Tire real contact area measurement method and measurement device based on color retention method

Abstract

The application provides a tire real contact area with a road surface measurement method and a measurement device based on a color retention method, and the measurement method based on the color retention method includes: obtaining a contact area S of a tire tread and a road surface; measuring a proportion R of a tire ground contact area occupied by a tire tread pattern; coloring the bottom of a rubber block to simulate the situation of the tire pressing the road surface, pressing the colored rubber block on a road surface test piece, and measuring and calculating the proportion r of the pattern area of the rubber block to the contact area of the road surface test piece according to the color retention; and calculating the real contact area A of the tire and the road surface, and the calculation formula of the real contact area is A=SXRxr. The measurement method based on the color retention method provided by the application can more accurately obtain the real contact area of the tire and the road surface, has high measurement precision, and is helpful for the research on the friction between the tire and the road surface.

Description

Technical Field

[0001] This invention relates to the field of road engineering testing technology, and in particular to a method and device for measuring the true contact area of ​​tire pavement based on the color retention method. Background Technology

[0002] With improved driving conditions and increased traffic volume, vehicle speeds are rising, leading to a surge in traffic accidents. The high frequency of accidents is directly related to the decline in road surface anti-skid performance, especially in rainy weather when tire-road friction decreases. To increase tire-road contact friction and improve vehicle safety, tire surfaces typically have treads. Road surfaces, constructed from various sizes of gravel or sand and binders such as asphalt and cement, are usually rough, resulting in only partial contact between the tire and the road surface. The actual contact area between them is much smaller than the nominal contact area (the macroscopic area of ​​the contact surface, determined by the external dimensions of the contacting objects).

[0003] In the study of the mechanism of tire-road friction, adhesion and hysteresis are considered two important components of friction. Adhesion is mainly affected by the size of the actual contact area, while hysteresis is formed within the actual contact area by the damping effect of the tread rubber under contact stress excitation. Friction theory research results are usually presented as contact area or related contact stress distribution. Therefore, accurate testing of the tire-road contact area is crucial for the study of friction mechanisms and the verification of related friction theories. However, current technologies offer very little research on the actual contact area between tires and roads; calculations are generally based on theoretical contact areas, which introduce significant errors compared to actual contact conditions. In conclusion, exploring and verifying the actual contact area between tires and roads remains an unresolved issue. Summary of the Invention

[0004] This invention provides a method and device for measuring the true contact area between a tire and a road surface based on the color retention method, in order to solve the problem that the true contact area between the tire and the road surface cannot be accurately obtained in the prior art.

[0005] In a first aspect, the present invention provides a method for measuring the true contact area of ​​a tire road surface based on the color retention method, comprising:

[0006] Obtain the contact area S between the tire tread and the road surface;

[0007] Measure the ratio R of the tire tread pattern to the tire's contact area with the ground.

[0008] The bottom of the rubber block is colored to simulate the situation of a tire pressing against the road surface. The colored rubber block is pressed onto the road test piece. Based on the color retention, the ratio r of the pattern area of ​​the rubber block to the contact area of ​​the road test piece is measured.

[0009] Calculate the actual contact area A between the tire and the road surface. The formula for calculating the actual contact area is: A = S × R × r.

[0010] According to the method for measuring the true contact area between a tire and the road surface based on the color retention method provided by the present invention, obtaining the contact area S between the tire tread and the road surface includes:

[0011] Drive the vehicle to a relatively smooth surface, lift the wheels until the tire treads are off the ground, and place the first piece of white paper under the tires;

[0012] Rotate the side of the tire that is in contact with the ground, apply paint to the side, and then return the tire to its original position.

[0013] The vehicle is started, and the dyed tires come into contact with the first white paper, leaving the tire tread imprint on the first white paper;

[0014] Mark the outer edge of the imprint, and use the area enclosed by the outer edge of the imprint as the contact area S between the tire tread and the road surface.

