Film thickness observation method based on piston ring cylinder sleeve friction measurement equipment

Abstract

The invention discloses a film thickness observation method based on piston ring cylinder sleeve friction measurement equipment. The observation method comprises the following steps: preparing the piston ring cylinder sleeve friction measurement equipment; field-of-view calibration: connecting the high-speed camera to the microscope, adjusting the distance between the photosensitive plane of the high-speed camera and the microscope, and placing a graduated scale on the focal plane to calibrate the size of the field-of-view of the camera; searching a movable contact area to ensure that the microscope can capture clear interference fringes; parameters of a high-speed camera and a laser light source are set, and it is ensured that the contact area can be shot within the set exposure time; and 4, starting a spindle motor, starting to continuously collect photos under a set working condition, screening out the photos of the contact area, judging whether the parameters set in the step 4 are reasonable or not according to the imaging quality, and if not, returning to the step 4 to reset the parameters. The observation method can effectively measure the oil film thickness between the piston ring and the cylinder sleeve, and realizes film thickness measurement in a contact area at any position.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of internal combustion engines, and particularly relates to a film thickness observation method based on a piston ring cylinder liner friction measuring device. BACKGROUND

[0002] Poor lubrication of the engine piston ring cylinder liner is an important cause of failure of the friction pair, and the lubricating oil film thickness between them has always been a concern. At present, various technologies are applied to oil film thickness measurement, and various experimental methods have been developed. Resistance method and capacitance method can determine whether contact occurs between metal surfaces, but the measurement results can only reflect the average oil film thickness in the contact area, and cannot reflect the oil film morphology. The X-ray method is to emit X-rays from one side, and the receiving sensor is symmetrically placed on the other side. This method can measure the minimum film thickness along the ray direction in the contact area, but still cannot reflect the oil film distribution in the contact area. In addition, this method has high requirements for the size of the ray beam directed to the oil film and the relative position of the ray beam and the oil film, and the experiment has certain danger. Ultrasonic method is also often used to measure the lubricating oil film thickness between metal friction pairs, but it still cannot reflect the film thickness morphology information in the contact area. In contrast, the optical method has the characteristics of high precision and full-morphology film thickness measurement, and is more suitable for lubrication mechanism research.

[0003] The optical method mainly includes light interference method and fluorescence method. In the existing observation method for simulating piston ring cylinder liner lubrication, the fluorescence method has high observation accuracy and a large observation thickness range, but the actuation motion is mostly rotary motion, and in the few reciprocating motion studies, the experimental speed is low, far from the movement speed of the engine piston ring. In addition, limited by the observation method, most of the experimental tables are simple part-level experimental tables, and the contact area is also static. At present, there are few studies on piston ring cylinder liner lubrication rules using light interference method, most of which can only do some simple simulation experiments on part-level experimental tables, and the motion form, contact form and oil supply mode are far from the actual working conditions. SUMMARY

[0004] The application provides a film thickness observation method based on a piston ring cylinder liner friction measuring device, which can effectively measure the oil film thickness between the piston ring and the cylinder liner, realize film thickness measurement in the contact area at any position, and has a measurement accuracy of nanometer level and a measurement upper limit of 1 micron.

[0005] In order to achieve the above purpose, the application adopts the following specific technical scheme: A film thickness observation method based on a piston ring cylinder liner friction measuring device, the observation method comprising the following steps: Step 1, prepare a piston ring cylinder liner friction measuring device, the measuring device comprising a base, a main shaft motor, an oil sump, a crankshaft, a piston ring cylinder liner assembly, an optical platform, a laser light source, a high-speed camera and a microscope with an objective lens; Step two, field calibration, install the microscope and laser light source on the optical platform, connect the high-speed camera to the microscope, adjust the distance between the light-sensitive plane of the high-speed camera and the microscope, and place a scale on the focal plane to calibrate the size of the camera field of view; Step three, find the dynamic contact area, move the optical platform so that the axis of the microscope is perpendicular to the piston motion axis and is aligned with the light-transmitting window on the piston ring liner assembly, and ensure that the microscope can capture clear interference fringes; Step four, set the parameters of the high-speed camera and the laser light source to ensure that the contact area can be captured within the set exposure time; Step five, start the main shaft motor and begin continuous image acquisition under the set operating conditions, select the contact area images, and determine whether the parameters set in step four are reasonable based on the imaging quality. If not, return to step four to reset the parameters.

