Pavement friction coefficient testing device and testing method

Abstract

The invention discloses a pavement friction coefficient testing device and a testing method. The pavement friction coefficient testing device comprises a testing box, a loading platform, a testing tire, a driving mechanism and a braking mechanism, wherein the testing box is internally provided with an accommodating space; the loading platform and the testing tire are rotationally mounted in the testing box; a pavement test piece extending in the circumferential direction is detachably connected to the outer circumferential surface of the loading platform, the pavement test piece is provided with a working surface which is used for being in contact with a test tire and enabling the test tire to rotate around the rotation axis of the test tire, and the rotation axis of the pavement test piece is parallel to the rotation axis of the test tire. The method has the beneficial effects that the test cost can be reduced, and the accuracy of a test result is improved.

Description

Technical Field

[0001] The invention relates to a road friction coefficient testing device and a testing method, belonging to the field of road material testing equipment and testing methods. Background Art

[0002] Road skid resistance refers to the ability of the road surface to provide sufficient friction to prevent slipping during vehicle driving. Good skid resistance can effectively ensure driving safety and reduce the occurrence of traffic accidents. In addition, excellent skid resistance helps vehicles maintain good handling and stability in various weather conditions and prevents vehicles from losing control. By studying the effects of road surfaces of different materials and structures on skid resistance, we can guide road design, select appropriate materials and construction methods, and improve the skid resistance of the road surface.

[0003] Usually, the braking method is used to test the tire-road dynamic friction coefficient, that is, the technology of measuring the dynamic friction coefficient between the tire and the road by simulating the slip behavior between the tire and the road during the vehicle braking process. However, the existing braking method needs to be tested outdoors under different real road conditions such as dry, wet, ice and snow, and requires special testing sites and equipment, which is costly; and multiple tests are required at different speeds and under different road conditions. The entire testing process is complicated and time-consuming; at the same time, there are certain safety risks in performing braking tests on actual roads; in addition, the test results of the braking method are greatly affected by environmental factors (such as temperature, humidity, and road conditions). Since environmental factors are uncontrollable, the test results are less accurate. Summary of the invention

[0004] The purpose of the present invention is to provide a road friction coefficient testing device and a testing method, which can reduce the testing cost and improve the accuracy of the test results.

[0005] The present invention is achieved through the following technical solutions.

[0006] A road friction coefficient testing device comprises a test box with a containing space inside, a loading platform and a test tire rotatably mounted in the test box, a driving mechanism for driving the loading platform to rotate, and a braking mechanism for controlling the locking of the loading platform; a road test piece extending in a circumferential direction is detachably connected to the outer peripheral surface of the loading platform, the road test piece has a working surface for contacting the test tire and causing the test tire to rotate around its own rotation axis, and the rotation axis of the road test piece is parallel to the rotation axis of the test tire; A rotating connecting piece is rotatably connected to the test tire, and a pressure regulating mechanism is provided on the test box. The pressure regulating mechanism has a pressure regulating component that can move along the distance direction between the rotation axis of the road test piece and the rotation axis of the test tire. The pressure regulating component is connected to the rotating connecting piece to adjust the pressure applied by the test tire to the road test piece.

[0007] As a further improvement of the present invention, the test tire is arranged directly above the road test piece so that the distance direction between the rotation axis of the test tire and the road test piece is vertically downward; a pressure detection component is provided between the pressure regulating component and the rotating connecting member for detecting the pressure applied by the pressure regulating mechanism to the road test piece.

[0008] As a further improvement of the present invention, the pressure regulating mechanism is configured as a cylinder telescopic mechanism or a hydraulic cylinder telescopic mechanism.

[0009] A road friction coefficient testing method, characterized in that a road friction coefficient testing device is applied to the above technical solution, and the steps of the testing method include: S1: Install a road test piece made of specified material on the loading platform; S2: Controlling the contact between the test tire and the road test piece through the pressure regulating mechanism, and detecting the pressure P applied by the pressure regulating mechanism on the test tire; S3: Control the driving mechanism to drive the loading platform to rotate, thereby driving the test tire to rotate; S4: Control the braking mechanism and the driving mechanism to drive the loading platform to brake, and detect the rotation speed v0 of the test tire when the loading platform is braked; S5: Detecting the moving travel L of the test tire relative to the road test piece after the loading platform is braked; S6: Replace the road test piece with a different material and repeat steps S1 to S5; S7: Calculate the friction coefficient µ between the road test pieces of different materials and the test tire. The specific calculation formula is as follows: Where: m represents the weight of the test tire, mg represents the gravity exerted on the test tire.