[0015] According to the method for measuring the true contact area of ​​a tire surface based on the color retention method provided by the present invention, when the side surface is dyed with paint, the unfolded length of the pigmented portion of the tire tread is not less than 0.3m.

[0016] According to the method for measuring the true tire-road contact area based on the color retention method provided by the present invention, the measurement of the ratio R of the tire tread pattern to the tire ground contact area includes:

[0017] Drive the vehicle to a relatively smooth surface and place a second sheet of white paper in front of the tires;

[0018] The tire tread that is not in contact with the ground and is on the same side as the second white paper is dyed;

[0019] Drive the vehicle so that the dyed tires roll onto the surface of the white paper and leave a mark on the paper;

[0020] The imprint is obtained, and an image processor is used to identify the areas with color, and the number of pixels in the area and the number of pixels corresponding to the area inside the imprint are counted.

[0021] Based on the number of pixels in the region and the number of pixels corresponding to the area inside the imprint, the proportion of pixels in the dyed region to the number of pixels inside the imprint is calculated to obtain the proportion R of the tire tread pattern to the tire ground contact area.

[0022] According to the method for measuring the true contact area of ​​a tire road surface based on the color retention method provided by the present invention, when dyeing the tire tread coating that is not in contact with the ground and is on the same side as the second white paper, the spread length of the dyed part is not less than 0.45m.

[0023] The method for measuring the true contact area of ​​a tire road surface based on the color retention method provided by the present invention further includes, before coloring the bottom of the rubber block:

[0024] Prepare test specimens based on road surface conditions;

[0025] Select the appropriate rubber block based on the characteristics of the tire;

[0026] The test specimen and the rubber block are respectively installed on the measuring device.

[0027] According to the method for measuring the true contact area of ​​a tire road surface based on the color retention method provided by the present invention, the step of preparing a road test specimen according to the road surface conditions includes:

[0028] Use a scanner to acquire surface texture data of the road surface;

[0029] A three-dimensional model of the road surface is constructed based on the surface texture data, and the three-dimensional model of the road surface is input into a 3D printer.

[0030] The 3D printer is used to replicate the road test specimen that has the same surface morphology as the road surface.

[0031] According to the method for measuring the true contact area of ​​a tire on a road surface based on the color retention method provided by the present invention, the step of selecting the corresponding rubber block according to the characteristics of the tire includes:

[0032] The hardness values ​​at multiple locations on the highest point of the tire tread are read using a hardness tester, and the average hardness value is calculated. The average hardness value is used as the representative value of the tread rubber hardness.

[0033] Select a rubber block whose hardness differs from the representative value of the tread rubber by no more than 5 Shore hardness.

[0034] According to the method for measuring the true contact area of ​​a tire road surface based on the color retention method provided by the present invention, the ratio r of the rubber block tread area to the contact area of ​​the road test specimen is calculated as follows:

[0035]

[0036] Among them, Num pixel This refers to the number of pixels with a pixel value of 1, indicating the number of pixels corresponding to the area where color is retained;

[0037] Num totalThe total number of pixels refers to the number of pixels corresponding to the nominal contact area between the rubber block and the road test piece.

[0038] In a second aspect, the present invention also provides a measuring device for measuring the true contact area of ​​a tire road surface based on the color retention method as described in any one of the first aspects, comprising: an upper support frame, a lower support frame, and a pressure loading component;

[0039] The upper support frame and the lower support frame are arranged opposite to each other. The upper support frame is used to connect the rubber block, and the lower support frame is used to place the road test specimen.

[0040] The pressure loading component is connected to the upper support frame. Under the action of the pressure loading component, the upper support frame can drive the rubber block to abut against the road test piece and leave an imprint on the road test piece.

