CN114544484B - Test device and method for measuring static friction coefficient of tire - Google Patents
Test device and method for measuring static friction coefficient of tire Download PDFInfo
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- CN114544484B CN114544484B CN202210440621.6A CN202210440621A CN114544484B CN 114544484 B CN114544484 B CN 114544484B CN 202210440621 A CN202210440621 A CN 202210440621A CN 114544484 B CN114544484 B CN 114544484B
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- 230000003068 static effect Effects 0.000 title claims abstract description 143
- 238000012360 testing method Methods 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000005259 measurement Methods 0.000 claims abstract description 47
- 238000006073 displacement reaction Methods 0.000 claims description 10
- 238000012935 Averaging Methods 0.000 claims description 4
- 238000004458 analytical method Methods 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 4
- 239000004814 polyurethane Substances 0.000 description 19
- 229920002635 polyurethane Polymers 0.000 description 19
- 239000000463 material Substances 0.000 description 17
- 229910000831 Steel Inorganic materials 0.000 description 9
- 230000008859 change Effects 0.000 description 9
- 239000010959 steel Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 238000003860 storage Methods 0.000 description 7
- 230000008569 process Effects 0.000 description 5
- 229910000838 Al alloy Inorganic materials 0.000 description 4
- 230000009471 action Effects 0.000 description 4
- 230000009194 climbing Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000001179 sorption measurement Methods 0.000 description 4
- 238000005507 spraying Methods 0.000 description 3
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000002783 friction material Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000004154 testing of material Methods 0.000 description 2
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
- G01N19/02—Measuring coefficient of friction between materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M17/00—Testing of vehicles
- G01M17/007—Wheeled or endless-tracked vehicles
- G01M17/02—Tyres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M17/00—Testing of vehicles
- G01M17/007—Wheeled or endless-tracked vehicles
- G01M17/02—Tyres
- G01M17/021—Tyre supporting devices, e.g. chucks
Abstract
The application provides a test device and a method for measuring static friction coefficient of a tire, and the test device comprises a measuring device, a tension assembly and a computer system, wherein the measuring device comprises a first flat plate, a second flat plate, a third flat plate, a screw, a pressure sensor and a U-shaped plate. The positive pressure can be applied to the tire to be tested by screwing the nuts at the joints of the first flat plate, the third flat plate and the screw, and the pressure between the second flat plate and the third flat plate can be measured by the pressure sensor. And the tension component applies tension far away from the U-shaped plate to the screw rod until the first flat plate, the second flat plate and the tire to be tested move relatively. And the computer system receives the pressure value data sent by the pressure sensor and the measurement data sent by the tension assembly in real time, and analyzes and calculates to obtain the static friction coefficient of the tire to be measured.
Description
Technical Field
The invention relates to the field of material measurement, in particular to a test device and a method for measuring a static friction coefficient of a tire.
Background
Friction is the most common phenomenon in industrial manufacturing processes, and causes uneven deformation, wear, slippage and the like of mechanical parts, thereby having great influence on the working performance and service life of the mechanical parts. With the continuous improvement of the use requirements of mechanical parts, various performance parameters are increasingly accurate, and the measurement of the static friction coefficient becomes the inevitable requirement of test representation.
In a static friction coefficient testing machine on the market at present, before measuring the static friction coefficient of a material, the material is firstly made into a sample size required by the static friction coefficient testing machine, and then the static friction coefficient of the material is measured. The static friction coefficient of the tire cannot be directly measured. For example, at present, the automatic equipment wall-climbing robot for removing paint from large storage tanks at home and abroad has two basic functions: adsorption function and walking function on the steel wall surface. The wall-climbing robot drives the polyurethane tire to walk on the outer wall surface of the storage tank, the hub of the polyurethane tire is made of aluminum alloy, and the hub is coated with polyurethane with a certain thickness. The wall climbing robot has various states on the wall surface of the petrochemical storage tank, such as vertical, horizontal and oblique movement. In order to ensure that the wall-climbing robot is reliably adsorbed on the steel wall surface of the storage tank, the wall-climbing robot in different states needs to be subjected to stress analysis, and one important force is the static friction force of the polyurethane tire and the steel plate under the water and non-water conditions.
By utilizing a static friction coefficient testing machine on the market at present, a polyurethane material needs to be manufactured into a sample size required by the static friction coefficient testing machine before the static friction coefficient of the material is measured, the friction testing machine needs to be purchased in a department with the friction material testing machine or by oneself for testing, the material consumption is high, the time and the labor are wasted, the static friction coefficient of the polyurethane material can only be measured, and the static friction coefficient of the whole polyurethane tire under the real working condition environment cannot be reduced to the maximum extent.
Disclosure of Invention
The application provides a test device and a method for measuring the static friction coefficient of a tire, which are used for measuring the static friction coefficients of tires made of different materials under different states on the premise of not changing the size of the materials, thereby ensuring the accuracy and the authenticity of the research on the static friction coefficient of the tire.
