A device and test method for measuring friction characteristics of eccentric cam of methanol engine

Abstract

The invention relates to the technical field of methanol engines, and in particular to a device and a testing method for measuring the friction characteristics of an eccentric cam of a methanol engine. The device comprises a chassis, a base is arranged at the middle position of the upper end surface of the chassis, a main shaft sleeve is sleeved on the base, a cavity is arranged inside the main shaft sleeve, a rolling ball is arranged in the cavity between the machine base and the main shaft sleeve, a friction arm is arranged outside the main shaft sleeve, a friction force sensor is also arranged on the upper end surface of the chassis, the friction force sensor is arranged corresponding to the position of the friction force arm, abuts against the friction force arm to prevent it from moving, a rocker arm unit is arranged on the upper end surface of the main shaft sleeve, the rocker arm unit is fixedly installed on the main shaft sleeve through a cover plate, and a driving motor is also included, an eccentric cam is arranged on the output shaft of the driving motor, the eccentric cam and the rocker arm unit are in contact to form a contact pair, and the problem that the working conditions of the eccentric cam of the valve mechanism of the methanol engine at the current stage are extremely complex, making numerical and experimental research very difficult is solved.

Description

Technical Field

[0001] The invention relates to the technical field of methanol engines, and in particular to a device and a testing method for measuring friction characteristics of an eccentric cam of a methanol engine. Background Art

[0002] Among various engine products, methanol engine is one of the thermal engines with the highest thermal efficiency at present. It is widely used in various types of power machinery. Its performance level is largely affected by the friction performance of its own moving pairs. The eccentric cam of the valve mechanism is the contact pair that is most sensitive to the anti-wear properties of lubricating oil in the methanol engine. It usually works under harsh working conditions. The load, suction speed and geometric shape of its contact area are constantly changing. If the contact pair is poorly lubricated, it will directly lead to imbalance of the intake and exhaust mechanisms of the internal combustion engine, reduce the thermal efficiency of the internal combustion engine, and even cause safety accidents when the wear is severe. However, due to the extremely complex working conditions of the eccentric cam of the valve mechanism (transient working conditions, thermal effects and system dynamics, etc.), numerical and experimental research is very difficult.

[0003] In summary, the present invention proposes a device and a test method for measuring the friction characteristics of the eccentric cam of a methanol engine, which solves the problem of measuring the friction characteristics of the eccentric cam of the valve mechanism under different operating parameters of the methanol engine. Summary of the invention

[0004] The purpose of the present invention is to provide a device and a test method for measuring the friction characteristics of the eccentric cam of a methanol engine to solve the problem that the working conditions of the eccentric cam of the valve mechanism of a methanol engine at this stage are extremely complex, making numerical and experimental research very difficult.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A device for measuring the friction characteristics of an eccentric cam of a methanol engine comprises a chassis, a base is arranged at the middle position of the upper end surface of the chassis, a main shaft sleeve is sleeved on the base, a cavity is arranged inside the main shaft sleeve, a rolling ball is arranged in the cavity between the base and the main shaft sleeve, a friction arm is arranged outside the main shaft sleeve, a friction force sensor is also arranged on the upper end surface of the chassis, the friction force sensor is arranged corresponding to the position of the friction force arm, abuts against the friction force arm to prevent it from moving, a rocker arm unit is arranged on the upper end surface of the main shaft sleeve, the rocker arm unit is fixedly mounted on the main shaft sleeve through a cover plate, and also comprises a drive motor, an eccentric cam is arranged on the output shaft of the drive motor, and the eccentric cam and the rocker arm unit are in contact to form a contact pair.

[0006] It is further defined that the friction arm includes a left friction arm and a right friction arm, and the left friction arm and the right friction arm are respectively arranged on the left and right sides of the outer side of the main shaft sleeve, and the friction sensors are respectively a left friction sensor and a right friction sensor, the left friction sensor is installed at the rear of the left friction arm and abuts against the left friction arm, and the right friction sensor is installed in front of the right friction arm and abuts against the right friction arm, and the left friction sensor and the right friction sensor limit the rotational movement of the left friction arm and the right friction arm.

[0007] It is further defined that the rocker arm unit is a sapphire disk, the sapphire disk and the cover plate are provided with through holes, the upper end surface of the main shaft sleeve is provided with threaded holes, and bolts pass through the through holes and threaded holes to connect the cover plate and the sapphire disk with the main shaft sleeve.

[0008] It is further defined that the base is in the shape of a boss, the bottom of the main shaft sleeve is open, the cavity inside the main shaft sleeve is in an inverted concave shape, corresponding to the boss-shaped base, the main shaft sleeve is invertedly sleeved on the base, and the inverted concave cavity matches the boss-shaped base.

