Method for observing thickness of plunger-bushing lubricating oil film of hydraulic rock drill

Abstract

The invention discloses a method for observing the thickness of a plunger-bushing lubricating oil film of a hydraulic rock drill. The observation method comprises the following steps: preparing equipment for observing the thickness of the plunger-bushing lubricating oil film; field-of-view calibration: 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 source are set, and it is ensured that the contact area can be shot within the set exposure time; and starting a motor, continuously collecting photos under a set working condition, and screening out the photos of the contact area. According to the observation method, non-contact, dynamic and high-precision observation and prediction of the oil film thickness can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine equipment, and particularly relates to a method for observing the lubricating oil film thickness of a plunger-bushing of a hydraulic rock drill. BACKGROUND

[0002] The working environment of a rock drill is usually harsh, such as high pressure, high speed, high frequency and strong vibration. As a key important part, the plunger-bushing friction pair often fails due to excessive wear, and thus is a key factor restricting the service life of the rock drill. The lubricating oil film, as an isolation medium between the friction pairs, undertakes the heavy task of lubrication, load bearing and wear resistance, and the thickness change of the lubricating oil film directly determines the friction state. However, the oil film thickness is usually in the nanometer to micrometer level, and its accurate measurement has always been a research hotspot and difficulty in the field of tribology and mechanical engineering.

[0003] At present, the measurement methods of the oil film thickness at home and abroad mainly focus on the following directions: 1. Electrical measurement is the earliest means applied to the monitoring of the oil film thickness, mainly including resistance method and capacitance method. The resistance method calculates the oil film thickness by using the resistance difference between the metal contact and the oil film isolation state, which is suitable for studying the boundary and mixed lubrication state. The capacitance method regards the oil film as a dielectric layer, and realizes the thickness estimation through the capacitance change, which has simple structure and is suitable for real-time monitoring. However, the electrical method is generally sensitive to the electrical conductivity and dielectric constant of the material, and has limited environmental adaptability.

[0004] 2. Optical interference method is one of the most accurate oil film measurement methods, and its resolution can reach nanometer level. The method uses the interference fringes formed by the reflection of light at the oil film and substrate interface to obtain the thickness distribution of the oil film. The optical method is widely used in academic research, such as the thickness distribution measurement of the elastohydrodynamic lubrication oil film. However, due to the need for transparent windows or special samples, its application in closed friction pairs (such as plunger pairs and bearing inner surfaces) is limited. The propagation characteristics of ultrasonic waves at the solid-liquid-solid interface are closely related to the thickness of the oil film. By analyzing the echo amplitude, phase or propagation time, the non-destructive detection of the oil film thickness can be realized.

[0005] 3. The ultrasonic method has the advantages of strong penetration, non-sensitivity to environmental light and suitability for in-situ measurement, and is especially suitable for oil film monitoring in high-pressure and strong-vibration environments, so it has become a research hotspot in recent years. However, this method has high requirements for sensor arrangement, signal processing algorithm and environmental noise suppression. The X-ray or neutron transmission method uses the absorption characteristics of the oil film to the X-ray or neutron to realize the thickness measurement. This method has the advantages of non-contact and high precision, but the test equipment is expensive and the experimental conditions are harsh, which is mainly limited to laboratory research and is difficult to promote to the engineering site.

[0006] Among the existing rock drill performance testing rigs, most testing equipment is geared towards research on the dynamics and vibration characteristics, durability and life testing, and hydraulic control strategy verification of rock drills. Research on lubrication testing of the plunger-bushing friction pair is still lacking.

[0007] In summary, to make the test conditions closer to the actual working conditions of a rock drill, this invention proposes a method for observing the thickness of the lubricating oil film between the plunger and bushing of a hydraulic rock drill, based on the optical interferometry method suitable for applied basic research. Summary of the Invention

[0008] This invention provides a method for observing the thickness of the lubricating oil film in the plunger-bushing of a hydraulic rock drill. This method enables non-contact, dynamic, and high-precision observation of the oil film thickness, with measurement accuracy down to the nanometer level and an upper limit of 1 micrometer.