In a first aspect, the application provides a test device for measuring a static friction coefficient of a tire, which comprises a measuring device, a tension assembly and a computer system, wherein the measuring device comprises a first flat plate, a second flat plate, a third flat plate, a screw, a pressure sensor and a U-shaped plate.
The first flat plate, the second flat plate and the third flat plate are parallel to each other and are provided with first through holes; the screw rod sequentially penetrates through the corresponding first through holes in the first flat plate, the second flat plate and the third flat plate; the first flat plate and the third flat plate are respectively fastened with the screw through first nuts.
A tire to be tested is placed between the first flat plate and the second flat plate; the first flat plate and the second flat plate are tangent to the outer circumference of the tire to be tested; the pressure sensor is connected between the second flat plate and the third flat plate; the pressure sensor is used for measuring the pressure value between the second flat plate and the third flat plate when the first nut is screwed down.
The U-shaped plate comprises a bottom plate and two side plates; connecting shafts are respectively arranged on the opposite inner walls of the two side plates; one end of the connecting shaft penetrates through the inner wall of the side plate and is fastened through a second nut; the other end of the connecting shaft is detachably connected with the hub of the tire to be tested.
The screw rod is connected with the tension assembly, and the tension assembly is used for applying tension far away from the U-shaped plate to the screw rod until the first flat plate, the second flat plate and the tire to be tested move relatively.
The computer system is configured to receive pressure value data sent by the pressure sensor and measurement data sent by the tension assembly in real time, and analyze and calculate the static friction coefficient of the tire to be measured; the measurement data comprises the tension applied to the screw by the tension component and the displacement of the screw.
In some embodiments, the tensile assembly is an electronic universal tester;
the electronic universal testing machine comprises an upper cross beam and a lower cross beam; the measuring device is arranged between the upper cross beam and the lower cross beam;
the screw is connected with the upper cross beam;
the bottom plate is connected with the lower cross beam.
In some embodiments, a first pin boss is disposed on the screw; a first pin shaft seat matched with the first pin shaft sleeve is arranged on the upper cross beam; a second pin shaft sleeve is arranged on the bottom plate; and a second pin shaft seat matched with the second pin shaft sleeve is arranged on the lower cross beam.
In some embodiments, the first through hole is formed in a center of one side of each of the first, second, and third flat plates.
In some embodiments, the first plate, the second plate and the third plate are symmetrically provided with the first through holes by taking a plate middle line as a symmetry axis.
In some embodiments, the pressure sensor has a centerline aligned with the centerline of the tire under test.
In a second aspect, the present application provides a method of measuring a static coefficient of friction of a tire, comprising:
acquiring pressure value data sent by a pressure sensor, wherein the pressure value data is a pressure value between a second flat plate and a third flat plate when a first nut is screwed down;
acquiring measurement data which is sent by a tension component and corresponds to the pressure value data, wherein the measurement data comprises tension loaded on a screw by the tension component and displacement of the screw;
and analyzing and calculating according to the acquired pressure value data and the acquired measurement data to obtain the static friction coefficient of the tire to be measured.
In some embodiments, the step of obtaining the static friction coefficient of the tire to be tested by performing analysis calculation according to the acquired pressure value data and the acquired measurement data includes:
analyzing according to the measurement data to obtain a maximum tension value of the tire to be measured, wherein the maximum tension value is a tension value of a critical point of relative movement of the first flat plate, the second flat plate and the tire to be measured;
calculating the maximum tension value to obtain the maximum static friction force corresponding to the pressure value borne by the tire to be tested;
and calculating according to the maximum static friction force and the pressure value data to obtain a static friction coefficient of the tire to be measured, wherein the static friction coefficient is the ratio of the maximum static friction force to the pressure value data.
In some embodiments, the measurement data corresponds to a tensile force value at least one time point, and the pressure value data corresponds to a pressure value at the same time point as a critical point at which relative movement occurs between the first plate, the second plate, and the tire under test.
In some embodiments, calculating according to the maximum static friction force and the pressure value data to obtain a static friction coefficient of the tire to be measured, where the static friction coefficient is a ratio of the maximum static friction force to the pressure value data, further includes:
and averaging a plurality of ratios of the maximum static friction force to the pressure value data to obtain the static friction coefficient.
According to the technical scheme, the test device and the method for measuring the static friction coefficient of the tire comprise a measuring device, a tension assembly and a computer system, wherein the measuring device comprises a first flat plate, a second flat plate, a third flat plate, a screw, a pressure sensor and a U-shaped plate. The positive pressure can be applied to the tire to be tested by screwing the nuts at the joints of the first flat plate, the third flat plate and the screw, and the pressure between the second flat plate and the third flat plate can be measured by the pressure sensor. And the tension component applies tension far away from the U-shaped plate to the screw rod until the first flat plate, the second flat plate and the tire to be tested move relatively. And the computer system receives the pressure value data sent by the pressure sensor and the measurement data sent by the tension assembly in real time, and analyzes and calculates to obtain the static friction coefficient of the tire to be measured.
