JP4322642B2 - Tire contact image analysis method, tire contact image analysis apparatus, and tire contact image analysis program - Google Patents

Description

  The present invention relates to a tire ground contact image analysis method, a tire ground contact image analysis apparatus, and a tire ground contact image analysis program. More specifically, the present invention relates to a tire ground contact image analysis method for approximating a tire ground contact shape as a function from acquired tire ground contact image data. The present invention relates to an image analysis apparatus and a tire ground contact image analysis program.

  A pneumatic tire (hereinafter simply referred to as a “tire”) is a power source of an engine or the like mounted on a vehicle such as a vehicle in contact with the road surface so that a moving body such as a vehicle moves on a target surface such as a road surface. It is the only one that transmits power from the source to the target surface. Therefore, the performance of the tire has a great influence on the motion performance of the vehicle. The tire performance includes evaluation items such as noise performance, friction performance, steering stability performance, and braking performance, and these evaluation items vary depending on the tire ground contact characteristics. The tire contact characteristics include a contact area, an average pressure based on a load and a contact area, a maximum contact length in the tire circumferential direction (contact length direction), and a maximum contact width in the tire width direction (contact width direction). In order to obtain these tire contact characteristics with high accuracy, the tire contact shape when the tire is in contact with the target surface, in particular, the contour line constituting the tire contact surface when the tire is in contact with the target surface must be determined with high accuracy. is important.

Therefore, conventionally, a technique has been proposed in which image analysis of tire ground contact image data is performed to obtain a tire ground contact shape and a tire ground contact characteristic (see, for example, Patent Document 1). In this conventional technique, a tire contact shape is repeatedly obtained by combining a procedure for expanding and contracting until one filled block is obtained in a procedure for image analysis of tire contact image data.
Japanese Patent No. 3293670

  However, in the above-described conventional technique, repeating the expanding procedure and the contracting procedure performed in the image analysis procedure increases the calculation time for obtaining the tire ground contact shape. In general, the image analysis of the image data requires enormous calculation, so that the calculation amount for obtaining the tire contact shape increases. Therefore, it is difficult to use a PC (personal computer) having a relatively low processing speed, and there is a problem that a dedicated tire ground contact image analyzing apparatus having a high processing speed is required. Further, the obtained tire ground contact shape is pixel data such as a pixel image, and the amount of data is large. Further, the tire ground contact shape varies depending on the position of the tread surface of the tire that contacts the road surface. Furthermore, there are many types of tires, and these tire ground contact shapes also differ depending on the ground contact conditions such as the internal pressure of the tire and the load on the target surface. Therefore, it is possible to obtain individual tire contact shapes by changing the position of the tread surface of the tire to be in contact with the road surface, the type of tire, and the contact condition of the tire, and to store the obtained tire contact shapes as data, that is, to create a database. It was difficult.

  Accordingly, the present invention has been made in view of the above, and aims to reduce the amount of data of the obtained tire contact shape by reducing the calculation time for calculating the tire contact shape and reducing the amount of calculation. An object of the present invention is to provide a tire contact image analysis method, a tire contact image analysis apparatus, and a tire contact image analysis program.

  In order to achieve the above object, in the present invention, a procedure for acquiring tire contact image data, a procedure for determining arbitrary coordinates in the tire contact shape from the acquired tire contact image data, and extending from the arbitrary coordinates for each sample angle. Approximate the intersection point between the straight line and the tire contact shape contour line, and the tire contact shape contour line from the sample angle and the length of the straight line to the intersection point determined from the arbitrary coordinates, and obtain the contact shape function. Including a procedure. Here, the contour line of the tire ground contact shape is an outer periphery of the tire ground contact surface in a case where all the grooves formed on the tread surface of the tire are not present, and a tire ground contact surface of a circumferential groove which is a groove in the tire circumferential direction. The outer circumference of the lug groove that is a groove in the tire width direction on the tire ground contact surface, the outer circumference on the tire ground contact surface of a set of blocks in which at least one side surface forms a tread surface adjacent to the circumferential groove, one block The outer periphery of the tire ground contact surface.

  According to this invention, the contact shape function of the contour line of the tire contact shape is obtained from the tire contact image data, that is, the tire contact shape is approximated by one function. Therefore, it is not necessary to obtain the pixel data such as the pixel image of the tire contact shape by repeatedly expanding and contracting from the tire contact image data as in the past, and the calculation time for calculating the tire contact shape is shortened and the calculation amount is reduced. Can be achieved. Further, since the tire ground contact shape obtained as in the prior art is not pixel data such as a pixel image but a contact shape function, the data amount of the tire ground contact shape can be reduced.