[0009] To achieve the above objectives, the present invention adopts the following specific technical solution: A method for observing the thickness of the lubricating oil film between the plunger and bushing of a hydraulic rock drill, the method comprising the following steps: Step 1: Prepare the plunger-bushing lubricating oil film thickness observation equipment. This equipment includes a motor, motor base, base plate, oil pan, crankcase, crankshaft, plunger-bushing assembly, optical platform, laser source, high-speed camera, and microscope with objective lens. Step 2, field of view calibration: Install the microscope and laser 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 axis of the plunger movement, and align it with the window on the plunger-bushing assembly to ensure that the microscope can capture clear interference fringes. Step 4: Set the parameters for the high-speed camera and laser source to ensure that the contact area can be captured within the set exposure time; Step 5: Start the motor and begin continuously acquiring photos under the set operating conditions. Select photos of the contact area and determine whether the parameters set in Step 4 are reasonable based on the image quality. If not, return to Step 4 to reset the parameters.

[0010] Furthermore, it 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.

[0011] Furthermore, it also includes: Step 7: Integrate simulation. Based on the geometric structure and mechanical properties of each part in the plunger-bushing assembly, as well as the physicochemical properties of the lubricating oil, establish a theoretical model of the plunger ring-bushing friction pair under various lubrication conditions and iteratively solve the oil film thickness to form an "experiment-simulation" closed-loop verification system.

[0012] Furthermore, in step three, the specific method to ensure that the microscope can capture clear interference fringes is as follows: move the plunger, 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.

[0013] Furthermore, 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.

[0014] Furthermore, an oil pan and a motor are fixedly mounted on the base plate of the observation device; a crankcase is fixedly mounted on the top of the oil pan; the crankshaft is rotatably mounted in the crankcase; the motor is connected to the crankshaft drive to drive the crankshaft to rotate. The plunger-bushing assembly includes a cylinder block fixedly mounted at the bottom of the crankcase; a bushing bushing consisting of an upper bushing, a glass ring, and a lower bushing connected sequentially from top to bottom on the inner wall of the cylinder block; three annular grooves are spaced apart on the outer circumference of the plunger, with an upper oil baffle ring installed in the upper annular groove, a test ring installed in the middle annular groove, and a lower oil baffle ring installed in the lower annular groove; the upper oil baffle ring, the test ring, and the lower oil baffle ring form a plunger ring and are all clearance-fitted with the inner wall of the bushing bushing; a connecting rod connects the plunger and the crankshaft; the cylinder block has a window; and a thin chromium film is provided on the inner surface of the glass ring. The cylinder block is equipped with an oil supply nozzle for spraying lubricating oil onto the top of the plunger; The high-speed camera, microscope, and laser source are all mounted on an optical platform. The high-speed camera is positioned opposite the glass ring inside the window via the microscope. 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 off the test 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. These fringes are then 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.

[0015] Furthermore, the gaps between the upper and lower oil baffle rings and the inner wall of the bushing allow the space between the upper and lower oil baffle rings to be filled with lubricating oil.

[0016] Furthermore, the inner wall of the cylinder is provided with a retaining ring for limiting the bottom end face of the lower bushing.

[0017] Furthermore, the cylinder block has multiple windows evenly distributed circumferentially; The height of the window covers the piston's stroke. The glass ring is located within the plunger's stroke.

[0018] Furthermore, the observation equipment also includes an electronic control system for controlling the motors, laser source, and high-speed camera.

[0019] Furthermore, the observation device also includes a motor mount that is fixedly installed between the base plate and the motor.

[0020] Furthermore, the big end of the connecting rod is clearance-fitted with the crankshaft, while the small end of the connecting rod is fixedly connected to the plunger via a piston pin.

[0021] Furthermore, the two ends of the crankshaft are mounted to the crankcase via bearings and are fixedly connected to the output shaft of the motor via a coupling.

[0022] Furthermore, a flange is provided at the bottom of the cylinder block, and the flange is connected to the crankcase by fasteners.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The observation method of this invention utilizes a plunger-bushing lubricating oil film thickness observation device to observe the oil film thickness. This is achieved through steps such as field-of-view calibration, locating the dynamic contact area, setting parameters for the high-speed camera and laser light source, and continuous image acquisition. Using this equipment and these steps, the oil film thickness between the plunger ring and the bushing can be effectively measured, achieving film thickness measurement within any contact area at any location. The measurement accuracy can reach the nanometer level, with an upper limit of 1 micrometer. This observation method, combined with high-speed photography and laser interferometry, can capture the dynamic contact area undergoing high-frequency reciprocating motion, allowing for the study of the transformation of the plunger ring-bushing lubrication system under various coupled operating conditions such as complex force fields, multiphase flow, and strong speed variations.

