A device and method for accurately measuring the coefficient of rolling friction

Abstract

This invention provides a device and method for accurately measuring the rolling friction coefficient. The device includes a frame; a test module comprising an upper sample plate, a movable plate, a lower sample plate, and a rolling friction pair; the lower sample plate is mounted on the frame base plate, and the movable plate and the upper sample plate are sequentially arranged on the lower sample plate; rolling friction pairs are arranged between the lower sample plate and the movable plate, and between the movable plate and the upper sample plate; a loading module is located above the test module and is used to apply a vertically downward load to the test module; a reciprocating motion module is located on the frame base plate and connected to the movable plate, and is used to drive the rolling friction pair to perform linear reciprocating rolling friction motion; and a positioning module is connected to the test module and is used to position and limit the test module, so that the upper sample plate, the movable plate, and the rolling friction pair are in a reference position. This invention eliminates the need for a test bearing and a cage. During the test, there is no relative motion other than rolling contact. The force measured by the tension / compression sensor is the rolling friction force. The measurement method is theoretically rigorous and yields accurate results.

Description

Technical Field

[0001] This invention relates to the field of rolling friction testing technology, and specifically to a device and method for accurately measuring the coefficient of rolling friction. Background Technology

[0002] Tribology is an interdisciplinary field involving materials science, mechanics, physics, chemistry, and other disciplines. It has a wide range of applications, strong practical relevance, and a rich theoretical framework. Rolling friction is a form of friction; compared to sliding friction, rolling friction has a lower coefficient of friction, allowing for more efficient torque transmission and support of rotational motion, as seen in the use of rolling bearings. However, currently, no mechanical equipment or device can accurately measure the coefficient of rolling friction.

[0003] Currently, rolling friction coefficient measuring devices use a rotating shaft to support the rolling contact of the sample, and a test bearing is installed on the rotating shaft. This leads to the frictional torque of the test bearing being mixed in with the measurement results. In practice, the rotating shaft is calibrated under no-load to remove the frictional torque of the test bearing from the measurement results. However, since the load on the rotating shaft is the same as that on the sample during the test, the frictional torque of the test bearing differs from that under no-load conditions. In addition, the lubricating oil temperature of the test bearing has a significant impact on its frictional torque, and it is impossible to guarantee that the lubrication state of the test bearing is completely consistent between no-load and test conditions. Therefore, the interference of the test bearing cannot be eliminated (e.g., the "Rolling Flow Friction and Wear Testing Machine" in Chinese Patent Publication No. CN107014708B). Furthermore, for test forms that use rolling bearings or other rolling elements, the sliding friction between the cage and the rolling elements, as well as the viscous resistance between the rolling elements and the lubricating oil, are also mixed in with the test results and cannot be eliminated.

[0004] Current rolling friction coefficient measuring devices or equipment cannot guarantee a single, pure rolling friction motion. The measurement results include resistance interference from other motions, and the degree of interference is related to the equipment structure. This leads to significant differences in measurement results when different devices measure the rolling friction coefficient of the same pair of components. Summary of the Invention

[0005] This invention provides a device and method for accurately measuring the rolling friction coefficient, aiming to overcome the shortcomings of existing rolling friction coefficient measurements, which suffer from numerous interfering factors that cannot be eliminated, resulting in inaccurate measurements.

[0006] The technical solution adopted to achieve the above-mentioned objectives is as follows:

[0007] The first aspect of the present invention provides a device for accurately measuring the coefficient of rolling friction, comprising:

[0008] Rack 1;

[0009] Test module 4 includes an upper sample plate 26, a movable plate 27, a lower sample plate 31, and a rolling friction pair. The lower sample plate 31 is mounted on the base plate of the frame 1, and the movable plate 27 and the upper sample plate 26 are sequentially arranged on the lower sample plate 31. The rolling friction pair is provided between the lower sample plate 31 and the movable plate 27, and between the movable plate 27 and the upper sample plate 26. The rolling friction pair includes a ball sample 28 and a block sample 29.

[0010] Loading module 3, which is disposed above the test module 4, is used to apply a vertically downward load to the test module 4;

[0011] The reciprocating motion module 5 is mounted on the base plate of the frame 1 and connected to the moving plate 27. It is used to drive the moving plate 27 to perform reciprocating linear motion, thereby causing the ball sample 28 to reciprocate and roll on the block sample 29.

[0012] Furthermore, the device also includes:

[0013] The installation positioning module 6 is connected to the test module 4 and is used to position and limit the test module 4 so that the upper sample plate 26, the moving plate 27 and the rolling friction pair are in the reference position.

[0014] Furthermore, the device also includes a loading module mounting plate 2, and the loading module 3 is fixed to the top plate or side wall of the frame 1 via the loading module mounting plate 2.

[0015] Furthermore, the loading module 3 includes an electric loading cylinder 10, a pressure sensor 13, and a loading plate 14. The electric loading cylinder 10 is vertically arranged, and the pressure sensor 13 is installed at the lower end of the electric loading cylinder 10. The loading plate 14 is arranged at the bottom of the pressure sensor 13. The lower surface of the loading plate 14 is provided with a spherical protrusion, and the spherical protrusion contacts the upper surface of the upper sample plate 26.