[0010] As a further improvement of the present invention, a temperature control mechanism is provided in the test box for adjusting the temperature in the test box.

[0011] As a further improvement of the present invention, a spray unit is provided in the test box, and the unit at least includes a spray head and a delivery pipe for delivering lubricating medium to the spray head, and the spray head has at least one water outlet for spraying lubricating medium onto the road test piece or test tire.

[0012] As a further improvement of the present invention, before performing step S4, the test tire is controlled to rotate at a constant speed by a driving mechanism.

[0013] As a further improvement of the present invention, when performing step S4, the driving mechanism is turned off while the braking mechanism is turned on.

[0014] As a further improvement of the present invention, the testing device further comprises a distance measuring mechanism having a camera component for detecting the movement stroke of the test tire relative to the road test piece after the road test piece is braked, and the camera component is arranged toward the side of the test tire.

[0015] As a further improvement of the present invention, a speed measuring mechanism is provided in the test box, which has a speed measuring component for contacting with the surface of the test tire to test the rotation speed of the test tire.

[0016] Beneficial effects of the present invention: 1. When the driving mechanism drives the road test piece to rotate, the test tire is driven to rotate by the road test piece under the action of friction. When the vehicle is driving on the real road, the road is stationary, and the tire rotates and moves relative to the road. In this test, the relative movement of the tire during driving is simulated by the rotation of the road test piece, which can more realistically simulate the interaction between the tire and the road, so that the contact between the test tire and the road test piece is closer to the real dynamic contact between the tire and the road during actual driving. The road test piece is set along the circumferential extension of the loading platform. Compared with the horizontally paved road, its structure is compact and occupies less space. Accordingly, the volume of the test box can be reduced. On the one hand, since the entire test process is carried out inside the test box, the smaller the internal space of the test box, the easier it is to control the test conditions, which can not only reduce the interference of the external environment, but also help to improve the consistency and repeatability of the test, thereby improving the accuracy of the test results. On the other hand, a smaller test box helps to reduce the test cost.

[0017] 2. The movement of the pressure regulating component is used to drive the test tire to move. On the one hand, the pressure of the test tire on the road test piece can be accurately adjusted to simulate the impact of different loads (such as vehicle weight) on the test. On the other hand, the movement of the pressure regulating component can be used to drive the test tire to move, so that the test tire can be detached from the road test piece when the road test piece is replaced, thereby avoiding interference with the replacement of the road test piece by the test tire, facilitating the replacement of the road test piece and improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to help understand the purpose and advantages of the present invention, wherein: Figure 1It is a schematic structural diagram of the cooperation among the test box, the test tire and the loading platform in a road friction coefficient test device of the present invention; Figure 2 A side view of a road friction coefficient testing device according to the present invention; Figure 3 This is a diagram of the internal structure of the test box from a top-down perspective; Figure 4 It is a schematic diagram of the structure of the pressure regulating mechanism and the test tire; DETAILED DESCRIPTION

[0019] The present invention is further described in detail below based on the accompanying drawings and implementation examples.

[0020] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. The words "inside" and "outside" refer to the direction toward or away from the geometric center of a specific component, respectively. They are relative concepts, and therefore may change accordingly according to different locations and different usage conditions. Therefore, these or other directional terms should not be interpreted as restrictive terms.

[0021] Embodiment 1: A road friction coefficient testing device is used to test the friction coefficient between the tire 3 and the road surface to evaluate the anti-skid performance of different road surfaces. Figures 1 to 4 , comprising a test box 1 with a containing space inside, a loading platform 2 rotatably installed in the test box 1, a test tire 3 rotatably arranged above the loading platform 2, a driving mechanism 4 for driving the loading platform 2 to rotate, and a braking mechanism 5 for controlling the locking of the loading platform 2; a road test piece 6 extending in the circumferential direction is detachably connected to the outer peripheral surface of the loading platform 2, and the road test piece 6 has a working surface for contacting with the test tire 3 and rotating the test tire 3 around its rotation axis, and the rotation axis of the road test piece 6 is parallel to the rotation axis of the test tire 3. The working surface here refers to the outer peripheral surface of the road test piece 6.