Compared with the prior art, the technical scheme has the following beneficial effects:
1. this application pulling force subassembly adopts electron universal tester, through combining with electron universal tester, has realized accurate, stable pulling force control.
2. The computer system receives pressure value data sent by the pressure sensor and measurement data sent by the tension assembly in real time, and analyzes and calculates to obtain the static friction coefficient of the tire to be measured. The data is traceable, and the measurement precision is high. The sensitivity of the tire changing from a static state to a motion state between the flat plates is greatly improved, the accurate measurement of the relative movement starting action between the tire and the contact surface is realized, and the measurement reliability of the static friction coefficient is improved.
3. This application can change the pressure between dull and stereotyped and the tire that awaits measuring through adjusting first nut through setting up first nut in first flat board, third flat board and screw rod junction, and the tire that awaits measuring receives positive pressure promptly to can measure the coefficient of static friction under the different positive pressures.
4. According to the tire static friction coefficient measuring device, the first nuts at the joints of the first flat plate, the third flat plate and the screw rod are completely loosened, the first flat plate and the second flat plate move on the screw rod, the distance between the first flat plate and the second flat plate can be adjusted, the static friction coefficient of tires with different diameters can be measured, and the adaptability to the diameters of the tires is strong.
5. This application is through changing a small amount of parts such as U template, connecting axle, and the static coefficient of friction of the tire of measurable quantity different width is stronger to the adaptability of tire width.
Drawings
Fig. 1 is a schematic structural diagram of a wall-climbing robot according to an embodiment of the present disclosure;
FIG. 2 is a schematic structural diagram of a testing apparatus for measuring a static friction coefficient of a tire according to an embodiment of the present disclosure;
FIG. 3 is a schematic structural diagram of a measuring device in a testing apparatus for measuring a static friction coefficient of a tire according to an embodiment of the present disclosure;
FIG. 4 is a structural side view of a measuring device in a testing device for measuring static friction coefficient of a tire according to an embodiment of the present application;
FIG. 5 is a flow chart of a method for measuring static coefficient of friction of a tire according to an embodiment of the present disclosure;
FIG. 6 is a flow chart of a method for providing analytical calculations of the pressure value data and the measurement data according to an embodiment of the present application.
Detailed Description
Friction is the most common phenomenon in industrial manufacturing processes, and causes uneven deformation, wear, slippage and the like of mechanical parts, thereby having great influence on the working performance and service life of the mechanical parts. With the continuous improvement of the use requirements of mechanical parts, various performance parameters are increasingly accurate, and the measurement of the static friction coefficient becomes the inevitable requirements of test representation.
At present, the automatic paint removing equipment for large-sized storage tanks at home and abroad mainly focuses on the aspect of wall-climbing robots. The wall climbing robot has two basic functions: adsorption function and walking function on the steel wall surface. The adsorption function of the wall-climbing robot is realized through the adsorption force between the permanent magnet and a steel plate material, and the walking function is realized through the motor-driven tire. Fig. 1 is a schematic structural diagram of the wall-climbing robot. Comprises a body frame 5, a spray disk 6, a walking part 7 and the like. The spraying plate 6 is positioned in the middle of the wall-climbing robot, the walking part 7 is divided into a left part and a right part, and the spraying plate 6, the walking part 7 and the like are connected into a whole through the body frame 5. Taking the right side traveling unit 7 as an example, the traveling unit 7 mainly includes components such as a urethane tire 71, a motor and speed reducer 72, and a permanent magnet 73. The wall-climbing robot is attracted to the outer wall surface of the storage tank by the attraction force between the permanent magnet 73 and the steel plate to perform operation, and has various states such as vertical, horizontal and oblique states. The wall-climbing robot is connected with a polyurethane tire 71 through a motor and a speed reducer 72, the polyurethane tire 71 is driven to walk on the outer wall surface of the storage tank, a hub of the polyurethane tire 71 is made of aluminum alloy, and polyurethane with a certain thickness is coated outside the hub. In order to ensure that the wall climbing robot is reliably adsorbed on the wall surface, the wall climbing robot in different states needs to be subjected to stress analysis, one important force is the static friction force of the polyurethane tire 71 and the steel plate under the working conditions of water and no water, the value of the static friction force is related to the positive pressure and changes along with the change of the value of the positive pressure, and under the same working condition, the static friction coefficient is constant. Therefore, the static friction force can be characterized by a static friction coefficient.
However, because the hub of the polyurethane tire is made of aluminum alloy, and the polyurethane with a certain thickness is wrapped on the outer radial side of the aluminum alloy hub, the existing measurement method is adopted, the polyurethane material is required to be processed into the sample size required by the friction material testing machine, the material consumption is high, the time and the labor are wasted, the static friction coefficient of the polyurethane material can only be measured, and the static friction coefficient of the whole polyurethane tire under the real working condition environment cannot be reduced to the maximum extent.