  In the present invention, the arbitrary coordinate in the tire ground contact shape is a center point in the tire ground contact shape. According to the present invention, since the length of the straight line from the arbitrary coordinate for each sample angle to the intersection obtained is stable, i.e., does not change drastically, the tire contact shape contour is approximated by a contact shape function having a low order. Can do. Accordingly, it is possible to further reduce the calculation time and the calculation amount for obtaining the contact shape function. In addition, since the contact shape function can be approximated by a low-order contact shape function, the data amount of the tire contact shape can be further reduced as compared with a complex contact shape function having a high order.

  Further, in the present invention, the tire contact shape contour line is an average value of the tire contact shape contour line that overlaps when the tire contact shape is folded symmetrically from the center point or rotated point symmetrically from the center point. It is either an outer value or an innermost value.

  According to the present invention, the front / rear, left / right or front / rear / left / right of the tire contact surface of the tire contact image data with variation is averaged. As a result, since the contour line of the tire ground contact shape is averaged in the front / rear direction, the left / right direction, or the front / rear left / right direction, the accuracy of the tire contact property calculated from the obtained contact shape function can be achieved.

  In the present invention, the ground contact shape function is a Fourier series or a polynomial. According to the present invention, by using the Fourier series for the ground contact shape function, it is possible to improve the approximate performance for the contour line of the tire ground contact shape. On the other hand, by using a polynomial for the contact shape function, the calculation time can be shortened and the amount of calculation can be reduced.

Further, in the present invention, the required contact shape function sequentially increases the order of the contact shape function, and the correlation coefficient R ² between the contact shape function and the tire contact shape in which the order increases sequentially becomes 0.9 or more. When the order of the first contact shape function is N, the contact shape function is a contact shape function whose order is N to N + 2.

According to the present invention, the correlation coefficient R ² to ground contact shape function is required by 0.9 or more, it is possible to prevent deterioration from contact shape function of accuracy in calculating the tire contact characteristic calculated it can. In addition, when the order of the first contact shape function having a correlation coefficient R ² of 0.9 or more is N, the obtained contact shape function is a contact shape function whose order is N to N + 2. In addition, an increase in the amount of tire ground contact data can be prevented.

  Further, according to the present invention, processing means for processing each procedure in the tire contact image analysis method, tire contact image data, input means for giving other data to the processing means, contact shape function by the processing means, tire contact image And a display means for displaying the analysis result.

  According to the present invention, the tire ground contact image analyzing apparatus includes processing means for executing the tire ground contact image analyzing method. Therefore, the contact shape function of the contour line of the tire contact shape is obtained from the tire contact image data acquired by the input means, that is, the tire contact shape is approximated by one function. Therefore, it is not necessary to obtain the pixel data such as the pixel image of the tire contact shape by repeatedly expanding and contracting from the tire contact image data as in the past, and the calculation time for calculating the tire contact shape is shortened and the calculation amount is reduced. Can be achieved. Further, since the tire ground contact shape obtained in the conventional manner is not a pixel image but a ground contact shape function, the data amount of the tire ground contact shape can be reduced.

  The present invention is characterized in that a computer executes the tire ground contact image analysis method. According to the present invention, by causing the computer to read and execute the program, the tire ground contact image analysis method can be realized using the computer, and the same effects as those of these methods can be obtained.

  According to the tire ground contact image analysis method according to the present invention, the tire ground contact image analysis can be performed even using a PC or the like whose processing speed is not relatively high. In addition, it is easy to store the obtained tire contact shape as data, that is, to create a database. In addition, it is possible to improve the accuracy of tire contact characteristics calculated from the determined contact shape function.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  FIG. 1 is a diagram showing a configuration example of a tire ground contact image analyzing apparatus that executes the tire ground contact image analyzing method according to the present invention. The tire ground contact image data is generated by the imaging device 2, and the generated tire ground contact image data is input to a tire ground contact image analyzing device 3 described later. The imaging device 2 includes a sheet-like medium 2a, a support substrate 2b, and a camera 2c.