[0022] In this embodiment, the rotation axes of the road test piece 6 and the test tire 3 are parallel, so that the contact area between the two forms a line contact or a surface contact, rather than a point contact, so as to be more in line with the actual contact state between the tire and the road surface. In addition, the driving mechanism 4 drives the loading platform 2 to rotate, and the surface of the road test piece installed on the loading platform 2 contacts the test tire 3. When the road test piece 6 rotates, the test tire 3 is driven to rotate by the road test piece 6 under the action of friction. When the vehicle is driving on a real road surface, the road surface is stationary, and the tire rotates and moves relative to the road surface. When the device is used for testing, the relative movement of the tire during driving is simulated by the rotation of the road test piece 6, so as to more realistically simulate the interaction between the tire and the road surface, so that the contact between the test tire 3 and the road test piece 6 is closer to the real dynamic contact between the tire and the road surface during actual driving.

[0023] At the same time, the road test piece 6 is extended along the circumference of the loading platform 2. Compared with a horizontally paved road surface, it has a compact structure and occupies less space. Accordingly, the volume of the test box 1 can be reduced. On the one hand, the entire test process is carried out inside the test box 1, and the smaller the internal space of the test box 1, the easier it is to control the test conditions, which can not only reduce the interference of the external environment, but also help to improve the consistency and repeatability of the test, thereby improving the accuracy of the test results. On the other hand, the smaller volume of the test box 1 helps to reduce the test cost.

[0024] In addition, a rotating connection member 31 is rotatably connected to the test tire 3, and a pressure regulating mechanism 7 is provided on the test box 1. The pressure regulating mechanism 7 has a pressure regulating component 71 that can move along the rotation axis of the road test piece 6 and the rotation axis of the test tire 3. The pressure regulating component 71 is connected to the rotating connection member 31. The movement of the pressure regulating component 71 can drive the test tire 3 to move in a direction close to or away from the road test piece 6 to adjust the pressure applied by the test tire 3 to the road test piece 6. The movement of the pressure regulating component 71 drives the test tire 3 to move. On the one hand, the pressure of the test tire 3 on the road test piece 6 can be accurately adjusted to simulate the influence of different loads (such as vehicle weight) on the test. On the other hand, the movement of the pressure regulating component 71 can drive the test tire 3 to move, so that the test tire 3 can be separated from the road test piece 6 when the road test piece 6 is replaced, thereby avoiding interference caused by the test tire 3 on the replacement of the road test piece 6, facilitating the replacement of the road test piece 6, and improving the test efficiency.

[0025] The principle of using this device to test the road friction coefficient is as follows: First, the contact between the road test piece 6 and the test tire 3 is controlled. When the road test piece 6 rotates under the drive of the driving mechanism 4, the test tire 3 will be driven to rotate due to the friction f1 between the road test piece 6 and the test tire 3. When the road test piece 6 continues to rotate and its rotation speed remains unchanged, the road test piece 6 is controlled to brake urgently through the braking mechanism 5. At this time, the road test piece 6 no longer pulls the test tire 3 to rotate, and the test tire 3 only rotates by its own rotational inertia. However, since it will contact the fixed road test piece 6 during the rotation process, it will be affected by the dynamic friction f2 of the road test piece 6. Therefore, the test tire 3 will perform uniform deceleration until it stops. Therefore, the dynamic friction coefficient µ between the road test piece 6 and the tire can be obtained according to the dynamic friction formula, so as to compare the anti-skid performance of different road surfaces. The specific calculation formula is as follows: Wherein N represents the pressure to which the road test specimen 6 is subjected.

[0026] At the same time, the velocity displacement formula is obtained: Among them, v 0 Refers to the rotation speed of the test tire 3 when the loading platform 2 is braked, v t Refers to the final speed. Since the wheels are in uniform deceleration motion, v t =0, and the distance that the test tire 3 performs uniform deceleration motion is set to L, that is, x=L.

[0027] Combined with the dynamic friction acceleration formula: The dynamic friction force f2 can be calculated, and thus the dynamic friction coefficient µ can be calculated.