[0041] The present invention provides a method for measuring the true contact area of ​​a tire against a road surface based on the color retention method. First, the contact area between the tire tread and the road surface is obtained, yielding the tire's ground contact area S. Then, the nominal contact area R between the tire and the road surface is measured again using the color retention method. Further, the tire's pressure on the road surface is simulated using a rubber block and a road test specimen. Dye from the bottom of the rubber block is transferred to the road test specimen. The proportion r of the rubber block's tread area to the road test specimen's contact area is calculated based on the imprint and dyed area on the road test specimen. Finally, based on the aforementioned contact area S, nominal contact area R, and proportion r of the rubber block's tread area to the road test specimen's contact area, and using the formula A = S × R × r, the true contact area A between the tire and the road surface is calculated, thus obtaining the true contact area A. Therefore, the tire-road surface contact area measurement method based on the color retention method provided by the present invention, compared to existing intuitive measurement methods, can more accurately obtain the true contact area between the tire and the road surface, offering high measurement precision and contributing to the study of tire-road friction.

[0042] The device for measuring the true contact area of ​​a tire road surface based on the color retention method provided by this invention has all the beneficial effects of the aforementioned method for measuring the true contact area of ​​a tire road surface based on the color retention method, since it is applied to the method for measuring the true contact area of ​​a tire road surface based on the color retention method to obtain the ratio of the rubber block pattern area to the contact area of ​​the road test specimen.

[0043] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted by the present invention, and the advantages brought about by the technical features of these technical solutions as described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings, or will be learned through the practice of the present invention. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic flowchart of the method for measuring the true contact area of ​​a tire road surface based on the color retention method provided in an embodiment of the present invention;

[0046] Figure 2 This is an image of the contact surface between the tire tread and the road surface provided in an embodiment of the present invention;

[0047] Figure 3 This is an embodiment of the present invention that uses an image processor to obtain the imprint image of the tire tread pattern;

[0048] Figure 4 This is a colored image of a road test specimen surface obtained using the scanning function of a printer, as provided in an embodiment of the present invention.

[0049] Figure 5 This is an image of the imprint left on a stained road test specimen, obtained using an image processor, provided in an embodiment of the present invention.

[0050] Figure 6 This is a schematic diagram of the structure of the device for measuring the true contact area of ​​a tire road surface based on the color retention method provided in an embodiment of the present invention;

[0051] Figure label:

[0052] 1: Upper support frame; 11: Force transmission frame; 12: Force transmission plate; 2: Fixing pin; 3: Pressure loading component; 4: Lower support frame; 41: Flange; 42: Limit screw; 5: Pressure loading pad; 6: Rubber block. Detailed Implementation

[0053] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0054] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0057] Furthermore, in the description of the embodiments of the present invention, unless otherwise stated, "multiple", "multiple roots", and "multiple groups" mean two or more, and "several", "several roots", and "several groups" mean one or more.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] The following is combined Figures 1 to 6 This invention describes a method and apparatus for measuring the true contact area of ​​a tire road surface based on the color retention method, as provided in embodiments of the present invention.

[0060] Firstly, such as Figure 1 As shown, the method for measuring the true contact area of ​​a tire road surface based on the color retention method in this embodiment of the invention includes:

[0061] Step 100: Obtain the contact area S between the tire tread and the road surface.

[0062] Step 200: Measure the ratio R of the tire tread pattern to the tire's contact area with the ground.

[0063] Step 300: Paint the bottom of the rubber block to simulate the situation of a tire pressing against the road surface. Press the colored rubber block onto the road test piece. Based on the color retention, measure and calculate the ratio r of the rubber block pattern area to the contact area of ​​the road test piece.

[0064] Step 400: Calculate the actual contact area A between the tire and the road surface. The formula for calculating the actual contact area is: A = S × R × r.