In order to solve the problems, the application provides a test device for measuring the static friction coefficient of a tire, which can measure the static friction coefficient of the tire under different working condition environments such as water and no water on the premise of not changing the size of a material.
As shown in fig. 2, 3 and 4, the testing device for measuring the static friction coefficient of a tire provided by the present application comprises a measuring device 1, a tension assembly 2 and a computer system 3, wherein the measuring device 1 comprises a first flat plate 11, a second flat plate 12 and a third flat plate 13, a screw 14, a pressure sensor 15 and a U-shaped plate 16.
The first flat plate 11, the second flat plate 12 and the third flat plate 13 are parallel to each other and are provided with first through holes 140; in this embodiment, the first flat plate 11, the second flat plate 12, and the third flat plate 13 have the same shape, material, and surface roughness, so as to ensure that the contact surfaces of the tire to be measured and the flat plates have the same roughness, thereby improving the accuracy of the measured friction coefficient.
The screw 14 sequentially penetrates through the corresponding first through holes 140 on the first flat plate 11, the second flat plate 12 and the third flat plate 13; in the embodiment, in the subsequent measurement process, a tensile force is applied to the screw 14, an eccentric force may occur in the measurement process, and when the eccentric force occurs, an error may exist in the finally measured data. In order to ensure uniform stress, the first through hole 140 may be provided at a central position of one side of each of the first, second, and third flat plates 11, 12, and 13. The first through holes 140 may be symmetrically formed in the first plate 11, the second plate 12, and the third plate 13 with a plate center line as a symmetry axis.
An exemplary arrangement of the present embodiment is that one first through hole 140 is provided at a central position of one side of the first, second, and third flat plates 11, 12, and 13, and a pair of first through holes 140 is symmetrically provided at the other side of the first, second, and third flat plates 11, 12, and 13 with a plate center line as a symmetry axis. This embodiment is through passing many screws 14 the flat board, can effectively fix the flat board to avoid exerting tensile in-process to the screw 14 and causing the flat board to rock, and then avoided exerting tensile in-process measured data to the screw 14 and have had the error. And each flat plate is provided with three through holes, the connecting lines of the three through holes can form a triangle, and the triangle has stability, so that the flat plate is more stable. When a pulling force is applied to the screw 14, the flat plates can be kept stable, and the distance between the flat plates is ensured not to change.
The first flat plate 11 and the third flat plate 13 are respectively fastened with the screw 14 through a first nut 17; in the present embodiment, the screw 14 penetrates the first plate 11, the second plate 12, and the third plate 13, and when the first nut 17 is completely loosened, the first plate 11, the second plate 12, and the third plate 13 are moved on the screw 14, so that the distance between the first plate 11 and the second plate 12 can be adjusted, and when the first nut 17 is tightened, the first plate 11, the third plate 13 is fastened to the screw 14.
A tire to be tested is placed between the first flat plate 11 and the second flat plate 12; the first flat plate 11 and the second flat plate 12 are tangent to the outer circumference of the tire to be tested; the pressure sensor 15 is connected between the second flat plate 12 and the third flat plate 13; the pressure sensor 15 is used to measure the pressure value between the second plate 12 and the third plate 13 when the first nut 17 is tightened.
In the present embodiment, the tire to be tested is placed between the first plate 11 and the second plate 12, and the surfaces of the first plate 11 and the second plate 12 are tangent to the outer circumference of the tire to be tested. The pressure sensor 15 is connected between the second plate 12 and the third plate 13. When the first nut 17 is tightened, pressure is formed between the first flat plate 11 and the second flat plate 12, and between the second flat plate 12 and the third flat plate 13, and since the acting force and the reacting force between the two objects are equal and opposite in magnitude, the pressure between the first flat plate 11 and the second flat plate 12 is the positive pressure applied to the tire to be tested. The pressure between the second plate 12 and the third plate 13 is equal to the pressure between the first plate 11 and the second plate 12. The pressure between the second flat plate 12 and the third flat plate 13 is measured by the pressure sensor 15, that is, the positive pressure applied to the tire to be measured is obtained.
To ensure more accurate measurement data, the centerline of the pressure sensor 15 is aligned with the centerline of the tire under test.
According to the application, the first nuts 17 are arranged at the connecting parts of the first flat plate 11, the third flat plate 13 and the screw 14, and the positive pressure of the tire to be measured can be changed by adjusting the first nuts 17, so that the static friction coefficients under different positive pressures can be measured. By completely loosening the first and third plates 11 and 13 and the first nuts 17 at the screw rods 14, the first and second plates 11 and 12 are moved on the screw rods 14, the distance between the first and second plates 11 and 12 can be adjusted, and the static friction coefficient of tires of different diameters can be measured. And because the first flat plate 11, the second flat plate 12 and the third flat plate 13 are parallel to each other, the acting force exerted by the first flat plate 11 and the second flat plate 12 on the tire to be measured is ensured to be positive pressure, namely the acting force is vertically exerted on the contact surface of the tire to be measured, so that the measured static friction coefficient is more accurate.