[0028] At the same time, in order to conveniently and quickly detect the pressure on the road test piece 6, the test tire 3 is placed directly above the road test piece 6 so that the distance direction between the road test piece 6 and the rotation axis of the test tire 3 is vertically downward. At this time, the gravity of the test tire 3 is completely borne by the road test piece 6, and the pressure applied by the pressure regulating component 71 to the test tire 3 is vertically downward, which is the same as the gravity direction of the test tire 3. Therefore, the pressure on the road test piece 6 is the gravity of the test tire 3 plus the pressure applied by the pressure regulating mechanism 7 to the test tire 3. In addition, a pressure detection component 72 is provided between the pressure regulating component 71 and the rotating connecting member 31, which is used to detect the pressure applied by the pressure regulating mechanism 7 to the road test piece 6. At this time, the pressure applied by the test tire 3 to the road test piece 6 can be accurately obtained only by the pressure detection component 72, and its structure is simple and the cost is low.

[0029] Therefore, when the test tire 3 contacts the road test piece 6, the pressure on the road test piece 6 is the gravity mg of the test tire 3 and the pressure P applied by the pressure regulating mechanism 7 to the test tire 3 in the vertical direction, that is: Finally, the formula is: In this embodiment, in order to accurately control the pressure applied by the pressure regulating mechanism 7 to the test tire 3, the pressure regulating mechanism 7 is set as a cylinder telescopic mechanism or a hydraulic cylinder telescopic mechanism, and its telescopic end is the above-mentioned pressure regulating component 71. The pressure regulating component 71 passes through the top of the test box 1 and is connected to the rotating connection member 31 through the pressure detection component 72. The cylinder body is located outside the test box 1 and fixed to the top of the test box 1 to ensure the stability of the movement of the pressure regulating component 71. At the same time, an air pressure sensor can also be installed at the air inlet of the cylinder to detect the pressure applied by the cylinder telescopic mechanism to the rotating connection member 31, or a hydraulic pressure sensor can be installed at the oil inlet and oil return port of the hydraulic cylinder to detect the pressure applied by the hydraulic telescopic mechanism to the rotating connection member 31.

[0030] In this embodiment, the loading platform 2 includes an assembly frame 21 for mounting the road test piece 6, a rotating component 22 connected to the driving mechanism 4, and a plurality of connecting components 23 for connecting the assembly frame 21 and the rotating component 22. The assembly frame 21 is annular, and the road test piece 6 is mounted on the outer peripheral surface of the assembly frame 21. The road test piece 6 in this embodiment can be divided into multiple parts, and is fixed to the outer peripheral surface of the assembly frame 21 in sequence by fasteners such as screws or nails.

[0031] In this embodiment, the driving mechanism 4 can be set as a power component such as an engine, a motor or an electric motor, and its output end is connected to the rotating component 22 of the loading platform 2. When the driving mechanism 4 is working, it can drive the loading platform 2 to rotate, thereby driving the contact test tire 3 with the road test piece 6 installed on the loading platform 2 to rotate. In addition, the braking mechanism 5 in this embodiment has a plurality of braking components in contact with the rotating component 22. The braking component here is set as a disc brake structure, which is installed on the rotating component 22 and controlled by an external controller. When the disc brake structure is working, it produces a braking effect on the rotating connection member 31, so that the road test piece 6 is braked urgently.

[0032] In this embodiment, a temperature control mechanism 9 is provided in the test box 1, which includes at least a heating module and a cooling module to control the temperature in the test box 1. Therefore, the temperature control mechanism 9 can accurately simulate the actual temperature in the external environment in the test box 1, further improving the accuracy of the test. Specifically, the temperature control mechanism 9 here can be set as an air conditioner. Since the test box 1 is a relatively closed space, the temperature in the test box 1 can be controlled by the cooling and heating functions of the air conditioner, and the heating and cooling functions of the air conditioner can be accurately controlled by the remote control of the air conditioner.

[0033] In this embodiment, a spray unit 10 is provided in the test box 1. The spray unit 10 includes at least a spray head 10a and a delivery pipe 10b for delivering a lubricating medium into the test box 1. The spray head 10a is provided with a plurality of water outlets, which are arranged toward the road test piece 6 or the test tire 3, and are used to spray a lubricating medium onto the road test piece 6 or the test tire 3. The lubricating medium here is set as water, that is, continuous water spraying on the road test piece 6 is used to simulate the vehicle driving conditions on rainy days or slippery roads on actual roads, thereby improving the accuracy of the test results. In addition, at least one water outlet is provided at the bottom of the test box 1, so that the lubricating medium sprayed by the spray unit 10 can flow out of the water outlet in time, thereby avoiding the accumulation of water in the test box 1 affecting normal testing.