[0065] Specifically, the method for measuring the true contact area of ​​a tire with the road surface based on the color retention method provided in this embodiment of the invention first obtains the contact area between the tire tread and the road surface to obtain the tire's ground contact area S; then, the proportion R of the tire tread pattern to the tire's ground contact area is measured again using the color retention imprint method; further, the tire's pressing on the road surface is simulated using a rubber block and a road test specimen, and the dye at the bottom of the rubber block is imprinted onto the road test specimen. The proportion r of the rubber block pattern area to the road test specimen's contact area is calculated based on the imprint and dyed area on the road test specimen; finally, based on the aforementioned contact area S between the tire tread and the road surface, the proportion R of the tire tread pattern to the tire's ground contact area, and the proportion r of the rubber block pattern area to the road test specimen's contact area, and the calculation formula: A = S × R × r, the true contact area A between the tire and the road surface is calculated, thus obtaining the true contact area between the tire and the road surface.

[0066] Therefore, the method for measuring the true contact area between the tire and the road surface based on the color retention method provided in this embodiment of the invention can more accurately obtain the true contact area between the tire and the road surface compared with the intuitive measurement method of the prior art. It has high measurement accuracy and is helpful for the study of tire-road friction.

[0067] In an optional embodiment, obtaining the contact area S between the tire tread and the road surface includes:

[0068] Step 110: Drive the vehicle to a relatively smooth surface, lift the wheels until the tire treads are off the ground, and place the first piece of white paper under the tires.

[0069] Step 120: Rotate the side of the tire that is in contact with the ground, apply paint to the side, and then put the tire back in place.

[0070] Step 130: Start the vehicle, and the dyed tires come into contact with the first white paper, leaving tire tread marks on the first white paper.

[0071] Step 140: Mark the outer edge of the imprint, and use the area enclosed by the outer edge of the imprint as the contact area S between the tire tread and the road surface.

[0072] Specifically, in practice, you can first drive the vehicle to a relatively smooth surface. This surface can be a flat and smooth road surface similar to a cement floor or a tile bottom, but not a road surface with a high degree of roughness, such as an asphalt road. Use a jack to lift one wheel so that the wheel is completely off the ground and can rotate freely, and place an A3-sized piece of white paper under the tire.

[0073] Then, turn the part of the tire that is in contact with the ground to the side and apply the paint, then turn the tire back to its original position.

[0074] Then, the jack was slowly removed, the vehicle was started, and the dyed tires gradually came into contact with the white paper, leaving tire marks on the surface of the paper.

[0075] Finally, mark the outer edge of the tire imprint; the area enclosed by the outer edge of the imprint is taken as the tire's contact patch area. Figure 2 As shown, by using the grid counting method to count the area enclosed by the outer edge of the imprint, the contact area S between the tire tread and the road surface can be obtained. In this embodiment of the invention, it is as follows: Figure 2 The contact area S between the tire tread and the road surface shown is 41400 mm². 2 .

[0076] When applying paint to the sidewalls, the spread length of the paint-coated portion of the tire tread shall not be less than 0.3m.

[0077] In an optional embodiment, measuring the ratio R of the tire tread pattern to the tire's contact area with the ground includes:

[0078] Step 210: Drive the vehicle to a smoother surface and place a second sheet of white paper in front of the tires.

[0079] Step 220: Apply paint to the tire tread that is not touching the ground and is on the same side as the second white paper.

[0080] Step 230: Start the vehicle so that the dyed tires roll onto the surface of the white paper and leave a mark on the paper.

[0081] Step 240: Obtain the imprint and use an image processor to identify the areas with color, count the number of pixels in the area and the number of pixels corresponding to the area inside the imprint.

[0082] Step 250: Based on the number of pixels in the region and the number of pixels corresponding to the area inside the imprint, calculate the ratio of the pixels in the stained area to the number of pixels inside the imprint, and obtain the ratio R of the tire tread pattern to the tire ground contact area.

[0083] Specifically, first, as above, drive the vehicle onto a relatively smooth surface. This surface can be a flat, smooth road surface similar to a cement floor or a tiled surface, but not a surface with a high degree of roughness, such as an asphalt road. Place an A3-sized piece of white paper in front of the tires.

[0084] Then, paint is applied to the part of the tire tread that is not touching the ground and is on the same side as the white paper.