[0006] Further, it also includes: Step six, construct the three-dimensional topography of the oil film thickness in the contact area, based on the pictures captured by the high-speed camera, combined with the order analysis and image processing technology of the laser interference fringes, realize the three-dimensional topography measurement and construction of the internal oil film thickness.

[0007] Further, it also includes: Step seven, fusion simulation, based on the geometric structure and mechanical properties of each part in the piston ring liner assembly, as well as the physicochemical properties of the lubricating oil, establish a theoretical model of the piston ring liner friction pair under multiple lubrication states and iteratively solve the oil film thickness, forming an "experiment-simulation" closed-loop verification system.

[0008] Further, in step three, the specific method to ensure that the microscope can capture clear interference fringes is: move the piston ring, when the contact area passes through the field of view of the microscope, ensure that the contact area can be accurately and clearly imaged, require clear fringe boundaries, and obvious light and dark differences in oil film thickness at different positions.

[0009] Further, step four specifically includes: According to the speed set by the experiment, calculate the time required for the contact area to pass through the field of view of the observation position, and adjust the exposure time of the high-speed camera and the power of the laser light source according to the time.

[0010] Further, the main shaft motor, the oil sump, and the optical platform are fixedly installed on the base; the top of the oil sump is fixedly installed with a crankcase; the crankshaft is rotatably installed in the crankcase; the main shaft motor is fixedly connected with the crankshaft for driving the crankshaft to rotate; The piston ring cylinder liner assembly comprises an upper cylinder liner, a cylinder body, a piston, a glass ring, a lower cylinder liner and a connecting rod; the cylinder body is arranged in a vertical direction and is fixedly installed at the top of the crankcase; the upper cylinder liner, the glass ring and the lower cylinder liner are sequentially connected in a vertical direction from top to bottom to form a cylinder liner and are tightly fitted to the inner wall of the cylinder body; the piston is provided with a piston ring in sealing fit with the inner wall of the cylinder liner; the connecting rod is connected between the piston and the crankshaft; the cylinder body is provided with a light-transmitting window; the inner surface of the glass ring is provided with a layer of chromium film; The crankcase is provided with an oil injection nozzle for injecting lubricating oil to the piston and the piston ring; The high-speed camera, the microscope and the laser light source are installed on an optical platform for supporting the high-speed camera, the microscope and the laser light source; the high-speed camera is oppositely arranged with the glass ring in the light-transmitting window through the microscope; the laser light emitted by the laser light source is vertically emitted to the glass ring through the objective lens of the microscope; the laser light is reflected on the surface of the piston ring and the surface of the chromium film on both sides of the oil film respectively and interferes with each other to form mutually superimposed bright and dark stripes reflected to the microscope, and the bright and dark stripes are imaged on the photosensitive element of the high-speed camera, and the thickness of the oil film is determined according to the wavelength of the laser light, the number of interference stripes and the brightness information.

[0011] Further, the measuring device further comprises an oil pump motor, a double oil pump and an oil storage tank fixedly installed on the top of the base; The oil pump motor is used for driving the double oil pump to work; The double oil pump is used for pumping the lubricating oil in the oil sump to the oil storage tank and delivering the lubricating oil in the oil storage tank to the oil injection nozzle.

[0012] Further, the electric control system for controlling the main shaft motor, the oil pump motor, the laser light source and the high-speed camera is further included; and the electric control system is installed on the base.

[0013] Further, the cylinder body is uniformly provided with four light-transmitting windows in a circumferential direction; The height of the light-transmitting window covers the entire stroke of the piston; The glass ring is located in the stroke of the piston.

[0014] Further, the inner wall of the cylinder body is provided with a limiting flange for limiting the bottom end surface of the lower cylinder liner.

[0015] Further, the large head of the connecting rod is connected to the crankshaft in a loose fit, and the small head of the connecting rod is fixedly connected to the piston through a piston pin.

[0016] Further, the two ends of the crankshaft are installed in the crankcase through sliding bearings and are fixedly connected between the motor shaft of the main shaft motor through a coupling; and the electric control system is installed on the base.

[0017] Further, the cylinder body and the crankcase are connected through fasteners.