[0016] Furthermore, the lower sample plate 31 is provided with three first grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the lower sample plate 31. The three first grooves are respectively provided on two opposite sides of the lower sample plate 31.

[0017] The upper surface of the movable plate 27 is provided with three second grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate 27. The three second grooves are respectively provided on two opposite sides of the movable plate 27.

[0018] The lower surface of the movable plate 27 is provided with three third grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate 27. The three third grooves are respectively located on two opposite sides of the movable plate 27.

[0019] The lower surface of the upper sample plate 26 is provided with three fourth grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the upper sample plate 26. The three fourth grooves are respectively located on two opposite sides of the upper sample plate 26.

[0020] The axes of symmetry of the four isosceles triangles extend along the left and right sides of the test module 4. The first groove and the third groove are distributed in corresponding positions, and the second groove and the fourth groove are distributed in corresponding positions. The second groove and the third groove are symmetrically arranged on the upper and lower surfaces of the moving plate 27.

[0021] Each of the first groove, the second groove, the third groove and the fourth groove is respectively installed with one block sample 29. A ball sample 28 is placed on the block sample 29 on the lower sample plate 31 and on the block sample 29 on the upper surface of the moving plate 27.

[0022] The ball sample 28 and the block sample 29 are in contact to form a rolling friction pair, and the ball sample 28 can roll on the block sample 29 along the left and right sides of the test module 4.

[0023] The central axis direction of the lower sample plate 31 of the upper sample plate 26 and the moving plate 27 is the same as the direction of the reciprocating linear motion of the moving plate 27.

[0024] Furthermore, the ball sample 28 is a rolling ball, and the upper end of the block sample 29 has a concave arc surface 34, the axial direction of which extends along the left and right sides of the test module 4.

[0025] Furthermore, the ball sample 28 is a cylindrical roller, and the upper end of the block sample 29 is a plane.

[0026] Furthermore, the installation positioning module 6 includes a lower positioning block 35, an upper positioning block 36, and an upper plate limiting module 37;

[0027] The lower positioning block 35 is fixed on the base plate of the frame 1 and is used to position the ball sample 28 on the lower sample plate 31 and limit the movement of the moving plate 27.

[0028] The upper positioning block 36 is fixed on the left and right sides of the moving plate 27 and is used to position the ball sample 28 on the upper surface of the moving plate 27.

[0029] The upper plate limiting module 37 is fixed on the front and rear sides of the test module 4 and is used to position and limit the upper sample plate 26.

[0030] Furthermore, the reciprocating motion module 5 includes a ball screw linear reciprocating module 15, an adjusting shim group 16, a slider 17, a tension / compression sensor 20, and a U-shaped connecting rod 24;

[0031] The U-shaped connecting rod 24 is horizontally fixed to one end of the tension / compression sensor 20. The U-end of the U-shaped connecting rod 24 is provided with the slider 17. The other end of the tension / compression sensor 20 is fixedly connected to the moving plate 27 through the stud 18.

[0032] The adjusting shim group 16 is set on the base plate of the frame 1, and the ball screw linear reciprocating module 15 is set on it. The adjusting shim group 16 is used to adjust the height of the ball screw linear reciprocating module 15.

[0033] Among them, the ball screw linear reciprocating module 15 is a finished linear reciprocating mechanism composed of a servo motor and a ball screw. The ball screw rotates under the drive of the servo motor and drives the slider 17 to generate reciprocating linear motion.

[0034] A method for accurately measuring the coefficient of rolling friction, using the apparatus for accurately measuring the coefficient of rolling friction described in the first aspect of the present invention, the method comprising the following steps:

[0035] a. The rolling friction pair is installed on the test module 4, and the test module 4 is positioned and limited by the installation positioning module 6, so that the ball sample 28 between the moving plate 27 and the upper sample plate 26 is distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate 27.

[0036] The ball specimens 28 between the lower specimen plate 31 and the moving plate 27 are arranged in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27; the contact force on the ball specimens 28 between the moving plate 27 and the upper specimen plate 26 is the same as the contact force on the ball specimens 28 between the lower specimen plate 31 and the moving plate 27.

[0037] b. Fix the reciprocating motion module 5 to the moving plate 27 so that the tension / compression sensor 20 and the moving plate 27 are at the same horizontal position;

[0038] c. Place the spherical protrusion of the loading plate 14 on the upper sample plate 26, so that the loading point of the spherical protrusion is located at the centroid of the isosceles triangle formed by the spherical sample 28 between the lower sample plate 31 and the moving plate 27; start the loading module 3 to apply the load, and transfer the load to the test module 4 through the loading plate 14, and use the pressure sensor 13 to collect the load during the sample process.

[0039] d. Remove the mounting and positioning module 6;

[0040] e. Start the ball screw linear reciprocating module 15 to drive the moving plate 27 to perform a fixed-frequency, low-speed, uniform, short-distance linear reciprocating motion with a reciprocating distance of <10mm and a moving linear speed of <10mm / min, thereby realizing the rolling friction of the rolling friction pair. At the same time, the rolling friction force during the test is collected by the tension and pressure sensor 20.

