Tire braking performance detection method

Abstract

The invention provides a tire braking performance detection method. The tire braking performance detection method comprises the steps that the longitudinal rigidity A, the ground contact area B and the ground contact rate C of a tire are obtained; constructing a first calculation module of the tire dry land braking rate, and inputting the longitudinal rigidity and the grounding area into the first calculation module: constructing a second calculation module of the tire wet land braking rate, and inputting the longitudinal rigidity, the grounding area and the grounding rate into the second calculation module; according to the first calculation module and the second calculation module, the dry land braking rate and the wet land braking rate of the tire are calculated, and the problems that in the prior art, the result accuracy of the braking performance test of the tire is low, and the test efficiency is low are solved.

Description

Technical Field

[0001] The invention relates to tire performance detection, and in particular to a method for detecting tire braking performance. Background Art

[0002] At present, cars have become an indispensable means of transportation. With the diversification of user needs, the performance requirements for cars are getting higher and higher. Tires, as an important part of the vehicle, take into account both the driving comfort and safety performance of the vehicle.

[0003] Tires have four basic functions in cars: bearing loads; buffering road impacts; providing starting acceleration and braking capabilities; and providing steering capabilities. Braking performance is a safety performance, which is divided into dry braking and wet braking. It affects driving safety, and the main indicators are dry braking distance and wet braking distance. Therefore, the braking performance of tires needs to be tested before they leave the factory.

[0004] In the prior art, most tires are transported to a special test site for testing, but this is not only time-consuming and costly, but also cannot be used as an entry test method. In addition, the test results of an indoor rigidity testing machine are quite different from the actual road test, the test results are inaccurate, and the test efficiency is low. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for detecting the braking performance of a tire, so as to solve the problems of low accuracy of the results of the braking performance test of the tire and low testing efficiency in the prior art.

[0006] In order to achieve the above object, according to one aspect of the present invention, a method for detecting tire braking performance is provided, comprising: obtaining longitudinal stiffness A, contact area B and contact ratio C of the tire; constructing a first calculation module for tire dry braking ratio, and inputting the longitudinal stiffness and contact area into the first calculation module:

[0007]

[0008] constructing a second calculation module for tire wet braking rate, and inputting the longitudinal stiffness, the contact area and the contact rate into the second calculation module;

[0009] Wet braking rate = A×y+(B×z)×10 -2 +

(1-C)×10 2

[0010] Among them, m, n, y, and z are constants.

[0011] Furthermore, obtaining the longitudinal stiffness A of the tire includes: placing the tire on a test platform; controlling the tire to rotate at a first predetermined speed; controlling the test platform to move at a second predetermined speed while applying a longitudinal force to the tire; obtaining a change curve of the longitudinal force and the longitudinal displacement of the tire, and obtaining a calculation formula for the longitudinal stiffness of the tire.

[0012] Furthermore, the longitudinal force and tire displacement variation curve is:

[0013]

[0014] Among them, F x : longitudinal force, N;

[0015] S x : longitudinal displacement, mm;

[0016] a, b, c, d: correlation coefficients during curve fitting, dimensionless.

[0017] Furthermore, obtaining the longitudinal rigidity calculation formula of the tire includes: taking the first-order derivative of the longitudinal force and tire displacement change curve to obtain the longitudinal rigidity calculation formula:

[0018]

[0019] Among them, L x : longitudinal stiffness, N / mm;

[0020] S , x (F x ): S x (F x ) is the first-order derivative of .

[0021] Furthermore, obtaining the longitudinal stiffness A of the tire also includes: before controlling the tire to rotate at a first predetermined speed, filling the tire with a predetermined air pressure load according to different specifications of the tire, and applying different longitudinal forces to the tire according to the predetermined air pressure load value D.

[0022] Further, when the predetermined air pressure load value D×70%>7000N, the maximum value of the longitudinal force is 7000N; when the predetermined air pressure load value D×70%≤7000N, the maximum value of the longitudinal force is (D×70%)N.