  The sheet-like medium 2a is placed on the support substrate 2b and is a cardboard, paper, or other appropriate sheet-like material having a certain thickness and area. The support substrate 2b is formed of a tempered glass that supports the tire 1 with a predetermined load and has transparency. The camera 2c is, for example, a CCD camera or the like, and images the grounding state of the tire 1 with respect to the support substrate 2b via the sheet-like medium 2a by applying light from an illumination lamp (not shown) from the back surface of the support substrate 2b. . The camera 2c is obtained by applying a transfer material such as black ink or vermilion to the tread surface 1a of the tire 1 in advance without using the sheet medium 2a and the support substrate 2b, and transferring the transfer material to a transfer material such as paper. The ground contact state of the obtained tire 1 may be imaged.

  Here, the camera 2c A / D converts the ground contact state of the imaged tire 1 from an analog state to a digital state, that is, tire ground contact image data. Here, the converted tire ground contact image data may be either binarized image data or grayscale image data.

  The tire ground contact image analyzing apparatus 3 includes a storage unit 3a and a processing unit 3b which are processing means. An input / output device 4 is connected to the tire ground contact image analyzing device 3, and an input unit 4 a provided therein directly stores tire ground contact image data generated by the imaging device 2 as a storage unit 3 a or a processing unit. A command to be input to 3b is given. In addition, other data such as the type of the tire 1 imaged and the grounding condition of the tire 1 are given to the storage unit 3a and the processing unit 3b. Note that the input unit 4a may indirectly input the tire ground contact image data generated by the imaging device 2 to the storage unit 3a or the processing unit 3b. That is, the tire ground contact image data generated from the ground contact state of the tire 1 imaged at another location is not directly input to the tire ground contact image analysis device 3 from the image capturing device 2. You may input into the analysis apparatus 3. FIG. Here, input devices such as a keyboard, a mouse, and a microphone can be used as the input means 4a.

  The storage unit 3a stores a tire contact image analysis program in which the tire contact image analysis method of the present invention for realizing the tire contact image analysis method of the present invention is incorporated. Here, the storage unit 3a is a fixed disk device such as a hard disk device, a flexible disk, a magneto-optical disk device, or a non-volatile memory such as a flash memory (a storage medium that can only be read such as a CD-ROM), It can be constituted by storage means such as a volatile memory such as RAM (Random Access Memory), or a combination thereof.

  The tire ground contact image analysis program is not necessarily limited to a single configuration, but cooperates with a program already stored in a computer system, for example, a separate program represented by an OS (Operating System). It is also possible to achieve this function. Further, a tire ground contact image analysis program for realizing the function of the processing unit 3b shown in FIG. 1 is stored in a computer-readable recording medium, and the tire ground contact image analysis program recorded on the recording medium is read into a computer system. The tire ground contact image analysis method according to the present invention may be executed by executing the method. The “computer system” here includes an OS and hardware such as peripheral devices.

  The processing unit 3b includes a memory such as a RAM and a ROM, and a CPU (Central Processing Unit). In the tire contact image analysis, the processing unit 3b stores the tire contact image analysis program in a memory (not shown) of the processing unit 3b based on the tire contact image data acquired by the tire contact image analysis device 3 as described above. Read and perform calculations. Note that the processing unit 3b appropriately stores a numerical value in the middle of the calculation in the storage unit 3a, and appropriately calculates the stored numerical value from the storage unit 3a. The processing unit 3b may be realized by dedicated hardware instead of the tire ground contact image analysis program.

  The contact shape function, the tire contact image analysis result, and the like calculated by the processing unit 3b are displayed by the display unit 4b of the input / output device 4. Here, a CRT (Cathode Ray Tube), a liquid crystal display device, or the like can be used as the display means 4b. Further, the obtained contact shape function, tire contact image analysis result, and the like can be output to a printer (not shown). The storage unit 3a may be provided in the processing unit 3b, or may be provided in another device (for example, a database server). Moreover, the structure which can access the tire grounding image-analysis apparatus 3 by a wired or wireless method from the terminal device which is not shown provided with the input / output device 4 may be sufficient.

  Next, a tire ground contact image analysis method will be described. Here, the case where the tire ground contact shape is the tire ground contact surface when all the grooves formed on the tread surface 1a of the tire 1 do not exist will be described. In addition to the above, the tire contact shape includes a circumferential groove that is a tire circumferential groove on the tire contact surface, a lug groove that is a tire width groove on the tire contact surface, and at least one side surface of the tire contact surface. It may be a set of blocks forming a tread surface adjacent to the directional groove, one block on the tire ground contact surface, or the like.