[0041] f. Measure the rolling friction force F of the ball sample 28 when it is in the reference position using the tension / compression sensor 20, and measure the load P of the ball sample 28 when it is in the reference position using the pressure sensor 13. Calculate the rolling friction coefficient based on the rolling friction force F, the load, and the diameter of the ball sample 28.

[0042] The reference position refers to the following: the spherical specimens 28 between the moving plate 27 and the upper specimen plate 26 are distributed in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27; simultaneously, the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27 are also distributed in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27, and the loading point of the spherical protrusion of the loading plate 14 is located at the centroid of the isosceles triangle formed by the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27; the centroid of the isosceles triangle formed by the spherical specimens 28 between the moving plate 27 and the upper specimen plate 26 corresponds to the position of the centroid of the isosceles triangle formed by the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. This invention eliminates the need for a test bearing and cage. During the test, there is no relative motion other than rolling contact. The force measured by the tension / compression sensor is the rolling friction force, and the measurement method is theoretically rigorous. It can measure the rolling friction coefficient with and without lubricating oil, with different lubricating oils, and with different material combinations. Even when using lubricating oil, the low rolling speed negligibles the interference of lubricating oil viscous resistance, allowing for a more focused study of rolling friction as a distinct frictional behavior.

[0045] 2. This invention allows for testing with different sample sizes by changing the radius of curvature of the concave arc surface 34 of the block sample 29 or the diameter of the spherical sample 28. By machining the arc surface 34 of the block sample 29 into a flat plane and using cylindrical rollers for the spherical sample 28, tests with different contact patterns can be performed. Furthermore, the equipment is simple in structure, inexpensive, easy to operate, and provides accurate measurements.

[0046] 3. In the sample module of the present invention, there are 3 rolling friction pairs in one plane. The 3 points can define one plane, ensuring that the contact load of the 3 sets of friction pairs is consistent during the loading process, avoiding the influence of sample size tolerance on the contact load, thereby ensuring the stability of the contact system and the test process. Attached Figure Description

[0047] Figure 1 Overall structural diagram of the invention;

[0048] Figure 2 A schematic diagram of the overall structure of this invention (excluding the frame);

[0049] Figure 3 Loading module structure diagram;

[0050] Figure 4 Schematic diagram of the reciprocating motion module;

[0051] Figure 5 3D view of the reciprocating motion module;

[0052] Figure 6 Schematic diagram of the test module installation (including upper sample plate, moving plate, and lower sample plate);

[0053] Figure 7 Schematic diagram of the test module installation (including the movable plate and the lower sample plate);

[0054] Figure 8 Schematic diagram of the completed installation of the test module;

[0055] Figure 9 Bottom view of the assembled movable plate and block sample;

[0056] Figure 10 Top view of the assembled movable plate and block sample;

[0057] Figure 11 Top view of the upper sample plate and block sample assembly;

[0058] Figure 12 Top view of the upper sample plate and block sample assembly;

[0059] Figure 13 OK clip structure diagram;

[0060] Figure 14 Schematic diagram of the block sample shape;

[0061] Figure 15 Side view of the installation positioning module and test module assembly;

[0062] Figure 16 Main view of the assembly of the positioning module and the test module;

[0063] Figure 17 Schematic diagram of the shape of the upper positioning block;

[0064] Figure 18 Schematic diagram of the shape of the lower positioning block;

[0065] Figure 19 Schematic diagram of the upper plate limit module;

[0066] Explanation of reference numerals in the attached drawings: 1-Frame, 2-Loading module mounting plate, 3-Loading module, 4-Test module, 5-Reciprocating motion module, 6-Mounting and positioning module, 10-Electric loading cylinder, 13-Pressure sensor, 14-Loading plate, 15-Ball screw linear reciprocating module, 16-Adjusting shim group, 17-Slider, 18-Stud, 19-Second shim, 20-Tension / compression sensor, 22-First shim, 24-U-shaped connecting rod, 26-Upper sample plate, 27-Moving plate, 28-Ball sample, 29-Block sample, 30-OK clamp, 31-Lower sample plate, 34-Concave arc surface, 35-Lower positioning block, 36-Upper positioning block, 37-Upper plate limiting module, 39-Cylindrical magnet, 40-Upper plate limiting rod, 41-Boss, 42-Fifth groove. Detailed Implementation

[0067] The present invention will now be described in further detail with reference to the embodiments.

[0068] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the field or according to the product instructions. Materials or equipment whose manufacturers are not specified are all conventional products that can be obtained by purchase.

[0069] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” to another element, it can be directly connected to the other element, or there may be an intermediate element. Furthermore, the term “connected” as used herein can include wireless connections.

[0070] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. The terms "inner," "upper," "lower," "left and right," "front and back," etc., indicate the orientation or state relationship based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0071] Here, "left and right of the sample module" refers to the direction of the linear reciprocating motion of the moving plate, and "front and back of the sample module" refers to the direction perpendicular to the direction of the linear reciprocating motion of the moving plate. More specifically, the directions mentioned in the text refer to up, down, left, right, front, and back. Figure 1 , Figure 5 or Figure 16 The directions of the projection relationship are consistent in all directions: up, down, left, right, front, and back.

