Piston ring-cylinder sleeve film thickness observation equipment based on light interference method

Abstract

The invention discloses a piston ring-cylinder sleeve film thickness observation device based on a light interference method. A main shaft motor and an oil pan are installed on a base of the observation device. The crankcase is fixedly mounted at the top of the oil pan; the crankshaft is rotationally mounted on the crankcase; the piston ring-cylinder sleeve assembly comprises an upper cylinder sleeve, a cylinder body, a piston, a glass ring, a lower cylinder sleeve and a connecting rod; the cylinder body is fixedly mounted at the top of the crankcase; the upper cylinder sleeve, the glass ring and the lower cylinder sleeve are tightly matched with the inner wall of the cylinder body; a window is formed in the cylinder body; a layer of chromium film is arranged on the inner surface of the glass ring; an oil nozzle is arranged in the crankcase; the high-speed camera is opposite to the glass ring in the window; the laser is reflected on the piston ring surface and the chromium film surface on the two sides of the oil film respectively and then interferes with each other to form overlapped light and dark fringes which are reflected back to the microscope, and images are formed on a photosensitive element of the high-speed camera. By means of the observation equipment, observation of the full-axial and full-circumferential lubrication positions of the piston ring-cylinder sleeve friction pair can be achieved.

Description

TECHNICAL FIELD

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

[0002] In the lubrication system of a vehicle power engine, the piston ring-cylinder liner friction pair shoulders the responsibility of sealing and lubrication, and over-lubrication or poor lubrication can respectively cause problems such as excessive oil consumption and excessive wear of parts. Due to the combined effects of working conditions such as speed, temperature, gas pressure and lubricant rheological properties, the friction pair can be in various lubrication states such as boundary lubrication, mixed lubrication, thin film lubrication, micro-elastic-plastic fluid dynamic pressure lubrication and fluid dynamic pressure lubrication in different strokes of reciprocating motion. With the improvement of the emission standard of internal combustion engines, the control of its lubrication state will be more complex. In the research on the lubrication performance of the piston ring-cylinder liner friction pair, the oil film thickness is the most intuitive indicator for measuring the lubrication state, and relevant research results have attracted much attention from the academic and industrial circles. However, due to the high difficulty in measurement, experimental research is still lacking. Among various oil film thickness measurement methods, the ultrasonic method has the problem of low measurement accuracy, the fluorescence method has the problem of fluorescence quencher leading to inaccurate measurement and is difficult to apply in the measurement of whole machine large oil supply, and compared with the above two methods, the optical interference method has the characteristics of simple principle, small modification, low measurement lower limit and high resolution.

[0003] In the existing research on the measurement of oil film thickness by the optical interference method, the contact forms are mostly concentrated on point contact and line contact, and the contact area positions are mostly absolutely stationary. The principle of these test benches is that a motor drives a horizontal transparent plane disc to rotate, and a ball or a cylindrical roller contacts the disc from below under the drive of the motor, and an observation device is arranged above the disc. This test bench for researching the lubrication of components has the advantages of simple structure and low cost, and is suitable for carrying out mechanism research. In the few curved surface ring contact tests, the main research object is the lubrication law of sliding bearings. In this test bench, a transparent glass ring is fixed, a motor drives a sliding bearing to rotate on the inner surface of the glass ring, and a load can be loaded on the glass ring or the shaft. The contact area is still absolutely stationary. In fact, the contact area between the piston ring and the cylinder liner is in high-speed motion when the engine is working, and the observation device cannot follow the motion, which determines that the film thickness observation is faced with short exposure and low light intensity. Therefore, the traditional measurement scheme cannot be applied to the scene of dynamically shooting the high-speed moving piston ring-cylinder liner contact area.