[0024] The observation method employs an equipment within the cylinder consisting of an upper bushing, a glass ring, and a lower bushing connected sequentially from top to bottom. A section of the bushing at a specific location is replaced by a transparent, coated glass ring of the same size and precision. A window is provided circumferentially within the cylinder. An observation system comprised of a laser source, a high-speed camera, and a microscope observes the oil film thickness between the plunger ring and the glass ring through this window. By rotating the cylinder, the film thickness can be observed at a specific height along the entire circumference. Adjusting the height of the glass ring by installing upper and lower bushings at different heights allows for changes in the observation position along the plunger stroke height. Through repeated disassembly and measurement, the oil film thickness at any position along the entire stroke and circumference can be measured, establishing a full-height, full-circumference oil film thickness distribution.

[0025] The above-mentioned observation method utilizes optical interferometry to overcome the limitations of traditional electrical and ultrasonic methods in closed friction pairs. It achieves high-precision oil film thickness prediction by dynamically analyzing interference fringes. By controlling parameters such as crankshaft speed, temperature, pressure, and lubricating oil viscosity, it obtains the distribution and evolution of oil film thickness under different working conditions. The constructed observation equipment is suitable for studying the oil film thickness measurement of rock drill plunger-bushing friction pairs and can be used for friction pair material selection and lubrication scheme design, thereby improving the service life of rock drills. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method for observing the thickness of the lubricating oil film on the plunger-bulb of a hydraulic rock drill according to the present invention; Figure 2 This is a three-dimensional structural diagram of the observation equipment used in the observation method of the present invention; Figure 3 This is a schematic diagram of the plunger-bulb assembly. Figure 4 This is a schematic diagram illustrating the principle of measuring lubricating oil film thickness using interference rays in the observation method of this invention.

[0027] Figure label: 1-Motor; 2-Motor mount; 3-Base plate; 4-Oil pan; 5-Crankcase; 6-Plunger-bulb assembly; 7-Laser source; 8-Microscope; 9-High-speed camera; 10-Cylinder block; 11-Plunger; 12-Upper bushing; 13-Glass ring; 14-Lower bushing; 15-Upper oil baffle ring; 16-Test ring; 17-Lower oil baffle ring; 18-Connecting rod; 19-Lubricating oil; 20-Chromium film. Detailed Implementation

[0028] 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.