[0018] Compared with the prior art, the technical scheme of the application has the following beneficial effects: The observation method of the application utilizes a piston ring cylinder liner friction measuring device, and realizes the thickness observation of the lubricating oil film through field calibration, dynamic contact area searching, parameter setting of the high-speed camera and the laser light source, and continuous photo acquisition. The above observation method can effectively measure the oil film thickness between the piston ring and the cylinder liner, realize the film thickness measurement in the contact area at any position, and the measurement accuracy can reach the nanometer level, and the upper limit of the measurement can reach 1 micron. The above observation method combined with high-speed photography and laser interference technology can capture the dynamic contact area of high-frequency reciprocating motion, and study the transformation of the piston ring cylinder liner lubrication system under the coupling of various working conditions such as complex force field, multiphase flow and strong variable speed.

[0019] The measuring device used in the observation method is composed of an upper cylinder liner, a glass ring and a lower cylinder liner which are connected in sequence from top to bottom, a transparent coated glass ring with the same size precision is used to replace a section of the cylinder liner, and a light transmission window is arranged in the circumferential direction of the cylinder body, the film thickness between the piston ring and the glass ring is measured by using the high-speed camera and the microscope to observe the interference light reflected on both sides of the oil film through the light transmission window; the film thickness at a certain height in the circumferential direction can be observed by rotating the cylinder body, the height position of the glass ring is adjusted by installing upper cylinder liners and lower cylinder liners with different heights, so as to realize the change of the observation position in the stroke height direction, and the film thickness at any position in the full stroke and full circumferential direction can be measured through multiple disassembly and assembly, so as to establish the film thickness distribution in the full stroke and full circumferential direction. The measuring device is convenient to disassemble and assemble, can simulate the real piston ring cylinder liner lubrication condition, and avoid the influence of strong and occasional differences caused by combustion on the film thickness measurement. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flow chart of the film thickness observation method based on the piston ring cylinder liner friction measuring device of the application; Figure 2 The structural schematic diagram of the piston ring cylinder liner friction measuring device used in the observation method of the application; Figure 3 The enlarged structural schematic diagram of the piston ring cylinder liner assembly; Figure 4 The schematic diagram of the principle of measuring the lubricating oil film thickness by using the interference light;

[0021] Reference signs: 1-main shaft motor; 2-electronic control system; 3-oil pump motor; 4-double oil pump; 5-oil storage tank; 6-oil pan; 7-crankshaft; 8-piston ring cylinder liner assembly; 9-laser light source; 10-microscope; 11-high-speed camera; 12-upper cylinder liner; 13-cylinder body; 14-piston; 15-glass ring; 16-lower cylinder liner; 17-connecting rod; 18-piston ring; 19-lubricating oil film; 20-chromium film. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To address the difficulty in measuring the oil film thickness of the piston ring-cylinder liner friction pair in high-power-density engines, this invention mainly solves the following three technical problems: Traditional experimental methods cannot measure the oil film thickness distribution morphology within the contact area, and their measurement results often fail to consider the minimum film thickness within the entire contact area; Traditional measurement methods still tend to be contact-based measurements, with the measurement range including other locations outside the contact area, and the dynamic response is slow; Traditional measurement methods are mostly applied to measurements in fixed contact areas, and the motion is mostly rotational, resulting in a limited number of controllable operating parameters that can be achieved by the experimental setup.