[0072] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "equipped with" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0073] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0074] like Figure 1 The device for accurately measuring the rolling friction coefficient described in this invention includes a frame 1, a loading module mounting plate 2, a loading module 3, a test module 4, a reciprocating motion module 5, and a mounting and positioning module 6.

[0075] The main body of the frame 1 is made of cast iron, which has good shock absorption performance and is used to support the various modules of the entire equipment.

[0076] The loading module mounting plate 2 is welded from steel plates. The loading module 3 is installed on the loading module mounting plate 2 by bolts. The loading module mounting plate 2 is installed on the top plate of the frame 1 by bolts.

[0077] The loading module 3 includes an electric loading cylinder 10, a pressure sensor 13, and a loading plate 14. The electric loading cylinder 10 is a finished electric loading cylinder composed of a servo motor and a ball screw. The electric loading cylinder 10 is vertically arranged, and the pressure sensor 13 is connected to the lower end of the electric loading cylinder 10 by a threaded connection. The loading plate 14 is fixed below the pressure sensor 13 by bolts.

[0078] The load generated by the electric loading cylinder 10 is transmitted to the test module 4 through the loading plate 14, and the pressure sensor 13 is used to measure the load generated by the electric loading cylinder 10.

[0079] A spherical protrusion is provided at the center of the lower end of the loading plate 14. The spherical protrusion contacts the middle of the upper surface of the upper sample plate 26. The spherical protrusion can prevent the loading from being skewed.

[0080] The test module 4 includes an upper sample plate 26, a movable plate 27, a lower sample plate 31, and 12 pairs of rolling friction pairs; the upper sample plate 26, the movable plate 27, and the lower sample plate 31 are used to install the rolling friction pairs and support the rolling friction of the friction pairs.

[0081] The lower sample plate 31 is installed in a groove on the base plate of the frame 1. The moving plate 27 and the upper sample plate 26 are sequentially arranged on the lower sample plate 31. Six pairs of rolling friction pairs are arranged between the lower sample plate 31 and the moving plate 27, and six pairs of rolling friction pairs are arranged between the moving plate 27 and the upper sample plate 26.

[0082] The lower sample plate 31 is provided with three first grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the lower sample plate 31. The three first grooves are respectively provided on two opposite sides of the lower sample plate 31; wherein, one first groove is provided on one side and two first grooves are provided on the opposite side.

[0083] The upper surface of the movable plate 27 is provided with three second grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate 27. The three second grooves are respectively provided on two opposite sides of the movable plate 27; wherein, one second groove is provided on one side and two second grooves are provided on the opposite side.

[0084] The lower surface of the movable plate 27 is provided with three third grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate 27. The three third grooves are respectively provided on two opposite sides of the movable plate 27; one third groove is provided on one side, and two third grooves are provided on the opposite side.

[0085] The lower surface of the upper sample plate 26 is provided with three fourth grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the upper sample plate 26. The three fourth grooves are respectively provided on two opposite sides of the upper sample plate 26; one fourth groove is provided on one side, and two fourth grooves are provided on the opposite side.

[0086] The axes of symmetry of the four isosceles triangles extend along the left and right sides of the test module 4. The first groove and the third groove are distributed in corresponding positions, and the second groove and the fourth groove are distributed in corresponding positions. The second groove and the third groove are symmetrically arranged on the upper and lower surfaces of the moving plate 27.

[0087] Each of the first groove, the second groove, the third groove and the fourth groove is respectively installed with one block sample 29. A ball sample 28 is placed on the block sample 29 on the lower sample plate 31 and on the block sample 29 on the upper surface of the moving plate 27.

[0088] The ball sample 28 and the block sample 29 are in contact to form a rolling friction pair, and the ball sample 28 can roll on the block sample 29 along the left and right sides of the test module 4.

[0089] The central axis direction of the lower sample plate 31 of the upper sample plate 26 and the moving plate 27 is the same as the direction of the reciprocating linear motion of the moving plate 27.

[0090] The ball sample 28 is a rolling ball, and the upper end of the block sample 29 has a concave arc surface 34, the axial direction of which extends along the left and right sides of the test module 4.

[0091] The block sample 29 is locked and fixed in the corresponding groove by the OK clamp 30.

[0092] The installation positioning module 6 includes a lower positioning block 35, an upper positioning block 36, and an upper plate limiting module 37.

[0093] The lower positioning block 35 is set on the left and right sides of the test module 4. The lower positioning block 35 is fixed to the base plate of the frame 1 by the OK clamp 30 and is used to position the ball sample 28 on the lower sample plate 31. A protrusion is provided on one side of the lower positioning block 35. The upper part of the side of the lower positioning block 35 with the protrusion is attached to the moving plate 27 to limit the movement of the moving plate 27.

[0094] Preferably, the lower sample 28 is a magnetic sphere, and the end of the protrusion of the lower positioning block 35 is provided with a cylindrical magnet 39. The cylindrical magnet 39 on the lower positioning block 35 is used to attract the spherical sample 28 above the lower sample plate 31 and position it.