The U-shaped plate 16 comprises a bottom plate 160 and two side plates 161; the opposite inner walls of the two side plates 161 are respectively provided with a connecting shaft 162; one end of the connecting shaft 162 penetrates through the inner wall of the side plate 161 and is fastened by a second nut 18; the other end of connecting axle 162 can be dismantled with the tire wheel hub that awaits measuring and be connected.
In the present embodiment, the U-shaped plate 16 is used for fixing the tire to be tested, and a connecting shaft 162 is disposed on the inner wall of each of the two side plates 161. One end of the connecting shaft 162 penetrates through the inner wall of the side plate 161, and the other end is detachably connected with the hub of the tire to be tested. The joint of the connecting shaft 162 and the side plate 161 is provided with a second nut 18, and the connecting shaft 162 can be drawn out from the side plate 161 by completely loosening the second nut 18, so that the tire to be tested can be placed in the groove of the U-shaped plate 16. Then, the connecting shaft 162 passes through the side plate 161 and is connected with the hub of the tire to be tested through a screw, and finally, the second nut 18 is screwed to complete the fixation of the tire to be tested.
This application is through placing the tire that awaits measuring in the recess of U template 16, and connecting axle 162 is fixed with the tire wheel hub that awaits measuring, realizes pressing from both sides tight fixedly to the tire wheel hub that awaits measuring. When the tire to be tested is fixed, the rotation of the tire to be tested is not influenced, and the tire to be tested is more convenient to mount and dismount. By replacing a small number of parts such as the U-shaped plate 16 and the connecting shaft 162, the static friction coefficients of tires with different widths can be measured.
It should be noted that, the connection between the connection shaft 162 and the tire hub to be tested by screws is only an exemplary embodiment, and the connection between the connection shaft 162 and the tire hub to be tested is not limited.
The screw 14 is connected with the tension assembly 2, and the tension assembly 2 is used for applying a tension force far away from the U-shaped plate 16 to the screw 14 until the first flat plate 11, the second flat plate 12 and the tire to be tested move relatively.
In this embodiment, the screw 14 is connected with the tension assembly 2. The U-shaped plate 16 is fixed to ensure that the tire to be tested does not move, and the tension component 2 applies tension to the screw 14, so that the first plate 11, the second plate 12 and the tire to be tested move relatively. When the first nut 17 is tightened, pressure is formed between the first plate 11 and the second plate 12, and between the second plate 12 and the third plate 13. Under the action of the pressure formed between the first plate 11 and the second plate 12, if the tensile force applied to the screw 14 is not enough to overcome the static friction force formed by the pressure, the first plate 11, the second plate 12 and the tire to be tested cannot move relatively. As the applied tension increases, when a critical point at which relative movement occurs between the first plate 11, the second plate 12 and the tire to be measured is reached, the first plate 11, the second plate 12 and the tire to be measured start to move relatively.
Further, this application current electron universal tester is adopted to tension assembly 2, and electron universal tester has the direct accurate effort of applying and reads the function of stress value, can realize accurate, stable tension control. The electronic universal testing machine comprises an upper cross beam 21 and a lower cross beam 22; the measuring device 1 is arranged between the upper cross beam 21 and the lower cross beam 22;
the screw 14 is connected with the upper cross beam 21;
the base plate 160 is connected to the lower cross member 22.
In this embodiment, the screw 14 is connected with the upper beam 21, the bottom plate 160 is connected with the lower beam 22, and the bottom plate 160 is fixed by the lower beam 22 of the electronic universal tester, so that the U-shaped plate 16 is ensured not to move. The upper cross beam 21 applies a pulling force to the screw 14, so that the first flat plate 11, the second flat plate 12 and the tire to be tested move relatively. The bottom plate 160 can also be fixed by the lower cross beam 22, and the upper cross beam 21 applies pressure to the screw 14, so that the first flat plate 11, the second flat plate 12 and the tire to be tested have relative movement.
In some embodiments, a first pin boss 23 is provided on the screw 14; the upper cross beam 21 is provided with a first pin shaft seat 24 matched with the first pin shaft sleeve 23; the bottom plate 160 is provided with a second pin shaft sleeve 25; the lower cross beam 22 is provided with a second pin shaft seat 26 matched with the second pin shaft sleeve 25.
The pin shaft is a standard fastener, and can be statically and fixedly connected or move relative to a connected piece. The first pin shaft sleeve 23 and the second pin shaft sleeve 25 are respectively sleeved with the first pin shaft seat 24 and the second pin shaft seat 26 and are connected in series through pin shafts. This embodiment measuring device 1 is connected with electron universal tester through the round pin axle, and reliable operation dismantles the convenience. Furthermore, the first pin shaft sleeve 23, the first pin shaft seat 24, the second pin shaft sleeve 25 and the second pin shaft seat 26 are arranged on the same line with the circle center of the tire to be measured, so that force is transmitted on the same line, torsion is avoided, and the accuracy of measurement and the accuracy of data are improved.