[0024] This invention provides a method for observing film thickness based on a piston ring and cylinder liner friction measuring device, such as... Figure 1 As shown, the observation method includes the following steps: Step 1: Prepare the piston ring and cylinder liner friction measuring equipment. For example... Figure 2 As shown, the measuring device includes a base (not shown), a spindle motor 1, an oil pan 6, a crankcase (not shown), a crankshaft 7, a piston ring and cylinder liner assembly 8, an optical platform (not shown), a laser light source 9, a high-speed camera 11, and a microscope 10 with an objective lens. The base serves as the foundation of the entire measuring device and is located at the bottom. The spindle motor 1, oil pan 6, and optical platform are all fixedly mounted on the base. The crankcase is fixedly mounted on the top of the oil pan 6. The crankshaft 7 is rotatably mounted on the crankcase, for example, both ends of the crankshaft 7 are mounted to the crankcase via bearings. The spindle motor 1 is fixedly connected to the crankshaft 7 via a coupling to drive the crankshaft 7 to rotate. Figure 3As shown, the piston ring cylinder liner assembly 8 comprises a cylinder body 13, a piston 14, an upper cylinder liner 12, a glass ring 15, a lower cylinder liner 16 and a connecting rod 17; the cylinder body 13 is arranged in a vertical direction and is fixedly installed at the top of the crankcase; the bottom end of the cylinder body 13 can be provided with a flange for fixed connection with the crankcase, and is fixedly connected to the crankcase through the flange and fasteners. The upper cylinder liner 12, the glass ring 15 and the lower cylinder liner 16 are sequentially connected in a vertical direction from top to bottom to form a cylinder liner and are tightly fitted to the inner wall of the cylinder body 13. The inner wall of the cylinder body 13 is provided with a limiting flange (not shown in the figure) for limiting the bottom end surface of the lower cylinder liner 16. The piston 14 is provided with a piston ring 18 in sealing fit with the inner wall of the cylinder liner; the connecting rod 17 is connected between the piston 14 and the crankshaft 7, the large end of the connecting rod 17 is loosely connected with the crankshaft 7, and the small end of the connecting rod 17 is fixedly connected with the piston 14 through a piston pin, and the rotation of the crankshaft 7 is converted into the reciprocating linear motion of the piston 14 in the vertical direction through the connecting rod 17. During the movement of the piston 14, the piston 14 and the piston ring 18 form sliding friction with the cylinder liner formed by the upper cylinder liner 12, the glass ring 15 and the lower cylinder liner 16. The cylinder body 13 is provided with a light-transmitting window, which is a long strip-shaped opening arranged in a vertical direction and penetrating through the wall thickness of the cylinder body 13, so that the glass ring 15 inside can be directly observed through the light-transmitting window. The cylinder body 13 can be uniformly provided with four light-transmitting windows in the circumferential direction. The height of the light-transmitting window covers the entire stroke of the piston 14, that is, the entire stroke of the piston 14 does not exceed the height of the light-transmitting window, so that the entire movement process of the piston 14 can be observed through the light-transmitting window. The glass ring 15 is located within the stroke of the piston 14. The inner surface of the glass ring 15 is provided with a layer of chromium film 20; an oil nozzle for spraying lubricating oil to the piston 14 and the piston ring 18 is arranged in the crankcase, and lubricating oil is sprayed to the dome of the piston 14 and between the piston 14 and the cylinder liner through the oil nozzle to form a lubricating oil film 19 between the piston 14 and the cylinder liner. In order to provide lubricating oil with a predetermined pressure and flow rate to the oil nozzle, an oil pump motor 3, a double oil pump 4 and an oil storage tank 5 are also fixedly installed on the top of the base; the output shaft of the oil pump motor 3 is fixedly connected with the rotating shaft of the double oil pump 4 through a shaft coupling for driving the double oil pump 4 to work; the double oil pump 4 is used for pumping lubricating oil in the oil sump 6 into the oil storage tank 5, and delivering the lubricating oil in the oil storage tank 5 to the oil nozzle. The high-speed camera 11, the microscope 10 and the laser light source 9 are installed on an optical platform for supporting the high-speed camera 11, the microscope 10 and the laser light source 9, and the optical platform can be composed of a lifting support. The high-speed camera 11 is oppositely arranged with the glass ring 15 in the light-transmitting window through the microscope 10, and the lubricating oil film 19 between the glass ring 15 and the piston 14 is observed through the microscope 10, the light-transmitting window and the glass ring 15.The laser emitted by the laser light source 9 is vertically emitted to the glass ring 15 through the objective lens of the microscope 10; the light emitting direction of the laser light source 9 is vertically arranged with the optical axis of the microscope 10, and a half-transmission half-reflection lens can be arranged in the microscope 10 for reflecting the laser emitted by the laser light source 9 and transmitting the light reflected from the lubricating oil film 19 into the high-speed camera 11. The laser is reflected on the surface of the piston ring 18 and the surface of the chromium film 20 on both sides of the oil film, respectively, and interferes with each other to form mutually superimposed bright and dark stripes reflected to the microscope 10, and the bright and dark stripes are imaged on the photosensitive element of the high-speed camera 11, and the thickness of the oil film is determined according to the wavelength of the laser, the number of interference stripes and the brightness information. In order to realize the automatic control of the measuring device, an electric control system 2 is also installed on the base, and the electric control system 2 is signal connected with the main shaft motor 1, the oil pump motor 3, the laser light source 9 and the high-speed camera 11 for controlling the main shaft motor 1, the oil pump motor 3, the laser light source 9 and the high-speed camera 11.