[0004] In the existing optical interference method for measuring the thickness of the piston ring-cylinder liner oil film, the local piston ring is mostly cut, the transparent ring is used to replace the cylinder liner, and the two are relatively moved under the action of reciprocation or rotation to study the influence law of the speed and viscosity on the film thickness. However, this test bench is only suitable for comparing the performance of the parts and lubricating oil, and cannot consider the influence of the real internal combustion engine large stroke, oil injection system, crank connecting rod mechanism and other structures and operation parameters. In the bench test for measuring the film thickness, a hole is mostly punched on the internal combustion engine cylinder body and cylinder liner at a certain position of the piston ring, and then a transparent film-coated material with suitable size tolerance is installed on the hole to observe the lubricating film thickness at the position under different engine operating conditions. This method also has the following problems: first, due to the determination of the observation window, the oil film thickness at other positions in the axial and circumferential directions cannot be observed, which limits the study of the influence of the lateral force and the piston top structure on the lubrication law; second, the internal combustion engine test bench system is complex, and the strong turbulence and high pulsation gas caused by combustion have strong randomness, which has a great influence on the high-speed, multiphase flow coupling of the lubricating film thickness measurement; finally, the test bench is not universal and is difficult to disassemble and assemble, and is not suitable for testing the performance of the friction pair materials and lubricants.

[0005] The piston ring of the internal combustion engine is often designed to be in surface contact with the cylinder liner. The lubrication effect of surface contact is worse than that of point contact and line contact. In order to more truly study the lubrication effect of the surface contact piston ring in the internal combustion engine and further optimize the design of the friction pair materials and lubricating oil, the present application specially designs a piston ring-cylinder liner film thickness observation device based on the optical interference method. SUMMARY

[0006] The present application provides a piston ring-cylinder liner film thickness observation device based on the optical interference method, which can meet the observation requirements of the full axial and full circumferential lubrication positions of the piston ring-cylinder liner friction pair, and avoids the shortcomings of the test bench and the parts test.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following specific technical scheme: A piston ring-cylinder liner film thickness observation device based on the optical interference method, the observation device comprising a base, a main shaft motor, an oil sump, a crankshaft, a piston ring-cylinder liner assembly, a laser light source, a microscope and a high-speed camera. The main shaft motor and the oil sump 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; and the main shaft motor is used to drive the crankshaft to rotate. The piston ring-cylinder sleeve assembly comprises an upper cylinder sleeve, a cylinder body, a piston, a glass ring, a lower cylinder sleeve 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 sleeve, the glass ring and the lower cylinder sleeve are sequentially connected in a vertical direction from top to bottom to form a cylinder sleeve and are tightly fitted to the inner wall of the cylinder body; the piston is provided with a piston ring in sealing cooperation with the inner wall of the cylinder sleeve; the connecting rod is connected between the piston and the crankshaft; the cylinder body is provided with a 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 is arranged opposite to the glass ring in the window through a microscope; the laser emitted by the laser light source is vertically emitted to the glass ring through the objective lens of the microscope; the laser 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, forms the mutually superimposed bright and dark stripes reflected to the microscope, and forms an image 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, the number of interference stripes and the brightness information.

[0008] Further, the cylinder body is uniformly provided with four windows in a circumferential direction; The height of the window covers the entire stroke of the piston; The glass ring is located in the stroke of the piston.

[0009] Further, the oil pump motor, the oil pump and the oil storage tank are fixedly installed on the top of the base; The oil pump motor is used for driving the oil pump to work; The oil pump is used for pumping the lubricating oil in the oil sump into the oil storage tank and delivering the lubricating oil in the oil storage tank to the oil injection nozzle.

[0010] Further, the big end of the connecting rod is connected to the crankshaft in a loose fit, and the small end of the connecting rod is fixedly connected to the piston through the piston pin.

[0011] Further, the inner wall of the cylinder body is provided with a limiting flange for limiting the bottom end surface of the lower cylinder sleeve.

[0012] 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; the electric control system is installed on the base.

[0013] Further, the optical platform for supporting the high-speed camera, the microscope and the laser light source is further included.

[0014] Further, the cylinder body and the crankcase are connected through fasteners.

[0015] Further, the oil pump is a double oil pump.

[0016] Further, an 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; the electric control system is installed on the base.

[0017] Compared with the prior art, the technical scheme of the present application has the following beneficial effects: The observation device of the present application uses the upper cylinder sleeve, the glass ring and the lower cylinder sleeve connected in sequence from top to bottom to form a cylinder sleeve, uses the transparent coated glass ring with the same size precision to replace a section of the cylinder sleeve, and is provided with a window in the circumferential direction of the cylinder body, uses the high-speed camera and the microscope to observe the film thickness between the piston ring and the glass ring through the window after the laser is reflected on both sides of the oil film; the film thickness observation of the whole circumferential direction at a certain height can be realized by rotating the cylinder body, the height position of the glass ring is adjusted by installing the upper cylinder sleeve and the lower cylinder sleeve with different heights, so that the observation position changes in the stroke height direction, and the oil film thickness at any position of the whole stroke and the whole circumferential direction can be measured through multiple disassembly and measurement, so that the oil film thickness distribution of the whole stroke and the whole circumferential direction is established.