[0029] This invention provides a method for observing the thickness of the lubricating oil film on the plunger-bushing of a hydraulic rock drill, such as... Figure 1 As shown, the observation method includes the following steps: Step 1: Prepare the plunger-liner lubricating oil film thickness observation equipment, such as... Figure 2 and Figure 3As shown, the observation device includes a motor 1, a motor mount 2, a base plate 3, an oil pan 4, a crankcase 5, a crankshaft (not shown), a plunger-bulb assembly 6, an optical platform (not shown), a laser source 7, a high-speed camera 9, and a microscope 8 with an objective lens. The base plate 3 serves as the foundation of the entire observation device and is located at the bottom. The oil pan 4 and the motor 1 are fixedly mounted on the base plate 3. The crankcase 5 is fixedly mounted on the top of the oil pan 4, which collects the lubricating oil 19 from the lubricating plunger 11. The crankcase 5 is used to mount the crankshaft; both ends of the crankshaft are rotatably mounted on the crankcase 5 via bearings. The motor 1 is connected to the crankshaft via a coupling and is used to drive the crankshaft to rotate. To facilitate the installation of the motor 1 and the crankshaft, a motor mount 2 is fixedly mounted between the base plate 3 and the motor 1. The motor mount 2 is fixedly connected to the base plate 3 and provides a mounting base for the motor 1. Figure 3As shown, the plunger-bushing assembly 6 includes a cylinder body 10, a plunger 11, an upper bushing 12, a glass ring 13, a lower bushing 14, an upper oil baffle ring 15, a test ring 16, a lower oil baffle ring 17, and a connecting rod 18. The cylinder body 10 is arranged vertically, and its bottom end is fixedly installed on the top of the crankcase 5. A flange may be provided at the bottom end of the cylinder body 10, and the flange is detachably installed on the top of the crankcase 5 by fasteners. A bushing is loosely fitted on the inner wall of the cylinder body 10. The bushing is composed of an upper bushing 12, a glass ring 13, and a lower bushing 14 connected sequentially from top to bottom. A retaining ring (not shown in the figure) is provided on the inner wall of the cylinder body 10 to limit the bottom end face of the lower bushing 14. The retaining ring can also support the bottom end of the lower bushing 14. The inner diameter of the retaining ring is larger than the inner diameter of the lower bushing 14 to avoid the retaining ring affecting the reciprocating movement of the plunger 11. The outer circumferential surface of the plunger 11 is provided with three annular grooves at intervals. The three annular grooves are distributed vertically from top to bottom, namely the first annular groove on the upper side, the second annular groove in the middle, and the third annular groove on the lower side. An upper oil baffle ring 15 is installed in the first annular groove on the upper side, a test ring 16 is installed in the second annular groove in the middle, and a lower oil baffle ring 17 is installed in the third annular groove on the lower side. The upper oil baffle ring 15, test ring 16, and lower oil baffle ring 17 form plunger rings and are all clearance-fitted with the inner wall of the bushing. This ensures that there are gaps between the upper oil baffle ring 15 and the inner wall of the bushing, between the test ring 16 and the inner wall of the bushing, and between the lower oil baffle ring 17 and the inner wall of the bushing. Through design and calculation, by controlling the gaps between the upper oil baffle ring 15 and the inner wall of the bushing, and between the lower oil baffle ring 17 and the inner wall of the bushing, the space between the upper oil baffle ring 15 and the lower oil baffle ring 17 can be filled with lubricating oil 19. That is, when lubricating oil 19 is injected into the plunger 11 from the oil supply nozzle at the top of the plunger 11, the cavity between the upper oil baffle ring 15 and the lower oil baffle ring 17, where the test ring 16 is located, can be filled with lubricating oil 19. The cross-sectional shape of the upper oil baffle ring 15, test ring 16, and lower oil baffle ring 17 is rectangular. Connecting rod 18 connects the plunger 11 and the crankshaft. The large end of connecting rod 18 is clearance-fitted with the crankshaft, and the small end of connecting rod 18 is fixedly connected to the plunger 11 via a piston pin. Connecting rod 18 converts the rotation of the crankshaft driven by motor 1 into the reciprocating linear motion of the plunger 11 in the vertical direction. The cylinder block 10 has windows, which are elongated openings in the vertical direction that penetrate the wall thickness of the cylinder block 10, allowing light to pass through and directly revealing the upper oil baffle ring 15, test ring 16, and lower oil baffle ring 17 inside the glass ring 13. Multiple windows are evenly distributed circumferentially in the cylinder block 10, such as three or four. The height of the windows covers the stroke of the plunger 11; that is, the top dead center and bottom dead center of the plunger 11 are both within the height range of the windows. The glass ring 13 is located within the stroke of the plunger 11; that is, the glass ring 13 is located between the top dead center and bottom dead center of the plunger 11. A thin chromium film 20 is provided on the inner surface of the glass ring 13.The cylinder 10 is equipped with an oil supply nozzle for spraying lubricating oil 19 onto the top of the plunger 11. The oil supply nozzle can be connected to an oil pump via an oil pipe to obtain the required lubricating oil 19. The high-speed camera 9, microscope 8, and laser source 7 are all mounted on an optical platform. The optical platform supports the high-speed camera 9, microscope 8, and laser source 7. The optical platform can be a lifting platform fixedly mounted on the base plate 3. The high-speed camera 9 is positioned opposite the glass ring 13 in the window of the microscope 8, so that the thickness of the oil film between the test ring 16 and the glass ring 13 can be observed through the microscope 8, the window, and the glass ring 13. The laser emitted by the laser source 7 is directed perpendicularly to the glass ring 13 through the objective lens of the microscope 8. The light output direction of the laser source 7 is perpendicular to the optical axis of the microscope 8. In order to make the laser emitted by the laser source 7 directed perpendicularly to the glass ring 13, a semi-transparent mirror opposite to the laser source 7 can be set in the microscope 8 to reflect the laser emitted by the laser source 7 to the glass ring 13, while allowing the light reflected from the lubricating oil 19 film to pass through and enter the high-speed camera 9. The laser light is reflected from the surfaces of the test ring 16 and the chromium film 20 on both sides of the oil film, and then interferes with each other to form superimposed bright and dark fringes reflected back to the microscope 8. These fringes are then imaged on the photosensitive element of the high-speed camera 9. The thickness of the oil film is determined based on the wavelength of the laser light, the order of the interference fringes, and the brightness information. The observation device also includes an electrical control system for controlling the motor 1, the laser source 7, and the high-speed camera 9. The electrical control system can be fixedly installed on the base plate 3 and is connected to the motor 1, the laser source 7, and the high-speed camera 9 via signal connections.