[0009] It is further defined that the rolling ball is arranged between the two sides of the raised part of the boss-shaped base and the inner wall of the concave cavity Further definition, wherein the contact pair friction force is f, the rotation radius of the sapphire disk is L, the measurement value of the left friction sensor is F1, the measurement value of the right friction sensor is F2, the distance between the left friction arm and the center of the chassis is L1, the distance between the right friction arm and the center of the chassis is L2, the eccentric cam sets the speed through the driving motor, when the eccentric cam starts to rotate, the contact pair friction force f will apply a driving torque to the sapphire disk, because the sapphire disk, the main shaft sleeve and the left friction arm and the right friction arm connected to the main shaft sleeve are fixed, the main shaft sleeve and the left friction arm and the right friction arm will transmit the friction torque of the sapphire disk to the left friction sensor and the right friction sensor, so that the friction force under different eccentric cam rotation angles can be measured, and the calculation formula is as follows: f=(F1*L1+F2*L2) / L It is further defined that the sapphire disk has a diameter of 150 mm, a thickness of 1 mm, and a refractive index of 1.762; the eccentric cam is a steel ball with G5 precision and a diameter of 25.4 mm. The surface roughness of the sapphire disk and the steel ball are approximately 1.4 nm and 14.0 nm, respectively. The test conditions are as follows: the cam speeds are 18 / (r·min-1), 36 / (r·min-1), 54 / (r·min-1), 96 / (r·min-1) and 144 / (r·min-1), respectively; the initial loads are 10 / N, 20 / N and 40 / N, the oil supply is sufficient, the eccentricity is 1 mm or 2 mm, the ambient temperature is 23°C±1°C, and the lubricating oils are PAO10, PAO20 and PAO40, and the dynamic viscosities at 23°C are 113.9 mPa·s, 321.0 mPa·s and 855.7 mPa·s, respectively.

[0010] It is further defined that the test steps are as follows: in the preparation stage, the left friction sensor and the right friction sensor are calibrated, and the calibration method is: standard weights of different masses are placed on the left friction sensor and the right friction sensor respectively, and the digital voltage signals converted by the data acquisition device are collected, and the digital voltage signals under the corresponding load are averaged; after measuring multiple groups of data of the left friction sensor and the right friction sensor, the digital voltage signal is used as the horizontal coordinate and the load is used as the vertical coordinate to fit the linear function curves between the digital voltage signals and the loads corresponding to the two sensors respectively, and the corresponding function relationship is written into the program to complete the calibration. Before the test, the eccentric cam is marked with a micrometer, and the cam angle is set to the 0° position when the rotation center of the eccentric cam is closest to the surface of the sapphire disk.

[0011] The beneficial effects of the present invention compared to the current technology are: The mechanical structure is relatively simple. The friction characteristics of the eccentric cam of the valve mechanism under various parameters such as cam speed, initial load, lubricating oil viscosity and eccentricity make the experimental research relatively simple, and solve the problem of measuring the friction characteristics of the eccentric cam of the valve mechanism under different operating parameters of the methanol engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the three-dimensional structure of the present invention Figure 2 A schematic top view of the present invention Figure 3 for Figure 2 CC section view Figure 4 Schematic diagram of the eccentric cam Figure 5 The curve of friction coefficient changing with cam angle under different eccentricity The markings in the figure correspond respectively to: 1-chassis, 2-main shaft sleeve, 3-base, 4-ball, 5-left friction arm, 6-right friction arm, 7-left friction sensor, 8-right friction sensor, 9-rocker arm unit, 10-cover plate, 11-drive motor, 12-bolt, 13-eccentric cam. DETAILED DESCRIPTION

