groove (24), a disassembly fixing rod (25) and a positioning locking block (256); the box cover (225) is covered on the box body (23); the box body positioning groove (24) is connected to the box body (23); the positioning locking block (256) and the disassembly fixing rod (25) are arranged on the box body (23) and position the radial loading system (13).

4. The ultrasonic measuring device for the oil film thickness of a rolling bearing according to claim 1, characterized in that: The electric drive spindle rotation system (11) further comprises an electric spindle seat upper cover (218), an electric spindle coupling (215), a drive end spindle nut (216), a bearing left end cover (217), a supporting ball bearing (221), a bearing outer ring sleeve (222), a radially loaded bearing preload spring (223), a drive end bearing preload washer B (224), a test bearing sleeve (235), an axially loaded end cover (237), an outer ring roller bearing sleeve (243), a roller bearing locking nut (245), an inner ring roller bearing sleeve (246), a test end spindle nut (247), a radially loaded bearing preload spring (223), a radially loaded bearing inner spacer (252), a radially loaded bearing spring washer (254), an axial baffle (255), a loaded ball bearing (253), a drive end bearing preload washer (28) and a sleeve (210); The electric spindle (214) is installed between the electric spindle housing (21) and the electric spindle housing upper cover (218). The output end of the electric spindle (214) is connected to the spindle (211) through the electric spindle coupling (215). A supporting ball bearing (221), a loading ball bearing (253), a radial loading bearing inner spacer (252), a radial loading bearing spring washer (254) and a shaft sleeve (210) are arranged on the left step section of the spindle (211). The two loading ball bearings (253) are separated by the radial loading bearing inner spacer (252). A radially loaded bearing spring washer (254) is arranged outside the inner spacer sleeve (252) of the loading bearing, a radially loaded bearing preload spring (250) is arranged inside the radially loaded bearing spring washer (254), radially loaded bearing sleeves (26) are arranged on the outer rings of the two loading ball bearings (253), an axial baffle (255) is installed on the positioning locking block (256), the sleeve (210) is arranged between the supporting ball bearing (221) and the two loading ball bearings (253), and a drive end bearing preload washer is arranged outside the sleeve (210) A (28) and a drive end bearing preload washer B (224), a radially loaded bearing preload spring (223) is sleeved on the shaft sleeve (210) and is located between the drive end bearing preload washer A (28) and the drive end bearing preload washer B (224), a supporting ball bearing (221) is arranged on the shaft end of the main shaft (211), and is fixed in the axial direction by the drive end main shaft nut (216), and is fixed in the radial direction by the bearing outer ring sleeve (222), the bearing left end cover (217) is connected to the bearing outer ring sleeve (222), and the main shaft (211) ) An inner ring roller bearing sleeve (246) and two test end spindle nuts (247) are arranged on the right stepped shaft section, the inner ring of the tested rolling bearing (242) is installed on the inner ring roller bearing sleeve (246) and fixed by a locking nut (245), the inner ring roller bearing sleeve (246) is fixed by two test end spindle nuts (247), the outer ring roller bearing sleeve (243) is installed on the outer ring of the tested rolling bearing (242), and is installed on the positioning system (16) through the test bearing sleeve (235) and the axial loading end cover (237).

5. The ultrasonic measuring device for the oil film thickness of a rolling bearing according to claim 4, characterized in that: The radial loading system (13) comprises a loading connector (226), a tension sensor connector (228), a tension sensor (229), a hydraulic loading cylinder (230), a hydraulic cylinder connecting rod (231), a hydraulic cylinder and box connector (232), a tension connector (233), a connecting bolt (238) and two disc springs (227); The hydraulic loading cylinder (230) and the hydraulic cylinder connecting rod (231) are installed on the hydraulic cylinder and box connecting piece (232); the lower part of the hydraulic loading cylinder (230) is connected to the tension sensor (229) through the tension connecting piece (233); the tension sensor (229) is connected to the loading connecting piece (226) through the tension sensor connecting piece (228) and a butterfly spring (227); the loading connecting piece (226) is connected to the radial loading bearing sleeve (26) through a connecting bolt (238) and another butterfly spring (227).

6. The ultrasonic measuring device for the oil film thickness of a rolling bearing according to claim 5, characterized in that: The cooling system comprises an oil mist isolation plate (236), a cooling circulation copper tube (240) and a glass wool insulation plate (241); the cooling circulation copper tube (240) and the glass wool insulation plate (241) are installed in a water tank arranged in an outer ring roller bearing sleeve (243); and the oil mist isolation plate (236) is arranged between the test bearing sleeve (235) and the outer ring roller bearing sleeve (243).

7. The ultrasonic measuring device for rolling bearing oil film thickness according to claim 1, characterized in that: The lubrication system comprises an oil spray pipe (244), a lubricating oil inlet pipe (248) and a loading oil spray ring (249); the lubricating oil inlet pipe (248) and the oil spray pipe (244) are fixed on the loading oil spray ring (249) and are used for oil spraying and lubricating the rolling bearing (242) to be tested.

8. A method for ultrasonically measuring the oil film thickness of a rolling bearing, characterized in that: Based on the rolling bearing oil film thickness ultrasonic measuring device according to any one of claims 1 to 8, the method comprises the following steps: First, the lubrication system (15) supplies lubricating oil to the rolling bearing (242) to be tested, the cooling system (14) cools the water-immersed ultrasonic probe (239), the electric spindle (214) drives the inner ring and roller of the rolling bearing (242) to be tested to rotate, and an oil film layer is generated between the roller and the outer ring; Then, the water immersion ultrasonic probe (239) of the ultrasonic transducer is adjusted so that the focused ultrasonic beam is incident vertically on the oil film layer; At the same time, the speed measurement component measures the output speed of the electric spindle (214), the square wave generated by the signal generator triggers the pulse transceiver, the pulse transceiver emits a sharp pulse to stimulate the water-immersed ultrasonic probe (239) to generate a series of ultrasonic pulses acting on the oil film layer, the digital oscilloscope records the continuously reflected time domain ultrasonic pulses, and then sends them to the host computer to obtain the frequency domain amplitude of the ultrasonic signal at the center of the contact area, select the minimum frequency domain amplitude of the ultrasonic signal to calculate the minimum reflection coefficient amplitude at the center of the contact area, select the minimum reflection coefficient amplitude and correct it based on temperature to obtain the oil film thickness at the center of the contact area.

9. The method for ultrasonically measuring the oil film thickness of a rolling bearing according to claim 8, characterized in that: The minimum reflection coefficient amplitude |R(f c )|: In the formula, f c is the center frequency of the sensor, A min is the minimum frequency domain amplitude, A ref is the mean amplitude of the non-rolling element area of ​​the rolling bearing, r ref is the reflection constant of the steel-oil interface and its value is 0.

944.

10. The method for ultrasonically measuring the oil film thickness of a rolling bearing according to claim 9, characterized in that: The method for selecting the minimum reflection coefficient amplitude and correcting the oil film thickness in the center of the contact area based on temperature is: The correction method for oil film thickness is as follows: In the formula, ρ s and c s They are the density and longitudinal sound velocity of the outer ring of the rolling bearing being tested: Where B = B(x,y) and is calculated by the following formula: Where η is the dynamic viscosity of the lubricating oil, P(x,y) is the oil film pressure, and B 00 is the product of the density of the lubricating oil and the square of the speed of sound at room temperature, β k is the viscosity-temperature coefficient of lubricating oil.

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