  FIG. 2 is a view showing a flowchart of the tire ground contact image analyzing method according to the present invention. 3-5 is explanatory drawing for calculating | requiring the intersection of the outline of a tire ground-contact shape, and a straight line. FIG. 6A is a diagram illustrating a contour line of the obtained tire ground contact shape. FIG. 6B is a diagram illustrating a relationship between the amplitude (straight line L) and the sample angle. FIG. 7-1 is a diagram illustrating an outline of a tire ground contact shape after averaging. FIG. 7B is a diagram illustrating a relationship between the amplitude after the averaging (straight line L) and the sample angle. 8 to 9 are explanatory diagrams for obtaining the ground contact shape function. FIG. 10 is a diagram showing a contact shape function obtained by the tire contact image analysis method according to the present invention. Here, except for FIGS. 6-2, 7-2, and 8, the Y axis is the circumferential direction of the tire 1, that is, the contact length direction, and the X axis is the width direction of the tire 1, that is, the contact width direction.

  First, as shown in FIG. 2, in the tire contact image analysis method according to the present invention, first, the tire contact image analysis device 3 acquires the tire contact image data 10 imaged at the image pickup device 2 or another place as described above. (Step ST1). As shown in FIG. 3, the tire contact image data 10 acquired by the tire contact image analysis device 3 includes a plurality of pixel data, and is, for example, binarized image data or grayscale image data.

  Next, an arbitrary coordinate within the tire contact shape, that is, the center point A of the tire contact surface 11 is calculated from the acquired tire contact image data 10 (step ST2). The calculation of the center point A by the processing unit 3b of the tire ground contact image analyzing apparatus 3 is performed as follows, for example. First, as shown in FIG. 4, lines 12 a and 12 b parallel to the Y axis that determine the maximum contact width (width direction) of the tire contact surface 11 in the tire contact image data 10 are determined. Next, the lines 13a and 13b parallel to the X axis that maximize the contact length (circumferential direction) of the tire contact surface 11 are determined. Next, a quadrangle 14 surrounding the tire ground contact image data 10 is formed from these parallel lines 12a to 13b. Then, an intersection of lines (lines parallel to the X and Y axes) 15a and 15b connecting the half positions of the opposing sides of the quadrangle 14 is set as a center point A, and the XY coordinates of the intersection are determined. Is called. Here, the arbitrary coordinates are not limited to the center point of the tire ground contact shape, and may be any point within the tire ground contact shape.

  Next, an intersection B between the straight line L extending from the arbitrary coordinates for each sample angle θ and the contour line of the tire ground contact shape is obtained, that is, the straight line L extending from the center point A which is an arbitrary coordinate and the contour line of the tire ground contact surface 11. The intersection point B is obtained (step ST3). As shown in FIG. 5, first, the processing unit 3b determines the sample angle θ (for example, every 1 °) of the straight line L extending from the center point A with reference to the line 16 parallel to the X axis extending from the center point A. To do. Next, a straight line L with the sample angle θ of 1 ° is extended from the center point A toward the outside of the tire ground contact surface 11 having a tire ground contact shape. An intersection B between the straight line L and the point where the straight line L becomes the longest among the pixel data constituting the tire contact surface 11 is calculated. Next, a straight line L is drawn so that the sample angle θ is 2 °, that is, the sample angle θ is 1 degree, and the intersection point B with the pixel data constituting the tire contact surface 11 where the straight line L is longest is calculated. That is, the straight line L is extended toward the outside of the tire ground contact surface 11 with respect to each sample angle θ, and the intersection point with the point where the straight line L is the longest among the pixel data constituting the tire ground contact surface 11 is calculated. Repeat until L makes one revolution around center point A.

Here, depending on the sample angle θ, the intersection B may be an intersection between the straight line L and the groove wall surface C of a groove in the tire contact surface 11 of the tire contact data 10 (for example, a circumferential groove continuous in the tire circumferential direction). is there. In this case, the groove wall surface C may be handled as the intersection B. Further, the length of the straight line L _n from the center point A in a sample angle theta _n to an intersection between the straight line L _n and the groove wall surface from C, the center point A at the previous sample angle theta _n-1 sample angle theta _n the length of the straight line L _n-1 to an intersection B _n-1 and may be determined by comparing the. Specifically, a certain threshold length of the straight line L _n at sample angles theta _n, for example, if the sample angle theta _n-1 does not exceed 80% of the length of the straight line L _n-1, the sample angle theta replacing the length of the straight line L _n on the length of the straight line L _n-1 in the sample angle theta _n-1 in _n. Thereby, the precision of a tire ground contact characteristic can be improved. Further, when the arbitrary coordinates are within the circumferential groove of the tire ground contact surface 11 having the tire ground contact shape, the straight line L may extend from the arbitrary coordinates toward the outside of the tire ground contact surface 11 in the tire circumferential direction (for example, If the sample angle θ is 90 ° or 270 °), the intersection point B with the contour line of the tire contact surface 11 cannot be obtained. In this case, similarly to the above, replaces the length of the straight line L _n at sample angles theta _n linear L _n-1 in the sample angle theta _n-1 in length.