[0095] At this time, the ball samples 28 on the lower sample plate 31 are distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate 27.

[0096] The upper positioning block 36 is fixed on the left and right sides of the moving plate 27 (i.e. the left and right sides of the test module 4) and is used to position and limit the ball sample 28 on the upper surface of the moving plate 27. The upper positioning block 36 is set with an inverted "L" shaped structure.

[0097] Preferably, the upper positioning block 36 is made of plastic, which is lightweight and easy to fix.

[0098] Preferably, the spherical sample 28 is a magnetic sphere, the block sample 29 is a magnetic block, and a cylindrical magnet 39 is provided on the vertical section of the upper positioning block 36. The vertical section of the upper positioning block 36 is fixed to the block sample 29 on the moving plate 27 by the cylindrical magnet 39 on the vertical section. A cylindrical magnet 39 is provided at the end of the horizontal section of the upper positioning block 36. The cylindrical magnet 39 on the horizontal section is used to attract the spherical sample 28 above the moving plate 27 and position it.

[0099] At this time, the ball samples 28 on the moving plate 27 are distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate 27.

[0100] The upper plate limiting module 37 is fixed on the front and rear sides of the test module 4 to fix the upper sample plate 26. The upper plate limiting module 37 has a base and an upper plate limiting rod 40 set on the base. The base is fixed on the bottom plate of the frame 1. A fifth groove 42 is provided on one side of the limiting rod. The upper sample plate 26 is provided with a boss 41 that cooperates with the fifth groove. The fifth groove and the boss 41 are in clearance fit for limiting the installation of the upper sample plate 26.

[0101] The reciprocating motion module 5 includes a ball screw linear reciprocating module 15, an adjusting shim group 16, a slider 17, a tension / compression sensor 20, and a U-shaped connecting rod 24;

[0102] A first washer 22 is provided between the U-shaped connecting rod 24 and the tension / compression sensor 20. The U-shaped connecting rod 24 is horizontally fixed to one end of the tension / compression sensor 20 by a stud and nut. The slider 17 is fixed to the U end of the U-shaped connecting rod 24 by bolts. The other end of the tension / compression sensor 20 is fixedly connected to the threaded hole 32 on the right side of the moving plate 27 by a stud 18. A second washer 19 is provided between the tension / compression sensor 20 and the moving plate 27.

[0103] The adjusting shim group 16 is set on the base plate of the frame 1, and the ball screw linear reciprocating module 15 is set on it. The adjusting shim group 16 is used to adjust the height of the ball screw linear reciprocating module 15.

[0104] The first gasket 22 can reduce the contact area between the tension / compression sensor 20 and the U-shaped connecting rod 24, making the connection between the two more secure and increasing the accuracy of the tension / compression sensor 20 measurement.

[0105] The second gasket 19 can reduce the contact area between the tension / compression sensor 20 and the moving plate 27, making the connection between the two more secure and increasing the accuracy of the tension / compression sensor 20 measurement.

[0106] Among them, the ball screw linear reciprocating module 15 is a finished linear reciprocating mechanism composed of a servo motor and a ball screw. The ball screw rotates under the drive of the servo motor and drives the slider 17 to generate reciprocating linear motion, which is transmitted to the test module 4 to drive the rolling friction pair to perform linear reciprocating rolling friction motion.

[0107] The adjusting shim group 16 is a combination of shims of different thicknesses. The shims are stacked to form different thicknesses, which are used to adjust the height of the ball screw linear reciprocating module 15.

[0108] As a preferred option, for non-magnetic spherical samples 28 and block samples 29, acrylic double-sided adhesive can be placed at the position of the cylindrical magnet 39 of the lower positioning block 35 and the upper positioning block 36 to achieve the effect of adsorbing the spherical sample 28 and installing the upper positioning block 36.

[0109] A method for accurately measuring the coefficient of rolling friction, using the aforementioned device for accurately measuring the coefficient of rolling friction, the method comprising the following steps:

[0110] The lower sample plate 31, with the block sample 29 installed, is placed into the square slot on the base plate of the frame 1 and locked in place using the OK clamp 30. Three ball samples 28 are placed in the middle of the concave arc surfaces 34 of the three block samples 29 in the lower sample plate 31. The three lower positioning blocks 35 are installed on the frame 1 using the OK clamp 30, and are pressed against the lower sample plate 31, with the ball samples 28 positioned close to the cylindrical magnets 39 on the lower positioning blocks 35. The moving plate 27, with the block sample 29 installed, is placed above the ball samples 28 located above the lower sample plate 31. Three upper positioning blocks 36 are installed on both sides of the moving plate 27. One ball sample 28 is placed in the middle of the concave arc surfaces 34 of the three block samples 29 on the moving plate 27, and the ball sample 28 is positioned close to the cylindrical magnets 39 on the upper positioning blocks 36. The three block samples 29 are then installed in the grooves of the upper sample plate 26 using the OK clamp 30. The upper sample plate 26, with the side of the block sample 29 mounted facing down, is placed above the spherical sample 28 located above the moving plate 27. The groove of the limiting rod engages with the protrusion 41 of the upper sample plate 26, causing the concave arc surface 34 of the block sample 29 on the upper sample plate 26 to contact the spherical sample 28 on the upper side of the moving plate 27, thus completing the installation. At this point, the moving plate 27 and the spherical sample 28 are in their reference positions. The upper surface of the upper sample plate 26 contacts the spherical protrusion of the loading plate 14, bearing the load applied by the loading module 3.