[0085] Then, start the vehicle so that the dyed tire slowly rolls onto the surface of the white paper and leaves a mark of the dyed tire tread on the white paper. The length of the mark should be equal to the unfolded length of the dyed tire tread.

[0086] Finally, the printer's scanning function was used to obtain the imprint left by the stained tire. The scanning resolution was set to 1200 DPI (Dots Per Inch). The outer edge of the imprint was marked, and an image processor, such as ImageJ software, was used to identify the colored areas and count the number of pixels in those areas and the number of pixels corresponding to the area inside the imprint, as shown below. Figure 3 The image shown is used to calculate the proportion of the number of pixels in the stained area to the number of pixels in the area inside the imprint, which gives the proportion R of the tire tread pattern to the tire's ground contact area.

[0087] In an embodiment of the present invention, one example is: Figure 3 As shown, the number of pixels corresponding to the stained area is 162411, and the number of pixels inside the imprint is 232016. Therefore, the ratio of the tire tread pattern to the tire contact area is R = 162411 / 232016 = 0.70.

[0088] Specifically, when dyeing the tire tread that is not touching the ground and is on the same side as the second white paper, the spread length of the painted part shall not be less than 0.45m.

[0089] In an optional embodiment, before coloring the bottom of the rubber block, the following steps are also included:

[0090] Prepare road test specimens according to road surface conditions.

[0091] Choose the appropriate rubber block based on the characteristics of the tire.

[0092] The test specimen and the rubber block were respectively installed on the measuring device.

[0093] The preparation of road test specimens based on road surface conditions includes:

[0094] Use a scanner to acquire surface texture data of the road surface.

[0095] A 3D model of the road surface is constructed based on surface texture data, and then the 3D model of the road surface is input into a 3D printer.

[0096] A road test specimen with the same surface morphology as the road surface is replicated using a 3D printer.

[0097] Specifically, test specimens can be obtained through core drilling, indoor molding, or 3D printing technologies.

[0098] In some embodiments, road test specimens are prepared by drilling cores on the road surface or forming test specimens indoors. The operation procedure can be followed according to the relevant specifications. It should be noted that road test specimens with a dark surface color obtained by drilling or forming need to be coated with white paint. The white paint should be applied evenly while controlling the thickness to within 0.01 mm to minimize the impact on the original texture of the road test specimen. Finally, the white-painted specimens are cut into pieces with an area of ​​not less than 60×60 mm using a double-sided saw. 2 The shape is square.

[0099] In other embodiments, 3D printing technology can be used to obtain road test specimens. The main process includes: first, using a 3D scanner to acquire surface texture data. The scanner resolution should not be lower than 0.1 mm and the accuracy should not be lower than 0.04 mm to ensure that enough detailed road texture information is captured; then, reconstructing a 3D model of the road surface based on the surface point cloud obtained from the 3D scan, inputting the model into a 3D printer, and using 3D printing to replicate a specimen with the same surface morphology as the scanned road surface. The printing material is light-colored resin.

[0100] Furthermore, a rubber block representative of the tread rubber properties should be selected. Different patterns on the tire surface result in varying tread hardness, thus affecting its contact characteristics with the road surface. Therefore, the measurement method provided in this embodiment should use hardness as the standard for selecting rubber, that is, selecting the corresponding rubber block according to the tire's characteristics, including:

[0101] A hardness tester is used to read hardness values ​​at multiple locations on the highest point of the tire tread, and the average hardness is calculated. The average hardness is used as the representative value of the tread rubber hardness.

[0102] In this embodiment of the invention, a rubber block with a Shore hardness not exceeding 5 compared to the representative hardness value of the tread rubber is selected. The bottom surface of the rubber block has a side length or diameter of not less than 60 mm and a thickness of 10 mm.

[0103] In an optional embodiment, the ratio r of the rubber block pattern area to the contact area of ​​the road test piece is calculated as follows:

[0104]

[0105] Among them, Num pixel＝1 This refers to the number of pixels with a pixel value of 1, indicating the number of pixels corresponding to the area where color is retained;

[0106] Num total The total number of pixels refers to the number of pixels corresponding to the nominal contact area between the rubber block and the road test piece.