[0023] Furthermore, the method for obtaining the contact area B and the contact rate C includes: placing the tire on a test platform, controlling the tire to run at a third predetermined speed, collecting the pressure value of the tire on the test platform and the contact print of the tire; and obtaining the contact area and the contact rate based on the pressure value and the contact print.

[0024] Furthermore, the method for obtaining the contact area B and the contact rate C also includes: a pressure detection component is provided on the test platform, and the collection frequency of the pressure detection component is set to a preset frequency threshold; while the tire is running at a third predetermined speed, a radial load is applied to the tire to a preset load value; after the radial load is applied to the preset load value, the tire maintains the preset load value to a preset time threshold.

[0025] Furthermore, the method for obtaining the longitudinal stiffness A, contact area B and contact rate C of the tire includes: obtaining multiple longitudinal stiffness values ​​A1, calculating the average value of the multiple longitudinal stiffness values ​​A1 to obtain the longitudinal stiffness A; obtaining multiple contact areas B1, calculating the average value of the multiple contact areas B1 to obtain the contact area B; obtaining multiple contact rates C1, calculating the average value of the multiple contact rates C1 to obtain the contact rate C.

[0026] Furthermore, the method for detecting the braking performance of the tire also includes: after the tire is parked for a first set time after vulcanization, inflating the tire and leaving it for at least a second set time; monitoring the tire pressure of the tire that has been left for at least the second set time, and after the monitoring is qualified, obtaining the tire for testing to obtain the longitudinal stiffness A, the contact area B and the contact rate C of the tire through the inflation test.

[0027] By applying the technical solution of the present invention, a method for detecting the braking performance of a tire provided in the present application includes obtaining the longitudinal stiffness A, the contact area B and the contact ratio C of the tire; constructing a first calculation module for the dry braking ratio of the tire, and inputting the longitudinal stiffness and the contact area into the first calculation module; constructing a second calculation module for the wet braking ratio of the tire, and inputting the longitudinal stiffness, the contact area and the contact ratio into the second calculation module; according to the first calculation module and the second calculation module, the dry braking ratio and the wet braking ratio of the tire are calculated respectively, and the braking performance of the tire under different driving environments can be calculated, thereby improving the accuracy of the braking performance detection of the tire, and adopting an integrated test of the rigidity test and the contact pressure test, which can save costs and improve the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1 A schematic diagram showing a flow chart of an embodiment of a method for detecting tire braking performance according to the present invention;

[0030] Figure 2 FIG. 1 is a schematic diagram showing a detection state of a tire according to the present invention.

[0031] The above drawings include the following reference numerals: DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] Please refer to Figure 1 The present application provides a method for detecting tire braking performance, comprising: obtaining the longitudinal stiffness A, the contact area B and the contact rate C of the tire; constructing a first calculation module for the tire dry braking rate, and inputting the longitudinal stiffness and the contact area into the first calculation module:

[0034]

[0035] constructing a second calculation module for tire wet braking rate, and inputting the longitudinal stiffness, the contact area and the contact rate into the second calculation module;

[0036] Wet braking rate = A×y+(B×z)×10 -2 +

(1-C)×10 2

[0037] Among them, m, n, y, and z are constants.

[0038] The tire braking performance detection method provided in the present application includes obtaining the longitudinal stiffness A, the contact area B and the contact ratio C of the tire; constructing a first calculation module for the tire dry braking ratio, and inputting the longitudinal stiffness and the contact area into the first calculation module; constructing a second calculation module for the tire wet braking ratio, and inputting the longitudinal stiffness, the contact area and the contact ratio into the second calculation module; calculating the dry braking ratio and the wet braking ratio of the tire according to the first calculation module and the second calculation module, respectively, being able to calculate the braking performance of the tire under different driving environments, thereby improving the accuracy of the tire braking performance detection, and adopting an integrated test of the rigidity test and the contact pressure test, being able to save costs and improve the detection efficiency.