[0018] The observation device of the present application combines the high-speed camera and the laser interference technology to capture the dynamic contact area of high-frequency reciprocating motion, and researches the transformation of the piston ring-cylinder sleeve lubrication system under the coupling of various working conditions such as complex force field, multiphase flow and strong variable speed.

[0019] The observation device is convenient to disassemble and assemble, can simulate the real piston ring-cylinder sleeve lubrication condition, and avoids the influence of strong accidental differences caused by combustion on the film thickness measurement. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a three-dimensional view of the piston ring-cylinder sleeve film thickness observation device of the present application; Figure 2 It is an enlarged structural schematic view of the piston ring-cylinder sleeve assembly.

[0021] Reference signs: 1-main shaft motor; 2-electric control system; 3-oil pump motor; 4-oil pump; 5-oil storage tank; 6-oil pan; 7-crankshaft; 8-piston ring-cylinder sleeve assembly; 9-laser light source; 10-microscope; 11-high-speed camera; 12-upper cylinder sleeve; 13-cylinder body; 14-piston; 15-glass ring; 16-lower cylinder sleeve; 17-connecting rod. DETAILED DESCRIPTION

[0022] The technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0023] To address the challenges in measuring the oil film thickness of the piston ring-cylinder liner friction pair in internal combustion engines, this invention primarily solves the following technical problems: traditional experimental setups are biased towards observation of the static contact area, making them unsuitable for situations involving high-speed piston ring movement; component-level tests cannot simulate the effects of large-volume oil injection lubrication, piston 14, connecting rod 17, and other real parts, as well as reciprocating motion patterns on lubrication; bench tests cannot measure film thickness at locations other than the observation point, and the strong randomness of combustion airflow is detrimental to lubricant film measurement; bench tests lack versatility, are difficult to disassemble and assemble, and are unsuitable for testing the performance of friction pair materials and lubricants.

[0024] This invention provides a piston ring-cylinder liner film thickness observation device based on optical interferometry, such as... Figure 1 As shown in the diagram, the observation device includes a base (not shown), a main spindle motor 1, an oil pan 6, a crankcase (not shown), a crankshaft 7, a piston ring-cylinder liner assembly 8, a laser light source 9, a microscope 10, a high-speed camera 11, an oil pump motor 3, an oil pump 4, an oil reservoir 5, and an electronic control system 2; wherein: The base, serving as the foundation of the entire observation equipment, is located at the bottom of the equipment. The main spindle motor 1 and the oil pan 6 are both fixedly mounted on the base; a crankcase is fixedly mounted on the top of the oil pan 6; the main spindle motor 1 drives the crankshaft 7 to rotate. The crankshaft 7 is rotatably mounted in the crankcase. Specifically, both ends of the crankshaft 7 can be mounted in the crankcase via sliding bearings or rolling bearings, and are fixedly connected to the motor shaft of the main spindle motor 1 via couplings.

[0025] like Figure 2 As shown, the piston ring-cylinder liner assembly 8 includes 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 vertically oriented, and its bottom end is fixedly mounted to the top of the crankcase using fasteners. The cylinder body 13 and the crankcase can be connected by threads or by bolts, screws, or other fasteners. A flange for fixed connection to the crankcase can be provided at the bottom end of the cylinder body 13. The upper cylinder liner 12, glass ring 15, and lower cylinder liner 16 are sequentially connected vertically from top to bottom to form a cylinder liner, which is tightly fitted to the inner wall of the cylinder body 13. A limiting flange (not shown in the figure) is provided on the inner wall of the cylinder body 13 to limit the bottom end face of the lower cylinder liner 16. The piston 14 is provided with piston rings that seal against the inner wall of the cylinder liner. Connecting rod 17 connects piston 14 and crankshaft 7. The large end of connecting rod 17 is loosely fitted to crankshaft 7, and the small end of connecting rod 17 is fixedly connected to piston 14 via a piston pin. Connecting rod 17 converts the rotation of crankshaft 7 into reciprocating linear motion of piston 14 in the vertical direction. During the movement of piston 14, piston 14 and piston rings experience sliding friction with the cylinder liner, which is composed of upper cylinder liner 12, glass ring 15, and lower cylinder liner 16.