[0107] Specifically, the bottom of the rubber block is coated with color, and the dye should be thin-coated and have good adhesion. The loading time and load size are set at the control end of the measuring device. The specific parameters of the loading time and load size are not limited and can be set according to actual needs.

[0108] After pressure loading and unloading, the test specimen was removed. The contact area between the rubber block and the test specimen was marked at the locations where dye remained. The surface image of the specimen with the remaining color was obtained using the printer's scanning function, as shown below. Figure 4 The image shown.

[0109] Finally, ImageJ software was used to identify the colored areas through threshold segmentation, and the number of pixels occupied by the nominal contact area of ​​the rubber-road test piece and the number of pixels occupied by the colored areas were counted. Figure 5 As shown, the ratio r of the number of pixels in the color area to the number of pixels corresponding to the road test specimen is used as the percentage of the rubber-road surface contact area. The nominal rubber-road surface contact area is the smaller of the projected areas of the road test specimen surface and the bottom surface of the rubber block.

[0110] In this embodiment of the invention, the rubber bottom surface is a circle with a diameter of 60mm, and the bottom projection of the road test piece is a square with a side length of 60mm, such as... Figure 5 As shown, the number of pixels corresponding to the square bottom surface of the specimen is 6696, the number of pixels corresponding to the colored area is 823, the nominal contact area between the rubber and the road surface is equal to the area corresponding to the bottom surface of the rubber sheet, and the proportion of the contact area between the rubber and the road surface is r = 823 / (6696 / (60×60)×3.14×(60 / 2)). 2 ) = 0.156 = 15.6%.

[0111] The actual contact area between the rubber and the road surface is obtained by multiplying the rubber-to-road contact area ratio r by the tire contact area S, and then multiplying by the ratio R of the tire tread pattern to the tire-to-road contact area. Therefore, according to the formula for calculating the actual contact area A between the tire and the road surface: A = S × R × r, A = 41400 × 0.70 × 15.6% = 4520.88 mm 2 .

[0112] Secondly, embodiments of the present invention also provide a measuring device for the method of measuring the true contact area of ​​a tire road surface based on the color retention method in the first aspect. It includes: an upper support frame 1, a lower support frame 4, and a pressure loading member 3.

[0113] The upper support frame 1 and the lower support frame 4 are arranged opposite to each other. The upper support frame 1 is used to connect the rubber block 6, and the lower support frame 4 is used to place the road test piece.

[0114] The pressure loading component 3 is connected to the upper support frame 1. Under the action of the pressure loading component 3, the upper support frame 1 can drive the rubber block 6 to abut against the road test piece and leave an imprint on the road test piece.

[0115] Specifically, such as Figure 6 As shown, the upper support frame 1 includes a force transmission frame 11 and a force transmission plate 12 located at the bottom. Its function is to transmit pressure load and install rubber block 6. The vertical part of the force transmission frame 11 has a small round hole at the end. The fixing pin 2 can pass through the small round hole to connect the pressure loading member 3 and the force transmission frame 11. The rubber block 6 is installed on the bottom surface of the force transmission plate 12 by adhesive bonding.

[0116] The lower support frame 4 includes a flange 41 with holes on four sides and limiting screws 42 located on the four sides of the flange 41. The purpose of the flange 41 is to place the road test piece and restrict the horizontal movement of the road test piece.