[0030] The installation process of the plunger-bushing assembly 6 is as follows: First, the lower bushing 14 is installed into the cylinder 10 through the top opening of the cylinder 10, all the way to the bottom retaining ring. Then, the glass ring 13 is installed into the cylinder 10 in the same way until the bottom end face of the glass ring 13 contacts the top end face of the lower bushing 14. Finally, the upper bushing 12 is installed. The lower bushing 14, glass ring 13, and upper bushing 12 are loosely fitted with the cylinder 10. The upper oil retaining ring 15, test ring 16, and lower oil retaining ring 17 are installed into the three annular grooves of the plunger 11 in sequence. The gaps between the upper oil retaining ring 15, test ring 16, and lower oil retaining ring 17 and the bushing are very small. Finally, the plunger assembly formed by assembling the piston pin, connecting rod 18, plunger 11, upper oil retaining ring 15, test ring 16, and lower oil retaining ring 17 is installed from the direction of the lower bushing 14 using plunger 11 ring calipers.

[0031] The operation of the aforementioned observation equipment is as follows: Before the observation begins, the oil supply nozzle at the top of the cylinder block 10 will spray oil from the direction of the upper bushing 12 towards the top of the plunger 11. Since there are gaps between the upper baffle ring 15 and the bushing, between the test ring 16 and the bushing, and between the lower baffle ring 17 and the bushing, lubricating oil 19 will successively flow into the cavities between the upper baffle ring 15 and the test ring 16, and between the test ring 16 and the lower baffle ring 17, and finally flow out from the gap between the lower baffle ring 17 and the bushing. The design purpose of the upper baffle ring 15 and the lower baffle ring 17 is to fill the gaps between them and the test ring 16 with sufficient lubricating oil 19, so that the test ring 16 is in a fully lubricated state, thus simulating the lubrication state of the plunger-bushing friction pair in the hydraulic chamber. When motor 1 starts, plunger 11 drives the upper baffle ring 15, test ring 16, and lower baffle ring 17 to reciprocate. By controlling the oil injection quantity, the amount of oil flowing into the upper baffle ring 15 and the amount of oil flowing out of the lower baffle ring 17 are balanced. The oil film thickness at the position where the test ring 16 passes through the glass ring 13 is observed using an observation system. By adjusting the height of the upper and lower bushings 14 and the rotation of the bushings, the oil film thickness in the moving contact area in the entire axial and circumferential directions can be observed.

[0032] Step 2, field of view calibration: Install microscope 8 and laser source 7 onto the optical platform, connect high-speed camera 9 to microscope 8, adjust the distance between the photosensitive plane of high-speed camera 9 and microscope 8, and place a scale on the focal plane to calibrate the size of the camera's field of view.

[0033] Step 3: Locate the moving contact area, move the optical platform so that the axis of the microscope 8 is perpendicular to the axis of motion of the plunger 11, and align it with the window on the plunger-bushing assembly 6 to ensure that the microscope 8 can capture clear interference fringes. The specific method to ensure that the microscope 8 can capture clear interference fringes is as follows: move the plunger 11, and when the contact area passes through the field of view of the microscope 8, 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.

[0034] Step four involves setting the parameters of the high-speed camera 9 and the laser source 7 to ensure that the contact area can be captured within the set exposure time. Specifically, this includes calculating the time required for the contact area to traverse the field of view at the observation position based on the experimentally set speed, and adjusting the exposure time of the high-speed camera 9 and the power of the laser source 7 accordingly. The power of the laser source is adjusted to ensure that the contact area can be captured by the high-speed camera 9 within the set exposure time.

[0035] Step 5: Start motor 1 and begin continuously acquiring photos under the set operating conditions. Select photos of the contact area and determine whether the parameters set in Step 4 are reasonable based on the imaging quality. If not, return to Step 4 to reset the parameters.