  Then, when the XY coordinates of the intersection point B with respect to each sample angle θ are displayed on the polar coordinates, as shown in FIG. 6A, the contour line 20 of the tire contact surface 11 having a tire contact shape is obtained. That is, the contour line 20 of the tire ground contact surface 11 constituted by the intersection point B is obtained. The obtained contour line 20 of the tire contact surface 11 can be converted into a contact contour waveform 30 of the length of the straight line L and the sample angle θ shown in FIG. Here, ai shown in FIG. 6A correspond to ai shown in FIG. The locations b, d, f, and h where the contour line 20 of the obtained tire ground contact shape shown in FIG. 6A changes greatly become the peak of the ground contact contour waveform 30 shown in FIG. Therefore, in order to approximate the contact shape function 40 obtained from the contact contour waveform 31 described later with the tire contact shape of the acquired tire contact image data 10, the obtained contour line 20 of the tire contact shape greatly changes. It is preferable to make the sample angle θ of the portion fine. That is, the sample angles θ are not limited to the above-mentioned equal intervals, and are preferably set at unequal intervals.

  Next, the obtained contour line 20 of the tire ground contact surface 11 which is a tire ground contact shape is averaged (step ST4). Specifically, first, as illustrated in FIG. 7A, the processing unit 3b rotates the contour line 20 obtained from the center point A (dotted line in FIG. 7A) symmetrically, for example, by 180 °. Next, an average value of the contour line rotated symmetrically from a center point A (not shown) overlapping the contour line 20 is obtained. And the contour line 21 (solid line in FIG. 7-1) of the tire contact surface 11 which is the tire contact shape averaged from this average value is calculated | required. That is, the front / rear, left / right or front / rear / left / right of the tire contact surface 11 of the tire contact image data 10 having variations is averaged. As a result, the calculated contour line 20 of the tire ground contact surface 11 that is the tire ground contact shape becomes the contour line 21 in which any one of front and rear, left and right, front and rear, and right and left is averaged. The accuracy of the tire ground contact characteristic calculated from 40 can be achieved. Note that the averaged contour line 21 is not limited to being obtained from an average value of a contour line rotated symmetrically from a center point A (not shown) that overlaps the contour line 20, and a center (not shown) that overlaps the contour line 20. You may obtain | require from the outermost value and innermost value of the outline rotated point-symmetrically from the point A. In step ST4, the obtained contour line 20 is averaged with point symmetry. However, the present invention is not limited to this, and the line is symmetrical with respect to the center point A (for example, a line parallel to the X axis, Y It may be averaged by folding back (symmetric to a line parallel to the axis).

  Next, a ground shape contour waveform 31 is created from the sample angle θ and the straight line L (step ST5). First, the processing unit 3b determines the length of the straight line L for each sample angle θ with respect to the obtained contour line 21 of the tire contact surface 11 having the averaged tire contact shape shown in FIG. The length to the intersection (not shown) with the contour line 21 of the tire contact surface 11 that is an averaged tire contact shape is obtained. Next, a ground shape contour waveform 31 (solid line) is created in which the horizontal axis shown in FIG. 7-2 is the sample angle θ and the vertical axis is the amplitude (straight line L). Reference numeral 30 denotes a ground shape contour line waveform (dotted line) with respect to the contour line 20 of the tire ground contact surface 11 before being averaged.

  Next, a ground contact shape function 40 is obtained from the tire ground contact contour 21 (contact shape contour waveform 31) (step ST6). That is, the contact shape function 40 is obtained from the contour line 21 obtained by averaging the tire contact shape from the sample angle θ and the length of the straight line L from the center point A which is an arbitrary coordinate to the intersection B. Here, a case will be described in which a Fourier series is used as a function that approximates a contour line of a tire contact surface that is a tire contact shape. By using the Fourier series, it is possible to improve the approximation performance of the contact shape function 40 with respect to the contour line of the tire contact shape. Therefore, the accuracy when calculating the tire contact characteristics from the obtained contact shape function 40 is improved. A polynomial may be used as a function that approximates the tire contact shape (the contour line of the tire contact surface 11). By using the polynomial, the calculation time of the ground contact shape function 40 for the contour line of the tire ground contact shape can be shortened, and the calculation amount can be reduced.