[0034] In this embodiment, a speed measuring mechanism is installed in the test box 1, which has a speed measuring component 8 for contacting the surface of the test tire 3 to test the rotation speed of the test tire 3. The speed measuring component 8 here is configured as a speedometer, which can measure the rotation speed of the test tire 3 by contacting the test tire 3.

[0035] In this embodiment, the test device also includes a distance measuring mechanism, which has a camera component 11. The camera component 11 here can be a high-definition video recorder, which is installed in the test box 1 and is used to detect the movement distance of the test tire 3 relative to the road test piece 6 after the road test piece 6 is braked. During the specific test, the camera component 11 is set toward the side of the test tire 3, and a marking point is set on the side of the test tire 3 using a marker or other marking equipment. Therefore, the camera component 11 is used to record the rotation angle of the marking point on the test tire 3 after the loading platform 2 is braked, that is, the arc length formula can be used to calculate and accurately obtain the movement distance of the test tire 3 relative to the road test piece 6 after the loading platform 2 is braked.

[0036] Embodiment 2: A road friction coefficient testing method, applied to the road friction coefficient testing device in Example 1, is used to detect the friction coefficient of a test tire 3 on different road test pieces 6, so as to judge the anti-skid performance of different road surfaces, and specifically comprises the following steps: S1: Installing a road test piece 6 made of a specified material on the loading platform 2; S2: controlling the test tire 3 to contact the road test piece 6 through the pressure regulating mechanism 7, and detecting the pressure applied by the pressure regulating mechanism 7 on the test tire 3; S3: Control the driving mechanism 4 to drive the loading platform 2 to rotate, so that the test tire 3 rotates; S4: Control the braking mechanism 5 and the driving mechanism 4 to brake the loading platform 2, and detect the rotation speed of the test tire 3 when the loading platform 2 is braked; S5: Detecting the moving distance of the test tire 3 relative to the road test piece 6 after the loading platform 2 is braked; S6: Replace the road test piece 6 with a different material and repeat steps S1 to S5; S7: Calculate the friction coefficient between the road test piece 6 of different materials and the test tire 3. The specific calculation formula is as follows: Wherein, m represents the weight of the test tire 3 , and mg represents the gravity exerted on the test tire 3 .

[0037] In this embodiment, the law of conservation of energy is used to convert kinetic energy into friction work, and the complex dynamic friction process is simplified into easily measurable physical quantities such as pressure, speed, and stroke, which helps to reduce complex calculations and improve efficiency. In addition, it is convenient to test different materials and compare the friction performance of different road surfaces, which helps in material selection and has low testing costs.

[0038] It should be noted that in step S4, when the braking mechanism 5 is turned on, the driving mechanism 4 needs to be turned off and stop providing rotational force to the loading platform 2 to ensure that the loading platform 2 can stop rotating immediately under the action of the braking mechanism 5, thereby avoiding test errors caused by untimely braking or continuous rotation of the road test piece 6.

[0039] In this embodiment, before performing step S2, the temperature in the test box 1 is controlled by the temperature control mechanism 9, that is, the friction behavior between the tire and the road under different temperature conditions can be simulated, so that the test conditions are more in line with the actual vehicle driving conditions, which helps to improve the authenticity of the test results. At the same time, before performing step S2, water can be sprayed onto the surface of the road test piece 6 through the spray unit 10, so as to simulate the rainy day conditions in the test box 1, and test the friction behavior between the test tire 3 and the road test piece 6 under the rainy day conditions.

[0040] In this embodiment, before performing step S4, the test tire 3 is controlled to rotate at a constant speed by the driving mechanism 4. One of the power components such as the engine, motor or electric motor of this embodiment only needs to control the output power of the driving mechanism 4 to remain unchanged, so as to achieve the uniform rotation of the test tire 3. When the test tire 3 rotates at a constant speed, the rotation speed of the test tire 3 detected by the test component remains unchanged, thereby reducing the measurement error caused by speed fluctuations and improving the accuracy of the test results.