[0025] Step two, field calibration, install the microscope 10 and the laser light source 9 on the optical platform, connect the high-speed camera 11 to the microscope 10 through an adapter ring, adjust the distance between the photosensitive plane of the high-speed camera 11 and the microscope 10, and place a scale on the focal plane before the experiment to calibrate the size of the camera field of view.

[0026] Step three, find the dynamic contact area, move the optical platform so that the axis of the microscope 10 is perpendicular to the motion axis of the piston 14, and align the light transmission window on the cylinder body 13 of the piston ring liner assembly 8, to ensure that the microscope 10 can capture clear interference stripes. The specific method to ensure that the microscope 10 can capture clear interference stripes is to move the piston ring 18, and when the contact area passes through the field of view of the microscope 10, ensure that the contact area can be accurately and clearly imaged, and the stripe boundary is clear, and the light and dark difference of the oil film thickness at different positions is obvious. When capturing the high-frequency reciprocating dynamic contact area, based on the high-frequency reciprocating characteristics of the piston ring 18, dark field strong light and high-speed shooting technology are set to realize non-contact high-speed dynamic capture of the contact area boundary in a small field of view, and clear and accurate black and white images are obtained.

[0027] Step four, set the parameters of the high-speed camera 11 and the laser light source 9 to ensure that the contact area can be photographed under the set exposure time. Specifically, according to the set speed, the time required for the contact area to pass through the field of view of the observation position is calculated, and the exposure time of the high-speed camera 11 and the power of the laser light source 9 and other auxiliary parameters are adjusted according to the time. Adjust the power of the laser light source 9 to ensure that the contact area can be photographed by the high-speed camera 11 under the set exposure time.

[0028] Step five, experimental test, start the main shaft motor 1, and start continuous photographing under the set working condition, select the contact area photos, and determine whether the parameters set in step four are reasonable according to the imaging quality, and return to step four to reset the parameters if they are not reasonable.

[0029] Step six, construct the contact area oil film thickness three-dimensional topography, according to the picture captured by high-speed camera 11, combined with the order analysis and image processing technology of laser interference fringes, realize the three-dimensional topography measurement and construction of the internal oil film thickness, and study the transition mechanism of the piston ring 18-cylinder liner tribology state with different working condition parameters.

[0030] Step seven, fusion simulation, according to the geometric structure and mechanical properties of each part in the piston ring cylinder liner assembly 8, and the physicochemical properties of lubricating oil, establish the theoretical model of the piston ring 18 cylinder liner friction pair under multiple lubrication states and iteratively solve the oil film thickness, form the "experiment-simulation" closed loop verification system, significantly improve the prediction accuracy and reliability of the high power density internal combustion engine piston ring 18 cylinder liner oil film thickness.

[0031] The above observation method uses a piston ring cylinder liner friction measuring device, and through field calibration, finding the dynamic contact area, setting the parameters of the high-speed camera 11 and the laser light source 9, and continuously collecting photos to realize the thickness observation of the lubricating oil film 19, which can effectively measure the oil film thickness between the piston ring 18 and the cylinder liner, realize the film thickness measurement in the contact area at any position, and the measurement accuracy can reach nanometer level, and the upper limit of the measurement can reach 1 micron. The above observation method combines high-speed photography and laser interference technology to capture the dynamic contact area of high-frequency reciprocating motion, and study the transition of the piston ring cylinder liner lubrication system under the coupling of complex force field, multiphase flow, strong variable speed and other working conditions.