[0039] Obtaining the longitudinal stiffness A of the tire includes: placing the tire on a test platform; controlling the tire to move at a first predetermined speed; controlling the test platform to move at a second predetermined speed to apply a longitudinal force to the tire; obtaining a longitudinal force and a longitudinal displacement change curve of the tire to obtain a calculation formula for the longitudinal stiffness of the tire. Preferably, the first predetermined speed and the second predetermined speed are 20 mm / min, respectively.

[0040] In the specific implementation process, the longitudinal force and tire displacement change curve is:

[0041]

[0042] Among them, Fx : longitudinal force, N;

[0043] S x : longitudinal displacement, mm;

[0044] a, b, c, d: correlation coefficients during curve fitting, dimensionless.

[0045] When fitting a curve, it is necessary to ensure that R 2 ≥0.99. Among them, R 2 is the fitting coefficient, the closer it is to 1, the better the fitting effect.

[0046] The calculation formula for the longitudinal rigidity of the tire includes: taking the first-order derivative of the longitudinal force and tire displacement curve to obtain the longitudinal rigidity calculation formula:

[0047]

[0048] Among them, L x : longitudinal stiffness, N / mm;

[0049] S , x (F x ): S x (F x ) is the first-order derivative of .

[0050] Obtaining the longitudinal stiffness A of the tire also includes: before controlling the tire to rotate at a first predetermined speed, filling the tire with a predetermined air pressure load according to different specifications of the tire, and applying different longitudinal forces to the tire according to the predetermined air pressure load value D.

[0051] When the predetermined air pressure load value D×70%>7000N, the maximum longitudinal force is 7000N; when the predetermined air pressure load value D×70%≤7000N, the maximum longitudinal force is (D×70%) N. The direction of the longitudinal force is the direction of movement of the platform.

[0052] The method for obtaining the contact area B and the contact rate C includes: placing the tire on the test platform, controlling the tire to run at a third predetermined speed, collecting the pressure value of the tire on the test platform and the contact print of the tire; and obtaining the contact area and the contact rate according to the pressure value and the contact print. Preferably, the third predetermined speed is 15 mm / min to 25 mm / min. Within this range, the load is most stable when loading and the loading efficiency is higher.

[0053] The method for obtaining the contact area B and the contact rate C also includes: a pressure detection component is provided on the test platform, and the collection frequency of the pressure detection component is set to a preset frequency threshold; while the tire is running at a third predetermined speed, a radial load is applied to the tire to a preset load value; after the radial load is applied to the preset load value, the tire maintains the preset load value to a preset time threshold. Preferably, the preset frequency threshold is 2 frames / s, the third predetermined speed is 25 mm / min, and the preset time threshold is 2 min to 10 min.

[0054] The method for obtaining the longitudinal stiffness A, the contact area B and the contact rate C of the tire includes: obtaining multiple longitudinal stiffness values ​​A1, calculating the average value of the multiple longitudinal stiffness values ​​A1 to obtain the longitudinal stiffness A; obtaining multiple contact areas B1, calculating the average value of the multiple contact areas B1 to obtain the contact area B; obtaining multiple contact rates C1, calculating the average value of the multiple contact rates C1 to obtain the contact rate C.

[0055] The tire braking performance detection method further includes: after the tire is parked for a first set time after vulcanization, inflating the tire and placing it for at least a second set time; monitoring the tire pressure of the tire that has been placed for at least the second set time, and after the monitoring is qualified, obtaining the tire for detection to obtain the longitudinal stiffness A, the contact area B and the contact rate C of the tire through the inflation test. Preferably, the first set time is 24 hours and the second set time is 3 hours.

[0056] In the actual test process, the test conditions are as follows: the tested tires are parked for 24 hours after vulcanization; the appearance quality of the test tires shall comply with the provisions of GB / T 9743 or GB / T 9744, the test rims shall comply with the provisions of GB / T 2977 or GB / T 2978; the test load shall comply with the load specified in GB / T 2977 or GB / T 2978. The test is repeated three times, and each round is filled with the corresponding air pressure in Table 1 and loaded with the load in Table 1.