Because the first flat plate 11, the second flat plate 12 and the tire to be measured move relatively in a moment, how to accurately capture the initial action of the relative movement between the contact surface of the tire to be measured and the flat plate is very important for improving the accuracy of the measurement of the static friction coefficient. Therefore, the computer system 3 is configured, and the computer system 3 is configured to receive the pressure value data sent by the pressure sensor 15 and the measurement data sent by the tension assembly 2 in real time, and analyze and calculate to obtain the static friction coefficient of the tire to be measured; the measurement data includes the tension applied to the screw 14 by the tension assembly 2 and the amount of displacement of the screw 14.
In this embodiment, the computer system 3 receives, in real time, the pressure value between the second plate 12 and the third plate 13, that is, the positive pressure applied to the tire to be tested, sent by the pressure sensor 15. And receiving the pulling force applied to the screw 14 by the pulling force component 2 and the displacement of the screw 14 sent by the pulling force component 2 in real time, accurately measuring the initial motion of the relative motion of the first flat plate 11, the second flat plate 12 and the tire to be tested and the change of the pulling force, and analyzing to obtain the maximum pulling force value when the first flat plate 11, the second flat plate 12 and the tire to be tested move relatively. According to the definition of the static friction coefficient, the maximum static friction force generated when two contact objects are in a critical state of sliding but not sliding is defined, and the ratio of the maximum static friction force to the maximum static friction force generated when the positive pressure force is defined as the static friction coefficient. Therefore, the calculation process for measuring the primary static friction coefficient includes that the maximum tension value measured by the tension assembly 2 is divided by 2 to obtain the maximum static friction force, and then the maximum static friction force is divided by the positive pressure of the tire to be measured by the pressure sensor 15 to obtain the static friction coefficient of the tire to be measured in the primary measurement process.
Furthermore, the pressure value between the first plate 11 and the second plate 12, that is, the positive pressure applied to the tire to be measured, can be adjusted by adjusting the first nut 17, so that the maximum tensile value of the tire to be measured under different positive pressures can be measured, and then a plurality of static friction coefficients can be obtained, and the static friction coefficients can be more accurate by taking the average value.
The first flat plate 11 and the second flat plate 12 are made of steel plates, and the polyurethane tire 71 of the wall-climbing robot is fixed on the U-shaped plate 16, so that the static friction coefficient between the polyurethane tire 71 of the wall-climbing robot and the steel plates can be measured. And water is sprayed on the contact surfaces of the first flat plate 11 and the second flat plate 12 and the tire to be measured, so that the static friction coefficient between the tire and the flat plate material under the water working condition can be measured. By spraying water on the flat plate, the static friction coefficient of the tire in a water-free environment and a water-free environment is measured. The application range of the device is greatly increased, and the adaptability of the device is improved.
Further, the computer system 3 is configured to display the pressure value data sent by the pressure sensor 15 and the measurement data sent by the tension assembly 2 in real time, and the data can be fitted into a force-displacement curve or a force-displacement graph, so that a user can visually see the change of the data.
This application is through setting up computer system 3 for the traceability of measured data, measurement accuracy is high. The sensitivity of the tire changing from a static state to a moving state between the flat plates is greatly improved. The method and the device realize accurate measurement of relative movement starting action between the tire and the contact surface, thereby improving the measurement reliability of the static friction coefficient. And the low-efficiency operation of manual data recording is improved, one or more groups of measured all data can be recorded, the recording time is shortened to a great extent, and the working efficiency is improved.
In a second aspect, as shown in fig. 5 and 6, the present application provides a method for measuring a static friction coefficient of a tire, applied to a testing apparatus as described above, including:
s10, acquiring pressure value data sent by the pressure sensor 15, where the pressure value data is a pressure value between the second plate 12 and the third plate 13 when the first nut 17 is tightened;
the static friction coefficient is a friction coefficient when two objects have a relative motion trend but do not move relative to each other, and is generally represented by a symbol mu. When there is a relative motion trend between the objects, the positive pressure between the contact surfaces is N. Then f = μ N, f representing the maximum static friction force. Therefore, in order to solve the static friction coefficient between the tire to be tested and the flat contact surface, the positive pressure applied to the tire to be tested and the maximum static friction between the tire to be tested and the flat contact surface need to be known. The pressure value between the second flat plate 12 and the third flat plate 13 is the positive pressure applied to the tire to be tested.