[0032] The measuring device used in the above observation method consists of an upper cylinder liner 12, a glass ring 15 and a lower cylinder liner 16 connected in sequence from top to bottom, a transparent coated glass ring 15 with the same size precision is used to replace a section of the cylinder liner, and a light transmission window is provided on the circumference of the cylinder body 13, the film thickness between the piston ring 18 and the glass ring 15 is measured by observing the interference light reflected on both sides of the oil film through the light transmission window by the high-speed camera 11 and the microscope 10; the film thickness at a certain height can be observed by rotating the cylinder body 13, the height position of the glass ring 15 can be adjusted by installing upper cylinder liners 12 and lower cylinder liners 16 with different heights to realize the change of the observation position in the stroke height direction, and the film thickness at any position in the full stroke and full circumference can be measured by disassembling and measuring several times, so as to establish the film thickness distribution in the full stroke and full circumference. The measuring device is easy to disassemble and assemble, which can simulate the real piston ring cylinder liner lubrication condition, and avoid the influence of strong and occasional differences caused by combustion on the film thickness measurement.

[0033] The interference principle of the above observation method is shown in Figure 4 As the observation field of the high-speed camera 11 is very small, the curvature of the piston ring 18 and the cylinder liner can be ignored, and Figure 4Ignoring the refraction of the light rays in the solid-liquid interface during the light rays travel, the incident light rays 1 and 2 emitted by the laser light source 9 are emitted from different positions on the outer surface of the glass ring 15 after passing through the microscope 10, and are reflected on the surface of the piston ring 18 and the lower surface of the chromium film 20 layer respectively (ignoring the transmission of the light rays 2), the reflected light of the two is superimposed to form the light rays 3, which returns to the microscope 10 and finally forms an image on the photosensitive plane of the high-speed camera 11. In actual work, the thickness of the oil film between the piston ring 18 and the cylinder liner is usually in the nanometer level, so the laser can use a visible light or ultraviolet light or other shorter wavelength light source. The actual measured oil film thickness information is contained in the extra distance traveled by the light rays 1 compared with the light rays 2. Light has the nature of wave, and the interference light rays 3 will show different brightness in the camera due to the difference in oil film thickness. According to the relative light intensity method, the darkest value and the brightest value of the interference light rays can be calibrated according to different thicknesses, and the oil film thickness can be calculated according to the relative light intensity method.

[0034] The observation process of the above friction measuring device is as follows: after being powered on, the main shaft motor 1 drives the crankshaft 7 to rotate under the control of the electric control system 2, and converts the rotation of the crankshaft 7 into reciprocating motion of the piston 14 through the crankshaft 7 and the connecting rod 17. The piston 14 drives the piston ring 18 to move and form a dynamic contact area with the upper cylinder liner 12, the lower cylinder liner 16 and the glass ring 15. This dynamic contact area observation is rarely studied in the prior art. When the piston ring 18 passes through the glass ring 15, the optical system composed of the laser light source 9, the high-speed camera 11 and the microscope 10 starts to capture the bright and dark stripes, and the oil film thickness is calculated after data processing. By adjusting the height of the upper cylinder liner 12 and the lower cylinder liner 16, and rotating the cylinder block 13, the film thickness of the dynamic contact area can be observed in the whole axial and circumferential direction, and the influence of the lateral force of the piston ring 18 on the lubrication of the piston ring 18 is realized. During work, the oil pump motor 3 drives the double oil pump 4 to spray lubricating oil in the oil storage tank 5 to the top of the piston 14 or the inner surface of the cylinder liner, and the lubricating oil falls into the oil sump 6 under the action of gravity, and then the lubricating oil in the oil sump 6 is recovered to the oil storage tank 5 through the action of the double oil pump 4 to form a circulation.

[0035] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

[0036] In summary, the above is only a preferred embodiment of the present application, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for observing film thickness based on a piston ring and cylinder liner friction measuring device, characterized in that, Includes the following steps: Step 1: Prepare the piston ring and cylinder liner friction measuring equipment. This measuring equipment includes a base, a spindle motor, an oil pan, a crankshaft, a piston ring and cylinder liner assembly, an optical platform, a laser light source, a high-speed camera, and a microscope with an objective lens. Step 2, field of view calibration: Install the microscope and laser light source onto the optical platform, connect the high-speed camera to the microscope, adjust the distance between the photosensitive plane of the high-speed camera and the microscope, and place a scale on the focal plane to calibrate the size of the camera's field of view. Step 3: Locate the moving contact area, move the optical platform so that the axis of the microscope is perpendicular to the piston movement axis, and align it with the light-transmitting window on the piston ring cylinder liner assembly to ensure that the microscope can capture clear interference fringes. Step 4: Set the parameters for the high-speed camera and laser light source to ensure that the contact area can be captured at the set exposure time; Step 5: Start the spindle motor and begin continuously acquiring photos under the set operating conditions. Filter out the photos of the contact area and determine whether the parameters set in Step 4 are reasonable based on the imaging quality. If they are not reasonable, return to Step 4 to reset the parameters.