[0057]

[0058] Table 1

[0059] The inflated test tire and rim assembly should be kept in a laboratory at room temperature of (20-30)°C for more than 3 hours. If the air pressure drops, refill it to the specified pressure and then test it after 15 minutes of parking.

[0060] During the specific test process, Figure 2As shown, Fx is the longitudinal force direction of the tire. Clean the dirt, debris and other pollutants on the tire surface, trim the exhaust rubber whiskers and mold seam rubber edges, then weigh and assemble it on the test rim, fill it with the air pressure specified in Table 1, and park it according to the test conditions. Re-adjust the tire pressure after parking to the air pressure specified in Table 1. Fix the test tire and rim assembly on the rigidity testing machine. Mark the required test points on the sidewall of the tire. Select and mark the middle position of the letter "O" among the three letters of the DOT year and week number as the reference point, and use the corresponding tread as the contact surface of the imprint test. Measure the outer diameter and section width of the tire according to the provisions of GB / T 521. Place a pressure blanket connected to the sensor between the tire and the simulated road platform, set the acquisition frequency to 2 frames / s, apply a load to the tire at a speed of 25mm / min to the specified value, and maintain it for more than 2 minutes after loading. The above values ​​have the best stability. Through data processing, the contact area B1 and contact rate C1 are obtained. Remove the pressure blanket and perform longitudinal rigidity test preload: set the spindle speed to 20mm / min, which can obtain the best fitting value. Load radially from zero to the air pressure load specified in Table 1, maintain pressure for 1min; then press at a speed of 20mm / min. Figure 2 Move the test platform in the specified direction. For tires with radial load D×70%≤7000N, the longitudinal force reaches the radial load D×70%. For tires with radial load D×70%>7000N, the longitudinal force reaches 7000N. Then move the test platform back to the far point and unload the radial load as a pretreatment stage to eliminate tire stress and improve test accuracy. Set the spindle at a speed of 20mm / min, radially load the tire with the air pressure load specified in Table 1, and maintain the pressure for 1min. Then press at a speed of 20mm / min. Figure 2 Move the test platform in the specified direction, for tires with radial load D×70%≤7000N, until the longitudinal force reaches the radial load D×70%; for tires with radial load D×70%>7000N, until the longitudinal force reaches 7000N, and measure the change of longitudinal force with displacement; after the test platform moves to the origin, unload the radial load; repeat the above steps for the second and third rounds of tests, and obtain A1, B1, C1, A2, B2, and C2 respectively; calculate the average values ​​of the three groups of longitudinal rigidity, contact area, and contact rate, and obtain A, B, and C respectively.

[0061]

[0062] m and n are constants. The constants for different product types are shown in Table 2

[0063]

[0064] Table 2

[0065] Calculate the wet braking rate: Substitute the longitudinal rigidity, contact area, and contact rate into Formula 3

[0066] Wet braking rate = A×y+(B×z)×10 -2 +

(1-C)×10 2

[0067] y and z are constants. The constants for different product types are shown in Table 3.

[0068]

[0069] Table 3

[0070] The braking performance of a tire mainly comes from the friction between the tire and the road. There are two basic mechanisms: surface adhesion and hysteresis effect.

[0071] Surface adhesion is caused by the molecular bonding between rubber and road surface particles. When the road surface is dry, the friction caused by the adhesion effect is dominant. However, adhesion decreases significantly with water accumulation on the road surface, which is why friction decreases when the road surface becomes wet.

[0072] The hysteresis effect represents the energy loss inside the rubber caused by the deformation of the rubber when it slides on the road surface particles. The friction caused by the hysteresis effect is not greatly affected by the water on the road surface. Although a large hysteresis effect is beneficial for braking, it leads to higher energy consumption. With the improvement of environmental protection requirements, low hysteresis rubber is gradually used in tires.