[0026] The cylinder 13 is provided with a window, which is a long strip-shaped opening arranged along the vertical direction and penetrating the wall thickness of the cylinder 13, so that light can be transmitted to directly view the internal glass ring 15. The cylinder 13 can be uniformly provided with four windows along the circumference. The height of the 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 window, so that the entire movement process of the piston 14 can be viewed through the window. The glass ring 15 is located within the stroke of the piston 14, and the height of the glass ring 15 can be half of the stroke of the piston 14. The inner surface of the glass ring 15 is provided with a layer of uniform chromium film.

[0027] The crankcase is provided with an oil injection nozzle for injecting lubricating oil to the piston 14 and the piston ring. The oil injection nozzle can inject lubricating oil to the dome of the piston 14 and between the piston 14 and the cylinder liner, so as to form a lubricating oil film between the piston 14 and the cylinder liner.

[0028] In order to provide the oil injection nozzle with lubricating oil of a predetermined pressure and flow rate, an oil pump motor 3, an oil pump 4 and an oil storage tank 5 are further 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 oil pump 4 through a shaft coupling, for driving the oil pump to work; the oil pump can be a double oil pump, for pumping the 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 injection nozzle.

[0029] The high-speed camera 11 is oppositely arranged with the glass ring 15 in the window through the microscope 10, so as to detect the lubricating oil film between the glass ring 15 and the piston 14 through the microscope 10, the 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-transmissive half-reflective lens can be arranged in the microscope 10, for reflecting the laser emitted by the laser light source 9, while transmitting the light reflected from the lubricating oil film to enter the high-speed camera 11. The laser 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, forming the mutually superimposed bright and dark stripes reflected to the microscope 10, and imaging on the photosensitive element of the high-speed camera 11, so as to determine the thickness of the oil film according to the wavelength of the laser, the number of interference stripes and the brightness information.

[0030] In order to realize the automatic control of the observation device, an electric control system 2 is further installed on the base, which 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.

[0031] In order to support the optical system, the observation device further comprises an optical platform for supporting the high-speed camera 11, the microscope 10 and the laser light source 9, which can be fixedly installed on the base and stably support the high-speed camera 11, the microscope 10 and the laser light source 9 through the optical platform.

[0032] The observation device uses the upper sleeve 12, the glass ring 15 and the lower sleeve 16 connected in sequence from top to bottom to form a sleeve, uses the transparent coated glass ring 15 with the same size precision to replace a section of the sleeve, and is provided with a window in the circumferential direction of the cylinder body 13, and the high-speed camera 11 and the microscope 10 are used to observe the interference light of the laser reflected on both sides of the oil film to measure the film thickness between the piston ring and the glass ring 15 through the window; the film thickness observation of the whole circumferential direction at a certain height can be realized by rotating the cylinder body 13, the height position of the glass ring 15 is adjusted by installing the upper sleeve 12 and the lower sleeve 16 with different heights, so as to realize the change of the observation position in the stroke height direction, and the oil film thickness at any position of the whole stroke and the whole circumferential direction can be measured through multiple disassembly and assembly measurements, so as to establish the oil film thickness distribution of the whole stroke and the whole circumferential direction.

[0033] The observation device can capture the dynamic contact area of high-frequency reciprocating motion by combining the high-speed photography and the laser interference technology, and study the transformation of the piston ring-cylinder sleeve lubrication system under the coupling of various working conditions such as complex force field, multiphase flow and strong variable speed.

[0034] The observation device is convenient to disassemble and assemble, can simulate the real piston ring-cylinder sleeve lubrication condition, and avoid the influence of strong accidental differences caused by combustion on the film thickness measurement.