2. The observation method as described in claim 1, characterized in that, Also includes: Step 6: Construct the three-dimensional morphology of the oil film thickness in the contact area. Based on the images captured by the high-speed camera, combined with the order analysis of laser interference fringes and image processing technology, the three-dimensional morphology of the internal oil film thickness is measured and constructed.

3. The observation method as described in claim 2, characterized in that, Also includes: Step 7: Integrate simulation. Based on the geometric structure and mechanical properties of each part in the piston ring and cylinder liner assembly, as well as the physicochemical properties of the lubricating oil, establish a theoretical model of the piston ring and cylinder liner friction pair under various lubrication states and iteratively solve the oil film thickness to form an "experiment-simulation" closed-loop verification system.

4. The observation method as described in claim 1, characterized in that, In step three, the specific method to ensure that the microscope can capture clear interference fringes is as follows: move the piston ring, and when the contact area passes through the microscope's field of view, ensure that the contact area can be accurately and clearly imaged, requiring clear fringe boundaries and obvious differences in the thickness and brightness of the oil film at different locations.

5. The observation method as described in claim 1, characterized in that, Step four specifically includes: Based on the speed set in the experiment, the time required for the contact area to pass through the field of view of the observation position was calculated, and the exposure time of the high-speed camera and the power of the laser source were adjusted accordingly.

6. The observation method according to any one of claims 1-5, characterized in that, The spindle motor, oil pan, and optical platform are all fixedly mounted on the base; the crankcase is fixedly mounted on the top of the oil pan; the crankshaft is rotatably mounted in the crankcase; the spindle motor is fixedly connected to the crankshaft and is used to drive the crankshaft to rotate. The piston ring cylinder liner assembly includes an upper cylinder liner, a cylinder block, a piston, a glass ring, a lower cylinder liner, and a connecting rod. The cylinder block is arranged vertically and its bottom end is fixedly mounted on the top of the crankcase. The upper cylinder liner, glass ring, and lower cylinder liner are connected sequentially from top to bottom vertically to form a cylinder liner, which is tightly fitted to the inner wall of the cylinder block. The piston is provided with piston rings that seal against the inner wall of the cylinder liner. The connecting rod connects the piston and the crankshaft. The cylinder block has a light-transmitting window. A thin chromium film is provided on the inner surface of the glass ring. The crankcase is equipped with an oil injector for spraying lubricating oil onto the piston and piston rings; A high-speed camera, a microscope, and a laser light source are mounted on an optical platform. The high-speed camera is positioned opposite the glass ring inside the microscope's light-transmitting window. The laser emitted by the laser light source is directed perpendicularly to the glass ring through the microscope's objective lens. The laser light is reflected off the piston ring surface and the chromium film surface on both sides of the oil film and then interferes with each other, forming superimposed bright and dark fringes reflected back to the microscope. These fringes are then imaged on the high-speed camera's photosensitive element. The oil film thickness is determined based on the laser wavelength, the order of the interference fringes, and the brightness information.

7. The observation method as described in claim 6, characterized in that, The measuring device also includes an oil pump motor, a dual oil pump, and an oil storage tank, all fixedly mounted on the top of the base. The oil pump motor is used to drive the dual oil pumps. The dual oil pump is used to pump the lubricating oil in the oil pan to the oil reservoir, and then deliver the lubricating oil in the oil reservoir to the fuel injector.

8. The observation method as described in claim 7, characterized in that, It also includes an electronic control system for controlling the spindle motor, oil pump motor, laser light source, and high-speed camera.

9. The observation method as described in claim 8, characterized in that, The cylinder block has four light-transmitting windows evenly distributed around its circumference; The height of the light-transmitting window covers the entire stroke of the piston; The glass rings are located within the piston's stroke.

10. The observation method as described in claim 6, characterized in that, The inner wall of the cylinder block is provided with a limiting flange for limiting the bottom end face of the lower cylinder liner.

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