  First, a Fourier series that approximates the ground shape contour waveform 31 created from the sample angle θ and the straight line L is obtained. In this case, the processing unit 3b sequentially obtains a function whose order is increased from a low-order Fourier series, for example, 0th order, to a higher-order polynomial, for example, an Nth-order expression. Here, since the contour line 20 is averaged point-symmetrically, as shown in FIG. 7B, the contour line 21 has the same or substantially the same shape of 0 ° to 180 ° and 180 ° to 360 ° in the polar coordinate system. In other words, the same array has a continuous shape twice. Therefore, as shown in FIG. 8, the even-order component is emphasized, and the influence of the odd-order component is reduced. FIG. 8 shows the influence of each order component. In FIG. 8, since there are many quaternary components, it can be seen that the outline 21 has a shape close to a quadrangle. Next, the Fourier series of the order that approximates the ground shape contour line waveform 31 is determined from the sequentially obtained Fourier series of each order, and this is used as the ground shape function 40. As shown in FIG. 9, for example, when the ground shape contour waveform 31 (one-dot chain line) is approximated by a 20th-order Fourier series, a ground shape function waveform 32 (solid line) is obtained. Further, when this contact shape function waveform 32 is converted into polar coordinates in the same manner as the averaged contour line 21 of the tire contact surface 11 having the tire contact shape, it is as shown in FIG. Thereby, the contact shape function 40 which is a Fourier series approximate to the contour line of the tire contact surface 11 is obtained.

Here, when determining the order Fourier series that approximates the ground shape contour waveform 31 from the sequentially obtained Fourier series of each order, it is preferable to perform the following procedure. FIG. 11 is a diagram illustrating the relationship between the correlation coefficient R ² and the order of the contact shape function. FIGS. 12-1 to 8 are diagrams illustrating the relationship between the contour line of the tire contact shape and the contact shape function. First, each XY of the point which comprises the calculated | required outline 21 of the tire ground contact surface 11 which is a tire ground contact shape, ie, the straight line L for every sample angle (theta), and the contour line of the tire ground contact surface 11 which is a tire ground contact shape. A ground shape function of a Fourier series of order N in which the square value R ² of the correlation coefficient between the coordinates and the Fourier series solution that is a ground shape function corresponding to each XY coordinate is 0.9 or more is determined. This is to prevent a decrease in accuracy when the tire ground contact characteristic is calculated from the obtained ground contact shape function. For example, the ground contact shape function 40a~c Fourier series from quartic shown in FIG 12-1～3 to 8 polynomials, square value R ² of the correlation coefficient is not greater than 0.9. On the other hand, in the 10th to 18th order Fourier series ground shape functions 40d to h shown in FIGS. 12-4 to 8, the square value R ² of the correlation coefficient is 0.9 or more. Therefore, any ground contact shape function 40d of a Fourier series of 10th order or higher can be a ground contact shape function that approximates the averaged contour line 21 of the tire ground contact surface 11. However, the higher the order, the more complicated the equation becomes, and the amount of tire ground contact shape data increases. In order to prevent this increase in the amount of data, the tire contact surface 11 is averaged by a Fourier series contact shape function from the Nth order to the N + 2nd order when the square value R ² of the correlation coefficient is 0.9 or more. It is preferable to approximate the contour line 21. Accordingly, for example, the ground shape functions 40d and 40e of the Fourier series of the 10th to 12th equations shown in FIGS.

  Next, the ground contact shape function 40 is converted into data as the tire ground contact shape (step ST7). That is, the processing unit 3b captures an image input to the tire ground contact image analysis device 3 by the ground contact shape function 40 that approximates the contour line of the tire ground contact surface 11 that is a tire ground contact shape and the input unit 4a of the input / output device 4. Other data such as the type of the tire 1 imaged by the device 2 or the like and the contact condition of the tire 1 are used as one tire contact shape data. The tire ground contact shape data can be displayed by the display means 4b of the input / output device 4 as shown in FIG. Then, the processing unit 3b stores the tire ground contact shape data in the storage unit 3a, that is, creates a database (step ST8). The tire ground contact shape data is stored not by the storage unit 3a of the tire ground contact image analysis device 3, but by a database server connected to another tire ground contact image analysis device 3 via a network such as the Internet or an intranet. It may be stored in