[0036] 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 9, 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 to study the transformation mechanism of the plunger ring-bushing tribological state with different working parameters.

[0037] Step 7: Integrate simulation. Based on the geometric structure and mechanical properties of each part in the plunger-bushing assembly 6, as well as the physicochemical properties of the lubricating oil 19, establish a theoretical model of the plunger ring-bushing friction pair under various lubrication conditions and iteratively solve the oil film thickness, forming an "experiment-simulation" closed-loop verification system, which significantly improves the prediction accuracy and reliability of the lubricating oil film thickness of the hydraulic rock drill plunger-bushing.

[0038] The aforementioned observation method utilizes a piston ring-bushing lubricating oil film thickness observation device. Through field-of-view calibration, locating the dynamic contact area, setting parameters for the high-speed camera 9 and laser light source, and continuously acquiring photographs, the thickness of the lubricating oil film is observed. This method can effectively measure the oil film thickness between the piston ring and the bushing, achieving film thickness measurement within any contact area with nanometer-level accuracy and an upper limit of 1 micrometer. Combining high-speed photography and laser interferometry, this method can capture the dynamic contact area undergoing high-frequency reciprocating motion, allowing for the study of the transformation of the piston ring-bushing lubrication system under various coupled operating conditions such as complex force fields, multiphase flow, and strong speed variations.

[0039] The interference principle of the above observation methods is as follows: Figure 4 As shown, since the field of view of the high-speed camera 9 is very small, the curvature of the plunger ring and bushing can be ignored. Figure 4 Ignoring refraction at the solid-liquid interface during light propagation, incident rays 1 and 2 emitted from laser source 7 enter from different positions on the outer surface of glass ring 13 after passing through microscope 8. They are reflected from the surface of test ring 16 and the lower surface of chromium film 20, respectively (transmission of ray 2 is ignored). The reflected light interferes and superimposes to form ray 3, which returns to microscope 8 and is finally imaged on the photosensitive plane of high-speed camera 9. In practice, the oil film thickness between test ring 16 and bushing is typically at the nanometer level; therefore, a shorter wavelength light source such as visible light or ultraviolet light can be used. The actual measured oil film thickness information is contained in the longer path traveled by ray 1 compared to ray 2. Since light has wave properties, the interference ray 3 will show different brightness in high-speed camera 9 due to differences in oil film thickness. By calibrating the darkest and brightest values ​​of the interference rays based on different thicknesses, the oil film thickness can be calculated using the relative intensity method.

[0040] The observation process of the above observation method is as follows: After power is applied, the motor 1 drives the crankshaft to rotate under the control of the electronic control system, and converts the rotation of the crankshaft into the reciprocating motion of the plunger 11 through the crankshaft and connecting rod 18. The plunger 11 drives the plunger ring to move and forms a dynamic contact area with the upper bushing 12, the lower bushing 14 and the glass ring 13. The observation of this dynamic contact area is rarely studied in the existing technology. When the test ring 16 passes the glass ring 13, the optical system composed of the laser source 7, the high-speed camera 9 and the microscope 8 begins to capture the bright and dark stripes, and calculates the oil film thickness after subsequent data processing. By adjusting the height of the upper bushing 12 and the lower bushing 14 and rotating the cylinder block 10, the film thickness of the dynamic contact area in the entire axial and circumferential directions can be observed, realizing the study of the influence of the lateral force of the plunger ring on the lubrication of the plunger 11 ring. During operation, the oil supply nozzle sprays lubricating oil 19 onto the top of the plunger 11 and the inner surface of the bushing. Under the action of gravity, the lubricating oil 19 flows through the gap between the plunger 11 and the bushing and falls into the oil pan 4.

[0041] The observation equipment used in this method consists of an upper bushing 12, a glass ring 13, and a lower bushing 14 connected sequentially from top to bottom. A section of the bushing is replaced by a transparent coated glass ring 13 of the same size and precision. A window is provided around the cylinder body 10. A high-speed camera 9 and a microscope 8 are used to observe the interference light reflected from the oil film on both sides of the laser through the window to measure the film thickness between the piston ring and the glass ring 13. By rotating the cylinder body 10, film thickness observation can be achieved at a certain height in the entire circumference. By installing upper bushings 12 and lower bushings 14 at different heights, the height position of the glass ring 13 can be adjusted to achieve changes in the observation position along the stroke height direction. After multiple disassembly and measurement, the oil film thickness at any position in the entire stroke and circumference can be measured, thereby establishing the oil film thickness distribution in the entire stroke and circumference. This observation equipment is easy to disassemble and assemble, and can simulate the actual piston ring-bushing lubrication condition while avoiding the influence of strong random differences caused by combustion on the film thickness measurement.