[0111] The reference position refers to the installation and positioning position of the six ball samples and the moving plate 27.

[0112] This equipment uses a total of 6 ball samples during operation, with 3 ball samples in each plane.

[0113] At the reference position, the three spheres in the same plane must meet the following two requirements:

[0114] 1. The three ball samples are arranged in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27.

[0115] 2. The loading position of the loading module is located on the axis of symmetry of the isosceles triangle described in 1. The distance from the left sphere along the central axis is L1, and the distance from the right sphere is L2, and L1 is twice L2.

[0116] Based on the lever principle, the load P at the reference position, and the contact force F experienced by the left spherical specimen. 左 The contact force F experienced by the spherical specimen on the right side 右 F satisfies the following relationship: 左 *L1=2*F 右 *L2. Because L1 is twice L2 at the reference position, therefore F 左 =F 右= 1 / 3 * P. At this point, the contact force on all six balls is the same. Only then can the frictional force generated during rolling be the same.

[0117] After the six ball samples and the moving plate are positioned by installing the positioning module, the six balls are in the reference position, and the position of the moving plate is its own reference position.

[0118] At the reference position, the spherical specimens 28 between the moving plate 27 and the upper specimen plate 26 are distributed in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27. Simultaneously, the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27 are also distributed in an isosceles triangle, with the base of the isosceles triangle perpendicular to the direction of the reciprocating linear motion of the moving plate 27. The loading point of the spherical protrusion of the loading plate 14 is located at the centroid of the isosceles triangle formed by the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27. The centroid of the isosceles triangle formed by the spherical specimens 28 between the moving plate 27 and the upper specimen plate 26 corresponds to the position of the centroid of the isosceles triangle formed by the spherical specimens 28 between the lower specimen plate 31 and the moving plate 27.

[0119] The tension / compression sensor 20 is installed into the threaded hole 32 of the movable plate 27 using studs and the second washer 19. The U-shaped connecting rod 24 is installed into the tension / compression sensor 20 using studs, the first washer 22, and the nut 23. The height of the ball screw linear reciprocating module 15 is adjusted by changing the thickness of the shims in the adjusting shim group 16. The position of the slider 17 is slightly adjusted by driving the ball screw linear reciprocating module 15. Then, the U-shaped connecting rod 24 is connected to the slider 17 with bolts and installed securely.

[0120] The electric loading cylinder 10 of the starting loading module 3 applies a load. After applying a certain load, the lower positioning block 35, the upper positioning block 36, and the corresponding OK clamp 30 are removed. The ball screw linear reciprocating module 15 is started, driving the moving plate 27 to perform a constant frequency, low speed, uniform speed, and short distance linear reciprocating motion (reciprocating distance < 10 mm, moving linear speed < 10 mm / min), realizing the rolling friction of 12 pairs of friction pairs consisting of 12 block samples 29 and 6 ball samples 28. At the same time, the rolling friction force during the test is collected by the tension and compression sensor 20. After several reciprocations, the reciprocating motion is stopped, and the ball screw linear reciprocating module 15 is driven to adjust the position of the moving plate 27. The lower positioning block 35 and the upper positioning block 36 are used to detect whether the ball sample 28 is also in the reference position when the moving plate 27 is in the reference position. If so, the test can be repeated; otherwise, the test module 4 needs to be reinstalled.

[0121] For ball specimens 28 and block specimens 29 of a certain size, the adjusting shim set 16 only needs to be adjusted during the first test. If the size of ball specimens 28 and block specimens 29 needs to be changed, the height of the ball screw linear reciprocating module 15 needs to be readjusted through the adjusting shim set 16. And the corresponding lower positioning block 35 and upper positioning block 36 should be replaced as needed to avoid interference during positioning.

[0122] There are three rolling friction pairs within a plane, and these three points define the plane, thus ensuring the stability of the contact system and the test process. The presence of three rolling friction pairs within a plane, with each pair defining a specific point, ensures consistent contact loads across the three sets of friction pairs during loading, avoiding the influence of specimen dimensional tolerances on the contact load.

[0123] Method for calculating rolling friction coefficient:

[0124] The unit of test load P is N; the dimensionless coefficient of friction f r ; dimensional coefficient of friction e, in mm; diameter D of the ball sample, in mm.

[0125] Rolling friction force F is measured in nanometers (N).

[0126] Rolling friction force during the test is collected using tension / compression sensor 20. When the moving plate 27 is in the leftmost and rightmost positions during its reciprocating motion (at this time, the ball specimen rolls along the concave arc surface 34 of the block specimen to the leftmost and rightmost positions), there is no relative movement between the ball specimen 28 and the block specimen 29, and the friction force is 0, that is, the rolling friction force collected by tension / compression sensor 20 is 0 (or at its lowest). Except for the initial moment, at the intermediate moment between two adjacent rolling friction force values ​​of 0 (or at its lowest), the ball specimen 28 and the block specimen 29 are located at the reference position.