[0013] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. Example

[0014] like Figure 1-Figure 5 As shown, a device for measuring the friction characteristics of an eccentric cam of a methanol engine comprises a chassis 1 and a main shaft sleeve 2. A base 3 is arranged in the middle position of the upper end surface of the chassis 1. The base 3 is in a boss shape. The main shaft sleeve 2 is open at the bottom and has a cavity arranged inside. The cavity is in an inverted concave shape, corresponding to the boss-shaped base 3. The main shaft sleeve 2 is invertedly sleeved on the base 3. The inverted concave cavity matches the boss-shaped base 3. Rolling balls 4 are arranged between the two sides of the convex part of the boss-shaped base 3 and the inner wall of the concave cavity. The left and right sides of the outer side of the main shaft sleeve 2 are respectively arranged with a left friction arm 5 and a right friction arm 6. The upper end surface of the chassis 1 is also provided with a A left friction sensor 7 and a right friction sensor 8 are arranged, the left friction sensor 7 is installed at the rear of the left friction arm 5 and abuts against the left friction arm 5, and the right friction sensor 8 is installed in front of the right friction arm 6 and abuts against the right friction arm 6. The left friction sensor 7 and the right friction sensor 8 limit the rotational movement of the left friction arm 5 and the right friction arm 6. It also includes a rocker unit 9, a cover plate 10 and a drive motor 11. The rocker unit 9 is a sapphire disk. Through holes are set on the sapphire disk and the cover plate 10. A threaded hole is provided on the upper end surface of the sleeve 2, and bolts 12 pass through the through holes and the threaded holes to connect the cover plate 10 and the sapphire disk to the main sleeve 2. An eccentric cam 13 is provided on the output shaft of the drive motor 11. The eccentric cam 13 and the sapphire disk are in contact to form a contact pair. The friction force of the contact pair is f, the rotation radius of the sapphire disk is L, the measurement value of the left friction sensor 7 is F1, the measurement value of the right friction sensor 8 is F2, the distance between the left friction arm 5 and the center of the chassis is L1, and the distance between the right friction arm 6 and the center of the chassis is L 2. The eccentric cam 12 sets the speed through the driving motor 11. When the eccentric cam 12 starts to rotate, the contact pair friction force f will apply a driving torque to the sapphire disk. Since the sapphire disk, the main shaft sleeve 2, and the left friction arm 5 and the right friction arm 6 connected to the main shaft sleeve 2 are fixed, the main shaft sleeve 2 and the left friction arm 5 and the right friction arm 6 will transmit the friction torque received by the sapphire disk to the left friction force sensor 7 and the right friction force sensor 8, so that the friction force under different rotation angles of the eccentric cam 12 can be measured. The calculation formula is as follows: f=(F1*L1+F2*L2) / L Among them, the sapphire disk has a diameter of 150 mm, a thickness of 1 mm, and a refractive index of 1.762; the eccentric cam 12 is a steel ball with G5 precision and a diameter of 25.4 mm. The surface roughness of the sapphire disk and the steel ball are approximately 1.4 nm and 14.0 nm, respectively. The test conditions are as follows: the cam speeds are 18 / (r·min-1), 36 / (r·min-1), 54 / (r·min-1), 96 / (r·min-1) and 144 / (r·min-1), respectively, the initial loads are 10 / N, 20 / N and 40 / N, the oil supply is sufficient, the eccentricity is 1 mm or 2 mm, the ambient temperature is 23℃±1℃, the lubricating oils are PAO10, PAO20 and PAO40, and the dynamic viscosities at 23℃ are 113.9 mPa·s, 321.0 mPa·s and 855.7 mPa·s, respectively; the test steps are as follows: In the preparation stage, the left friction sensor 7 and the right friction sensor 8 are calibrated. The calibration method is as follows: standard weights of different masses (10.0 g ~ 910.5 g) are placed on the left friction sensor 7 and the right friction sensor 8 respectively, and the digital voltage signals converted by the data acquisition device are collected, and the digital voltage signals under the corresponding load are averaged; after measuring multiple groups of data of the left friction sensor 7 and the right friction sensor 8, the digital voltage signal is used as the horizontal coordinate and the load is used as the vertical coordinate to fit the linear function curves between the digital voltage signals and the loads corresponding to the two sensors respectively, and the corresponding function relationship is written into the program to complete the calibration. Before the test, the eccentric cam 13 is marked by a micrometer, and when the rotation center of the eccentric cam 13 is closest to the surface of the sapphire disk, the cam angle is set to 0°. Figure 4 In the figure, O1 is the center of the steel ball, O2 is the rotation center of the eccentric cam 13, and the eccentricity of the cam is e.

[0015] The research on the friction pair characteristics of the eccentric cam 13 of the valve mechanism using the contact form of the eccentric cam 13 and the sapphire disk shows that the change of the eccentricity of the eccentric cam 13 causes the cam sliding speed, contact area load and sliding-rolling ratio to change accordingly. The change of the friction coefficient caused by the increase of the eccentricity is mainly determined by the sliding-rolling state. Under the premise that the overall material of the eccentric cam 13 is the same, appropriately increasing the initial load can improve the reliability; under the premise of meeting the needs, the smaller the eccentricity of the eccentric cam 13, the smaller the friction loss and the more reliable the structure.

[0016] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0017] The above is a detailed introduction to a device and a test method for measuring the friction characteristics of the eccentric cam of a methanol engine provided by the present invention. The description of the specific embodiment is only used to help understand the method and its core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A device for measuring the friction characteristics of an eccentric cam of a methanol engine, comprising a chassis (1), characterized in that: A base (3) is provided at a middle position of the upper end surface of the chassis (1), a main shaft sleeve (2) is sleeved on the base (3), a cavity is provided inside the main shaft sleeve (2), a rolling ball (4) is provided in the cavity between the base (3) and the main shaft sleeve (2), a friction arm is provided outside the main shaft sleeve (2), a friction force sensor is also provided on the upper end surface of the chassis (1), the friction force sensor is provided at a position corresponding to the friction force arm, abuts against the friction force arm to prevent it from moving, a rocker unit (9) is provided on the upper end surface of the main shaft sleeve (2), the rocker unit (9) is fixedly mounted on the main shaft sleeve (2) through a cover plate (10), and also includes a drive motor (11), an eccentric cam (13) is provided on the output shaft of the drive motor (11), and the eccentric cam (13) and the rocker unit (9) are in contact with each other to form a contact pair.