  The processing unit 3b may calculate tire contact characteristics based on the tire contact shape data (step ST9). That is, from the contact shape function 40, the contact area of the tire contact characteristics, the average pressure based on the load load and the contact area, the maximum contact length in the tire circumferential direction (contact length direction), the tire width direction (contact width direction) The maximum ground contact width may be calculated. These tire ground contact characteristics can be displayed by the display means 4b of the input / output device 4. Further, these tire contact characteristics may be included in the tire contact shape data and stored in the storage unit 3a, that is, formed into a database (step ST8).

  Furthermore, the processing unit 3b may use the tire ground contact shape data for simulation (step ST10). That is, a model of the contact surface of the tire 1 may be created from the tire contact shape data, and the performance evaluation of the tire 1, for example, noise performance, friction performance, steering stability performance, braking performance, and the like may be performed. In this case, since the tire contact shape data is the combined contact shape function 60, it is possible to easily create a model of the contact surface of the tire 1, and the calculation time and amount of calculation of the tire contact image analysis device 3 that performs the simulation. Can be reduced. In addition, when the processing capability of the processing unit 3b of the tire contact image analysis device 3 is low, the simulation is performed by inputting the tire contact shape data into a dedicated simulation device having a high processing capability for performing another simulation. May be.

  As described above, it is not necessary to obtain the pixel image of the tire contact shape by repeatedly expanding and contracting from the tire contact image data 10 as in the conventional case, and the calculation time and the calculation amount for obtaining the tire contact shape are reduced. be able to. Thus, the tire ground contact image analysis can be performed even with a PC or the like that has a relatively low processing speed. Further, since the tire ground contact shape obtained in the conventional manner is not a pixel image but a ground contact shape function 40, the data amount of the tire ground contact shape can be reduced. Thereby, it becomes easy to store the obtained tire ground contact shape as data, that is, to create a database.

  Further, since the arbitrary coordinate is the center point A on the tire contact surface 11 having the tire contact shape, the length of the straight line L from the center point A to the intersection B obtained for each sample angle θ is stable, that is, changes extremely. Therefore, the contour line 20 of the tire ground contact surface 11 having the tire ground contact shape can be approximated by a Fourier series contact shape function having a low order. Accordingly, it is possible to further reduce the calculation time and the calculation amount for obtaining the ground contact shape function 40. In addition, since the contact shape function can be approximated by a low-order contact shape function, the data amount of the tire contact shape can be further reduced as compared with a complex contact shape function having a high order.

  In the best mode for carrying out the invention, the case where the contact shape function 40 is obtained from the tire contact image data 10 at a predetermined position on the tread surface 1a of the tire 1 has been described. However, the present invention is not limited to this. is not. For example, one contact shape function 40 may be obtained from the tire contact image data 10 at a plurality of locations on the tread surface 1a of the tire 1 as the tire contact shape. In this case, first, the tire ground contact image analyzing device 3 acquires a plurality of tire ground contact image data 10 captured at the image capturing device 2 or other places. Next, the contour line 20 of the tire contact surface 11 in each tire contact image data 10 is obtained from the sample angle θ and the straight line L. Next, the obtained plurality of contour lines 20 are overlapped in the same polar coordinate system and averaged, that is, the average value, outermost value, and innermost value of the overlapping contour lines are obtained. A ground contact shape function is obtained from the averaged contour line by the method described above.

  Here, a comparison was made between the contact shape function 40 obtained from the tire contact image data 10 and the tire contact image data 10 by the tire contact image analysis method. 13 to 16 are diagrams showing a comparison between the contact shape function and the tire contact image data. FIG. 13 shows a tire contact surface 11-1 of tire contact image data with a tire internal pressure of 230 kPa and a load of 4.6 kN when a radial tire for a passenger car having a tire size of 205 / 65R15 94S is mounted on a rim (not shown). Is the ground state function 40-1. FIG. 14 shows from the tire contact surface 11-2 of the tire contact image data with a tire internal pressure of 190 kPa and a load of 4.6 kN in a state where a radial tire for a passenger car having a size of 205 / 65R15 94H is mounted on a rim (not shown). The ground state function 40-2 is obtained. FIG. 15 shows a tire ground contact image data 11-3 with a tire internal pressure of 210 kPa and a load of 3.5 kN in a state where a radial tire for a passenger car having a size of 175 / 70R15 84S is mounted on a rim (not shown). The ground state function 40-3 is obtained. FIG. 16 shows from the tire contact surface 11-4 of the tire contact image data with a tire internal pressure of 900 kPa and a load of 24.52 kN in a state where a radial tire for a truck having a size of 11R22.5 14P is mounted on a rim (not shown). The ground state function 40-4 is obtained.