[0042] The above observation method utilizes optical interferometry to overcome the limitations of traditional electrical and ultrasonic methods in closed friction pairs. It achieves high-precision oil film thickness prediction by dynamically analyzing interference fringes. By controlling parameters such as crankshaft speed, temperature, pressure, and lubricating oil viscosity, the distribution and evolution of oil film thickness under different working conditions can be obtained. The constructed film thickness observation equipment is suitable for studying the film thickness measurement of rock drill plunger-bushing friction pairs and can be used for friction pair material selection and lubrication scheme design, thereby improving the service life of rock drills.

[0043] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

[0044] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for observing the thickness of the lubricating oil film between the plunger and bushing of a hydraulic rock drill, characterized in that, Includes the following steps: Step 1: Prepare the plunger-bushing lubricating oil film thickness observation equipment. This equipment includes a motor, motor base, base plate, oil pan, crankcase, crankshaft, plunger-bushing assembly, optical platform, laser source, high-speed camera, and microscope with objective lens. Step 2, field of view calibration: Install the microscope and laser 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 axis of the plunger movement, and align it with the window on the plunger-bushing assembly to ensure that the microscope can capture clear interference fringes. Step 4: Set the parameters for the high-speed camera and laser source to ensure that the contact area can be captured within the set exposure time; Step 5: Start the motor and begin continuously acquiring photos under the set operating conditions. Select photos of the contact area and determine whether the parameters set in Step 4 are reasonable based on the image quality. If not, 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 plunger-bushing assembly, as well as the physicochemical properties of the lubricating oil, establish a theoretical model of the plunger ring-bushing friction pair under various lubrication conditions 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 plunger, 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, An oil pan and a motor are fixedly mounted on the base plate of the observation equipment; a crankcase is fixedly mounted on the top of the oil pan; the crankshaft is rotatably mounted in the crankcase; the motor is connected to the crankshaft drive and is used to drive the crankshaft to rotate. The plunger-bushing assembly includes a cylinder block fixedly mounted at the bottom to the top of the crankcase; a bushing consisting of an upper bushing, a glass ring, and a lower bushing connected sequentially from top to bottom is loosely fitted on the inner wall of the cylinder block; three annular grooves are spaced apart on the outer circumference of the plunger, with an upper oil baffle ring installed in the upper annular groove, a test ring installed in the middle annular groove, and a lower oil baffle ring installed in the lower annular groove; the upper oil baffle ring, the test ring, and the lower oil baffle ring form a plunger ring and are all clearance-fitted with the inner wall of the bushing; a connecting rod connects the plunger and the crankshaft; the cylinder block has a window; a thin chromium film is provided on the inner surface of the glass ring; The cylinder block is equipped with an oil supply nozzle for spraying lubricating oil onto the top of the plunger; The high-speed camera, microscope, and laser source are all mounted on an optical platform. The high-speed camera is positioned opposite the glass ring inside the window via the microscope. 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 off the test 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. These fringes are then 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.

7. The method for observing the thickness of the lubricating oil film on the plunger-bulb of a hydraulic rock drill as described in claim 6, characterized in that, The gaps between the upper and lower oil baffle rings and the inner wall of the bushing allow the space between the upper and lower oil baffle rings to be filled with lubricating oil.

8. The method for observing the thickness of the lubricating oil film on the plunger-bulb of a hydraulic rock drill as described in claim 6, characterized in that, The inner wall of the cylinder is provided with a retaining ring for limiting the bottom end face of the lower bushing.

9. The method for observing the thickness of the lubricating oil film on the plunger-bulb of a hydraulic rock drill as described in claim 6, characterized in that, The cylinder block has multiple windows evenly distributed circumferentially. The height of the window covers the piston's stroke. The glass ring is located within the plunger's stroke.

10. The method for observing the thickness of the lubricating oil film on the plunger-bulb of a hydraulic rock drill as described in claim 6, characterized in that, The observation equipment also includes an electronic control system for controlling the motors, laser source, and high-speed camera.

Images