S20, acquiring measurement data corresponding to the pressure value data sent by the tension component 2, wherein the measurement data comprises tension loaded on the screw 14 by the tension component 2 and displacement of the screw 14;
the static friction force is different from the general restraint counter force, and does not increase without limit with the increase of the external force. When the magnitude of the external force reaches a certain value, the object is in a critical state that the object is about to slide but does not start to slide. At this time, the static friction reaches the maximum value, namely the maximum static friction. Therefore, through the test device provided by the application, the first nut 17 is screwed, under the action of the pressure formed between the first flat plate 11 and the second flat plate 12, the tensile force far away from the U-shaped plate is applied to the screw 14, and if the tensile force applied to the screw 14 is not enough to overcome the static friction force formed by the pressure, the first flat plate 11, the second flat plate 12 and the tire to be tested cannot move relatively. As the applied tension increases, when a critical point at which relative movement occurs between the first plate 11, the second plate 12 and the tire to be measured is reached, the first plate 11, the second plate 12 and the tire to be measured start to move relatively.
And S30, analyzing and calculating according to the obtained pressure value data and the measured data to obtain the static friction coefficient of the tire to be measured.
The step of analyzing and calculating according to the acquired pressure value data and the acquired measurement data to obtain the static friction coefficient of the tire to be measured comprises the following steps of:
s31, analyzing according to the measurement data to obtain a maximum tension value of the tire to be measured, wherein the maximum tension value is a tension value of a critical point of relative movement of the first flat plate 11, the second flat plate 12 and the tire to be measured;
s32, calculating the maximum tension value to obtain the maximum static friction force corresponding to the pressure value of the tire to be tested;
and S33, calculating according to the maximum static friction force and the pressure value data to obtain a static friction coefficient of the tire to be measured, wherein the static friction coefficient is the ratio of the maximum static friction force to the pressure value data.
Analyzing the trend of relative movement of the first flat plate 11, the second flat plate 12 and the tire to be tested but the moment of no movement according to the data such as the change of the tensile force, the change of the displacement and the like in the measured data, wherein the tensile force value at the moment is the maximum tensile force value, because the surfaces of the first flat plate 11 and the second flat plate 12 are tangent to the outer circumference of the tire to be tested, the first flat plate 11, the second flat plate 12 and the tire to be tested generate static friction force, and dividing the maximum tensile force value by 2 is the maximum static friction force between the contact surface of the tire to be tested and the flat plate. According to the formula: f = μ N, the static friction coefficient of the tire to be tested, i.e. the ratio of the maximum static friction force between the tire to be tested and the contact surface to the positive pressure, can be obtained.
In some embodiments, the measurement data correspond to the tension value at least one time point, and the pressure value data correspond to the pressure value at the same time point as the critical point of relative movement of the first plate 11, the second plate 12 and the tire to be tested.
As the tensile force applied by the tension assembly 2 to the screw 14 increases gradually, the measurement data includes tensile force values at different time points, and in the process of applying the tensile force applied by the tension assembly 2 to the screw 14, the pressure value measured by the pressure sensor 15 may change, that is, the positive pressure applied to the tire to be tested may change. Therefore, when the maximum static friction force and the pressure value data are calculated, the pressure value of the pressure data is calculated by selecting the pressure value at the same time point as the critical point of relative movement of the first flat plate 11, the second flat plate 12 and the tire to be measured, so that the static friction coefficient is more accurate.
In some embodiments, calculating according to the maximum static friction force and the pressure value data to obtain a static friction coefficient of the tire to be measured, where the step of calculating the static friction coefficient as a ratio of the maximum static friction force to the pressure value data further includes:
and averaging a plurality of ratios of the maximum static friction force to the pressure value data to obtain the static friction coefficient.
When the static friction coefficient of the tire to be measured is measured, the tire to be measured can be measured for multiple times under the same positive pressure, then multiple maximum static friction forces are solved, the multiple maximum static friction forces are divided by pressure value data respectively, and then the average value is taken to obtain the static friction coefficient. Further, the pressure value between the second plate 12 and the third plate 13, i.e. the positive pressure applied to the tire to be tested, can be adjusted by adjusting the first nut 17. And respectively measuring the tire to be measured under different positive pressures, solving a plurality of maximum static friction forces, dividing the maximum static friction forces by corresponding pressure value data, and then averaging to obtain the static friction force coefficient. The static friction coefficient is more accurate through multiple measurement and solution.
The application provides a method for measuring the static friction coefficient of a tire, which obtains the static friction coefficient of the tire to be measured by acquiring pressure value data sent by a pressure sensor and measurement data corresponding to the pressure value data sent by a tension assembly in real time and analyzing and calculating the measurement data, and improves the precision and reliability of measuring the static friction coefficient.
The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments that can be extended by the solution according to the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.