[0127] The leftmost and rightmost positions refer to the positions of the ball sample and the moving plate during the reciprocating motion, which are the leftmost and rightmost edges of the reciprocating motion range. The leftmost and rightmost positions of the moving plate 27 during reciprocating motion are symmetrical with respect to the aforementioned reference positions.

[0128] During the reciprocating motion, the 12 pairs of friction pairs at the reference position experience completely identical forces. The coefficient of friction can be calculated based on the rolling friction force F, the normal load P, and the diameter D of the ball specimen at this moment. There are a total of 12 pairs of friction pairs during the test. Among them, the resultant horizontal resistance generated by the 6 pairs of friction pairs between the moving plate and the ball specimen is equal to the rolling friction force F. That is, each rolling contact point generates a horizontal resistance of F / 6.

[0129] 1. Dimensional coefficient of friction

[0130] According to the definition of the dimensional coefficient of rolling friction (Principles of Tribology, 2nd Edition, Wen Shizhu, Tsinghua University Press, 2002) and the force equilibrium of the ball sample, we know that: F / 6*D=e*(P / 3)*2. Therefore, e=F*D / 4P, and the units of e are consistent with the units of D.

[0131] 2. Dimensionless coefficient of friction

[0132] According to the definition of the dimensional coefficient of rolling friction (Principles of Tribology, 2nd Edition, Wen Shizhu, Tsinghua University Press, 2002), f can be calculated as follows: r =F / 6 / (P / 3)=2e / D.

[0133] Considering the influence of the weight of the components and the specimens themselves, the greater the difference between the total weight Q of the moving plate + six block specimens + six ball specimens and the load P, the smaller the difference in contact load between each rolling friction pair. When P ≥ 20 * Q, the difference in contact force between each rolling contact friction pair is ≤ 5%, which meets the general laboratory accuracy requirements.

[0134] The rolling friction pair of this invention can be freely replaced according to experimental needs. This allows for the measurement of the rolling friction coefficient of different rolling friction pairs based on experimental requirements, making it widely applicable. This invention can calculate the rolling friction coefficient of a single ball sample through measurement, thus realizing the determination of the rolling friction coefficient of a single rolling friction pair.

[0135] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for accurately measuring the coefficient of rolling friction, comprising the following steps: a. Install the rolling friction pair on the test module (4), and use the installation positioning module (6) to position and limit the test module (4) so ​​that the ball specimens (28) between the moving plate (27) and the upper sample plate (26) are distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate (27); make the ball specimens (28) between the lower sample plate (31) and the moving plate (27) distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate (27); make the contact force on the ball specimens (28) between the moving plate (27) and the upper sample plate (26) the same as the contact force on the ball specimens (28) between the lower sample plate (31) and the moving plate (27); b. Fix the reciprocating motion module (5) to the moving plate (27) so that the tension and compression sensor (20) and the moving plate (27) are at the same horizontal position; c. Place the spherical protrusion of the loading plate (14) on the upper sample plate (26), so that the loading point of the spherical protrusion is located at the centroid of the isosceles triangle formed by the spherical sample (28) between the lower sample plate (31) and the moving plate (27); start the loading module 3 to apply the load, and transfer the load to the test module (4) through the loading plate 14, and use the pressure sensor (13) to collect the load during the sample process. d. Remove the mounting and positioning module (6); e. Start the ball screw linear reciprocating module (15) to drive the moving plate (27) to perform a fixed frequency, low speed, uniform speed, short distance linear reciprocating motion. The reciprocating distance is <10mm and the moving linear speed is <10mm / min. This achieves rolling friction of the rolling friction pair. At the same time, the rolling friction force during the test is collected by the tension and pressure sensor (20). f. Measure the rolling friction force F of the ball sample (28) when it is in the reference position using the tension and compression sensor (20), and measure the load P of the ball sample (28) when it is in the reference position using the pressure sensor (13). Calculate the rolling friction coefficient based on the rolling friction force F, the load, and the diameter of the ball sample (28). in, The reference position refers to the following: the spherical specimens (28) between the moving plate (27) and the upper specimen plate (26) are distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate (27); at the same time, the spherical specimens (28) between the lower specimen plate (31) and the moving plate (27) are distributed in an isosceles triangle, and the base of the isosceles triangle is perpendicular to the direction of the reciprocating linear motion of the moving plate (27), and the loading point of the spherical protrusion of the loading plate (14) is located at the centroid of the isosceles triangle formed by the spherical specimens (28) between the lower specimen plate (31) and the moving plate (27); the centroid of the isosceles triangle formed by the spherical specimens (28) between the moving plate (27) and the upper specimen plate (26) corresponds to the position of the centroid of the isosceles triangle formed by the spherical specimens (28) between the lower specimen plate (31) and the moving plate (27).