[0073] The static rigidity performance test of tires can generally be divided into five categories: radial rigidity, lateral rigidity, longitudinal rigidity, torsional rigidity, and wrap rigidity. The test is used to detect the changes in pressure and shear force and displacement in all directions on the tire contact surface when the tire is statically grounded. The longitudinal rigidity refers to the longitudinal force required for a unit longitudinal displacement during braking, which is of great significance for studying the longitudinal vibration, braking force, traction, critical speed, and inflation pressure of tires, and can reflect the braking performance to a certain extent.

[0074] The contact test measures the distribution of various parameters of the tire on the static contact surface, so as to determine the various states of the contact area when the tire contacts the ground. The changes in various parameters of the contact area of ​​the contact tire under different test conditions are determined, including the footprint area, contact area, contact ratio, rectangular ratio, etc. The contact area refers to the total area of ​​the tread blocks in the tire contact area, and the contact ratio refers to the ratio of the contact area to the contact area. These two parameters can also reflect the braking performance of the tire to a certain extent.

[0075] The main factor affecting dry braking is the surface adhesion, which is related to the longitudinal rigidity and the ground contact area.

[0076] When braking on wet ground, due to the influence of water film, drainage performance must be considered in addition to surface adhesion, so it is also related to the ground contact rate.

[0077] A tire rigidity tester (or tire five-rigidity tester) capable of testing longitudinal rigidity requires a maximum measuring outer diameter of 1360mm; a load range of 0-7T, an accuracy of 1% FS; longitudinal / lateral displacement of 0mm-35mm; and a torsion angle of 0°-360°.

[0078] The pressure blanket with testable footprint ground contact area and ground contact rate requires maximum measurement dimensions: width 402.3mm × length 433.3mm; sensor size: 0.4×0.4mm; sensor spacing: 1.1×1.1mm; single sensor measurement pressure range: 15~300PSI (1.0~21.0kgf / cm2) pressure sensor overall accuracy (including force and area): ±5% PS; pressure sensor distance measurement accuracy: ±1.1mm; sampling frequency: maximum 70 times / second (adjustable).

[0079] This method is used to calculate different schemes for all-season tires 235 / 60R18 and compared with the final actual vehicle test data, which is consistent, as follows:

[0080] project Solution 1 Solution 2 Solution 3 A Longitudinal rigidity N / mm 143.9 137.9 127.6 <![CDATA[B grounding area mm 2 > 15571 15067 15214 C grounding rate 0.67 0.64 0.66 Dry braking rate 154 150 147 Wet braking rate 1149 1354 1212 Dry braking distance m (actual measurement) 37.9 38.39 39 Wet braking distance m (actual measurement) 30.07 29.2 30

[0081] Note: The shorter the dry and wet braking distance, the better the performance.

[0082] Dry braking rate: Scheme 1 > Scheme 2 > Scheme 3

[0083] Dry braking performance: Option 1 > Option 2 > Option 3

[0084] Wet braking rate: Scheme 2 > Scheme 3 > Scheme 1

[0085] Wet braking performance: Option 2 > Option 3 > Option 1

[0086] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0087] The tire braking performance detection method provided in the present application includes obtaining the longitudinal stiffness A, the contact area B and the contact ratio C of the tire; constructing a first calculation module for the tire dry braking ratio, and inputting the longitudinal stiffness and the contact area into the first calculation module; constructing a second calculation module for the tire wet braking ratio, and inputting the longitudinal stiffness, the contact area and the contact ratio into the second calculation module; calculating the dry braking ratio and the wet braking ratio of the tire according to the first calculation module and the second calculation module, respectively, being able to calculate the braking performance of the tire under different driving environments, thereby improving the accuracy of the tire braking performance detection, and adopting an integrated test of the rigidity test and the contact pressure test, being able to save costs and improve the detection efficiency.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting tire braking performance, characterized in that: include: Obtain the longitudinal stiffness A, contact area B and contact rate C of the tire; Construct a first calculation module for tire dry braking rate, and input the longitudinal stiffness and the contact area into the first calculation module: constructing a second calculation module for tire wet braking rate, and inputting the longitudinal stiffness, the contact area and the contact rate into the second calculation module; Wet braking rate = A×y+(B×z)×10 -2 +【(1-C)×10 2 】 2 ; Among them, m, n, y, and z are constants.