2. The device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 1, characterized in that: The friction arm comprises a left friction arm (5) and a right friction arm (6), the left friction arm (5) and the right friction arm (6) being respectively arranged on the left and right sides of the outer side of the main shaft sleeve (2), the friction sensors being respectively a left friction sensor (7) and a right friction sensor (8), the left friction sensor (7) being installed at the rear of the left friction arm (5) and abutting against the left friction arm (5), the right friction sensor (8) being installed at the front of the right friction arm (6) and abutting against the right friction arm (6), the left friction sensor (7) and the right friction sensor (8) limiting the rotational movement of the left friction arm (5) and the right friction arm (6).

3. The device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 2, characterized in that: The rocker arm unit (9) is a sapphire disk, the sapphire disk and the cover plate (10) are both provided with through holes, the upper end surface of the main shaft sleeve (2) is provided with a threaded hole, and the bolts (12) pass through the through holes and the threaded holes to connect the cover plate (10) and the sapphire disk to the main shaft sleeve (2).

4. The device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 1, characterized in that: The base (3) is convex, the main shaft sleeve (2) is open at the bottom, the cavity inside the main shaft sleeve (2) is inverted concave, corresponding to the convex base (3), the main shaft sleeve (2) is invertedly sleeved on the base (3), and the inverted concave cavity matches the convex base (3).

5. The device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 4, characterized in that: The rolling balls (4) are arranged between the two sides of the raised portion of the boss-shaped base (3) and the inner wall of the concave cavity.

6. The testing method of the device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 3, characterized in that: in, The friction force of the contact pair is f, the rotation radius of the sapphire disk is L, the measurement value of the left friction sensor (7) is F1, the measurement value of the right friction sensor (8) is F2, the distance between the left friction arm (5) and the center of the chassis (1) is L1, and the distance between the right friction arm (6) and the center of the chassis (1) is L2. The eccentric cam (13) is set to rotate at a speed by the driving motor (11). When the eccentric cam (11) starts to rotate, the friction force f of the contact pair will apply a driving torque to the sapphire disk. Since the sapphire disk, the main shaft sleeve (2) and the left friction arm (5) and the right friction arm (6) connected to the main shaft sleeve (2) are fixed, the main shaft sleeve (2) and the left friction arm (5) and the right friction arm (6) will transmit the friction torque received by the sapphire disk to the left friction sensor (7) and the right friction sensor (8), so that the friction force under different rotation angles of the eccentric cam (12) can be measured. The calculation formula is as follows: f=(F1*L1+F2*L2) / L.

7. The testing method of the device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 6, characterized in that: The sapphire disk has a diameter of 150 mm, a thickness of 1 mm, and a refractive index of 1.762; the eccentric cam (13) is a steel ball with a G5 precision and a diameter of 25.4 mm. The surface roughness of the sapphire disk and the steel ball are approximately 1.4 nm and 14.0 nm, respectively. The test conditions are as follows: The cam speeds are 18 / (r·min-1), 36 / (r·min-1), 54 / (r·min-1), 96 / (r·min-1) and 144 / (r·min-1), respectively. The initial loads are 10 / N, 20 / N and 40 / N, the oil supply is full, the eccentricity is 1mm or 2mm, the ambient temperature is 23℃±1℃, and the lubricating oils are PAO10, PAO20 and PAO40, and the dynamic viscosities at 23℃ are 113.9 mPa·s, 321.0mPa·s and 855.7mPa·s, respectively.

8. The testing method of the device for measuring the friction characteristics of the eccentric cam of a methanol engine according to claim 7, characterized in that: The test steps are as follows: in the preparation stage, the left friction sensor (7) and the right friction sensor (8) are calibrated, and the calibration method is as follows: standard weights of different masses are placed on the left friction sensor (7) and the right friction sensor (8), respectively, and the digital voltage signals converted by the data acquisition device are collected, and the digital voltage signals under the corresponding load are averaged; after measuring multiple sets of data of the left friction sensor (7) and the right friction sensor (8), the digital voltage signal is used as the horizontal coordinate and the load is used as the vertical coordinate to fit the linear function curves between the digital voltage signals and the loads corresponding to the two sensors, and the corresponding function relationship is written into the program to complete the calibration. Before the test, the eccentric cam (13) is marked by a micrometer, and when the rotation center of the eccentric cam (13) is closest to the surface of the sapphire disk, the cam angle is set to the 0° position.

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