[0041] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A road friction coefficient testing device, characterized in that: The invention comprises a test box (1) having a containing space inside, a loading platform (2) and a test tire (3) rotatably mounted inside the test box (1), a driving mechanism (4) for driving the loading platform (2) to rotate, and a braking mechanism (5) for controlling the locking of the loading platform (2); a road test piece (6) extending in the circumferential direction is detachably connected to the outer peripheral surface of the loading platform (2); the road test piece (6) has a working surface for contacting the test tire (3) and causing the test tire (3) to rotate around its own rotation axis; and the road test piece (6) is provided with a plurality of driving mechanisms (4) for driving the loading platform (2) to rotate. The rotation axis of the test piece (6) is parallel to the rotation axis of the test tire (3); a rotation connection piece (31) is rotationally connected to the test tire (3); a pressure regulating mechanism (7) is provided on the test box (1); the pressure regulating mechanism (7) has a pressure regulating component (71) movable along the direction of the spacing between the rotation axis of the road test piece (6) and the rotation axis of the test tire (3); the pressure regulating component (71) is connected to the rotation connection piece (31) to adjust the pressure applied by the test tire (3) to the road test piece (6).

2. A road friction coefficient testing device according to claim 1, characterized in that: The test tire (3) is arranged directly above the road test piece (6) such that the distance between the rotation axis of the test tire (3) and the rotation axis of the road test piece (6) is directed vertically downward; a pressure detection component (72) is provided between the pressure regulating component (71) and the rotating connecting component (31) for detecting the pressure applied by the pressure regulating mechanism (7) to the test tire (3).

3. A road friction coefficient testing device according to claim 2, characterized in that: The pressure regulating mechanism (7) is configured as a cylinder telescopic mechanism or a hydraulic cylinder telescopic mechanism.

4. A road friction coefficient testing method, characterized in that: A road friction coefficient testing device applied to claim 2 or 3, wherein the testing method comprises the following steps: S1: installing a road test piece (6) made of a specified material on a loading platform (2); S2: controlling the test tire (3) to contact the road test piece (6) through the pressure regulating mechanism (7), and detecting the pressure P applied by the pressure regulating mechanism (7) to the test tire (3); S3: controlling the driving mechanism (4) to drive the loading platform (2) to rotate, thereby driving the test tire (3) to rotate; S4: controlling the braking mechanism (5) and the driving mechanism (4) to brake the loading platform (2), and detecting the rotation speed v0 of the test tire (3) when the loading platform (2) is braked; S5: Detecting the moving distance L of the test tire (3) relative to the road test piece (6) after the loading platform (2) is braked; S6: Replace the road test piece (6) with a different material and repeat steps S1 to S5; S7: Calculate the friction coefficient µ between the road test piece (6) of different materials and the test tire (3). The specific calculation formula is as follows: ， Wherein: m represents the weight of the test tire (3), and mg represents the gravity exerted on the test tire (3).

5. A road friction coefficient testing method according to claim 4, characterized in that: A temperature control mechanism (9) is provided in the test box (1) for adjusting the temperature in the test box (1).

6. A road friction coefficient testing method according to claim 4, characterized in that: The test box (1) is provided with a spray unit (10), the unit comprising at least a spray head (10a) and a delivery pipe (10b) for delivering a lubricating medium to the spray head (10a), the spray head (10a) having at least one water outlet for spraying the lubricating medium onto the road test piece (6) or the test tire (3).

7. A road friction coefficient testing method according to claim 4, characterized in that: Before performing step S4, the test tire (3) is controlled to rotate at a constant speed by the driving mechanism (4).

8. A road friction coefficient testing method according to claim 4, characterized in that: When performing step S4, the driving mechanism (4) is turned off while the braking mechanism (5) is turned on.

9. A road friction coefficient testing method according to claim 4, characterized in that: The testing device further comprises a distance measuring mechanism having a camera component (11) for detecting the movement travel of the test tire (3) relative to the road test piece (6) after the road test piece (6) is braked, and the camera component (11) is arranged toward the side of the test tire (3).

10. A road friction coefficient testing method according to claim 4, characterized in that: The test box (1) is provided with a speed measuring mechanism having a speed measuring component (8) for contacting the surface of the test tire (3) to detect the rotation speed of the test tire (3).

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