[0117] In addition, the flange 41 has a stud in the center, which is used to install the flange 41 onto the pressure loading pad 5. At the same time, the flange 41 and the force transmission plate 12 are vertically aligned, which can center the rubber block 6 and the test specimen in the longitudinal direction to ensure the pressing effect.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the true contact area of ​​a tire road surface based on the color retention method, characterized in that, include: Obtain the contact area S between the tire tread and the road surface; Measure the ratio R of the tire tread pattern to the tire's contact area with the ground. The bottom of the rubber block is colored to simulate the situation of a tire pressing against the road surface. The colored rubber block is pressed onto the road test piece. Based on the color retention, the ratio r of the pattern area of ​​the rubber block to the contact area of ​​the road test piece is measured and calculated. Calculate the actual contact area A between the tire and the road surface. The formula for calculating the actual contact area is: A = S × R × r; The step of obtaining the contact area S between the tire tread and the road surface includes: Drive the vehicle to a relatively smooth surface, lift the wheels until the tire treads are off the ground, and place the first piece of white paper under the tires; Rotate the side of the tire that is in contact with the ground, apply paint to the side, and then return the tire to its original position. The vehicle is started, and the dyed tires come into contact with the first white paper, leaving the tire tread imprint on the first white paper; Mark the outer edge of the imprint, and use the area enclosed by the outer edge of the imprint as the contact area S between the tire tread and the road surface.

2. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 1, characterized in that, When applying paint to the sidewall, the unfolded length of the paint-coated portion of the tire tread is not less than 0.3m.

3. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 1, characterized in that, The ratio R of the tire tread pattern to the tire's contact area with the ground includes: Drive the vehicle to a relatively smooth surface and place a second sheet of white paper in front of the tires; The tire tread that is not in contact with the ground and is on the same side as the second white paper is dyed; Drive the vehicle so that the dyed tires roll onto the surface of the white paper and leave a mark on the paper; The imprint is obtained, and an image processor is used to identify the areas with color, and the number of pixels in the area and the number of pixels corresponding to the area inside the imprint are counted. Based on the number of pixels in the region and the number of pixels corresponding to the area inside the imprint, the proportion of pixels in the dyed region to the number of pixels inside the imprint is calculated to obtain the proportion R of the tire tread pattern to the tire ground contact area.

4. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 3, characterized in that, When dyeing the tire tread that is not touching the ground and is on the same side as the second white paper, the spread length of the dyed portion shall not be less than 0.45m.

5. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 1, characterized in that, Before coloring the bottom of the rubber block, the process also includes: Prepare test specimens based on road surface conditions; Select the appropriate rubber block based on the characteristics of the tire; The test specimen and the rubber block are respectively installed on the measuring device.

6. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 5, characterized in that, The preparation of road test specimens based on road surface conditions includes: Use a scanner to acquire surface texture data of the road surface; A three-dimensional model of the road surface is constructed based on the surface texture data, and the three-dimensional model of the road surface is input into a 3D printer. The 3D printer is used to replicate the road test specimen that has the same surface morphology as the road surface.

7. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 6, characterized in that, The step of selecting the corresponding rubber block according to the characteristics of the tire includes: The hardness values ​​at multiple locations on the highest point of the tire tread are read using a hardness tester, and the average hardness value is calculated. The average hardness value is used as the representative value of the tread rubber hardness. Select a rubber block whose hardness differs from the representative value of the tread rubber by no more than 5 Shore hardness.

8. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 1, characterized in that, The ratio r of the rubber block pattern area to the contact area of ​​the road test piece is calculated as follows: Among them, Num pixel＝1 This refers to the number of pixels with a pixel value of 1, indicating the number of pixels corresponding to the area where color is retained; Num total The total number of pixels refers to the number of pixels corresponding to the nominal contact area between the rubber block and the road test piece.

9. The method for measuring the true contact area of ​​a tire road surface based on the color retention method according to claim 1, characterized in that, The method for measuring the true contact area of ​​a tire on a road surface based on the color retention method is performed using a measuring device. The measuring device includes: Upper support frame, lower support frame, and pressure loading components; The upper support frame and the lower support frame are arranged opposite to each other. The upper support frame is used to connect the rubber block, and the lower support frame is used to place the road test specimen. The pressure loading component is connected to the upper support frame. Under the action of the pressure loading component, the upper support frame can drive the rubber block to abut against the road test piece and leave an imprint on the road test piece.

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