2. The tire braking performance detection method according to claim 1, characterized in that: Obtaining the longitudinal stiffness A of the tire comprises: placing the tire on a test platform; Controlling the tire to rotate at a first predetermined speed; Controlling the test platform to move at a second predetermined speed while applying a longitudinal force to the tire; The longitudinal force and the longitudinal displacement variation curve of the tire are obtained to obtain a calculation formula for the longitudinal rigidity of the tire.

3. The tire braking performance detection method according to claim 2, characterized in that: The longitudinal force and the tire displacement variation curve is: Among them, F x : longitudinal force, N; S x : longitudinal displacement, mm; a, b, c, d: correlation coefficients during curve fitting, dimensionless.

4. The tire braking performance detection method according to claim 3, characterized in that: The calculation formula for obtaining the longitudinal rigidity of the tire includes: The longitudinal force and the tire displacement variation curve are first-order derived to obtain the longitudinal rigidity calculation formula: Among them, L x : longitudinal stiffness, N / mm; S , x (F x ): S x (F x ) is the first-order derivative of .

5. The tire braking performance detection method according to claim 2, characterized in that: The step of obtaining the longitudinal stiffness A of the tire further comprises: Before controlling the tire to rotate at a first predetermined speed, a predetermined air pressure load is filled into the tire according to different specifications of the tire, and different longitudinal forces are applied to the tire according to the predetermined air pressure load value D.

6. The tire braking performance detection method according to claim 5, characterized in that: When the predetermined air pressure load value D×70%>7000N, the maximum value of the longitudinal force is 7000N; When the predetermined air pressure load value D×70%≤7000N, the maximum value of the longitudinal force is (D×70%)N.

7. The tire braking performance detection method according to claim 1, characterized in that: The method for obtaining the contact area B and the contact rate C includes: Placing the tire on a test platform, controlling the tire to run at a third predetermined speed, and collecting a pressure value of the tire on the test platform and a contact print of the tire; The contact area and contact rate are obtained according to the pressure value and the contact print.

8. The tire braking performance detection method according to claim 7, characterized in that: The method for obtaining the contact area B and the contact rate C further includes: The test platform is provided with a pressure detection component, and the acquisition frequency of the pressure detection component is set to a preset frequency threshold; applying a radial load to the tire to a preset load value while the tire is running at a third predetermined speed; After the radial load is applied to a preset load value, the tire maintains the preset load value to a preset time threshold.

9. The tire braking performance detection method according to claim 1, characterized in that: The method for obtaining the longitudinal stiffness A, the contact area B and the contact rate C of the tire includes: Acquire a plurality of the longitudinal stiffness values ​​A1, and calculate an average value of the plurality of the longitudinal stiffness values ​​A1 to obtain the longitudinal stiffness A; Acquire a plurality of the contact areas B1, and calculate an average value of the plurality of contact areas B1 to obtain the contact area B; A plurality of ground contact rates C1 are obtained, and an average value of the plurality of ground contact rates C1 is calculated to obtain the ground contact rate C.

10. The tire braking performance detection method according to claim 1, characterized in that: The tire braking performance detection method further includes: After the tire is vulcanized and left standing for a first set time, the tire is inflated and left standing for at least a second set time; Perform tire pressure monitoring on the tire that has been placed for at least the second set time. After the monitoring is qualified, obtain the tire for testing to obtain the longitudinal stiffness A, contact area B and contact rate C of the tire through an inflation test.

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