[0035] The working principle of the observation device is that the inner surface of the glass ring 15 is coated with a uniform thin chromium film, when the piston ring passes through the inner surface of the glass ring 15, the lubricating oil film will fill the small gap between the piston ring-chromium film contact area; at this time, the objective lens of the external optical system will emit laser light perpendicular to the contact area, the laser light is reflected on the upper and lower surfaces of the oil film, i.e. the surface of the piston ring and the surface of the chromium film, and then interferes with each other, forms mutually superimposed bright and dark stripes, and reflects back to the observation system, and finally forms an image on the photosensitive element of the high-speed camera 11. According to the wavelength of the laser, the number of interference stripes and the brightness information, the oil film thickness can be determined.

[0036] The observation process of the observation 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 reciprocating motion of the piston 14 through the crankshaft 7 and the connecting rod 17, the piston 14 drives the piston ring to move and forms a dynamic contact area with the upper cylinder sleeve 12, the lower cylinder sleeve 16 and the glass ring 15. This dynamic contact area is rarely studied in the prior art. When the piston ring passes through the glass ring 15, the optical system composed of the light source, the camera and the microscope 10 starts to capture the bright and dark stripes, and the oil film thickness is calculated through post-processing data. By adjusting the height of the upper cylinder sleeve 12 and the lower cylinder sleeve 16, and rotating the cylinder body 13, the film thickness of the dynamic contact area in the whole axial and circumferential direction can be observed, and the influence of the lateral force of the piston ring on the lubrication of the piston ring is realized.

[0037] In operation, the oil pump motor 3 drives the oil pump to spray the lubricating oil in the oil storage tank 5 to the inner surface of the dome of the piston 14 or the cylinder sleeve, and the lubricating oil falls into the oil pan 6 under the action of gravity, and then the lubricating oil in the oil pan 6 is recovered to the oil storage tank 5 through the action of the oil pump to form a cycle.

[0038] 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.

[0039] 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 piston ring-cylinder liner film thickness observation device based on optical interferometry, characterized in that, Includes base, spindle motor, oil pan, crankshaft, piston ring-cylinder liner assembly, laser light source, microscope, and high-speed camera; The main spindle motor and oil pan are 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 main spindle motor is used to drive the crankshaft to rotate. The piston ring-cylinder liner assembly includes an upper cylinder liner, cylinder block, piston, glass ring, lower cylinder liner, and 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 window; the inner surface of the glass ring is provided with a thin chromium film; The crankcase is equipped with an oil injector for spraying lubricating oil onto the piston and piston rings; The high-speed camera is positioned opposite the glass ring inside the microscope window; the laser emitted by the laser source is directed perpendicularly to the glass ring through the objective lens of the microscope; the laser is reflected by the piston ring surface and the chromium film surface on both sides of the oil film and interferes with each other, forming superimposed bright and dark fringes reflected back to the microscope, and imaged on the photosensitive element of the high-speed camera. The thickness of the oil film is determined based on the wavelength of the laser, the order of the interference fringes and the brightness information.

2. The observation device as described in claim 1, characterized in that, The cylinder block has four windows evenly distributed around its circumference; The height of the window covers the entire stroke of the piston; The glass rings are located within the piston's stroke.

3. The observation device as described in claim 2, characterized in that, It also includes an oil pump motor, an oil pump, and an oil storage tank that are fixedly installed on the top of the base; The oil pump motor is used to drive the oil pump. The 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.

4. The observation device as described in claim 3, characterized in that, The big end of the connecting rod is loosely connected to the crankshaft, while the small end of the connecting rod is fixedly connected to the piston via a piston pin.

5. The observation device as described in claim 1, 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.

6. The observation device as described in claim 1, characterized in that, The crankshaft is mounted on the crankcase at both ends by sliding bearings and is fixedly connected to the motor shaft of the main shaft motor by a coupling.

7. The observation device as described in claim 1, characterized in that, It also includes optical platforms for supporting high-speed cameras, microscopes, and laser light sources.

8. The observation device as described in claim 1, characterized in that, The cylinder block and crankcase are connected by fasteners.

9. The observation device as described in claim 1, characterized in that, The oil pump is a dual oil pump.

10. The observation device according to any one of claims 1-9, characterized in that, It also includes the electrical control system for controlling the spindle motor, oil pump motor, laser light source and high-speed camera; the electrical control system is mounted on the base.

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