2. The device for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 1, characterized in that, The device includes: Rack (1); The test module (4) includes an upper sample plate (26), a moving plate (27), a lower sample plate (31), and a rolling friction pair. The lower sample plate (31) is mounted on the base plate of the frame (1), and the moving plate (27) and the upper sample plate (26) are arranged sequentially on the lower sample plate (31). The rolling friction pair is provided between the lower sample plate (31) and the moving plate (27) and between the moving plate (27) and the upper sample plate (26). The rolling friction pair includes a ball sample (28) and a block sample (29). Loading module (3), which is disposed above the test module (4), is used to apply a vertically downward load to the test module (4); The reciprocating motion module (5) is set on the base plate of the frame (1) and connected to the moving plate (27) to drive the moving plate (27) to perform reciprocating linear motion, thereby causing the ball sample (28) to reciprocate and roll on the block sample (29).

3. The device for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 2, characterized in that, The device also includes: The installation positioning module (6) is connected to the test module (4) and is used to position and limit the test module (4) so ​​that the upper sample plate (26), the moving plate (27) and the rolling friction pair are in the reference position.

4. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 2, characterized in that, The device also includes a loading module mounting plate (2), and the loading module (3) is fixed to the top plate or side wall of the frame (1) via the loading module mounting plate (2).

5. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 2, characterized in that, The loading module (3) includes an electric loading cylinder (10), a pressure sensor (13) and a loading plate (14). The electric loading cylinder (10) is vertically arranged. The pressure sensor (13) is installed at the lower end of the electric loading cylinder (10). The loading plate (14) is arranged at the bottom of the pressure sensor (13). The lower surface of the loading plate (14) is provided with a spherical protrusion. The spherical protrusion is in contact with the upper surface of the upper sample plate (26).

6. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to any one of claims 2-5, characterized in that, The lower sample plate (31) is provided with three first grooves, which are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the lower sample plate (31). The three first grooves are respectively located on two opposite sides of the lower sample plate (31). The upper surface of the movable plate (27) is provided with three second grooves. The three second grooves are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate (27). The three second grooves are respectively located on two opposite sides of the movable plate (27). The lower surface of the movable plate (27) is provided with three third grooves. The three third grooves are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the movable plate (27). The three third grooves are respectively located on two opposite sides of the movable plate (27). The lower surface of the upper sample plate (26) is provided with three fourth grooves. The three fourth grooves are distributed in an isosceles triangle. The axis of symmetry of the isosceles triangle coincides with the central axis of the upper sample plate (26). The three fourth grooves are respectively located on two opposite sides of the upper sample plate (26). Among them, the axes of symmetry of the four isosceles triangles extend along the left and right sides of the test module (4), the first groove and the third groove are distributed in corresponding positions, the second groove and the fourth groove are distributed in corresponding positions, and the second groove and the third groove are symmetrically arranged on the upper and lower surfaces of the moving plate (27). Each of the first groove, the second groove, the third groove and the fourth groove is respectively equipped with a block sample (29), and a ball sample (28) is placed on the block sample (29) on the lower sample plate (31) and on the block sample (29) on the upper surface of the moving plate (27). The ball sample (28) and the block sample (29) are in contact to form a rolling friction pair, and the ball sample (28) can roll on the block sample (29) along the left and right sides of the test module (4). The central axis of the lower sample plate (31) of the upper sample plate (26) and the moving plate (27) is in the same direction as the reciprocating linear motion of the moving plate (27).

7. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 6, characterized in that, The ball specimen (28) is a rolling ball, and the upper end of the block specimen (29) has a concave arc surface (34), the axial direction of which extends along the left and right sides of the test module (4).

8. The device for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to claim 7, characterized in that, The ball sample (28) is a cylindrical roller, and the upper end of the block sample (29) is a plane.

9. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to any one of claims 3, characterized in that, The installation positioning module (6) includes a lower positioning block (35), an upper positioning block (36), and an upper plate limiting module (37). The lower positioning block (35) is fixed on the bottom plate of the frame (1) and is used to position the ball sample (28) on the lower sample plate (31) and limit the movement plate (27). The upper positioning block (36) is fixed on the left and right sides of the moving plate (27) and is used to position the ball sample (28) on the upper surface of the moving plate (27). The upper plate limiting module (37) is fixed on the front and rear sides of the test module (4) and is used to position and limit the upper sample plate (26).

10. The apparatus for accurately measuring the rolling friction coefficient used in the method for accurately measuring the rolling friction coefficient according to any one of claims 3, characterized in that, The reciprocating motion module (5) includes a ball screw linear reciprocating module (15), an adjusting shim group (16), a slider (17), a tension and compression sensor (20), and a U-shaped connecting rod (24). The U-shaped connecting rod (24) is horizontally fixed at one end of the tension and compression sensor (20). The U end of the U-shaped connecting rod (24) is provided with the slider (17). The other end of the tension and compression sensor (20) is fixedly connected to the moving plate (27) through a stud (18). The adjusting shim group (16) is set on the bottom plate of the frame (1), and the ball screw linear reciprocating module (15) is set on it. The adjusting shim group (16) is used to adjust the height of the ball screw linear reciprocating module (15). Among them, the ball screw linear reciprocating module (15) is a finished linear reciprocating mechanism composed of a servo motor and a ball screw. The ball screw rotates under the drive of the servo motor and drives the slider (17) to generate reciprocating linear motion.

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