Claims (9)
1. A test device for measuring the static friction coefficient of a tire comprises a measuring device (1), a tension assembly (2) and a computer system (3), and is characterized in that,
the measuring device (1) comprises a first flat plate (11), a second flat plate (12), a third flat plate (13), a screw rod (14), a pressure sensor (15) and a U-shaped plate (16);
the first flat plate (11), the second flat plate (12) and the third flat plate (13) are parallel to each other and are provided with first through holes (140); the screw (14) sequentially penetrates through the corresponding first through holes (140) in the first flat plate (11), the second flat plate (12) and the third flat plate (13); the first flat plate (11) and the third flat plate (13) are respectively fastened with the screw (14) through a first nut (17);
a tire to be tested is placed between the first flat plate (11) and the second flat plate (12); the first flat plate (11) and the second flat plate (12) are tangent to the outer circumference of the tire to be tested; the pressure sensor (15) is connected between the second plate (12) and the third plate (13); the pressure sensor (15) is used for measuring a pressure value between the second flat plate (12) and the third flat plate (13) when the first nut (17) is screwed down, and the pressure value is a positive pressure borne by a tire to be measured;
the U-shaped plate (16) comprises a bottom plate (160) and two side plates (161); connecting shafts (162) are respectively arranged on the opposite inner walls of the two side plates (161); one end of the connecting shaft (162) penetrates through the inner wall of the side plate (161) and then is fastened through a second nut (18); the other end of the connecting shaft (162) is detachably connected with a wheel hub of a tire to be tested;
the screw (14) is connected with the tension component (2), and the tension component (2) is used for applying tension far away from the U-shaped plate (16) to the screw (14) until the first flat plate (11), the second flat plate (12) and the tire to be tested move relatively;
the computer system (3) is configured to receive pressure value data sent by the pressure sensor (15) and measurement data sent by the tension assembly (2) in real time, and analyze and calculate the static friction coefficient of the tire to be tested; the measurement data comprises the tension applied to the screw (14) by the tension assembly (2) and the displacement of the screw (14).
2. The test device for measuring the static friction coefficient of a tire according to claim 1, wherein the tension assembly (2) is an electronic universal tester;
the electronic universal testing machine comprises an upper cross beam (21) and a lower cross beam (22); the measuring device (1) is arranged between the upper cross beam (21) and the lower cross beam (22);
the screw (14) is connected with the upper cross beam (21);
the base plate (160) is connected to the lower cross member (22).
3. A test device for measuring the static friction coefficient of a tyre as claimed in claim 2, characterized in that said threaded rod (14) is provided with a first pin bushing (23); a first pin shaft seat (24) matched with the first pin shaft sleeve (23) is arranged on the upper cross beam (21); a second pin shaft sleeve (25) is arranged on the bottom plate (160); and a second pin shaft seat (26) matched with the second pin shaft sleeve (25) is arranged on the lower cross beam (22).
4. The test device for measuring the static friction coefficient of a tire according to claim 1, wherein the first through hole (140) is formed in the center of one side of each of the first flat plate (11), the second flat plate (12) and the third flat plate (13).
5. A test device for measuring the static friction coefficient of a tire according to claim 1 or 4, wherein the first plate (11), the second plate (12) and the third plate (13) are all symmetrically provided with the first through holes (140) with the plate center line as the symmetry axis.
6. Test unit for measuring the static friction coefficient of a tyre as claimed in claim 1, characterized in that the pressure sensor (15) has a median aligned with the median of the tyre to be tested.
7. A method for measuring the static friction coefficient of a tire, applied to the test device of any one of claims 1 to 6, comprising:
acquiring pressure value data sent by a pressure sensor (15), wherein the pressure value data is a pressure value between a second flat plate (12) and a third flat plate (13) when a first nut (17) is screwed down;
acquiring measurement data which are sent by a tension component (2) and correspond to the pressure value data, wherein the measurement data comprise tension loaded on a screw (14) by the tension component (2) and displacement of the screw (14);
and analyzing and calculating according to the acquired pressure value data and the acquired measurement data to obtain the static friction coefficient of the tire to be measured, wherein the measurement data corresponds to the tension value at least one time point, and the pressure value data corresponds to the pressure value at the same time point as the critical point of relative movement of the first flat plate (11), the second flat plate (12) and the tire to be measured.
8. The method for measuring the static friction coefficient of the tire according to claim 7, wherein the step of performing analysis calculation according to the acquired pressure value data and the acquired measurement data to obtain the static friction coefficient of the tire to be measured comprises:
analyzing according to the measurement data to obtain the maximum tension value of the tire to be measured, wherein the maximum tension value is the tension value of a critical point of relative movement of the first flat plate (11), the second flat plate (12) and the tire to be measured;
calculating the maximum tension value to obtain the maximum static friction force corresponding to the pressure value borne by the tire to be tested;
and calculating according to the maximum static friction force and the pressure value data to obtain a static friction coefficient of the tire to be measured, wherein the static friction coefficient is the ratio of the maximum static friction force to the pressure value data.
9. The method for measuring the static friction coefficient of a tire according to claim 8, wherein the step of calculating the static friction coefficient of the tire to be measured according to the maximum static friction and the pressure value data further comprises:
and averaging a plurality of ratios of the maximum static friction force to the pressure value data to obtain the static friction coefficient.
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| CN113514389A (en) * | 2020-04-10 | 2021-10-19 | 广州汽车集团股份有限公司 | Friction coefficient measuring device and method thereof |
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