  In any case, it can be seen that the contact shape functions 40-1 to 40-4 approximate the contour lines (not shown) of the tire contact surfaces 11-1 to 4 which are the tire contact shapes of the tire contact image data, respectively. Accordingly, tire contact characteristics (contact area, average pressure, maximum contact length, maximum contact width, etc.) can be accurately calculated from the contact shape functions 40-1 to 40-4. Moreover, the reliability of evaluation of tire performance evaluation (noise performance, friction performance, steering stability performance, braking performance, etc.) can be improved by using the contact shape functions 40-1 to 4 for simulation.

It is a figure which shows the structural example of the tire contact image analysis apparatus which performs the tire contact image analysis method concerning this invention. It is a figure which shows the flowchart of the tire contact image analysis method concerning this invention. It is explanatory drawing for calculating | requiring the intersection of the outline of a tire ground-contact shape, and a straight line. It is explanatory drawing for calculating | requiring the intersection of the outline of a tire ground-contact shape, and a straight line. It is explanatory drawing for calculating | requiring the intersection of the outline of a tire ground-contact shape, and a straight line. It is a figure which shows the outline of a tire ground contact shape. It is a figure which shows the relationship between an amplitude (straight line L) and a sample angle. It is a figure which shows the outline of the tire contact shape after averaging. It is a figure which shows the relationship between the amplitude (straight line L) after averaging, and a sample angle. It is explanatory drawing for calculating | requiring a ground-contact shape function. It is explanatory drawing for calculating | requiring a ground-contact shape function. It is a figure which shows the contact shape function calculated | required by the tire contact image analysis method concerning this invention. Is a diagram showing the relationship between the correlation coefficient R ² the order of the ground contact shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the relationship between the outline of a tire grounding shape, and a grounding shape function. It is a figure which shows the comparison with a contact shape function and tire contact image data. It is a figure which shows the comparison with a contact shape function and tire contact image data. It is a figure which shows the comparison with a contact shape function and tire contact image data. It is a figure which shows the comparison with a contact shape function and tire contact image data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Imaging device 3 Tire contact image analyzer 4 Input / output device 10 Tire contact image data 20 Contour line 30 Ground shape contour waveform 32 Ground shape function waveform 40 Ground shape function A Center point B Intersection L Line θ Sample angle

Claims (7)

The procedure to acquire tire ground contact image data,
A procedure for determining arbitrary coordinates in the tire contact shape from the acquired tire contact image data,
A procedure for obtaining an intersection of a straight line extending from the arbitrary coordinates for each sample angle and the contour line of the tire ground contact shape;
A procedure for approximating the contour line of the tire ground contact shape with a function from the sample angle and the length of a straight line from the arbitrary coordinate to the obtained intersection, and obtaining a contact shape function;
A tire ground contact image analysis method comprising:   The tire contact image analysis method according to claim 1, wherein the arbitrary coordinate in the tire contact shape is a center point in the tire contact shape.   The tire contact shape contour line is an average value, outermost value of the tire contact shape contour line that overlaps when the tire contact shape is line-symmetrically folded from the center point or rotated point-symmetrically from the center point. The tire ground contact image analysis method according to claim 1, wherein the tire ground contact image analysis method is an innermost value.   The tire contact image analysis method according to claim 1, wherein the contact shape function is a Fourier series or a polynomial. The obtained contact shape function sequentially increases the order of the contact shape function, and the first contact where the correlation coefficient R ² between the contact shape function and the tire contact shape in which the order sequentially increases becomes 0.9 or more. The tire ground contact image analysis method according to any one of claims 1 to 4, wherein when the order of the shape function is N, the order is a ground contact shape function of N to N + 2. Processing means for processing each procedure in the tire ground contact image analysis method according to any one of claims 1 to 5,
Input means for giving the tire contact image data and other data to the processing means;
Display means for displaying the contact shape function and tire contact image analysis result by the processing means;
A tire ground contact image analyzing apparatus comprising:   A tire ground contact image analysis program which causes a computer to execute the tire ground contact image analysis method according to any one of claims 1 to 5.

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